INVESTIGATING THE ACTIVITY OF ZIRCONIA AS A CATALYST …

INVESTIGATING THE ACTIVITY OF ZIRCONIA AS A

CATALYST AND AS A SUPPORT FOR NOBLE METALS IN

ORGANIC OXIDATION REACTIONS

Presented by

MOHAMMAD SADIQ

NATIONAL CENTRE OF EXCELLENCE IN PHYSICAL

CHEMISTRY UNIVERSITY OF PESHAWAR

2009


CATALYST AND AS A SUPPORT FOR NOBLE METALS

IN ORGANIC OXIDATION REACTIONS

A dissertation submitted to the University of Peshawar in partial

fulfillment for the degree of

DOCTOR OF PHILOSOPHY IN PHYSICAL CHEMISTRY

Presented by

MOHAMMAD SADIQ



2009

i

ii

Acknowledgment

I would like to express my thanks to all those who have supported me and encouraged

me to pursue the study of Physical Chemistry particularly during my doctoral studies

First I would like to thank my supervisor Prof Dr Mohammad Ilyas for giving me the

opportunity to complete doctoral studies in his laboratory under his kind supervision

During the last three years he fulfilled all of my wishes with regard to giving me

scientific freedom broadening the research topic providing instrumentation and

interesting courses The atmosphere in his laboratory was pleasant and stress-free I am

grateful to him for the very fast review of my work his helpful remarks his generosity

and his confidence in me

I wish to thank Prof Dr Syed Mustafa Director NCE in Physical chemistry

University of Peshawar for providing me all the available facilities during the study

I would like to acknowledge the work and support from the glassblowing staff

who have made every possible effort to designed and constructed different Pyrex glass

reactors for experimental setup

Further I appreciate the staff of Centralized Resources Laboratory at Physics

Department and NCE in Geology for helping me in characterization of the catalysts

I am thankful from the core of my heart to my junior brother Mohammad Ali for

his support through out my study I also say a big ldquothank yourdquo to Saima my cute wife for

all her care her understanding her love and spiritual support

During the last three years of my PhD study I have met many nice colleagues

most of them deserve to be thanked for some reasons Heartfelt thanks to my Lab fellows

Mr Mohammad Taufiq Mr Imdad Khan Mr Mohammad Saeed Rahmat Ali and

Mohammad Hamayun for their sincere cooperation and friendly behavior throughout the

time I spent with them

And at last

Dear family members thank you very much for standing with me through thick and thin

Mr Mohammad Sadiq

iii

Abstract

Alcohols and cyclic alkanes oxidation in an environment friendly protocol was carried

out in a typical batch reactor These reactions were carried out in solvent free conditions

andor in eco-friendly solvents using molecular oxygen as the only oxidant and ZrO2

andor ZrO2 supported noble metals (Pt Pd) as catalysts The influence of different

reaction parameters (speed of agitation reaction time and temperature) catalyst

parameters (calcination temperature and loading) and oxygen partial pressure on the

catalyst performance was studied Different modern techniques such as (FT-IR XRD

SEM EDX surface and pores size analyzer and particle size analyzer) were used for the

characterization of catalyst ZrO2 calcined at 1223 K was found to be more active as a

single catalyst than the one calcined at 723 K for alcohol oxidation to the corresponding

carbonyl products under solvent free conditions and in ecofriendly solvent as well

Platinum supported on zirconia was highly active and selective for oxidation of benzyl

alcohol to benzaldehyde in n- heptane and toluene to benzoic acid in both solvent free

conditions and in aqueous medium Similarly zirconia supported Pt or Pd catalysts were

tested for cyclohexane oxidation in solvent free conditions and for phenol oxidation in

aqueous medium Both catalysts have shown magnificent catalytic activity Bismuth was

added as a promoter to these catalysts Bismuth promoted PtZrO2 has shown outstanding

catalytic performance These catalysts are insoluble in the reaction mixture and can be

easily separated by simple filtration and reused Typical batch reactorrsquos kinetic data were

obtained and fitted to the classical LangmuirndashHinshelwood Marsndashvan Krevelen and as

well as to the Eley-Rideal model of heterogeneously catalyzed reactions In alcohol

oxidation reactions the Langmuir-Hinshelwood model was found to give a better fit The

rate-determining step was proposed to involve direct interaction of an adsorbed oxidizing

species with the adsorbed reactant or an intermediate product of the reactant While in

toluene oxidation the Eley-Rideal model was found to give a better fit Eley-Rideal

mechanism envisages reaction between adsorbed oxygen with hydrocarbon molecules

from the fluid phase The calculated apparent activation energy and agitation effect have

shown the absence of mass transfer effect

Keywords Catalysis solvent free eco-friendly solvents organic oxidation reactions mild conditions

iv

List of Publications

Thesis includes the following papers which were published in different international

journals and presented at various conferences

I Ilyas M Sadiq M Imdad K Chin J Catal 2007 28 413

II Ilyas M Sadiq M Chem Eng Technol 2007 30 1391-1397

III Ilyas M Sadiq M Chin J Chem 2008 26 146

IV Ilyas M Sadiq M Catal Lett 2009 128 337

V Ilyas M Sadiq M ldquoInvestigating the activity of zirconia as a catalyst

and a support for noble metals in green oxidation of cyclohexanerdquo J

Iran Chem Soc Submitted

VI M Ilyas M Sadiq ldquoA model catalyst for aerobic oxidation of toluene in

aqueous solutionrdquo presented in 12th International Conference of the

Pacific Basin Consortium for Environment amp Health Sciences at Beijing

University China 26-29 October 2007 (Submitted to Catalysis Letter)

VII M Ilyas M Sadiq ldquoOxidation of benzyl alcohol in aqueous medium by

zirconia catalyst at mild conditionsrdquo presented in 18th National Chemistry

Conference in Institute of Chemistry University of Punjab Lahore

Pakistan 25-27 February 2008

VIII M Ilyas M Sadiq ldquoComparative study of commercially available ZrO2

and laboratory prepared ZrO2 for liquid phase solvent free oxidation of

cyclohexanolrdquo presented in 18th National Chemistry Conference Institute

of Chemistry University of Punjab Lahore Pakistan 25-27 February

2008

IX M Ilyas M Sadiq ldquoZirconia-supported noble metals catalyst for

oxidation of phenol in artificially contaminated water at milder

conditionsrdquo presented in 1st National Symposium on Analytical

Environmental and Applied Chemistry in Shah Abdul Latif University

Khairpur Sindh Pakistan 24-25 October 2008

v

TABLE OF CONTENTS

CHAPTER No PARTICULARS PAGE No

Acknowledgment ii

Abstract iii

List of Publications iv

Chapter 1 Introduction

11 Aims and objective 01

12 Zirconia in Catalysis 02

13 Oxidation of alcohols 03

14 Oxidation of toluene 06

15 Oxidation of cyclohexane 09

16 Oxidation of phenol 09

17 Characterization of catalyst 11

171 Surface area Measurements 11

172 Particle size measurement 11

173 X-ray differactometry 12

174 Infrared Spectroscopy 12

175 Scanning Electron Microscopy 13

Chapter 2 Literature review 14

References 20

vi

TABLE OF CONTENTS


Chapter 3 Experimental

31 Material 30

32 Preparation of catalyst 30

321 Laboratory prepared ZrO2 30

322 Optimal conditions 32

323 Commercial ZrO2 32

324 Supported catalyst 32

33 Characterization of catalysts 32

34 Experimental setups for different reaction 33

35 Liquid-phase oxidation in solvent free conditions 37

351 Design of reactor for liquid phase oxidation in

solvent free condition 37

36 Liquid-phase oxidation in eco-friendly solvents 38


eco-friendly solvents 38

37 Analysis of reaction mixture 39

38 Heterogeneous nature of the catalyst 41

References 42

vii

TABLE OF CONTENTS


Chapter 4A Results and discussion

Oxidation of alcohols in solvent free

conditions by zirconia catalyst 43

4A 1 Characterization of catalyst 43

4A 2 Brunauer-Emmet-Teller method (BET) 43

4A 3 X-ray diffraction (XRD) 43

4A 4 Scanning electron microscopy 43

4A 5 Effect of mass transfer 45

4A 6 Effect of calcination temperature 46

4A 7 Effect of reaction time 46

4A 8 Effect of oxygen partial pressure 48

4A 9 Kinetic analysis 48

426 Mechanism of reaction 49

427 Role of oxygen 52

References 54

Chapter 4B Results and discussion

Oxidation of alcohols in aqueous medium by

zirconia catalyst 56

4B 1 Characterization of catalyst 56

4B 2 Oxidation of benzyl alcohols in Aqueous Medium 56

4B 3 Effect of Different Parameters 59

References 62

viii

TABLE OF CONTENTS


Chapter 4C Results and discussion

Oxidation of toluene in solvent free

conditions by PtZrO2 63

4C 1 Catalyst characterization 63

4C 2 Catalytic activity 63

4C 3 Time profile study 65

4C 4 Effect of oxygen flow rate 67

4C 5 Appearance of trans-stilbene and

methyl biphenyl carboxylic acid 67

References 70

Chapter 4D Results and discussion

Oxidation of benzyl alcohol by zirconia supported

platinum catalyst 71

4D1 Characterization catalyst 71

4D2 Oxidation of benzyl alcohol 71

4D21 Leaching of the catalyst 72

4D22 Effect of Mass Transfer 74

4D23 Temperature Effect 74

4D24 Solvent Effect 74

4D25 Time course of the reaction 75

4D26 Reaction Kinetics Analysis 75

4D27 Effect of Oxygen Partial Pressure 80

4D 28 Mechanistic proposal 83

References 84

ix

TABLE OF CONTENTS


Chapter 4E Results and discussion

Oxidation of toluene in aqueous medium

by PtZrO2 86

4E 1 Characterization of catalyst 86

4E 2 Effect of substrate concentration 86

4E 3 Effect of temperature 88

4E 4 Agitation effect 88

4E 5 Effect of catalyst loading 88

4E 6 Time profile study 90

4E 7 Effect of oxygen partial pressure 90

4E 8 Reaction kinetics analysis 90

4E 9 Comparison of different catalysts 94

References 95

Chapter 4F Results and discussion

Oxidation of cyclohexane in solvent free

by zirconia supported noble metals 96

4F1 Characterization of catalyst 96

4F2 Oxidation of cyclohexane 98

4F3 Optimal conditions for better catalytic activity 100

References 102

Chapter 4G Results and discussion

Oxidation of phenol in aqueous medium

by zirconia-supported noble metals 103

4G1 Characterization of catalyst 103

4G2 Catalytic oxidation of phenol 108

x

TABLE OF CONTENTS


4G3 Effect of different parameters 108

4G4 Time profile study 108

4G5 Comparison of different catalysts 108

4G6 Effect of Pd and Pt loading on catalytic activity 110

4G 7 Effect of bismuth addition on catalytic activity 110

4G 8 Influence of reduction on catalytic activity 110

4G 9 Effect of temperature 110

References 112

Chapter 5 Concluding review 113

1

Chapter 1

Introduction

Oxidation of organic compounds is well established reaction for the synthesis of

fine chemicals on industrial scale [1 2] Different reagents and methods are used in

laboratory as well as in industries for organic oxidation reactions Commonly oxidation

reactions are performed with stoichiometric amounts of oxidants such as peroxides or

high oxidation state metal oxides Most of them share common disadvantages such as

expensive and toxic oxidants [3] On industrial scale the use of stoichiometric oxidants

is not a striking choice For these kinds of reactions an alternative and environmentally

benign oxidant is welcome For industrial scale oxidation molecular oxygen is an ideal

oxidant because it is easily accessible cheap and non-toxic [4] Currently molecular

oxygen is used in several large-scale oxidation reactions catalyzed by inorganic

heterogeneous catalysts carried out at high temperatures and pressures often in the gas

phase [5] The most promising solution to replace these toxic oxidants and harsh

conditions of temperature and pressure is supported noble metals catalysts which are

able to catalyze selective oxidation reactions under mild conditions by using molecular

oxygen The aim of this work was to investigate the activity of zirconia as a catalyst and a

support for noble metals in organic oxidation reactions at milder conditions of

temperature and pressure using molecular oxygen as oxidizing agent in solvent free

condition andor using ecofriendly solvents like water

11 Aims and objectives

The present-day research requirements put pressure on the chemist to divert their

research in a way that preserves the environment and to develop procedures that are

acceptable both economically and environmentally Therefore keeping in mind the above

requirements the present study is launched to achieve the following aims and objectives

i To search a catalyst that could work under mild conditions for the oxidation of

alkanes and alcohols

2

ii Free of solvents system is an ideal system therefore to develop a reaction

system that could be run without using a solvent in the liquid phase

iii To develop a reaction system according to the principles of green chemistry

using environment acceptable solvents like water

iv A reaction that uses many raw materials especially expensive materials is

economically unfavorable therefore this study reduces the use of raw

materials for this reaction system

v A reaction system with more undesirable side products especially

environmentally hazard products is rather unacceptable in the modern

research Therefore it is aimed to develop a reaction system that produces less

undesirable side product in low amounts that could not damage the

environment

vi This study is aimed to run a reaction system that would use simple process of

separation to recover the reaction materials easily

vii In this study solid ZrO2 and or ZrO2 supported noble metals are used as a

catalyst with the aim to recover the catalyst by simple filtration and to reuse

the catalyst for a longer time

viii To minimize the cost of the reaction it is aimed to carry out the reaction at

lower temperature

To sum up major objectives of the present study is to simplify the reaction with the

aim to minimize the pollution effect to gather with reduction in energy and raw materials

to economize the system

12 Zirconia in catalysis

Over the years zirconia has been largely used as a catalytic material because of

its unique chemical and physical characteristics such as thermal stability mechanical

stability excellent chemical resistance acidic basic reducing and oxidizing surface

properties polymorphism and different precursors Zirconia is increasingly used in

catalysis as both a catalyst and a catalyst support [6] A particular benefit of using

zirconia as a catalyst or as a support over other well-established supportscatalyst systems

is its enhanced thermal and chemical stability However one drawback in the use of

3

zirconia is its rather low surface area Alumina supports with surface area of ~200 m2g

are produced commercially whereas less than 50 m2g are reported for most available

zirconia But it is known that activity and surface area of the zirconia catalysts

significantly depends on precursorrsquos material and preparation procedure therefore

extensive research efforts have been made to produce zirconia with high surface area

using novel preparation methods or by incorporation of other components [7-14]

However for many catalytic purposes the incorporation of some of these oxides or

dopants may not be desired as they may lead to side reactions or reduced activity

The value of zirconia in catalysis is being increasingly recognized and this work

focuses on a number of applications where zirconia (as a catalyst and a support) gaining

academic and commercial acceptance

13 Oxidation of alcohols

Oxidation of organic substrates leads to the production of many functionalized

molecules that are of great commercial and synthetic importance In this regard selective

oxidation of alcohols to carbonyl compounds is a fundamental transformation in organic

chemistry as carbonyl compounds are widely used as intermediates for fine chemicals

[15-17] The traditional inorganic oxidants such as permanganate and dichromate

however are toxic and produce a large amount of waste The separation and disposal of

this waste increases steps in chemical processes Therefore from both economic and

environmental viewpoints there is an urgent need for greener and more efficient methods

that replace these toxic oxidants with clean oxidants such as O2 and H2O2 and a

(preferably separable and reusable) catalyst Many researchers have reported the use of

molecular oxygen as an oxidant for alcohol oxidation using different catalysts [17-28]

and a variety of solvents

The oxidation of alcohols can be carried out in the following three conditions

i Alcohol oxidation in solvent free conditions

ii Alcohol oxidation in organic solvents

iii Alcohol oxidation in water

4

To make the liquid-phase oxidation of alcohols more selective toward carbonyl

products it should be carried out in the absence of any solvent There are a few methods

reported in the published reports for solvent free oxidation of alcohols using O2 as the

only oxidant [29-32] Choudhary et al [32] reported the use of a supported nano-size gold

catalyst (3ndash8) for the liquid-phase solvent free oxidation of benzyl alcohol with

molecular oxygen (152 kPa) at 413 K U3O8 MgO Al2O3 and ZrO2 were found to be

better support materials than a range of other metal oxides including ZnO CuO Fe2O3

and NiO Benzyl alcohol was oxidized selectively to benzaldehyde with high yield and a

relatively small amount of benzyl benzoate as a co-product In a recent study of benzyl

alcohol oxidation catalyzed by AuU3O8 [30] it was found that the catalyst containing

higher gold concentration and smaller gold particle size showed better process

performance with respect to conversion and selectivity for benzaldehyde The increase in

temperature and reaction duration resulted in higher conversion of alcohol with a slightly

reduced selectivity for benzaldehyde Enache and Li et al [31 32] also reported the

solvent free oxidation of benzyl alcohol to benzaldehyde by O2 with supported Au and

Au-Pd catalysts TiO2 [31] and zeolites [32] were used as support materials The

supported Au-Pd catalyst was found to be an effective catalyst for the solvent free

oxidation of alcohols including benzyl alcohol and 1-octanol The catalysts used in the

above-mentioned studies are more expensive Furthermore these reactions are mostly

carried out at high pressure Replacement of these expensive catalysts with a cheaper

catalyst for alcohol oxidation at ambient pressure is desirable In this regard the focus is

on the use of ZrO2 as the catalyst and catalyst support for alcohol oxidation in the liquid

phase using molecular oxygen as an oxidant at ambient pressure ZrO2 is used as both the

catalyst and catalyst support for a large variety of reactions including the gas-phase

cyclohexanol oxidationdehydrogenation in our laboratory and elsewhere [33- 35]

Different types of solvent can be used for oxidation of alcohols Water is the most

preferred solvent [17- 22] However to avoid over-oxidation of aldehydes to the

corresponding carboxylic acids dry conditions are required which can be achieved in the

presence of organic solvents at a relatively high temperature [15] Among the organic

solvents toluene is more frequently used in alcohol oxidation [15- 23] The present work

is concerned with the selective catalytic oxidation of benzyl alcohol (BzOH) to

5

benzaldehyde (BzH) Conversion of benzyl alcohol to benzaldehyde is used as a model

reaction for oxidation of aromatic alcohols [23 24] Furthermore benzaldehyde by itself

is an important chemical due to its usage as a raw material for a large number of products

in organic synthesis including perfumery beverage and pharmaceutical industries

However there is a report that manganese oxide can catalyze the conversion of toluene to

benzoic acid benzaldehyde benzyl alcohol and benzyl benzoate [36] in solvent free

conditions We have also observed conversion of toluene to benzaldehyde in the presence

of molecular oxygen using Nickel Oxide as catalyst at 90 ˚C Therefore the use of

toluene as a solvent for benzyl alcohol oxidation could be considered as inappropriate

Another solvent having boiling point (98 ˚C) in the same range as toluene (110 ˚C) is n-

heptane Heynes and Blazejewicz [37 38] have reported 78 yield of benzaldehyde in

one hour when pure PtO2 was used as catalyst for benzyl alcohol oxidation using n-

heptane as solvent at 60 ˚C in the presence of molecular oxygen They obtained benzoic

acid (97 yield 10 hours) when PtC was used as catalyst in reflux conditions with the

same solvent In the present work we have reinvestigated the use of n-heptane as solvent

using zirconia supported platinum catalysts in the presence of molecular oxygen

In relation to strict environment legislation the complete degradation of alcohols

or conversion of alcohols to nontoxic compound in industrial wastewater becomes a

debatable issue Diverse industrial effluents contained benzyl alcohol in wide

concentration ranges from (05 to 10 g dmminus3) [39] The presence of benzyl alcohol in

these effluents is challenging the traditional treatments including physical separation

incineration or biological abatement In this framework catalytic oxidation or catalytic

oxidation couple with a biological or physical-chemical treatment offers a good

opportunity to prevent and remedy pollution problems due to the discharge of industrial

wastewater The degradation of organic pollutants aldehydes phenols and alcohols has

attracted considerable attention due to their high toxicity [40- 42]

To overcome environmental restrictions researchers switch to newer methods for

wastewater treatment such as advance oxidation processes [43] and catalytic oxidation

[39- 42] AOPs suffer from the use of expensive oxidants (O3 or H2O2) and the source of

energy On other hand catalytic oxidation yielded satisfactory results in laboratory studies

[44- 50] The lack of stable catalysts has prevented catalytic oxidation from being widely

6

employed as industrial wastewater treatment The most prominent supported catalysts

prone to metal leaching in the hot acidic reaction environment are Cu based metal oxides

[51- 55] and mixed metal oxides (CuO ZnO CoO) [56 57] Supported noble metal

catalyst which appear much more stable although leaching was occasionally observed

eg during the catalytic oxidation of pulp mill effluents over Pd and Pt supported

catalysts [58 59] Another well-known drawback of catalytic oxidation is deactivation of

catalyst due to formation and strong adsorption of carbonaceous deposits on catalytic

surface [60- 62] During the recent decade considerable efforts were focused on

developing stable supported catalysts with high activity toward organic pollutants [63-

76] Unfortunately these catalysts are expensive Search for cheap and stable catalyst for

oxidation of organic contaminants continues Many groups have reviewed the potential

applications of ZrO2 in organic transformations [77- 86] The advantages derived from

the use of ZrO2 as a catalyst ease of separation of products from reaction mixture by

simple filtration recovery and recycling of catalysts etc [87]

14 Oxidation of toluene

Selective catalytic oxidation of toluene to corresponding alcohol aldehyde and

carboxylic acid by molecular oxygen is of great economical and industrial importance

Industrially the oxidation of toluene to benzoic acid (BzOOH) with molecular oxygen is

a key step for phenol synthesis in the Dow Phenol process and for ɛ-caprolactam

formation in Snia-Viscosia process [88- 94] Toluene is also a representative of aromatic

hydrocarbons categorized as hazardous material [95] Thus development of methods for

the oxidation of aromatic compounds such as toluene is also important for environmental

reasons The commercial production of benzoic acid via the catalytic oxidation of toluene

is achieved by heating a solution of the substrate cobalt acetate and bromide promoter in

acetic acid to 250 ordmC with molecular oxygen at several atmosphere of pressure

Although complete conversion is achieved however the use of acidic solvents and

bromide promoter results in difficult separation of product and catalyst large volume of

toxic waste and equipment corrosion The system requires very expensive specialized

equipment fitted with extensive safety features Operating under such extreme conditions

consumes large amount of energy Therefore attempts are being made to make this

7

oxidation more environmentally benign by performing the reaction in the vapor phase

using a variety of solid catalysts [96 97] However liquid-phase oxidation is easy to

operate and achieve high selectivity under relatively mild reaction conditions Many

efforts have been made to improve the efficiency of toluene oxidation in the liquid phase

however most investigation still focus on homogeneous systems using volatile organic

solvents Toluene oxidation can be carried out in

i Solvent free conditions

ii In solvent

Employing heterogeneous catalysts in liquid-phase oxidation of toluene without

solvent would make the process more environmentally friendly Bastock and coworkers

have reported [98] the oxidation of toluene to benzoic acid in solvent free conditions

using a commercial heterogeneous catalyst Envirocat EPAC in the presence of catalytic

amount of carboxylic acid as promoter at atmospheric pressure The reaction was

performed at 110-150 ordmC with oxygen flow rate of 400 mlmin The isolated yield of

benzoic acid was 85 in 22 hours Subrahmanyan et al [99] have performed toluene

oxidation in solvent free conditions using vanadium substituted aluminophosphate or

aluminosilictaes as catalyst Benzaldehyde (BzH) and benzoic acid were the main

products when tert-butyl hydro peroxide was used as the oxidizing agent while cresols

were formed when H2O2 was used as oxidizing agent Raja et al [100101] have also

reported the solvent free oxidation of toluene using zeolite encapsulated metal complexes

as catalysts Air was used as oxidant (35 MPa) The highest conversion (451 ) was

achieved with manganese substituted aluminum phosphate with high benzoic acid

selectivity (834 ) at 150 ordm C in 16 hours Li and coworkers [36-102] have also reported

manganese oxide and copper manganese oxide to be active catalyst for toluene oxidation

to benzoic acid in solvent free conditions with molecular oxygen (10 MPa) at 190-195

ordmC Recently it was observed in this laboratory [103] that when toluene was used as a

solvent for benzyl alcohol (BzOH) oxidation by molecular oxygen at 90 ordmC in the

presence of PtZrO2 as catalyst benzoic acid was obtained with 100 selectivity The

mass balance of the reaction showed that some of the benzoic acid was obtained from

toluene oxidation This observation is the basis of the present study for investigation of

the solvent free oxidation of toluene using PtZrO2 as catalyst

8

The treatment of hazardous wastewater containing organic pollutants in

environmentally acceptable and at a reasonable cost is a topic of great universal

importance Wastewaters from different industries (pharmacy perfumery organic

synthesis dyes cosmetics manufacturing of resin and colors etc) contain toluene

formaldehyde and benzyl alcohol Toluene concentration in the industrial wastewaters

varies between 0007- 0753 g L-1 [104] Toluene is one of the most water-soluble

aromatic hydrocarbons belonging to the BTEX group of hazardous volatile organic

compounds (VOC) which includes benzene ethyl benzene and xylene It is mainly used

as solvent in the production of paints thinners adhesives fingernail polish and in some

printing and leather tanning processes It is a frequently discharged hazardous substance

and has a taste in water at concentration of 004 ndash 1 ppm [105] The maximum

contaminant level goal (MCLG) for toluene has been set at 1 ppm for drinking water by

EPA [106] Several treatment methods including chemical oxidation activated carbon

adsorption and biological stabilization may be used for the conversion of toluene to a

non-toxic substance [107-109 39- 42] Biological treatment is favored because of the

capability of microorganisms to degrade low concentrations of toluene in large volumes

of aqueous wastes economically [110] But efficiency of biological processes decreases

as the concentration of pollutant increases furthermore some organic compounds are

resistant to biological clean up as well [111] Catalytic oxidation to maintain high

removal efficiency of organic contaminant from wastewater in friendly environmental

protocol is a promising alternative Ilyas et al [112] have reported the use of ZrO2 catalyst

for the liquid phase solvent free benzyl alcohol oxidation with molecular oxygen (1atm)

at 373-413 K and concluded that monoclinic ZrO2 is more active than tetragonal ZrO2 for

alcohol oxidation Recently it was reported that Pt ZrO2 is an efficient catalyst for the

oxidation of benzyl alcohol in solvent like n-heptane 1 PtZrO2 was also found to be an

efficient catalyst for toluene oxidation in solvent free conditions [103113] However

some conversion of benzoic acid to phenol was observed in the solvent free conditions

The objective of this work was to investigate a model catalyst (PtZrO2) for the oxidation

of toluene in aqueous solution at low temperature There are to the best of our

knowledge no reports concerning heterogeneous catalytic oxidation of toluene in

aqueous solution

9

15 Oxidation of cyclohexane

Poorly reactive and low-cost cyclohexane is interesting starting materials in the

production of cyclohexanone and cyclohexanol which is a valuable product for

manufacturing nylon-6 and nylon- 6 6 [114 115] More than 106 tons of cyclohexanone

and cyclohexanol (KA oil) are produced worldwide per year [116] Synthesis routes

often include oxidation steps that are traditionally performed using stoichiometric

quantities of oxidants such as permanganate chromic acid and hypochlorite creating a

toxic waste stream On the other hand this process is one of the least efficient of all

major industrial chemical processes as large-scale reactors operate at low conversions

These inefficiencies as well as increasing environmental concerns have been the main

driving forces for extensive research Using platinum or palladium as a catalyst the

selective oxidation of cyclohexane can be performed with air or oxygen as an oxidant In

order to obtain a large active surface the noble metal is usually supported by supports

like silica alumina carbon and zirconia The selectivity and stability of the catalyst can

be improved by adding a promoter (an inactive metal) such as bismuth lead or tin In the

present paper we studied the activity of zirconia as a catalyst and a support for platinum

or palladium using liquid phase oxidation of cyclohexane in solvent free condition at low

temperature as a model reaction

16 Oxidation of phenol

Undesirable phenol wastes are produced by many industries including the

chemical plastics and resins coke steel and petroleum industries Phenol is one of the

EPArsquos Priority Pollutants Under Section 313 of the Emergency Planning and

Community Right to Know Act of 1986 (EPCRA) releases of more than one pound of

phenol into the air water and land must be reported annually and entered into the Toxic

Release Inventory (TRI) Phenol has a high oxygen demand and can readily deplete

oxygen in the receiving water with detrimental effects on those organisms that abstract

dissolved oxygen for their metabolism It is also well known that even low phenol levels

in the parts per billion ranges impart disagreeable taste and odor to water Therefore it is

necessary to eliminate as much of the phenol from the wastewater before discharging

10

Phenols may be treated by chemical oxidation bio-oxidation or adsorption Chemical

oxidation such as with hydrogen peroxide or chlorine dioxide has a low capital cost but

a high operating cost Bio-oxidation has a high capital cost and a low operating cost

Adsorption has a high capital cost and a high operating cost The appropriateness of any

one of these methods depends on a combination of factors the most important of which

are the phenol concentration and any other chemical pollutants that may be present in the

wastewater Depending on these variables a single or a combination of treatments is be

used Currently phenol removal is accomplished with chemical oxidants the most

commonly used being chlorine dioxide hydrogen peroxide and potassium permanganate

Heterogeneous catalytic oxidation of dissolved organic compounds is a potential

means for remediation of contaminated ground and surface waters industrial effluents

and other wastewater streams The ability for operation at substantially milder conditions

of temperature and pressure in comparison to supercritical water oxidation and wet air

oxidation is achieved through the use of an extremely active supported noble metal

catalyst Catalytic Wet Air Oxidation (CWAO) appears as one of the most promising

process but at elevated conditions of pressure and temperature in the presence of metal

oxide and supported metal oxide [45] Although homogeneous copper catalysts are

effective for the wet oxidation of industrial effluents but the removal of toxic catalyst

made the process debatable [117] Recently Leitenburg et al have reported that the

activities of mixed-metal oxides such as ZrO2 MnO2 or CuO for acetic acid oxidation

can be enhanced by adding ceria as a promoter [118] Imamura et al also studied the

catalytic activities of supported noble metal catalysts for wet oxidation of phenol and the

other model pollutant compounds Ruthenium platinum and rhodium supported on CeO2

were found to be more active than a homogeneous copper catalyst [45] Atwater et al

have shown that several classes of aqueous organic contaminants can be deeply oxidized

using dissolved oxygen over supported noble metal catalysts (5 Ru-20 PtC) at

temperatures 393-433 K and pressures between 23 and 6 atm [119] Carlo et al [120]

reported that lanthanum strontium manganites are very active catalyst for the catalytic

wet oxidation of phenol In the present work we explored the effectiveness of zirconia-

supported noble metals (Pt Pd) and bismuth promoted zirconia supported noble metals

for oxidation of phenol in aqueous solution

11

17 Characterization of catalyst

An important step in the field of heterogeneous catalysis is the characterization

of catalysts The field of surface science of catalysis is helpful to examine the structure

and composition of the catalytically active surface and to correlate this information with

catalytic reaction rates selectivity activity and catalyst lifetime Because heterogeneous

catalytic activity is so strongly influence surface structure on an atomic scale the

chemical bonding of adsorbates and the composition and oxidation states of surface

atoms Surface science offers a number of modern techniques that are employed to obtain

information on the morphological and textural properties of the prepared catalyst These

include surface area measurements particle size measurements x-ray diffractions SEM

EDX and FTIR which are the most common used techniques

171 Surface Area Measurements

Surface area measurements of a catalyst play an important role in the field of

surface chemistry and catalysis The technique of selective adsorption and interpretation

of the adsorption isotherm had to be developed in order to determine the surface areas

and the chemical nature of adsorption From the knowledge of the amount adsorbed and

area occupied per molecule (162 degA for N2) the total surface area covered by the

adsorbed gas can be calculated [121]

172 Particle size measurement

The size of particles in a sample can be measured by visual estimation or by the

use of a set of sieves A representative sample of known weight of particles is passed

through a set of sieves of known mesh sizes The sieves are arranged in downward

decreasing mesh diameters The sieves are mechanically vibrated for a fixed period of

time The weight of particles retained on each sieve is measured and converted into a

percentage of the total sample This method is quick and sufficiently accurate for most

purposes Essentially it measures the maximum diameter of each particle In our

laboratory we used sieves as well as (analystte 22) particle size measuring instrument

12

173 X-ray differactometry

X-ray powder diffractometry makes use of the fact that a specimen in the form of

a single-phase microcrystalline powder will give a characteristic diffraction pattern A

diffraction pattern is typically in the form of diffraction angle Vs diffraction line

intensity A pattern of a mixture of phases make up of a series of superimposed

diffractogramms one for each unique phase in the specimen The powder pattern can be

used as a unique fingerprint for a phase Analytical methods based on manual and

computer search techniques are now available for unscrambling patterns of multiphase

identification Special techniques are also available for the study of stress texture

topography particle size low and high temperature phase transformations etc

X-ray diffraction technique is used to follow the changes in amorphous structure

that occurs during pretreatments heat treatments and reactions The diffraction pattern

consists of broad and discrete peaks Changes in surface chemical composition induced

by catalytic transformations are also detected by XRD X-ray line broadening is used to

determine the mean crystalline size [122]

174 Infrared Spectroscopy

The strength and the number of acid sites on a solid can be obtained by

determining quantitatively the adsorption of a base such as ammonia quinoline

pyridine trimethyleamine In this method experiments are to be carried out under

conditions similar to the reactions and IR spectra of the surface is to be obtained The

IR method is a powerful tool for studying both Bronsted and Lewis acidities of surfaces

For example ammonia is adsorbed on the solid surface physically as NH3 it can be

bonded to a Lewis acid site bonding coordinatively or it can be adsorbed on a Bronsted

acid site as ammonium ion Each of the species is independently identifiable from its

characteristic infrared adsorption bands Pyridine similarly adsorbs on Lewis acid sites as

coordinatively bonded as pyridine and on Bronsted acid site as pyridinium ion These

species can be distinguished by their IR spectra allowing the number of Lewis and

Bronsted acid sites On a surface to be determined quantitatively IR spectra can monitor

the adsorbed states of the molecules and the surface defects produced during the sample

pretreatment Daturi et al [124] studied the effects of two different thermal chemical

13

pretreatments on high surface areas of Zirconia sample using FTIR spectroscopy This

sample shows a significant concentration of small pores and cavities with size ranging 1-

2 nm The detection and identification of the surface intermediate is important for the

understanding of reaction mechanism so IR spectroscopy is successfully employed to

answer these problems The reactivity of surface intermediates in the photo reduction of

CO2 with H2 over ZrO2 was investigated by Kohno and co-workers [125] stable surface

species arises under the photo reduction of CO2 on ZrO2 and is identified as surface

format by IR spectroscopy Adsorbed CO2 is converted to formate by photoelectron with

hydrogen The surface format is a true reaction intermediate since carbon mono oxide is

formed by the photo reaction of formate and carbon dioxide Surface format works as a

reductant of carbon dioxide to yield carbon mono oxide The dependence on the wave

length of irradiated light shows that bulk ZrO2 is not the photoactive specie When ZrO2

adsorbs CO2 a new bank appears in the photo luminescence spectrum The photo species

in the reaction between CO2 and H2 which yields HCOO is presumably formed by the

adsorption of CO2 on the ZrO2 surface

175 Scanning Electron Microscopy

Scanning electron microscopy is employed to determine the surface morphology

of the catalyst This technique allows qualitative characterization of the catalyst surface

and helps to interpret the phenomena occurring during calcinations and pretreatment The

most important advantage of electron microscopy is that the effectiveness of preparation

method can directly be observed by looking to the metal particles From SEM the particle

size distribution can be obtained This technique also gives information whether the

particles are evenly distributed are packed up in large aggregates If the particles are

sufficiently large their shape can be distinguished and their crystal structure is then

determining [126]

14

Chapter 2

Literature review

Zirconia is a technologically important material due to its superior hardness high

refractive index optical transparency chemical stability photothermal stability high

thermal expansion coefficient low thermal conductivity high thermomechanical

resistance and high corrosion resistance [127] These unique properties of ZrO2 have led

to their widespread applications in the fields of optical [128] structural materials solid-

state electrolytes gas-sensing thermal barriers coatings [129] corrosion-resistant

catalytic [130] and photonic [131 132] The elemental zirconium occurs as the free oxide

baddeleyite and as the compound oxide with silica zircon (ZrO2SiO2) [133] Zircon is

the most common and widely distributed of the commercial mineral Its large deposits are

found in beach sands Baddeleyite ZrO2 is less widely distributed than zircon and is

usually found associated with 1-15 each of silica and iron oxides Dressing of the ore

can produce zirconia of 97-99 purity Zirconia exhibit three well known crystalline

forms the monoclinic form is stable up to 1200 C the tetragonal is stable up to 1900 C

and the cubic form is stable above 1900C In addition to this a meta-stable tetragonal

form is also known which is stable up to 650C and its transformation is complete at

around 650-700 C Phase transformation between the monoclinic and tetragonal forms

takes place above 700C accompanied with a volume change Hence its mechanical and

thermal stability is not satisfactory for the use of ceramics Zirconia can be prepared from

different precursors such as ZrOCl2 8H2O [134 135] ZrO(NO3)22H2O[136 137] Zr

isopropoxide [137 139] and ZrCl4 [140 141] in order to attained desirable zirconia

Though synthesizing of zirconia is a primary task of chemists the real challenge lies in

preparing high surface area zirconia and maintaining the same HSA after high

temperature calcination

Chuah et al [142] have studied that high-surface-area zirconia can be prepared by

precipitation from zirconium salts The initial product from precipitation is a hydrous

zirconia of composition ZrO(OH)2 The properties of the final product zirconia are

affected by digestion of the hydrous zirconia Similarly Chuah et al [143] have reported

15

that high surface area zirconia was produced by digestion of the hydrous oxide at 100degC

for various lengths of time Precipitation of the hydrous zirconia was effected by

potassium hydroxide and sodium hydroxide the pH during precipitation being

maintained at 14 The zirconia obtained after calcination of the undigested hydrous

precursors at 500degC for 12 h had a surface area of 40ndash50 m2g With digestion surface

areas as high as 250 m2g could be obtained Chuah [144] has reported that the pH of the

digestion medium affects the solubility of the hydrous zirconia and the uptake of cations

Both factors in turn influence the surface area and crystal phase of the resulting zirconia

Between pH 8 and 11 the surface area increased with pH At pH 12 longer-digested

samples suffered a decrease in surface area This is due to the formation of the

thermodynamically stable monoclinic phase with bigger crystallite size The decrease in

the surface area with digestion time is even more pronounced at pH 137 Calafat [145]

has studied that zirconia was obtained by precipitation from aqueous solutions of

zirconium nitrate with ammonium hydroxide Small modifications in the preparation

greatly affected the surface area and phase formation of zirconia Time of digestion is the

key parameter to obtain zirconia with surface area in excess of 200 m2g after calcination

at 600degC A zirconia that maintained a surface area of 198 m2g after calcination at 900degC

has been obtained with 72 h of digestion at 80degC Recently Chane-Ching et al [146] have

reported a general method to prepare large surface area materials through the self-

assembly of functionalized nanoparticles This process involves functionalizing the oxide

nanoparticles with bifunctional organic anchors like aminocaproic acid and taurine After

the addition of a copolymer surfactant the functionalized nanoparticles will slowly self-

assemble on the copolymer chain through a second anchor site Using this approach the

authors could prepare several metal oxides like CeO2 ZrO2 and CeO2ndashAl(OH)3

composites The method yielded ZrO2 of surface area 180 m2g after calcining at 500 degC

125 m2g for CeO2 and 180 m2g for CeO2-Al (OH)3 composites Marban et al [147]

have been described a general route for obtaining high surface area (100ndash300 m2g)

inorganic materials made up by nanosized particles (2ndash8 nm) They illustrate that the

methodology applicable for the preparation of single and mixed metallic oxides

(ferrihydrite CuO2CeO2 CoFe2O4 and CuMn2O4) The simplicity of technique makes it

suitable for the mass scale production of complex nanoparticle-based materials

16

On the other hand it has been found that amorphous zirconia undergoes

crystallization at around 450 degC and hence its surface area decreases dramatically at that

temperature At room temperature the stable crystalline phase of zirconia is monoclinic

while the tetragonal phase forms upon heating to 1100ndash1200 degC Under basic conditions

monoclinic crystallites have been found to be larger in size than tetragonal [144] Many

researchers have tried to maintain the HSA of zirconia by several means Fuertes et al

[148] have found that an ordered and defect free material maintains HSA even after

calcination He developed a method to synthesize ordered metal oxides by impregnation

of a metal salt into siliceous material and hydrolyzing it inside the pores and then

removal of siliceous material by etching leaving highly ordered metal oxide structures

While other workers stabilized tetragonal phase ZrO2 by mixing with CaO MgO Y2O3

Cr2O3 or La2O3 at low temperature Zirconia and mixed oxide zirconia have been widely

studied by many methods including solndashgel process [149- 156] reverse micelle method

[157] coprecipitation [158142] and hydrothermal synthesis [159] functionalization of

oxide nanoparticles and their self-assembly [146] and templating [160]

The real challenge for chemists arises when applying this HSA zirconia as

heterogeneous catalysts or support for catalyst For this many propose researchers

investigate acidic basic oxidizing and or reducing properties of metal oxide ZrO2

exhibits both acidic and basic properties at its surface however the strength is rather

weak ZrO2 also exhibits both oxidizing and reducing properties The acidic and basic

sites on the surface of oxide both independently and collectively An example of

showing both the sites to be active is evidenced by the adsorption of CO2 and NH3 SiO2-

Al2O3 adsorbs NH3 (a basic molecule) but not CO2 (an acid molecule) Thus SiO2-Al2O3

is a typical solid acid On the other hand MgO adsorb CO2 and NH3 and hence possess

both acidic and basic properties ZrO2 is a typical acid-base bifunctional oxide ZrO2

calcined at 600 C exhibits 04μ molm2 of acidic sites and 4μ molm2 of basic sites

Infrared studies of the adsorbed Pyridine revealed the presence of Lewis type acid sites

but not Broansted acid sites [161] Acidic and basic properties of ZrO2 can be modified

by the addition of cationic or anionic substances Acidic property may be suppressed by

the addition of alkali cations or it can be promoted by the addition of anions such as

halogen ions Improvement of acidic properties can be achieved by the addition of sulfate

17

ion to produce the solid super acid [162 163] This super acid is used to catalyze the

isomerrization of alkanes Friedal-Crafts acylation and alkylation etc However this

supper acid catalyst deactivates during alkane isomerization This deactivation is due to

the removal of sulphur reduction of sulphur and fermentation of carbonaceous polymers

This deactivation may be overcome by the addition of Platinum and using the hydrogen

in the reaction atmosphere

Owing to its unique characteristics ZrO2 displays important catalytic properties

ZrO2 has been used as a catalyst for various reactions both as a single oxide and

combined oxides with interesting results have been reported [164] The catalytic activity

of ZrO2 has been indicated in the hydrogenation reaction [165] aldol addition of acetone

[166] and butane isomerization [167] ZrO2 as a support has also been used

successively Copper supported zirconia is an active catalyst for methanation of CO2

[168] Methanol is converted to gasoline using ZrO2 treated with sulfuric acid

Skeletal isomerization of hydrocarbon over ZrO2 promoted by platinum and

sulfate ions are the most promising reactions for the use of ZrO2 based catalyst Bolis et

al [169] have studied chemical and structural heterogeneity of supper acid SO4 ZrO2

system by adsorbing CO at 303K Both the Bronsted and Lewis sites were confirmed to

be present at the surface Gomez et al [170] have studied ZirconiaSilica-gel catalysts for

the decomposition of isopropanol Selectivity to propene or acetone was found to be a

function of the preparation methods of the catalysts Preparation of the catalyst in acid

developed acid sites and selective to propene whereas preparation in base is selective to

acetone Tetragonal Zirconia has been investigated [171] for its surface reactivity and

was found to exhibits differences with respect to the better-known monoclinic phase

Yttria-stabilized t-ZrO2 and a commercial powder ceramic material of similar chemical

composition were investigated by means of Infrared spectroscopy and adsorption

microcalarometry using CO as a probe molecule to test the surface acidic properties of

the solids The surface acidic properties of t-ZrO2 were found to depend primarily on the

degree of sintering the preparation procedure and the amount of Y2 O3 added

Yori et al [172] have studied the n-butane isomerization on tungsten oxide

supported on Zirconia Using different routes of preparation of the catalyst from

ammonium metal tungstate and after calcinations at 800C the better WO3 ZrO2 catalyst

18

showed performance similar to sulfated Zirconia calcined at 620 C The effects of

hydrogen treated Zirconia and Pt ZrO2 were investigated by Hoang et al [173] The

catalysts were characterized by using techniques TPR hydrogen chemisorptions TPDH

and in the conversion of n-hexane at high temperature (650 C) ZrO2 takes up hydrogen

In n-hexane conversions high temperature hydrogen treatment is pre-condition of

the catalytic activity Possibly catalytically active sites are generated by this hydrogen

treatment The high temperature hydrogen treatment induces a strong PtZrO2 interaction

Hoang and Co-Workers in another study [174] have investigated the hydrogen spillover

phenomena on PtZrO2 catalyst by temperature programmed reduction and adsorption of

hydrogen At about 550C hydrogen spilled over from Pt on to the ZrO2 surface Of this

hydrogen spill over one part is consumed by a partial reduction of ZrO2 and the other part

is adsorbed on the surface and desorbed at about 650 C This desorption a reversible

process can be followed by renewed uptake of spillover hydrogen No connection

between dehydroxylable OH groups and spillover hydrogen adsorption has been

observed The adsorption sites for the reversibly bound spillover hydrogen were possibly

formed during the reducing hydrogen treatment

Kondo et al [175] have studied the adsorption and reaction of H2 CO and CO2 over

ZrO2 using IR spectroscopy Hydrogen is dissociatively adsorbed to form OH and Zr-H

species and CO is weakly adsorbed as the molecular form The IR spectrum of adsorbed

specie of CO2 over ZrO2 show three main bands at Ca 1550 1310 and 1060 cm-1 which

can be assigned to bidentate carbonate species when hydrogen was introduced over CO2

preadsorbed ZrO2 formate and methoxide species also appears It is inferred that the

formation of the format and methoxide species result from the hydrogenation of bidentate

carbonate species

Miyata etal [176] have studied the properties of vanadium oxide supported on ZrO2

for the oxidation of butane V-Zr catalyst show high selectivity to furan and butadiene

while high vanadium loadings show high selectivity to acetaldehyde and acetic acid

Schild et al [177] have studied the hydrogenation reaction of CO and CO2 over

Zirconia supported palladium catalysts using diffused reflectance FTIR spectroscopy

Rapid formation of surface format was observed upon exposure to CO2 H2 Similarly

CO was rapidly transformed to formate upon initial adsorption on to the surfaces of the

19

activated catalysts The disappearance of formate as observed in the FTIR spectrum

could be correlated with the appearance of gas phase methane

Recently D Souza et al [178] have reported the preparation of thermally stable

HSA zirconia having 160 m2g by a ldquocolloidal digestingrdquo route using

tetramethylammonium chloride as a stabilizer for zirconia nanoparticles and deposited

preformed Pd nanoparticles on it and screened the catalyst for 1-hexene hydrogenation

They have further extended their studies for the efficient preparation of mesoporous

tetragonal zirconia and to form a heterogeneous catalyst by immobilizing a Pt colloid

upon this material for hydrogenation of 1- hexene [179]

20

Chapter 1amp 2

References

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4 Puzari A Jubaraj B J Mol Catal A Chem 2002 187 149

5 Gates B C Catalytic Chemistry John Wiley and Sons New York 1992

6 Yamaguchi T Catal Today 1994 20 199

7 Ozawa M Kimura M J Mater Sci Lett 1990 9 446

8 Inoue M Kominami H Inui T Appl Catal A 1993 97 L25-30

9 Aiken B Hsu W P Matijevid E J Mater Sci1990 25 1886

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37 Heyns K Blazejewicz L Tetrahedron 1960 9 67

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38 Heyns K Paulsen H in ldquo Newer Methods of Preparative Organic

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39 Christoskova St Stoyanova M Water Res 2002 36 2297-2303

40 Christoskova St Final Report Contract X-123 National Science Fund

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41 Christoskova St Stoyanova M Water Res 2000 3096 1ndash5

42 Christoskova St Danova N Georgieva M Argirov O Mehandjiev D

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43 Munter R Proc Estonian Sci Chem 2001 50 59-804

44 Mishra V S Mahajani VV Joshi JB Ind Eng Chem Res 1995 34 2

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46 Pintar Catal Today 2003 77 451

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48 Luck F Catal Today 1999 53 81

49 Kolaczkowski S T Plucinski P Beltran FJ Rivas F Lurgh DB Chem

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51 Fortuny C Ferrer C Bengoa J Font and Fabregat A Catal Today 1995

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52 Alejandre F Medina A Fortuny P Salagre and Suerias JE Appl Catal

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53 Alvarez PM McLurgh D Plucinsky P Ind Eng Chem Res 2002 41

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54 Hu X Lei L Chu HP Yue PL Carbon 1999 37 631

55 Santos A Yustos P Durban B Garcia-Ochoa F Environ Sci Technol

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56 Fortuny A Bengoa C Font J Fabregat A J Hazard Mater 1999 64

181

57 Zhang Q Chuang KT Environ Sci Technol1999 33 3641

58 Zhang Q Chuang KT Can J Chem Eng1999 77 399

23

59 Wu Q Hu X Yue PL Zhao XS Lu GQ Appl Catal B Environ

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60 Stuber F Polaert I Delmas H Font J Fortuny A Fabregat A J Chem

Technol Biotechnol 2001 76 743

61 Hamoudi S Larachi F Sayari A J Catal 1998 77 247

62 Hamoudi S Larachi F Cerrella G Casssanello M Ind Eng Chem Res

1998 37 3561

63 Pintar and Levec J J Catal 1992 135 345

64 Alejandre A Medina F Rodriguez X Salagre P Suerias JE J Catal

1999 188 311

65 Hamoudi S Sayari A Belkacemi K Bonneviot L Larachi F Catal

Today 2000 62 379

66 Hussain ST Sayari A Larachi F J Catal 2001 201153

67 Hussain ST Sayari A Larachi F Appl Catal B Environ 2001 34 1

68 Alejandre A Medina F Rodriguez X Salagre P CesterosYSuerias

JE Appl Catal B Environ 2001 30 195

69 Gallezot P Laurain N Isnard P Appl Catal B Environ 1996 9 L11

70 Beziat JC Besson M Gallezot P Durecu S Ind Eng Chem Res 1999

381310

71 Pintar Besson M Gallezot P Appl Catal B Environ 2001 30 123


73 Duprez S Delano F Barbier J Isnard P Blanchard G Catal Today

1996 29 317

74 An W Zhang Q Ma Y Chuang KT Catal Today 2001 64 289

75 Hocevar S Batista J Levec J J Catal 1999 184 39

76 Hocevar S Krasovec UO Orel B Arico A S Kim H Appl Catal B

Environ 2000 28113

77 Reddy M Thrimurthulu G Saikia P Bharali P J Mole Catal A

Chemical 2007 275 167-173

78 Solinas V Rombi E Ferino I Cutrufello M G Coloacuten G Naviacuteo J

A J Mole Catal A Chemical 2003 204 629-635

24

79 Sun YH Sermon PAJ Chem Soc Chem Commu 1993 16 1242

80 Ma Z Yang C Wei W Li W Sun Y J Mole Catal A Chemical 2005

231 75ndash81

81 Zong H Hattori H Tanabe K J Catal 1998 36 139

82 Vijay S Wolf EE Appl Catal A Gen 2004 264 117-124

83 Hwanga H C Chena X R Wonga ST Chenc CL Mou CY Appl

Catal A General 2007 323 9-17

84 Wong S Li T Cheng S Lee J Mou C J Catal 2003 215 45ndash56

85 Mamedov EA Corberfin V C Appl Catal A General 1995 127 1-40

86 Tomishig K Ikeda Y Sakaihori T Fujimoto K J Catal 2000 192 355-

362

87 Ilyas M Sadiq M Chin J Chem2008 26 941

88 Collinn D E Richery F A in J A Kent (Eds) Reigle Handbook of

Industrial Chemistry C B S New Delhi 1987 Chap 22 p 800

89 Dow Chemical Corp US Patent 2 727 926 1955

90 California Research Corp US Patent 2 762 838 1956

91 Bujis W J Molecular Catal A 1999146 237

92 Dubreuil JF Serna JG Verdugo EG Dudda L M Aird G R

Thomas W B Poliakoff M J Supercritical Fluids 2006 39 220

93 Bujjs W Frijns L H B Offermanns M R J US Patent 5 210 331

1993

94 Pennington J in C A Heaton (eds) An Introduction to Industrial

Chemistry Leonard Hill London 1984 Chap 9 p 323

95 US Environmental Protection Agency Integrated Risk Information

System (IRIS) on Toluene National Center for Environmental Assistance

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96 Bulushev D A Rainone F Minsker L K Catalysis Today 2004 96

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97 Worayingyong A Nitharach A Poo-arporn Y Science Asia 2004

30 341

98 Bastock T E Clark J H Martin K Trentbirth B W Green

25

Chemistry 2002 4 615

99 Subrahmanyama Ch Louisb B Viswanathana B Renkenb A

Varadarajan TK Applied Catalysis A General 2005 282 67

100 Raja R Thomas J M Dreyerd V Catalysis Letters 2006110 179

101 Thomas J M Raja R Catalysis Today 2006 117 22

102 Li X Xu J Zhou L Wang F Gao J Chen C Ning J Ma H

Catalysis Letters 2006 110 255

103 Ilyas M Sadiq M ChemEng Technol 2007 30 1391

104 Enright A M Collins G FlahertyVO Water Res 2007 411465

105 httpwwweco-usanettoxicstolueneshtml

106 httpwwwfreedrinkingwatercomwater-contaminanttoluene-

contaminantsremoval-waterhtm

107 Langwaldt J H Puhakka J A Environ Pollut 2000 107 197

108 De Nardi IR Varesche MB Zaiat M Foresti E Water Sci Technol

2002 45 180

109 De Nardi I R Ribeiro R Zaiat M ForestiE Process Biochem 2005

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110 Stenstrom M K Cardinal L Libra J Environ Prog 19898 107

111 Mantzavinos D Sahibzada M Livingston A Metcalfe I Hellgardt

K Catal Today 1999 53 93

112 Ilyas M Sadiq M KhanI Chin J Catal 2007 28 413

113 Ilyas M Sadiq M Catal Lett (Online first) DOI 101007s10562-008-

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114 Chandalia SB Oxidation of Hydrocarbons 1st Ed Sevak Bombay

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115 Musser MT inW Gerhartz (Ed) Encyclopedia of Industrial Chemistry

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116 Suresh AK Sharma MM Sridhar T Ind Eng Chem Res 2000 39

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117 Wang R Qi Y Shen Z Wu Z Huadong Huagong Xueyuan Xue

1982 4 411-18

26

118 Leitenburg C Goi D Primavera A Trovarelli A Dolcetti G Appl

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119 Atwater J E Akse J R Mckinnis J A Thompson J O Appl Catal

B 1996 11 L11-L18

120 Carlo R Federico C Silvia B Ombretta P Guido B Appl Catal B

Environ 2008 84 678-683

121 Adomson AW ldquoPhysical Chemistry of Surfacesrdquo 4th ed John Wiley and

sons Newyork 1982

122 Packertand M Baikev A JChem Soc Faraday Trans 1 1985 81

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123 Yamashita H Yoschikawas M Fanahiki T Yoshida S J Chem Soc

Faraday Trans1 1986 82 1771

124 Daturi M Binet C Berneal S Omil J A P Larvalley J C J Chem

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125 Kohno Y Tanaka T Funaziki T YoshidaS J Chem Soc Faraday

Trans 1998 94 1875

126 Che and Bennet CO ldquoAdvances in Catalysisrdquo Academic Press Inc

1998 36 55-97

127 Harrison HDE McLamed NT Subbarao EC J Electrochem Soc

1963 110 23

128 Kourouklis GA Liarokapis E J Am Ceram Soc1991 74 52

129 Birkby I Stevens R Key Eng Mater 1996 122 527

130 Murase Y Kato E J Am Ceram Soc1982 66196

131 Sorek Y Zevin M Reisfeld R Hurvita T RuschinS Chem Mater

1997 9 670

132 Salas P Rosa-Cruz E D Mendoza D Gonzales P Rodryguez R

Castano VM Mater Lett 2000 45 241

133 Stevens R ldquoAn Introduction to Zirconiardquo Magnesium Elecktron Ltd

Publication no113 Litho 2000 Twickenhom UK July (1986)

134 Arata K Hino H in ldquoProceeding 9th International Congress on

27

Catalysis Calgary 1088rdquo (MJPhillips and M ternan Eds) Vol 4 p

1727 Chem Institute of Canada Ottawa 1988

135 Sohn JR Jang HJ J Mol Catal 1991 64 349

136 Garvie RC J Phy Chem 1965 69 1238

137 Yamaguchi T Tanabe K Kung Y C Matter Chem Phys 1986 16

67

138 Bensitel M Saur O Lavalley J C Mabilon G Matter Chem Phys

1987 17 249

139 Morterra C Cerrato G Emanuel C Bolis V J Catal 1993 142 349

140 Srinivasan R Davis B H Catal Lett 1992 14 165

141 Ardizzone S Bassi G Matter Chem Phys 1990 25 417

142 Chuah G K Jaenicke S Pong B K J Catal1998 175 80-92

143 Chuah G K Jaenicke S Appl Catal A General 1997 163 261-273

144 Chuah G K Catal Today 1999 49 131

145 Calafat A Studies Surf Sci Catal 1998 118 837-843

146 Chane-Ching JY Cobo F Aubert D Harvey HG Airiau M

Corma A Chem Eur J 2005 11 979

147 G Marbaacuten A B Fuertes T V Soliacutes Micropor Mesopor Mater

2008112 291-298

148 Fuertes AB J Phys Chem Solids 2005 66 741

149 Parvulescu V Coman NS Grange P Parvulescu VI Appl Catal

A1999 176 27

150 Parvulescu VI Parvulescu V Endruschat U Lehmann CW

Grange P Poncelet G Bonnemann H Micropor Mesopor Mater

2001 44 221

151 Parvulescu VI Bonnemann H Parvulescu V Endruschat U

Rufinska A Lehmann CW Tesche B Poncelet G Appl Catal

A2001 214 273

152 Ward DA Ko EI J Catal 1995 157 321

153 Mamak M Coombs N Ozin GA Chem Mater 2001 13 3564

154 Li Y He D YuanY Cheng Z Zhu Q Energy Fuels 2001 151434

28

155 Xu W Luo Q Wang H Francesconi LC Stark RE Akins DL

J Phys Chem B 2003 107 497

156 Navio JA Hidalgo MC Colon G Botta SG Litter MI

Langmuir 2001 17 202

157 Sun W Xu L Chu Y Shi W J Colloid Interface Sci 2003 266

99

158 Stichert W Schuth F J Catal 1998 174 242

159 Tani E Yoshimura M Somiya S J Am Ceram Soc 1983 6611

160 Kristof C Thierry L Katrien A Pegie C Oleg L Gustaaf VG

Rene VG Etienne FV J Mater Chem 2003 13 3033

161 Nakano Y Izuka T Hattori H Taanabe K J Catal 1978 51 1

162 Zarkalis A S Hsu C Y Gates B C Catal Lett 1996 37 5

163 Rezgui S Gates B C Catal Lett 1996 37 5

164 Tanabe K YamaguchiT Catal Today 1994 20 185

165 Nakano Y Yamaguchi K Tanabe K J Catal 1983 80 307

166 Zong H Hattori H Tanabe K J Catal 198836139

167 Pajonk G M Tanany A E React Kinet Catal Lett1992 47 167

168 DeniseB SneedenRPA Beguim B Cherifi O Appl Catal

198730353

169 Bolis V Cerrate G Morterra C Langmuir 1997 13 888

170 Gomez R LopezT Tzompantzi F Garciafigueroa E Acosta D W

Novaro O Langmuir 1997 13 970

171 Morterra Cerrato G Bolis V Lamberti C Ferroni L Montanaro

LJ Chem Soc Faraday Trans 1995 91 113

172 Yori J C Vera C R Peraro J M Appl CatalA Gen 1997 163 165

173 Hoang D L Lieske H Catal Lett 1994 27 33

174 Hoang DL Berndt H LieskeH Catal Lett 1995 31165

175 Kondo J Abe H Sakata Y Maruya K Domen K Onishi T

JChem Soc Faraday TransI 1988 84 511

176 Miyata H Kohna M Ono I Ohno T Hatayana F J Chem Soc

Faraday Trans I 1989 85 3663

29

177 Schild C Wokeun A Baiker A J Mol Catal 1990 63 223

178 Souza L D Subaie J S Richards R M J Colloid Interface Sci 2005

292 476ndash485

179 Souza L D Suchopar A Zhu K Balyozova D Devadas M

Richards R M Micropor Mesopor Mater 2006 88 22ndash30

30

Chapter 3

Experimental

31 Material

ZrOCl28H2O (Merck 8917) commercial ZrO2 ( Merk 108920) NH4OH (BDH

27140) AgNO3 (Merck 1512) PtCl4 (Acros 19540) Palladium (II) chloride (Scharlau

Pa 0025) benzyl alcohol (Merck 9626) cyclohexane (Acros 61029-1000) cyclohexanol

(Acros 27870) cyclohexanone (BDH 10380) benzaldehyde (Scharlu BE0160) toluene

(BDH 10284) phenol (Acros 41717) benzoic acid (Merck 100136) alizarin

(Acros 400480250) Potassium Iodide (BDH102123B) 24-Dinitro phenyl hydrazine

(BDH100099) and trans-stilbene (Aldrich 13993-9) were used as received H2

(99999) was prepared using hydrogen generator (GCD-300 BAIF) Nitrogen and

Oxygen were supplied by BOC Pakistan Ltd and were further purified by passing

through traps (CRSInc202268) to remove traces of water and oil Traces of oxygen

from nitrogen gas were removed by using specific oxygen traps (CRSInc202223)

32 Preparation of catalyst

Two types of ZrO2 were used in this study

i Laboratory prepared ZrO2

ii Commercial ZrO2

321 Laboratory prepared ZrO2

Zirconia was prepared using an aqueous solution of zirconyl chloride [1-4] with

the drop wise addition of NH4OH for 4 hours (pH 10-12) with continuous stirring The

precipitate was washed with triply distilled water using a Soxhletrsquos apparatus for 24 hrs

until the Cl- test with AgNO3 was found to be negative Precipitate was dried at 110 degC

for 24 hrs After drying it was calcined with programmable heating at a rate of 05

degCminute to reach 950 degC and was kept at that temperature for 4 hrs Nabertherm C-19

programmed control furnace was used for calcinations

31

Figure 1

Modified Soxhletrsquos apparatus

32

322 Optimal conditions for preparation of ZrO2

Optimal conditions were set for obtaining predictable results i concentration ~

005M ii pH ~12 iii Mixing time of NH3 ~12 hours iv Aging ~ 48 hours v Washing

~24h in modified Soxhletrsquos apparatus vi Drying temperature~110 0C for 24 hours in

temperature control oven

323 Commercial ZrO2

Commercially supplied ZrO2 was grounded to powder and was passed through

different US standard test sieves mesh 80 100 300 to get reduced particle size of the

catalyst The grounded catalyst was calcined as above

324 Supported catalyst

Supported Catalysts were prepared by incipient wetness technique For this

purpose calculated amount (wt ) of the precursor compound (PdCl4 or PtCl4) was taken

in a crucible and triply distilled water was added to make a paste Then the required

amount of the support (ZrO2) was mixed with it to make a paste The paste was

thoroughly mixed and dried in an oven at 110 oC for 24 hours and then grounded The

catalyst was sieved and 80-100 mesh portions were used for further treatment The

grounded catalyst was calcined again at the rate of 05 0C min to reach 950 0C and was

kept at 950 0C for 4 hours after which it was reduced in H2 flow at 280 ordmC for 4 hours

The supported multi component catalysts were prepared by successive incipient wetness

impregnation of the support with bismuth and precious metals followed by drying and

calcination Bismuth was added first on zirconia support by the incipient wetness

impregnation procedure After drying and calcination Bizirconia was then impregnated

with the active metals such as Pd or Pt The final sample then underwent the same drying

and calcination procedure The metal loading of the catalyst was calculated from the

weight of chemicals used for impregnation

33 Characterization of catalysts

33

XRD analyses were performed using a JEOL (JDX-3532) diffractometer with

CuKa radiation (k = 15406 A˚) operated at 40 kV and 20 mA BET surface area of the

catalyst was determined using a Quanta chrome (Nova 2200e) surface area and pore size

analyzer The samples of ZrO2 was heat-treated at a rate of 05 ˚ Cmin to 950 ˚ C and

maintained at that temperature for 4 h in air and then allowed to cool to room

temperature Thus pre-treated samples were used for surface area and isotherm

measurements N2 was used as an adsorbate For surface area measurements seven-point

isotherm data were considered (PP0 between 0 and 03) Particle size was measured by

analysette 22 compact (Fritsch Germany) FTIR spectra were recorded with Prestige 21

Shimadzu Japan in the range 500-4000cm-1 Furthermore SEM and EDX measurements

were performed using scanning electron microscope of Joel 50 H super prob 733

34 Experimental setups for different reaction

In the present study we use three types of experimental set ups as shown in

(Figures 2 3 4) The gases O2 or N2 or a mixture of O2 and N2 was passed through the

reactor containing liquid (reactant) and solid catalyst dispersed in it The partial pressures

of the gases passed through the reactor were varied for various experiments All the pipes

used in the systemrsquos assembly were of Teflon tubes (quarter inch) with Pyrex glass

connections and stopcocks The gases flow was regulated by stainless steel and Teflon

needle valves The reactor was heated by heating tapes connected to a temperature

controller or by hot water circulation The reactor was connected to a condenser with

cold-water circulation supply in order to avoid evaporation of products reactant The

desired partial pressure of the gases was controlled by mixing O2 and N2 (in a particular

proportion) having a constant desired flow rate of 40 cm3 min-1 The flow was measured

by flow meter After a desired period of time the reaction was stopped and the reaction

mixture was filtered to remove the solid catalyst The filtered reaction mixture was kept

in sealed bottle and was used for further analysis

34

Figure 2

Experimental setup for oxidation reactions in

solvent free conditions

35

Figure 3


ecofriendly solvents

36

Figure 4

Experimental setup for solvent free oxidation of

toluene in dry conditions

37

35 Liquid-phase oxidation in solvent free conditions

The liquid-phase oxidation in solvent free conditions was carried out in a

magnetically stirred Pyrex glass single walled flat bottom three-necked batch reactor

equipped with a reflux condenser and a mercury thermometer for measuring the reaction

temperature The reaction temperature was maintained by using heating tapes A

predetermined quantity (10 ml) was taken in the reactor and 02 g of catalyst was then

added O2 and N2 gases at atmospheric pressure were allowed to pass through the reaction

mixture at a flow rate of 40 mlmin at a fixed temperature All the reactants were heated

to the reaction temperature before adding to the reactor Samples were withdrawn from

the reaction mixture at predetermined time intervals

351 Design of reactor for liquid phase oxidation in solvent free condition

Figure 5

Reactor used for solvent free reactions

38

36 Liquid-phase oxidation in ecofriendly solvents

The liquid-phase oxidation in ecofriendly solvent was carried out in a

magnetically stirred Pyrex glass double walled flat bottom three-necked batch reactor


temperature The reaction temperature was maintained by using water circulator

(WiseCircu Fuzzy control system) A predetermined quantity of substrate solution was

taken in the reactor and a desirable amount of catalyst was then added The reaction

during heating period was negligible since no direct contact existed between oxygen and

catalyst O2 and N2 gases at atmospheric pressure were allowed to pass through the

reaction mixture at a flow rate of 40 mlmin at a fixed temperature When the temperature

and pressure reached the designated values the stirrer was turned on at 900 rpm

361 Design of reactor for liquid phase oxidation in ecofriendly solvents

Figure 6

Reactor used for liquid phase oxidation in


39

37 Analysis of reaction mixture

The reaction mixture was filtered and analyzed for products by [4-9]

i chemical methods

This method adopted for the determination of ketone aldehydes in a reaction

mixture 5 cm3 of the filtered reaction mixture was added to 250cm3 conical

flask containing 50cm3 of a saturated solution of pure 2 4 ndash dinitro phenyl

hydrazine in 2N HCl (containing 4 mgcm3) and was placed in ice to achieve 0

degC Precipitate (hydrazone) formed after an hour was filtered thoroughly

washed with 2N HCl and distilled water respectively and dried at 110 degC in

oven Then weigh the dried precipitate

ii Thin layer chromatography

Thin layer chromatographic analysis was carried out using standard

chromatographic plates (Merck) with silica gel 60 F254 support (Merck TLC

105554 and PLC 113793) Ethyl acetate (10 ) in cyclohexane was used as

eluent

iii FTIR (Shimadzu IRPrestigue- 21)

Diffuse reflectance spectra of solids (trans-Stilbene) were recorded on

Shimadzu IRPrestigue- 21 FTIR-8400S using diffuse reflectance accessory

[DRS- 8000A] Solid samples were diluted with KBr before measurement

The spectra were recorded with resolution of 4 cm-1 with 50 accumulations

iv UV spectrophotometer (UV-160 SHAMIDZO JAPAN)

For UV spectrophotometic analysis standard addition method was adopted In

this method the matrix (medium in which the analyte exists) of standard and

unknown match exactly Known amount of spikes was added to known

volume of reaction mixture A calibration plot is obtained that is offset from

zero A linear regression should generate a straight-line equation of (y = mx +

b) where m is the slope and b is intercept The concentration of the unknown

is equal to the value of x and is determined by solving the straight-line

equation for y = 0 yields x = b m as shown in figure 7 The samples were

scanned for λ max The increase in absorbance for added spikes was noted

The calibration plot was obtained by plotting standard solution verses

40

Figure 7 Plot for spiked and normalized absorbance

Figure 8 Plot of Abs Vs COD concentrations (mgL)

41

absorbance Subtracting the absorbance of unknown (amount of product) from

the standard added solution absorbance can normalize absorbance The offset

shows the unknown concentration of the product

v GC (Clarus 500 Perkin Elmer)

The GC was equipped with (FID) and capillary column (Elite-5 L 30m ID

025 DF 025) Nitrogen was used as the carrier gas For injecting samples 10

microl gas tight injection was used Same standard addition method was adopted

The conversion was measured as follows

Ci and Cf are the initial concentration and final concentration respectively

vi Determination of COD

COD was determined by closed reflux colorimetric method according to

which the organic substances are oxidized (digested) by potassium dichromate

K2Cr2O7 at 160degC in a sealed tube When orange colored Cr2O2minus

7 is reduced

green colored Cr3+ is formed which can be detected in a spectrophotometer at

λ = 600 nm The relation between absorbance and COD concentration is

established by calibration with standard solutions of potassium hydrogen

phthalate in the range of COD values between 200 and 1200 mgL as shown

in Fig 8

38 Heterogeneous nature of the catalyst

The heterogeneity of catalytic reaction was confirmed with Alizarin test for Zr+4

ions and potassium iodide test for Pt+4 and Pd+2 ions in the reaction mixture For Zr+4 test

5 ml of reaction mixture was mixed with 5 ml of Alizarin reagent and made the total

volume up to 100 ml by adding 01 N HCl solution No change in color (which was

expected to be red in case of Zr+4 presence) and no absorbance at λ max = 513 nm was

observed For Pt+4 and Pd+2 test 1 ml of 5 KI and 2 ml of reaction mixture was mixed

and made the total volume to 50 ml by adding 01N HCL solution No change in color

(which was to be brownish pink color of PtI6-2 in case of Pt+4 ions presence) and no

absorbance at λ max = 496nm was observed

100() minus

=Ci

CfCiX

42

Chapter 3

References

1 Ilyas M Sadiq M Chem Eng Technol 2007 30 1391

2 Ilyas M Sadiq M Khan I Chin J Catal 2007 28 413

3 Ilyas M Sadiq M Chin J Chem 2008 26 941

4 Ilyas M Sadiq M Catal Lett 2008 (online first) DOI 101007s10562-008-

9750-8

5 Liu H Feng l Zhang X Xue Q J Phys Chem 1995 99 332

6 Li X Xu J Wang F Gao J Zhou L Yang G Catal Lett 2006 108 137

7 Li X Xu J Zhou L Wang F Gao J Chen C Ning J Ma H Catal Lett

2006 110 255

8 Zhao Y Wang G Li W Zhu Z Chemom Intell Lab Sys 2006 82 193

9 Christoskova ST Stoyanova M Water Res 2002 36 2297

43

Chapter 4A

Results and discussion

Reactant Cyclohexanol octanol benzyl alcohol

Catalyst ZrO2

Oxidation of alcohols in solvent free conditions by zirconia catalyst

4A 1 Characterization of catalyst

An important step in the field of heterogeneous catalysis is the characterization of

catalysts The field of surface science of catalysis is helpful to examine the structure and

composition of the catalytically active surface and to correlate this information with

catalytic reaction rates selectivity activity and catalyst lifetime

4A 2 Brunauer-Emmet-Teller method (BET)

Surface area of ZrO2 was dependent on preparation procedure digestion time pH

agitation and concentration of precursor solution and calcination time During this study

we observe fluctuations in the surface area of ZrO2 by applying various conditions

Surface area of ZrO2 was found to depend on calcination temperature Fig 1 shows that at

a higher temperature (1223 K) ZrO2 have a monoclinic geometry and a lower surface area

of 8860m2g while at a lower temperature (723 K) ZrO2 was dominated by a tetragonal

geometry with a high surface area of 17111 m2g

4A 3 X-ray diffraction (XRD)

From powder XRD we obtained diffraction patterns for 723K 1223K-calcined

neat ZrO2 samples which are shown in Fig 2 ZrO2 calcined at 723K is tetragonal while

ZrO2 calcined at1223K is monoclinic Monoclinic ZrO2 shows better activity towards

alcohol oxidation then the tetragonal ZrO2

4A 4 Scanning electron microscopy

The SEM pictures with two different resolutions of the vacuum dried neat ZrO2 material

calcined at 1223 K and 723 K are shown in Fig 3 The morphology shows that both these

44

Figure 1

Brunauer-Emmet-Teller method (BET)

plot for ZrO2 calcined at 1223 and 723 K

Figure 2

XRD for ZrO2 calcined at 1223 and 723 K

Figure 3

SEM for ZrO2 calcined at 1223 K (a1 a2) and

723 K (b1 b2) Resolution for a1 b1 1000 and

a2 b2 2000 at 25 kV

Figure 4

EDX for ZrO2 calcined at before use and

after use

45

samples have the same particle size and shape The difference in the surface area could be

due to the difference in the pore volume of the two samples The total pore volume

calculated from nitrogen adsorption at 77 K is 026 cm3g for the sample calcined at 1223

K and 033 cm3g for the sample calcined at 723 K Elemental analysis results were

obtained for laboratory prepared ZrO2 calcined at 723 and 1223 K which indicate the

presence of a small amount of hafnium (Hf) 2503 wt oxygen and 7070 wt zirconia

reported in Fig4 The test also found trace amounts of chlorine present indicating a

small percentage from starting material is present Elemental analysis for used ZrO2

indicates a small percentage of carbon deposit on the surface which is responsible for

deactivation of catalytic activity of ZrO2

4A 5 Effect of mass transfer

Preliminary experiments were performed using ZrO2 as catalyst for alcohol

oxidation under the solvent free conditions at a high agitation speed of 900 rpm for 24 h

with O2 bubbling through the reaction mixture Analysis of the reaction mixture shows

that benzaldehyde (yield 39) was the only product detected by FID The presence of

oxygen was necessary for the benzyl alcohol oxidation to benzaldehyde No reaction was

observed when no oxygen was bubbled through the reaction mixture or when oxygen was

replaced by nitrogen Similarly no reaction was observed when oxygen was passed

through the reactor above the surface of the reaction mixture This would support the

conclusion of Kluytmans et al [1] that direct contact of gaseous oxygen with catalyst

particles is necessary for the alcohol oxidation over supported platinum catalysts A

similar result was obtained for n-octanol Only cyclohexanol shows some conversion

(~15) in a deoxygenated atmosphere after 24 h For the effective use of the catalyst it

is necessary that the reaction should be carried out in the absence of mass transfer

limitations The effect of the mass transfer on the rate of reaction was determined by

studying the change in conversion at various speeds of agitation from 150 to 1200 rpm

Fig 5 shows that the conversion of alcohol increases with the increase in the speed of

agitation from 150 to 900 rpm The increase in the agitation speed above 900 rpm has no

effect on the conversion indicating a minimum effect of mass transfer resistance at above

900 rpm All the subsequent experiments were performed at 1200 rpm

46

4A 6 Effect of calcination temperature

Table 1 shows the effect of the calcination temperature on the catalytic activity of

ZrO2 The catalytic activity of ZrO2 calcined at 1223 K is higher than ZrO2 calcined at

723 K for the oxidation of alcohols This could be due to the change in the crystal

structure [2 3] Ferino et al [4] also reported that ZrO2 calcined at temperatures above

773 K was dominated by the monoclinic phase whereas that calcined at lower

temperatures was dominated by the tetragonal phase The difference in the catalytic

activity of the tetragonal and monoclinic zirconia-supported catalysts was also reported

by Yori et al [5] Yamasaki et al [6] and Li et al [7]

4A 7 Effect of reaction time

The effect of the reaction time was investigated at 413 K (Fig 6) The conversion

of all the alcohols increases linearly with the reaction time reaches a maximum value

and then remains constant for the remaining period The maximum attainable conversion

of benzyl alcohol (~50) is higher than cyclohexanol (~39) and n-octanol (~38)

Similarly the time required to reach the maximum conversion for benzyl alcohol (~30 h)

is shorter than the time required for cyclohexanol and n-octanol (~40 h) Considering the

establishment of equilibrium between alcohols and their oxidation products the

experimental value of the maximum attainable conversion for benzyl alcohol is much

different from the theoretical values obtained using the standard free energy of formation

(∆Gordmf) values [8] for benzyl alcohol benzaldehyde and H2O or H2O2

Table 1 Effect of calcination temperature on the catalytic

performance of ZrO2 for the liquid-phase oxidation of alcohols

Reaction condition 1200 rpm ZrO2 02 g alcohols 10 ml p(O2) =

101 kPa O2 flow rate 40 mlmin 413 K 24 h ZrO2 was calcined at

1223 K

47

Figure 5

Effect of agitation speed on the catalytic

performance of ZrO2 for the liquid-phase

oxidation of alcohols (1) Benzyl

alcohol (2) Cyclohexanol (3) n-Octanol

(Reaction conditions ZrO2 02 g

alcohols 10 ml p(O2) = 101 kPa O2

flow rate 40 mlmin 413 K 24 h ZrO2

was calcined at 1223 K

Figure 6

Effect of reaction time on the catalytic

performance of ZrO2 for the liquid-

phase oxidation of alcohols

(1) Benzyl alcohol (2) Cyclohexanol

(3) n-Octanol

Figure 7

Effect of O2 partial pressure on the

catalytic performance of ZrO2 for the

liquid-phase oxidation of cyclohexanol at

different temperatures (1) 373 K (2) 383

K (3) 393 K (4) 403 K (5) 413 K

(Reaction condition total flow rate (O2 +

N2) = 40 mlmin)

Figure 8

Plots of 1r vs1pO2 according to LH

kinetic equation for moderate

adsorption

48

4A 8 Effect of oxygen partial pressure

The effect of oxygen partial pressure on the catalytic performance of ZrO2 for the

liquid-phase oxidation of cyclohexanol at different temperatures was investigated Fig 7

shows that the average rate of the cyclohexanol conversion increases with the increase in

the partial pressure of oxygen and temperature Higher conversions are however

accompanied by a small decline (~2) in the selectivity for cyclohexanone The major

side products for cyclohexanol detected at high temperatures are cyclohexene benzene

and phenol Eanche et al [9] observed that the reaction was of zero order at p(O2) ge 100

kPa for benzyl alcohol oxidation to benzaldehyde under solvent free conditions They

used higher oxygen partial pressures (p(O2) ge 100 kPa) This study has been performed in

a lower range of oxygen partial pressure (p(O2) le 101 kPa) Fig7 also shows a zero order

dependence of the rate on oxygen partial pressure at p(O2) ge 76 kPa and 413 K

confirming the observation of Eanche et al [9] The average rates of the oxidation of

alcohols have been calculated from the total conversion achieved in 24 h Comparison of

these average rates with the average rate data for the oxidation of cyclohexanol tabulated

by Mallat et al [10] shows that ZrO2 has a reasonably good catalytic activity for the

alcohol oxidation in the liquid phase

4A 9 Kinetic analysis

The kinetics of a solvent-free liquid phase heterogeneous reaction can be studied

when the mass transfer resistance is eliminated Therefore the effect of agitation was

investigated first Fig 5 shows that the conversion of alcohol increases with increase in

speed of agitation from 150mdash900 rpm which was kept constant after this range till 1200

rpm This means that beyond 900 rpm mass transfer effect is minimum Both the effect of

stirring and the apparent activation energy (ca 654 kJmol-1) show that the reaction is in

the kinetically controlling regime This is a typical slurry reaction having the catalyst in

the solid state and the reactants in liquid phase During the development of mechanistic

interpretations of the catalytic reactions using macroscopic rate equations that find

general acceptance are the Langmuir-Hinshelwood (LH) [11] Eley Rideal mechanism

[12] and Mars-Van Krevelen mechanism [13]

Most of the reactions by heterogeneous

49

catalysis are found to obey the Langmuir Hinshelwood mechanism The data were fitted

to different LH kinetic equations (1)mdash(4)

Non-dissociative adsorption

2

21

O

O

kKpr

Kp=

+ (1)

Dissociative Adsorption

( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)

Where ldquorrdquo is rate of reaction ldquokrdquo is the rate constant and ldquoKrdquo is the adsorption

equilibrium constant

The linear form of equation (1)

2

1 1 1

Or kKp k= + (3)

The data fitted to equation (3) for non-dissociative adsorption shows sharp linearity as

indicated in figure 8 All other forms weak adsorption of oxygen (2Or kKp= ) or the

linear form of equation (2)

( )2

1

2

1 1 1

O

r kk Kp

= + (4)

were not applicable to the data

426 Mechanism of reaction

In the present research work the major products of the dehydrogenation of

alcohols over ZrO2 are ketones aldehydes Increase in rate of formation of desirable

products with increase in pO2 proves that oxidative dehydrogenation is the major

pathway of the reaction as indicated in Fig 7 The formation of cyclohexene in the

cyclohexanol dehydrogenation particularly at lower temperatures supports the

dehydration pathway The formation of phenol and other unknown products particularly

at higher temperatures may be due to inter-conversion among the reaction components

50

The formation of cyclohexene is due to the slight use of the acidic sites of ZrO2 via acid

catalyzed E2 mechanism which is supported by the work reported [14-17]

To check the mechanism of oxidative dehydrogenation of alcohol to corresponding

carbonyl compounds in which the oxygen acts as a receptor for hydrogen methylene blue

was introduced in the reaction mixture and the reaction was run in the absence of oxygen

After 14 h of the reaction duration the blue color of the reaction mixture (due to

methylene blue) disappeared It means that the dye goes over into colorless liquor due to

the extraction of hydrogen from alcohol by the methylene blue This is in excellent

agreement with the work reported [18-20] Methylene blue as a hydrogen receptor was

also verified by Nicoletti et al [21] Fabiana et al[22] have investigated dehydrogenation

of cyclohexanol over bi-metallic RhmdashCu and proposed two different reaction pathways

Dehydration of cyclohexanol to cyclohexene proceeds at the acid sites and then

cyclohexanol moves toward the RhmdashCu sites being dehydrogenated to benzene

simultaneously dehydrogenation occurs over these sites to cyclohexanone or phenol

At a very early stage Heyns et al [23 24] suggested that liquid phase oxidation of

alcohols on metal surfaces proceed via a dehydrogenation mechanism followed by the

oxidation of the adsorbed hydrogen atom with dissociatively adsorbed oxygen This was

supported by kinetic modeling of oxidation experiments [25] and by direct observation of

hydrogen evolving from aldose aqueous solutions in the presence of platinum or rhodium

catalysts [26] A number of different formulae have been proposed to describe the surface

chemistry of the oxidative dehydrogenation mechanism Thus in a study based on the

kinetic modeling of the ethanol oxidation on platinum van den Tillaart et al [27]

proposed that following the first step of abstraction of the hydroxyl hydrogen of ethanol

the ethoxide species CH3CH2Oads

did not dehydrogenate further but reacted with

dissociatively adsorbed oxygen

CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51

In this research work we propose the same mechanism of reaction for the oxidative

dehydrogenation of alcohol to aldehydes ketones over ZrO2

C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)

In the inert atmosphere we propose the following mechanism for dehydrogenation of

cyclohexanol to cyclohexanone which probably follows the dehydrogenation pathway

C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)

The above mechanism proposed in the present research work is in agreement with the

mechanism proposed by Ahmad et al [28] who studied the dehydrogenation and

dehydration of cyclohexanol over CuCrFeO4 and CuCr2O4

We also identified cyclohexene as the side product of the reaction which is less than 1

The mechanism of cyclohexene formation from cyclohexanol also follows the

dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)

In the formation of cyclohexene it was observed that with the increase in partial pressure

of oxygen no increase in the formation of cyclohexene occurred This clearly indicates

that oxygen has no effect on the formation of cyclohexene

52

427 Role of oxygen

Oxygen plays an important role in the oxidation of organic compounds which

was believed to be dissociatively adsorbed on transition metal surfaces [29] Various

forms of oxygen may exist on the surface and in the bulk of oxide catalyst which include

(a) chemisorbed surface oxygen species uncharged and charged (mono-atomic O- andor

molecular) (b) lattice oxygen of the formal charge O2-

According to Haber [30] O2

- and O- being strongly electrophilic reactants attack

the organic molecule in the regions of its high electron density and peroxy and epoxy

complexes formed as a result of such attack are in the unstable conditions of a

heterogeneous catalytic reaction and represent intermediates in the degradation of the

organic molecule letting Haber propose a classification of oxidation reactions into two

groups ldquoelectronic oxidation proceeding through the activation of oxygen and

nucleophilic oxidation in which activation of the organic molecule is the first step

followed by consecutive steps of nucleophilic oxygen addition and hydrogen abstraction

[31] The simplest view of a metal oxide is that it will have two distinct types of lattice

points a positively charged site associated with the metal cation and a negatively charged

site associated with the oxygen anion However many of the oxides of major importance

as redox catalysts have metal ions with anionic oxygen bound to them through bonds of a

coordinative nature Oxygen chemisorption is of most interest to consider that how the

bond rupturing occurs in O2 with electron acquisition to produce O2- As a gas phase

molecule oxygen ldquoO2rdquo has three pairs of electrons in the bonding outer orbital and two

unpaired electrons in two anti-bonding π-orbitals producing a net double bond In the

process of its chemisorption on an oxide surface the O2 molecule is initially attached to a

reduced metal site by coordinative bonding As a result there is a transfer of electron

density towards O2 which enters the π-orbital and thus weakens the OmdashO bond

Cooperative action [32] involving more than one reduction site may then affect the

overall dissociative conversion for which the lowest energy pathway is thought to

involve a succession of steps as

O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53

This gives the basic description of the effective chemisorption mechanism of oxygen as

involved in many selective oxidation processes It depends upon the relatively easy

release of electrons associated with the increase of oxidation state of the associated metal

center Two general mechanisms can be investigated for the oxidation of molecule ldquoXrdquo

on the oxide surface

X(ads) + O(lattice) rarr Product + Lattice vacancy

12O2(g) + Lattice vacancy rarr O (lattice)

ie X(ads) reacts with oxygen from the oxide lattice and the resultant vacancy is occupied

afterward using gas phase oxygen The general action represented by this mechanism is

referred to as Mars-Van Krevelen mechanism [33-35] Some catalytic processes at solid

surface sites which are governed by the rates of reactant adsorption or less commonly on

product desorption Hence the initial rate law took the form of Rate = k (Po2)12 which

suggests that the limiting role is played by the dissociative chemisorption of the oxygen

on the sites which are independent of those on which the reactant adsorbs As

represented earlier that

12 O2 (gas) rarr O (lattice)

The rate of this adsorption process would be expected to depend upon (pO2)12

on the

basis of mass action principle In Mar-van Krevelen mechanism the organic molecule

Xads reacts with the oxygen from an oxide lattice preceding the rate determining

replenishment of the resultant vacancy with oxygen derived from the gas phase The final

step in the overall mechanism is the oxidation of the partially reduced surface by O2 as

obvious in the oxygen chemisorption that both reductive and oxidative actions take place

on the solid surfaces The kinetic expression outlined was derived as

p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred

represent the rate constants for oxidation of the oxide catalysts and

n =1 represents associative and n =12 as dissociative oxygen adsorption

54

Chapter 4A

References

1 Kluytmans J H J Markusse A P Kuster B F M Marin G B Schouten J

C Catal Today 2000 57 143


3 Liu H Feng L Zhang X Xue Q J Phys Chem 1995 99 332

4 Ferino I Casula M F Corrias A Cutrufello M Monaci G R

Paschina G Phys Chem Chem Phys 2000 2 1847

5 Yori J C Parera J M Catal Lett 2000 65 205

6 Yamasaki M Habazaki H Asami K Izumiya K Hashimoto K Catal

Commun 2006 7 24

7 Li X Nagaoka K Simon L J Olindo R Lercher J A Catal Lett 2007

113 34

8 Dean A J Langersquos Handbook of Chemistry 13th Ed New York McGraw Hill

1987 9ndash72

9 Enache D I Edwards J K Landon P Espiru B S Carley A F Herzing

A H Watanabe M Kiely C J Knight D W Hutchings G J Science 2006

311 362


11 Bonzel H P Ku R Surf Sci 1972 33 91

12 Somorjai G A Chemistry in Two Dimensions Cornell University Press Ithaca

New York 1981

13 Xu X De Almeida C P Antal M J Jr Ind Eng Chem Res 1991 30 1448

14 Narayan R Antal M J Jr J Am Chem Soc 1990 112 1927

15 Xu X De Almedia C Antal J J Jr J Supercrit Fluids 1990 3 228

16 West M A B Gray M R Can J Chem Eng 1987 65 645

17 Wieland H A Ber Deut Chem Ges 1912 45 2606

18 Wieland H A Ber Duet Chem Ges 1913 46 3327


20 Nicoletti J W Whitesides G M J Phys Chem 1989 93 759

55

21 Fabiana M T Appl Catal A General 1997 163 153

22 Heyns K Paulsen H Angew Chem 1957 69 600

23 Heyns K Paulsen H Ruediger G Weyer J F Chem Forsch 1969 11 285

24 de Wilt H G J Van der Baan H S Ind Eng Chem Prod Res Dev 1972 11

374

25 de Wit G de Vlieger J J Kock-van Dalen A C Heus R Laroy R van

Hengstum A J Kieboom A P G Van Bekkum H Carbohydr Res 1981 91

125

26 Van Den Tillaart J A A Kuster B F M Marin G B Appl Catal A General

1994 120 127

27 Ahmad A Oak S C Darshane V S Bull Chem Soc Jpn 1995 68 3651

28 Gates B C Catalytic Chemistry John Wiley and Sons Inc 1992 p 117

29 Bielanski A Haber J Oxygen in Catalysis Marcel Dekker New York 1991 p

132

30 Haber J Z Chem 1973 13 241

31 Brazdil J F In Characterization of Catalytic Materials Ed Wachs I E Butter

Worth-Heinmann Inc USA 1992 96 p 10353

32 Mars P Krevelen D W Chem Eng Sci 1954 3 (Supp) 41

33 Sivakumar T Shanthi K Sivasankar B Hung J Ind Chem 1998 26 97

34 Saito Y Yamashita M Ichinohe Y In Catalytic Science amp Technology Vol

1 Eds Yashida S Takezawa N Ono T Kodansha Tokyo 1991 p 102

35 Sing KSW Pure Appl Chem 1982 54 2201

56

Chapter 4B


Reactant Alcohol in aqueous medium

Catalyst ZrO2

Oxidation of alcohols in aqueous medium by zirconia catalyst

4B 1 Characterization of catalyst

ZrO2 was well characterized by using different modern techniques like FT-IR

SEM and EDX FT-IR spectra of fresh and used ZrO2 are reported in Fig 1 FT-IR

spectra for fresh ZrO2 show a small peak at 2345 cm-1 as we used this ZrO2 for further

reactions the peak become sharper and sharper as shown in the Fig1 This peak is

probably due to asymmetric stretching of CO2 This was predicted at 2640 cm-1 but

observed at 2345 cm-1 Davies et al [1] have reported that the sample derived from

alkoxide precursors FT-IR spectra always showed a very intense and sharp band at 2340

cm-1 This band was assigned to CO2 trapped inside the bulk structure of the oxide which

is in rough agreement with our results Similar results were obtained from the EDX

elemental analysis The carbon content increases as the use of ZrO2 increases as reported

in Fig 2 These two findings are pointing to complete oxidation of alcohol SEM images

of ZrO2 at different resolution were recoded shown in Fig3 SEM image show that ZrO2

has smooth morphology

4B 2 Oxidation of benzyl alcohols in Aqueous Medium

57

Figure 1

FT-IR spectra for (Fresh 1st time used 2nd

time used 3rd time used and 4th time used

ZrO2)

Figure 2

EDX for (Fresh 1st time used 2nd time used

3rd time used and 4th time used ZrO2)

58

Figure 3

SEM images of ZrO2 at different resolutions (1000 2000 3000 and 6000)

59

Overall oxidation reaction of benzyl alcohol shows that the major products are

benzaldehyde and benzoic acid The kinetic curve illustrating changes in the substrate

and oxidation products during the reaction are shown in Fig4 This reveals that the

oxidation of benzyl alcohol proceeds as a consecutive reaction reported widely [2] which

are also supported by UV spectra represented in Fig 5 An isobestic point is evident

which points out to the formation of a benzaldehyde which is later oxidized to benzoic

acid Calculation based on these data indicates that an oxidation of benzyl alcohol

proceeds as a first order reaction with respect to the benzyl alcohol oxidation

4B 3 Effect of Different Parameters

Data concerning the impact of different reaction parameters on rate of reaction

were discuss in detail Fig 6a and 6b presents the effect of concentration studies at

different temperature (303-333K) Figures 6a 6b and 7 reveals that the conversion is

dependent on concentration and temperature as well The rate decreases with increase in

concentration (because availability of active sites decreases with increase in

concentration of the substrate solution) while rate of reaction increases with increase in

temperature Activation energy was calculated (~ 86 kJ mole-1) by applying Arrhenius

equation [3] Activation energy and agitation effect supports the absence of mass transfer

resistance Bavykin et al [4] have reported a value of 79 kJ mole-1 for apparent activation

energy in a purely kinetic regime for ruthenium catalyzed oxidation of benzyl alcohol

They have reported a value of 61 kJ mole-1 for a combination of kinetic and mass transfer

regime The partial pressure of oxygen dramatically affects the rate of reaction Fig 8

shows that the conversion increases linearly with increase of partial pressure of

oxygen The selectivity to required product increases with increase in the partial pressure

of oxygen Fig 9 shows that the increase in the agitation above the 900 rpm did not affect

the rate of reaction The rate increases from 150-900 rpm linearly but after that became

flat which is the region of interest where the mass transfer resistance is minimum or

absent [5] The catalyst reused several time after simple drying in oven It was observed

that the activity of catalyst remained unchanged after many times used as shown in Fig

10

60

Figure 6a and 6b

Plot of Concentration Vs Conversion

Figure 4

Concentration change of benzyl alcohol

and reaction products during oxidation

process at lower concentration 5gL Reaction conditions catalyst (02 g) substrate solution (10 mL) pO2 (101 kPa) flow rate (40

mLmin) temperature (333K) stirring (900 rpm)

time 6 hours

Figure 5

UV spectrum i to v (225nm)

corresponding to benzoic acid and

a to e (244) corresponding to

benzaldehyde Reaction conditions catalyst (02 g)

substrate solution (5gL 10 mL) pO2 (101

kPa) flow rate (40 mLmin) temperature (333K) stirring (900 rpm)

61

Figure 7

Plot of temperature Vs Conversion Reaction conditions catalyst (02 g) substrate solution (20gL 10 mL) pO2 (101 kPa) stirring (900 rpm) time

(6 hrs)

Figure 11 Plot of agitation Vs

Conversion

Figure 9

Effect of agitation speed on benzyl

alcohol oxidation catalyzed by ZrO2 at

333K Reaction conditions catalyst (02 g) substrate

solution (20gL 10 mL) pO2 (101 kPa) time (6

hrs)

Figure 8

Plot of pO2 Vs Conversion Reaction conditions catalyst (02 g) substrate solution (10gL 10 mL) temperature (333K)

stirring (900 rpm) time (6 hrs)

Figure 10

Reuse of catalyst several times Reaction conditions catalyst (02 g) substrate solution

(10gL 10 mL) pO2 (101 kPa) flow rate (40 mLmin) temperature (333K) stirring (900 rpm) time (6 hrs)

62

Chapter 4B

References

1 Davies L E Bonini N A Locatelli S Gonzo EE Latin American Applied

Research 2005 35 23-28

2 Christoskova St Stoyanova Water Res 2002 36 2297-2303


4 Bavykin D V Lapkin A A Kolaczkowski S T Plucinski P K App Catal

A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2

Oxidation of toluene in solvent free conditions by PtZrO2

4C 1 Catalyst characterization

BET surface area was 65 and 183 m2 g-1 for ZrO2 and PtZrO2 respectively Fig 1

shows SEM images which reveal that the PtZrO2 has smaller particle size than that of

ZrO2 which may be due to further temperature treatment or reduction process The high

surface area of PtZrO2 in comparison to ZrO2 could be due to its smaller particle size

Fig 2a b shows the diffraction pattern for uncalcined ZrO2 and ZrO2 calcined at 950 degC

Diffraction pattern for ZrO2 calcined at 950 degC was dominated by monoclinic phase

(major peaks appear at 2θ = 2818deg and 3138deg) [1ndash3] Fig 2c d shows XRD patterns for

a PtZrO2 calcined at 750 degC both before and after reduction in H2 The figure revealed

that PtZrO2 calcined at 750 degC exhibited both the tetragonal phase (major peak appears

at 2θ = 3094deg) and monoclinic phase (major peaks appears 2θ = 2818deg and 3138deg) The

reflection was observed for Pt at 2θ = 3979deg which was not fully resolved due to small

content of Pt (~1 wt) as also concluded by Perez- Hernandez et al [4] The reduction

processing of PtZrO2 affects crystallization and phase transition resulting in certain

fraction of tetragonal ZrO2 transferred to monoclinic ZrO2 as also reported elsewhere [5]

However the XRD pattern of PtZrO2 calcined at 950 degC (Fig 2e f) did not show any

change before and after reduction in H2 and were fully dominated by monoclinic phase

However a fraction of tetragonal zirconia was present as reported by Liu et al [6]

4C 2 Catalytic activity

In this work we first studied toluene oxidation at various temperatures (60ndash90degC)

with oxygen or air passing through the reaction mixture (10 mL of toluene and 200 mg of

64

Figure 1

SEM images of ZrO2 (calcined at 950 degC) and PtZrO2 (calcined at 950 degC and reduced in H2)

Figure 2

XRD pattern of ZrO2 and PtZrO2 (a) ZrO2 (uncalcined) (b) ZrO2 (calcined at 950 degC) (c) PtZrO2

(unreduced calcined at 750 degC) and (d) PtZrO2 (calcined at 750 degC and reduced in H2) (e) PtZrO2

(unreduced calcined at 950 degC) and (f) PtZrO2 (calcined at 950 degC and reduced in H2)

65

1(wt) PtZrO2) with continuous stirring (900 rpm) The flow rate of oxygen and air

was kept constant at 40 mLmin Table 1 present these results The known products of the

reaction were benzyl alcohol benzaldehyde and benzoic acid The mass balance of the

reaction showed some loss of toluene (~1) Conversion rises with temperature from

96 to 372 The selectivity for benzyl alcohol is higher than benzoic acid at 60 degC At

70 degC and above the reaction is more selective for benzoic acid formation 70 degC and

above The reaction is highly selective for benzoic acid formation (gt70) at 90degC

Reaction can also be performed in air where 188 conversion is achieved at 90 degC with

25 selectivity for benzyl alcohol 165 for benzaldehyde and 516 for benzoic acid

Comparison of these results with other solvent free systems shows that PtZrO2 is very

effective catalyst for toluene oxidation Higher conversions are achieved at considerably

lower temperatures and pressure than other solvent free systems [7-12] The catalyst is

used without any additive or promoter The commercial catalyst (Envirocat EPAC)

requires trimethylacetic acid as promoter with a 11 ratio of catalyst and promoter [7]

The turnover frequency (TOF) was calculated as the molar ratio of toluene converted to

the platinum content of the catalyst per unit time (h-1) TOF values are very high even at

the lowest temperature of 60degC

4C 3 Time profile study

The time profile of the reaction is shown in Fig 3 where a linear increase in

conversion is observed with the passage of time An induction period of 30 min is

required for the products to appear At the lowest conversion (lt2) the reaction is 100

selective for benzyl alcohol (Fig 4) Benzyl alcohol is the main product until the

conversion reaches ~14 Increase in conversion is accompanied by increase in the

selectivity for benzoic acid Selectivity for benzaldehyde (~ 20) is almost unaffected by

increase in conversion This reaction was studied only for 3 h The reaction mixture

becomes saturated with benzoic acid which sublimes and sticks to the walls of the

reactor

66

Table 1

Oxidation of toluene at various temperatures

Reaction conditions

Catalyst (02 g) toluene (10 mL) pO2 (101 kPa) flow rate of O2Air (40 mLmin) a Toluene lost (mole

()) not accounted for bTOF (turnover frequency) molar ratio of converted toluene to the platinum content

of the catalyst per unit time (h-1)

Figure 3

Time profile for the oxidation of toluene

Reaction conditions

Catalyst (02 g) toluene (10 mL) pO2 (101 kPa)

flow rate (40 mLmin) temperature (90 degC) stirring

(900 rpm)

Figure 4

Selectivity of toluene oxidation at various

conversions

Reaction conditions



(900 rpm)

67

4C 4 Effect of oxygen flow rate

Effect of the flow rate of oxygen on toluene conversion was also studied Fig 5

shows this effect It can be seen that with increase in the flow rate both toluene

conversion and selectivity for benzoic acid increases Selectivity for benzyl alcohol and

benzaldehyde decreases with increase in the flow rate At the oxygen flow rate of 70

mLmin the selectivity for benzyl alcohol becomes ~ 0 and for benzyldehyde ~ 4 This

shows that the rate of reaction and selectivity depends upon the rate of supply of oxygen

to the reaction system

4C 5 Appearance of trans-stilbene and methyl biphenyl carboxylic acid

Toluene oxidation was also studied for the longer time of 7 h In this case 20 mL

of toluene and 400 mg of catalyst (1 PtZrO2) was taken and the reaction was

conducted at 90 degC as described earlier After 7 h the reaction mixture was converted to a

solid apparently having no liquid and therefore the reaction was stopped The reaction

mixture was cooled to room temperature and more toluene was added to dissolve the

solid and then filtered to recover the catalyst Excess toluene was recovered by

distillation at lower temperature and pressure until a concentrated suspension was

obtained This was cooled down to room temperature filtered and washed with a little

toluene and sucked dry to recover the solid The solid thus obtained was 112 g

Preparative TLC analysis showed that the solid mixture was composed of five

substances These were identified as benzaldehyde (yield mol 22) benzoic acid

(296) benzyl benzoate (34) trans-stilbene (53) and 4-methyl-2-

biphenylcarboxylic acid (108) The rest (~ 4) could be identified as tar due to its

black color Fig 6 shows the conversion of toluene and the yield (mol ) of these

products Trans-stilbene and methyl biphenyl carboxylic acid were identified by their

melting point and UVndashVisible and IR spectra The Diffuse Reflectance FTIR spectra

(DRIFT) of trans-stilbene (both of the standard and experimental product) is given in Fig

7 The oxidative coupling of toluene to produce trans-stilbene has been reported widely

[13ndash17] Kai et al [17] have reported the formation of stilbene and bibenzyl from the

oxidative coupling of toluene catalyzed by PbO However the reaction was conducted at

68

Figure 7

Diffuse reflectance FTIR (DRIFT) spectra of trans-stilbene

(a) standard and (b) isolated product (mp = 122 degC)

Figure 5

Effect of flow rate of oxygen on the

oxidation of toluene

Reaction conditions

Catalyst (04 g) toluene (20 mL) pO2 (101

kPa) temperature (90degC) stirring (900

rpm) time (3 h)

Figure 6

Conversion of toluene after 7 h of reaction

TL toluene BzH benzaldehyde

BzOOH benzoic acid BzB benzyl

benzoate t-ST trans-stilbene MBPA

methyl biphenyl carboxylic acid reaction

Conditions toluene (20 mL) catalyst (400

mg) pO2 (101 kPa) flow rate (40 mLmin)

agitation (900 rpm) temperature (90degC)

69

a higher temperature (525ndash570 degC) in the vapor phase Daito et al [18] have patented a

process for the recovery of benzyl benzoate by distilling the residue remaining after

removal of un-reacted toluene and benzoic acid from a reaction mixture produced by the

oxidation of toluene by molecular oxygen in the presence of a metal catalyst Beside the

main product benzoic acid they have also given a list of [6] by products Most of these

byproducts are due to the oxidative couplingoxidative dehydrocoupling of toluene

Methyl biphenyl carboxylic acid (mp 144ndash146 degC) is one of these byproducts identified

in the present study Besides these by products they have also recovered the intermediate

products in toluene oxidation benzaldehyde and benzyl alcohol and esters formed by

esterification of benzyl alcohol with a variety of carboxylic acids inside the reactor The

absence of benzyl alcohol (Figs 3 6) could be due to its esterification with benzoic acid

to form benzyl benzoate

70

Chapter 4C

References

1 Souza L D Suchopar A Zhu K Balyozova D Devadas M Richards R

M Microporous Mesoporous Mater 2006 88 22

2 Ferino I Casula M F Corrias A Cutrufello M Monaci G R Paschina G

Phys Chem Chem Phys 2000 2 1847

3 Ding J Zhao N Shi C Du X Li J J Alloys Compd 2006 425 390

4 Perez-Hernandwz R Aguilar F Gomez-Cortes A Diaz G Catal Today

2005 107ndash108 175

5 Zhan Y Cai G Xiao Y Wei K Cen T Zhang H Zheng Q Guang Pu

Xue Yu Guang Pu Fen Xi 2004 24 914


7 Bastock T E Clark J H Martin K Trentbirth B W Green Chem 2002 4

615

8 Subrahmanyama C H Louisb B Viswanathana B Renkenb A Varadarajan

T K Appl Catal A Gen 2005 282 67

9 Raja R Thomas J M Dreyerd V Catal Lett 2006 110 179

10 Thomas J M Raja R Catal Today 2006 117 22

11 Li X Xu J Wang F Gao J Zhou L Yang G Catal Lett 2006108 137


2006 110 255

13 Montgomery P D Moore R N Knox W K US Patent 3965206 1976

14 Lee T P US Patent 4091044 1978

15 Williamson A N Tremont S J Solodar A J US Patent 4255604 4268704

4278824 1981

16 Hupp S S Swift H E Ind Eng Chem Prod Res Dev 1979 18117

17 Kai T Nomoto R Takahashi T Catal Lett 2002 84 75

18 Daito N Ueda S Akamine R Horibe K Sakura K US Patent 6491795

2002

71

Chapter 4D


Reactant Benzyl alcohol in n- haptane

Catalyst ZrO2 Pt ZrO2

Oxidation of benzyl alcohol by zirconia supported platinum catalyst

4D1 Characterization catalyst

BET surface area of the catalyst was determined using a Quanta chrome (Nova

2200e) Surface area ampPore size analyzer Samples were degassed at 110 0C for 2 hours

prior to determination The BET surface area determined was 36 and 48 m2g-1 for ZrO2

and 1 wt PtZrO2 respectively XRD analyses were performed on a JEOL (JDX-3532)

X-Ray Diffractometer using CuKα radiation with a tube voltage of 40 KV and 20mA

current Diffractograms are given in figure 1 The diffraction pattern is dominated by

monoclinic phase [1] There is no difference in the diffraction pattern of ZrO2 and 1

PtZrO2 Similarly we did not find any difference in the diffraction pattern of fresh and

used catalysts

4D2 Oxidation of benzyl alcohol

Preliminary experiments were performed using ZrO2 and PtZrO2 as catalysts for

oxidation of benzyl alcohol in the presence of one atmosphere of oxygen at 90 ˚C using

n-heptane as solvent Table 1 shows these results Almost complete conversion (gt 99 )

was observed in 3 hours with 1 PtZrO2 catalyst followed by 05 PtZrO2 01

PtZrO2 and pure ZrO2 respectively The turn over frequency was calculated as molar

ratio of benzyl alcohol converted to the platinum content of catalyst [2] TOF values for

the enhancement and conversion are shown in (Table 1) The TOF values are 283h 74h

and 46h for 01 05 and 1 platinum content of the catalyst respectively A

comparison of the TOF values with those reported in the literature [2 11] for benzyl

alcohol shows that PtZrO2 is among the most active catalyst

72

All the catalysts produced only benzaldehyde with no further oxidation to benzoic

acid as detected by FID and UV-VIS spectroscopy Selectivity to benzaldehyde was

always 100 in all these catalytic systems Opre et al [10-11] Mori et al [13] and

Makwana et al [15] have also observed 100 selectivity for benzaldehyde using

RuHydroxyapatite Pd Hydroxyapatite and MnO2 as catalysts respectively in the

presence of one atmosphere of molecular oxygen in the same temperature range The

presence of oxygen was necessary for benzyl alcohol oxidation to benzaldehyde No

reaction was observed when oxygen was not bubbled through the reaction mixture or

when oxygen was replaced by nitrogen Similarly no reaction was observed in the

presence of oxygen above the surface of the reaction mixture This would support the

conclusion [5] that direct contact of gaseous oxygen with the catalyst particles is

necessary for the reaction

These preliminary investigations showed that

i PtZrO2 is an effective catalyst for the selective oxidation of benzyl alcohol to

benzaldehyde

ii Oxygen contact with the catalyst particles is required as no reaction takes place

without bubbling of O2 through the reaction mixture

4D21 Leaching of the catalyst

Leaching of the catalyst to the solvent is a major problem in the liquid phase

oxidation with solid catalyst To test leaching of catalyst the following experiment was

performed first the solvent (10 mL of n-heptane) and the catalyst (02 gram of PtZrO2)

were mixed and stirred for 3 hours at 90 ˚C with the reflux condenser to prevent loss of

solvent Secondly the catalyst was filtered and removed and the reactant (2 m mole of

benzyl alcohol) was added to the filtrate Finally oxygen at a flow rate of 40 mLminute

was introduced in the reaction system After 3 hours no product was detected by FID

Furthermore chemical tests [18] of the filtrate obtained do not show the presence of

platinum or zirconium ions

73

Figure 1

XRD spectra of ZrO2 and 1 PtZrO2

Figure 2

Effect of mass transfer on benzyl

alcohol oxidation catalyzed by

1PtZrO2 Catalyst (02g) benzyl

alcohol (2 mmole) n-heptane (10

mL) temperature (90 ordmC) O2 (760

torr flow rate 40 mLMin) stirring

rate (900rpm) time (1hr)

Figure 3

Arrhenius plot for benzyl alcohol

oxidation Reaction conditions

Catalyst (02g) benzyl alcohol (2

mmole) n-heptane (10 mL)

temperature (90 ordmC) O2 (760 torr

flow rate 40 mLMin) stirring rate

(900rpm) time (1hr)

74

4D22 Effect of Mass Transfer

The process is a typical slurry-phase reaction having one liquid reactant a solid

catalyst and one gaseous reactant The effect of mass transfer on the rate of reaction was

determined by studying the change in conversion at various speeds of agitation (Figure 2)

the conversion increases in the initial stages and becomes constant at the stirring speed of

900 rpm and above showing that conversion is independent of stirring This is the region

of interest and all further studies were performed at a stirring rate of 900 rpm or above

4D23 Temperature Effect

Effect of temperature on the conversion was studied in the range of 60-90 ˚C

(figure 3) The Arrhenius equation was applied to conversion obtained after one hour

The apparent activation energy is ~ 778 kJ mole-1 Bavykin et al [12] have reported a

value of 79 kJmole-1 for apparent activation energy in a purely kinetic regime for

ruthenium-catalyzed oxidation of benzyl alcohol They have reported a value of 61

kJmole-1 for a combination of kinetic and mass transfer regime The value of activation

energy in the present case shows that in these conditions the reaction is free of mass

transfer limitation

4D24 Solvent Effect

Comparison of the activity of PtZrO2 for benzyl alcohol oxidation was made in

various other solvents (Table 2) The catalyst was active when toluene was used as

solvent However it was 100 selective for benzoic acid formation with a maximum

yield of 34 (based upon the initial concentration of benzyl alcohol) in 3 hours

However the mass balance of the reaction based upon the amount of benzyl alcohol and

benzaldehyde in the final reaction mixture shows that a considerable amount of benzoic

acid would have come from oxidation of the solvent Benzene and n-octane were also

used as solvent where a 17 and 43 yield of benzaldehyde was observed in 25 hours

75

4D25 Time course of the reaction

The time course study for the oxidation of the reaction was monitored

periodically This investigation was carried out at 90˚C by suspending 200 mg of catalyst

in 10 mL of n-heptane 2 m mole of benzyl alcohol and passing oxygen through the

reaction mixture with a flow rate of 40 mLmin-1 at one atmospheric pressure Figure 4

shows an induction period of about 30 minutes With the increase in reaction time

benzaldehyde formation increases linearly reaching a conversion of gt99 after 150

minutes Mori et al [13] have also observed an induction period of 10 minutes for the

oxidation of 1- phenyl ethanol catalyzed by supported Pd catalyst

The derivative at any point (after 30minutes) on the curve (figure 6) gives the

rate The design equation for an isothermal well-mixed batch reactor is [14]

Rate = -dCdt

where C is the concentration of the reactant at time t

4D26 Reaction Kinetics Analysis

Both the effect of stirring and the apparent activation energy show that the

reaction is taking place in the kinetically controlled regime This is a typical slurry

reaction having catalyst in the solid state and reactants in liquid and gas phase

Following the approach of Makwana et al [15] reaction kinetics analyses were

performed by fitting the experimental data to one of the three possible mechanisms of

heterogeneous catalytic oxidations

i The Eley-Rideal mechanism (E-R)

ii The Mars-van Krevelen mechanism (M-K) or

iii The Langmuir-Hinshelwood mechanism (L-H)

The E-R mechanism requires one of the reactants to be in the gas phase Makwana et al

[15] did not consider the application of this mechanism as they were convinced that the

gas phase oxygen is not the reactive species in the catalytic oxidation of benzyl alcohol to

benzaldehyde by (OMS-2) type manganese oxide in toluene

However in the present case no reaction takes place when oxygen is passed

through the reactor above the surface of the liquid reaction mixture The reaction takes

place only when oxygen is bubbled through the liquid phase It is an indication that more

76

Table 2 Catalytic oxidation of benzyl alcohol

with molecular oxygen effect of solvent

Figure 4

Time profile for the oxidation of

benzyl alcohol Reaction conditions


mmole) solvent (10 mL) temperature

(90 ordmC) O2 (760 torr flow rate 40

mLMin) stirring rate (900rpm)

Reaction conditions

Catalyst (02g) benzyl alcohol (2 mmole)

solvent (10 mL) temperature (90 ordmC) O2 (760

torr flow rate 40 mLMin) stirring rate

(900rpm)

Figure 5

Non Linear Least square fit for Eley-

Rideal Model according to equation (2)

Figure 6

Non Linear Least square fit for Mars-van

Krevelen Model according to equation (4)

77

probably dissolved oxygen is not an effective oxidant in this case Replacing oxygen by

nitrogen did not give any product Kluytmana et al [5] has reported similar observations

Therefore the applicability of E-R mechanism was also explored in the present case The

E-R rate law can be derived from the reaction of gas phase O2 with adsorbed benzyl

alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]

Where k is the rate coefficient and K is the adsorption equilibrium constant for benzyl

alcohol

It is to be mentioned that for gas phase oxidation reactions the E-R

mechanism envisage reaction between adsorbed oxygen with hydrocarbon molecules

from the gas phase However in the present case since benzyl alcohol is in the liquid

phase in contact with the catalyst and therefore it is considered to be pre-adsorbed at the

surface

In the case of constant O2 pressure equation 1 can be transformed by lumping together all

the constants to yield

BzOHb

BzOHaRate

+=

1 (2)

The M-K mechanism envisages oxidation of the substrate molecules by the lattice

oxygen followed by the re-oxidation of the reduced catalyst by molecular oxygen

Following the approach of Makwana et al [15] the rate expression for M-K mechanism

can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)

Where 1k and 2k are the rate constants for oxidation of the substrate and the surface

respectively and (= 05) is the stoichiometric coefficient for O2 For a constant O2

pressure the equation was transformed to

BzOHcb

BzOHaRate

+= (4)

78

The Lndash H mechanism involves adsorption of the reacting species (benzyl alcohol and

oxygen) on active sites at the surface followed by an irreversible rate-determining

surface reaction to give products The Langmuir-Hinshelwood rate law can be given as

1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)

Where k is the rate coefficient and K1 and K2 are the adsorption equilibrium constants for

benzyl alcohol an O2 respectively The value of n can be taken 1or 05 for molecular or

dissociative adsorption of oxygen respectively

Again for a constant O2 pressure it can be transformed to

2BzOHcb

BzOHaRate

+= (6)

The rate data obtained from the time course study (figure 4) was subjected to

kinetic analysis using a nonlinear regression analysis according to the above-mentioned

three models Figures 5 and 6 show the models fit as compared to actual experimental

data for E-R and M-K according to equation 2 and 4 respectively Both these models

show a similar pattern with a similar value (R2 =0827) for the regression coefficient In

comparison to this figure 7 show the L-H model fit to the experimental data The L-H

Model (R2 = 0986) has a better fit to the data when subjected to nonlinear least square

fitting Another way to test these models is the traditional linear forms of the above-

mentioned models The linear forms are given by using equation 24 and 6 respectively

as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate

BzOH+= (8) [M-K model]

and

BzOH

a

c

a

b

Rate

BzOH+= (9) [L-H-model]

It is clear that the linear forms of E-R and M-K models are similar to each other Figure 8

shows the fit of the data according to equation 7 and 8 with R2 = 0967 The linear form

79

Figure 7

Non Linear Least square fit for Langmuir-

Hinshelwood Model according to equation

(6)

Figure 8

Linear fit for Eley-Rideasl and Mars van Krevelen

Model according to equation (7 and 8)

Figure 9

Linear Fit for Langmuir-Hinshelwood

Model according to equation (9)

Figure 10

Time profile for benzyl alcohol conversion at

various oxygen partial pressures Reaction

conditions Catalyst (04g) benzyl alcohol (4

mmole) n-heptane (20 mL) temperature (90

ordmC) O2 (flow rate 40 mLMin) stirring (900

rmp)

80

of L-H model is shown in figure 9 It has a better fit (R2 = 0997) than the M-K and E-R

models Keeping aside the comparison of correlation coefficients a simple inspection

also shows that figure 8 is curved and forcing a straight line through these points is not

appropriate Therefore it is concluded that the Langmuir-Hinshelwood model has a much

better fit than the other two models Furthermore it is also obvious that these analyses are

unable to differentiate between Mars-van Kerevelen and Eley-Rideal mechanism (Eqs

7 8 and 10)

4D27 Effect of Oxygen Partial Pressure

The effect of oxygen partial pressure was studied in the lower range of 95-760 torr with a

constant initial concentration of 02 M benzyl alcohol concentration (figure 10)

Adsorption of oxygen is generally considered to be dissociative rather than molecular in

nature However figure 11 shows a linear dependence of the initial rates on oxygen

partial pressure with a regression coefficient (R2 = 0998) This could be due to the

molecular adsorption of oxygen according to equation 5

1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)

Where due to the low pressure of O2 the term 22 OK could be neglected in the

denominator to transform equation (10)

1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)

which at constant benzyl alcohol concentration is reduced to

2Rate a O= (12)

Where a is a new constant having lumped together all the constants

In contrast to this the rate equation according to L-H mechanism for dissociative

adsorption of oxygen could be represented by

81

22

2

Ocb

OaRate

+= (13)

and the linear form would be

2

42

Oa

c

a

b

Rate

O+= (14)

Fitting of the data obtained for the dependence of initial rates on oxygen partial pressure

according to equation obtained from the linear forms of E-R (equation similar to 7) M-K

(equation similar to 8) and L-H model (equation 14) was not successful Therefore the

molecular adsorption of oxygen is favored in comparison to dissociative adsorption of

oxygen According to Engel et al [19] the existence of adsorbed O2 molecules on Pt

surface has been established experimentally Furthermore they have argued that the

molecular species is the ldquoprecursorrdquo for chemisorbed atomic species ldquoOadrdquo which is

considered to be involved in the catalytic reaction Since the steady state concentration of

O2ads at reaction temperatures will be negligibly small and therefore proportional to the

O2 partial pressure the kinetics of the reaction sequence

can be formulated as

gads

ad OkOkdt

Od22 == minus

(15)

If the rate of benzyl alcohol conversion is directly proportional to [Oad] then equation

(15) is similar to equation (12)

From the above analysis it could concluded that

a) The Langmuir-Hinshelwood mechanism is favored as compared to Eley-Rideal

and Mars-van Krevelen mechanisms

b) Adsorption of oxygen is molecular rather than dissoiciative in nature However

molecular adsorption of oxygen could be a precursor for chemisorbed atomic

oxygen (dissociative adsorption of oxygen)

It has been suggested that H2O2 could be an intermediate in alcohol oxidation on

Pdhydroxyapatite [13] which is produced by the reaction of the Pd-hydride species with

82

Figure 11

Effect of oxygen partial pressure on the initial

rates for benzyl alcohol oxidation

Conditions Catalyst (04g) benzyl alcohol (4



rmp)

Figure 12

Decomposition of hydrogen peroxide on

PtZrO2

Conditions catalyst (20 mg) hydrogen

peroxide (0067 M) volume 20 mL

temperature (0 ordmC) stirring (900 rmp)

83

molecular oxygen Hydrogen peroxide is immediately decomposed to H2O and O2 on the

catalyst surface Production of H2O2 has also been suggested during alcohol oxidation

on MnO2 [15] and PtO2 [16] Both Platinum [9] and MnO2 [17] have been reported to be

very active catalysts for H2O2 decomposition The decomposition of H2O2 to H2O and O2

by PtZrO2 was also confirmed experimentally (figure 12) The procedure adapted for

H2O2 decomposition by Zhou et al [17] was followed

4D 28 Mechanistic proposal

Our kinetic analysis supports a mechanistic model which assumes that the rate-

determining step involves direct interaction of the adsorbed oxidizing species with the

adsorbed reactant or an intermediate product of the reactant The mechanism proposed by

Mori et al [13] for alcohol oxidation by Pdhydroxyapatite is compatible with the above-

mentioned model This model involves the following steps

(i) formation of a metal-alcoholate species

(ii) which undergoes a -hydride elimination to produce benzaldehyde and a metal-

hydride intermediate and

(iii) reaction of this hydride with an oxidizing species having a surface concentration

directly proportional to adsorbed molecular oxygen which leads to the

regeneration of active catalyst and formation of O2 and H2O

The reaction mixture was subjected to the qualitative test for H2O2 production [13]

The color of KI-containing starch changed slightly from yellow to blue thus suggesting

that H2O2 is more likely to be an intermediate

This mechanism is similar to what has been proposed earlier by Sheldon and

Kochi [16] for the liquid-phase selective oxidation of primary and secondary alcohols

with molecular oxygen over supported platinum or reduced PtO2 in n-heptane at lower

temperatures ZrO2 alone is also active for benzyl alcohol oxidation in the presence of

oxygen (figure 2) Therefore a similar mechanism is envisaged for ZrO2 in benzyl

alcohol oxidation

84

Chapter 4D

References

1 Ferino I Casula F M Corrias A Cutrufello MG Monaci R Paschina G

Phys Chem Chem Phys 2002 2 1847-1854

2 Mallat T Baiker A Chem Rev 2004 104 3037-3058

3 Muzart J Ttetrahedron 2003 59 5789-5816

4 Rafelt J S Clark JH Catal Today 2000 57 33-44


J C Catal Today 2000 37 143-155


2005 232 432-443

7 Hutchings G J Carrettin S Landon P Edwards JK Enache D Knight

DW Xu Y CarleyAF Top Catal 2006 38 223-230



10 Opre Z Grunwaldt JD Mallat T BaikerA J Molec Catal A-Chem 2005

242 224-232

11 Opre Z Ferri D Krumeich F Mallat T Baiker A J Catal 2006 241 287-

293


A 2005 288 175-184


2004 126 10657-10666

14 Hashemi M M KhaliliB Eftikharisis B J Chem Res 2005 (Aug) 484-485

15 Makwana VD Son YC Howell AR Suib SL J Catal 2002 210 46-52

16 Sheldon R A Kochi J K Metal Catalyzed Oxidations of Organic Reactions

Academic Press New York 1981 p 354-355

17 Zhou H Shen YF Wang YJ Chen X OrsquoYoung CL Suib SL J Catal

1998 176 321-328

85

18 Charlot G Colorimetric Determination of Elements Principles and Methods

Elsvier Amsterdam 1964 pp 346 347 (Pt) pp 439 (Zr)

19 Engel T ErtlG in ldquoThe Chemical Physics of Solid Surfaces and Heterogeneous

Catalysisrdquo King D A Woodruff DP Elsvier Amsterdam 1982 vol 4 pp

71-93

86

Chapter 4E


Reactant Toluene in aqueous medium

Catalyst ZrO2 Pt ZrO2 Pd ZrO2

Oxidation of toluene in aqueous medium by Pt and PdZrO2

4E 1 Characterization of catalyst

The characterization of zirconia and zirconia supported platinum described in the

previous papers [1-3] Although the characterization of zirconia supported palladium

catalyst was described Fig 1 2 shows the SEM images of the catalyst before used and

after used From the figures it is clear that there is little bit different in the SEM images of

the fresh catalyst and used catalyst Although we did not observe this in the previous

studies of zirconia and zirconia supported platinum EDX of fresh and used PdZrO2

were given in the Fig 3 EDX of fresh catalyst show the peaks of Pd Zr and O while

EDX of the used PdZrO2 show peaks for Pd Zr O and C The presence of carbon

pointing to total oxidation from where it come and accumulate on the surface of catalyst

In fact the carbon present on the surface of catalyst responsible for deactivation of

catalyst widely reported [4 5] Fig 4 shows the XRD of monoclinic ZrO2 PtZrO2 and

PdZrO2 For ZrO2 the spectra is dominated by the peaks centered at 2θ = 2818deg and

3138deg which are characteristic of the monoclinic structure suggesting that the sample is

present mainly in the monoclinic phase calcined at 950degC [6] The reflections were

observed for Pd at 2θ = 404deg and 469deg and for Pt at 2θ =3979deg and 4628deg respectively

4E 2 Effect of substrate concentration

The study of amount of substrate is a subject of great importance Consequently

the concentration of toluene in water varied in the range 200- 1000 mg L-1 while other

parameters 1 wt PtZrO2 100 mg temperature 323 K partial pressure of oxygen ~

101 kPa agitation 900 rpm and time 30 min Fig 5 unveils the fact that toluene in the

lower concentration range (200- 400 mg L-1) was oxidized to benzoic acid only while at

higher concentration benzyl alcohol and benzaldehyde are also formed

87

a b

Figure 1

SEM image for fresh a (Pd ZrO2)

Figure 2

SEM image for Used b (Pd ZrO2)

Figure 3

EDX for fresh (a) and used (b) Pd ZrO2

Figure 4

XRD for ZrO2 Pt ZrO2 Pd ZrO2

88

4E 3 Effect of temperature

Effect of reaction temperature on the progress of toluene oxidation was studied in

the range of 303-333 K at a constant concentration of toluene (1000 mg L-1) while other

parameters were the same as in section 321 Fig 6 reveals that with increase in

temperature the conversion of toluene increases reaching maximum conversion at 333 K

The apparent activation energy is ~ 887 kJ mole-1 The value of activation energy in the

present case shows that in these conditions the reaction is most probably free of mass

transfer limitation [7]

4E 4 Agitation effect

The process is a liquid phase heterogeneous reaction having liquid reactants and a

solid catalyst The effect of mass transfer on the rate of reaction was determined by

studying the change in conversion at various speeds of agitation A PTFE coated stir bar

(L = 19 mm OD ~ 5 mm) was used for stirring For the oxidation of a toluene to proceed

the toluene and oxygen have to be present on the platinum or palladium catalyst surface

Oxygen has to be transferred from the gas phase to the liquid phase through the liquid to

the catalyst particle and finally has to diffuse to the catalytic site inside the particle The

toluene has to be transferred from the liquid bulk to the catalyst particle and to the

catalytic site inside the particle The reaction products have to be transferred in the

opposite direction Since the purpose of this study is to determine the intrinsic reaction

kinetics the absence of mass transfer limitations has to be verified Fig 7 shows that the

conversion increases in the initial stages and becomes constant at the stirring speed of

900 rpm and above Chaudhari et al [8 9] also reported similar results This is the region


The value activation energy and agitation study support the absence of mass transfer

effect

4E 5 Effect of catalyst loading

The effect of catalyst amount on the progress of oxidation of toluene was studied

in the range 20 ndash 100 mg while all other parameters were kept constant Fig 8 shows

89

Figure 7

Effect of agitation on the conversion of

toluene in aqueous medium catalyzed by

PtZrO2 at 333 K Catalyst (100 mg)

solution volume (10 mL) toluene

concentration (1000 mgL-1) pO2 (101

kPa) time (30 min)

Figure 8

Effect of catalyst loading on the

conversion of toluene in aqueous medium

catalyzed by PtZrO2 at 333 K Solution

volume (10 mL) toluene concentration

(200-1000 mgL-1) pO2 (101 kPa) stirring

(900 rpm) time (30 min)

Figure 5

Effect of substrate concentration on the


catalyzed by PtZrO2 at 333 K Catalyst

(100 mg) solution volume (10 mL)

toluene concentration (200-1000 mgL-1)

pO2 (101 kPa) stirring (900 rpm)

time (30

min)

Figure 6

Arrhenius plot for toluene oxidation

Temperature (303-333 K) Catalyst (100

mg) solution volume (10 mL) toluene


kPa) stirring (900 rpm) time (30 min)

90

that the rate of reaction increases in the range 20-80 mg and becomes approximately

constant afterward

4E 6 Time profile study

The time course study for the oxidation of toluene was periodically monitored

This investigation was carried out at 333 K by suspending 100 mg of catalyst in 10mL

(1000 mgL-1) of toluene in water oxygen partial pressure ~101 kPa and agitation 900

rpm Fig 9 indicates that the conversion increases linearly with increases in reaction

time

4E 7 Effect of Oxygen partial pressure

The effect of oxygen partial pressure was also studied in the lower range of 12-

101 kPa with a constant initial concentration of (1000 mg L-1) toluene in water at 333 K

The oxygen pressure also proved to be a key factor in the oxidation of toluene Fig 10

shows that increase in oxygen partial pressure resulted in increase in the rate of reaction

100 conversion is achieved only at pO2 ~101 kPa

4E8 Reaction Kinetics Analysis

From the effect of stirring and the apparent activation energy it is concluded that the

oxidation of toluene is most probably taking place in the kinetically controlled regime

This is a typical slurry reaction having catalyst in the solid state and reactants in liquid

and gas phase

As discussed earlier [111 the reaction kinetic analyses were performed by fitting the

experimental data to one of the three possible mechanisms of heterogeneous catalytic

oxidations

iv The Langmuir-Hinshelwood mechanism (L-H)

v The Mars-van Krevelen mechanism (M-K) or

vi The Eley-Rideal mechanism (E-R)

The Lndash H mechanism involves adsorption of the reacting species (toluene and oxygen) on

active sites at the surface followed by an irreversible rate-determining surface reaction

to give products The Langmuir-Hinshelwood rate law can be given as

91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)


Toluene [T] and O2 respectively The value of n can be taken 1or 05 for molecular or

dissociative adsorption of oxygen respectively For constant O2 or constant toluene

concentration equation (1) will be transformed by lumping together all the constants as to

2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)

The rate expression for Mars-van Krevelen mechanism can be given

ng

n

g

OkTk

OkTkRate

221

221

+=

(2)



pressure or constant Toluene concentration the equation was transformed to

Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)

The E-R mechanism envisage reaction between adsorbed oxygen with hydrocarbon

molecules from the fluid phase

ng

n

g

OK

TOkKRate

2

2

1+= (3)

In case of constant O2 pressure or constant toluene concentration equation 3 can be

transformed by lumping together all the constants to yield

TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)

The data obtained from the effect of substrate concentration (figure 5) and oxygen

partial pressure (figure 10) was subjected to kinetic analysis using a nonlinear regression

analysis according to the above-mentioned three models The rate data for toluene

conversion at different toluene concentration obtained at constant O2 pressure (from

figure 5) was subjected to kinetic analysis Equation (1a) and (2a) were not applicable to

92

the data It is obvious from (figure 11) that equation (3a) is applicable to the data with a

regression coefficient of ~0983 and excluding the data point for the highest

concentration (1000 mgL) the regression coefficient becomes more favorable (R2 ~

0999) Similarly the rate data for different O2 pressures at constant toluene

concentration (from figure 10) was analyzed using equations (1b) (2b) and (3b) using a

nonlinear least analysis software (Curve Expert 13) Equation (1b) was not applicable

to the data The best fit (R2 = 0993) was obtained for equations (2b) and (3b) as shown in

(figure 12) It has been mentioned earlier [1] that the rate expression for Mars-van

Krevelen and Eley-Rideal mechanisms have similar forms at a constant concentration of

the reacting hydrocarbon species However as equation (2a) is not applicable the

possibility of Mars-van Krevelen mechanism can be excluded Only equation (3) is

applicable to the data for constant oxygen concentration (3a) as well as constant toluene

concentration (3b) Therefore it can be concluded that the conversion of toluene on

PtZrO2 is taking place by Eley-Rideal mechanism It is up to the best of our knowledge

the first observation of a liquid phase reaction to be taking place by the Eley-Rideal

mechanism Considering the polarity of toluene in comparison to the solvent (water) and

its low concentration a weak or no adsorption of toluene on the surface cannot be ruled

out Ordoacutentildeez et al [12] have reported the Mars-van Krevelen mechanism for the deep

oxidation of toluene benzene and n-hexane catalyzed by platinum on -alumina

However in that reaction was taking place in the gas phase at a higher temperature and

higher gas phase concentration of toluene We have observed earlier [1] that the

Langmuir-Hinshelwood mechanism was operative for benzyl alcohol oxidation in n-

heptane catalyzed by PtZrO2 at 90 degC Similarly Makwana et al [11] have observed

Mars-van Krevelen mechanism for benzyl alcohol oxidation in toluene catalyzed by

OMS-2 at 90 degC In both the above cases benzyl alcohol is more polar than the solvent n-

heptan or toluene Similarly OMS-2 can be easily oxidized or reduced at a relatively

lower temperature than ZrO2

93

Figure 9

Time profile study of toluene oxidation

in aqueous medium catalyzed by PtZrO2

at 333 K Catalyst (100 mg) solution


(1000 mgL-1) pO2 (101 kPa) stirring

(900 rpm)

Figure 10

Effect of oxygen partial pressure on the


catalyzed by PtZrO2 at 333 K Catalyst (100


concentration (200-1000 mgL-1) stirring (900

rpm) time (30 min)

Figure 11

Rate of toluene conversion vs toluene

concentration Data for toluene

conversion from figure 1 was used

Figure 12

Plot of calculated conversion vs

experimental conversion Data from

figure 6 for the effect of oxygen partial

pressure effect on conversion of toluene

was analyzed according to E-R

mechanism using equation (3b)

94

4E 9 Comparison of different catalysts

Among the catalysts we studied as shown in table 1 both zirconia supported

platinum and palladium catalysts were shown to be active in the oxidation of toluene in

aqueous medium Monoclinic zirconia shows little activity (conversion ~17) while

tetragonal zirconia shows inertness toward the oxidation of toluene in aqueous medium

after a long (t=360 min) run Nevertheless zirconia supported platinum appeared as the

best High activities were measured even at low temperature (T ~ 333k) Zirconia

supported palladium catalyst was appear to be more selective for benzaldehyde in both

unreduced and reduced form Furthermore zirconia supported palladium catalyst in

reduced form show more activity than that of unreduced catalyst In contrast some very

good results were obtained with zirconia supported platinum catalysts in both reduced

and unreduced form Zirconia supported platinum catalyst after reduction was found as a

better catalyst for oxidation of toluene to benzoic in aqueous medium Furthermore as

we studied the Pt ZrO2 catalyst for several run we observed that the activity of the

catalyst was retained

Table 1

Comparison of different catalysts for toluene oxidation

in aqueous medium

95

Chapter 4E

References




9750-8

9 Markusse AP Kuster BFM Koningsberger DC Marin GB Catal

Lett1998 55 141

10 Markusse AP Kuster BFM Schouten JC Stud Surf Sci Catal1999 126

273




A 2005 288 175-184

13 Choudhary V R Dhar A Jana P Jha R de Upha B S GreenChem 2005

7 768


15 Makwana V D Son Y C Howell A R Suib S L J Catal 2002 210 46-52

16 Ordoacutentildeez S Bello L Sastre H Rosal R Diez F V Appl Catal B 2002 38

139

96

Chapter 4F


Reactant Cyclohexane


Oxidation of cyclohexane in solvent free by zirconia supported noble metals

4F1 Characterization of catalyst

Fig1 shows X-ray diffraction patterns of tetragonal ZrO2 monoclinic ZrO2 Pd

monoclinic ZrO2 and Pt monoclinic ZrO2 respectively Freshly prepared sample was

almost amorphous The crystallinity of the sample begins to develop after calcining the

sample at 773 -1223K for 4 h as evidenced by sharper diffraction peaks with increased

calcination temperature The samples calcined at 773K for 4h exhibited only the

tetragonal phase (major peak appears at 2 = 3094deg) and there was no indication of

monoclinic phase For ZrO2 calcined at 950degC the spectra is dominated by the peaks

centered at 2 = 2818deg and 3138deg which are characteristic of the monoclinic structure

suggesting that the sample is present mainly in the monoclinic phase The reflections

were observed for Pd at 2θ = 404deg and 469deg and for Pt at 2θ =3979deg and 4628deg

respectively The X-ray diffraction patterns of Pd supported on tetragonal ZrO2 and Pt

supported on tetragonal ZrO2 annealed at different temperatures is shown in Figs2 and 3

respectively No peaks appeared at 2θ = 2818deg and 3138deg despite the increase in

temperature (from 773 to 1223K) It seems that the metastable tetragonal structure was

stabilized at the high temperature as a function of the doped Pd or Pt which was

supported by the X-ray diffraction analysis of the Pd or Pt-free sample synthesized in the

same condition and annealed at high temperature Fig 4 shows the X-ray diffraction

pattern of the pure tetragonal ZrO2 annealed at different temperatures (773K 823K

1023K and1223K) The figure reveals tetragonal ZrO2 at 773K increasing temperature to

823K a fraction of monoclinic ZrO2 appears beside tetragonal ZrO2 An increase in the

fraction of monoclinic ZrO2 is observed at 1023K while 1223K whole of ZrO2 found to

be monoclinic It is clear from the above discussion that the presence of Pd or Pt

stabilized tetragonal ZrO2 and further phase change did not occur even at high

97

Figure 1

XRD patterns of ZrO2 (T) ZrO2 (m) PdZrO2 (m)

and Pt ZrO2 (m)

Figure 2

XRD patterns of PdZrO2 (T) annealed at

773K 823K 1023K and 1223K respectively

Figure 3

XRD patterns of PtZrO2 (T) annealed at 773K

823K 1023K and1223K respectively

Figure 4

XRD patterns of pure ZrO2 (T) annealed at

773K 823K 1023K and1223K respectively

98

temperature [1] Therefore to prepare a catalyst (noble metal supported on monoclinic

ZrO2) the sample must be calcined at higher temperature ge1223K to ensure monoclinic

phase before depositing noble metal The surface area of samples as a function of

calcination temperature is given in Table 1 The main trend reflected by these results is a

decrease of surface area as the calcination temperature increases Inspecting the table

reveals that Pd or Pt supported on ZrO2 shows no significant change on the particle size

The surface area of the 1 Pd or PtZrO2 (T) sample decreased after depositing Pd or Pt in

it which is probably due to the blockage of pores but may also be a result of the

increased density of the Pd or Pt

4F2 Oxidation of cyclohexane

The oxidation of cyclohexane was carried out at 353 K for 6 h at 1 atmospheric

pressure of O2 over either pure ZrO2 or Pd or Pt supported on ZrO2 catalyst The

experiment results are listed in Table 1 When no catalyst (as in the case of blank

reaction) was added the oxidation reaction did not proceed readily However on the

addition of pure ZrO2 (m) or Pd or Pt ZrO2 as a catalyst the oxidation reaction between

cyclohexane and molecular oxygen was initiated As shown in Table 1 the catalytic

activity of ZrO2 (T) and PdO or PtO supported on ZrO2 (T) was almost zero while Pd or Pt

supported on ZrO2 (T) shows some catalytic activity toward oxidation of cyclohexane The

reason for activity is most probably reduction of catalyst in H2 flow (40mlmin) which

convert a fraction of ZrO2 (T) to monoclinic phase The catalytic activity of ZrO2 (m)

gradually increases in the sequence of ZrO2 (m) lt PdOZrO2 (m) lt PtOZrO2 (m) lt PdZrO2

(m) lt PtZrO2 (m) The results were supported by arguments that PtZrO2ndashWOx catalysts

that include a large fraction of tetragonal ZrO2 show high n-butane isomerization activity

and low oxidation activity [2 3] As one can also observe from Table 1 that PtZrO2 (m)

was more selective and reactive than that of Pd ZrO2 (m) Fig 5 shows the stirring effect

on oxidation of cyclohexane At higher agitation speed the rate of reaction became

99

Table 1

Oxidation of cyclohexane to cyclohexanone and cyclohexanol

with molecular oxygen at 353K in 360 minutes

Figure 5

Effect of agitation on the conversion of cyclohexane

catalyzed by Pt ZrO2 (m) at temperature = 353K Catalyst

weight = 100mg volume of reactant = 20 ml partial pressure

of O2 = 760 Torr time = 360 min

100

constant which indicate that the rates are kinetic in nature and unaffected by transport

restrictions Ilyas et al [4] also reported similar results All further reactions were

conducted at higher agitation speed (900-1200rpm) Fig 6 shows dependence of rate on

temperature The rate of reaction linearly increases with increase in temperature The

apparent activation energy was 581kJmole-1 which supports the absence of mass transfer

resistance [5] The conversions of cyclohexane to cyclohexanol and cyclohexanone are

shown in Fig 7 as a function of time on PtZrO2 (m) at 353 K Cyclohexanol is the

predominant product during an initial induction period (~ 30 min) before cyclohexanone

become detectable The cyclohexanone selectivity increases with increase in contact time

4F3 Optimal conditions for better catalytic activity

The rate of the reaction was measured as a function of different parameters like

temperature partial pressure of oxygen amount of catalyst volume of reactants agitation

and reaction duration The rate of reaction also shows dependence on the morphology of

zirconia deposition of noble metal on zirconia and reduction of noble metal supported on

zirconia in the flow of H2 gas It was found that reduced Pd or Pt supported on ZrO2 (m) is

more reactive and selective toward the oxidation of cyclohexane at temperature 353K

agitation 900rpm pO2 ~ 760 Torr weight of catalyst 100mg volume of reactant 20ml

and time 360 minutes

101

Figure 6

Arrhenius Plot Ln conversion vs 1T (K)

Figure 7

Time profile study of cyclohexane oxidation catalyzed by Pt ZrO2 (m)

Reaction condition temperature = 353K Catalyst weight = 100mg

volume of reactant = 20 ml partial pressure of O2 = 760 Torr

agitation speed = 900rpm

102

Chapter 4F

References




4 Ilyas M Sadiq M Catal Lett 2008 (online first) DOI 101007s10562-

008-9750-8


103

Chapter 4G


Reactant Phenol in aqueous medium

Catalyst PtZrO2 PdZrO2 Pt-PdZrO2 Bi2O3ZrO2 and MnO2ZrO2

Oxidation of phenol in aqueous medium by zirconia-supported noble metals

4G1 Characterization of catalyst

X-ray powder diffraction pattern of the sample reported in Fig 1 confirms the

monoclinic structure of zirconia The major peaks responsible for monoclinic structure

appears at 2 = 2818deg and 3138deg while no characteristic peak of tetragonal phase (2 =

3094deg) was appeared suggesting that the zirconia is present in purely monoclinic phase

The reflections were observed for Pd at 2θ = 404deg and 469deg and for Pt at 2θ =3979deg and

4628deg respectively [1] For Bi2O3 the peaks appear at 2θ = 277deg 305deg33deg 424deg and

472deg while for MnO2 major peaks observed at 2θ = 261deg 289deg In this all catalyst

zirconia maintains its monoclinic phase SEM micrographs of fresh samples reported in

Fig 2 show the homogeneity of the crystal size of monoclinic zirconia The micrographs

of PtZrO2 PdZrO2 and Pt-PdZrO2 revealed that the active metals are well dispersed on

support while the micrographs of Bi2O3ZrO2 and MnO2ZrO2 show that these are not

well dispersed on zirconia support Fig 3 shows the EDX analysis results for fresh and

used ZrO2 PtZrO2 PdZrO2 Pt-PdZrO2 Bi2O3ZrO2 and MnO2ZrO2 samples The

results show the presence of carbon in used samples Probably come from the total

oxidation of organic substrate Many researchers reported the presence of chlorine and

carbon in the EDX of freshly prepared samples [1 2] suggesting that chlorine come from

the matrix of zirconia and carbon from ethylene diamine In our case we did used

ethylene diamine and did observed the carbon in the EDX of fresh samples We also did

not observe the chlorine in our samples

104

Figure 1

XRD of different catalysts

105

Figure 2 SEM of different catalyst a ZrO2 b Pt ZrO2 c Pd ZrO2 d Pt-Pd ZrO2 e

Bi2O3 f Bi2O3 ZrO2 g MnO2 h MnO2 ZrO2

a b

c d

e f

h g

106

Fresh ZrO2 Used ZrO2

Fresh PtZrO2 Used PtZrO2

Fresh Pt-PdZrO2 Used Pt-Pd ZrO2

Fresh Bi-PtZrO2 Used Bi-PtZrO2

107

Fresh Bi-PdZrO2 Used Bi-Pd ZrO2

Fresh Bi2O3ZrO2 Fresh Bi2O3ZrO2

Fresh MnO2ZrO2 Used MnO2 ZrO2

Figure 3

EDX of different catalyst of fresh and used

108

4G2 Catalytic oxidation of phenol

Oxidation of phenol was significantly higher over PtZrO2 catalyst Combination

of 1 Pd and 1 Pt on ZrO2 gave an activity comparable to that of the Pd ZrO2 or

PtZrO2 catalysts Adding 05 Bismuth significantly increased the activity of the ZrO2

supported Pt shows promising activity for destructive oxidation of organic pollutants in

the effluent at 333 K and 101 kPa in the liquid phase 05 Bismuth inhibit the activity

of the ZrO2 supported Pd catalyst

4G3 Effect of different parameters

Different parameters of reaction have a prominent effect on the catalytic oxidation

of phenol in aqueous medium

4G4 Time profile study

The conversion of the phenol with time is reported in Fig 4 for Bi promoted

zirconia supported platinum catalyst and for the blank experiment In the absence of any

catalyst no conversion is obtained after 3 h while ~ total conversion can be achieved by

Bi-PtZrO2 in 3h Bismuth promoted zirconia-supported platinum catalyst show very

good specific activity for phenol conversion (Fig 4)

4G5 Comparison of different catalysts

The activity of different catalysts was found in the order Pt-PdZrO2gt Bi-

PtZrO2gt Bi-PdZrO2gt PtZrO2gt PdZrO2gt CuZrO2gt MnZrO2 gt BiZrO2 Bi-PtZrO2 is

the most active catalyst which suggests that Bi in contact with Pt particles promote metal

activity Conversion (C ) are reported in Fig 5 However though very high conversions

can be obtained (~ 91) a total mineralization of phenol is never observed Organic

intermediates still present in solution widely reported [3] Significant differences can be

observed between bi-PtZrO2 and other catalyst used

109

Figure 4

Time profile study Temp 333 K

Cat 02g substrate solution 20 ml

(10g dm-3) of phenol in water pO2

760 Torr and agitation 900 rpm

Figure 5

Comparison of different catalysts

Temp 333 K Cat 02g substrate

solution 20 ml (10g dm-3) of phenol

in water pO2 760 Torr and

agitation 900 rpm

Figure 6

Effect of Pd loading on conversion




agitation 900 rpm

Figure 7

Effect of Pt loading on conversion

Temp 333 K Cat 02g substrate solution

20 ml (10g dm-3) of phenol in water pO2


110

4G6 Effect of Pd and Pt loading on catalytic activity

The influence of platinum and palladium loading on the activity of zirconia-

supported Pd catalysts are reported in Fig 6 and 7 An increase in Pt loading improves

the activity significantly Phenol conversion increases linearly with increase in Pt loading

till 15wt In contrast to platinum an increase in Pd loading improve the activity

significantly till 10 wt Further increase in Pd loading to 15 wt does not result in

further improvement in the activity [4]

4G 7 Effect of bismuth addition on catalytic activity

The influence of bismuth on catalytic activities of PtZrO2 PdZrO2 catalysts is

reported in Fig 8 9 Adding 05 wt Bi on zirconia improves the activity of PtZrO2

catalyst with a 10 wt Pt loading In contrast to supported Pt catalyst the activity of

supported Pd catalyst with a 10 wt Pd loading was decreased by addition of Bi on

zirconia The profound inhibiting effect was observed with a Bi loading of 05 wt

4G 8 Influence of reduction on catalytic activity

High catalytic activity was obtained for reduce catalysts as shown in Fig 10

PtZrO2 was more reactive than PtOZrO2 similarly Pd ZrO2 was found more to be

reactive than unreduce Pd supported on zirconia Many researchers support the

phenomenon observed in the recent study [5]

4G 9 Effect of temperature

Fig 11 reveals that with increase in temperature the conversion of phenol

increases reaching maximum conversion at 333K The apparent activation energy is ~

683 kJ mole-1 The value of activation energy in the present case shows that in these

conditions the reaction is probably free of mass transfer limitation [6-8]

111

Figure 8

Effect of bismuth on catalytic activity

of PdZrO2 Temp 333 K Cat 02g

substrate solution 20 ml (10g dm-3) of

phenol in water pO2 760 Torr and

agitation 900 rpm

Figure 9


of PtZrO2 Temp 333 K Cat 02g



agitation 900 rpm

Figure 10

Effect of reduction on catalytic activity


solution 20 ml (10g dm-3) of phenol in

water pO2 760 Torr and agitation 900

rpm

Figure 11

Effect of temp on the conversion of phenol

Temp 303-333 K Bi-1wtPtZrO2 02g

substrate 20 ml (10g dm-3) pO2 760 Torr and

agitation 900 rpm

112

Chapter 4G

References

1 Souza L D Subaie JS Richards R J Colloid Interface Sci 2005 292 476ndash

485


M Micropor Mesopor Mater 2006 88 22ndash30

3 Zhang Q Chuang KT Ind Eng Chem Res 1998 37 3343 -3349

4 Resini C Catania F Berardinelli S Paladino O Busca G Appl Catal B

Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review

bull ZrO2 is an effective catalyst for the selective oxidation of alcohols to ketones and

aldehydes under solvent free conditions with comparable activity to other

expensive catalysts ZrO2 calcined at 1223 K is more active than ZrO2 calcined at

723 K Moreover the oxidation of alcohols follows the principles of green

chemistry using molecular oxygen as the oxidant under solvent free conditions

From the study of the effect of oxygen partial pressure at pO2 le101 kPa it is

concluded that air can be used as the oxidant under these conditions Monoclinic

phase ZrO2 is an effective catalyst for synthesis of aldehydes ketone

Characterization of the catalyst shows that it is highly promising reusable and

easily separable catalyst for oxidation of alcohol in liquid phase solvent free

condition at atmospheric pressure The reaction shows first order dependence on

the concentration of alcohol and catalyst Kinetics of this reaction was found to

follow a Langmuir-Hinshelwood oxidation mechanism

bull Monoclinic ZrO2 is proved to be a better catalyst for oxidation of benzyl alcohol

in aqueous medium at very mild conditions The higher catalytic performance of

ZrO2 for the total oxidation of benzyl alcohol in aqueous solution attributed here

to a high temperature of calcinations and a remarkable monoclinic phase of

zirconia It can be used with out any base addition to achieve good results The

catalyst is free from any promoter or additive and can be separated from reaction

mixture by simple filtration This gives us the idea to conclude that catalyst can

be reused several times Optimal conditions for better catalytic activity were set as

time 6h temp 60˚C agitation 900rpm partial pressure of oxygen 760 Torr

catalyst amount 200mg It summarizes that ZrO2 is a promising catalytic material

for different alcohols oxidation in near future

bull PtZrO2 is an active catalyst for toluene partial oxidation to benzoic acid at 60-90

C in solvent free conditions The rate of reaction is limited by the supply of

oxygen to the catalyst surface Selectivity of the products depends upon the

114

reaction time on stream With a reaction time 3 hrs benzyl alcohol

benzaldehyde and benzoic acid are the only products After 3 hours of reaction

time benzyl benzoate trans-stilbene and methyl biphenyl carboxylic acid appear

along with benzoic acid and benzaldehyde In both the cases benzoic acid is the

main product (selectivity 60)

bull PtZrO2 is used as a catalyst for liquid-phase oxidation of benzyl alcohol in a

slurry reaction The alcohol conversion is almost complete (gt99) after 3 hours

with 100 selectivity to benzaldehyde making PtZrO2 an excellent catalyst for

this reaction It is free from additives promoters co-catalysts and easy to prepare

n-heptane was found to be a better solvent than toluene in this study Kinetics of

the reaction was investigated and the reaction was found to follow the classical

Langmuir-Hinshelwood model

bull The results of the present study uncovered the fact that PtZrO2 is also a better

catalyst for catalytic oxidation of toluene in aqueous medium This gives us

reasons to conclude that it is a possible alternative for the purification of

wastewater containing toluene under mild conditions Optimizing conditions for

complete oxidation of toluene to benzoic acid in the above-mentioned range are

time 30 min temperature 333 K agitation 900 rpm pO2 ~ 101 kPa catalyst

amount 100 mg The main advantage of the above optimal conditions allows the

treatment of wastewater at a lower temperature (333 K) Catalytic oxidation is a

significant method for cleaning of toxic organic compounds from industrial

wastewater

bull It has been demonstrated that pure ZrO2 (T) change to monoclinic phase at high

temperature (1223K) while Pd or Pt doped ZrO2 (T) shows stability even at high

temperature ge 1223K It was found that the degree of stability at high temperature

was a function of noble metal doping Pure ZrO2 (T) PdO ZrO2 (T)

and PtO ZrO2

(T) show no activity while Pd ZrO2 (T)

and Pt ZrO2 (T)

show some activity in

cyclohexane oxidation ZrO2 (m) and well dispersed Pd or Pt ZrO2 (m)

system is

very active towards oxidation and shows a high conversion Furthermore there

was no leaching of the Pd or Pt from the system observed Overall it is

115

demonstrated that reduced Pd or Pt supported on ZrO2 (m) can be prepared which is

very active towards oxidation of cyclohexane in solvent free conditions at 353K

bull Bismuth promoted PtZrO2 and PdZrO2 catalysts are each promising for the

destructive oxidation of the organic pollutants in the industrial effluents Addition

of Bi improves the activity of PtZrO2 catalysts but inhibits the activity of

PdZrO2 catalyst at high loading of Pd Optimal conditions for better catalytic

activity temp 333K wt of catalyst 02g agitation 900rpm pO2 101kPa and time

180min Among the emergent alternative processes the supported noble metals

catalytic oxidation was found to be effective for the treatment of several

pollutants like phenols at milder temperatures and pressures

bull To sum up from the above discussion and from the given table that ZrO2 may

prove to be a better catalyst for organic oxidation reaction as well as a superior

support for noble metals

116

116

Table Catalytic oxidation of different organic compounds by zirconia and zirconia supported noble metals

mohammad_sadiq26yahoocom

Catalyst Solvent Duration

(hours)

Reactant Product Conversion

()

Ref

ZrO2(t) - 24 Cyclohexanol

Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III

ZrO2(m) - 24 Cyclohexanol

Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I

ZrO2(m) water 6 Benzyl alcohol Benzaldehyde

Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)

n-heptane 3 Benzyl alcohol Benzaldehyde

~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-

biphenylcarbxylic acid

372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)

water 05 Toluene Benzoic acid ~100 VI

Pt ZrO2(m)

(reduce in

H2 flow)

- 6 Cyclohexane Cyclohexanol

cyclohexanone

14

401

V

Bi-Pt ZrO2

water 3 Phenol Complete oxidation IX


CATALYST AND AS A SUPPORT FOR NOBLE METALS

IN ORGANIC OXIDATION REACTIONS

A dissertation submitted to the University of Peshawar in partial

fulfillment for the degree of

DOCTOR OF PHILOSOPHY IN PHYSICAL CHEMISTRY

Presented by

MOHAMMAD SADIQ



2009

i

ii

Acknowledgment

























And at last


Mr Mohammad Sadiq

iii

Abstract






























iv























2008






v

TABLE OF CONTENTS


Acknowledgment ii

Abstract iii
















References 20

vi

TABLE OF CONTENTS



31 Material 30
















References 42

vii

TABLE OF CONTENTS
















References 54







References 62

viii

TABLE OF CONTENTS











References 70














References 84

ix

TABLE OF CONTENTS




by PtZrO2 86










References 95







References 102






x

TABLE OF CONTENTS









References 112


1

Chapter 1

Introduction


























2












environment







lower temperature












3





























4
































5
































6































7








ii In solvent
























8































aqueous solution

9






























10
































11




























12































13

























determining [126]

14

Chapter 2

Literature review




























15
































16
































17
































18
























carbonate species








19










20

Chapter 1amp 2

References


























2005 232 432

21






242 224-232


287-293


Catal A 2005 288 175-184


2004 126 10657-10666



52


2005 7 768




Science 2006 311 362








2006 108 137


22



303-335














Eng J 1999 73 143



24 79




2153



2001 35 2828


181



23


2001 32 151





1998 37 3561



1999 188 311


Today 2000 62 379







381310




1996 29 317




Environ 2000 28113


Chemical 2007 275 167-173



24



231 75ndash81








362










1993







195


30 341


25















2002 45 180


40 587






9750-8


1977




3958


1982 4 411-18

26


Catal B 1996 11 L29-L35


B 1996 11 L11-L18


Environ 2008 84 678-683


sons Newyork 1982


2797






Trans 1998 94 1875


1998 36 55-97


1963 110 23





1997 9 670






27






67


1987 17 249











2008112 291-298



A1999 176 27



2001 44 221



A2001 214 273




28


J Phys Chem B 2003 107 497




99













198730353













29



292 476ndash485



30

Chapter 3

Experimental

31 Material















ii Commercial ZrO2









31

Figure 1


32






323 Commercial ZrO2





















33



























34

Figure 2



35

Figure 3



36

Figure 4



37












Figure 5


38













Figure 6



39



i chemical methods












eluent

















40



41














7 is reduced





in Fig 8











100() minus

=Ci

CfCiX

42

Chapter 3

References





9750-8




2006 110 255



43

Chapter 4A



Catalyst ZrO2























44

Figure 1



Figure 2


Figure 3



a2 b2 2000 at 25 kV

Figure 4


after use

45































46

























1223 K

47

Figure 5









Figure 6





(3) n-Octanol

Figure 7





K (3) 393 K (4) 403 K (5) 413 K


N2) = 40 mlmin)

Figure 8



adsorption

48































49




2

21

O

O

kKpr

Kp=

+ (1)


( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)




2

1 1 1

Or kKp k= + (3)




( )2

1

2

1 1 1

O

r kk Kp

= + (4)










50



























CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51



C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)



C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)






dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)




52

427 Role of oxygen





























O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53


















on the







p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred



54

Chapter 4A

References









Commun 2006 7 24


113 34


1987 9ndash72



311 362




New York 1981









55





374



125


1994 120 127




132

30 Haber J Z Chem 1973 13 241








56

Chapter 4B



Catalyst ZrO2

















57

Figure 1



ZrO2)

Figure 2



58

Figure 3


59





























10

60

Figure 6a and 6b


Figure 4





time 6 hours

Figure 5







61

Figure 7


(6 hrs)


Conversion

Figure 9





hrs)

Figure 8



Figure 10



62

Chapter 4B

References


Research 2005 35 23-28




A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2























64

Figure 1


Figure 2




65



























reactor

66

Table 1


Reaction conditions




Figure 3


Reaction conditions



(900 rpm)

Figure 4


conversions

Reaction conditions



(900 rpm)

67






























68

Figure 7



Figure 5



Reaction conditions



rpm) time (3 h)

Figure 6









69













70

Chapter 4C

References







2005 107ndash108 175





615







2006 110 255


14 Lee T P US Patent 4091044 1978


4278824 1981




2002

71

Chapter 4D














used catalysts












72















benzaldehyde













73

Figure 1


Figure 2








Figure 3







(900rpm) time (1hr)

74
















transfer limitation

4D24 Solvent Effect









75












Rate = -dCdt



















76



Figure 4







Reaction conditions




(900rpm)

Figure 5



Figure 6



77





alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]


alcohol





surface



BzOHb

BzOHaRate

+=

1 (2)




can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)




BzOHcb

BzOHaRate

+= (4)

78




1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)





2BzOHcb

BzOHaRate

+= (6)










as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate


and

BzOH

a

c

a

b

Rate




79

Figure 7



(6)

Figure 8



Figure 9



Figure 10






rmp)

80







7 8 and 10)








1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)



1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)


2Rate a O= (12)




81

22

2

Ocb

OaRate

+= (13)


2

42

Oa

c

a

b

Rate

O+= (14)












gads

ad OkOkdt

Od22 == minus

(15)











82

Figure 11






rmp)

Figure 12


PtZrO2




83



























alcohol oxidation

84

Chapter 4D

References







J C Catal Today 2000 37 143-155


2005 232 432-443






242 224-232


293


A 2005 288 175-184


2004 126 10657-10666






1998 176 321-328

85





71-93

86

Chapter 4E




























87

a b

Figure 1


Figure 2


Figure 3


Figure 4


88

























effect




89

Figure 7






kPa) time (30 min)

Figure 8







Figure 5







time (30

min)

Figure 6






90


constant afterward






time











and gas phase



oxidations







91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)





2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)


ng

n

g

OkTk

OkTkRate

221

221

+=

(2)




Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)



ng

n

g

OK

TOkKRate

2

2

1+= (3)



TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)






92




























93

Figure 9






(900 rpm)

Figure 10






rpm) time (30 min)

Figure 11




Figure 12







94
















Table 1


in aqueous medium

95

Chapter 4E

References




9750-8


Lett1998 55 141


273




A 2005 288 175-184


7 768




139

96

Chapter 4F





























97

Figure 1


and Pt ZrO2 (m)

Figure 2



Figure 3



Figure 4



98



























99

Table 1



Figure 5





100



















101

Figure 6


Figure 7





102

Chapter 4F

References





008-9750-8


103

Chapter 4G

























104

Figure 1


105



a b

c d

e f

h g

106





107




Figure 3


108

























109

Figure 4





Figure 5





agitation 900 rpm

Figure 6





agitation 900 rpm

Figure 7





110
























111

Figure 8





agitation 900 rpm

Figure 9





agitation 900 rpm

Figure 10





rpm

Figure 11




agitation 900 rpm

112

Chapter 4G

References


485





Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review




























114






















wastewater





and PtO ZrO2


and Pt ZrO2 (T)



system is



115














116

116




(hours)


()

Ref


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I


Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)


~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-


372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)


Pt ZrO2(m)

(reduce in

H2 flow)


cyclohexanone

14

401

V

Bi-Pt ZrO2


i

ii

Acknowledgment

























And at last


Mr Mohammad Sadiq

iii

Abstract






























iv























2008






v

TABLE OF CONTENTS


Acknowledgment ii

Abstract iii
















References 20

vi

TABLE OF CONTENTS



31 Material 30
















References 42

vii

TABLE OF CONTENTS
















References 54







References 62

viii

TABLE OF CONTENTS











References 70














References 84

ix

TABLE OF CONTENTS




by PtZrO2 86










References 95







References 102






x

TABLE OF CONTENTS









References 112


1

Chapter 1

Introduction


























2












environment







lower temperature












3





























4
































5
































6































7








ii In solvent
























8































aqueous solution

9






























10
































11




























12































13

























determining [126]

14

Chapter 2

Literature review




























15
































16
































17
































18
























carbonate species








19










20

Chapter 1amp 2

References


























2005 232 432

21






242 224-232


287-293


Catal A 2005 288 175-184


2004 126 10657-10666



52


2005 7 768




Science 2006 311 362








2006 108 137


22



303-335














Eng J 1999 73 143



24 79




2153



2001 35 2828


181



23


2001 32 151





1998 37 3561



1999 188 311


Today 2000 62 379







381310




1996 29 317




Environ 2000 28113


Chemical 2007 275 167-173



24



231 75ndash81








362










1993







195


30 341


25















2002 45 180


40 587






9750-8


1977




3958


1982 4 411-18

26


Catal B 1996 11 L29-L35


B 1996 11 L11-L18


Environ 2008 84 678-683


sons Newyork 1982


2797






Trans 1998 94 1875


1998 36 55-97


1963 110 23





1997 9 670






27






67


1987 17 249











2008112 291-298



A1999 176 27



2001 44 221



A2001 214 273




28


J Phys Chem B 2003 107 497




99













198730353













29



292 476ndash485



30

Chapter 3

Experimental

31 Material















ii Commercial ZrO2









31

Figure 1


32






323 Commercial ZrO2





















33



























34

Figure 2



35

Figure 3



36

Figure 4



37












Figure 5


38













Figure 6



39



i chemical methods












eluent

















40



41














7 is reduced





in Fig 8











100() minus

=Ci

CfCiX

42

Chapter 3

References





9750-8




2006 110 255



43

Chapter 4A



Catalyst ZrO2























44

Figure 1



Figure 2


Figure 3



a2 b2 2000 at 25 kV

Figure 4


after use

45































46

























1223 K

47

Figure 5









Figure 6





(3) n-Octanol

Figure 7





K (3) 393 K (4) 403 K (5) 413 K


N2) = 40 mlmin)

Figure 8



adsorption

48































49




2

21

O

O

kKpr

Kp=

+ (1)


( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)




2

1 1 1

Or kKp k= + (3)




( )2

1

2

1 1 1

O

r kk Kp

= + (4)










50



























CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51



C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)



C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)






dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)




52

427 Role of oxygen





























O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53


















on the







p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred



54

Chapter 4A

References









Commun 2006 7 24


113 34


1987 9ndash72



311 362




New York 1981









55





374



125


1994 120 127




132

30 Haber J Z Chem 1973 13 241








56

Chapter 4B



Catalyst ZrO2

















57

Figure 1



ZrO2)

Figure 2



58

Figure 3


59





























10

60

Figure 6a and 6b


Figure 4





time 6 hours

Figure 5







61

Figure 7


(6 hrs)


Conversion

Figure 9





hrs)

Figure 8



Figure 10



62

Chapter 4B

References


Research 2005 35 23-28




A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2























64

Figure 1


Figure 2




65



























reactor

66

Table 1


Reaction conditions




Figure 3


Reaction conditions



(900 rpm)

Figure 4


conversions

Reaction conditions



(900 rpm)

67






























68

Figure 7



Figure 5



Reaction conditions



rpm) time (3 h)

Figure 6









69













70

Chapter 4C

References







2005 107ndash108 175





615







2006 110 255


14 Lee T P US Patent 4091044 1978


4278824 1981




2002

71

Chapter 4D














used catalysts












72















benzaldehyde













73

Figure 1


Figure 2








Figure 3







(900rpm) time (1hr)

74
















transfer limitation

4D24 Solvent Effect









75












Rate = -dCdt



















76



Figure 4







Reaction conditions




(900rpm)

Figure 5



Figure 6



77





alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]


alcohol





surface



BzOHb

BzOHaRate

+=

1 (2)




can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)




BzOHcb

BzOHaRate

+= (4)

78




1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)





2BzOHcb

BzOHaRate

+= (6)










as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate


and

BzOH

a

c

a

b

Rate




79

Figure 7



(6)

Figure 8



Figure 9



Figure 10






rmp)

80







7 8 and 10)








1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)



1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)


2Rate a O= (12)




81

22

2

Ocb

OaRate

+= (13)


2

42

Oa

c

a

b

Rate

O+= (14)












gads

ad OkOkdt

Od22 == minus

(15)











82

Figure 11






rmp)

Figure 12


PtZrO2




83



























alcohol oxidation

84

Chapter 4D

References







J C Catal Today 2000 37 143-155


2005 232 432-443






242 224-232


293


A 2005 288 175-184


2004 126 10657-10666






1998 176 321-328

85





71-93

86

Chapter 4E




























87

a b

Figure 1


Figure 2


Figure 3


Figure 4


88

























effect




89

Figure 7






kPa) time (30 min)

Figure 8







Figure 5







time (30

min)

Figure 6






90


constant afterward






time











and gas phase



oxidations







91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)





2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)


ng

n

g

OkTk

OkTkRate

221

221

+=

(2)




Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)



ng

n

g

OK

TOkKRate

2

2

1+= (3)



TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)






92




























93

Figure 9






(900 rpm)

Figure 10






rpm) time (30 min)

Figure 11




Figure 12







94
















Table 1


in aqueous medium

95

Chapter 4E

References




9750-8


Lett1998 55 141


273




A 2005 288 175-184


7 768




139

96

Chapter 4F





























97

Figure 1


and Pt ZrO2 (m)

Figure 2



Figure 3



Figure 4



98



























99

Table 1



Figure 5





100



















101

Figure 6


Figure 7





102

Chapter 4F

References





008-9750-8


103

Chapter 4G

























104

Figure 1


105



a b

c d

e f

h g

106





107




Figure 3


108

























109

Figure 4





Figure 5





agitation 900 rpm

Figure 6





agitation 900 rpm

Figure 7





110
























111

Figure 8





agitation 900 rpm

Figure 9





agitation 900 rpm

Figure 10





rpm

Figure 11




agitation 900 rpm

112

Chapter 4G

References


485





Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review




























114






















wastewater





and PtO ZrO2


and Pt ZrO2 (T)



system is



115














116

116




(hours)


()

Ref


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I


Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)


~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-


372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)


Pt ZrO2(m)

(reduce in

H2 flow)


cyclohexanone

14

401

V

Bi-Pt ZrO2


ii

Acknowledgment

























And at last


Mr Mohammad Sadiq

iii

Abstract






























iv























2008






v

TABLE OF CONTENTS


Acknowledgment ii

Abstract iii
















References 20

vi

TABLE OF CONTENTS



31 Material 30
















References 42

vii

TABLE OF CONTENTS
















References 54







References 62

viii

TABLE OF CONTENTS











References 70














References 84

ix

TABLE OF CONTENTS




by PtZrO2 86










References 95







References 102






x

TABLE OF CONTENTS









References 112


1

Chapter 1

Introduction


























2












environment







lower temperature












3





























4
































5
































6































7








ii In solvent
























8































aqueous solution

9






























10
































11




























12































13

























determining [126]

14

Chapter 2

Literature review




























15
































16
































17
































18
























carbonate species








19










20

Chapter 1amp 2

References


























2005 232 432

21






242 224-232


287-293


Catal A 2005 288 175-184


2004 126 10657-10666



52


2005 7 768




Science 2006 311 362








2006 108 137


22



303-335














Eng J 1999 73 143



24 79




2153



2001 35 2828


181



23


2001 32 151





1998 37 3561



1999 188 311


Today 2000 62 379







381310




1996 29 317




Environ 2000 28113


Chemical 2007 275 167-173



24



231 75ndash81








362










1993







195


30 341


25















2002 45 180


40 587






9750-8


1977




3958


1982 4 411-18

26


Catal B 1996 11 L29-L35


B 1996 11 L11-L18


Environ 2008 84 678-683


sons Newyork 1982


2797






Trans 1998 94 1875


1998 36 55-97


1963 110 23





1997 9 670






27






67


1987 17 249











2008112 291-298



A1999 176 27



2001 44 221



A2001 214 273




28


J Phys Chem B 2003 107 497




99













198730353













29



292 476ndash485



30

Chapter 3

Experimental

31 Material















ii Commercial ZrO2









31

Figure 1


32






323 Commercial ZrO2





















33



























34

Figure 2



35

Figure 3



36

Figure 4



37












Figure 5


38













Figure 6



39



i chemical methods












eluent

















40



41














7 is reduced





in Fig 8











100() minus

=Ci

CfCiX

42

Chapter 3

References





9750-8




2006 110 255



43

Chapter 4A



Catalyst ZrO2























44

Figure 1



Figure 2


Figure 3



a2 b2 2000 at 25 kV

Figure 4


after use

45































46

























1223 K

47

Figure 5









Figure 6





(3) n-Octanol

Figure 7





K (3) 393 K (4) 403 K (5) 413 K


N2) = 40 mlmin)

Figure 8



adsorption

48































49




2

21

O

O

kKpr

Kp=

+ (1)


( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)




2

1 1 1

Or kKp k= + (3)




( )2

1

2

1 1 1

O

r kk Kp

= + (4)










50



























CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51



C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)



C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)






dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)




52

427 Role of oxygen





























O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53


















on the







p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred



54

Chapter 4A

References









Commun 2006 7 24


113 34


1987 9ndash72



311 362




New York 1981









55





374



125


1994 120 127




132

30 Haber J Z Chem 1973 13 241








56

Chapter 4B



Catalyst ZrO2

















57

Figure 1



ZrO2)

Figure 2



58

Figure 3


59





























10

60

Figure 6a and 6b


Figure 4





time 6 hours

Figure 5







61

Figure 7


(6 hrs)


Conversion

Figure 9





hrs)

Figure 8



Figure 10



62

Chapter 4B

References


Research 2005 35 23-28




A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2























64

Figure 1


Figure 2




65



























reactor

66

Table 1


Reaction conditions




Figure 3


Reaction conditions



(900 rpm)

Figure 4


conversions

Reaction conditions



(900 rpm)

67






























68

Figure 7



Figure 5



Reaction conditions



rpm) time (3 h)

Figure 6









69













70

Chapter 4C

References







2005 107ndash108 175





615







2006 110 255


14 Lee T P US Patent 4091044 1978


4278824 1981




2002

71

Chapter 4D














used catalysts












72















benzaldehyde













73

Figure 1


Figure 2








Figure 3







(900rpm) time (1hr)

74
















transfer limitation

4D24 Solvent Effect









75












Rate = -dCdt



















76



Figure 4







Reaction conditions




(900rpm)

Figure 5



Figure 6



77





alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]


alcohol





surface



BzOHb

BzOHaRate

+=

1 (2)




can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)




BzOHcb

BzOHaRate

+= (4)

78




1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)





2BzOHcb

BzOHaRate

+= (6)










as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate


and

BzOH

a

c

a

b

Rate




79

Figure 7



(6)

Figure 8



Figure 9



Figure 10






rmp)

80







7 8 and 10)








1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)



1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)


2Rate a O= (12)




81

22

2

Ocb

OaRate

+= (13)


2

42

Oa

c

a

b

Rate

O+= (14)












gads

ad OkOkdt

Od22 == minus

(15)











82

Figure 11






rmp)

Figure 12


PtZrO2




83



























alcohol oxidation

84

Chapter 4D

References







J C Catal Today 2000 37 143-155


2005 232 432-443






242 224-232


293


A 2005 288 175-184


2004 126 10657-10666






1998 176 321-328

85





71-93

86

Chapter 4E




























87

a b

Figure 1


Figure 2


Figure 3


Figure 4


88

























effect




89

Figure 7






kPa) time (30 min)

Figure 8







Figure 5







time (30

min)

Figure 6






90


constant afterward






time











and gas phase



oxidations







91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)





2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)


ng

n

g

OkTk

OkTkRate

221

221

+=

(2)




Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)



ng

n

g

OK

TOkKRate

2

2

1+= (3)



TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)






92




























93

Figure 9






(900 rpm)

Figure 10






rpm) time (30 min)

Figure 11




Figure 12







94
















Table 1


in aqueous medium

95

Chapter 4E

References




9750-8


Lett1998 55 141


273




A 2005 288 175-184


7 768




139

96

Chapter 4F





























97

Figure 1


and Pt ZrO2 (m)

Figure 2



Figure 3



Figure 4



98



























99

Table 1



Figure 5





100



















101

Figure 6


Figure 7





102

Chapter 4F

References





008-9750-8


103

Chapter 4G

























104

Figure 1


105



a b

c d

e f

h g

106





107




Figure 3


108

























109

Figure 4





Figure 5





agitation 900 rpm

Figure 6





agitation 900 rpm

Figure 7





110
























111

Figure 8





agitation 900 rpm

Figure 9





agitation 900 rpm

Figure 10





rpm

Figure 11




agitation 900 rpm

112

Chapter 4G

References


485





Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review




























114






















wastewater





and PtO ZrO2


and Pt ZrO2 (T)



system is



115














116

116




(hours)


()

Ref


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I


Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)


~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-


372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)


Pt ZrO2(m)

(reduce in

H2 flow)


cyclohexanone

14

401

V

Bi-Pt ZrO2


iii

Abstract






























iv























2008






v

TABLE OF CONTENTS


Acknowledgment ii

Abstract iii
















References 20

vi

TABLE OF CONTENTS



31 Material 30
















References 42

vii

TABLE OF CONTENTS
















References 54







References 62

viii

TABLE OF CONTENTS











References 70














References 84

ix

TABLE OF CONTENTS




by PtZrO2 86










References 95







References 102






x

TABLE OF CONTENTS









References 112


1

Chapter 1

Introduction


























2












environment







lower temperature












3





























4
































5
































6































7








ii In solvent
























8































aqueous solution

9






























10
































11




























12































13

























determining [126]

14

Chapter 2

Literature review




























15
































16
































17
































18
























carbonate species








19










20

Chapter 1amp 2

References


























2005 232 432

21






242 224-232


287-293


Catal A 2005 288 175-184


2004 126 10657-10666



52


2005 7 768




Science 2006 311 362








2006 108 137


22



303-335














Eng J 1999 73 143



24 79




2153



2001 35 2828


181



23


2001 32 151





1998 37 3561



1999 188 311


Today 2000 62 379







381310




1996 29 317




Environ 2000 28113


Chemical 2007 275 167-173



24



231 75ndash81








362










1993







195


30 341


25















2002 45 180


40 587






9750-8


1977




3958


1982 4 411-18

26


Catal B 1996 11 L29-L35


B 1996 11 L11-L18


Environ 2008 84 678-683


sons Newyork 1982


2797






Trans 1998 94 1875


1998 36 55-97


1963 110 23





1997 9 670






27






67


1987 17 249











2008112 291-298



A1999 176 27



2001 44 221



A2001 214 273




28


J Phys Chem B 2003 107 497




99













198730353













29



292 476ndash485



30

Chapter 3

Experimental

31 Material















ii Commercial ZrO2









31

Figure 1


32






323 Commercial ZrO2





















33



























34

Figure 2



35

Figure 3



36

Figure 4



37












Figure 5


38













Figure 6



39



i chemical methods












eluent

















40



41














7 is reduced





in Fig 8











100() minus

=Ci

CfCiX

42

Chapter 3

References





9750-8




2006 110 255



43

Chapter 4A



Catalyst ZrO2























44

Figure 1



Figure 2


Figure 3



a2 b2 2000 at 25 kV

Figure 4


after use

45































46

























1223 K

47

Figure 5









Figure 6





(3) n-Octanol

Figure 7





K (3) 393 K (4) 403 K (5) 413 K


N2) = 40 mlmin)

Figure 8



adsorption

48































49




2

21

O

O

kKpr

Kp=

+ (1)


( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)




2

1 1 1

Or kKp k= + (3)




( )2

1

2

1 1 1

O

r kk Kp

= + (4)










50



























CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51



C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)



C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)






dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)




52

427 Role of oxygen





























O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53


















on the







p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred



54

Chapter 4A

References









Commun 2006 7 24


113 34


1987 9ndash72



311 362




New York 1981









55





374



125


1994 120 127




132

30 Haber J Z Chem 1973 13 241








56

Chapter 4B



Catalyst ZrO2

















57

Figure 1



ZrO2)

Figure 2



58

Figure 3


59





























10

60

Figure 6a and 6b


Figure 4





time 6 hours

Figure 5







61

Figure 7


(6 hrs)


Conversion

Figure 9





hrs)

Figure 8



Figure 10



62

Chapter 4B

References


Research 2005 35 23-28




A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2























64

Figure 1


Figure 2




65



























reactor

66

Table 1


Reaction conditions




Figure 3


Reaction conditions



(900 rpm)

Figure 4


conversions

Reaction conditions



(900 rpm)

67






























68

Figure 7



Figure 5



Reaction conditions



rpm) time (3 h)

Figure 6









69













70

Chapter 4C

References







2005 107ndash108 175





615







2006 110 255


14 Lee T P US Patent 4091044 1978


4278824 1981




2002

71

Chapter 4D














used catalysts












72















benzaldehyde













73

Figure 1


Figure 2








Figure 3







(900rpm) time (1hr)

74
















transfer limitation

4D24 Solvent Effect









75












Rate = -dCdt



















76



Figure 4







Reaction conditions




(900rpm)

Figure 5



Figure 6



77





alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]


alcohol





surface



BzOHb

BzOHaRate

+=

1 (2)




can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)




BzOHcb

BzOHaRate

+= (4)

78




1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)





2BzOHcb

BzOHaRate

+= (6)










as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate


and

BzOH

a

c

a

b

Rate




79

Figure 7



(6)

Figure 8



Figure 9



Figure 10






rmp)

80







7 8 and 10)








1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)



1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)


2Rate a O= (12)




81

22

2

Ocb

OaRate

+= (13)


2

42

Oa

c

a

b

Rate

O+= (14)












gads

ad OkOkdt

Od22 == minus

(15)











82

Figure 11






rmp)

Figure 12


PtZrO2




83



























alcohol oxidation

84

Chapter 4D

References







J C Catal Today 2000 37 143-155


2005 232 432-443






242 224-232


293


A 2005 288 175-184


2004 126 10657-10666






1998 176 321-328

85





71-93

86

Chapter 4E




























87

a b

Figure 1


Figure 2


Figure 3


Figure 4


88

























effect




89

Figure 7






kPa) time (30 min)

Figure 8







Figure 5







time (30

min)

Figure 6






90


constant afterward






time











and gas phase



oxidations







91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)





2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)


ng

n

g

OkTk

OkTkRate

221

221

+=

(2)




Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)



ng

n

g

OK

TOkKRate

2

2

1+= (3)



TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)






92




























93

Figure 9






(900 rpm)

Figure 10






rpm) time (30 min)

Figure 11




Figure 12







94
















Table 1


in aqueous medium

95

Chapter 4E

References




9750-8


Lett1998 55 141


273




A 2005 288 175-184


7 768




139

96

Chapter 4F





























97

Figure 1


and Pt ZrO2 (m)

Figure 2



Figure 3



Figure 4



98



























99

Table 1



Figure 5





100



















101

Figure 6


Figure 7





102

Chapter 4F

References





008-9750-8


103

Chapter 4G

























104

Figure 1


105



a b

c d

e f

h g

106





107




Figure 3


108

























109

Figure 4





Figure 5





agitation 900 rpm

Figure 6





agitation 900 rpm

Figure 7





110
























111

Figure 8





agitation 900 rpm

Figure 9





agitation 900 rpm

Figure 10





rpm

Figure 11




agitation 900 rpm

112

Chapter 4G

References


485





Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review




























114






















wastewater





and PtO ZrO2


and Pt ZrO2 (T)



system is



115














116

116




(hours)


()

Ref


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I


Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)


~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-


372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)


Pt ZrO2(m)

(reduce in

H2 flow)


cyclohexanone

14

401

V

Bi-Pt ZrO2


iv























2008






v

TABLE OF CONTENTS


Acknowledgment ii

Abstract iii
















References 20

vi

TABLE OF CONTENTS



31 Material 30
















References 42

vii

TABLE OF CONTENTS
















References 54







References 62

viii

TABLE OF CONTENTS











References 70














References 84

ix

TABLE OF CONTENTS




by PtZrO2 86










References 95







References 102






x

TABLE OF CONTENTS









References 112


1

Chapter 1

Introduction


























2












environment







lower temperature












3





























4
































5
































6































7








ii In solvent
























8































aqueous solution

9






























10
































11




























12































13

























determining [126]

14

Chapter 2

Literature review




























15
































16
































17
































18
























carbonate species








19










20

Chapter 1amp 2

References


























2005 232 432

21






242 224-232


287-293


Catal A 2005 288 175-184


2004 126 10657-10666



52


2005 7 768




Science 2006 311 362








2006 108 137


22



303-335














Eng J 1999 73 143



24 79




2153



2001 35 2828


181



23


2001 32 151





1998 37 3561



1999 188 311


Today 2000 62 379







381310




1996 29 317




Environ 2000 28113


Chemical 2007 275 167-173



24



231 75ndash81








362










1993







195


30 341


25















2002 45 180


40 587






9750-8


1977




3958


1982 4 411-18

26


Catal B 1996 11 L29-L35


B 1996 11 L11-L18


Environ 2008 84 678-683


sons Newyork 1982


2797






Trans 1998 94 1875


1998 36 55-97


1963 110 23





1997 9 670






27






67


1987 17 249











2008112 291-298



A1999 176 27



2001 44 221



A2001 214 273




28


J Phys Chem B 2003 107 497




99













198730353













29



292 476ndash485



30

Chapter 3

Experimental

31 Material















ii Commercial ZrO2









31

Figure 1


32






323 Commercial ZrO2





















33



























34

Figure 2



35

Figure 3



36

Figure 4



37












Figure 5


38













Figure 6



39



i chemical methods












eluent

















40



41














7 is reduced





in Fig 8











100() minus

=Ci

CfCiX

42

Chapter 3

References





9750-8




2006 110 255



43

Chapter 4A



Catalyst ZrO2























44

Figure 1



Figure 2


Figure 3



a2 b2 2000 at 25 kV

Figure 4


after use

45































46

























1223 K

47

Figure 5









Figure 6





(3) n-Octanol

Figure 7





K (3) 393 K (4) 403 K (5) 413 K


N2) = 40 mlmin)

Figure 8



adsorption

48































49




2

21

O

O

kKpr

Kp=

+ (1)


( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)




2

1 1 1

Or kKp k= + (3)




( )2

1

2

1 1 1

O

r kk Kp

= + (4)










50



























CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51



C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)



C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)






dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)




52

427 Role of oxygen





























O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53


















on the







p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred



54

Chapter 4A

References









Commun 2006 7 24


113 34


1987 9ndash72



311 362




New York 1981









55





374



125


1994 120 127




132

30 Haber J Z Chem 1973 13 241








56

Chapter 4B



Catalyst ZrO2

















57

Figure 1



ZrO2)

Figure 2



58

Figure 3


59





























10

60

Figure 6a and 6b


Figure 4





time 6 hours

Figure 5







61

Figure 7


(6 hrs)


Conversion

Figure 9





hrs)

Figure 8



Figure 10



62

Chapter 4B

References


Research 2005 35 23-28




A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2























64

Figure 1


Figure 2




65



























reactor

66

Table 1


Reaction conditions




Figure 3


Reaction conditions



(900 rpm)

Figure 4


conversions

Reaction conditions



(900 rpm)

67






























68

Figure 7



Figure 5



Reaction conditions



rpm) time (3 h)

Figure 6









69













70

Chapter 4C

References







2005 107ndash108 175





615







2006 110 255


14 Lee T P US Patent 4091044 1978


4278824 1981




2002

71

Chapter 4D














used catalysts












72















benzaldehyde













73

Figure 1


Figure 2








Figure 3







(900rpm) time (1hr)

74
















transfer limitation

4D24 Solvent Effect









75












Rate = -dCdt



















76



Figure 4







Reaction conditions




(900rpm)

Figure 5



Figure 6



77





alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]


alcohol





surface



BzOHb

BzOHaRate

+=

1 (2)




can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)




BzOHcb

BzOHaRate

+= (4)

78




1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)





2BzOHcb

BzOHaRate

+= (6)










as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate


and

BzOH

a

c

a

b

Rate




79

Figure 7



(6)

Figure 8



Figure 9



Figure 10






rmp)

80







7 8 and 10)








1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)



1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)


2Rate a O= (12)




81

22

2

Ocb

OaRate

+= (13)


2

42

Oa

c

a

b

Rate

O+= (14)












gads

ad OkOkdt

Od22 == minus

(15)











82

Figure 11






rmp)

Figure 12


PtZrO2




83



























alcohol oxidation

84

Chapter 4D

References







J C Catal Today 2000 37 143-155


2005 232 432-443






242 224-232


293


A 2005 288 175-184


2004 126 10657-10666






1998 176 321-328

85





71-93

86

Chapter 4E




























87

a b

Figure 1


Figure 2


Figure 3


Figure 4


88

























effect




89

Figure 7






kPa) time (30 min)

Figure 8







Figure 5







time (30

min)

Figure 6






90


constant afterward






time











and gas phase



oxidations







91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)





2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)


ng

n

g

OkTk

OkTkRate

221

221

+=

(2)




Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)



ng

n

g

OK

TOkKRate

2

2

1+= (3)



TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)






92




























93

Figure 9






(900 rpm)

Figure 10






rpm) time (30 min)

Figure 11




Figure 12







94
















Table 1


in aqueous medium

95

Chapter 4E

References




9750-8


Lett1998 55 141


273




A 2005 288 175-184


7 768




139

96

Chapter 4F





























97

Figure 1


and Pt ZrO2 (m)

Figure 2



Figure 3



Figure 4



98



























99

Table 1



Figure 5





100



















101

Figure 6


Figure 7





102

Chapter 4F

References





008-9750-8


103

Chapter 4G

























104

Figure 1


105



a b

c d

e f

h g

106





107




Figure 3


108

























109

Figure 4





Figure 5





agitation 900 rpm

Figure 6





agitation 900 rpm

Figure 7





110
























111

Figure 8





agitation 900 rpm

Figure 9





agitation 900 rpm

Figure 10





rpm

Figure 11




agitation 900 rpm

112

Chapter 4G

References


485





Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review




























114






















wastewater





and PtO ZrO2


and Pt ZrO2 (T)



system is



115














116

116




(hours)


()

Ref


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I


Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)


~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-


372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)


Pt ZrO2(m)

(reduce in

H2 flow)


cyclohexanone

14

401

V

Bi-Pt ZrO2


v

TABLE OF CONTENTS


Acknowledgment ii

Abstract iii
















References 20

vi

TABLE OF CONTENTS



31 Material 30
















References 42

vii

TABLE OF CONTENTS
















References 54







References 62

viii

TABLE OF CONTENTS











References 70














References 84

ix

TABLE OF CONTENTS




by PtZrO2 86










References 95







References 102






x

TABLE OF CONTENTS









References 112


1

Chapter 1

Introduction


























2












environment







lower temperature












3





























4
































5
































6































7








ii In solvent
























8































aqueous solution

9






























10
































11




























12































13

























determining [126]

14

Chapter 2

Literature review




























15
































16
































17
































18
























carbonate species








19










20

Chapter 1amp 2

References


























2005 232 432

21






242 224-232


287-293


Catal A 2005 288 175-184


2004 126 10657-10666



52


2005 7 768




Science 2006 311 362








2006 108 137


22



303-335














Eng J 1999 73 143



24 79




2153



2001 35 2828


181



23


2001 32 151





1998 37 3561



1999 188 311


Today 2000 62 379







381310




1996 29 317




Environ 2000 28113


Chemical 2007 275 167-173



24



231 75ndash81








362










1993







195


30 341


25















2002 45 180


40 587






9750-8


1977




3958


1982 4 411-18

26


Catal B 1996 11 L29-L35


B 1996 11 L11-L18


Environ 2008 84 678-683


sons Newyork 1982


2797






Trans 1998 94 1875


1998 36 55-97


1963 110 23





1997 9 670






27






67


1987 17 249











2008112 291-298



A1999 176 27



2001 44 221



A2001 214 273




28


J Phys Chem B 2003 107 497




99













198730353













29



292 476ndash485



30

Chapter 3

Experimental

31 Material















ii Commercial ZrO2









31

Figure 1


32






323 Commercial ZrO2





















33



























34

Figure 2



35

Figure 3



36

Figure 4



37












Figure 5


38













Figure 6



39



i chemical methods












eluent

















40



41














7 is reduced





in Fig 8











100() minus

=Ci

CfCiX

42

Chapter 3

References





9750-8




2006 110 255



43

Chapter 4A



Catalyst ZrO2























44

Figure 1



Figure 2


Figure 3



a2 b2 2000 at 25 kV

Figure 4


after use

45































46

























1223 K

47

Figure 5









Figure 6





(3) n-Octanol

Figure 7





K (3) 393 K (4) 403 K (5) 413 K


N2) = 40 mlmin)

Figure 8



adsorption

48































49




2

21

O

O

kKpr

Kp=

+ (1)


( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)




2

1 1 1

Or kKp k= + (3)




( )2

1

2

1 1 1

O

r kk Kp

= + (4)










50



























CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51



C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)



C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)






dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)




52

427 Role of oxygen





























O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53


















on the







p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred



54

Chapter 4A

References









Commun 2006 7 24


113 34


1987 9ndash72



311 362




New York 1981









55





374



125


1994 120 127




132

30 Haber J Z Chem 1973 13 241








56

Chapter 4B



Catalyst ZrO2

















57

Figure 1



ZrO2)

Figure 2



58

Figure 3


59





























10

60

Figure 6a and 6b


Figure 4





time 6 hours

Figure 5







61

Figure 7


(6 hrs)


Conversion

Figure 9





hrs)

Figure 8



Figure 10



62

Chapter 4B

References


Research 2005 35 23-28




A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2























64

Figure 1


Figure 2




65



























reactor

66

Table 1


Reaction conditions




Figure 3


Reaction conditions



(900 rpm)

Figure 4


conversions

Reaction conditions



(900 rpm)

67






























68

Figure 7



Figure 5



Reaction conditions



rpm) time (3 h)

Figure 6









69













70

Chapter 4C

References







2005 107ndash108 175





615







2006 110 255


14 Lee T P US Patent 4091044 1978


4278824 1981




2002

71

Chapter 4D














used catalysts












72















benzaldehyde













73

Figure 1


Figure 2








Figure 3







(900rpm) time (1hr)

74
















transfer limitation

4D24 Solvent Effect









75












Rate = -dCdt



















76



Figure 4







Reaction conditions




(900rpm)

Figure 5



Figure 6



77





alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]


alcohol





surface



BzOHb

BzOHaRate

+=

1 (2)




can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)




BzOHcb

BzOHaRate

+= (4)

78




1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)





2BzOHcb

BzOHaRate

+= (6)










as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate


and

BzOH

a

c

a

b

Rate




79

Figure 7



(6)

Figure 8



Figure 9



Figure 10






rmp)

80







7 8 and 10)








1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)



1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)


2Rate a O= (12)




81

22

2

Ocb

OaRate

+= (13)


2

42

Oa

c

a

b

Rate

O+= (14)












gads

ad OkOkdt

Od22 == minus

(15)











82

Figure 11






rmp)

Figure 12


PtZrO2




83



























alcohol oxidation

84

Chapter 4D

References







J C Catal Today 2000 37 143-155


2005 232 432-443






242 224-232


293


A 2005 288 175-184


2004 126 10657-10666






1998 176 321-328

85





71-93

86

Chapter 4E




























87

a b

Figure 1


Figure 2


Figure 3


Figure 4


88

























effect




89

Figure 7






kPa) time (30 min)

Figure 8







Figure 5







time (30

min)

Figure 6






90


constant afterward






time











and gas phase



oxidations







91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)





2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)


ng

n

g

OkTk

OkTkRate

221

221

+=

(2)




Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)



ng

n

g

OK

TOkKRate

2

2

1+= (3)



TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)






92




























93

Figure 9






(900 rpm)

Figure 10






rpm) time (30 min)

Figure 11




Figure 12







94
















Table 1


in aqueous medium

95

Chapter 4E

References




9750-8


Lett1998 55 141


273




A 2005 288 175-184


7 768




139

96

Chapter 4F





























97

Figure 1


and Pt ZrO2 (m)

Figure 2



Figure 3



Figure 4



98



























99

Table 1



Figure 5





100



















101

Figure 6


Figure 7





102

Chapter 4F

References





008-9750-8


103

Chapter 4G

























104

Figure 1


105



a b

c d

e f

h g

106





107




Figure 3


108

























109

Figure 4





Figure 5





agitation 900 rpm

Figure 6





agitation 900 rpm

Figure 7





110
























111

Figure 8





agitation 900 rpm

Figure 9





agitation 900 rpm

Figure 10





rpm

Figure 11




agitation 900 rpm

112

Chapter 4G

References


485





Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review




























114






















wastewater





and PtO ZrO2


and Pt ZrO2 (T)



system is



115














116

116




(hours)


()

Ref


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I


Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)


~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-


372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)


Pt ZrO2(m)

(reduce in

H2 flow)


cyclohexanone

14

401

V

Bi-Pt ZrO2


vi

TABLE OF CONTENTS



31 Material 30
















References 42

vii

TABLE OF CONTENTS
















References 54







References 62

viii

TABLE OF CONTENTS











References 70














References 84

ix

TABLE OF CONTENTS




by PtZrO2 86










References 95







References 102






x

TABLE OF CONTENTS









References 112


1

Chapter 1

Introduction


























2












environment







lower temperature












3





























4
































5
































6































7








ii In solvent
























8































aqueous solution

9






























10
































11




























12































13

























determining [126]

14

Chapter 2

Literature review




























15
































16
































17
































18
























carbonate species








19










20

Chapter 1amp 2

References


























2005 232 432

21






242 224-232


287-293


Catal A 2005 288 175-184


2004 126 10657-10666



52


2005 7 768




Science 2006 311 362








2006 108 137


22



303-335














Eng J 1999 73 143



24 79




2153



2001 35 2828


181



23


2001 32 151





1998 37 3561



1999 188 311


Today 2000 62 379







381310




1996 29 317




Environ 2000 28113


Chemical 2007 275 167-173



24



231 75ndash81








362










1993







195


30 341


25















2002 45 180


40 587






9750-8


1977




3958


1982 4 411-18

26


Catal B 1996 11 L29-L35


B 1996 11 L11-L18


Environ 2008 84 678-683


sons Newyork 1982


2797






Trans 1998 94 1875


1998 36 55-97


1963 110 23





1997 9 670






27






67


1987 17 249











2008112 291-298



A1999 176 27



2001 44 221



A2001 214 273




28


J Phys Chem B 2003 107 497




99













198730353













29



292 476ndash485



30

Chapter 3

Experimental

31 Material















ii Commercial ZrO2









31

Figure 1


32






323 Commercial ZrO2





















33



























34

Figure 2



35

Figure 3



36

Figure 4



37












Figure 5


38













Figure 6



39



i chemical methods












eluent

















40



41














7 is reduced





in Fig 8











100() minus

=Ci

CfCiX

42

Chapter 3

References





9750-8




2006 110 255



43

Chapter 4A



Catalyst ZrO2























44

Figure 1



Figure 2


Figure 3



a2 b2 2000 at 25 kV

Figure 4


after use

45































46

























1223 K

47

Figure 5









Figure 6





(3) n-Octanol

Figure 7





K (3) 393 K (4) 403 K (5) 413 K


N2) = 40 mlmin)

Figure 8



adsorption

48































49




2

21

O

O

kKpr

Kp=

+ (1)


( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)




2

1 1 1

Or kKp k= + (3)




( )2

1

2

1 1 1

O

r kk Kp

= + (4)










50



























CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51



C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)



C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)






dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)




52

427 Role of oxygen





























O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53


















on the







p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred



54

Chapter 4A

References









Commun 2006 7 24


113 34


1987 9ndash72



311 362




New York 1981









55





374



125


1994 120 127




132

30 Haber J Z Chem 1973 13 241








56

Chapter 4B



Catalyst ZrO2

















57

Figure 1



ZrO2)

Figure 2



58

Figure 3


59





























10

60

Figure 6a and 6b


Figure 4





time 6 hours

Figure 5







61

Figure 7


(6 hrs)


Conversion

Figure 9





hrs)

Figure 8



Figure 10



62

Chapter 4B

References


Research 2005 35 23-28




A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2























64

Figure 1


Figure 2




65



























reactor

66

Table 1


Reaction conditions




Figure 3


Reaction conditions



(900 rpm)

Figure 4


conversions

Reaction conditions



(900 rpm)

67






























68

Figure 7



Figure 5



Reaction conditions



rpm) time (3 h)

Figure 6









69













70

Chapter 4C

References







2005 107ndash108 175





615







2006 110 255


14 Lee T P US Patent 4091044 1978


4278824 1981




2002

71

Chapter 4D














used catalysts












72















benzaldehyde













73

Figure 1


Figure 2








Figure 3







(900rpm) time (1hr)

74
















transfer limitation

4D24 Solvent Effect









75












Rate = -dCdt



















76



Figure 4







Reaction conditions




(900rpm)

Figure 5



Figure 6



77





alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]


alcohol





surface



BzOHb

BzOHaRate

+=

1 (2)




can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)




BzOHcb

BzOHaRate

+= (4)

78




1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)





2BzOHcb

BzOHaRate

+= (6)










as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate


and

BzOH

a

c

a

b

Rate




79

Figure 7



(6)

Figure 8



Figure 9



Figure 10






rmp)

80







7 8 and 10)








1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)



1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)


2Rate a O= (12)




81

22

2

Ocb

OaRate

+= (13)


2

42

Oa

c

a

b

Rate

O+= (14)












gads

ad OkOkdt

Od22 == minus

(15)











82

Figure 11






rmp)

Figure 12


PtZrO2




83



























alcohol oxidation

84

Chapter 4D

References







J C Catal Today 2000 37 143-155


2005 232 432-443






242 224-232


293


A 2005 288 175-184


2004 126 10657-10666






1998 176 321-328

85





71-93

86

Chapter 4E




























87

a b

Figure 1


Figure 2


Figure 3


Figure 4


88

























effect




89

Figure 7






kPa) time (30 min)

Figure 8







Figure 5







time (30

min)

Figure 6






90


constant afterward






time











and gas phase



oxidations







91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)





2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)


ng

n

g

OkTk

OkTkRate

221

221

+=

(2)




Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)



ng

n

g

OK

TOkKRate

2

2

1+= (3)



TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)






92




























93

Figure 9






(900 rpm)

Figure 10






rpm) time (30 min)

Figure 11




Figure 12







94
















Table 1


in aqueous medium

95

Chapter 4E

References




9750-8


Lett1998 55 141


273




A 2005 288 175-184


7 768




139

96

Chapter 4F





























97

Figure 1


and Pt ZrO2 (m)

Figure 2



Figure 3



Figure 4



98



























99

Table 1



Figure 5





100



















101

Figure 6


Figure 7





102

Chapter 4F

References





008-9750-8


103

Chapter 4G

























104

Figure 1


105



a b

c d

e f

h g

106





107




Figure 3


108

























109

Figure 4





Figure 5





agitation 900 rpm

Figure 6





agitation 900 rpm

Figure 7





110
























111

Figure 8





agitation 900 rpm

Figure 9





agitation 900 rpm

Figure 10





rpm

Figure 11




agitation 900 rpm

112

Chapter 4G

References


485





Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review




























114






















wastewater





and PtO ZrO2


and Pt ZrO2 (T)



system is



115














116

116




(hours)


()

Ref


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I


Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)


~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-


372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)


Pt ZrO2(m)

(reduce in

H2 flow)


cyclohexanone

14

401

V

Bi-Pt ZrO2


vii

TABLE OF CONTENTS
















References 54







References 62

viii

TABLE OF CONTENTS











References 70














References 84

ix

TABLE OF CONTENTS




by PtZrO2 86










References 95







References 102






x

TABLE OF CONTENTS









References 112


1

Chapter 1

Introduction


























2












environment







lower temperature












3





























4
































5
































6































7








ii In solvent
























8































aqueous solution

9






























10
































11




























12































13

























determining [126]

14

Chapter 2

Literature review




























15
































16
































17
































18
























carbonate species








19










20

Chapter 1amp 2

References


























2005 232 432

21






242 224-232


287-293


Catal A 2005 288 175-184


2004 126 10657-10666



52


2005 7 768




Science 2006 311 362








2006 108 137


22



303-335














Eng J 1999 73 143



24 79




2153



2001 35 2828


181



23


2001 32 151





1998 37 3561



1999 188 311


Today 2000 62 379







381310




1996 29 317




Environ 2000 28113


Chemical 2007 275 167-173



24



231 75ndash81








362










1993







195


30 341


25















2002 45 180


40 587






9750-8


1977




3958


1982 4 411-18

26


Catal B 1996 11 L29-L35


B 1996 11 L11-L18


Environ 2008 84 678-683


sons Newyork 1982


2797






Trans 1998 94 1875


1998 36 55-97


1963 110 23





1997 9 670






27






67


1987 17 249











2008112 291-298



A1999 176 27



2001 44 221



A2001 214 273




28


J Phys Chem B 2003 107 497




99













198730353













29



292 476ndash485



30

Chapter 3

Experimental

31 Material















ii Commercial ZrO2









31

Figure 1


32






323 Commercial ZrO2





















33



























34

Figure 2



35

Figure 3



36

Figure 4



37












Figure 5


38













Figure 6



39



i chemical methods












eluent

















40



41














7 is reduced





in Fig 8











100() minus

=Ci

CfCiX

42

Chapter 3

References





9750-8




2006 110 255



43

Chapter 4A



Catalyst ZrO2























44

Figure 1



Figure 2


Figure 3



a2 b2 2000 at 25 kV

Figure 4


after use

45































46

























1223 K

47

Figure 5









Figure 6





(3) n-Octanol

Figure 7





K (3) 393 K (4) 403 K (5) 413 K


N2) = 40 mlmin)

Figure 8



adsorption

48































49




2

21

O

O

kKpr

Kp=

+ (1)


( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)




2

1 1 1

Or kKp k= + (3)




( )2

1

2

1 1 1

O

r kk Kp

= + (4)










50



























CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51



C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)



C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)






dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)




52

427 Role of oxygen





























O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53


















on the







p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred



54

Chapter 4A

References









Commun 2006 7 24


113 34


1987 9ndash72



311 362




New York 1981









55





374



125


1994 120 127




132

30 Haber J Z Chem 1973 13 241








56

Chapter 4B



Catalyst ZrO2

















57

Figure 1



ZrO2)

Figure 2



58

Figure 3


59





























10

60

Figure 6a and 6b


Figure 4





time 6 hours

Figure 5







61

Figure 7


(6 hrs)


Conversion

Figure 9





hrs)

Figure 8



Figure 10



62

Chapter 4B

References


Research 2005 35 23-28




A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2























64

Figure 1


Figure 2




65



























reactor

66

Table 1


Reaction conditions




Figure 3


Reaction conditions



(900 rpm)

Figure 4


conversions

Reaction conditions



(900 rpm)

67






























68

Figure 7



Figure 5



Reaction conditions



rpm) time (3 h)

Figure 6









69













70

Chapter 4C

References







2005 107ndash108 175





615







2006 110 255


14 Lee T P US Patent 4091044 1978


4278824 1981




2002

71

Chapter 4D














used catalysts












72















benzaldehyde













73

Figure 1


Figure 2








Figure 3







(900rpm) time (1hr)

74
















transfer limitation

4D24 Solvent Effect









75












Rate = -dCdt



















76



Figure 4







Reaction conditions




(900rpm)

Figure 5



Figure 6



77





alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]


alcohol





surface



BzOHb

BzOHaRate

+=

1 (2)




can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)




BzOHcb

BzOHaRate

+= (4)

78




1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)





2BzOHcb

BzOHaRate

+= (6)










as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate


and

BzOH

a

c

a

b

Rate




79

Figure 7



(6)

Figure 8



Figure 9



Figure 10






rmp)

80







7 8 and 10)








1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)



1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)


2Rate a O= (12)




81

22

2

Ocb

OaRate

+= (13)


2

42

Oa

c

a

b

Rate

O+= (14)












gads

ad OkOkdt

Od22 == minus

(15)











82

Figure 11






rmp)

Figure 12


PtZrO2




83



























alcohol oxidation

84

Chapter 4D

References







J C Catal Today 2000 37 143-155


2005 232 432-443






242 224-232


293


A 2005 288 175-184


2004 126 10657-10666






1998 176 321-328

85





71-93

86

Chapter 4E




























87

a b

Figure 1


Figure 2


Figure 3


Figure 4


88

























effect




89

Figure 7






kPa) time (30 min)

Figure 8







Figure 5







time (30

min)

Figure 6






90


constant afterward






time











and gas phase



oxidations







91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)





2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)


ng

n

g

OkTk

OkTkRate

221

221

+=

(2)




Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)



ng

n

g

OK

TOkKRate

2

2

1+= (3)



TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)






92




























93

Figure 9






(900 rpm)

Figure 10






rpm) time (30 min)

Figure 11




Figure 12







94
















Table 1


in aqueous medium

95

Chapter 4E

References




9750-8


Lett1998 55 141


273




A 2005 288 175-184


7 768




139

96

Chapter 4F





























97

Figure 1


and Pt ZrO2 (m)

Figure 2



Figure 3



Figure 4



98



























99

Table 1



Figure 5





100



















101

Figure 6


Figure 7





102

Chapter 4F

References





008-9750-8


103

Chapter 4G

























104

Figure 1


105



a b

c d

e f

h g

106





107




Figure 3


108

























109

Figure 4





Figure 5





agitation 900 rpm

Figure 6





agitation 900 rpm

Figure 7





110
























111

Figure 8





agitation 900 rpm

Figure 9





agitation 900 rpm

Figure 10





rpm

Figure 11




agitation 900 rpm

112

Chapter 4G

References


485





Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review




























114






















wastewater





and PtO ZrO2


and Pt ZrO2 (T)



system is



115














116

116




(hours)


()

Ref


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I


Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)


~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-


372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)


Pt ZrO2(m)

(reduce in

H2 flow)


cyclohexanone

14

401

V

Bi-Pt ZrO2


viii

TABLE OF CONTENTS











References 70














References 84

ix

TABLE OF CONTENTS




by PtZrO2 86










References 95







References 102






x

TABLE OF CONTENTS









References 112


1

Chapter 1

Introduction


























2












environment







lower temperature












3





























4
































5
































6































7








ii In solvent
























8































aqueous solution

9






























10
































11




























12































13

























determining [126]

14

Chapter 2

Literature review




























15
































16
































17
































18
























carbonate species








19










20

Chapter 1amp 2

References


























2005 232 432

21






242 224-232


287-293


Catal A 2005 288 175-184


2004 126 10657-10666



52


2005 7 768




Science 2006 311 362








2006 108 137


22



303-335














Eng J 1999 73 143



24 79




2153



2001 35 2828


181



23


2001 32 151





1998 37 3561



1999 188 311


Today 2000 62 379







381310




1996 29 317




Environ 2000 28113


Chemical 2007 275 167-173



24



231 75ndash81








362










1993







195


30 341


25















2002 45 180


40 587






9750-8


1977




3958


1982 4 411-18

26


Catal B 1996 11 L29-L35


B 1996 11 L11-L18


Environ 2008 84 678-683


sons Newyork 1982


2797






Trans 1998 94 1875


1998 36 55-97


1963 110 23





1997 9 670






27






67


1987 17 249











2008112 291-298



A1999 176 27



2001 44 221



A2001 214 273




28


J Phys Chem B 2003 107 497




99













198730353













29



292 476ndash485



30

Chapter 3

Experimental

31 Material















ii Commercial ZrO2









31

Figure 1


32






323 Commercial ZrO2





















33



























34

Figure 2



35

Figure 3



36

Figure 4



37












Figure 5


38













Figure 6



39



i chemical methods












eluent

















40



41














7 is reduced





in Fig 8











100() minus

=Ci

CfCiX

42

Chapter 3

References





9750-8




2006 110 255



43

Chapter 4A



Catalyst ZrO2























44

Figure 1



Figure 2


Figure 3



a2 b2 2000 at 25 kV

Figure 4


after use

45































46

























1223 K

47

Figure 5









Figure 6





(3) n-Octanol

Figure 7





K (3) 393 K (4) 403 K (5) 413 K


N2) = 40 mlmin)

Figure 8



adsorption

48































49




2

21

O

O

kKpr

Kp=

+ (1)


( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)




2

1 1 1

Or kKp k= + (3)




( )2

1

2

1 1 1

O

r kk Kp

= + (4)










50



























CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51



C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)



C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)






dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)




52

427 Role of oxygen





























O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53


















on the







p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred



54

Chapter 4A

References









Commun 2006 7 24


113 34


1987 9ndash72



311 362




New York 1981









55





374



125


1994 120 127




132

30 Haber J Z Chem 1973 13 241








56

Chapter 4B



Catalyst ZrO2

















57

Figure 1



ZrO2)

Figure 2



58

Figure 3


59





























10

60

Figure 6a and 6b


Figure 4





time 6 hours

Figure 5







61

Figure 7


(6 hrs)


Conversion

Figure 9





hrs)

Figure 8



Figure 10



62

Chapter 4B

References


Research 2005 35 23-28




A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2























64

Figure 1


Figure 2




65



























reactor

66

Table 1


Reaction conditions




Figure 3


Reaction conditions



(900 rpm)

Figure 4


conversions

Reaction conditions



(900 rpm)

67






























68

Figure 7



Figure 5



Reaction conditions



rpm) time (3 h)

Figure 6









69













70

Chapter 4C

References







2005 107ndash108 175





615







2006 110 255


14 Lee T P US Patent 4091044 1978


4278824 1981




2002

71

Chapter 4D














used catalysts












72















benzaldehyde













73

Figure 1


Figure 2








Figure 3







(900rpm) time (1hr)

74
















transfer limitation

4D24 Solvent Effect









75












Rate = -dCdt



















76



Figure 4







Reaction conditions




(900rpm)

Figure 5



Figure 6



77





alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]


alcohol





surface



BzOHb

BzOHaRate

+=

1 (2)




can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)




BzOHcb

BzOHaRate

+= (4)

78




1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)





2BzOHcb

BzOHaRate

+= (6)










as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate


and

BzOH

a

c

a

b

Rate




79

Figure 7



(6)

Figure 8



Figure 9



Figure 10






rmp)

80







7 8 and 10)








1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)



1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)


2Rate a O= (12)




81

22

2

Ocb

OaRate

+= (13)


2

42

Oa

c

a

b

Rate

O+= (14)












gads

ad OkOkdt

Od22 == minus

(15)











82

Figure 11






rmp)

Figure 12


PtZrO2




83



























alcohol oxidation

84

Chapter 4D

References







J C Catal Today 2000 37 143-155


2005 232 432-443






242 224-232


293


A 2005 288 175-184


2004 126 10657-10666






1998 176 321-328

85





71-93

86

Chapter 4E




























87

a b

Figure 1


Figure 2


Figure 3


Figure 4


88

























effect




89

Figure 7






kPa) time (30 min)

Figure 8







Figure 5







time (30

min)

Figure 6






90


constant afterward






time











and gas phase



oxidations







91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)





2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)


ng

n

g

OkTk

OkTkRate

221

221

+=

(2)




Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)



ng

n

g

OK

TOkKRate

2

2

1+= (3)



TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)






92




























93

Figure 9






(900 rpm)

Figure 10






rpm) time (30 min)

Figure 11




Figure 12







94
















Table 1


in aqueous medium

95

Chapter 4E

References




9750-8


Lett1998 55 141


273




A 2005 288 175-184


7 768




139

96

Chapter 4F





























97

Figure 1


and Pt ZrO2 (m)

Figure 2



Figure 3



Figure 4



98



























99

Table 1



Figure 5





100



















101

Figure 6


Figure 7





102

Chapter 4F

References





008-9750-8


103

Chapter 4G

























104

Figure 1


105



a b

c d

e f

h g

106





107




Figure 3


108

























109

Figure 4





Figure 5





agitation 900 rpm

Figure 6





agitation 900 rpm

Figure 7





110
























111

Figure 8





agitation 900 rpm

Figure 9





agitation 900 rpm

Figure 10





rpm

Figure 11




agitation 900 rpm

112

Chapter 4G

References


485





Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review




























114






















wastewater





and PtO ZrO2


and Pt ZrO2 (T)



system is



115














116

116




(hours)


()

Ref


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I


Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)


~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-


372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)


Pt ZrO2(m)

(reduce in

H2 flow)


cyclohexanone

14

401

V

Bi-Pt ZrO2


ix

TABLE OF CONTENTS




by PtZrO2 86










References 95







References 102






x

TABLE OF CONTENTS









References 112


1

Chapter 1

Introduction


























2












environment







lower temperature












3





























4
































5
































6































7








ii In solvent
























8































aqueous solution

9






























10
































11




























12































13

























determining [126]

14

Chapter 2

Literature review




























15
































16
































17
































18
























carbonate species








19










20

Chapter 1amp 2

References


























2005 232 432

21






242 224-232


287-293


Catal A 2005 288 175-184


2004 126 10657-10666



52


2005 7 768




Science 2006 311 362








2006 108 137


22



303-335














Eng J 1999 73 143



24 79




2153



2001 35 2828


181



23


2001 32 151





1998 37 3561



1999 188 311


Today 2000 62 379







381310




1996 29 317




Environ 2000 28113


Chemical 2007 275 167-173



24



231 75ndash81








362










1993







195


30 341


25















2002 45 180


40 587






9750-8


1977




3958


1982 4 411-18

26


Catal B 1996 11 L29-L35


B 1996 11 L11-L18


Environ 2008 84 678-683


sons Newyork 1982


2797






Trans 1998 94 1875


1998 36 55-97


1963 110 23





1997 9 670






27






67


1987 17 249











2008112 291-298



A1999 176 27



2001 44 221



A2001 214 273




28


J Phys Chem B 2003 107 497




99













198730353













29



292 476ndash485



30

Chapter 3

Experimental

31 Material















ii Commercial ZrO2









31

Figure 1


32






323 Commercial ZrO2





















33



























34

Figure 2



35

Figure 3



36

Figure 4



37












Figure 5


38













Figure 6



39



i chemical methods












eluent

















40



41














7 is reduced





in Fig 8











100() minus

=Ci

CfCiX

42

Chapter 3

References





9750-8




2006 110 255



43

Chapter 4A



Catalyst ZrO2























44

Figure 1



Figure 2


Figure 3



a2 b2 2000 at 25 kV

Figure 4


after use

45































46

























1223 K

47

Figure 5









Figure 6





(3) n-Octanol

Figure 7





K (3) 393 K (4) 403 K (5) 413 K


N2) = 40 mlmin)

Figure 8



adsorption

48































49




2

21

O

O

kKpr

Kp=

+ (1)


( )

( )

2

2

1

2

1

21

O

O

k Kpr

Kp

=

+

(2)




2

1 1 1

Or kKp k= + (3)




( )2

1

2

1 1 1

O

r kk Kp

= + (4)










50



























CH3CH

2OHrarr CH

3CH

2O

ads+ H

ads (1)

CH3CH

2O

ads+ O

adsrarrCH

3CHO + OH

ads (2)

Hads

+ OHads

rarrH2O (3)

51



C6H

11OHrarrC

6H

11O

ads+ H

ads (4)

C6H

11O

ads + O

adsrarrC

6H

10O + OH

ads (5)

Hads

+ OHads

rarrH2O (6)



C6H

11OHrarrC

6H

11O

ads + H

ads (7)

C6H

11O

adsrarrC

6H

10O + H

ads (8)

Hads

+ Hads

rarrH2

(9)






dehydration pathway

C6H

11OHrarrC

6H

10OH

ads+ H

ads (10)

C6H

10OH

adsrarrC

6H

10 + OH

ads (11)

Hads

+ OHads

rarrH2O (12)




52

427 Role of oxygen





























O2rarr O

2(ads) rarr O2

2- (ads)-2e-rarr 2O

2-(lattice)

53


















on the







p k op k

p op k k Rate

redred2

n

ox

red2

n

redox

+=

where kox and kred



54

Chapter 4A

References









Commun 2006 7 24


113 34


1987 9ndash72



311 362




New York 1981









55





374



125


1994 120 127




132

30 Haber J Z Chem 1973 13 241








56

Chapter 4B



Catalyst ZrO2

















57

Figure 1



ZrO2)

Figure 2



58

Figure 3


59





























10

60

Figure 6a and 6b


Figure 4





time 6 hours

Figure 5







61

Figure 7


(6 hrs)


Conversion

Figure 9





hrs)

Figure 8



Figure 10



62

Chapter 4B

References


Research 2005 35 23-28




A 2005 288 175-184


63

Chapter 4C


Reactant Toluene

Catalyst PtZrO2























64

Figure 1


Figure 2




65



























reactor

66

Table 1


Reaction conditions




Figure 3


Reaction conditions



(900 rpm)

Figure 4


conversions

Reaction conditions



(900 rpm)

67






























68

Figure 7



Figure 5



Reaction conditions



rpm) time (3 h)

Figure 6









69













70

Chapter 4C

References







2005 107ndash108 175





615







2006 110 255


14 Lee T P US Patent 4091044 1978


4278824 1981




2002

71

Chapter 4D














used catalysts












72















benzaldehyde













73

Figure 1


Figure 2








Figure 3







(900rpm) time (1hr)

74
















transfer limitation

4D24 Solvent Effect









75












Rate = -dCdt



















76



Figure 4







Reaction conditions




(900rpm)

Figure 5



Figure 6



77





alcohol (BzOH) as

Rate =

05

2[ ][ ]

1 ]

gkK BzOH O

k BzOH+ [1]


alcohol





surface



BzOHb

BzOHaRate

+=

1 (2)




can be given

ng

n

g

OkBzOHk

OkBzOHkRate

221

221

+=

(3)




BzOHcb

BzOHaRate

+= (4)

78




1 2 2

1 2 2

2

1n

g

nn

g

K BzOH K O

kK K BzOH ORate

+ +

=

(5)





2BzOHcb

BzOHaRate

+= (6)










as follow

BzOH

a

b

aRate

BzOH+=

1 (7) [E-R model]

BzOH

a

c

a

b

Rate


and

BzOH

a

c

a

b

Rate




79

Figure 7



(6)

Figure 8



Figure 9



Figure 10






rmp)

80







7 8 and 10)








1 2 2

2

1 2 21

g

g

kK K BzOH ORate

K BzOH K O

=

+ +

(10)



1 2 2

2

11

gkK K BzOH O

RateK BzOH

=+

(11)


2Rate a O= (12)




81

22

2

Ocb

OaRate

+= (13)


2

42

Oa

c

a

b

Rate

O+= (14)












gads

ad OkOkdt

Od22 == minus

(15)











82

Figure 11






rmp)

Figure 12


PtZrO2




83



























alcohol oxidation

84

Chapter 4D

References







J C Catal Today 2000 37 143-155


2005 232 432-443






242 224-232


293


A 2005 288 175-184


2004 126 10657-10666






1998 176 321-328

85





71-93

86

Chapter 4E




























87

a b

Figure 1


Figure 2


Figure 3


Figure 4


88

























effect




89

Figure 7






kPa) time (30 min)

Figure 8







Figure 5







time (30

min)

Figure 6






90


constant afterward






time











and gas phase



oxidations







91

2221

221

1n

n

g

gOKTK

OTKkKRate

++= (1)





2Tcb

TaRate

+= (1a) or

22

2

Ocb

OaRate

+= (1b)


ng

n

g

OkTk

OkTkRate

221

221

+=

(2)




Tcb

TaRate

+= (2a) or

ng

n

g

Ocb

OaRate

2

2

+= (2b)



ng

n

g

OK

TOkKRate

2

2

1+= (3)



TaRate = (3a) or

ng

n

g

Ob

OaRate

2

2

1+= (3b)






92




























93

Figure 9






(900 rpm)

Figure 10






rpm) time (30 min)

Figure 11




Figure 12







94
















Table 1


in aqueous medium

95

Chapter 4E

References




9750-8


Lett1998 55 141


273




A 2005 288 175-184


7 768




139

96

Chapter 4F





























97

Figure 1


and Pt ZrO2 (m)

Figure 2



Figure 3



Figure 4



98



























99

Table 1



Figure 5





100



















101

Figure 6


Figure 7





102

Chapter 4F

References





008-9750-8


103

Chapter 4G

























104

Figure 1


105



a b

c d

e f

h g

106





107




Figure 3


108

























109

Figure 4





Figure 5





agitation 900 rpm

Figure 6





agitation 900 rpm

Figure 7





110
























111

Figure 8





agitation 900 rpm

Figure 9





agitation 900 rpm

Figure 10





rpm

Figure 11




agitation 900 rpm

112

Chapter 4G

References


485





Environ 2008 84 678-683


9750-8




Catal A 2005 288 175-184

113

Chapter 5

Conclusion review




























114






















wastewater





and PtO ZrO2


and Pt ZrO2 (T)



system is



115














116

116




(hours)


()

Ref


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

236

152

115

I

III


Benzyl alcohol

n-Octanol

Cyclohexanone

Benzaldehyde

Octanal

367

222

197

I


Benzoic acid

23

887

VII

Pt ZrO2

(used

without

reduction)


~100 II

Pt ZrO2

(reduce in

H2 flow)

-

-

3

7

Toluene

Toluene

Benzoic acid

Benzaldehyde

Benzoic acid

Benzyl benzoate

Trans-stelbene

4-methyl-2-


372

22

296

34

53

108

IV

Pt ZrO2

(reduce in

H2 flow)


Pt ZrO2(m)

(reduce in

H2 flow)


cyclohexanone

14

401

V

Bi-Pt ZrO2


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INVESTIGATING THE ACTIVITY OF ZIRCONIA AS A CATALYST …