A Process Report on Comparative Study of Production of Isoamyl Acetate by Fischer Esterification Using Different Catalysts

In the name of Allah, The most Beneficent, the most

Gracious.

A PROCESS REPORT ON COMPARATIVE STUDY OF PRODUCTION OF

ISOAMYL ACETATE BY FISCHER ESTERIFICATION USING DIFFERENT CATALYSTS

Submitted To

Institute of Chemical Engineering &Technology

University Of Punjab Lahore

In Partial Fulfillment of B.Sc. Engineering (Chemical)

By

Sajjad Rasool Chaudhry (M08-PG12) Ali Rafiq (M08-PG11) Ibrar ur Rehman Faisal (M08-PG09) Babar Rafiq (M08-PG10)

(Session 2007-2011)

Supervisor: Prof. Dr. Syed Zahoor ul Hassan Rizvi

Faculty of Engineering & Technology

Institute of Chemical Engineering & Technology University of the Punjab Quid-e-Azam Campus, Lahore, Pakistan

A PROCESS REPORT ON COMPARATIVE STUDY OF PRODUCTION OF ISOAMYL

ACETATE BY FISCHER ESTERIFICATION USING DIFFERENT CATALYSTS

This Process Report is submitted to the Institute of Chemical Engineering &

Technology, University of the Punjab Lahore, Pakistan. As per requirement for the

partial fulfillment of the B.Sc. Engineering (CHEMICAL)

Approved by:

------------------------- Project Supervisor

Prof. Dr. Syed Zahoor ul Hassan Rizvi

Faculty of Engineering & Technology Institute of Chemical Engineering & Technology

University of the Punjab Quid-e-Azam Campus, Lahore, Pakistan

Acknowledgement

Definitely nothing can be done without the will of Allah. Therefore, we are highly thankful to almighty Allah, Who made us able to explore things from His universe.

After that we are thankful to our respectable teacher, Prof. Dr. Syed Zahoor ul Hassan Rizvi who guided us about the rich information of the topic and also for his help as Director; Institute of the Chemical Engineering & Technology. He provided us a great opportunity to work in a best educational environment. No word of indebtedness can ever repay the debt, we owe to hem. Moreover we are very thankful to Dr. Javed Iqbal for his continuous help and kindness throughout the research work. The credit, if any, goes to the venerable teachers and error is because of our incompetence because mistakes are a part of learning and we would like to accept the useful suggestions from the worthy teachers. At the end we are thankful to all those who helped us in gathering data and providing information about the concerned project and words are lacking to express our humble obligations to our cherished affectionate parents, who ever remembered us in their prayers and supported us in all respects along the awful avenue to our academic achievements.

Authors

Dedicated To

Our Beloved Parents

And Teachers Whose

Proper Guidance and

Prayers

Made This All Possible

PREFACE

As food technology progresses, its impact on the human diet becomes more evident. The use of preservatives, color additives, and flavoring agents by manufacturers plays an important role in sustaining and extending the quality and quantity of food. Due to the diversity required in food flavors, Isoamyl acetate is the most famous natural identical for banana and pear flavorings.

Iso-amyl acetate is a colorless organic ester of acetic acid and Isoamyl alcohol. The most famous and conventional method of manufacturing Isoamyl acetate has been Fischer Esterification, using an appropriate catalyst and under appropriate conditions. Being a third world country, for Pakistan it’s the need of the hour to design methods for manufacturing chemicals through most economical means, and also reducing high amounts of imports from the developing/developed countries. Keeping in view, all these aspects the authors studied the preparation of Isoamyl acetate on laboratory scale, using three different types of catalyst, to choose the most appropriate one. Here, the “appropriate catalyst” signifies the catalyst which can give the maximum yield with maximum purity and minimum cost. Over the years, various catalysts have been tested upon and proven right or wrong for the process.

Though, our research work may not have contributed much to the actual advancement of the commercial use of flavors, however we have tried to expose the role of the catalyst on a very important and most commonly used flavor in food industry.

TABLE OF CONTENTS CHAPTER 1: LITERATURE REVIEW 1.1 ESTERS ................................................................................................................................................ 10

1.2 ESTERIFICATION .............................................................................................................................. 11

1.3 TYPES OF ESTERIFICATION ........................................................................................................... 11

1.3.1 BATCH ESTERIFICATION .................................................................................................... 12

1.3.2 CONTINUES ESTERIFICATION ........................................................................................... 12

1.3.3 VAPOR PHASE ESTERIFICATION ....................................................................................... 12

1.3.4 CATALYTIC ESTERIFICATION ........................................................................................... 12

1.4 PROCESS SELECTION FOR ISO-AMYL ACETATE ....................................................................... 12

1.5 FISCHER ESTERIFICATION ............................................................................................................. 13

1.5.1REACTION MECHANISM ...................................................................................................... 14

1.5.2RATE EXPRESSION ............................................................................................................... 16

1.5.3COMPLETING ESTERIFICATION ......................................................................................... 18

1.5.4PROS & CONS OF FISCHER ESTERIFICATION ..................................................................... 18

CHAPTER 2: ISOAMYL ACETATE 2.1 SIGNIFICANCE ................................................................................................................................... 21

2.2 CHEMISTRY OF AMY ACETATE ..................................................................................................... 23

2.3 CHEMICAL AND PHYSICAL PROPERTIES OF ISOAMYL ACETATE ........................................ 24

2.3.1PHYSICAL DATA ................................................................................................................... 24

2.3.2REACTIVITY .......................................................................................................................... 24

2.3.3FLAMMABILITY .................................................................................................................... 24

2.3.4STORAGE ............................................................................................................................... 25

2.3.5EXPOSURE LIMITS ................................................................................................................ 25

2.3.6SUMMARY OF TOXIC BEHAVIOR ....................................................................................... 25

2.3.7EXPOSURE SOURCES AND CONTROL METHODS ............................................................. 26

2.4 APPLICATIONS .................................................................................................................................. 27

2.5 STATUS IN PAKISTAN ....................................................................................................................... 28

2.6 ISOAMYL ACETATE: THE PAST, THE PRESENT AND THE FUTURE ........................................ 28

CHAPTER 3: RAW MATERIALS & EXPERIMENTATION

3.1 RAW MATERIALS .............................................................................................................................. 31

3.1.1 ISOAMYL ALCOHOL ............................................................................................................ 31

3.1.2 ACETIC ACID/ ETHANOIC ACID ......................................................................................... 34

3.1.3 CATALYST ............................................................................................................................ 35

3.2 EXPERIMENTAL PERFORMANCE .................................................................................................. 40

3.2.1 CHEMICAL REACTION INVOLVED .................................................................................... 40

3.2.2 PROCEDURE .......................................................................................................................... 40

CHAPTER 4: RESULTS & DISCUSSION 4.1 STOICHIOMETRIC CALCULATIONS ............................................................................................. 45

4.1.1 ISOAMYL ALCOHOL ............................................................................................................ 45

4.1.2 ISOAMYL ACETATE ............................................................................................................. 45

4.2 EXPERIMENTAL CALCULATIONS ................................................................................................. 46

4.2.1 AMOUNT OF WATER PRODUCED ....................................................................................... 46

4.2.2 ACTUAL AMOUNT OF ISOAMYL ACETATE ...................................................................... 48

4.2.3 THEORETICALLY PRODUCED AMOUNT OF ISOAMYL ACETATE ................................. 48

4.2.4 PERCENTAGE YIELD ........................................................................................................... 49

4.2.5 LABORATORY TESTS OF ISOAMYL ACETATE ................................................................. 51

4.3 TABLE OF SUMMARY OF RESULTS ............................................................................................... 54

4.4 DISCUSSION ON RESULTS: .............................................................................................................. 54

4.4.1 CONCLUSION ........................................................................................................................ 55

REFERENCES…..…..…………………………………………………………………………...57

Chapter 1 Literature Review

9

Chapter no. 1

LITERATURE REVIEW


10

1.1 Esters [1]

Esters are derivatives of carboxylic acids. They are a class of organic compounds

which, unlike many organics, have pleasant odor.

The process of formation of ester is termed as esterification. Esters are naturally

abundant and readily synthesized, but all have the same following structure,

Several examples of Fischer esterification products has been presented in the table 1

given below.

Ester Structure Fragrance/Flavor Carboxylic Acid Alcohol

Iso-Butyl Formate

HCO2CH2CH(CH3)2 Raspberry essence acetic acid iso-

butanol Propyl Acetate

CH3CO2CH2CH2CH3 Pear essence acetic acid 1-

Propanol Iso-Amyl Acetate

CH3CO2(CH2)2CH(CH3)2 Banana essence formic acid iso-amyl alcohol

Octyl Acetate CH3CO2CH2(CH2)6CH3 Orange essence acetic acid octanol

Benzyl acetate

CH3CO2CH2C6H5 Peach essence acetic acid Benzyl alcohol

Iso-butyl CH3CH2CO2CH2CH(CH3)2 Rum essence propionic acid iso-butyl

Ethyl butyrate

CH3CH2CH2CO2CH2CH Pineapple essence butyric acid alcohol

Methyl butyrate

CH3CH2CH2CO2CH3 ‘Apple like’ essence butyric acid ethanol

Iso-amyl butyrate

CH3CH2CH2CO2(CH2)2 CH(CH3)2

Apricot essence butyric acid methanol

Iso-amyl valerate

CH3CH2CH2CO2(CH2)2 CH(CH3)2

‘real’ Apple essence valeric acid iso-amyl

Methyl anthranilate

H2NC6H4CO2CH3 Grape essence anthranilic acid alcohol

Ethyl laurate CH3(CH2)10CO2CH2CH3 Tuberose essence lauric acid iso-amyl

MEthyl salicylate

HOC6H4CO2CH3 Oil of wintergreen salicylic acid alcohol

Table-1: [2] Combinations of carboxylic acids and alcohols resulting in ‘familiar’ esters


11

1.2 Esterification [1]

As mentioned earlier, methods used for the manufacturing of esters are generally

called as esterification. They may be mainly prepared by one of the four methods.

1) By Direct esterification of a carboxylic acid with an alcohol (Fischer Esterification).

2) From carboxylic acid derivatives by:

a) Reaction of acid anhydride and alcohol.

b) Reaction of acid salts and alkyl halides

c) Reaction of acid chloride and alcohol.

d) Reaction of amides and alcohol

e) Reaction of nitriles and alcohol

f) Reaction of ethers and alcohol.

g) Trans esterification(ester interchange)

i. Ester alcohol interchange (alcoholysis)

ii. Ester acid interchange (acidolysis)

iii. Ester-ester interchange

3) By Esters addition to unsaturated system

4) By dehydrogenation of alcohol

Different techniques are used to employ above mentioned processes. A brief

introduction of each technique or type of esterification has been discussed below.

1.3 Types of Esterification [3]

Following types of esterification are most widely used on industrial scale or in

laboratory.

• Batch Esterification

• Continues Esterification

• Vapor-Phase Esterification

• Catalytic Esterification


12

1.3.1 Batch Esterification

Batch process was used on industrial scale but it is now regarded as the older

method of production of esters. This method is based on the use of still pot reactor and an

ordinary fractionating column (bubble cap or packed type).

1.3.2 Continues Esterification

Three major factors, namely, law of mass action, laws of kinetics and laws of

distillation operate continuously in the operation of this type. Esterification occurs only when

the concentration of the components give calculated values of the apparent equilibrium

constants which are less than the value of the true equilibrium constants; otherwise hydrolysis

occurs. As whole process is taking place continuously, exact and accurate mathematical

calculations should be applied for successful completion of the process.

1.3.3 Vapor Phase Esterification

The catalytic esterification of alcohol and acid in the vapor phase has received

considerable attention because the conversions obtained are generally higher in the

corresponding liquid phase reactions. No commercial application of the vapor phase method

has been reported.

1.3.4 Catalytic Esterification

The esterification process carried away in the presence of a catalyst is taken in

the category of catalytic esterification. Often in the absence of catalyst the rate of reaction is

very small. This rate is increased by the addition of a catalyst acting as dehydrating agent,

thus shifting the equilibrium toward the right in favor of formation of the product. Further

details are discussed later.

1.4 Process Selection for Iso-amyl Acetate [3] [4]

All processes mentioned before for the preparation of esters are not equally

satisfactory for preparation of iso-amyl acetate. Comparison between the reaction, cost of raw

material, operational efficiency and percentage conversion are made to select the best method

of preparation.


13

The process of esterification by addition to unsaturated systems, results in secondary

and tertiary esters, if all olefins are used. So, it also results in the formation of vinyl acetate if

acetylene is used so this process cannot be used for the preparation of isoamyl acetate.

The process involving the reaction of carboxylic salts and alkyl halides, is employed

commercially for the production of isoamyl acetate, but it is very expensive. This reaction is

very rapid at room temperature, infact explosive almost. HCL gas may also be produced that

corrode the equipment. This gas causes the product to blacken, making it inappropriate for its

use in food industry. However, this method is applied only when esterification cannot be

carried out by the usual means.

The processes employing the reactions between acid chlorides/ alcohols, acid

anhydrides/ alcohols and transesterfication (Ester interchange), become very expensive, due

to very high cost of raw materials, for instance acetic finhydride, esters of acetic acid and acid

chlorides.

Moreover, acid chlorides/alcohols process, produce hydrogen chloride, which causes

corrosion and blackens the product.

However, today due to the advancements in science and technology, few alterations in

the above mentioned processes, make these reactions to be feasible and much more practical.

The process most preferable in Pakistan is Fischer Esterification of isoamyl alcohol and

acetic acid in the presence of appropriate catalyst, under specified conditions. Though the raw

material can be expensive for their use in Pakistan, but the method of preparation becomes

more economical due to high product yields and comparatively low operating cost.

1.5 Fischer esterification [5] [6]

In a Fischer esterification reaction, a carboxylic acid is exposed to an alcohol and a

strong acid catalyst that in turn yields an ester and water as the reaction products. The

reaction is reversible and the composition of the reaction mixture or position of equilibrium is

determined by thermodynamics. There are a number of ways to obtain good yields of the

product ester. Generally these methods involve the removal (or complexation) of water or the

use of a large excess of one of the reactants in order to favor the formation of the ester. Both

procedures for obtaining good yields of ester follow Le Chatelier's principle in that the


14

removal of water or the addition of an excess of one of the reactants drives the reaction

towards formation of the ester. A typical example of Fischer esterification reaction may be as

follows:

As mentioned before, the reaction is reversible, so it must be shifted to the product

side by using excess reagent, or removing one of the products. This reaction is also limited by

any steric hindrance in the carboxylic acid or the alcohol. The presence of acid catalyst acts

as a dehydrating agent and is usually used to remove water thus keeping the reaction moving

in forward direction to favor the formation of the ester.

The ease with which esterification takes place is determined largely by the type of

hydroxyl compounds and by the acid used. In general it may be said that primary alcohols

react more readily then the corresponding secondary alcohols, while tertiary alcohols and

phenols do not react to any serious extent. So, the preparation of acyl derivatives by direct

action of carboxylic acid on an alcohol is restricted to primary and secondary alcohols.

Under special circumstances, the preparation of esters by this method is

effected by warming a solution of the acid in an excess of appropriate alcohol using a

catalyst, for instance sulphuric acid or alcohol containing hydrochloric acid. The amount of

catalyst required is only about 1-5% of the weight of alcohol used.

1.5.1 Reaction Mechanism [5]

The reaction mechanism for this reaction may be divided in the following steps:

a) Proton transfer from acid catalyst to carbonyl oxygen. It increases electrophilic

behavior of carbonyl carbon.

b) The carbonyl carbon is then attacked by the nucleophilic oxygen atom of the

alcohol

c) Proton transfer from the oxonium ion to a second molecule of the alcohol gives

an activated complex.


15

d) Protonation of one of the hydroxyl groups of the activated complex giving a new

oxonium ion.

e) Loss of water from this oxonium ion and subsequent de-protonation giving

the ester.

All these steps can be expressed in the form of chemical equations as written as:

Formation of water in the reaction indicates that cleavage of breaking of carbonyl

oxygen bond of organic acid takes place thus releasing the -OH group as nucleophile. The

nucleophile attacks an alcohol thus forming water and releasing ester.

Therefore it can be safely concluded that “in the process of esterification of acid by

alcohol the hydrogen atom is available by alcohol while -OH group comes from acid”. The

generalized explanation of this selectiveness of the bond can also be done in the basis


16

electronic configuration (structure) of reactants and products. Since oxygen is more

electronegative than carbon, the carbonyl carbon in the carboxylic acid acquires a positive

charge while the carbonyl oxygen acquires a negative charge.

Any compound containing the electron pair will attack the carboxylic acid thus

creating a negatively charge state. The Transition State can lose the negative charge either by

loss of hydroxyl ion or by loss of species.

1.5.2 Rate Expression [3]

The interaction between a carboxylic acid and an alcohol is a reversible process and

proceeds very slowly. Equilibrium is only attained after refluxing for several hours.

When equimolar proportions of the acid and alcohol are employed, only about two-

third of the theoretically possible yield is obtained. Conversely, when equimolar quantities of

ester and water heated together approximately one third of the ester was converted to acid

and alcohol.

In the esterification reaction

2 2 2KKRCO H RCO R H O′ ′+ → +

The rate of esterification can be represented by

[ ][ ]2K RCO H R OH′

And the rate of hydrolysis by

[ ][ ]2 2K RCO R H O′ ′

Thus if the concentration are those at equilibrium

[ ][ ] [ ][ ]2 2 2K RCO H R OH K RCO R H O′ ′ ′=

And

[ ][ ][ ][ ]

2 2

2

RCO R H OKKK RCO H R OH

′= =

′ ′


17

The constant K is called the equilibrium constant of the reaction. Different

concentrations of the reactants and products can be present initially, but when equilibrium is

obtained the concentration of different species will be related such that the equilibrium holds.

The value of K will depend upon the particular carboxylic acid and alcohol

concentration and is determined experimentally by allowing the reaction mixture to reach

equilibrium and analyzing for reactants and products. In general, the numerical value of the

esterification constant varies between 1 to 10 for various primary and secondary alcohols and

carboxylic acids. The primary alcohols have higher value than secondary alcohols. Tertiary

alcohols have value much lesser than unity and direct esterification with carboxylic is not

practical since dehydration of alcohol will generally occur much more readily than

esterification.

The heat of reaction of many esterification reactions is nearly zero or at least quite

small. For these reactions the equilibrium constant is essentially independent of temperature.

Although the equilibrium constant indicates the extent to which esterification will

proceed. It tells nothing about the rate of reaction. The rate of reaction is affected much more

dramatically than the position of equilibrium by changes in the structure of the reactants. The

largest change is due to steric effects, with relatively little influence due to polar effects.

Because the esterification of an alcohol and an organic acid involves a reversible

equilibrium, the reactions do not go to completion: It is necessary to displace the equilibrium

in order to obtain high conversions. According to the law of mass action, the equilibrium is

displaced on favor of the ester by the use of excess one of the reactants. It is frequently

convenient to use acid in excess, however, if acid is expensive then alcohol can be taken as

an excess reactant. The excess reactant can be recovered by distillation.

The equilibrium is also displaced by removing one or both of the products as they are

formed. In practice it is generally achieved by distillation of water formed as it is insoluble

with other components of reactor and hence separated. It is first order reaction so rate

expression is proportional to 1st power of reactant.


18

1.5.3 Completing Esterification [3]

As in industry a higher yield is achieved by disturbing the equilibrium just by

removing one of the products formed either ester or water. For the removal of any product

formed, the esterification can be divided into three broad classes depending upon the

volatility of the ester.

• Class 1

This is the class of esters formed by esterification whose boiling point is lesser than

that of the corresponding alcohol. In such case ester can be removed from the reaction

mixture by employing the distillation method. For example, methyl formate, methyl acetate,

ethyl formate.

• Class 2

Esters of medium volatility are capable of removing water formed by distillation.

These include propyl, butyl and amyl formate, ethyl propyl butyl and amyl acetate and

methyl and ethyl esters of propanic, butyric and valeric acids.

• Class 3

With the esters of low volatility several possibilities exist. In case of the esters of

butyl and amyl alcohol, water is removed as a binary mixture with the alcohol. Usually using

solvent extraction technique separates this type of ester.

1.5.4 Pros & Cons of Fischer esterification [5]

The primary advantages of Fischer esterification compared to other esterification

processes are based on its relative simplicity. Straightforward acidic conditions can be used if

acid-sensitive functional groups are not an issue; sulfuric acid can be used; softer acids can be

used with a tradeoff of longer reaction times. Because the reagents used are "direct," there is

less environmental impact in terms of waste products and harmfulness of the reagents. Alkyl

halides are potential greenhouse gases or ozone depletors and possible ecological poisons.

Acid chlorides evolve hydrochloric acid gas upon contact with atmospheric moisture, so they

are corrosive, react vigorously with water and other nucleophiles (sometimes dangerously);

they are easily quenched by other nucleophiles besides the desired alcohol; their most


19

common synthesis routes involve the evolution of toxic carbon monoxide or sulfur

dioxide gases (depending on the synthesis process used).

Fischer esterification is primarily a thermodynamically-controlled process: because of

its slowness, the most stable ester tends to be the major product. This can be a desirable trait

if there are multiple reaction sites and side product esters to be avoided. In contrast, rapid

reactions involving acid anhydrides or acid chlorides are often kinetically-controlled.

The primary disadvantages of Fischer esterification routes are its thermodynamic

reversibility and relatively slow reaction rates—often on the scale of several hours to years,

depending on the reaction conditions. Workarounds to this can be inconvenient if there are

other functional groups sensitive to strong acid, in which case other catalytic acids may be

chosen. If the product ester has a lower boiling point than either water or the reagents, the

product may be distilled rather than water; this is common as esters with no protic functional

groups tend to have lower boiling points than their protic parent reagents. Purification and

extraction are easier if the ester product can be distilled away from the reagents and

byproducts, but reaction rate can be slowed because overall reaction temperature can be

limited in this scenario. A more inconvenient scenario is if the reagents have a lower boiling

point than either the ester product or water, in which case the reaction mixture must be

capped and refluxed and a large excess of starting material added.

Chapter 2 Iso-Amyl Acetate

20

Chapter no. 2

ISO-AMYL ACETATE


21

2.1 Significance [8] [9] [13]

Isoamyl acetate is a colorless organic ester of acetic acid and Isoamyl alcohol.

As discussed in the previous chapter, most famous and conventional method of

manufacturing Isoamyl acetate has been Fischer Esterification, using an appropriate catalyst

and under appropriate conditions. For Pakistan, being a third world country, it’s the need of

hour to design methods for manufacturing chemicals through most economical means, and

also reducing high amounts of imports from the developing/developed countries.

Keeping in view, all these aspects the authors studied the preparation of Isoamyl

acetate on laboratory scale, using three different types of catalyst, to choose the most

appropriate one. Here, the “appropriate catalyst” signifies the catalyst which can give the

maximum yield with maximum purity and minimum cost. Over the years, various catalysts

have been tested upon and proven right or wrong for the process.

With the enhancement in food technology, its impact on the human diet becomes

more evident. The global food supply has grown to depend on the quantity, quality, and

variety of wholesome and nutritious foods produced through scientific advancements in this

field. The use of preservatives, color additives, and flavoring agents by manufacturers plays

an important role in sustaining and extending the quality and quantity of food.

The Swiss company, Givaudan, one of the oldest and largest flavor and fragrance

houses in the world, manufacture flavorings for range of products, like breakfast cereals, ice

creams, herbal teas, biscuits, cake-mixes, soups and chewing-gums - Today Givaudan’s

formulations go into one in every five of the world’s artificially flavored foods; and although

the company will not name its customers, you can safely assume that it supplies most of the

big names. Thomas Hefti, senior scientist of Givandan explains that it’ll be uneconomic for

the food industry to rely solely on real bananas pears, strawberries etc.; there would not be

enough fresh fruit to go round, and besides, the individual fruit contain far too little natural

flavor to make large-scale extraction viable. Besides, we consumers apparently want those

heavily processed tastes that have become familiar.

Moreover, he adds, naturally sourced flavors may include all sorts of undesirable

residues left over from the farm: herbicides, pesticides, microorganisms, even levels of plant

toxins that, he suggests, could be harmful. In a state-of-the-art plant like Givaudan’s, the

consumer is guaranteed a healthiest end product, he suggests.


22

The secret to food flavoring popularly known as ‘creative appraisal’ of the flavors

provided by nature: although a real banana comprises around 225 volatile flavor components,

scientists can engineer an artificial alternative using just nine ingredients, with Isoamyl

acetate being the key one. A kilogram of the recipe, all mixed into a solvent - will flavor

5,000 liters of drinks. Even if it lacks the fresh fruit’s nuances, the result is impressively

familiar to anyone who has ever tasted a banana fast-food milkshake.

Isoamyl acetate is a famous replacement for banana and pear flavorings. In the past

few years, recent media had reported that bananas may be extinct within 10 years. The

Cavendish banana, found mostly on western supermarket shelves, has been under attack in

some Asian countries by a new strain of Fusarium wilt, also known as “Panama disease.”

FAO (United Nation’s Food and Agriculture Organization) has urged producers to promote

greater genetic diversity in commercial bananas, to counter the disease and meet the high

demand of bananas all year long. Here, a replacement for banana’s flavoring, Isoamyl acetate

is a pure blessing for the world masses.

Today, majority of scientists do not like the words ‘artificial’ or non-natural for

flavoring, instead the flavorings are mostly referred to as’ nature identical’. Dr Heini Menzi,

vice president for European R&D explains, ‘NI’ chemicals, are identical in their molecular

composition to ingredients found in nature. The difference is that they have been synthesized

in the lab by a chemical process - allowing a flavor originating in a plant to be manufactured

cost-effectively in vast quantities. A chemist can get to the same molecule, whether he takes

it physically out of the raw plant, or via synthesis. From a taste point of view, you could use

either.”

The importance of Isoamyl acetate does not end here. Isoamyl acetate over the years

has been used as a solvent for the major industrial polymer, cellulose nitrate. Though the

advent of other solvents for nitrocellulose, have replaced Isoamyl acetate, it still upholds its

individuality as a solvent. The popular antibiotic, pencilin relies on amyl acetate for its

extraction and purification from the fermentation broth. Due to their powerful solvency, high

volatility and mild odor, acetates are widely used in the manufacture and in the processing of

paints, coatings, adhesives, and printing industry. Furthermore, Isoamyl acetate due to its

characteristic aroma proves its significance in the manufacture of perfumes. Due to its vast

range of applications, Isoamyl acetate has proven to be one important chemical in the

industrial realm.


23

2.2 Chemistry of Amy Acetate [10]

Amyl acetate belongs to homologous series of organic compounds which are

known as esters. Esters are derivatives of carboxylic acids in which (-OH) group has been

replaced by (-OR) group.

R and R may be the same or different alkyl groups. These esters of carboxylic acid are

often referred as “Carboxylic esters”.

The Ester functional group (or function) may be presented as -CO-OR’ or -

COOR. Esters are the most important class of acid derivatives. A large number of these occur

in flowers and fruits which owe their fragrance to these compounds. They are used in many

perfumes, pesticides, fiber solvents and plasticizers. Amyl acetate (CH3COOC5H11), the ester

under consideration has the following structural formula.

Its “IUPAC” name is n-Pentyl Ethanoate. It is sometimes marketed under the

trader name of “Pantacetate or Pentasol-acetate”. Amyl is the name given due to eight

isomeric arrangements of radical C5H11.The word “amyl” is derived from Latin word

“Amylum” that means starch. Since, formerly the fusel oil (a mixture of primary alcohols

obtained by fermentation of starch), was the only significant source of five carbon alcohols

and their derivatives and then fusel oil in turn is obtained from starch hence the term ”amyl”

arose for Pentyl group (C5H11).

But the special compound we are discussing in this report is Isoamyl acetate, an

isomer of Pentyl acetate. It has structural formula as follows:


24

2.3 Chemical and Physical Properties of Isoamyl Acetate [11] [12]

2.3.1 Physical data Molecular weight: 130.18 amu

Boiling point (at 760 mm Hg) 142 oC (287.6 oF)

Specific gravity 0.876 at 15 oC (59 oF)

Vapor density 4.5

Melting point -78.5 oC (-109.3 59 oF)

Vapor pressure at 20 oC (68 oF) 4 mm Hg

Solubility Slightly soluble in water,

Soluble in most organic solvents.

Evaporation rate (butyl acetate = 1) 0.42

2.3.2 Reactivity Conditions contributing to

instability:

Heat, sparks, or flame.

Incompatibilities: Contact between Isoamyl acetate and nitrates, strong

oxidizers, strong alkalies, and strong acids should be

avoided.

Hazardous decomposition

protects:

Toxic gases and vapors (such as carbon monoxide and

carbon dioxide) may be released in a fire involving

isoamyl acetate.

Special precautions: None reported.

2.3.3 Flammability

The National Eke Protection Association has assigned a flammability rating of 3

(severe fire hazard) to isoamyl acetate. Some other specifications are:

1. Flash point: 38 oC (100 oF)

2. Auto-ignition temperature: 360 oC (680 oF)

3. Flammable limits in air (% by Vol. at 100 oC): 1.0 - 7.5

4. Extinguishing: For small fires use dry chemical, carbon dioxide, water spray, or

alcohol-resistant foam. Use water spray, fog, or alcohol-resistant foam to fight

large fires involving isoamyl acetate.


25

2.3.4 Storage

Isoamyl acetate should be stored in a cool, dry, well-ventilated area in tightly sealed

containers that are labeled in accordance with OSHA’s Hazard Communication Standard [29

CPR 1910.1200]. Containers of isoamyl acetate should be protected from physical damage

and ignition sources, and should be stored separately from nitrates, strong oxidizers, strong

alkalies, and strong acids.

2.3.5 Exposure Limits

Exposure to isoamyl acetate can occur through inhalation, ingestion, and eye or skin contact.

Limits and regulations for exposure to isoamyl acetate by different authorities are given in the

following lines.

OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for isoamyl acetate is 100 ppm (525 mg/m3) as an 8-hour time-weighted average (TWA) concentration.

NIOSH REL

The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for isoamyl acetate of 100 ppm (525 mg/m3) as a TWA for up to a 10-hour workday and a 40-hour workweek [NIOSH 1992].

ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned

isoamyl acetate a threshold limit value (TLV) of 100 ppm (532 mg/m3) as a TWA for a

normal 8-hour workday and a 40 hour workweek [ACGIH 1994].

2.3.6 Summary of toxic behavior

Effects on Animals

Isoamyl acetate is an irritant of the eyes and mucous membranes, and at high

concentrations it is a narcotic. Mice survived 2- to 3-hour exposures to 1,000 ppm

without effect, but at concentrations of 3,800 ppm for 4 to 6 hours, central nervous

system effects were seen. Cats and rabbits exposed to 900 ppm exhibited irritation of

the eyes and nose; at 5,000 ppm, the animals displayed lassitude, and some developed

diarrhea and albuminuria (indicating kidney damage). At postmortem, rabbits exposed

to isoamyl acetate on a sub-acute regimen displayed changes in the liver, congestion

and hypertrophy of the spleen, and congestion of the kidneys. Instilled into the eyes of

rabbits, isoamyl acetate caused mild and transient corneal epithelial injury.


26

Effects on Humans

Isoamyl acetate is an irritant of the eyes and mucous membranes. Human

volunteers exposed to 1,000 ppm isoamyl acetate for 30 minutes experienced

irritation, difficulty in breathing, fatigue, and an increased pulse rate. Severe throat

irritation occurs in humans at 200 ppm, and slight throat discomfort is experienced at

100 ppm. A concentration of 300 ppm is reported to be “noticeably” irritating to the

eyes; at higher concentrations, isoamyl acetate causes redness of the eyes and a

burning sensation, but no corneal damage has been reported. Exposure to

concentrations of 1,000 ppm for 30 minutes causes irritation, dyspnea increased pulse

headache and fatigue.

2.3.7 Exposure Sources and Control Methods

The following operations may involve isoamyl acetate and lead to worker exposures

to this substance:

• During the manufacture and transportation of isoamyl acetate

• Liberated during application of varnishes and nitrocellulose lacquers as protective

and finish coatings for wood, paper, metal, leather, and other surfaces by dipping,

roller coating, tumbling, knifing, or brushing

• Liberated during manufacture of nail polish, shoe polish, and furniture polish;

during fermentation of whiskey grains

• Liberated during manufacture of cellulosic photographic film by formation from

solvent solutions

• Use as a solvent of old oil colors, formaldehyde, synthetic resins, waxes, paints,

phosphors, tannins, nitrocellulose, lacquers, celluloid, and camphor, and to cover

unpleasant odors

• Use in manufacture of bath sponges, artificial leathers, artificial silk, rayon, pearls,

artificial glass, waterproof varnishes, bronzing fluids, and metallic paints

Methods that are effective in controlling worker exposures to isoamyl acetate,

depending on the feasibility of implementation, are as follows:

• Process enclosure

• Local exhaust ventilation

• General dilution ventilation


27

• Personal protective equipment (PPEs)

2.4 Applications [10] [14] [15]

Isoamyl acetate had been a very prominent and useful chemical product, and is sold

under the trade name of” banana oil” or “pear oil”. It has following important applications

a) Isoamyl acetate is one of the older and still one of the best solvents for cellulose

nitrate.

b) Amyl acetate is used in the, extraction and purification of penicillin. Penicillin is

recovered from the fermentation broth by extraction with amyl acetate after lowering

the pH, to get a favorable partition coefficient. The solvent is then treated with

buffered phosphate solution from which penicillin is eventually produced by drying.

c) It is employed in making of photographic films and moving picture films.

d) Though rarely, but it is used as an additive in American cigarettes.

e) It is employed in the manufacture of shoe polishes, silk, water proof varnishes and

bronzing liquids.

f) Furthermore, it is used for drying and finishing of textile.

g) It is recommended as standard oil in photometry.

h) It is widely used in the formation of artificial fruit flavors. For instance,

i. Banana flavored bubble gum.

ii. Sometimes found as a preservative in sodas, soft drinks, etc

iii. One form of isoamyl acetate is found in artificially pear flavored food

articles

iv. In alcohol solution as a pear flavor in mineral waters and syrups

i) Amyl acetate is also used as a solvent for celluloid, camphor, formaldehyde synthetic

and natural resins.

j) It is utilized in the making of rayon and perfumes. (Note: for use in the manufacture

of perfumes it should be free from amyl alcohol.

k) Dry cleaning preparations also employ isoamyl acetate.


28

2.5 Status in Pakistan

Reliable sources from PCSIR reported that Isoamyl acetate was being manufactured

in Pakistan in very minor quantities. The reason being the expensive raw materials, also the

fact that the product obtained was not fitting for the use in food and pharmaceutical

industries. Therefore, it is being imported from Brazil and China, to fulfill its demand in

Pakistan’s industrial realm.

2.6 Isoamyl Acetate: the past, the present and the future [10] [16]

Isoamyl acetate has been seen, tasted, or touched by many generations. Over centuries

it has been consumed by the human population, as a popular fruit known as banana. Isoamyl

acetate is the distinctive odor, taste, and color of bananas.

The discovery of isoamyl acetate can be traced back to the early 20th century. In 1920,

the Standard Oil Company of New Jersey began to produce isopropyl alcohol from light

fraction of petroleum. By 1926, Sharpless Chemical Corporation Belle, started separating

pentane from casing head gas and employed it in producing a mixture of pentyl alcohols,

including amyl alcohol and subsequently produced theft respective acetates (amyl acetate) in

order to fulfill the demands of liquor industry.

Before and during World War II, amyl acetate was popularly known as Banana Oil

and was very widely used as high boiling solvent constituent for paints coatings and resins. It

was also employed for the extraction of penicillin from the fermentation broth.

After the mid of 20th century, isoamyl acetate went on to prove its importance as an

industrial chemical. Its realm of applications has further widened over the years.

Subsequently, a variety of processes for its production have come into being.

By the year 1965, Isoamyl acetate was Granted Generally Recognized as Safe

(GRAS) status by PEMA.

By 1983, isoamyl acetate could be derived from natural gasoline, along with the

method of esterification of isoamyl alcohol with acetic acid.

Later that decade in 1989, the applications of isoamyl acetate diversified. The

following uses of isoamyl acetate were also recognized in alcohol solution as a pear flavor, in


29

mineral waters and syrups; as a solvent for old oil colors; swelling bath sponges; covering

unpleasant odors, and perfuming shoe polish.

In 1994, Isoamyl acetate as a synthetic flavoring substance was permitted for direct

addition to food for human consumption, as long as (a) it is used in the minimum quantity

required to produce its intended effect, and otherwise in accordance with all the principles of

good manufacturing practice. (b) It consists of one or more of the following, used alone or in

combination with flavoring substances and adjuvants generally recognizable as safe in food.

The use pattern which was prominent by 1990s: Isoamyl acetate being used as a solvent for

tannins, nitrocellulose, lacquers, celluloid, and camphor. It also is used as a flavoring agent in

soft drinks, chewing gum, and candies. Isoamyl acetate being applied during the

manufacturing process of artificial silk, leather, pearls, photographic films, celluloid cements,

waterproof varnish, bronzing liquids, metallic paints, dyeing, and finishing textiles.

Today, in the 2l century isoamyl acetate still keeps the status of an essential industrial

chemical. It is still being applied in the fields mentioned earlier. It is now without any doubt,

the natural identical of banana and pear fruits.

In future isoamyl acetate will withhold its reputation. Moreover if the New Science

Magazine reports (of bananas being extinct within 10 years) prove right, then it is going to be

a very important replacement for bananas for all the fruit lovers.

Due to its diverse nature in the past and present, its future is full of bright possibilities.

Chapter 3 Raw Materials & Experimentation

30

Chapter no. 3

RAW MATERIALS & EXPERIMENTATION


31

As described in 1st chapter isoamyl acetate can be prepared by Fischer

esterification reaction by the reversible, catalyzed, combination of acetic acid with isoamyl

alcohol. This method consists of heating a mixture of the acid and alcohol in the presence of

catalyst.

CH3COOH + C2H5OH → CH3COOC2H5 + H2O

The authors’ task was to prepare isoamyl acetate, using three different types of

catalysts; Paratoluene sulphonic acid, vanadium titanate and sulphuric acid.

3.1 Raw Materials

Following are the raw materials used for the preparation of isoamyl acetate.

1. Isoamyl Alcohol

2. Acetic Acid/Ethanoic Acid

3. Catalyst:

(i) Sulphuric Acid

(ii) Para-Toluene Sulphonic Acid

(iii) Vanadium Titanate

3.1.1 Isoamyl Alcohol [17] [18]

It is one of the eight isomers of amyl alcohol. Amyl alcohol may be any of 8

alcohols with the formula C5H11OH. Out of these eight isomers four are primary alcohol, 3

are secondary and 1 is tertiary. The odd carbon structure and the extent of branching provide

email alcohol with unique physical and solubility properties.

Our desired alcohol Isoamyl alcohol is the chief constituent of fermentation

amyl alcohol, and consequently a constituent of fusel oil. It is separated from fusel oil by

shaking with strong brine solution; then the oily layer is separated from the brine layer and is

distilled, the portion boiling between 125 and 140 °C is collected. For further purification it is

shaken with hot lime water, the oily layer is separated, dried with calcium chloride and

fractionated; the fraction boiling between 128 and 132 °C is collected.


32

It may also be synthesized from isobutanol by conversion into isovaleraldehyde,

which is subsequently reduced to isobutyl carbinol by means of sodium amalgam.

It is a colourless liquid of density 0.8247 g/cm³ (0 °C), boils at 131.6 °C, slightly

soluble in water, easily soluble in organic solvents. It possesses a characteristic strong smell

and a sharp burning taste. When pure, it is nontoxic, while the impure product is toxic

On industrial scale, a mixture of isomeric alcohols (1-pentanol and 2-methyl 1-

butanol) is often preferred because the different degree branching imparts a more desirable

combination of properties; they are also less expensive to produce commercially.

Three significant commercial processes for the production of amyl alcohols include:

1) Fusel oil

2) Chlorination hydrolysis process

3) Oxo process

3.1.1.1 Preparation from Fusel oil [19]

Fusel oil is a by-product of alcoholic fermentation process and is obtained during

distillation crude ethyl alcohol. Prior to the development of a synthetic process, fusel oil was

the only commercial source of amyl alcohols.

The major components of fusel oil are the primary alcohols, 3-Methyl 1-butanol and

2-Methyl 1-butanol. Fusel oil also contains water, 1-Pentanol and ethyl, propyl, butyl, hexyl

and heptyl alcohols. The product sold as refined amyl alcohol contains about 85% 3-Methyl

1-butanol (isoamyl alcohol) and 2-Methyl 1-butanol.

3.1.1.2 Preparation from Chlorination Hydrolysis Process [20]

The manufacture of first synthetic amyl alcohol by this route was begun in 1926.

Fusel oil alcohols were in limited supply and a new source of amyl alcohols and their esters

were needed to meet the increasing demand of automotive industry for higher boiling lacquer

solvents.

In this process, a mixture of amyl chlorides was first produced by continuous vapor

phase chlorination of a mixture of pentane and iso-pentane in the absence of light and


33

catalysts. Hydrolysis of chlorides with aqueous caustic at high temperature produces a

mixture of 7 of the 8 amyl alcohol isomers; formation of neopentyl alcohol is negligible.

In contrast to the fusel oil and oxo process, this method provides significance

quantities of the three secondary amyl alcohols, especially 2-pentanol.

3.1.1.3 Preparation from Oxo Process [20]

Due to the catalytic advancements made since 1970s, Oxo process also known as

hydroformylation is used now as days to obtain amyl alcohols. Due to effectiveness of this

process, comparatively high cost and waste disposal problems associated with the

chlorination hydrolysis process have been minimized. So the Oxo process is now the

principle source of amyl alcohol. In the low pressure, hydro formulation (oxo) process for the

production of amyl alcohols, 1-butene, 2-butene and 2-methyl propylene react with a mixture

of carbon mono oxide and hydrogen in the presence of suitable metal catalyst (Rhodium) to

form an isomeric mixture of aldehyde with one more carbon atom than the olefin. Once made

the 1-pentaldehyde, 2-methyl butyraldehyde and 3-methyl butylaldehyde are hydrogenated to

corresponding amyl alcohols.

Both 1- and 2- butylene mainly give 1-pentanol and 2-methyl-1-butanol.

3-methyl-1-butanol (isoamyl alcohol) is formed in much smaller amount, methyl propene

leads chiefly to 3-methyl-1-butanol, and only very small amounts of 2,2-dimethyl-1-propanol

are formed. It will be noted that in all cases the main product is primary alcohols. The

product is fractionated, and sold in three grades.


34

3.1.2 Acetic Acid/ Ethanoic acid [21] [22]

It is a corrosive organic acid having sharp odor. It is found in ocean water, oil field

brines, rain and in traces in many plants and animals liquids. Fermentation of fruit and

vegetable juices yield 2- l2% of acetic acid solutions, usually called vinegar. It is colorless

liquid and is also known commonly by these names: Ethanoic Acid, Methane Carboxylic

Acid, and Ethylic Acid. it is shipped under the name of Acetic Acid or Glacial Acetic Acid.

Commercial production of acetic acid has been revolutionized in the decade 1978 to

1988. Currently all the acetic acid is produced commercially through:

1. Acetaldehyde Oxidation,

2. Methanol or Methyl Acetate Carbonylation

3. Light Hydrocarbon Liquid Phase Oxidation

Some small amounts are also generated by:

1. Butane Liq0uid Phase Oxidation

2. Direct Ethanol Oxidation

3. Synthesis gas

3.1.2.1 Acetaldehyde oxidation

Ethanol is easily dehydrogenated through oxidation, to acetaldehyde using silver,

brass or bronze as catalysts. Acetaldehyde can then be oxidized in the liquid phase in the

presence of cobalt or manganese salts yield acetic acid. Conversion of acetaldehyde is

typically more than 90% and the selectivity of acetic acid is higher than 95%. Stainless steel

can be used in constructing the plant.

The problems in this process exist are related to more extensively automating control

of the system, notably at startup and shut down, although even these matters have been

largely solved. This route is the most reliable of acetic acid processes.


35

3.1.2.2 Methanol Carbonylation

Acetic Acid is usually was produced in 1920s by the reaction of methanol with carbon

monoxide in the presence of catalyst. A wide range of catalysts and different ranges of

pressure and temperature have been used during the century for the production of acetic acid.

The chief catalysts used are phosphoric acid, copper phosphate, hydrated tungsten oxide, and

iodides. Nickel iodide proved to be more particularly valuable.

3.1.2.3 Butane-Naphtha Catalytic Liquid Phase Oxidation:

Direct Liquid Phase oxidation of butane and/or naphtha was once the most favored

worldwide route of acetic acid because of the low cost of these hydrocarbons. Butane, in the

presence of metallic ions, e.g. cobalt, chromium or manganese undergoes simple air oxidation

in acidic solvent. The peroxide intermediates are decomposed by high temperature,

mechanical agitation and by the action of metallic catalysts, to form acetic acid and a

comparatively small suit of other compounds. Ethyl acetate and butanone are produced, and

the process can be altered to provide large quantities of these valuable materials. Ethanol is

thought to be an important intermediate, acetone forms through minor pathways from

isobutene present in the hydrocarbon feed. Formic acid, propanoic acid and minor quantities

of butyric acid are also formed. Final acetic acid purification follows much the same

treatments as are used in acetaldehyde oxidation.

3.1.3 Catalyst [23] [24]

Flowing three type’s catalyst are used for the manufacture of isoamyl alcohol.

1. Para Toluene Sulphonic Acid 2. Vanadium Titanate 3. Sulphuric Acid

3.1.3.1 Para Toluene Sulphonic Acid (PTSA):


36

Para toluene sulphonic acid is employed as such in acid form for applications where

strongly polar hydrophilic (– SO2, OH) group confers needed properties on a comparatively

hydrophobic non polar organic molecule.

For the production of PTSA, sulfonation is carried out. Aromatic sulfonation places a

sulfonic group (-SO3H) onto the benzene ring. This is accomplished by the use of Sulfur

Trioxide in the presence of Sulfuric Acid. The Sulfur Trioxide (SO3) serves two purposes. It

acts first as the sulfonating agent, and it prevents the unfavorable reversible of this

equilibrium by reacting with and effectively removing the water product thus driving this

equilibrium to the right.

SO3 + H2O → H2SO4

The Sulfonation can be accomplished without the Sulfur Trioxide by using excess

Sulfuric Acid. Then extra Sulfuric Acid will act as a dehydrating agent absorbing the water

and preventing the reversal of the equilibrium. This is not as efficient as the Sulfur Trioxide

so the reaction is much slower.

Along with p-toluene sulphonic acid, traces (about 10 to 15%) of o-toluene sulphonic

acid are also formed. Washing and distillation can result in a purer product.

Para toluene sulphonic acid is the most recent catalyst utilized in the production of

isoamyl acetate. This is a strong deactivating agent, resulting in a much more stable sulfonate

ion and a proton. This proton helps in initiating the reaction between isoamyl alcohol and

acetic acid, as shown in the reaction mechanism below.


37

REACTION MECHANISM OF THIS CATALYS

STEP 1: DISSOCIATION:

STEP2: PROTONATION:

STEP 3: NUCLEOPHILIC ATTACK (AMYL ALCOHOL):

STEP 4: HYDROGEN ION TRANSFER:

STEP 5: ELIMINATION OF PROTON AND WATER:

STEP 6: REGENERATION:


38

3.1.3.2 Vanadium Titanate (V2O5/TiO2)

Vanadium catalysts have been used widely in various organic oxidation processes,

sulfonation of aromatic compounds, preparation of hypochlorites, manufacture of sulphuric

acid etc. The authors, due to its huge popularity as a catalyst, employed one of the vanadium

compounds in the production of isoamyl acetate i.e. vanadium titanate. It is also known as a

refractory titanate.

In general, vanadium titanate can be prepared merely by hearing an intimate mixture of the

oxide of vanadium with titanium dioxide at relatively high temperature.

The vanadium titanate behaves as a lewis acid/lewis base, to act as a catalyst in the

production of isoamyl acetate.

3.1.3.3 Sulphuric Acid:

Sulphuric acid is also largely used as catalyst in amyl acetate production. It is a strong

dibasic acid. In addition, it is an oxidizing and dehydrating agent, in particularly, towards

organic compounds. The dehydrating action is very important in absorbing the water formed

in such chemical conversions as esterification, nitration and sulphonation. This causes the

reaction to move in the forward direction, as a result ensures a high yield.

Sulphuric acid has a boiling point of 270°C and relative density of 1.8357. It is

manufactured by two process contact process and chamber process. Both processes are based

on SO2, being catalytic in nature and both require air as the source of oxygen for making SO3.

Sulphuric acid is widely sold as solutions in water of various concentration or in the

form of H2S2O7 (SO3 in H2SO4) known as oleum.

Sulphuric acid is very effective as a catalyst in the manufacture of isoamyl acetate,

and it is not as corrosive to metals as hydrochloric acid. However, the product obtained by

employing sulphuric acid, is not at all fitting for the use in food and pharmaceutical

industries.


39

REACTION MECHANISM

STEP 1: DISSOCIATION:

STEP 2: PROTONATION:

STEP 3: NUCLEOPHILIC ATTACK (AMYL ALCOHOL):

STEP 4: HYDROGEN ION TRANSFER:

STEP 5: ELIMINATION OF PROTON AND WATER:

STEP 6: REGENERATION:


40

3.2 Experimental Performance [25]

3.2.1 Chemical Reaction Involved

Following chemical reaction is involved in the iso amyl acetate preparation;

3.2.2 Procedure

Following procedure was adopted in order to prepare the isoamyl acetate using three

different catalysts.

1. First of all 500g of acetic acid (limiting reactant) was weighed out and mixed it

with 845g of isoamyl alcohol (the excess reactant being 10% in excess) in a round

bottom three neck flask

2. Now 2g of PTSA (Para Toluene Sulphonic acid) was added as a catalyst in to the

reaction mixture in the first experiment.

a. In second experiment, 4g of PTSA was weighed out in to the reaction mixture.

b. For the third experiment, 4g of PTSA was weighed out as a catalyst in to the

reaction mixture.

c. For the fourth one, 4g of PTSA was taken (and distillation was carried out

before and after washing.).

d. In the fifth experiment, 4g of vanadium titanate was taken as a catalyst.

e. In the last experiment, 50g of 0.1 of sulphuric acid were taken.

3. A reflux was attached to one of the necks of the flask and heated mixture to about

100-120°C under the reflux condition till the maximum quantity of water was

obtained. The heating was carried out for 5-6 hrs.

4. After the reaction being carried out, the flask was allowed to cool down.

5. A separating funnel was taken, washed and was dried on a stand.


41

6. Following treatments were done in the sixth step:

a. For 1st, 3rd and 4th experiments, a 5% Na2CO3 solution was prepared by

weighing 25g of Na2CO3 and dissolving it in 500m1 of water. The product

mixture containing isoamyl acetate, isoamyl alcohol, acetic acid and some

quantity of PTSA was washed with 5% Na2CO3 solution in the separating

funnel. Two layers of liquid were formed; the bottom layer was drawn off, as

it was that of water and other water-soluble ionic impurities, while the upper

layer was that isoamyl alcohol and isoamyl acetate. Now, the product mixture

was washed with water at least 4 times so that pH of the product mixture was

about 7.0.

b. For fifth experiment, 10% Na2CO3 solution by weighing out 50g of Na2CO3

and was dissolved in 500m1 of water. The product mixture was firstly washed

with it and then with water at least 6 times until its pH was almost 7.0.

c. For sixth time, 8% Na2CO3 solution was prepared by weighing 40g of Na2CO3

and dissolving it in 500m1 water. Washing of the product mixture was done

with it, until the pH of 7.0 was obtained.

7. The final product mixture was containing isoamyl alcohol and isoamyl acetate.

The only method to separate these two was distillation. The distillation was

carried out in a three neck round bottom flask. During distillation the product

mixture was heated to 132-135°C so that rest of water and unreacted and excess

isoamyl alcohol should be completely separated.

8. After distillation following colors of the product were obtained;

a. In case of PTSA used as a catalyst, the final product obtained was colorless.

b. In case of vanadium titanate used as catalyst, color of the product was very

pale.

c. In case of sulphuric acid used as catalyst, color of the product was slightly

pale. (A known quantity of charcoal was taken to remove color but of no use).

9. After the experiments completed, the product samples were sent for GLC (gas-

liquid chromatography) to obtain the results.


42

Fig 3.1: Schematic Figure of Experimental Setup

1. Isomantle 2. Condenser 3. Separator 4. Motor 5. Stirrer 6. Thermometer 7. 2 Litres round bottom three neck

flask

Chapter 4 Results & Discussion

44

Chapter no. 4

RESULTS & DISCUSSION


45

4.1 Stoichiometric Calculations

As acetic acid was taken as a limiting reactant, hence the quantity of other chemicals

used is taken on basis of acetic acid

Amount of acetic acid weighed out = 500g

Density of acetic acid = 1025g/cm3

Volume of acetic acid used = 500/1025 = 488ml

So, Basis: 500g of acetic acid

4.1.1 Isoamyl Alcohol

As 60g of acetic acid is to react= 88g of isoamyl alcohol

1g of acetic acid is to react = (88/60)

500g of acetic acid is to react = (88/60) x 500 = 734g

As isoamyl alcohol is used 10% in excess therefore,

Amount of isoamyl alcohol in excess = 734 x 0.1 = 73.4g

So,

Total amount of isoamyl alcohol used = 734 + 73.4 807.4

As,

Density of isoamyl alcohol = 0.8104g/cm3

Therefore,

Volume of isoamyl used = 807.4/0.8104 996.3ml

4.1.2 Isoamyl Acetate

60g of acetic acid required to produce = 130g of isoamyl acetate

1g of acetic acid required to produce = 130/60

500g of acetic acid required to produce = (130/60) x 500 =1084g

As,

Density of isoamyl acetate 0.878g/cm3

So,

Volume of isoamyl acetate to be produced = 1084/.0878 = 1235ml


46

3. Water:

60g of acetic acid required to produce = 18g or water

1g of acetic acid required to produce = 18/60

500g of acetic acid required to produce = (18/60) x 500 l5Og

As

Density of water = l000g/cm3

So,

Volume of water produced = 150/1.0 = 150ml

4.2 Experimental Calculations

4.2.1 Amount of Water Produced

PTSA was used as a catalyst for Sample# 1, 2, 3 & 4, Vanadium Titanate for sample#5 and

Sulfuric Acid for Sample# 6

SAMPLE #1

Volume of water obtained = 136 ml

Amount of water not formed = 150- 136 = 14 ml

As Density of water = 1.000 g/ml

Therefore, Amount of water not formed = 14g

SAMPLE # 2


Amount of water not formed = 150 – 132 =18 ml

As, Density of water = 1.000 g/ml

Therefore, Amount of water not formed = 18 g

SAMPLE #3



47

Amount of water not formed = 150 - 141 = 9 ml


Therefore, Amount of water not formed= 9 g

SAMPLE # 4




Therefore, Amount of water not formed = 6 g

SAMPLE # 5




Therefore, Amount of water not formed 60 g

SAMPLE # 6




Therefore, Amount of water not formed = 40g


48

4.2.2 Actual Amount of Isoamyl Acetate

No. of Samples Weight of product

(g) Purity from GLC

(%age) Weight of Isoamyl

Acetate (g)

1 965 92.89 896

2 952 92.04 876

3 1017 91.0 925

4 1024 94.0 963

5 880 54.0 475

6 776 76.4 590

4.2.3 Theoretically produced amount of Isoamyl Acetate

SAMPLE #1:

18g of water produced with = 130g of Isoamyl Acetate

1g of water produced with = 130/18

14g of water produced = 130/18 x 14

= 101.1g of isoamyl acetate

Amount of isoamyl acetate produced theoretically = 1084 -101.1

= 982.9g isoamyl acetate

SAMPLE # 2:




=130g of isoamyl acetate

Amount of isoamyl acetate produced theoretically = 1084 - 130

= 954g of isoamyl acetate

SAMPLE # 3:




=65g of Isoamyl Acetate


= 1019 g of isoamyl acetate


49

SAMPLE # 4:




= 413g of Isoamyl Acetate

Amount of isoamyl acetate produced theoretically = 1084 - 43.3

= l040.67g ≈ 1041 g of isoamyl acetate

SAMPLE # 5:

18g of water produced with = 130 g of Isoamyl Acetate

Ig of water produced with = 130/18


=433g of Isoamyl Acetate


= 650.6 g of isoamyl acetate

SAMPLE #6:

18g of water produced with = 130 g of Isoamyl Acetate



= 289g of Isoamyl Acetate


= 795g of isoamyl acetate

4.2.4 Percentage Yield

SAMPLE # 1

%age yield of isoamyl acetate = Actual yield

Theoritical yield

= 896/983 x 100

= 91.15 %

SAMPLE # 2


Theoritical yield

= 876/954 x 100

= 91.82%


50

SAMPLE # 3


Theoritical yield

= 925/1019 x 100

= 90.77%

SAMPLE # 4


Theoritical yield

= 963/1041 x 100

= 92.51%

SAMPLE # 5


Theoritical yield

= 475/651 x 100

= 72.90%

SAMPLE # 6


Theoritical yield

= 590/795 x 100

= 74.21%


51

4.2.5 Laboratory Tests of Isoamyl Acetate

1. Surface Tension

Surface tension was found out by using stalagometer. Firstly, water was taken in

stalagometer and number of drops was counted from the lower end. Similar procedure was

repeated for isoamyl acetate. Densities of water and isoamyl acetate, and the value of surface

tension of water were taken from literature. Surface tension of isoamyl acetate was calculated

using the relation:

γ2/ γ1 = n1/n2 × Q2/Q1

No. Of Samples

No. of drops of water, (n1)

No. of drops of

Each sample,

(n2)

Density of water,

p1 (g/cm3)

Density of each sample,

p2 (g/cm3)

Surface Tension of water, γ1

(dyne/cm)

Surface Tension of

each sample, γ2 (dyne/cm)

1 59 144 1.00 0.876 72.53 26.03

2 59 141 1.00 0.876 72.53 26.59

3 59 140 1.00 0.876 72.53 26.77

4 59 140 1.90 0.876 72.53 25.03

5 59 137 1.00 0.876 72.53 27.26

6 59 139 1.00 0.876 72.53 26.92

2. Relative Viscosity

Relative viscosity was calculated by using Ostwald’s viscometer. In this case, the time

of flow of both water and isoamyl acetate through its bulb was noted. The values of density

of water and isoamyl acetate and viscosity of water were taken from literature. The

relationship used for the determination of viscosity of isoamyl acetate was:

γ2/ γ1 = n1/n2 × Q2/Q1


52

No. Of Samples

Time of flow for sample t1 (s)

Time of flow for

water t2 (s)

Density of sample,

p1 (g/cm3)

Density of each sample,

p2 (g/cm3)

Viscosity of water, μ1 (cP)

Viscosity of each

sample, μ2 (cP)

1 65 59 0.876 1.00 0.89 0.860

2 64 59 0.876 1.00 0.89 0.844

3 62 59 0.876 1.00 0.89 0.819

4 68 59 0.876 1.00 0.89 0.898

5 6o 59 o.87t 1.00 0.89 0.792

6 66 59 0.876 1.00 0.89 0.870

3. Specific Gravity

Specific gravity of the prepared samples of esters was found by using the specific

gravity bottle. As the volume of specific gravity bottle was 25m1, so 25m1 of both water and

isoamyl acetate was taken in it, one by one. The bottle with sample was weighed using the

electrical balance. Then, their weight ratio was taken to find out the specific gravity.

Sp. gr. = w2/w1

No. Of Samples

Weight of sp. gr

bottle (g)

Weight of sp. gr

bottle + water (g)

Weight of sp. gr

bottle + sample (g)

Weight of water w1

(g)

Weight of sample w2

(g)

Specific gravity of

sample w2/w1

1 8.21 40.79 36.20 32.58 27.99 0.859

2 8.21 40.79 36.27 32.58 28.06 0.861

3 8.21 40.79 36.31 32.58 28.10 0.862

4 8.21 40.79 36.10 32.58 27.89 0.865

5 8.21 40.79 36.92 32.58 28.71 0.878

6 8.21 40.79 36.46 32.58 28.25 0.867


53

4. Refractive Index

The refractive index of the prepared sample was determined by using Abbe’s

Refractrometer. The samples were applied respectively on to the prism and the reading was

observed directly from the graduated scale.

No. of Samples Refractive Index

1 1.416

2 1.411

3 1.419

4 1.404

5 1.429

6 1.421


54

4.3 Summary of Results

Sample No.

(Catalyst Used)

Color Odor Purity (%age)

%age yield

Sp. Gravity

Refractive index

Viscosity Surf.

Tension

1 (PTSA)

Colorless Banana

like 92.89 91.15 0.859 1.416 0.86 26.03

2 (PTSA)

Colorless Banana

like 92.04 91.82 0.861 1.411 0.844 26.59

3 (PTSA)

Colorless Banana

like 91.09 90.77 0.862 1.419 0.819 26.77

4 (PTSA)

Colorless Banana

like 94.00 92.51 0.865 1.404 0.898 25.03

5 (Vanadium Titanate)

Very Pale

Banana like

54.00 72.90 0.878 1.29 0.792 27.26

6 (Sulfuric

Acid)

Slightly Pale

Banana like

76.40 74.21 0.867 1.421 0.870 26.92

Standard values

Colorless Banana

like 99.00

97-99

0.868-0.878

1.400-1.405

24.85-24.97

4.4 Discussion on Results:

Table 4.3 shows the observations made in the preparation of iso amyl acetate by

esterification of amyl alcohol with glacial acetic acid. It was observed that using different

reaction conditions and catalysts, extent of reaction and purity of product varied.

Firstly, the authors used PTSA as catalyst with excess of iso amyl alcohol and

performed a series of four experiments.


55

i. The first sample obtained had a purity of 92.89% from the GLC report and

percentage yield of 91.15%.

ii. For the second, purity was 92.04% and yield was 91.82%.

iii. In case of third, the purity obtained from GLC was 91.09% and percentage yield

calculated was 90.77%.

iv. For the fourth experiment, the distillation was carried out before and after

washing, and the GLC reported a purity of 94.O%O and percentage yield

determined was 92.51%.This was the maximum purity and yield obtained.

Secondly, vanadium titanate was used as catalyst and the purity of product was 54%

and the yield obtained was 72.90%.

For the last experiment with sulphuric acid as catalyst, the purity reported was 76.40

and yield determined was 74.21%.

The tests of refractive index showed a linear relationship between purity and

refractive index. As the purity decreased the observed refractive index decreased and vice

versa. For the test of viscosity, again a linear relation with purity was observed.

However, from the tests of surface tension, an inverse relation between purity and

surface tension was seen. While, there was no proper pattern in the variation of specific

gravity with purity.

All of the above samples had a banana like odor; along with color range between

colorless to pale.

4.4.1 Conclusion Three catalysts were employed in the preparation of isoamyl acetate, namely PTSA

vanadium titanate and sulphuric acid.

In case of vanadium titanate, before washing product was obtained as an emulsion, for

which thorough washing with sodium carbonate was required. After washing and distillation,

the product with minimum yield and purity was obtained. Thus, the authors completely

discourage the use of vanadium titanate as a catalyst in the manufacture of isoamyl acetate.

The results from the conventional catalyst, sulphuric acid showed greater yield and

purity in comparison to vanadium titanate. However, the use of sulphuric acid as a catalyst

was rejected, as its performance was inferior to PTSA. Also, sulphuric acid, when used in the


56

large scale preparation, gives a product which is not appropriate for food and pharmaceutical

use.

From the above results, the authors concluded that the maximum yield and the most

pure product obtained were, in case of PTSA as a catalyst. So it was found to be the most

feasible catalyst, and so recommended for the future and large scale preparation of isoamyl

acetate.

REFERENCES

1. http://en.wikipedia.org/wiki/Ester

2. http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/crbacid1.htm

3. Kirk-Othmer, “Concise Encyclopedia of Chemical Technology” 5th Edition, Wiley-

Interscience, 1963

4. Junzo O., Joji N., “Esterification: Methods, Reactions, and Applications”, 2nd

Edition, Wiley-VCH Verlag GmbH & Co. KGaA, 2006

5. http://en.wikipedia.org/wiki/Fischer-Speier_esterification

6. http://www.organic-chemistry.org/namedreactions/fischer-esterification.shtm

7. Snell, Foster D., Snell, Cornelia T., “Dictionary of Commercial Chemicals”,

3rd Edition, Van Nostrand Reinhold Inc.,U.S.A., 1962

8. Clarke A, “Flavoring Materials, Natural & Synthetic”, Mocison and Gills Ltd.,

Edinburgh, 1922

9. D. L. Pavia, G. M. Lampman, “Introduction to Organic Laboratory Techniques, A

Micro-scale Approach”, G. S. Kriz, and R. G. Engel, 1990

10. http://en.wikipedia.org/wiki/Isoamyl_acetate

11. http://www.chemicalland21.com/specialtychem/perchem/ISO-AMYLACETATE.htm

12. http://www.osha.gov/SLTC/healthguidelines/isoamylacetate/recognition.html

13. http://www.davidrowan.com/2008/06/observer-how-technology-is-changing-our.html

14. http://www.bookrags.com/research/isoamyl-acetate-chmc/

15. http://www.oxiteno.com.br/aplicacoes/mercados/doc/documento.asp?produtoMarca=

140405173772637HFBAAF4E11DH43492&idioma=IN&r=.pdf

16. US Code of Federal Regulations (CFR) for Foods and Drugs,

http://cfr.vlex.com/source/code-federal-regulations-food-drus-1070

17. http://en.wikipedia.org/wiki/Amyl_alcohol

18. http://en.wikisource.org/wiki/1911_Encyclopædia_Britannica/Amyl_Alcohols

19. http://www.highbeam.com/doc/1G1-230438398.html

20. Production of Isoamyl alcohol

http://www.sbioinformatics.com/design_thesis/Isoamyl_alcohol/Isoamyl-

2520alcohol.htm

http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/crbacid1.htm

http://www.organic-chemistry.org/namedreactions/fischer-esterification.shtm

http://en.wikipedia.org/wiki/Isoamyl_acetate

http://www.chemicalland21.com/specialtychem/perchem/ISO-AMYLACETATE.htm

http://www.osha.gov/SLTC/healthguidelines/isoamylacetate/recognition.html

http://www.davidrowan.com/2008/06/observer-how-technology-is-changing-our.html

http://www.bookrags.com/research/isoamyl-acetate-chmc/

http://www.oxiteno.com.br/aplicacoes/mercados/doc/documento.asp?produtoMarca=140405173772637HFBAAF4E11DH43492&idioma=IN&r=.pdf

http://www.oxiteno.com.br/aplicacoes/mercados/doc/documento.asp?produtoMarca=140405173772637HFBAAF4E11DH43492&idioma=IN&r=.pdf

http://cfr.vlex.com/source/code-federal-regulations-food-drus-1070

http://en.wikipedia.org/wiki/Amyl_alcohol

http://en.wikisource.org/wiki/1911_Encyclopædia_Britannica/Amyl_Alcohols

http://www.highbeam.com/doc/1G1-230438398.html

21. http://en.wikipedia.org/wiki/Acetic_acid

22. Prof. Shakhashiri, “Chemical of the Week, Acetic Acid & Acetic Anhydride”

http://www.scifun.chem.wisc.edu/chemweek/pdf/aceticacid.pdf

23. S. Shanmugam, B. Viswanathan , T.K. Varadarajan, “Esterification by solid acid

catalysts-a comparison”, Journal of Molecular Catalysis A: Chemical 223 (2004)

143–147

24. Saha, B., Teo, H.T.R., Alqahtani, A., "iso-Amyl Acetate Synthesis by Catalytic

Distillation," International Journal of Chemical Reactor Engineering (2005): Vol. 3:

A11.

25. Vogel, I. A., “Text book of Quantitative Inorganic Analysis”, 2nd Edition, Longman

Sc. & Tech, June, 1980

Other Reference Books and Articles

26. Stecher, Paul G., “The Merk Index of Chemicals & Drugs”, 1st Edition, Merck & Co.

Inc. U.S.A., 1960

27. Groggins. H.P, “Unit Process in Organic Synthesis”, 5th Edition, McGraw-Hill,

Kokusha Ltd. Tokyo, 1958

28. Shrieve, N.R., “Chemical Process Industries”, 3rd Edition, McGraw Hill Book

Company, Tokyo, 1946

29. Pakistan Standard Trade, Revision 3, Manager of Publications, Karachi, 2005.

http://en.wikipedia.org/wiki/Acetic_acid

Documents

A Process Report on Comparative Study of Production of Isoamyl Acetate by Fischer Esterification Using Different Catalysts