FORMATION OF POLYOLS FROM PHENOLIC COMPOUNDS IN BIO-OILS

Mé moire

ZHENG FANG

Maîtrise en Gé nie Chimique

Maître è s sciences (M. Sc.)

Qué bec, Canada

© Zheng Fang, 2017

FORMATION OF POLYOLS FROM PHENOLIC COMPOUNDS IN BIO-OILS

Mé moire

ZHENG FANG

Sous la direction de :

Serge Kaliaguine, directeur de recherche

III

RÉSUMÉ

Le polyuréthane (PU) est le polymère synthétique le plus utilisé dans des applications

comme les revêtements, les adhésifs, les élastomères, les mousses et les fibres. De nos

jours, la lignine est utilisée dans la synthèse de PU. Une conversion hautement efficace

mais peu coûteuse de la lignine est un élément clé de l'utilisation commerciale de la

conversion de la biomasse lignocellulosique. L'utilisation de la lignine pour remplacer

une partie de polyols en synthèse de polyuréthane suit deux approches principales: (1)

utiliser directement de la lignine sans modification chimique préliminaire; (2) utiliser la

lignine avec une modification chimique. La lignine modifiée par oxypropylation a été

reconnue comme un procédé efficace pour produire des polyols de lignine. En plus de

la lignine, d'autres composés qui ont les mêmes groupes fonctionnels que la lignine

peuvent être utilisés dans l'industrie de la PU, comme le guaiacol, le phénol et le

catéchol.

Au cours des dernières décennies la diminution des ressources en combustibles fossiles

a suscité des inquiétudes croissantes. La biomasse est considérée comme une matière

première potentielle à utiliser largement et à grande échelle grâce à son énorme

abondance dans la nature. Parmi les technologies thermochimiques pour l'utilisation des

ressources en biomasse, la pyrolyse semble être la plus prometteuse en raison de sa

capacité potentielle à permettre aux fabricants commerciaux d'utiliser la biomasse

lignocellulosique abondante, économique et locale. Un certain nombre de composés

phénoliques préparés par pyrolyse sous vide peuvent être classés en trois groupes

présentant les mêmes groupes fonctionnels que le guaiacol, le phénol et le catéchol.

Dans ce projet, nous avons d’abord étudié la réaction d'oxypropylation du guaiacol en

produisant un produit avec une performance appropriée. Étant donné que le rendement

était même inférieur à 3%, la synthèse d'éther de Williamson a été utilisée comme la

deuxième méthode pour modifier le guaiacol, le phénol et le catéchol. Le rendement

était d'environ 55% à 65%, et les caractérisations étaient également les mêmes que

celles habituellement mentionnées dans la littérature pour les polyols compondants.

IV

ABSTRACT

Polyurethane (PU) is the most wildly used synthetic polymer in many applications like

coatings, adhesives, elastomers, foams, and fibers. Nowadays, lignin is used in the

synthesis of PU. A highly efficient yet low-cost conversion of lignin is a key element in

the commercial utilization of lignocellulosic biomass conversion. Using lignin to replace

part of polyols in polyurethane synthesis follows two main approaches: (1) directly using

lignin without any preliminary chemical modification; (2) using lignin with chemical

modification. Oxypropylation-modified lignin has been recognized as an effective

method to produce lignin polyols. In addition to lignin, some other compounds which

have the same functional groups as lignin can be used in the PU industry, such as

guaiacol, phenol and catechol.

The increasingly reduced availability of fossil fuels has caused increasing concerns

over the last few decades. Biomass is considered a potential raw material to be used

widely and extensively because of its huge abundance in nature. Among the

thermochemical technologies for using biomass resources, pyrolysis seems to be the

most promising due to its potential capacity to enable commercial-scale plants to use

abundant, cheap, and local lignocellulosic biomass. A number of phenolic compounds

prepared by vacuum pyrolysis can be classified into three groups bearing the same

functionalities as guaiacol, phenol, and catechol.

In this project, we have first studied the oxypropylation reaction of guaiacol in producing

a product with suitable performance. Since the yield was even less than 3%, Williamson

ether synthesis was used as a second method for modifying guaiacol, phenol and catechol.

The yield was approximately 55% to 65%, and the characterizations were also the same

as usually mentioned in the literature for the corresponding polyols for the

compounding polyols.

V

Table of Contents

RÉSUMÉ ........................................................................................................................III

ABSTRACT .................................................................................................................. IV

Table of Contents ............................................................................................................. V

List of Figures ............................................................................................................... VII

List of Tables ............................................................................................................... VIII

Acknowledgments ......................................................................................................... IX

CHAPTER 1 .....................................................................................................................1

INTRODUCTION ............................................................................................................1

1.1 Lignin Structure ..........................................................................................................2

1.2 Polyurethane ...............................................................................................................3

1.3 Oxypropylation ...........................................................................................................4

1.4 Williamson Ether Synthesis ........................................................................................5

1.5 Objectives ...................................................................................................................5

CHAPTER 2 .....................................................................................................................2

LITERATURE REVIEW .................................................................................................2

2.1 The Polyurethane Industry ..........................................................................................7

2.2 Oxypropylation of Lignin ...........................................................................................8

2.3 Advantages of Kraft Lignin-based Rigid PU Foams ................................................10

2.4 The Williamson Ether Synthesis Reaction ...............................................................13

2.5 Bio-oils from Pyrolysis Processes ............................................................................16

CHAPTER ３ ..............................................................................................................27

OXYPROPYLATION OF GUAIACOL ........................................................................27

3.1 Experimental .............................................................................................................28

3.1.1 Materials .........................................................................................................28

3.1.2 Apparatus ........................................................................................................28

3.1.3 Procedure ........................................................................................................29

3.1.4 Removal of Propylene Oxide Homopolymer .................................................30

3.1.5 Characterization of Oxypropylated Guaiacol .................................................30

3.1.6 Observation .....................................................................................................30

3.2 Results and Discussion .............................................................................................32

3.3 Conclusions ..............................................................................................................35

CHAPTER 4 ...................................................................................................................36

PHENOLIC FRACTIONS OF BIO-OIL .......................................................................36

4.1 Isolating the Phenolic Fractions from Bio-oil ..........................................................38

4.1.1 Materials .........................................................................................................38

4.1.2 Procedure ........................................................................................................38

4.2 Results and Discussion ......................................................................................38

CHAPTER 5 ...................................................................................................................42

WILLIAMSON ETHER SYNTHESIS WITH PHENOLIC COMPOUNDS AND

CHLOROPROPANEDIOL ............................................................................................42

5.1 Experimental .............................................................................................................43

5.1.1 Materials .........................................................................................................43

5.1.2 Apparatus ........................................................................................................43

5.1.3 Procedure ........................................................................................................43

5.1.4 Characterization ..............................................................................................44

VI

5.2 Results and Discussion .............................................................................................44

5.3 Conclusion ................................................................................................................55

CHAPTER 6 ...................................................................................................................56

CONCLUSIONS AND FUTURE WORK .....................................................................56

6.1 General Conclusions ..........................................................................................57

6.2 Future Work .......................................................................................................58

References ......................................................................................................................59

APPENDIX ....................................................................................................................64

VII

List of Figures

Figure 1.1: Lignin primary precursors [2-4] ..............................................................2

Figure 1. 2: Three phenolic compounds used in this project .....................................5

Figure 2.1: Possible reactions involved in the preparation of PU [18]......................8

Figure 2. 2: Reactions involved in the oxypropylation of lignin [12] .......................8

Figure 2.3: SEM images of rigid PU foams prepared with (a) 0, (b) 10, (c) 30, (d)

60, (e) 100 wt% of Kraft lignin polyol based on the weight of sucrose polyol

of the control foam, and (f) only lignin polyol [12] ........................................12

Figure 2.4: The Williamson ether synthesis of racemic guaifenesin [23] ...............14

Figure 2.5: Representative compounds of bio-oils [53] ..........................................18

Figure 2.6: Representative pyrolysis reactions [57] ................................................20

Figure 2.7: Diagram of the integrated hydroprocessing and zeolite for upgrading

bio-oil [58] .......................................................................................................21

Figure 2.8: The carbon distribution of feed and product (%) in the hydroprocessing

of water-soluble bio-oil (WSBO) and for the zeolite upgrading. (A) WSBO

feedstock distribution; (B) the product from single-stage hydrogenation of

WSBO via Ru/C catalyst at 398 K and 52 bar; (C) the product from two-stage

hydrogenation of WSBO over Ru/C at 398 K and 100 bar first, then over Pt/C

at 523 K and 100 bar; (D) the conversion of various types of feedstock over

HZSM-5 catalyst. [62] .....................................................................................22

Figure 2.9: Pyrolysis of biomass [63] ......................................................................23

Figure 2.10: Procedure for recovering phenolic compounds in Iowa State

University’s bio-oil fractionating recovery system [68, 69] ............................24

Figure 3.1: 100 ml Parr reactor ................................................................................29

Figure 3.2: Temperature changes and reaction time ................................................31

Figure 3.3: Pressure changes and reaction time ......................................................31

Figure 3.4: The dark brown oil after the reaction ....................................................32

Figure 3.5: 300 mg of product isolated from the liquid product of guaiacol ..........33

Figure 3.6: 1H NMR spectrum of guaiacol .............................................................33

Figure 3.7: 1H NMR spectrum of oxypropylated guaiacol .....................................34

Figure 4.1: GC-MS spectrum of toluene extracts ....................................................39

Figure 5.1: Product isolated from the reaction of guaiacol. (Product 1) .................46

Figure 5.2: 1H NMR of the product of reaction of chloropropanediol with guaiacol

.........................................................................................................................47

Figure 5.3: 1H NMR spectrum of phenol ................................................................49

Figure 5.4: 1H NMR of the product of reaction of chloropropanediol with phenol 50

Figure 5.5: 1H NMR of the product of reaction of chloropropanediol with catechol

.........................................................................................................................52

Figure 5.6: 1H NMR of the product from the reaction of guaiacol, phenol and

catechol with chloropropanediol .....................................................................54

VIII

List of Tables

Table 2.1: Formulation optimization experiment setup [12] ...................................10

Table 2.2: Different cream times of rigid PU foams prepared with different

percentages of lignin polyol contents [12] ......................................................13

Table 2.3: Yield strength and compressive modulus of prepared rigid PU foams [12]

.........................................................................................................................13

Table 2.4: Preparation of 3-aryloxy-1-acetoxypropan-2-ones (1a–m) [43] ............16

Table 3.1: Parameters of the oxypropylation test ....................................................31

Table 4.1: Identified chemical components in the toluene extracts from the oil

phase obtained from the pyrolysis of biomass ................................................39

Table 4.2: All identified phenolic compounds in the toluene extracts from the oil

phase obtained from the pyrolysis of biomass ................................................41

IX

Acknowledgments

The successful completion of any project depends on the cooperation among the

individuals working together to achieve the same goal. Many factors are necessary for a

project to succeed. Hard work, proper guidance, adequate investment of time, money

and energy of the concerned individuals are all of primary importance. First and

foremost, I take this opportunity to express my sincere gratitude to Professor Serge

Kaliaguine for giving me the opportunity to work on this project. I am deeply indebted

to Mr. Luc Charbonneau for his guidance and constant supervision. I sincerely thank

him for his constant support and encouragement. I would also like to thank the other

professionals at University Laval for their kind support and help.

Last but not the least, I am also greatly indebted to my dear friends, Kiran and Cong,

who helped me in many ways throughout my master’s studies.

CHAPTER 1

INTRODUCTION

2

1.1 Lignin Structure

Lignin is found in cells, cell walls and among the cells of vascular plants. It is the

second most abundant organic polymer on earth. The name “lignin” is derived from the

Latin word lignum, which means wood. Indeed, lignin constitutes about 15% to 30% of

the wood and gives trees the woody feature. Lignin’s main biological function is

strengthening the structure of wood and conducting water in plant stems. Playing an

important role in plant biology, it is also the most abundant aromatic biopolymer in

nature and a three-dimensional amorphous polymer. The abundant supplies of lignin in

nature and its intrinsic features make it possible to extract it for industrial applications.

Over the years, numerous research projects have been carried out to study lignin’s

chemical structure and its main composition in order to identify its various potential

uses in industrial applications. So far, lignin’s basic chemical composition has been

determined. As an organic substance composed of carbon, hydrogen and oxygen in

different proportions, lignin is composed of phenylpropane units (C9 or C6-C3) linked

together covalently by several types of ether (β-O-4, α-O-4, 4-O-5) and carbon-carbon

bonds. [1]

Figure 1.1: Lignin primary precursors [2-4]

As shown in Figure 1.1 above, from a chemical point of view, three monolignol

monomers, namely p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol, are

methoxylated to different degrees. Some major chemical functional groups are present

3

in lignin, including hydroxyl, methoxyl, carbonyl and carboxyl moieties in various

amounts, depending on the botanic origin. [5]

Although much research has been conducted on lignin for many years, its commercial

uses have not yet been fully studied and explored. Each year, the pulp and paper

industry generates about 55 million tons of lignin around the world, most of which is

burned in recovery furnaces to recover pulping chemicals and energy. [6] Although

people have realized the potential commercial value and the magnitude by which this

natural resource is wasted each year, the existing markets for lignin products remain

quite limited (2%) nowadays. Some niche applications have been primarily focused on

low-value products, such as agents for dispersing, binding, and emulsion stabilization

in the form of water-soluble lignosulphonates prepared with the sulphite pulping

process. [7,8] Given that lignin contains a large number of aliphatic and phenolic

hydroxyl groups, the interest in preparing lignin-modified phenolic resin, epoxy

polymer, acrylics, especially polyurethane has kept increasing among researchers.

1.2 Polyurethane

Polyurethane (PU) is a polymer composed of organic units joined by carbamate links

and is one of the most widely used synthetic polymers. As we know, it is widely used

in the manufacture of coatings, adhesives, elastomers, foams and fibers. [9]

Polyurethane’s numerous applications can be attributed to its predominant and

controlled mechanical and thermal performance. Of course, various applications are

much influenced by the synergistic effect of soft and hard segments of the polymer

matrix, as well as various optional species, such as the chain extender, the cross-linker,

the UV absorber, the light stabilizer, the antioxidant, and the flame retardant. [10]

Polyurethane’s properties may differ because of its chemical components, but its

performance has been recognized in many industries. One of polyurethane’s most

desirable attributes is that it can be turned into foam, such as rigid PU foam, which is a

heavily cross-linked polymer with a closed-cell structure. Some of PU’s highly

desirable properties, such as low density, low thermal conductivity, low moisture

permeability, high dimensional stability, and good adhesive property have found their

4

way into a wide range of applications in construction, refrigeration appliances, and

technical insulation. [11]

Essentially, the main ingredients needed to make polyurethane formed of urethane

linkage are polyols and isocyanates. However, polyurethane can also be formed using

linkages other than urethane bonds, such as allophanate bonds, which can be generated

from the reaction of excess diisocyanates with urethane groups. Moreover, since

isocyanates are highly reactive materials, isocyanate dimerization and trimerization

reactions can also occur. [12]

How to prepare low-cost polyols using abundant and renewable biomass resources has

become an actively studied and hotly discussed subject in the PU industry. Two major

approaches aimed at making more effective and efficient use of lignin in polyurethane

synthesis are being focused on worldwide: (1) directly using lignin (currently the most

common material in the PU industry); (2) making certain chemical modifications, such

as esterification and etherification reactions, in order to make the hydroxyl functions

stronger and more active.

1.3 Oxypropylation

In order to overcome certain technical limitations and constraints in reinforcing lignin’s

properties in PU formulation, chain extension reaction is directly used to produce the

polyol precursor, instead of directly using underivatized lignin. [13-19] Oxypropylation

has been recognized as a promising approach to improving a product’s performance for

synthetic purposes. [20] Especially, direct oxypropylation of lignin under an alkaline

condition is probably more effective and efficient than under an acidic condition [21],

since the reaction under an alkaline condition can provide PU foam with good thermal

properties and dimensional stability even after aging. [22]

5

1.4 Williamson Ether Synthesis

The most important element in producing polyurethane is polyol. Both the

oxypropylation reaction and the Williamson ether synthesis can provide suitable

polyols for polyurethane synthesis (see Scheme 1.1). [23]

Scheme 1.1: The Williamson ether synthesis [23]

1.5 Objectives

In this project, we intend to produce polyols by using the phenolic fraction of a

pyrolytic oil mixture, which is provided by Pyrovac, a biomass pyrolysis company. The

reaction is usually conducted with three typical phenolic model compounds: phenol,

guaiacol and catechol (see Figure 1.2). We have studied the base-catalyzed

oxypropylation reaction of guaiacol, and the Williamson ether synthesis.

Phenol Guaiacol Catechol

Figure 1. 2: Three phenolic compounds used in this project

CHAPTER 2

LITERATURE REVIEW

7

2.1 The Polyurethane Industry

Nowadays, the ever-increasing demand for rigid polyurethane foam is driving the

remarkable progress in the industry. For instance, sucrose polyols and glycerol polyols

are being more widely used than other types. Compared with conventional polyols, the

various applications involving lignin polyols have comparable or even better properties

in products. Of course, more studies in this field are needed to further improve the

applications. [12] Figure 2.1 shows some possible reactions employed in the PU

industry. [18] The first equation shows how polyols are used to make urethane linkages

in PU synthesis.

8

Figure 2.1: Possible reactions involved in the preparation of PU [18]

2.2 Oxypropylation of Lignin

Glasser and his co-workers were the early pioneers in studying the oxypropylation of

lignin (see Figure 2.2). They modified lignin by mainly changing the operating

conditions in order to achieve different reaction results. Often, their operating

conditions required high temperatures and pressures. [24] Some of the reactions they

conducted led to the self-condensation of the lignin macromolecules, which produced

insoluble fractions. They applied the polyols generated by their experimental methods

in PU formulation. [25-31]

Figure 2. 2: Reactions involved in the oxypropylation of lignin [12]

Thus, in the field of PU formulation, for the very first time, oxypropylated lignin was

produced through the reactions illustrated in Figure 2.2 above. This kind of lignin was

actually a by-product of kraft pulping. [32,33] Because of the large amount of aliphatic

and phenolic hydroxyl groups found in lignin, an increasing number of research

projects are focused on preparing lignin-modified phenolic resin, epoxy polymer,

acrylics and polyurethanes. [34-36]

Wu and Glasser [24] studied the oxypropylation of lignin under alkaline conditions at

180ºC by conducting a reaction involving propylene oxide (PO), and PO in

9

combination with several lignin-like model compounds and with kraft lignin in a

300-mL Parr batch reactor equipped with a heating mantle, a mechanical stirrer, a

pressure gauge, a cooling loop, a safety valve, and a thermocouple. KOH was used as

the catalyst.

The reaction finished after about 90 minutes. The reactor content was collected by

dissolution in acetonitrile and then charged with hexane for refluxing. Finally, the

resulting syrup was precipitated into a large excess (ca. 20: l) of water.

It was necessary to analyze the catalyst concentration’s impact on the reaction rate. The

reaction product’s viscosity has been proven quite high, especially at the peak

temperature. As shown in Figure 2.3, as the catalyst concentration rose (0 -

2.6 mmol/mol PO), the reaction rate increased quickly. [24] To some degree, we can

say the catalyst is the most important factor determining the reaction rate. However,

peculiar conditions and exceptions do exist. When KOH concentrations reach above

2.6 mmol/mol PO, it seems the reaction rate reaches its maximum level and stops

increasing.

Figure 2.3: Concentration-time (c-t) curves of propylene oxide (PO) homopolymerization in relation to KOH concentration. [24]

10

2.3 Advantages of Kraft Lignin-based

Rigid PU Foams

To obtain different types of foam made with different proportions of lignin polyol, Y.

Li and A. J. Ragauskas first prepared a kind of control foam using sucrose polyol,

glycerol polyol and polymeric MDI and then replaced sucrose polyol by lignin polyol

because of their similar hydroxyl group properties. The weight percentages of sucrose

polyol were successively changed from 10%, 30%, and 60% to 100%. These two

researchers finally succeeded in obtaining the kind of desired foam using only lignin

polyol and without using additional commercial polyol. Table 2.1 lists the amount of

every component used in each round of foam preparation trial. [12]

By applying the same experimental conditions, they succeeded in preparing Kraft

lignin-based rigid PU foams of different formulations. All the foams’ densities

measured were almost 30 kg m−3. The images in Figure 2.4 show the differences in

close-cell diameter between the 60% and 100% Kraft lignin-based foams (750 µm) and

other foams (650 µm). The PU foam prepared with lignin polyol has been proven better

in construction. Also, the more lignin polyol contents there are, the fewer cream time is

required, as highlighted in Table 2.2. Therefore, it can be concluded that under the

same experimental conditions, lignin polyol has been proven to have higher reactivity

to polymeric MDI.

Table 2.1: Formulation optimization experiment setup [12]

Lignin Sucrose Glycerol Polymeric

Polyol (wt%1) Polyol (g) Polyol (g) MDI2 (g)

0 25.00 15.00 36.37

10 22.50 15.00 36.66

30 17.50 15.00 37.24

11

60 10.00 15.00 36.07

100 0.00 15.00 39.24

Only lignin polyol 0.00 0.00 42.20

1Weight percentage is based on 25.00 g of sucrose polyol used in the control foam.

2Polymeric MDI (PMDI) is a technical grade MDI, which contains 30% to 80 % w/w

4,4'- methylene diphenyl isocyanate.

12

Figure 2.4: SEM images of rigid PU foams prepared with (a) 0, (b) 10, (c) 30, (d) 60, (e) 100 wt% of Kraft lignin polyol based on the weight of sucrose polyol of the control foam, and (f) only lignin polyol [12]

13

Table 2.2: Different cream times of rigid PU foams prepared with different percentages of lignin polyol contents [12]

Table 2.3 [12] shows the yield strength and the compressive modulus of all the PU

foams. Both the strength and the modulus slightly increased at 10% and 30% lignin

polyol contents, and then dropped below the values of the control foam at 60% and

100% lignin polyol contents, which also demonstrates lignin polyol’s advantage.

Table 2.3: Yield strength and compressive modulus of prepared rigid PU foams [12]

Lignin Polyol (wt%) Strength (MPa) Modulus (MPa)

0 0.10 ± 0.01 1.45 ± 0.07

10 0.10 ± 0.01 1.56 ± 0.05

30 0.11 ± 0.01 1.58 ± 0.05

60 0.10 ± 0.01 1.13 ± 0.01

100 0.09 ± 0.01 1.11 ± 0.03

Only lignin polyol 0.14 ± 0.01 3.41 ± 0.39

2.4 The Williamson Ether Synthesis

Reaction

Lignin Polyol (wt%) Cream Time(s)

0 40

10 38

30 34

60 26

100 23

Only lignin polyol 17

14

Producing polyols with suitable performance is a key element in PU synthesis. Two

methods can be used to provide polyols: (1) conducting the oxypropylation reaction

between lignin (or lignin model compounds) and propylene oxide; (2) conducting the

Williamson ether synthesis with phenolic compounds.

Over the past 150 years, the Williamson ether synthesis reaction between an alkoxide

(or a phenoxide anion) and a sterically unhindered alkyl halide has been extensively

studied. [23] This reaction is a subject of discussion in virtually every introductory

organic chemistry textbook. [37-39] Quite a few published micro-scale laboratory

procedures also illustrate this fundamental reaction. [40,41]

Figure 2.3: The Williamson ether synthesis of racemic guaifenesin [23]

Figure 2.4 [23] above shows the small-scale synthesis of racemic guaifenesin using the

Williamson method. As shown in this figure, by reacting with (+)- or

(−)-3-chloro-1,2-propanediol, phenol can achieve chain extension and form two alcohol

hydroxyl groups. By replacing one phenolic hydroxyl group, two hydroxyl groups

become suitable for PU synthesis.

Stabile and Dicks [41] successfully conducted this reaction by using the following

15

procedure. Instead of conducting an 8-hour reaction as reported in 1950 [42], they

modified the procedure. Guaiacol (2-methoxyphenol, 550 µL, 5 mmol) was dissolved

in 3 mL 95% ethanol, and a solution containing 250 mg (6.25 mmol) of crushed NaOH

pellets in 1 mL of water was added. The mixture was heated under reflux for 10

minutes. Then, a mixture of 500 µL (±)-3-chloro-1,2-propanediol (5.98 mmol) in 0.5

mL of 95% ethanol was added dropwise to the phenoxide anion and the reflux

continued for 1 hour. The, the ethanol was removed under vacuum, and 3 mL of water

was added to dissolve the precipitated NaCl. The aqueous solution was extracted twice

with 10 mL of ethyl acetate, and the organic layer was dried using MgSO4. Removal of

the drying agent and the solvent under vacuum produced a pale yellow oil, which was

then solidified by adding 10 mL of hexanes while being cooled and stirred in an

ice-bath. This crude solid was collected by vacuum filtration and was recrystallized

from ethyl acetate and hexanes to yield 450 mg to 600 mg of white crystals (45% to

60% yield); mp 78–79 oC (78.5–79.5 oC); 1H NMR (CDCl3,): 2.58 (t, 1H), 3.30 (d, 1H),

3.75–3.9 (m, 5H), 4.03–4.20 (m, 3H), 6.86– 7.05 (m, 4H);13C NMR (CDCl3): 56.05,

64.07, 70.38, 72.02, 112.08, 114.76, 121.35, 122.28, 148.22, 149.76. [42]

Egri et al. [43] studied the reaction between phenyl, benzyloxymethyl, azidomethyl and

(±)-3-Chloro-1,2-propanediol. The 3-aryloxy-1-acetoxypropan-2-ones 1a–m were

prepared by alkylation of the corresponding phenols (3a–m) with racemic

3-chloropropane-1,2-diol rac-2 as shown in Table. 2.4 below. Since this kind of

reaction can be conducted by using most of the phenolic compounds, it can become

another way to produce polyols.

16

Table 2.4: Preparation of 3-aryloxy-1-acetoxypropan-2-ones (1a–m) [43]

2.5 Bio-oils from Pyrolysis Processes

Over the past few decades, the continuous reduction of the available fossil fuels has

caused increasing concern. Environmental problems, such as climate change and

pollution caused by fossil fuel use, have become truly global issues. The need to find

solutions for these issues has motivated researchers and scientists to study how to best

utilize renewable energy resources, including nuclear, solar, geothermal, hydropower,

wind and biomass.

17

Among these sustainable resources, biomass is considered as a potential raw material to

be extensively applied because of its abundant supplies in nature. Biomass can be

converted into several forms of energy through direct combustion, gasification,

fermentation, syn-gas utilization and pyrolysis. [44] Compared with the other methods

just mentioned, pyrolysis seems to be the most promising thermochemical technology

because of its potential application in commercial-scale plants that use abundant cheap

local lignocellulosic biomass. [45-50]

Pyrolysis is a thermochemical process for decomposing biomass at temperatures

ranging from 275oC to 650oC without oxygen. The products yielded by this reaction

contain volatile species, as well as solid and non-volatile species. While those

non-volatile species are being collected as bio-char, a portion of the gas-phase volatile

species is condensed into a black, viscous fluid called “bio-oil”, which is also called by

various other synonyms, such as pyrolysis oil, wood liquid, wood oil, bio-crude oil,

biofuel oil, pyroligneous acid. [51] To a considerable extent, bio-oils’ properties

depend on the parameters of the conditions of the reaction process. Even a small

change made to the temperature, the residence time and the heating rate can

dramatically affect the respective percentages of gas, char, and liquid in the final

products. A long residence time at low temperatures produces mainly gas products,

whereas a short residence time and moderate temperatures may yield liquid products.

An optimal match-up of the residence time and the temperature is needed to produce

the desired intermediate. Based on the differences in these parameters, the pyrolysis

methods can be grouped into two types: slow pyrolysis and fast pyrolysis. The fast

pyrolysis process is a promising technology for producing high liquid yield. [51,52].

Table 2.5 summarizes the key characteristics of the fast pyrolysis process.

The slow pyrolysis process produces a large amount of biochar, which is usually used

as a solid fuel. Unlike slow pyrolysis, fast pyrolysis can produce bio-oils in very high

yields. The bio-oils are a mixture of numerous different compounds, including

carboxylic acids, alcohols, aldehydes and hydroxyaldehydes, hydroxyketones,

furan/pyran ring containing compounds, anhydrosugars, phenolic compounds and

oligomeric fragments of lignocellulosic polymers (see Figure 2.5). [53] The

thermochemical reactions taking place under the fast pyrolysis conditions are extremely

18

complicated to be thoroughly understood because of the complex compositions of

biomass feedstock and the relatively wide range of reaction temperatures.

Figure 2.4: Representative compounds of bio-oils [53]

19

Table 2.5: Key characteristics of the fast pyrolysis process [52]

Pretreatment

Particle size

Feed-drying

Washing and additives

Small particles needed; expensive

essential to ≈ 10%

for chemical production

Reaction

Heat supply

Heat transfer

Heating rates

Reaction temperature

Reactor configuration

High heat transfer rate needed.

Gas-solid and/or solid-solid.

Wood conductivity limits the heating

rate.

500oC maximizes liquids from

wood.

Many configurations have been

invested in and developed.

Product Conditioning and Collection

Vapor residence time

Secondary cracking

Char separation

Liquid collection

Critical for chemicals, less for fuels.

Reduces yields.

Difficult from vapor or liquid.

Difficult and quenching seems best.

Over the past few decades, a huge amount of research has been done on the

thermochemical reactions involved in the pyrolysis process and more than 300

individual compounds have been identified. [54-56] These reaction methods can be

generally classified into several common types: dehydration, depolymerization,

fragmentation, rearrangement, re-polymerization and condensation (see Figure 2.6).

[57]

20

Figure 2.5: Representative pyrolysis reactions [57]

Pyrolysis oils can be converted to a renewable chemical commodity through

integrated catalytic processing, in which zeolite is used to enhance the proportions of

aromatic hydrocarbons and light olefins in the products. [58,59] Huber et al.

established a strategy to hydrogenate various types of bio-oil into commodity

chemicals, such as C2 to C4 olefins with over 60% carbon yields, C2 to C6 alcohols

and C6 to C8 aromatic hydrocarbons. Their hydrotreating process involves a

multi-stage process using first supported metals catalysts and followed by a zeolite

catalyst such as HZSM-5 (Figure 2.7) [58].

21

Figure 2.6: Diagram of the integrated hydroprocessing and zeolite for upgrading bio-oil [58]

Huber and his co-workers experimented with three types of process under different

conditions (see Figure 2.8). [62] Ru/C is the most active and selective catalyst for

acetic acid hydrogenation at a low temperature, while Pt provides high C-O

hydrogenation and low C-C bond cleavage reactivity. [60,61] Overall, the two-stage

exhibits more efficient conversion of Water Soluble Bio-Oil (WSBO) to gasoline cut 1,

gasoline cut 2 and C2 to C6 diols as 45.8%, compared with 29.4% in the single-stage

(Figure 2.8 B,C). Gasoline cut 1 consists of small monohydric alcohols and gasoline

cut 2 includes C4 to C6 alcohols.

22

Figure 2.7: The carbon distribution of feed and product (%) in the hydroprocessing of water-soluble bio-oil (WSBO) and for the zeolite upgrading. (A) WSBO feedstock distribution; (B) the product from single-stage hydrogenation of WSBO via Ru/C catalyst at 398 K and 52 bar; (C) the product from two-stage hydrogenation of WSBO over Ru/C at 398 K and 100 bar first, then over Pt/C at 523 K and 100 bar; (D) the conversion of various types of feedstock over HZSM-5 catalyst. [62]

Elliott et al. studied hydroprocessing of fractionated phenolic oils obtained by fast

pyrolysis. Phenolic oils were produced by fast pyrolysis using two different biomass

feedstocks, red oak and corn stover. The phenolic oils were produced by a bio-oil

fractionating process in combination with a simple water wash of the heavy ends from

the fractionating process (see Figure 2.9). [63]

23

Figure 2.8: Pyrolysis of biomass [63]

Lindfors et al. [64] used fractionation of bio-oil prior to upgrading as a more efficient

way to produce liquid fuels, instead of treating whole bio-oil. In comparison with the

water-soluble phase of bio-oil, the water-insoluble phase is more difficult to upgrade

because of high-molecular-weight aromatic structures derived from pyrolysis of the

biomass lignin fraction. Effective bio-oil fractionation prior to upgrading may be a

valuable approach to producing liquid fuels and chemicals, instead of upgrading whole

bio-oil. [65]

Iowa State University [66,67] has developed a fractionating bio-oil recovery system

that allows for collecting bio-oil as heavy-ends (stage fraction or SF 1 and SF 2),

intermediate fractions (SF 3 and SF 4) consisting of monomeric compounds, and light

ends (SF 5) containing the majority of acids and water (see Figure 2.10). [68, 69]

24

Figure 2.9: Procedure for recovering phenolic compounds in Iowa State University’s bio-oil fractionating recovery system [68, 69]

To examine the content of this fraction, GC-MS and GC-FID analyses were performed

on the oil phases to characterize the extracted chemical compounds obtained from

pyrolysis of lignin. [70] Table 2.6 lists the 41 organic compounds that were identified

using this analytical technique. These chemicals were subsequently categorized into

five groups: benzenes, phenols, guaiacols, catechols and others.

25

Table 2.6: Identified chemical components in the oil phase obtained from pyrolysis of lignin [70]

CP0: Conventional pyrolysis at 0 wt% char mixed with the raw material.

CP30: Conventional pyrolysis at 30 wt% char mixed with the raw material.

MWP0: Microwave pyrolysis at 0 wt% char mixed with the raw material; and

MWP30: Microwave pyrolysis at 30 wt% char mixed with the raw material.

26

There are many phenolic fractions in the bio-oil, which can be used in the

modification via the Williamson ether synthesis reaction.

For this project, the bio-oil used was prepared by vacuum pyrolysis, which also

contains a huge amount of phenolic fractions. J. Gagnon and S. Kaliaguine introduced

a very low-temperature hydrotreating process, which was performed at 80oC over a

5% Ru on γ-alumina. [71] Another catalyst, copper chromite, was also tested, but its

performance was poor in this process. The experimental procedure involved two

stages. At the first stage, 20 g of Ru catalyst was introduced to a stirred batch reactor

holding 400 g of vacuum-pyrolysis oil and the reaction went on for 2 hours. At the end

the 2 hours, the reactor was cooled down, opened and 12 g of NiO-WO3/γ-Al2O3 was

added for the second stage at 325oC and 2,500 psig.

Figure 2.11: Schematic diagram of experimental setup: 1, reactor; 2, turbine; 3, magnetic stirrer; 4, belt; 5, motor; 6, reactor head; 7, thermowell; 8, heating bands; 9, temperature controller; 10, gas feed; 11, mass flow controller; 12, compressor; 13, gas inlet; 14, pressure gauge, 0-500 psig; 15, pressure gauge; 16, liquid sampling; 17, gas sampling. [71]

CHAPTER ３

OXYPROPYLATION OF GUAIACOL

28

3.1 Experimental

Guaiacol, which, like lignin, also has the phenolic hydroxyl group, was used in the first

experiment. Additionally, it is one of the most abundant parts in phenolic fractions

from pyrolysis of bio-oil. In order to make a chain extension reaction on guaiacol to

produce polyol, oxypropylation (Equation 3.1) was used.

( 3.1)

3.1.1 Materials

Guaiacol and propylene oxide were purchased from Sigma-Aldrich Chemicals.

Potassium hydroxide commercial pellets were also purchased from Sigma-Aldrich

Chemicals and were crushed into a fine powder.

3.1.2 Apparatus

The oxypropylation reaction was conducted in a 100 ml Parr reactor equipped with a

heating mantle, a mechanical stirrer, a pressure gauge, a cooling loop, a safety valve

and a thermocouple.

29

Figure 3.1: 100 ml Parr reactor

3.1.3 Procedure

The 100 ml Parr reactor was charged with propylene oxide, guaiacol and KOH in

appropriate ratios and was sealed. Guaiacol (0.1 mol) and propylene (0.1 mol) oxide

were charged in the molar ratio of 1:1. The reactor was heated to 140°C. After the

reaction, the reactor content was collected by dissolution in 25 ml of acetonitrile. The

reaction product was a dark brown viscous liquid, with no solid particles present. The

isolation of oxypropylated guaiacol from propylene oxide oligomers was carried out

using a liquid-liquid extractor, with a reflux apparatus. A rotary evaporator was used to

remove excess solvent.

30

3.1.4 Removal of Propylene Oxide Homopolymer

The reaction product dissolved in 25 ml acetonitrile was extracted with refluxing hot

hexane 3 times. [72-74] Subsequent by the product was poured into a liquid-liquid

extractor with a 120 ml capacity. After extraction, the acetonitrile layer was

concentrated to a 25% solution using a rotary evaporator. Then, the resulting syrup was

precipitated into a large excess of water. The resulting product was refrigerated for 24

hours and then filtered and dried in an oven at 40°C for 48 hours.

3.1.5 Characterization of Oxypropylated Guaiacol

Nuclear magnetic resonance (NMR) spectra were recorded on a Varian Inova AS400

spectrometer (Varian, Palo Alto, USA). 1H NMR spectra were acquired on dry samples

(20 mg) in DMSO (450 µL).

3.1.6 Observation

As shown in Figure 3.2 and Figure 3.3, at first, due to the boiling point of propylene

oxide (34oC), the pressure gradually rose as the temperature increased. Once the

temperature reached 140°C, the pressure increased to a maximum value of 175 psi in

seconds and then quickly returned to 0 in less than 20 minutes, which indicated the

completion of the reactants.

31

Figure 3.2: Temperature changes with reaction time

Figure 3.3: Pressure changes with reaction time

Table 3.1 shows the parameters of the test. During the reaction, the maximum

temperature was 218oC, and the maximum pressure was 175 psi.

Table 3.1: Parameters of the oxypropylation test

1Tset is the reaction setting temperature.

2The reaction time was recorded from the moment when the temperature was set at

140°C to the moment when the pressure reached 0 psi.

Guaiacol Propylene Potassium Tset1 Tmax Pmax Time2

(g) oxide (mL) hydroxide (g) (◦ C) (◦ C) (psi) (min)

8 5 0.24 140 218 175 20

32

The end result was a dark brown oily layer. (Figure 3.4)

Figure 3.4: The dark brown oil obtained after the reaction

3.2 Results and Discussion

The obtained materials in the oxypropylation reaction of guaiacol in the conditions

discussed above contained a very low amount of crystals: only 300 mg, or less than 3%

(see Figure 3.5) The dried powder was collected for NMR analysis.

33

Figure 3.5: 300 mg of product isolated from the liquid product of guaiacol

Figure 3.6: 1H NMR spectrum of guaiacol

34

Figure 3.7: 1H NMR spectrum of oxypropylated guaiacol

35

The 1H NMR spectra were recorded on a Bruker AW-250 spectrometer operating at

400MHz. All spectra were taken in a CDCl3 solution. Figure 3.6 shows the 1H NMR of

starting guaiacol: peak of CH3 groups at 3.794 ppm, peak of –OH groups at 5.83 ppm,

and peak of ArH at around 6.8-6.9 ppm. Compared with the starting guaiacol (see

Figure 3.6), the oxypropylated guaiacol exhibited differences in the 1H NMR spectral

data (see Figure 3.7). The structure of the product can be seen below (Eq. 3.2). As we

can see the peak of phenolic OH groups at 5.8 ppm disappeared. The spectrum shoes

new peaks of CH3 groups at 1.0 ppm, CH2 groups at 3.4 ppm, and CH groups at 3.7

ppm, which were also seen by Nadji et al in the 1H NMR analysis of oxypropylated

lignin. [22] Protons from aromatic rings (6.3–7.7 ppm) were also clearly identified,

which confirmed the structure of the product obtained.

(3.2)

3.3 Conclusions

Due to the competitive homopolymerization of propylene oxide, the yield was very

low. The reaction between guaiacol and propylene oxide resulted in a very small

amount of crystals (300 mg). As a result, this reaction was not successful. To obtain

better results, the method needs to be improved. We preferred to test another method of

polyols production by Williamson etherification.

CHAPTER 4

PHENOLIC FRACTIONS OF BIO-OIL

38

4.1 Isolating the Phenolic Fractions from

Bio-oil

4.1.1 Materials

The bio-oil used in this project was prepared by the company Pyrovac Inc, which

conducted pyrolysis of wood type 80% pine and 20% mixture of fir and spruce at

475oC under atmospheric temperature. Pyrovac obtained 57.6% oil (including water),

24.8% solid and 17.5% gas. The pyrolysis oil was composed of two phases: the oil

phase, and the aqueous phase which contained 55.4% water-soluble organic

compounds. The materials used for this project was the aqueous phase of the pyrolysis

oil (The batch number was 50KG-2016-05-26-BR-UF-475). Toluene was used as the

solvent for phenolic compounds extraction.

4.1.2 Procedure

For extraction purposes, 75 ml of toluene was added as the solvent into 100g of the

dark black bio-oil. At the end of the first round of extraction, a layer of toluene

containing the desired phenolic fractions came to the top. Then, the lower oily layer

was collected and extracted a second time. The two toluene solutions were then

combined in a 500 ml flask, and toluene was removed by rotary evaporation. The

product was sent for GC-MS analysis.

4.2 Results and Discussion

Figure 4.1 shows the GC-MS spectrum from the bio-oil toluene extracts. Table 4.1 lists

39

most of the organic compounds that were identified using this analytical technique

according to the retention time. These chemicals were categorized into five groups:

benzenes, phenols, guaiacols, catechols, and others. As shown in Table 4.2, most of the

fractions are phenolic compounds. The fraction of peak area of these compounds

represents 70% of all identified products in this toluene extract. For all these phenolics

the reaction with chloropropanediol by using the Williamson ether synthesis reaction is

a priori possible.

5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00

200000

400000

600000

800000

1000000

1200000

1400000

1600000

1800000

2000000

2200000

Time-->

Abundance

TIC: 020301.D

Figure 4.1: GC-MS spectrum of toluene extracts

Table 4.1: Identified chemical components in the toluene extracts from the oil phase obtained

from the pyrolysis of biomass

RT Chemical Components Peak Area%

3.79 Toluene 4.03

5.15 2-Furancarboxaldehyde 1.27

5.84 Acetoxyacetone 0.746

40

6.53 2-Methyl-2-cyclopenten-1-one 1.635

6.79 2-Furanone 2.206

6.97 1,3-cyclopentanedione 1.084

7.69 3-Methyl-2-cyclopenten-1-one 2.906

7.95 2-furanone, 3-methyl 1.07

8.10 Phenol 1.739

8.35 3-Pyridazinone, 4,5-dihydro-6-methyl 1.032

8.86 2-cyclopenten-1-one, 2-hydroxy-3-methyl 5.711

8.98 unknow 1.173

9.41 o-Methyl-phenol 3.311

9.85 p-Methyl-phenol 3.807

10.00 Guaiacol 6.404

10.58 unknow 1.31

11.27 2,4-Dimethylphenol 3.38

11.68 p-Ethylphenol 3.3

12.13 p-Methylguaiacol 9.103

12.51 Catechol 6.54

13.19 2-Ethyl-5-methylphenol 3.162

13.90 3-Methylcatechol 3.73

14.01 4-Ethylguaiacol 5.093

14.62 4-Methylcatechol 5.026

15.86 4-Propenylguaiacol 4.839

16.07 p-Propylguaiacol 2.344

16.82 4-Ethylcatechol 4.752

17.12 4-Propenylguaiacol 3.813

18.19 4-Propenylguaiacol 4.222

19.01 4-Propylcatechol 2.224

19.14 Apocynin 1.427

20.09 Homovanillic acid 1.182

41

Table 4.2: All identified phenolic compounds in the toluene extracts from the oil phase obtained

from the pyrolysis of biomass

RT Chemical Components Peak Area%

Phenols

8.1 Phenol 1.739

9.41 o-Methyl-phenol 3.311

9.85 p-Methyl-phenol 3.807

11.27 2,4-Dimethylphenol 3.38

11.68 p-Ethylphenol 3.3

13.19 2-Ethyl-5-methylphenol 3.162

Guaiacols

10 Guaiacol 6.404

12.13 p-Methylguaiacol 9.103

14.01 4-Ethylguaiacol 5.093

15.86 4-Propenylguaiacol 4.839

16.07 p-Propylguaiacol 2.344

17.12 4-Propenylguaiacol 3.813

18.19 4-Propenylguaiacol 4.222

Catechols

12.51 Catecol 6.54

13.9 3-Methylcatecol 3.73

14.62 4-Methylcatecol 5.026

16.82 4-Ethylcatecol 4.752

19.01 4-Propylcatecol 2.224

CHAPTER 5

WILLIAMSON ETHER SYNTHESIS

FROM PHENOLIC COMPOUNDS

43

5.1 Experimental

As shown in Chapter 4, the main compounds of the bio-oil toluene extract are phenolic

compounds. Guaiacol, phenol and catechol are three typical compounds of this bio-oil

considered for this project. To deal with these fractions, the experiment of Williamson

etherification was performed with guaiacol, phenol and catechol.

5.1.1 Materials

Phenol, guaiacol, catechol and (±)-3-Chloro-1,2-propanediol (3-MCPD) are commercial

chemicals purchased from Sigma-Aldrich Chemicals. Potassium hydroxide commercial

pellets were also purchased from Sigma-Aldrich Chemicals and were crushed into a fine

powder.

5.1.2 Apparatus

The oxypropylation by Williamson etherification reaction was conducted at atmospheric

pressure in a 250 ml two-neck flask equipped with magnetic stirrer and hot plate, a

water condenser and a thermocouple.

5.1.3 Procedure

Into the solution of 0.1 mol phenolic compound in ethanol (60 ml), a solution of NaOH

(5.0g, 0.125 mol) in water (20 ml) was added and the resulting mixture was heated

under reflux for 30 minutes. Then, a solution of 3-chloropropane-1,2-diol, 0.12 mol in

44

ethanol (10 ml) was added within 5 minutes and the mixture was further heated under

reflux (70oC) for 2 to 3 hours. After cooling, the volume of the resulting mixture was

reduced using a rotary evaporator; then, 60 ml of water was added and extraction was

performed with chloroform (2×75 ml). Removal of the solvent produced a pale yellow

oil, which was precipitated in 200 ml of toluene with cooling and stirring in an ice-bath.

This solid was recrystallized from ethyl acetate.

5.1.4 Characterization

The 1H NMR spectra were recorded on a Bruker AW-250 spectrometer operating at

250MHz. All spectra were taken in a CDCl3 solution.

5.2 Results and Discussion

Etherification of guaiacol

The first reaction test was conducted with guaiacol. The structure of the product is

shown on the right side of Equation 5.1 below. The molecular mass of the product

(product 1) is 198g/mol. The mass of crystals produced was 12g. It is a fine and white

powder (see Figure 5.1). The yield obtained of crystalline Product 1 was 65%. The dried

powder was collected for 1H NMR analysis (see Figure 5.2).

45

( 5.1 )

Product 1

In the NMR spectrum of the starting guaiacol (Figure 3.6), the peak of CH3 groups is at

3.794 ppm, the peak of –OH groups is at 5.83 ppm, and the peak of ArH groups is at

around 6.8-6.9 ppm. It can be easily found that the peak corresponding to the phenolic

hydroxyl groups has completed disappeared as expected. After the reaction, the product

exhibited apparent differences in the 1H NMR spectral data. Peaks at 3.77-3.82 ppm

correspond to the CH2-OH groups. The highest peak at 3.86 ppm corresponds to the

O-CH3 groups. The peak at 4.04-4.07 ppm corresponds to the ArO-CH2 groups. The

peak at 4.15-4.19 ppm corresponds to the CH groups. Peaks at 6.89-7.0 correspond to

the ArH, which were also seen in the literature [43]. The ratio of the peak area is 2:3:2:1,

which is the same as the ratio of the proton in each group in product 1. The 1H NMR

spectra confirmed the structure of the product obtained.

46

Figure 5.1: Product isolated from the reaction of guaiacol. (Product 1)

47

Figure 5.2: 1H NMR of the product of reaction of chloropropanediol with guaiacol

48

Etherification of phenol

The second reaction test was conducted with phenol. The structure of the product

(product 2) is shown on the right side of Equation 5.2. The molecular mass of the

product is 168g/mol. The amount of crystals was 9.3 g. The yield obtained from the

crystals was 55%. The dried powder was collected for 1H NMR analysis (see Figure

5.4)

(5.2)

Product 2

Compared with the starting phenol (Figure 5.3), by looking at the peak of –OH groups

at 5.35 ppm, and the peak of ArH groups at around 6.8-7.2 ppm, it can be easily found

that the peak corresponding to the phenolic hydroxyl group also disappeared. After the

reaction, the product exhibited apparent differences in the 1H NMR spectral data. The

peaks at 3.30-3.41 ppm correspond to the CH2-OH groups. The peak at 3.73-3.82 ppm

corresponds to the ArO-CH2 groups. The peak at 3.92-3.95 ppm corresponds to the CH

groups. The peaks at 6.85-7.25 correspond to the ArH, which were also seen in the

literature [43]. The 1H NMR spectra confirmed the structure of the product obtained.

It can also be seen that the peak at 1.05 ppm corresponds to the ethanol (solvent), and

the peak at 2.5 ppm corresponds to the toluene (solvent). There are two hydroxyl groups

in the product’s structure, which is not that much stable. Side reaction happened in this

experiment due to the high temperature during the reaction or purification. A small

49

amount of the product became the compound, as shown below (Eq. 5.3). The two peaks

can be found at 4.62 ppm and 4.89 ppm, which correspond to the two protons in =CH2

groups.

(5.3)

Figure 5.3: 1H NMR spectrum of phenol

50

Figure 5.4: 1H NMR of the product of reaction of chloropropanediol with phenol

51

Etherification of catechol

The third reaction test was conducted with catechol. The structure of the product is

shown on the right side of Equation 5.4 below. After purification, the product became a

light yellow liquid (12g, yield 46.5%), which was different from the products of the

reactions using guaiacol and phenol. The yellow liquid product was directly collected

and sent for 1H NMR analysis (see Figure 5.5)

( 5.4)

It can be found that the peak corresponding to the phenolic hydroxyl group (5.35 ppm)

also disappeared. As shown in Figure 5.5, the peaks at 3.34-3.44 ppm correspond to the

CH2-OH groups. The peaks at 3.77-3.80 ppm correspond to the ArO-CH2 groups. The

peaks at 3.93-3.95 ppm correspond to the CH groups. The peaks at 6.54-6.86

correspond to the ArH. New peaks arose at 8.59 ppm and 8.74 ppm, which are still

unknown. The peaks at 1.00-1.05 ppm correspond to the ethanol, and the peaks at

2.45-2.46 ppm correspond to the toluene. The relative intensity of the aromatic groups’

peaks increased because of the remaining chloroform (the solvent).

52

Figure 5.5: 1H NMR of the product of reaction of chloropropanediol with catechol

53

Etherification of a mixture of phenolic compounds

A fourth test was conducted with a mixture of guaiacol, phenol and catechol. The molar

ratio of these three compounds was 1:1:1. After purification, the product also was liquid,

(11.2g, yield 53.8%) which could not be solidified. The liquid product was collected and

sent for 1H NMR analysis (see Figure 5.6).

As shown in Figure 5.6, none of the peaks of phenolic hydroxyl groups remained after

the reaction (about 5.5 ppm). Compared with the spectra of the products from the

reactions using guaiacol, phenol and catechol, the relative intensity of the aromatic

groups at around 3.5-4.0 ppm increased significantly, which indicated the high content

of alcoholic functions, which came from chloropropanediol. The chain extension

reaction was successful.

54

Figure 5.6: 1H NMR of the product from the reaction of guaiacol, phenol and catechol with chloropropanediol

55

5.3 Conclusion

Phenol, guaiacol and catechol are the most common compounds present in bio-oil. They

are also the three typical phenolic compounds used to produce polyols on this research

project. By using them as well as their mixture, chain extension has been achieved. The

products (polyols) contain at least 2 –OH groups per molecule, which is a significant

result and suggests highly encouraging prospects for developing commercial materials

for the polyurethane industry using these compounds.

CHAPTER 6

CONCLUSIONS AND FUTURE WORK

57

6.1 General Conclusions

Polyurethane is a wildly used material in many applications. Over the years, numerous

studies have been conducted on how to produce high-performance PU products by

adding polyols in the polyurethane structure. Therefore, preparing low-cost polyols is

becoming an increasingly important undertaking in developing the commercial value

of the PU industry. Oxypropylated lignin and its model compounds have already been

used in producing lignin polyols. In this respect, it has been proven that polyols

prepared with phenolics can be used as new materials in PU formulation. All the

phenolic compounds studied in this project were from pyrolysis of biomass.

1. Oxypropylation of guaiacol with propylene oxide

a) Oxypropylation reaction took place on guaiacol.

b) Both homopolymerization and copolymerization happened during the

oxypropylation of guaiacol. Propylene oxide was simultaneously converted to a

homopolymer during this reaction, which is not desired.

c) Due to the side reaction, the yield was very low, which means new ideas should be

found to solve this problem.

2. Formation of phenolic compounds from bio-oil

a) After pyrolysis of biomass, a large amount of bio-oil is produced. High contents of

phenolic compounds led to the idea of producing polyols. The isolation procedures

are described in Chapter 4.

b) After isolation, most of the fractions were phenolic compounds. There were still

some other components, which are not ideal materials for the reaction.

c) After the phenolic fractions were isolated from bio-oil, a reaction using

chloropropanediol was also tried. Due to the presence of those undesired

58

components, the reaction was not successful. The GC-MS results show that none of

the desired products was produced after the reaction (see the Appendix)

3. Reaction with chloropropanediol

a) This is a new method for providing hydroxyl groups from a phenolic structure.

Instead of adding one alcoholic OH group in each molecule by the oxypropylation

reaction, the reaction with chloropropanediol provides two OH groups.

b) As shown in the 1H NMR spectra in Chapter 5, this reaction was highly successful.

After this reaction, guaiacol phenol and catechol all achieved chain extension with

reasonable yields.

c) In addition to lignin polyols, these new products can be used in polyurethane

synthesis due to the existence of the OH groups.

d) From the 1H NMR spectrum, some peaks which were not expected were also found.

To avoid peaks from toluene and ethanol, better purification procedures should be

used. The =CH2 groups which are formed by partial dehydration can be avoided by

decreasing both the reaction temperature and the rotary evaporation temperature.

6.2 Future Work

Further studies should be done to focus on isolating the phenolic compounds from

bio-oil. Once no other compound remains, this fraction should be used to produce

phenolic polyols by using the method described in this project, and finally introduce this

method into polyurethane synthesis.

59

References

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Reactions. ed. Sarkanen, K.V. and Ludwig, C.H. Wiley-Interscience: New York.

916 pp. (1971).

2. Chakar, F.S.; Ragauskas, A.J. Review of current and future softwood kraft lignin

process chemistry. Ind. Crop. Prod. 2004, 20, 131–141.

3. Zakzeski, J.; Bruijnincx, P.C. A.; Jongerius, A.L.;Weckhuysen, B.M. The Catalytic

valorization of lignin for the production of renewable chemicals. Chem. Rev. 2010,

110, 3552–3599.

4. Borges da Silva, E.A.; Zabkova,M.; Araujo, J.D.; Cateto, C.A.; Barreiro, M.R.;

Belgacem,M.N.; Rodrigues, A.E. An integrated process to produce vanillin and

lignin-based polyurethanes from Kraft lignin. Chem. Eng. Res. Des. 2009, 87,

1276–1292.

5. Lee, H. V., et al. "Conversion of Lignocellulosic Biomass to Nanocellulose:

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APPENDIX

a

After phenolic fractions were extracted from bio-oil, a reaction was also tried, using the

Williamson ether synthesis. The reaction took place between the phenolic fractions (see

Table 4.1) and chloropropanediol. The procedure is described in Chapter 5. After the

reaction, the product was a very thick black liquid. Although the same purification

method as mentioned in Chapter 5 was used, there was no precipitation. The black

liquid product was directly sent for GC-MS analysis, which was performed in

Université Laval’s Chemistry Department. The results are shown below. Pages b-k are

from the first GC-MS analysis, where Page b shows the results of GC and Pages c-k

show the results of MS. Pages i-s are from the second GC-MS analysis, where Page i

shows the results of GC and Pages j-s show the results of MS. From the MS results of

both analyses, it was found that the phenolic compounds did not react with

chloropropanediol and were still there. Compared with the GC-MS results of the

starting materials (Table 4.1), the differences shown by the nonphenolic compounds

were not expected to be there. These compounds became polymers after the reaction,

which made the liquid very viscous. The reaction failed between the phenolic fractions

and chloropropanediol. The nonphenolic compounds should have been removed first.

b

c

d

e

f

g

h

i

j

k

l

m

n

o

p

q

r

s