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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

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FORMATION OF POLYOLS FROM PHENOLIC

COMPOUNDS IN BIO-OILS

Mé moire

ZHENG FANG

Sous la direction de :

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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.

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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.

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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

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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

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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

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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

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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.

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CHAPTER 1

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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

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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

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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]

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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

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CHAPTER 2

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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.

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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

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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]

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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

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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

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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]

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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

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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.

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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.

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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.

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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

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complicated to be thoroughly understood because of the complex compositions of biomass feedstock and the relatively wide range of reaction temperatures.

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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]

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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].

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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.

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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]

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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]

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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.

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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.

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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]

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CHAPTER 3

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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.

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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.

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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.

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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.

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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

1T

set 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)

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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.

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

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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.

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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.

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CHAPTER 4

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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

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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

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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

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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

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CHAPTER 5

WILLIAMSON ETHER SYNTHESIS

FROM PHENOLIC COMPOUNDS

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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

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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).

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( 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.

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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

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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)

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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).

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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.

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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.

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CHAPTER 6

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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

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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.

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Figure

Figure 1.1: Lignin primary precursors [2-4]
Figure 2.1: Possible reactions involved in the preparation of PU [18]
Figure 2.3: Concentration-time (c-t) curves of propylene oxide (PO) homopolymerization in  relation to KOH concentration
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]
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