Conversion characteristics of sugars derived from Quercus mongolica to levulinic acid by two-step acid-catalyzed treatment
신갈나무 유래 당으로부터 2단계 산촉매 처리에 의한 레불린산으로의 전환 특성

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dc.description학위논문 (박사)-- 서울대학교 대학원 : 산림과학부(환경재료과학 전공), 2016. 2. 최인규.-
dc.description.abstractThe objective of the present study is to understand the conversion characteristics of C6 and C5 sugars during acid-catalyzed treatment. Based on this knowledge, this study also aimed to produce levulinic acid from lignocellulosic biomass (Quercus mongolica) via a two-step acid-catalyzed treatment, to utilize a by-product of this reaction for production of levulinic acid, and to evaluate the productivity of this process in comparison with conventional fermentable sugar production methods.
The conversion of C6 and C5 sugars (i.e., glucose, galactose, mannose, xylose, and arabinose) by acid-catalyzed treatment using sulfuric acid (SA) was markedly affected by the reaction conditions (reaction temperature: 100-230°C, acid concentration: 0-2%), but differences among C6 or C5 sugars proved insignificant. In the absence of an acid catalyst, C6 sugar decomposition initiated at 160°C and was preferentially converted into 5-HMF, furfural, and humin, but not levulinic acid and formic acid, were generated. However, in the presence of an acid catalyst, C6 sugar was efficiently converted into levulinic acid via a 5-HMF intermediate at a lower reaction temperature (120-130°C), and the highest yield of levulinic acid (29.3 g/100 g C6 sugar at 200°C, 2% SA) was obtained by single-step acid-catalyzed treatment. However, the levulinic acid yield was slightly reduced due to the generation of humin at temperatures over 210°C.
By contrast, C5 sugar was decomposed at 160°C and was almost immediately converted into furfural (28.1 g/100 g C5 sugar (230°C)) in the absence of SA. However, under acidic conditions, C5 sugars were efficiently converted into furfural at lower reaction temperatures (120°C)
dc.description.abstractthe furfural yield was highest at 180°C in 1% SA, 37.6 g/100 g C5 sugar. Moreover, C5 sugar generated a large amount of an unidentified precipitate (37.3 g/100 g C5 sugar at 230°C, 2% SA) due to the strong condensation reaction caused by furfural, which might lead to the increased condensation of other products.
Based on these results, Two-step acid-catalyzed treatment of Quercus mongolica under various reaction conditions was conducted for levulinic acid production. During the 1st step of acid-catalyzed treatment, most of the hemicellulosic C5 sugars (15.6 g/100 g biomass) were released into the liquid hydrolysate at 150°C in 1% SA
dc.description.abstracta solid fraction containing 53.5% of the C6 sugars remained. Subsequently, during the 2nd step of acid-catalyzed treatment of the solid fraction under the selected conditions (reaction temperature: 160-230°C-
dc.description.abstractacid concentration: 1% or 2%), a higher levulinic acid yield (16.5 g/100 g biomass) was obtained at 200°C in 2% SA than in the single-step treatment.
Resultant liquid hydrolysate obtained from 1st step acid-catalyzed treatment of Quercus mongolica at 150°C in 1% SA was additionally treated by a zeolite as a catalyst. The zeolite was alkaline treated with different NaOH concentration for using C5 sugars as levulinic acid source, and then it could possess sizeable pores and relatively higher portions of strong acid sites. Considering effects of other treatment factors, reaction temperature (150-210°C) and time (30-300 min), 3.5 g/100 g biomass of levulinic acid was produced through zeolite-catalyzed treatment at 190°C, 180 min, and zeolite treated by 0.25 M NaOH.
In total, 20.0 g of levulinic acid could be produced from 100 g of Quercus mongolica via a multi-step treatment process in terms of biorefinery concept in this study. However, 31.5 g/100 g biomass of fermentable sugar (glucose) was produced from same solid fraction using a conventional process including enzymatic hydrolysis. Therefore, the proposed two-step acid-catalyzed treatment process is attractive due to the price competiveness of levulinic acid and the increased by-product utilization rate.
In conclusion, the conversion characteristics of lignocellulosic biomass to levulinic acid under acid-catalyzed conditions were investigated. Based on this, levulinic acid was produced from lignocellulosic biomass via the two-step acid-catalyzed treatment process. Then, levulinic acid production via by-product application was performed in a biorefinery concept. Therefore, the levulinic acid yield was maximized using the total process, which used a novel lignocellulosic biomass biorefinery process to effectively produce levulinic acid.
dc.description.tableofcontentsChapter 1. Introduction 1
1. Background 2
1.1. Renewable resources 2
1.2. Lignocellulosic biomass 4
1.3. Pretreatment of lignocellulosic biomass 7
1.4. The concept of biorefinery 8
1.5. Levulinic acid as a biorefinery product 10
2. Objectives 14
3. Literature review 16
3.1. Pretreatment process of lignocellulosic biomass 16
3.1.1. Physical pretreatment 16
3.1.2. Chemical pretreatment 17
3.1.3. Physicochemical pretreatment 19
3.1.4. Biological pretreatment 20
3.2. Multi-step pretreatment process 21
3.3. Conversion of sugar in lignocellulosic biomass 22
3.3.1. Conversion of C5 sugar under acidic condition 22
3.3.2. Conversion of C6 sugar under acidic condition 24
3.4. Production of levulinic acid 26

Chapter 2. Conversion characteristics of C6 and C5 sugars during acid-catalyzed treatment 29
1. Introduction 30
2. Materials and methods 32
2.1. Materials 32
2.2. Acid-catalyzed treatment process 32
2.2.1. Combined severity factor 34
2.3. Analysis of solid fractions 36
2.3.1. Water-insoluble solid recovery rate 36
2.4. Analysis of liquid hydrolysates 36
2.4.1. Sugar analysis 36
2.4.2. Sugar degradation product analysis 37
2.5. Statistical analysis 37
3. Results and discussion 39
3.1. C6 sugar conversion during acid-catalyzed treatment 39
3.1.1. C6 sugars 39
3.1.2. C6 sugar degradation products 43
3.1.3. Mass balance 54
3.2. C5 sugar conversion during acid-catalyzed treatment 58
3.2.1. C5 sugars 58
3.2.2. C5 sugar degradation products 61
3.2.3. Mass balance 67
4. Conclusions 71

Chapter 3. Levulinic acid production via two-step acid-catalyzed treatment of Quercus mongolica 73
1. Introduction 74
2. Materials and methods 76
2.1. Materials 76
2.2. Chemical composition analysis 76
2.2.1. Determination of extractives 76
2.2.2. Determination of lignin and structural sugars 77
2.2.3. Determination of ash 78
2.2.4. Elemental analysis 78
2.3. 1st step acid-catalyzed treatment 80
2.3.1. Combined severity factor 80
2.4. 2nd step acid-catalyzed treatment 81
2.5. Analysis of solid fractions 83
2.5.1. Water-insoluble solid recovery rate 83
2.5.2. Chemical composition and elemental analysis 83
2.5.3. FT-IR analysis 83
2.5.4. Pyrolysis-GC/MS analysis 83
2.5.5. BET surface area and pore volume analysis 84
2.6. Analysis of liquid hydrolysate 85
2.6.1. Sugar (monosaccharide) analysis 85
2.6.2. Sugar (oligosaccharide) analysis 85
2.6.3. Analysis of levulinic acid and other sugar degradation products 85
2.6.4. GC/MS analysis 86
2.7. Statistical analysis 86 
3. Results and discussion 87
3.1. Conversion characteristics of Quercus mongolica by 1st step acid-catalyzed treatment 87
3.1.1. Physicochemical characteristics of sold fractions 87
3.1.2. Chemical compositions of liquid hydrolysates 108
3.2. Levulinic acid production via 2nd step acid-catalyzed treatment 119
3.2.1. Levulinic acid yield 119
3.2.2. Mass balance 124
4. Conclusions 126

Chapter 4. Levulinic acid production via zeolite-catalyzed treatment using a liquid hydrolysate 127
1. Introduction 128
2. Materials and methods 130
2.1. Materials 130
2.2. Catalyst preparation 130
2.3. Zeolite-catalyzed treatment 132
2.4. Catalyst characterization 134
2.4.1. Acidic properties of zeolites 134
2.4.2. FT-IR analysis 134
2.4.3. BET surface area and pore volume analysis 134
2.5. Analysis of the liquid hydrolysate 135
2.5.1. Sugar analysis 135
2.5.2. Analysis of levulinic acid and other sugar degradation products 135
2.6. Statistical analysis 135
3. Results and discussion 136
3.1. Physicochemical properties of catalysts 136
3.1.1. Acidic properties of zeolites 136
3.1.2. Physical properties of zeolites 139
3.2. Conversion characteristics of liquid hydrolysate via zeolite-catalyzed treatment 143
3.2.1. Levulinic acid yield as a function of treatment factors 143
3.2.2. Mass balance 150
4. Conclusions 152

Chapter 5. Feasibility study of levulinic acid and fermentable sugar production for application to biorefinery process 153
1. Introduction 154
2. Materials and methods 156
2.1. Materials 156
2.2. Acid-catalyzed pretreatment 156
2.3. Enzymatic hydrolysis 158
2.4. Analysis of solid fractions 158
2.4.1. Water-insoluble solid recovery rate 158
2.4.2. Chemical composition analysis 158
2.5. Analysis of liquid hydrolysate 159
2.5.1. Sugar analysis 159
2.5.2. Sugar degradation product analysis 159
2.6. Statistical analysis 159
3. Results and discussion 160
3.1. Effects of pretreatment factors on fermentable sugar production 160
3.2. Fermentable sugar yield 164
3.2.1. Conversion rate of fermentable sugar 164
3.2.2. Mass balance 167
4. Conclusions 169

Chapter 6. Concluding remarks 170

References 175

초록 204
dc.format.extent5089453 bytes-
dc.publisher서울대학교 대학원-
dc.subjectlevulinic acid-
dc.subjecttwo-step acid-catalyzed treatment-
dc.subjectlignocellulosic biomass-
dc.subjectQuercus mongolica-
dc.titleConversion characteristics of sugars derived from Quercus mongolica to levulinic acid by two-step acid-catalyzed treatment-
dc.title.alternative신갈나무 유래 당으로부터 2단계 산촉매 처리에 의한 레불린산으로의 전환 특성-
dc.contributor.affiliation농업생명과학대학 산림과학부-
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College of Agriculture and Life Sciences (농업생명과학대학)Dept. of Forest Sciences (산림과학부)Theses (Ph.D. / Sc.D._산림과학부)
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