Heterogeneous iron and ruthenium catalysts for carbohydrate based biomass transformations

다국어 초록 (Multilingual Abstract)

Heterogeneous catalyst applications have increased attention in green chemistry. Polymer, metal oxide, and carbon are used as universal support materials to fabricate heterogeneous catalysts. Because the heterogeneous catalyst is generally insoluble in solvent, it can be separated easily from the reaction media by filtration and recycled numerous times. Moreover, it is possible to design the property of catalysts through chemical processes. Despite these advantages, the use of heterogeneous catalysts has not been increased in biomass conversion to produce value-added chemicals because of lower activities than homogeneous catalysts. Thus, the development of highly efficient heterogeneous catalyst still remains a challenge in biomass transformation.
In this thesis, two types of heterogeneous transition metal catalysts were utilized for efficient carbohydrate transformations: iron catalyst for fructose dehydration and ruthenium catalyst for 5-hydroxymethyl furfural (HMF) hydrogenation/oxidation.
In chapter 1, fructose dehydration into HMF by heterogeneous NHC-Fe catalyst is described. Developing HMF production process has been the most important task in C6 biomass transformation. So far, numerous HMF production methods from carbohydrates have been reported using various catalysts such as Bronsted and Lewis acid, and ionic liquids. N-heterocyclic carboene (NHC)-Fe complex grafted heterogeneous catalysts were prepared from polystyrene and graphene oxide support. NHC ligand provided a stable and strong metal-ligand bonding environment to form an efficient active site. Polystyrene supported NHC-FeIII catalyst showed excellent fructose dehydration activity comparing to other supported NHC-metal catalysts. Graphene oxide grafted with NHC-FeIII catalyst showed better catalytic performance than polystyrene supported one. Futhermore, the NHC-FeIII grafted catalysts could be reused for 5 cycles without significant loss of activity.
In chapter 2, synthesis of HMF derivatives by heterogeneous ruthenium catalyst is described. HMF derivatives such as 2,5-furandicarboxylic acid (FDCA) and 2,5-bis(hydroxymethyl)furan (BHMF) have received a lot of attention because of their applicability. Zirconia was chosen as a suitable solid support with unique surface features, which can improve the catalytic ability of the metal active sites. Ruthenium active sites were immobilized on the surface of zirconia without forming Ru(0) metal or RuO2 nanoparticles (NPs). The well deposited Ru active site resulted in enhanced HMF hydrogenation and oxidation activity. The zirconia supported ruthenium catalyst showed excellent catalytic ability for oxidation of HMF into FDCA with molecular oxygen as a green oxidant. HMF was selectively reduced to BHMF with excellent yield under pressured hydrogen gas condition. Moreover, the zirconia supported ruthenium catalyst could be recycled over 10 times without significant loss of activity.

목차 (Table of Contents)

• TABLE OF CONTENTS
• ABSTRACT i
• TABLE OF CONTENTS iv
• LIST OF TABLES vii
• LIST OF FIGURES viii
• LIST OF SCHEME xii
• LIST OF ABBREVIATIONS xiv
• Introduction
• 1. Concept of Green Chemistry 1
• 2. Biomass and Bio-refinery 4
• 2.1 Biomass: Renewable Carbon Source 4
• 2.2 Bio-refinery 6
• 2.2.1 Strategies of Biomass Transformation Processes. 8
• 2.2.2 Biomass Based Platform Chemicals 10
• 2.3 Carbohydrate Biomass Conversion to Produce Platform Chemicals 12
• 2.3.1 Carbohydrate based Platform Chemicals 12
• 2.3.2 Synthesis of HMF from Carbohydrates 14
• 2.3.3 Synthesis of FDCA from HMF 17
• 2.3.4 Synthesis of BHMF from HMF 21
• 3. Catalysts 23
• 3.1 Heterogeneous Catalysts 23
• 3.2 Catalytic Dehydration Reaction 25
• 3.3 Catalytic Oxidation Reaction 26
• 3.4 Catalytic Reduction Reaction 31
• 3.5 Iron Catalyst in Organic Synthesis 33
• 3.6 Ruthenium Catalyst in Organic Synthesis 36
• 4. Research Objectives 38
• Chapter 1 Fructose Dehydration for Producing HMF
• 1. Experimental Section 39
• 1.1. Chemicals and Materials 39
• 1.2 Characterization 41
• 1.3. Preparation of N-Heterocyclic Carbene (NHC)─FeIII Catalyst 43
• 1.3.1 Immobilization of 1-Methyl Imidazole on Chloromethyl Polystyrene 43
• 1.3.2 Preparation of PS-NHC-FeIII Catalyst 44
• 1.3.3 Synthesis of NHC Ligand 45
• 1.3.4. Preparation of Graphene Oxide (GO) 47
• 1.3.5 Preparation of GO-NHC-FeIII 48
• 1.4. Fructose Dehydration Reaction Catalyzed by NHC-FeIII 49
• 1.4.1. General Experimental Procedure for Fructose Dehydration Reaction Catalyzed by PS-NHC-FeIII 49
• 1.4.2 General Experimental Procedure for Fructose Dehydration Reaction Catalyzed by GO-NHC-FeIII 50
• 1.4.3 Reusability Test of PS-NHC-FeIII Catalysts for Fructose Dehydration Reaction 51
• 1.4.4 Reusability Test of GO-NHC-FeIII Catalysts for Fructose Dehydration Reaction 52
• 1.5 Separation of HMF from DMSO 53
• 2. Result and Discussion 54
• 2.1. Characterization of PS-NHC-FeIII 54
• 2.2. Dehydration of Fructose to HMF Catalyzed by PS-NHC-Metal Catalysts 65
• 2.3. Characterization of GO-NHC-FeIII 71
• 2.4. Dehydration of fructose to HMF catalyzed by GO-NHC-FeIII catalysts 83
• 2.5. Separation of HMF from DMSO 89
• 3. Conclusion 91
• Chapter 2. Conversion of HMF to Value Added Chemicals
• 1. Experimental Section 92
• 1.1. Chemicals and Materials 92
• 1.2. Characterization 93
• 1.3. Oxidation of HMF into FDCA Catalyzed by Ru(OH)x/ZrO2 95
• 1.4. Reduction of HMF into BHMF Catalyzed by Ru(OH)x/ZrO2 96
• 2. Results and Discussion 97
• 2.1. Characterization of Ru(OH)x/ZrO2 Catalyst 97
• 2.2. Oxidation HMF into FDCA Catalyzed by Ru(OH)x/ZrO2 103
• 2.3. Reduction HMF into BHMF Catalyzed by Ru(OH)x/ZrO2 118
• 2.3.1. Reaction Optimization in Reduction HMF into BHMF 118
• 2.3.2. Hydrogenation of HMF into BHMF 123
• 3. Conclusion 129
• References 130
• Appendix 151
• Abstract in Korean 161