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Title Page
Contents
Abstract 9
CHAPTER ONE. GENERAL INTRODUCTION AND EXPERIMENTATION 12
1.1. Background 13
1.1.1. Biodiesel 13
1.1.2 Transesterification 14
1.1.3. Saponification 17
1.1.4. Esterification 18
1.1.5. Alkali catalyzed processes 18
1.1.6. Acid catalyzed process 21
1.1.7. Two-step processes 24
1.2. Waste oils as a feedstock for Biodiesel 24
1.3. General Experimentation 30
1.3.1. Materials 30
1.3.2. Catalyst preparation 31
1.3.3. Characterization 33
1.3.4. Experimental procedures 34
1.4. Product Analysis 37
1.4.1. GC analysis 37
1.4.2. GC/MS Analysis 40
1.4.3. Acid value measurement 40
1.5. References 42
CHAPTER TWO. Study on the Solid Acid Catalysts in Biodiesel Production from High Acid Value Oil 44
2.1. Introduction 45
2.2. Experimental 48
2.2.1. Materials 48
2.2.2. Catalyst preparation 48
2.2.3. Experimental procedure 50
2.3. Results and discussion 50
2.3.1. Activities of different acid catalysts 50
2.3.2. XRD and FT-IR 54
2.3.3. Reaction optimization 57
2.3.4. Influence of free fatty acids 66
2.3.5. Catalyst recycling 76
2.4. Conclusions 78
2.5. References 79
CHAPTER THREE. Transesterification of used vegetable oils with a Cs-doped heteropolyacid catalyst in supercritical methanol 83
3.1. Introduction 84
3.2. Experimental 91
3.2.1. Materials 91
3.2.2. Catalyst preparation 91
3.2.3. Tansesterification of used VO in supercritical methanol 92
3.2.4. Catalyst stability test in supercritical methanol 93
3.3. Results and discussion 95
3.3.1. Catalyst stability in supercritical methanol 95
3.3.2. Catalyst characterization 97
3.3.3. Reaction-kinetics and effects of reaction parameters 102
3.4. Conclusions 115
3.5. References 116
CHAPTER FOUR. Tungstophosphoric acid supported over mesoporous titania silica composite as a novel catalyst for esterification reaction 120
4.1. Introduction 121
4.2. Experimental 124
4.2.1. Materials 124
4.2.2. Catalyst preparation 124
4.2.3. Characterization 126
4.2.4. Esterification reaction 127
4.2.5. Catalyst stability test 128
4.3. Results and discussions 128
4.4. Conclusion 149
4.5. References 150
CHAPTER FIVE. Synthesis of sulfated mesoporous titania-silica catalysts and its application in biodiesel production from waste oil 154
5.1. Introduction 155
5.2. Experimental 160
5.2.1. Materials 160
5.2.2. Preparation of SO₄2-/TiO₂-SiO₂ catalysts(이미지참조) 160
5.2.3. Catalytic tests 162
5.2.4. Characterization 164
5.3. Results and discussion 166
5.4. Conclusion 187
5.5. Reference 189
General conclusions 193
초록보기 더보기
The production of biodiesel from low quality feedstocks, which are generally associated with high free fatty acid (FFA) contents, is a valuable alternative that would make the process more economical. The conventional alkali catalysts are not suitable while dealing with waste oils, FFAs and water contents can cause saponification leading to lower conversions and catalyst effectiveness. Hence, It is necessary to develop new and effective solid acid catalysts which are capable of catalyzing esterification and transesterification reactions simultaneously, important steps in biodiesel synthesis from waste oils, and have more tolerance against FFAs.
In this dissertation, the use of Cs-doped heteropoly tungstate (CsHPW) has been studied for the biodiesel production in chapter 1 and 2. CsHPW exhibited high catalytic activity as well as better leaching stability in comparison to other solid acid catalysts, such as 20%HPW/ZrO₂, 20%WO₃/ZrO₂, 20%HPW/γ-Al₂O₃, and 20%HPW/SiO2, when applied for the simultaneous esterification and transesterification of 10% oleic acid-soybean oil mixture. The catalyst was recoverable and reused without any significant activity loss. A maximum conversion of 90% was achieved at 200 ℃ and 10 h reaction time. To increase the reaction rates and to utilize highly insoluble feature of CsHPW, it was applied in the transesterification of used vegetable oil with supercritical methanol. The results showed that supercritical methanol compensated for the low reaction rate of solid acid catalytic transesterification, while the Cs-doped heteropoly acid catalyst mitigated the harsh operation conditions of the supercritical methanol process. The content of fatty acid methyl esters (FAME) reached 92% under the optimum reaction conditions of 260 ℃, 20 MPa, a molar ratio of methanol to oil of 40, and a reaction time of 40 min in the presence of 3% catalyst.
Titania-silica mixed metal oxide materials with a mesostructure were synthesized from relatively cheaper precursors i.e., titanium oxychloride and sodium silicate. The mesoporous titania-silica composite (TSC) was further used as a support material to synthesize novel solid acid catalysts for the biodiesel production.
A series of 12-tungstophosphoric acid (HPW) immobilized on mesoporous TSC, with different HPW loadings from 5wt% to 50wt%, were prepared by impregnation method. The synthesized materials were characterized by BET, N2 adsorption isotherms, XRD, FT-IR, UV-visible spectroscopy, and SEM analysis. The utilization of these materials in the esterification of oleic acid showed that the 20%HPW/TSC was an active and stable catalyst which could be recycled for three consecutive runs without any considerable activity loss. The higher activity of this compound can be attributed to the higher surface area and better dispersion of the active material on the support surface.
A sulfated titania-silica composite (S-TSC), with improved structural and catalytic properties, was synthesized through surface modification of mesoporous titania-silica composite using sulfuric acid. The synthesized materials were critically characterized with various characterization techniques. Further, the utilization of S-TSC for the esterification of oleic acid and transesterification of waste oil proved its effectiveness in the biodiesel synthesis.
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