Effect of transition metals on hydrothermal liquefaction (HTL) of agricultural residues = 전이 금속을 적용한 농업 부산물의 수열반응에 관한 연구

다국어 초록 (Multilingual Abstract)

Hydrothermal liquefaction (HTL) of two agricultural residues, empty fruit bunch (EFB) and coconut shell (CCNS) was performed with an autoclave reactor within a diverse temperature range (240–330 °C) in the presence of various transition metal chlorides (ZnCl2, CuCl2 and NiCl2) to investigate its effects on the properties of HTL products: HTL oil, hydrochar, and water soluble fraction (WSF). The highest yield of HTL oil from EFB was 24.2 wt% at 300 °C, which was higher than that from CCNS (14.0 wt%) at the same temperature. The yield of gas showed an inversely proportional correlation to the yield of HTL oil. At 240 °C the yield of hydrochar from EFB was higher than 50% due to the incomplete degradation of cellulose, and it steadily decreased with increases in temperature. Water content of HTL oil ranged from 2.0% to 5.6% for EFB, 3.3% to 9.6% for CCNS, respectively. Total acid number (TAN) value of oil for both biomasses increased with a rising temperature up to 300 ºC and then decreased at 330 ºC. Gas chromatography-mass spectrometry (GC/MS) analysis revealed that HTL oils from EFB and CCNS at 300 °C had the largest amounts of chemical compounds, such as furfural and cyclic ketones derived from holocellulose and phenol, guaiacol, and syringol derived from lignin. In the presence of transition metals, the yield of HTL oil decreased with an increased transition metal dose of up to 10.0%, while changes in the amount of gas, WSF, and hydrochar were different by according to the kind of feedstock or metals. Water content of HTL oil rose by the increasing amount of the metals, while the TAN value was varied and chemical compounds decreased. γ-Valerolactone (GVL) and levulinic acid were found, derived from acidic hydrothermal decomposition of cellulose. Unlike other metals, relatively small amounts of GVL and large amounts of levulinic acid were detected, especially in the presence of CuCl2. It is suggested that CuCl2 inactivates the conversion of levulinic acid to GVL under subcritical condition.

목차 (Table of Contents)

• 1. Introduction 1
• 1.1. Agricultural residue and its application 1
• 1.2. Thermochemical conversion process 3
• 1.3. Hydrothermal liquefaction (HTL) for oil production 5
• 1.4. Objectives 7
• 2. Literature review 9
• 2.1. HTL of biomass 9
• 2.1.1. Feedstock for HTL 9
• 2.1.1.1. Cellulose / lignin model compounds 9
• 2.1.1.2. Woody biomass 10
• 2.1.1.3. Non-woody biomass 11
• 2.1.1.4. Algal biomass 11
• 2.1.2. Process parameters 12
• 2.2. Catalysts for HTL of biomass 14
• 2.2.1. Alkaline catalysts 14
• 2.2.2. Acid catalysts 15
• 2.2.3. Metal catalysts 16
• 2.2.4. Other catalysts 16
• 3. Materials and methods 18
• 3.1. Materials 18
• 3.2. Performance process of HTL 22
• 3.3. Characterization of the HTL products 26
• 3.3.1. Physicochemical analysis of HTL products 26
• 3.3.2. GC/MS analysis of HTL oil 27
• 4. Results and discussion 28
• 4.1. Characterization of the samples 28
• 4.2. Effect of process parameters on the HTL 31
• 4.2.1. Effect of temperature 31
• 4.2.1.1. Mass balance 31
• 4.2.1.2. Physicochemical properties 35
• 4.2.1.3. GC/MS analysis 37
• 4.2.2. Effect of transition metal chlorides 44
• 4.2.1.1. Mass balance 44
• 4.2.1.2. Physicochemical properties 48
• 4.2.1.3. GC/MS analysis 50
• 5. Conclusion 61
• 6. References 63
• 초 록 71