Effects of Process Parameters on Conversion of Rice Straw-Lignin into Bio-Oil by Hydrothermal Liquefaction

• Published in: Chemical engineering transactions Vol. 94
• Main Authors: Phu V. Vu, Tan M. Le, Viet T. Tran, Phung K. Le
• Format: Journal Article
• Language: English
• Published: AIDIC Servizi S.r.l 01.09.2022
• ISSN: 2283-9216
• DOI: 10.3303/CET2294137

Lignin derived from rice straw, an abundant renewable feedstock in nature, has the potential to be utilized as a substitute for fossil fuels in the production of value-added aromatic derivatives. However, depolymerization becomes one of the most difficult obstacles in the lignin-to-valuable products conversions due to the structural complexity and recalcitrance of lignin. In this work, rice straw-derived lignin was depolymerized to aromatics by using the hydrothermal liquefaction method in the ethanol-water solvent under hydrogen pressure. Effects of various process parameters on yields such as reaction time, ethanol concentration, reaction temperature, initial hydrogen pressure, and solvent-to-lignin ratio, were investigated. The suitable conditions for the highest yield of oil products (~ 75 %) were determined to be 65 vol. % ethanol, 250 °C, 60 min, 20 bar of hydrogen, and the solvent-to-lignin ratio of 35 mL/g. The obtained oil products were characterized by gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared (FT-IR). The bio-oil was mainly aromatics such as phenol, 3-ethylphenol, guaiacol and had a heating value of 22.2 MJ/kg. Hydrothermal liquefaction was demonstrated as an appropriate method for lignin depolymerization into aromatic compounds with high production yields.