Production of upgraded biocrude from hydrothermal liquefaction using clays as in situ catalysts

• Published in: Energy conversion and management Vol. 247; p. 114764
• Main Authors: Ma, Qiulin, Wang, Kui, Sudibyo, Hanifrahmawan, Tester, Jefferson W., Huang, Guangqun, Han, Lujia, Goldfarb, Jillian L.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-11-2021; Elsevier Science Ltd
• Subjects: Biocrude; Boiling points; Calorific value; Catalysts; Char formation; Chemical composition; Chromatography; Clay; Clay mineral; Clay minerals; Dolomite; Energy recovery; Heterogeneous catalyst; Hydrothermal liquefaction; Kaolinite; Liquefaction; Minerals; Montmorillonite; Water-soluble oil; HTL; SSC; Hydrothermal liquefaction; EL; WSB; DL; Heterogeneous catalyst; Energy recovery; WISB; CR; DCM; TGA; GC-MS; SC; Biocrude; EW; DW; DSC; Clay mineral; HHV; KSC; Water-soluble oil; EA; MSC
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2021.114764

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•Catalytic hydrothermal liquefaction using montmorillonite, dolomite, kaolin, and sand.•Clay catalyst enhanced water-soluble and insoluble bio-oil yield and energy recovery.•Dolomite suppressed char formation to greatest extent.•80% of water-soluble, 40% of water-insoluble bio-oil comprises distillates <300 °C.
Hydrothermal liquefaction (HTL) is a thermochemical process that converts biomass into biocrude. HTL suffers from low yields of water-insoluble biocrude with high oxygen contents and low heating values. Inexpensive clay minerals including montmorillonite, dolomite, kaolinite and sand were used to upgrade HTL biocrude as in situ acid-base catalysts. Batch tests were performed using starch with 5 wt% clay minerals at 300 °C for 1 h. Bio-oil was fractionated into water-soluble and water-insoluble parts to explore potential catalytic mechanisms by analyzing the fractional distribution, elemental composition and chemical composition. Higher carbon recoveries in the bio-oil fraction (approaching 60%) occurred with clay-catalyzed HTL. Energy recovery of both bio-oil fractions increased by approximately 22% for all clays. A base-catalyzed pathway inhibits char formation from catalytic HTL, with dolomite approaching a char yield as low as 3%. Chromatographic analysis of heavy and light oils from both fractions showed that dolomite and montmorillonite play a catalytic effect via base and acid pathways on upgrading biocrude. Clay-catalyzed HTL modified the boiling point distributions by producing more 100–300 °C middle temperature distillates. Overall, catalytic HTL with clay minerals enhanced the heating value and energy recovery of bio-oils.