Effect of thermochemically fractionation before hydrothermal liquefaction of herbaceous biomass on biocrude characteristics

Hydrothermal liquefaction (HTL) of fractionated two types herbaceous biomass (kenaf and miscanthus) by dilute acid, organosolv, alkaline, or demineralization process was carried out under ethanol water co-solvent at 350 degrees C for 30 min to examine the biocrude yield and characteristics. The biocrude properties were comprehensively characterized by HPLC, elemental, GC-MS, and TGA analysis. Fractionation technologies before HTL effectively increased biocrude yield up to 38% compared to that of untreated herbaceous biomass (31%), except for organosolv fractionation of miscanthus, especially, HTL after alkaline fractionation showed high yield and energy recovery ratio up to 70%. Elemental analysis showed that HHV of biocrude was negatively affected by hydrolysis reaction of high lignin content after dilute acid fractionation. The GC-MS analysis revealed that carbohydrates-derived compound significantly increased in the biocrude obtained after organosolv and alkaline fractionation due to holocellulose increases through fractionation process. Additionally, TGA results indicated that the ratio of high-boiling-point compounds in biocrude obtained after demineralization was expanded compared with untreated due to ash removal, which could act as a catalyst. (C) 2020 Elsevier Ltd. All rights reserved.