Hydrothermal liquefaction of lignocellulosic biomass feedstock to produce biofuels: Parametric study and products characterization

In this work, hydrothermal liquefaction (HTL) of corn stover, obtained from north Alberta farms, was performed at different temperatures of 250, 300, 350 and 375 degrees C, initial pressures (P-i) of 300 and 600 psi and retention time (t(r)) of 0, 15, 30 and 60 min. All experiments were performed in a 250 mL autoclave reactor with 5 g corn stover and 30 mL de-ionized water (corresponding feed to water ratio of 1:6) in inert N-2 condition. The highest yield of heavy oil (29.25 wt%) was obtained at 300 degrees C, final pressure (P-f) of 2200 psi and 0 min retention time. The highest yield of hydrochar (30.21 wt%) was obtained at 350 degrees C, P-f of 3150 psi and t(r) of 15 min. Based on elemental analysis and energy calculation, highest carbon content and higher heating value for heavy oil was 76.32 wt% and 35.13 MJ/kg at 375 degrees C, P-f of 600 psi and t(r) of 15 min; and for hydrochar it was 68.23 wt% and 24.7 MJ/kg at 350 degrees C, P-f of 3150 psi and t(r) of 15 min. The GC-MS results for heavy oil indicated that majority of the compounds were phenolic in nature. SEM and FTIR results confirmed the presence of oxygen containing function groups on hydrochar surface. The gas was mainly composed of CO2, CH4, C2H6, C2H4, C3H6, C4H8, C4H6, C5H12, C6H14, and C6H12.