Catalytic hydrothermal liquefaction of lignin for production of aromatic hydrocarbon over metal supported mesoporous catalyst

Catalytic hydrothermal liquefaction (HTL) of lignin was examined at various temperature (250–310 °C) and reaction time in the presence of different solvents (water, methanol and ethanol) with different metal supported on MCM-41 mesoporous catalyst. In case of ethanol solvent, the maximum bio-oil yield of 56.2 wt% was obtained with Ni-Al/MCM-41. However in case of water, bio-oil yield was (44.3 wt%); while significantly improves bio-oil yield for methanol solvent (48.1 wt%). It is indicated that alcoholic solvents promoted the lignin decomposition, while in the presence of catalyst; water solvent significantly improves lignin degradation. Loading of Ni and Al on MCM-41, the acid strength of the catalyst increased, which enhanced lignin degradation. From the GC–MS analysis, the main G-type (ca.54%) phenolic compounds were produced with higher percentage of aromatic hydrocarbon compounds. CHNS and GPC analysis showed that catalytic liquefaction encouraged hydrodeoxygenation, which produced lower oxygen content bio-oil with lower molecular weight.