Catalytic hydrothermal liquefaction of alkali lignin over activated bio-char supported bimetallic catalyst

Carbon-based support catalysts are beneficial on account of low material cost, prominent surface area, and stability at high temperature. In this study, biochar derived activated carbon (AC) supported metal catalysts were tested for hydrothermal liquefaction (HTL) of alkali lignin. Catalytic HTL of alkali lignin was carried out at various temperatures (260 to 300 degrees C) with varying catalysts quantity (5 to 20 wt%), and solvents (water, ethanol, methanol) for 15 min reaction time. As the reaction temperature increased from 260 to 300 degrees C, conversion increased from 76.2 to 85.5 wt%. Bimetallic catalyst Ni-Co/AC with ethanol solvent system at 280 degrees C gave highest bio-oil yield (72.0 wt%). Lignin catalytic depolymerization produces monomer phenolic compounds due to efficient breaking of the lignin macromolecule. Thus, the presence of catalyst and solvent increased the cleavage of beta-O-4 bonds resulting in increased selectivity towards vanillin (32.3-36.2%).

Automated summary

Carbon-based support catalysts play a crucial role in optimizing the hydrothermal liquefaction of alkali lignin, leading to increased bio-oil yield through efficient depolymerization. The use of ethanol solvent system, higher reaction temperatures, and increased catalyst quantities results in enhanced conversion and selectivity towards vanillin.