Catalytic hydrothermal liquefaction of municipal sludge for biocrude production over non-noble bimetallic catalyst in ethanol solvent

In this study, non-noble metal Ni, Cu, Co loading on activated carbon (AC) were applied to the hydrothermal liquefaction (HTL) process of municipal sludge with ethanol solvent to evaluate the effects on biocrude. Three AC-supported non-noble metal catalysts were prepared: Ni/AC, Ni-Co/AC and Ni-Cu/AC. Ni-Co/AC and Ni-Cu/AC catalysts increased the HHV of biocrudes, and significantly reduced the sulfur content in biocrudes from 4.3 wt% to 0.8 wt% and 0.7 wt% compared with non-catalytic HTL. Ethanol solvent significantly improved biocrude yields, and esters accounted for about 50% of the total biocrudes due to esterification reaction. The presence of Ni-Co/AC along with ethanol promoted the conversion of high boiling point compounds to low boiling point compounds.