Catalytic hydrothermal liquefaction of peanut shell for the production aromatic rich monomer compounds

Abstract Industrial wastes and natural mixed oxide materials were evaluated as inexpensive heterogeneous catalysts for catalytic hydrothermal liquefaction (HTL) of food wastes. Base MgO and ZSM-5 and mixture of MgO + ZSM-5 achieved bio-oil yields of 31.2, 35.5, and 40.6 wt% with higher heating values (HHVs) of 32.5–34.8 MJ kg-1, respectively, which were much greater than those without the catalyst. Bio-oil characterization revealed that similar families of molecules were formed in the presence and absence of catalysts, implying that the main role of the catalyst is to promote rates of thermal reactions, leading to Bio-oil production. The improved catalytic HTL performance of the mixed metal oxides compared with single-metal oxides was attributed to the synergistic effects of base and acid sites present on catalyst surfaces. Maximum yield of aromatic hydrocarbon compounds (49%) observed in case of HTL with MgO + ZSM-5 mixture catalyst. The percent of energy recovered as bio-oil was strongly correlated with the base-to-acid site density ratio, providing an important performance predictor for catalyst HTL conversion of food waste to bioenergy.