Transportation fuel production by catalytic co-pyrolysis of pinewood biomass and used engine oil over HZSM-5@MCM-41 catalysts

Abstract

In this study, the performance of HZSM-5@MCM-41 core–shell catalysts was evaluated for the co-pyrolysis of pinewood (as a biomass source) and used engine oil (as hydrogen-rich waste) to enhance bio-oil quality. The results indicated that the use of catalysts increased biogas yield while reducing bio-oil yield, attributed to the removal of oxygenated functional groups. The investigation demonstrated that the catalytic co-pyrolysis process’s effectiveness in improving bio-oil quality depended significantly on the ratio of micro- and mesoporous structures. Among the catalysts examined, HZ/MC-1.5 (CTAB/HZSM-5 = 1.5) exhibited superior performance in terms of crystallinity, acidity, and surface properties. The incorporation of MCM-41 shells on the HZSM-5 core reduced coke formation from 4.2 % in the HZSM-5 catalyst to 1.5 % in the HZ/MC-1.5 catalyst, thereby enhancing catalytic activity during the co-pyrolysis process. The HZ/MC-1.5 core–shell catalyst achieved the highest degree of deoxygenation (78.1 %) and produced biofuels with improved quality, characterized by the highest H/C_eff ratio (1.65), the highest HHV (42.56 MJ/kg), and the lowest O/C ratio (0.05). In the presence of the HZ/MC-1.5 catalyst, the highest yields of aromatic (30.12 %) and naphthenic (21.13 %) compounds were obtained. Furthermore, the catalyst improved the yield of gasoline-, kerosene-, and diesel-range hydrocarbons compared to HZSM-5, with minimal impact on the yield of heavy components (>C20). The biofuel produced via catalytic co-pyrolysis in this study exhibited significantly improved properties compared to commercial heavy fuel and was comparable to commercial diesel and gasoline fuels.