Hydroconversion of Waste Cooking Oil into Green Biofuel over Hierarchical USY-Supported NiMo Catalyst: A Comparative Study of Desilication and Dealumination

The hydroconversion of waste cooking oil into hydrocarbon fuel was investigated over the hierarchical USY zeolite-supported NiMo catalysts which were prepared by dealumination ((NH4)2SiF6)/desilication (NaOH). The physical and acidity properties of the hierarchical catalysts were characterized by X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) infrared spectroscopy of adsorbed pyridine (Py-IR), ammonia temperature-programmed desorption (NH3-TPD), and H2 temperature-programmed reduction (H2-TPR). The Brønsted/Lewis (B/L) acid distribution was little affected by dealumination and the acid density decreased significantly. However, the highly-desilicated catalysts decreased the B/L ratio obviously. Therefore, many more Mo species in the NiMoO4 and MoO3 phases were produced in the AHFS-treated catalysts, while more high-valence-state Mo species in the NiMoO4 phase were formed in the NaOH-treated catalysts. The AHFS-treated catalysts showed higher catalytic activity and better DCO2 selectivity and selective cracking for jet fuel. The 42.3% selectivity of jet fuel and 13.5% selectivity of jet-range aromatics was achieved over the 8 wt % (NH4)2SiF6-treated catalyst with 67% DCO2 selectivity.