Effectiveness of CoMo and NiMo catalysts on co-hydroprocessing of heavy atmospheric gas oil–waste cooking oil mixtures

Co-hydroprocessing of fossil fractions with lipids is an alternative pathway for integrating biomass in the transportation sector. This work involves the evaluation of two commercial hydrodesulfurization (HDS) catalysts in terms of their effectiveness and suitability for hydroconversion of heavy atmospheric gas oil (HAGO) and waste cooking oil (WCO) mixtures. As the most common catalysts for conventional gas oil hydroprocessing are CoMo and NiMo over Al2O3, this work focused on comparing a CoMo/Al2O3 and a NiMo/Al2O3 catalyst with respect to the resulting diesel selectivity and quality. Both catalysts were investigated for three feedstocks including pure HAGO, a low WCO content (10% v/v) HAGO/WCO and a higher WCO content (30% v/v) HAGO/WCO mixture under three different reactor temperatures (330 °C, 350 °C and 370 °C). All the experiments were performed at constant pressure 812 psig, liquid hourly space velocity (LHSV) 1 h−1 and H2/Oil ratio 505.9 nl/l. The results have shown that the catalyst HDS efficiency depends primarily upon the reaction temperature and HAGO to WCO ratio, but is quite different for both catalyst types. The HDS effectiveness of the NiMo catalyst is not affected by the addition of WCO, even in the lowest temperature (330 °C), while the one of the CoMo catalyst is strongly affected by WCO. The presence of WCO in the feedstock was proven favorable for both diesel yield and saturation, for both catalysts, but affected strongly the deactivation rate of the CoMo catalyst. Based on the experimental results obtained via this study, it was evident that NiMo type catalysts are more suitable for co-hydroprocessing of petroleum fractions with lipid containing feedstocks.