Hydrotreatment of FCC Gasoline Catalyzed by CoMo Bifunctional Catalysts: The Effects of Acidity on Catalytic Performance

The acidity of bifunctional catalysts is regarded as one of the most important factors for FCC gasoline hydrotreatment. To investigate the effects of acidity on catalytic performance, the CoMo/Al2O3 catalysts modified by MCM-41 and HZSM-5 were prepared by incipient wetness impregnation. The characterization results showed that adding molecular sieves changed the distribution of acid sites of catalysts and had a positive impact on forming longer MoS2 slabs with a slightly higher stacking number related to better hydrodesulfurization (HDS) performance. The results of catalytic performance indicated that 1-octene isomerization conversion increased from 4.13 to 33.97% with the increasing Brønsted acid site/Lewis acid site (BAS/Lewis acid sites (LAS)) ratio by presenting stronger BAS, resulting in the increasing selectivity of hydrodesulfurization/olefin hydrogenation (HDS/HYDO) from 0.89 to 5.41. However, when the BAS/LAS ratio surpassed 0.46 with the presence of weaker and stronger BAS, HDS efficiencies started decreasing. This understanding sheds light on designing hydrotreating catalysts to produce high-quality gasoline.