HYDRODESULFURIZATION OVER PDMO HY ZEOLITE CATALYSTS/

A series of palladium-promoted Mo catalysts was prepared by two-step i mpregnation procedure using an ultrastable HY zeolite carrier. The mut ual effect of Pd and Mo phases and zeolitic support was investigated i n hydrodesulfurization (HDS) of dibenzothiophene (DBT) and diesel oil (1.1 wt% S). Pd/HY was more active than its binary PdMo/HY counterpart s, suggesting an inhibitory effect of Mo on Pd. The incorporation of P d probably prevented deactivation of PdMo catalysts in HDS of DBT. The initial sulfur conversion in HDS of gas oil over Pd/HY was similar to that on a commercial CoMo/Al2O3 catalyst; however, both Pd/HY catalys t and the blank HY zeolite deactivated very fast at short times on-str eam. On the basis of catalyst characterization by X-ray photoelectron spectroscopy, Fourier transform i.r. spectroscopy of adsorbed CO and p yridine, and temperature-programmed reduction, it is concluded that fo rmation of HxMoS2 and S[PdH+] hydride-like species in PdMo zeolites ar e probably responsible for the inhibitory effect on HDS activity. Copy right (C) 1996 Elsevier Science Ltd.