Effects of H2S on hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene on alumina-supported NiMo and NiW catalysts Original Research Article

Effects of the H2S partial pressure on the catalytic activity and product selectivity of the hydrodesulfurization (HDS) reactions of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were investigated over the sulfided NiMo/Al2O3 and NiW/Al2O3 catalysts under the deep desulfurization conditions (sulfur concentrations <0.05 wt.%). The inhibiting effects of H2S were observed in the HDS reactions of both DBT and 4,6-DMDBT. The HDS reaction of DBT was more strongly inhibited by H2S than that of 4,6-DMDBT over each catalyst. The formations of both biphenyls (BPs) and cyclohexylbenzenes (CHBs) were inhibited by H2S, but the former were inhibited more strongly. The NiMo/Al2O3 catalyst was less susceptible to the inhibiting effect of H2S than the NiW/Al2O3 catalyst. The promotion of Ni on NiMo catalyst reduced the inhibiting effect of H2S on the HDS activity. The HDS reactions were expressed by the Langmuir–Hinshelwood rate equation to examine the mechanisms of the inhibiting effects of H2S over the various catalysts. Over each catalyst, the heats of adsorption increased in the order DBT<4,6-DMDBT