Dual character of H2S as promoter and inhibitor for hydrodesulfurization of dibenzothiophene

Hydrodesulfurization (HDS) of dibenzothiophene (DBT) over laboratory synthesized bulk MoS2 catalysts using batch microautoclave reactor was studied. Influence of H2S (wide range level) on the DBT HDS activity and selectivity was investigated. In general, H2S was found to inhibit the direct desulfurization route that leads to biphenyl regardless the catalyst applied. However, the hydrogenation pathway which mainly produces phenylcyclohexane inferred to be either uninhibited or even more interestingly highly promoted by the presence of H2S depending on the catalyst nature. The ultimate sum impact of H2S on the catalytic activity shows two extremes, inhibition and promotion. Mechanism of H,S effect is proposed. (C) 2003 Elsevier Science B.V. All rights reserved.