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Abstract: The reaction mechanism of thiophene hydrodesulfurization (HDS) on a Mo3S9 model catalyst has been investigated at the GGA level of density functional theory. On the basis of the computed energetic data, 2,5-dihydrothiophene has been identified as the most important intermediate of HDS processes, and it is responsible for the direct formation of butadiene as the principal product. Neither the stepwise formation of cis-2-butene nor that of butane is competitive. However, butene (or butane) can be obtained from the hydrogenation of the formed butadiene. [Copyright &y& Elsevier]

Abstract: The entire catalytic hydrodesulfurization (HDS) cycle of benzothiophene over Mo3S9 cluster has been investigated at the level of density functional theory. It is found that the hydrogenation and hydrogenolysis route with dihydrobenzothiophene (DHBT) as intermediate is more favored than the hydrogenolysis and hydrogenation route with styrene as intermediate. The stepwise hydrogenolysis of SB–C9 (C(aryl)–S) bond in DHBT leading to the formation of 2-phenylethanethiol is more favored than that of SB–C2 (C(alkyl)–S) bond with 2-ethylthiophenol as intermediate. The computed activation free energy and rate constant of benzothiophene hydrogenation to DHBT agree well with the available experimental data. The difference in HDS reactivity between benzothiophene and thiophene has been discussed. [Copyright &y& Elsevier]

The catalytic performance of Cu/ZrO2 calcined at different temperatures was investigated with XRD and XPS. It was found that the activity of Cu/ZrO2 depends on the interaction between copper and zirconia, rather than on their crystal sizes. The XRD and XPS results illustrated that the reinforced interaction between copper and zirconia can hinder the increase of the copper crystal size in the reaction process. In addition, B3LYP/LACVP density functional calculation revealed electron transfer from copper to zirconia and weakening effect of surface hydroxyl on zirconia near copper center. [Copyright &y& Elsevier]