Density functional theory study of thiophene hydrodesulfurization on γ-Mo2N(100) surface

Abstract

The hydrodesulfurization (HDS) of thiophene on an γ-Mo2N(100) surface was investigated by density functional theory (DFT) and different configurations of thiophene on γ-Mo2N(100) surface were considered. After geometric optimization, it was confirmed that the η5-Mo2N configuration was the most stable adsorption model with an adsorption energy of -0.56 eV, where thiophene absorbed on 4-fold hcp vacant sites parallel to the surface with the S atom bonded to a Mo2 atom. The stable coadsorption of H atoms and thiophene on hcp sites showed that the hcp site is the active site for thiophene HDS on γ-Mo2N(100). A direct desulfurization reaction pathway in HDS of thiophene dominated the process on the γ-Mo2N(100) surface, which could be divided into the removal of the S atom and the hydrogenation saturation of C4 species. To identify the intermediate products and the most probable reaction mechanism of thiophene HDS, a transition state search was carried out. The results indicated that the reaction of the first H atom required an activation energy of 1.69 eV, which was the rate-determining step in the HDS of thiophene. The thiol group (―SH) and butadiene were preferentially formed after hydrogenation of thiophene, and ―SH detached from mercaptan was the intermediate of H2S. 2-Butene and butane were the products of the hydrogenation saturation of butadiene. H2S, 2-butene, and butane were easily desorbed from γ-Mo2N(100) to give the products because of weak adsorption