Molecular simulation on hydrodesulfurization of thiophenic compounds over MoS2 using ZINDO

In order to develop a fundamental understanding of the HDS mechanism of thi ophenic compounds over molybdenum disulfide (MoS2), a molecular simulation of the hydrodesulfurization (HDS) of thiophenic compounds over MoS2 has bee n performed using Zerner's Intermediate Neglect of Differential Overlap (ZI NDO) program. On the basis of the calculated edge structure, stoichiometry of MoS2, shape of the crystal, and the size corresponding to real MoS2 part icles, a single-slab cluster, Mo27S54, has been proposed for modeling the h ighly dispersed MoS2. The proposed cluster is a regular hexagon with ((1) o ver bar 010) and (30 (3) over bar 0) edge planes only. According to the cal culated electronic properties of the surface, the coordinately unsaturated Mo-IV in the (30 (3) over bar 0) plane is expected to be the active site fo r hydrogenation of thiophenic and aromatic compounds. The most stable adsor ption configuration of thiophene on the Mo-IV is a flat adsorption configur ation via the eta(5)-bound coordination, whereas the most stable adsorption configuration of tetrahydrothiophene (THT) on the Mo-IV is a tilted adsorp tion configuration via the S-bound coordination. HDS mechanism of thiophene through the hydrogenation pathway over the (30 (3) over bar 0) plane of Mo S2 is discussed according to quantum chemical insights in combination with experimental results from the literature. (C) 2000 Elsevier Science B.V. Al l rights reserved.