Quantum chemistry of adsorption and hydrogenation of DBT and carbazole on NiMoS using ZINDO/I method

Abstract

The purpose of this study was to develop a fundamental understanding of the adsorption and first-step hydrogenation mechanisms of sulfur and nitrogen compounds over molybdenum disulfide (MoS2). To do so, molecular simulation of the dibenzothiophene (DBT) and carbazole over NiMoS micro-crystal active surface was performed using Zerner's intermediate neglect of differential overlap (ZINDO) program with Hyperchem software. This study discusses the adsorbed structural parameters of DBT and carbazole molecules and proposes possible reaction pathways of hydrogenation on the NiMoS catalyst surface. The most stable configuration of adsorbed DBT is with the molecular plane perpendicular to the catalyst surface, while carbazole preferably adsorbed with the molecular plane parallel to the surface. Reaction enthalpies of DBT and carbazole adsorption processes on the catalyst surface were simulated based on the different configuration structures. The conformation heats and the activation energies of first-step hydrogenation of DBT and carbazole molecules over different configuration structures were also obtained by quantum chemistry simulation. The simulations on different catalyst surface structures indicated that the less vacant sites on the surface would result in the relatively low activation energies for DBT molecule. However, the hydrodenitrogenation (HDN) of carbazole increased with more vacant sites on the catalyst surface.