A promising catalyst for hydrodesulfurization: Ni2P – A DFT study

Abstract

Abstract To test the hydrodesulfurization (HDS) performance of nickel phosphide (Ni2P), a periodic Ni2P model consisting of multiple sites was established. A density functional theory (DFT) accounting for dispersion corrections was used to calculate the structures, energy changes and energy barriers of hydrogen dissociation and key elementary step of 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS via direct hydrodesulfurization (DDS) route and hydrogenation (HYD) route. The results show the hydrogen dissociation on one hcp site and one Ni-P bridge site is exothermic and with a moderate activation energy, which means good reductivity of Ni2P surface. The adsorption of 4,6-DMDBT is strongly exothermic than Co(Ni)MoS, thanks to the extra interaction between the molecule and Ni2P surface. The process of C–S bond cleavage of 4,6-DMDBT through DDS route is also exothermic and activated efficiently when the activated hydrogen is in the appropriate position. While for HYD route, it’s a barrierless process with a tiny energy change when forming TH-4,6-DMDBT. Partial cycles of DDS and HYD were also calculated to understand the HDS mechanism. In addition, the HDS process over Ni2P has lots of advantages like adsorption strength, metal cations, accessibility of hydrogen, hydrogen transfer and sufficient sites for adsorption and reaction than that of Co(Ni)MoS. Hence, the Ni2P (001) surface is of great performance to catalyze HDS process, which makes Ni2P a promising next generation catalyst.