Molybdenum nitride and carbide prepared from heteropolyacid - III. Hydrodesulfurization of benzothiophene

Abstract

Hydrodesulfurization (HDS) of benzothiophene has been studied over molybdenum nitride prepared from MoO3, 12-molybdophosphoric acid (HPA), and MoO3 + P2O5 (a physical mixture of P2O5 and MoO3 with stoichiometry of P to Mo equal to that of HPA). It was observed that Mo2N was an effective catalyst for HDS of benzothiophene. Ethylbenzene was the exclusive product over the whole temperature range investigated. Adding P2O5 to the precursor MoO3 had beneficial effects on HDS of benzothiophene. Most importantly, the presence of phosphorus in Mo2N dramatically improved its resistance against catalyst deactivation. The reaction pathway of HDS appeared not to be changed by adding phosphorus. Adsorption, XRD, EPMA, and XPS characterized the catalysts after HDS reaction. The bulk structure of face-centered-cubic Mo2N and its morphology were retained after HDS reaction. However the presence of phosphorus in the precursors resulted in growing polycrystallinity and amorphism in produced Mo2N. A great amount of sulfur compounds was found deposited on the surface of the catalysts after reaction, leading to catalyst deactivation. The presence of phosphorus in Mo2N reduced the amount of deposited sulfur compounds that appeared responsible for the improved resistance against the catalyst deactivation. (C) 1998 Academic Press.