Preparation of highly active unsupported nickel–zinc–molybdenum catalysts for the hydrodesulfurization of dibenzothiophene

Abstract

Nickel–zinc–molybdenum oxide catalyst precursors with various Ni/Zn molar ratios were synthesized by chemical precipitation and unsupported nickel–zinc–molybdenum sulfide catalysts were obtained by sulfidation of the precursors. The oxide precursors and unsupported sulfide catalysts were characterized by XRD, N2 adsorption–desorption, AAS, FT-IR, TG–DSC–MS, SEM, TPR, CHSN analysis, HRTEM, and XPS. The unsupported nickel–zinc–molybdenum sulfide catalysts were tested in the hydrodesulfurization of dibenzothiophene (DBT). XRD revealed that the mesoporous nickel–zinc–molybdenum oxide precursors consisted of a phase of ammonium nickel (or zinc) molybdate. SEM showed that the Ni9.5Zn0.5Mo10 catalyst precursor contained smaller nanoparticles than the other nickel–zinc–molybdenum precursors. A reduction peak of Mo species (from Mo6+ to Mo4+) was detected on the ternary nickel–zinc–molybdenum catalyst precursors and highly crystalline phases of MoS2 and Ni3S2 nanoclusters were found on the nickel–zinc–molybdenum sulfide catalysts. XPS showed that the introduction of Zn enhanced the sulfidation of Mo species. The Ni9.5Zn0.5Mo10 catalyst showed a higher reaction rate of DBT than the other nickel–zinc–molybdenum catalysts due to the easier reduction of both oxide precursors and sulfide catalysts, and full sulfidation of Mo species, which might be attractive in industrial application.