Effect of NiMo phases on the hydrodesulfurization activities of dibenzothiophene

Preparation of highly-active hydrodesulfurization (HDS) catalysts draws increasing attention due to environmental concerns. Now the effects of various NiMo phases on the HDS activities are investigated. Calcinations of a series of PVP-assisted synthesized NiMo oxides led to NiMo precursors with various phases. The NiMo precursors and sulfided catalysts were characterized by XRD, N-2 isotherm, FT-IR, SEM, and TPR, and the activities of the NiMo catalysts were obtained in the HDS reactions of dibenzothiophene (DBT). Results revealed that the phases of alpha-, beta-NiMoO4, and ammonium nickel molybdate were detected on the NiMo precursors. A NiMo-0.5 precursor with a H-2-type hysteresis loop had very high BET surface area (144 m(2) g(-1)), which was higher than traditional metal oxides. Phases of MoS2 and Ni3S2 nanoparticles were detected on the sulfided NiMo catalysts. Catalytic results reveal that the sulfided NiMo catalysts deriving from beta-NiMoO4 phase were more active than those from the alpha-NiMoO4 phase. A NiMo-0.1 catalyst had higher HDS activities towards DBT than the other NiMo catalysts, due to the phase of beta-NiMoO4 and easy reductions of nickel oxide and molybdate, which might be beneficial for the formation of 'NiMoS' active phase. These findings show that for the preparations of highly-active unsupported and supported NiMo catalysts, the beta-NiMoO4 phase is preferred, which provides more useful information in the development of HDS catalysts. (C) 2016 Elsevier B.V. All rights reserved.