PVP-assisted synthesis of unsupported NiMo catalysts with enhanced hydrodesulfurization activity

•Polyvinyl pyrrolidone (PVP)-assisted synthesis of NiMo catalyst precursor•A NiMo-0.5 precursor showed a uniform size of 20 nm.•Simultaneous reduction of Ni- and Mo-containing species was detected.•The NiMo-0.5 catalyst showed an enhanced HDS activity towards DBT.

The effect of polyvinyl pyrrolidone (PVP) on the physicochemical properties and catalytic activities of unsupported NiMo catalysts was studied. The NiMo catalyst precursors were synthesized by a PVP-assisted chemical precipitation method, by adding various contents of PVP to a Ni- and Mo-containing solution. A series of techniques, including CHSN analysis, XRF, XRD, N2 adsorption-desorption, FT-IR, SEM, TG-DSC, TPR, and XPS, were used to characterize the NiMo oxide precursors and sulfided catalysts, and the catalytic activities were tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The characterization results revealed that PVP was efficiently removed due to low contents in the synthesis and high solubility in water. The pore properties and hysteresis loop, the agglomeration of the nanoparticles, and the reducibility of the NiMo precursor were affected by the introduction of PVP, while the phases of the precursors and the thermal stabilities were little changed. Ni3S2 and MoS2 phases were observed in the sulfided catalysts. The catalysis results revealed that the hydrogenation pathway was predominant in the HDS of DBT. A NiMo catalyst synthesized with 0.5 g PVP showed a higher conversion of DBT than the other NiMo catalysts, possibly due to efficient formation of the 'NiMoS' active phase. This facile, scalable, and cost-effective route to prepare unsupported NiMo catalyst with enhanced HDS activities would be attractive in industrial applications.

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