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Unsupported NiMoW sufides; Thermal decomposition; Hydrodesulfurization; Dibenzothiophene; Thiosalts
Abstract:
A family of unsupported NiMoW sulfide catalysts have been prepared by thermal decomposition of
mechanically ground tetramethylammonium thiomolybdotungstate and Ni(NO3)2 for hydrodesulfurization
of dibenzothiophene. The materials were characterized by Fourier transformation infrared spectroscopy,
ultraviolet–visible spectroscopy, thermogravimetric analysis, X-ray diffraction, N2 physorption,
scanning electron microscopy, and transmission electron microscopy. The results showed that structures
and properties of unsupported NiMoW sulfides depend on nickel content and decomposition condition.
XRD revealed a decrease in the stacking along the c direction of the MoS2 and/or WS2 crystalline structures
as the nickel content was increased, consistent with a higher dispersion of the metal sulfides observed
by electron microscopy. The low nickel content in Ni0.5MoWSy catalyst gave a positive effect on the
hydrodesulfurization of dibenzothiophene, as indicated by the greatly increased specific catalytic activity
per unit surface area. In contrast, the high nickel content in Ni1.5MoWSy catalyst showed a negative
effect due to the formation of nickel sulfides. Ni0.5MoWSy catalyst showed the highest activity in the
hydrodesulfurization reaction compared to other samples. The results further suggest that unsupported
NiMoW sulfide catalysts may be promising candidates for wide application in hydrotreating of fuel oil.
