Synthesis and Characterization of Ferromagnetic Nickel–Cobalt Silicide Catalysts with Good Sulfur Tolerance in Hydrodesulfurization of Dibenzothiophene

Abstract

Preparation of highly active and excellent sulfur tolerant hydrodesulfurization (HDS) catalysts is very important for the removal the sulfur from the sulfur containing compounds in petroleum. Herein we report on the synthesis and characterization of ferromagnetic nickel–cobalt silicide (Ni1–xCoxSi2) solid solution catalysts having large surface area by the reaction of nickel cobalt oxide solid solutions with SiH4. The catalytic properties of Ni1–xCoxSi2 were investigated for HDS of dibenzothiophene (DBT). The results showed that the saturation magnetization of the Ni1–xCoxSi2 solid solutions with fluorite structure can be controlled by changing the molar ratio of Ni to Co. The nickel-rich Ni0.75Co0.25Si2 catalyst is much more active than that of monometallic silicide (NiSi2 and CoSi2) and significantly improves the hydrogenation property (31.5% HYD selectivity), proving the synergistic effect between the components. X-ray photoelectron spectroscopy (XPS) provided further evidence that the valence electron concentration of the Ni increased with increasing the Co substitution, enhancing the metal–silicon and metal–metal interactions. In addition, the Si sites in the silicides alter the metal coordination, leading to a strong modification of the electronic structure around the Fermi level of the metals. This engenders a high activity for the HDS of DBT and weakens the metal–sulfur bonds, improving the sulfur tolerance.