Thiophene hydrodesulfurization over supported nickel phosphide catalysts

Abstract Silica-supported nickel phosphide (Ni 2 P/SiO 2 ) catalysts have been prepared and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), elemental analysis, X-ray photoelectron spectroscopy (XPS), and O 2 chemisorption measurements. Ni 2 P/SiO 2 catalysts were synthesized from oxidic precursors by reduction in either flowing H 2 or a H 2 S/H 2 mixture. XRD and TEM analysis of a 25 wt% Ni 2 P/SiO 2 catalyst confirmed the presence of Ni 2 P crystallites dispersed on the surface of the silica support. XPS analysis of a passivated 30 wt% Ni 2 P/SiO 2 catalyst indicated the presence of two kinds of Ni species, as well as phosphide and phosphate species at the catalyst surface. Thiophene hydrodesulfurization (HDS) activities were measured for Ni 2 P/SiO 2 catalysts with a wide range of Ni 2 P loadings (5–35 wt%) and after different pretreatments. A 30 wt% Ni 2 P/SiO 2 catalyst, when pretreated only by degassing in flowing He, was nearly 15 and 3.5 times more active than sulfided Mo/SiO 2 and NiMo/SiO 2 catalysts, respectively, after 100 h on-stream. The HDS activities of the Ni 2 P/SiO 2 catalysts correlated well with their O 2 chemisorption capacities, allowing calculation of a turnover frequency of 0.017±0.002 s −1 . Based on XRD measurements of tested catalysts as well as catalysts subjected to H 2 S/H 2 treatments at increasing temperatures, silica-supported Ni 2 P shows excellent stability under HDS conditions.