Ni2P/Al2O3 hydrodesulfurization catalysts prepared by separating the nickel compound and hypophosphite

Abstract

Bulk Ni2P and Al2O3-supported Ni2P were prepared at low phosphidation temperature (300 or 330°C) from nickel nitrate, oxide, sulfate, chloride, and acetate as nickel source and ammonium and sodium hypophosphite as well as hypophosphoric acid as phosphorus source. The hypophosphite source was positioned up-flow of the nickel source in an oven and flowing N2 gas transported the phosphine formed in the decomposition of hypophosphite to the nickel compound. X-ray diffraction, N2 adsorption-desorption, thermogravimetry and differential scanning calorimetry, temperature-programmed reduction in H2, and transmission electron microscopy, field emission scanning electron microscopy, CO chemisorption, and solid-state 31P nuclear magnetic resonance were used to study the bulk and supported Ni2P. Whereas unsupported nickel nitrate, sulfate, chloride, and oxide led to impure Ni2P, nickel acetate gave pure Ni2P. Ni2P/Al2O3 catalysts were therefore prepared from nickel acetate and their activity was studied in the hydrodesulfurization of dibenzothiophene. Separating the hypophosphite from the nickel compound has the advantage that the phosphate formed in the disproportionation of hypophosphite does not reach the Al2O3-supported Ni compound and cannot block the pores of the support. Ni2P is formed by sequential reduction and phosphidation reactions and therefore its preparation demands careful adjustment of the synthesis conditions. Insufficient PH3 leads to Ni and Ni12P5 side products and too much PH3 to Ni5P4, which all have a lower HDS activity than Ni2P.