Study On Synthesis, Characterization And Catalytic Properties Of New Catalytic Material--Tungsten Phosphide Catalysts

Unsupported tungsten phosphide (WP) was prepared from an aqueous solution of ammonium metatungate and ammonium phosphate by dissolution, evaporation, calcinations and temperature-progammer reduction at the heating rate of 1℃/min in hydrogen. Supported tungsten phosphide catalysts were prepared by mixing and co-impregnation method. They were characterized by X-ray diffraction (XRD), BET, NH3-TPD and TG/DTA. The catalytic activities of the catalysts were investigated through hydrodesulfurization of thiophene, dibenzothiophene, diesel oil and hydrodenitrogenation of pyridine, quinoline. The catalytic activity of supported WP catalyst was also tested in long time HDS reaction of thiophene. The conclusions are as below:(1) The unsupported tungsten phosphide catalyst was prepared from the WP precursor (WPO5.5·0.5H2O ) by temperature-progammer reduction at above 500℃ in flowing hydrogen and then passivated under room temperature.(2) Supported tungsten phosphide catalyst precursors synthesized by co-impregnation method were reduced in flow to the Al-O-W-P at 600～700℃because of a stronger interaction between the γ-Al2O3 supporter and active species, and lost weight all the time at 700～900℃, which was the losing oxygen process of Al-O-W-P. Supported tungsten phosphide catalyst precursors synthesized by mixing method reached at constant weight at 700℃ in H2 reduction and mostly transformed into WP.(3) The thiophene HDS activities of the supported WP catalysts synthesized by mixing and co-impregnation methods increased with the increasing of reaction temperature. Appropriate amount of Ni and Co promoters was favourable to the thiophene HDS activities of the supported WP catalysts.The supported WP catalyst showed a higher thiophene HDS activity than that of the sulfurized industrial catalyst at higher reaction temperature.(4) The pyridine HDN activities of WP and supported WP catalyst synthesized by co-impregnation method at first increased, then decreased with the increasing of reaction temperature. The pyridine HDN activities of the supported WP catalyst synthesized by mixing method decreased with the increasing of reaction temperature. The Ni promotor was not favourable to HDN activity of the supported WP catalyst. Suitable amount of Co promotor could increase the HDN activity of the supported WP catalyst.(5) The supported WP catalysts showed considerable activity in HDS reaction of dibenzothiophene and HDN reaction of quinoline. The ibenzothiophene HDS activity and quinoline HDN activity of the spported WP catalysts synthesized by co-impregnation method was better than that synthesized by mixing method. The HDS and HDN activities of 25～30% WP catalysts synthesized by co-impregnation method and reduced at 650～750℃ were better than those of the corresponding sulfurized catalyst.(6)The WP/γ-Al2O3 catalyst containing 5% Ni promotor showed a higher diesel oil HDS activity than that of the corresponding sulfurized catalyst and phosphide industrial catalyst and sulfurized industrial catalyst.(7) The thiophene HDS activities of the supported WP catalyst did not decrease obviously in the long time HDS reaction. The HDS activity of the supported WP catalyst was relatively stable.