Preparation And Hydrodesulfurization Performance Of Phosphides/SBA-15 Catalysts

Transition metal phosphides have showed superior activities in hydrodesulfurization and hydrodenitrogenation as a new hydroprocessing catalyst.Using Al₂O₃ as support of phosphides catalysts have worse catalytic performance because of the reaction between precursor and carrier.The mesoporous molecular sieve SBA-15 has high surface area and high thermal stability.It may improve the surface area and the dispersion of catalysts using SBA-15 as support.So in this paper,phosphides/SBA-15 catalysts with different phosphides contents were prepared,and the characterization and catalytic performance of these catalysts were mainly investigated.SBA-15 was prepared by hydrothermal synthesis method using P123 as surfactant and TEOS as silicate material in the acidic condition.The precursors of phosphides/SBA-15 were prepared by impregnation method using SBA-15 as support,(NH₃)₂HPO₄ as phosphorus source and ammonium molybdate.Ammonium tungstate and nickel nitrate as metal source.Then,the MoP/SBA-15(10%～30%),WP/SBA-15(10%～30%)and Ni₂P/SBA-15 (5%～40%)catalysts with different phosphide content were prepared by temperature-programmed reduction method.The mesoporous structure of SBA-15 was still maintained after supporting MoP and WP,the active components were well dispersed,but the specific surface area,pore diameter,and total volume gradually decreased. The catalytic performance increases with increasing MoP and WP contents, and the catalysts have best catalytic performance when MoP and WP contents was 30%.The thiophene conversion of MoP/SBA-15 reached 95%and approached overall conversion of WP/SBA-15 catalysts.The catalytic performance was increased obviously by adding Ni contents.In Ni₂P/SBA-15 catalysts,the phase on SBA-15 was the mixture phase of Ni₂P and Ni₁₂P₅ when P/Ni=0.5,and there's only Ni₂P phase when P/Ni=0.8,1, The active components Ni₂P were well dispersed,but the specific surface area,pore diameter,and total volume gradually decreased with increasing Ni₂P contents.The catalysts with 25%Ni₂P contents has the best catalytic performance below 360℃,and the thiophene conversion of all the catalysts approach overall conversion when the temperature is higher than 360℃.The catalytic performance sequence of the phosphides/SBA-15 catalysts is: Ni₂P/SBA-15＞WP/SBA-15＞MoP/SBA-15 in the same condition.