Study On Ni₂P Catalysts Supported On TiO₂-Pillared Sepiolite For Thiophene Hydrodesulfurization

With the petroleum becomes heavy, inferior degree deepen and the environmental laws become more and more strict, the sulfur content was strictly limited in the world, there puts forward the concept of deep hydrodesulfurization in both academia and industry. Deep hydrodesulfurization of oil is one of the most effective means to product clean fuel. Therefore, it is very urgent to develop more high-performance hydrodesulfurization catalyst.Transition-metal phosphides have been claimed to be promising new high-activity catalysts for HDS and HDN reactions and have very good resistance to coke deposition and poisoning. Ni2P has been reported as the most active phase among transition-metal phosphides for both HDN and HDS reactions. In this paper, a series of Ni2P catalysts with different supports were prepared by temperature-programmed reduction. Thiophene hydrodesulfurization was chosen as probe reaction to investigate activity of the catalysts. The catalysts were characterized by X-ray diffraction, BET, thermogravimetry(TG), transmission electron microscope and temperature-programmed reduction.In the first part, TiO2-pillared sepiolite was prepared by ion exchange method. The results demonstrated that the specific surface and pore volume of Ti-Sep were enlarged and catalyst thermal stability was improved; the surface acidity was enhanced and surface acid content was increased.In the second part, Ni2P/Ti-Sep catalysts were prepared by temperature-programmed reduction using nickel hydroxide as a nickel source and phosphorous acid as a phosphorus source (Ni/P=1/2), and the catalysts were applied to HDS of thiophene. Consequently, thiophene conversion on Ni2P/Ti-Sep is improved compared with Ni2P/Na-Sep and Ni2P/Ti-Sep, which were prepared on sepiolite without Ti-pillared. Ni2P shows better activity than Ni12P5. Ni2P/Ti-Sep with a Ni loading of15%(w) shows the highest activity among all of the studied catalysts, on which thiophene conversion of can reach100%at400℃. The method supposes an energy saving as there is no need of calcination and a lower reduction temperature is required.In the third part, Ni2P/Ti-Sep catalysts were prepared by temperature-programmed reduction using nickel nitrate as a nickel source and (NH4)2HPO4as a phosphorus source, and the catalysts were applied to HDS of thiophene. The optimum condition of Ni2P preparation was drawn as follows:Ni/P initial molar ratio1/1.25, the final reduction temperature of catalysts600℃, heating rate3℃/min, the optimum Ni load15w%. Thiophene conversion on Ni2P/Ti-Sep is improved compared with Ni2P/Al2O3.