Preparation Of Supported Nickel Phosphide Catalyst And Its Hydrodesulfurization Performance

A simple and energy-efficient method for preparing a highly active nickel phosphide hydrodesulfurization?HDS? catalyst was proposed based on low temperature programmed reduction, in which the original nickel phosphide catalyst was modified under a flow of air instead of being passivated with an O₂/N₂ mixture. In this way, no pre-treatment at 500 oC for 2 h of the catalyst prior to reaction was needed. Ni₂P-O?x?/MCM-41?x is the different air modification temperature? catalysts with an initial Ni/P molar ratio of 1/2 and Ni loading of 10 wt.% were prepared by impregnating NiCl₂ and NH₄H₂PO₂ with the mesoporous MCM-41. The prepared catalysts were characterized by XRD, H₂-TPR, BET, CO uptake, XPS, PY-FTIR, SEM and TEM. The effects of the modification temperature, preparation methods and specific surface area on catalytic performance in HDS of dibenzothiophene?DBT? were investigated.The catalysts, which modified by air at different temperatures, showed a pure active Ni₂P phase. The sizes of Ni₂P particles were decreased by modification with air. The Lewis acidity was enhanced and the enrichment of phosphorus was suppressed by modification treatment. Compared with the Ni₂P-N/MCM-41 catalyst?the size of Ni₂P phase is 18 nm and CO uptake is 35 ?mol·g-1? prepared by O₂/N₂ passivation. The size of particles from Ni₂P-O?100?/MCM-41 catalyst decrease 4 nm, reached the smallest size of 14 nm, and the CO uptake increase 7 ?mol·g-1, reached the most adsorption quantity of 42 ?mol·g-1 respectively at 100 oC modification. The catalysts modified by different temperatures activity levels decrease as follows: Ni₂P-O?100?/MCM-41 > Ni₂P-O?50?/MCM-41 >Ni₂P-O?150?/MCM-41>Ni₂P-N/MCM-41. At a reaction temperature of 340 oC, a pressure of 3.0 MPa, a H₂/oil ratio of 500?V/V? and weight hourly space velocity of 6.0 h-1, the conversion of Ni₂P-O?100?/MCM-41 for DBT HDS was 95.4%, which increased by 6.9% compared to that of Ni₂P-N/MCM-41?88.5%? passivated with an O₂/N₂. Catalyst with air surface modification showed higher HDS activity may be due to the decrease of active phase size and the increase of Lewis acidity. Compared with high temperature programmed reduction method, the ratio of P/Ni was smaller, the enrichment of phosphorus was suppressed which expose more Ni active sites and performance in HDS was improved by the catalyst prepared with low temperature programmed reduction method. With a higher specific surface area of support, is advantageous to the distribution of active phase, which indicate the ratio of P/Ni was smaller and the mount of Ni active sites were more. The catalysts with different specific surface area activity levels decrease as follows: Ni₂P-O/MCM-41?H?>Ni₂P-N/MCM-41?H?>Ni₂P-O/MCM-41?L?>Ni₂P-N/MCM-41?L?.