Effect of preparation method on the structure of rare earth metal Y modified Ni₂P catalysts and its HDS performance

The yttrium (Y) modified unsupported Y_x-Ni₂P catalysts were prepared by one step method and stepwise method (x refers to mol ratio of Y to Ni), respectively.The catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption specific surface area measurements (BET), CO uptake and X-ray photoelectron spectroscopy (XPS).The effects of preparation methods on thehydrodesulfurization (HDS) property of the catalysts were investigated by using dibenzothiophene (DBT) as the model compound.The results show that the addition of Y can suppress the formation of Ni₅P₄ phase and thus promote the formation of active Ni₂P phase.The addition of Y can dramatically increase the surface area and pore volume, effectively improve the HDS activity of nickel phosphide catalyst.The Y_x-Ni₂P catalysts prepared by these two methods with Y/Ni mol ratio of 0.10 exhibited the highest HDS activity.As compared to the stepwise method, the one step method which obtained catalysts possessed a larger specific surface area with high pore volume, a lower surface P/Ni mol ratio, a larger CO uptake and more exposed active Ni sites as compared to stepwise method.As a result, it showed a higher HDS activity.At a temperature of 340℃, a pressure of 3.0 MPa, a H₂/oil volume ratio of 700 and a weight hourly space velocity (WHSV) of 1.5 h^-1, the conversion of DBT over Y_0.10-Ni₂P catalyst prepared by one step method reached 97.7%, which was an increase of 5.4% comparing with the Y_0.10-Ni₂P catalyst prepared by stepwise method (92.3%).