A novel synthesis of Ni2P/MCM-41 catalysts by reducing a precursor of ammonium hypophosphite and nickel chloride at low temperature

Abstract

A novel method to prepare Ni2P/MCM-41 catalysts at low reduction temperature based on ammonium hypophosphite and nickel chloride by temperature programmed reduction is described. The catalysts were prepared using incipient wetness impregnation of the siliceous MCM-41 support with aqueous solutions of ammonium hypophosphite and nickel chloride, followed by reducing the obtained precursor at 483–663K for 2h in flowing H2, to form Ni2P catalysts. The catalysts were characterized by H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), N2-adsorption specific surface area measurements (BET), CO uptake, transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). With sample of initial P/Ni molar ratio >0.5, the Ni2P was successfully obtained at lower reduction temperature, and a high initial P/Ni molar ratio favors the formation of Ni2P at lower temperature. Using less oxidic phosphorus precursor of hypophosphite enabled the Ni2P to be formed at low reduction temperature. Evaluation of the activity for DBT HDS of the catalysts shows that the catalyst prepared with initial P/Ni ratios of 2 exhibited the highest activity. At a reaction temperature of 613K, a pressure of 3.0MPa, a H2/oil ratio of 500 (V/V), and a weight hourly space velocity (WHSV) of 2.0h−1, the HDS conversion reached 99%, and no catalyst deactivation was observed within 120h.