Hydrodechlorination of Chlorobenzene Over Ni2P/SiO2 Catalysts: Influence of Ni2P Loading

The influence of Ni2P loading on the properties of Ni2P/SiO2 catalysts was investigated by means of N-2 adsorption-desorption, X-ray diffraction, H-2 and NH3 temperature-programmed desorption, CO chemisorption, inductively coupled plasma atomic emission spectroscopy and activity evaluation for the hydrodechlorization of chlorobenzene. It was found that increasing Ni2P loading results in the decrease of Ni2P dispersion. Higher P/Ni ratio occurs in the catalysts with lower Ni2P loadings, indicating that smaller Ni2P crystallites may more strongly interact with surplus P. We suggest that the acid amount of the Ni2P/SiO2 catalyst is related to the exposed Ni sites and P-OH groups, while Bronsted acidity of P-OH groups facilitates hydrogen spillover. Increasing Ni2P loading is favorable to the catalyst activity, while this effect is not obvious when the Ni2P loading is greater than 9.6 wt%. Apart from the metallic property of Ni2P phase and spilt-over hydrogen species, we propose that the acidity and the role of P in activating reactants should be considered for the catalyst performance.