Hydrodechlorination of chlorobenzene over NiB/SiO2 and NiP/SiO2 amorphous catalysts after being partially crystallized: A consideration of electronic and geometrical factors

The effect of electronic and geometrical factors on the performance of the crystallized Ni-B and Ni-P amorphous alloys in the gas-phase hydrodechlorination (HDC) was investigated by means of N-2 adsorption, inductively coupled plasma spectroscopy (ICP), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersion X-ray spectroscopy (EDS), hydrogen chemisorption, hydrogen temperature-programmed desorption (H-2-TPD), and the activity evaluation. Through the thermal treatment at 673 K in H-2 flow, SiO2-supported Ni-B amorphous alloy was partially crystallized to metallic Ni, while SiO2-supported Ni-P amorphous alloy was partially crystallized to metallic Ni and Ni3P. The crystallized catalysts have smaller metallic crystallites than SiO2-supported Ni, a reference catalyst prepared by the impregnation method. B and P make different effects on the electron density of nickel in the crystallized samples. It is suggested that the electronic property of Ni strongly affects the catalyst activity, and the electron deficiency of nickel is favorable to promoting the hydrodechlorination of chlorobenzene. Turnover frequency (TOF) of the hydrodechlorination is related to the electronic and geometrical properties of the catalysts. (C) 2008 Elsevier B.V. All rights reserved.