The deactivation of the Ni2P/SiO2 catalyst in the hydrodechlorination of chlorobenzene was studied. To better illuminate the reasons for the deactivation, the effect of HC1 on the structure and activity of Ni2P/SiO2 was investigated. For comparison, the deactivation of the Ni/SiO2 catalyst was also involved. It was found that the Ni2P particles possessed good resistance to HC1 poison and to sintering, which is ascribed to the electron-deficiency of Ni delta+(0 < delta < 1) site in Ni2P. Acted as the Lewis and Bronsted acid site, the Ni delta+ site and the P-OH group on Ni2P/SiO2 catalyzed the formation of the carbonaceous deposit that was difficultly eliminated by hydrogenation. The carbonaceous deposit covered the active sites and might also induce a decrease in the Ni2P crystallinity, subsequently leading to the Ni2P/SiO2 deactivation. Different from Ni2P/Si02, Ni/SiO2 was mainly deactivated by the chlorine poison and the sintering of nickel crystallites. (C) 2014 Elsevier B.V. All rights reserved.