Abstract: Ni₂P/SiO₂ was pretreated with a 0.8%H₂O-99.2%H₂ flow at 303, 514, and 543 K. The Ni₂P/SiO₂ catalysts before and after treatment were characterized by N₂ adsorption-desorption, X-ray diffraction, inductively coupled plasma atomic emission spectrometry, H₂ temperature-programmed desorption, and in situ diffuse reflection infrared Fourier transform spectroscopy, and their activities in the hydrodechlorination of chlorobenzene (CB) were tested in a fix-bed reactor. There was no difference in BET specific surface area, pore structure, the Ni₂P crystallite size, the Ni content, and the Ni/P ratio for the Ni₂P/SiO₂ catalysts before and after treatment. The treatment at 303 K did not decrease the density of exposed Ni sites on Ni₂P/SiO₂, while the treatment at 514 and 543 K led to the decrease of exposed Ni sites and the increase of the P–OH groups on Ni₂P/SiO₂. Under the conditions of 513 K, the CB space velocity of 3.75 ml/(g·h), and the H₂/CB molar ratio of 9.0, the initial CB conversions on the treated Ni₂P/SiO₂ catalysts exceeded 93.8%, which was much higher than that (5.6%) on the untreated one. The promotion effect of steam treatment on the activity of Ni₂P/SiO₂ may be related to a synergism between the Ni sites and the P–OH groups.

Key words: nickel phsphide, hydrodechlorination, steam treatment, acidity