Catalytic hydrodechlorination of condensate oil on highly active and stable nickel phosphide catalysts

Abstract

Catalytic hydrodechlorination of condensate oil on supported nickel phosphide catalysts was investigated in this work. The catalysts were prepared by incipient wetness impregnation in the presence or absence of ethylenediaminetetraacetic acid (EDTA) and characterized by X-ray diffraction, N₂ adsorption, hydrogen temperature-programmed reduction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Among nickel phosphide catalysts with different Ni/P molar ratios, Ni₂P/SiO₂ with Ni/P = 2 existed mainly in the Ni₁₂P₅ crystalline phase and showed the best hydrodechlorination performance. The addition of EDTA during the preparation of Ni₂P/SiO₂ significantly improved the dispersion of Ni₂P on the catalyst and consequently enhanced its catalytic activity. The reactivities of three corresponding representative organochlorine compounds of the chlorinated aromatics, chlorinated alkanes and chlorinated alkenes, respectively, followed the order of chlorobenzene > tetrachloroethylene > 1,3-dichloropropane, which was in the same order of their adsorption energies on Ni₂P/SiO₂ calculated by VASP. Ni₂P/SiO₂-EDTA showed excellent catalytic hydrodechlorination activity and stability for real condensate oil, and the chlorine removal reached 97% under conditions of 300 °C, a LHSV of 3 h⁻¹, a H₂/oil ratio of 200, and 3 MPa in a fixed-bed reactor, and the chlorine removal remained at 96.4% after 160 h on stream.