In Situ Synthesis of Unsupported Nickel Phosphides and Their Activity in 1,4-Dichlorobenzene Hydrodechlorination

A series of unsupported nickel phosphides were synthesized in situ in a reaction mixture under the conditions of hydrodechlorination of 1,4-dichlorobenzene. Triphenylphosphine and red phosphorus were used as phosphorus sources, beneficial in terms of environmental friendliness and cost effectiveness. Using X-ray fluorescence spectrometry, it was demonstrated that, with red phosphorus as a phosphorus source, a Ni₂P phase was formed even at a Ni/P molar ratio of 1 : 1. The effects of temperature and pressure on the catalytic activity were investigated. The nickel phosphides proved to be reusable in hydrodechlorination: their catalytic activity remained adequate over five reaction cycles. In contrast, an unphosphided nickel-based catalyst exhibited high activity only in the first to third reaction cycles, after which the dechlorination degree abruptly declined due to the formation of NiCl₂.