Carbon-supported Ni catalysts with enhanced metal dispersion and catalytic performance for hydrodechlorination of chlorobenzene

Novel, highly-dispersed, carbon-supported nickel catalysts with Ni loading from 6.8 to 20.2 wt% were successfully prepared via in situ self-reduction of hybrid Ni-Al layered double hydroxide/carbon (NiAl-LDH/C) nanocomposite precursors, which were assembled by a separate nucleation and aging process accompanied by the carbonization of glucose. The results demonstrated that the carbon component in NiAl-LDH/C precursors serving as the reducing agent could in situ reduce Ni2+ species to Ni-0 upon heating under an inert atmosphere, and that such hybrid structures of NiAl-LDH crystals and carbon matrix facilitated the formation of highly-dispersed and uniform Ni nanoparticles with small diameter and large metal surface area. The composition and structure of supported Ni catalysts was profoundly affected by the composition of the NiAl-LDH/C precursors. The as-synthesized supported catalyst with a Ni loading amount of 18.7 wt% displayed excellent catalytic performance in the liquid phase hydrodechlorination of chlorobenzene, giving 99.3% conversion. It was concluded that the dispersion and loading amount of nickel for supported Ni-based catalysts were both critical aspects responsible for the hydrodechlorination activity.