Enhanced metal dispersion and hydrodechlorination properties of a Ni/Al_2O_3 catalyst derived from layered double hydroxides

摘要

An Ni~(2 +) s(-) Al~(3 +) s(-) CO_3~(2 -)-layered double hydroxides (NiAl-LDHs) precursor has been synthesized in the pores of spherical γ-Al_2O_3 particles. After calcination at 500 °C, a NiO/γ-Al_2O_3 catalyst precursor was obtained. X-ray photoelectron spectroscopy, temperature programmed reduction, and temperature programmed desorption of hydrogen showed that in the material prepared by calcination of NiAl-LDHs supported on Al_2O_3, the NiO was characterized by higher reduction temperature, stronger interactions with Al_2O_3, and higher nickel dispersion compared with the NiO in a material prepared by conventional impregnation of γ-Al_2O_3 with an aqueous solution of Ni~(2+) ions followed by calcination at 500 °C. The vapor phase hydrodechlorination of chlorobenzene using molecular hydrogen was studied using Ni/γ-Al_2O_3 catalysts prepared by reduction of the NiO/γ-Al_2O_3 catalyst precursors synthesized by the two different methods. Under identical reaction conditions, the Ni/γ-Al_2O_3 catalyst obtained from the LDHs precursor exhibited not only higher activity but also better stability.