Structure of NiOSiO catalyst for ethylene dimerization as observed by infrared absorption

Abstract

Nickel oxide-silica catalysts were prepared by precipitation from an acidic solution of a nickel salt-sodium silicate mixture, and the structure of prepared catalyst was examined by infrared absorption spectra. Two types of nickel-hydrosilicate, montmorillonite and antigorite, are formed in the catalysts, the relative abundance of which is indicated by ir bands at 710 and 665 cm−1. It is shown that the higher the final pH in precipitation, or the higher the Ni/SiO2 ratio in the starting mixture, the more the formation of antigorite. The NiO/SiO2 catalysts thus prepared are activated for ethylene dimerization by evacuation at elevated temperatures, giving two optimum temperatures, about 100 and 600°C. The first activation is ascribed to a montmorillonite-type site, while the second activation is ascribed to an antigorite-type site.