Preparation and characterization of NiO/CeO2-ZrO 2/WO3 catalyst for ethylene dimerization: Effect of CeO2 doping and WO3 modifying on catalytic activity

Abstract

A series of catalysts, NiO/CeO2-ZrO2/WO3, for ethylene dimerization was prepared by the precipitation and impregnation methods. For NiO/CeO2-ZrO2/WO3 sample, no diffraction line of nickel oxide was observed up to 40 wt%, indicating good dispersion of nickel oxide on the surface of catalyst. The hexagonal and monoclinic phases of WO3 up to the calcination temperature of 500°C were observed, whereas the hexagonal phase of WO3 completely was transformed into monoclinic phase of WO3 at 600°C and above. The role of CeO2 in the catalysts was to form a thermally stable solid solution with zirconia and consequently to give high surface area and acidity. The catalytic activities for ethylene dimerization were correlated with the acidity of catalysts measured by the ammonia chemisorption method. 25-NiO/5-CeO2-ZrO2/15-WO3 containing 25 wt% NiO, 15 wt% WO3 and 5 mol% CeO2, and calcined at 400°C exhibited a maximum catalytic activity due to the effects of WO 3 modifying and CeO2 doping.