Influence of Support Structural Characteristics on Long-term Performance of Pd-Ag/α-Al2O3 Catalyst for Tail-end Acetylene Selective Hydrogenation

Abstract

Abstract The selective hydrogenation of acetylene to ethylene in acetylene/ethylene mixture over Pd-Ag/α-Al2O3 catalysts prepared by sequential impregnation method was studied. The α-Al2O3 support was prepared by thermal treatment of γ-Al2O3 in temperature range of 1,090–1,100 °C. The samples were characterized for their structural properties and coke deposition. They showed egg-shell structure with penetration depth increasing with sintering temperature of the support. A kinetic model based on 1st order in acetylene and 0.5th order in hydrogen for the main reaction and 2nd order independent decay law for catalyst deactivation was used to fit the conversion-time data and to obtain quantitative assessment of catalyst performances. Fair fits were observed from which the reaction and deactivation rate constants were evaluated. The highest selectivity to ethylene, and therefore best performance, was obtained for the highest calcination temperature which was attributed to its lower acidity and larger pore diameters.