Pd-Ag/ alpha -Al sub(2)O sub(3 ) Catalyst Deactivation in Acetylene Selective Hydrogenation Process

The selective hydrogenation of acetylene to ethylene over Pd-Ag/ alpha -Al sub(2)O sub(3) catalysts prepared by different impregnation/reduction methods was studied. The best catalytic performance was achieved with the sample prepared by sequential impregnation. A kinetic model based on first order in acetylene and 0.5th order in hydrogen for the main reaction and second-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. Coke deposition amounts showed a good correlation with catalyst deactivation rate constants, indicating that coke formation should be the main cause of catalyst deactivation. The long-term behavior of the Pd-Ag/ alpha -Al sub(2)O sub(3) catalyst in selective hydrogenation of C sub(2)H sub(2) to C sub(2)H sub(4) can be well determined by a kinetic model based on first order in C sub(2)H sub(2) and 0.5th order in H sub(2) for the main reaction and a second-order independent decay law for catalyst deactivation. Coke amounts over catalysts indicated that coke formation was the main cause of catalyst deactivation.