An Egg-Shell Pd-Ag/α-Al2O3 Catalyst for Tail-End Acetylene Selective Hydrogenation

In the present research, egg-shell Pd-Ag/α-Al2O3 catalysts prepared by impregnation method using self-improved spherical alumina support with BET 13.34m2/g and pore volume 0.36cm3/g were used for the hydrogenation of acetylene in the presence of a large excess of ethylene (tail-end cuts) and their activity-selectivity patterns were compared with the commercial one. All of the synthesized catalysts were tested under 60C, 10bar, space velocity 6500h-1 and H2/C2H2 ratio 1.5 (mol/mol) which is the same as an industrial plant.The effect of impregnation operating parameters, such as pH of the impregnation solution and impregnation type, on palladium penetration depth and palladium uptake was investigated.pH 1.5 is best for impregnation solution.Catalytic performance tests showed that for Pd-Ag/α-Al2O3 catalysts,sequential impregnation was a suitable method for the active metal. By controlling the synthesis condition, the best Pd-Ag/α-Al2O3 sample was an egg-shell one in which Pd was loaded evenly in a layer with thickness 20-30µm. This sample gave ethylene selectivity of 100% and acetylene conversion of 58% which is higher than the commercial one.