Simulated front-end acetylene hydrogenation over single-atom Pd-Ag/Al2O3 egg-shell catalyst: effect of Ag:Pd ratio

A series of egg–shell 0.15% PdAg/Al 2 O 3 single-atom catalysts was synthesized for front-end acetylene hydrogenation. The Ag:Pd ratio was varied from 1 to 10. All samples were characterized by XPS, EXAFS and CO-DRIFTS. Selected catalysts were characterized by HRTEM. The formation of PdAg bimetallic alloy nanoparticles with Pd single atoms as active sites was demonstrated. An egg-shell distribution of the PdAg active component was confirmed by optical microscopy. The catalytic performance of the 0.15%PdAg/Al 2 O 3 catalysts was tested in simulated front-end selective hydrogenation of acetylene at H 2 :C 2 H 2 ratio of 20. Under these conditions, the Pd 1 Ag 10 /Al 2 O 3 exhibited the highest selectivity toward ethylene formation (ca. 94% at 90% acetylene conversion). Finally, it was demonstrated that compared to the monometallic Pd/Al 2 O 3 catalyst, an excess of the Ag component completely suppresses any local thermal runaway effects.