Properties of PdAg/Al₂O₃ Egg–Shell Single-Atom Catalysts in Front-End Hydrogenation of Acetylene

Two samples of PdAg/Al₂O₃ egg–shell single-atom catalysts, with Ag/Pd ratios of 1 : 1 and 3 : 1, were synthesized and characterized by TEM, XPS, and DRIFTS-CO methods. The formation of bimetallic PdAg alloy nanoparticles with single-atom Pd₁ active sites was demonstrated. Furthermore, a physicochemical characterization showed a egg–shell distribution of the active component. The catalytic performance of the samples was tested in front-end selective hydrogenation of acetylene. The H₂/C₂H₂ ratio in the model mixture was varied from 20 to 60. Under front-end acetylene hydrogenation conditions, the highest ethylene selectivity (about 87 at 90% acetylene conversion) was achieved in the presence of the Pd₁Ag₃/Al₂O₃ catalyst at H₂/C₂H₂ = 20. Finally, it was shown that, unlike the monometallic Pd catalyst, the Ag-promoted catalysts were completely free of any local thermal runaway effect.