Single-Atom Alloy Pd1Ag6/Al2O3 Egg-Shell Catalyst for Selective Acetylene Hydrogenation

Here, we report the synthesis of a single-atom alloy Pd₁Ag₆/Al₂O₃ catalyst with an egg-shell distribution of the active component over the catalyst granules for the selective hydrogenation of acetylene traces in ethylene. The formation of an egg-shell structure has been confirmed by electron probe microanalysis, which demonstrates that metals are predominantly localized at a depth of 130–160 µm from the granule surface. Transmission electron microscopy and X-ray photoelectron spectroscopy have provided evidence of the formation of a PdAg substitutional solid solution with electron density transfer from Ag to Pd. The formation of Pd₁ single sites has been confirmed by IR spectra of adsorbed CO. In the selective hydrogenation of acetylene, the synthesized single-atom alloy Pd₁Ag₆/Al₂O₃ with an egg-shell distribution shows high selectivity, which radically exceeds the selectivity of the palladium counterpart.