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.