Acetylene semi-hydrogenation over Pd-Zn/CeO2: Relevance of CO adsorption and methanation as descriptors of selectivity

Abstract

The most selective Pd-Zn surfaces for the selective hydrogenation of acetylene to ethylene were recently proposed to be intermetallic in nature, exhibiting only Pd-Zn-Pd units and no Pd-Pd pairs, the later forming bridged CO upon exposure to CO. Ceria-supported Pd-Zn formulations apparently free of Pd-Pd ensembles were prepared and yet led to poor selectivity to ethylene. CO methanation was actually shown to be a better selectivity descriptor in the present case. Only the samples most selective for acetylene semi‐hydrogenation, which were obtained by reduction at temperatures equal or higher than 550 °C, led to negligible CO methanation rates. © 2017 Elsevier B.V