Surface characterisation of Pd-Ag/Al2O3 catalysts for acetylene hydrogenation using an improved XPS procedure

Abstract

Effects of pretreatment on the surface of alumina-supported Pd-Ag catalysts with oxygen or oxygen-containing compounds (NO, N2O, CO and CO 2) have been studied using an improved X-ray photoelectron spectroscopy (XPS). Surface analysis was performed either before or after the selective hydrogenation of acetylene. Analysis of the surface after reduction shows evidence of a Pd-Ag alloy. The binding energy of the Pd 3d is not affected by pretreatment, whereas a significant shift of the Ag 3d is revealed after NO and N2O pretreatment. The surface after reaction shows no state change of either Pd or Ag compared to those measured prior to reaction, which is in agreement with the reactivity test; th..