The Effect of the Heat Treatment of Pd Thin Film Alloy on the Hydrogenation of Olefins

Abstract

Abstract Pd–(B, P) thin film alloys have been prepared by an RF sputtering method. Before heat treatment, the selectivity for the partial hydrogenation of olefins increased with the increase in the B or P concentration in the Pd–(B, P) films. After the heat treatment, on the other hand, the selectivity for the partial hydrogenation was reduced over the Pd films with a low B or P concentration. However, in the case of the Pd films with a high B or P concentration, the selectivity was enhanced by the heat treatment. The high selectivity after the heat treatment was explainable in terms of the small ensemble size, the low electron density of Pd, and the appearance of a Pd3B, Pd4.8P, or Pd5P2 phase in the Pd films with a high B or P concentration. A sputtered film is known to have a columnar structure. This columnar structure was deduced to be controlled both by the alloying of Pd with B or P and by the heat treatment, so as to exhibit the high selectivity for the partial hydrogenation of olefins.