Characterization and evaluation of Ag–Pt/SiO2 catalysts prepared by electroless deposition

A series of Ag–Pt/SiO2 catalysts have been prepared by the electroless deposition of Ag onto a Pt/SiO2 catalyst. Results indicate that Ag deposition does not readily occur on the SiO2 support, but is essentially restricted to the Pt surface. The Ag–Pt catalysts have been characterized by FTIR of adsorbed 12CO and 13CO, which suggest that Ag is preferentially located on Pt(111) sites rather than the more coordinatively-unsaturated corner and edge sites. Hydrogenation of 3,4-epoxy-1-butene (EpB), a multifunctional olefin, was chosen as a probe reaction. Reaction data indicate that ED-derived catalysts provide a more targeted Ag placement on the Pt surface than traditional incipient wetness catalysts. EpB conversion increased dramatically (image) with the addition of sub-monolayer coverages of Ag on the Pt surface. Conversely, activity for propylene hydrogenation decreased with increasing Ag coverages. The enhanced EpB hydrogenation appears to be due to a Ag-induced decrease in EpB adsorption energy on surface Pt sites.