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 PUSiO2 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 (CO)-C-12 and (CO)-C-13, 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 (similar to 3x) 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. (c) 2007 Elsevier Inc. All rights reserved.