COLL 304 |
| Wilfred T. Tysoe, Department of Chemistry and Laboratory for Surface Studies, UW-Milwaukee, 3210 N Cramer St, Milwaukee, WI 53211 and D. J. Stacchiola, Department of Chemistry and Laboratory for Surface Studies, University of Wisconsin-Milwaukee, 3210 N. Cramer St., Milwaukee, WI 53211. |
| The ultrahigh-vacuum reaction pathways for palladium-catalyzed acetylene trimerization and hydrogenation, and ethylene hydrogenation are compared with those occurring under realistic, high-pressure conditions. These are selected since a model Pd(111) single crystal sample provides a good model for the working catalysts. In addition, all of the reactions proceed in ultrahigh vacuum allowing the reaction pathway to be studied in detail. The nature of the surface intermediates is probed using reflection-absorption infrared spectroscopy (RAIRS) where, for example, it is shown that ethylene is di-σ-bonded on clean Pd(111), but forms a more weakly bound π-bonded species on a hydrogen pre-covered surface, an effect that is shown to be due to subsurface hydrogen. The nature of the catalyst surface is monitored under reaction conditions using photoelastic modulation RAIRS, which effectively removes contributions from the gas phase, while allowing surface species to be detected. |
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Vibrational Analyses of Dry and Wet Surfaces
8:30 AM-11:30 AM, Tuesday, March 30, 2004 Marriott -- Grand Ballroom H, Oral
Division of Colloid and Surface Chemistry |