AVS 46th International Symposium
    Surface Science Division Monday Sessions
       Session SS2-MoM

Paper SS2-MoM2
Catalytic Oxidation of Unsaturated C@sub 3@ Hydrocarbons on the Pt (111) Surface

Monday, October 25, 1999, 8:40 am, Room 607

Session: Catalysis on Metals
Presenter: A.M. Gabelnick, University of Michigan
Authors: A.M. Gabelnick, University of Michigan
A.T. Capitano, University of Michigan
D.J. Burnett, University of Michigan
D.A. Fischer, National Institute of Standards and Technology
J.L. Gland, University of Michigan
Correspondent: Click to Email
The catalytic oxidation of unsaturated C3 hydrocarbons (propylene and methylacetylene) has been studied in-situ in oxygen pressures ranging from UHV to 0.01 torr on the Pt(111) surface. Using a combination of kinetic and spectroscopic in-situ fluorescence yield soft X-ray techniques, we have characterized the oxidation of these hydrocarbons based on absolute carbon coverage and identified oxidation intermediates spectroscopically. The adsorbed intermediates for oxidation of preadsorbed propylene, propylene catalytic oxidation (both propylene and oxygen in the gas phase), and methylacetylene oxidation have been characterized. Despite differences in these intermediates, skeletal oxidation begins at the same temperature, indicating a common rate limiting step in the oxidation process. In the catalytic oxidation of propylene, dehydrogenation of propylene occurs prior to skeletal oxidation, even with both propylene and oxygen in the gas phase. In pressures of oxygen, a monolayer of propylene and methylacetylene completely oxidize by 450 K, with skeletal oxidation of both hydrocarbons beginning near 320 K. Quantitative kinetic studies of methylacetylene oxidation over a range of conditions enabled the determination of both the activation energy and order of the reaction in oxygen. Experiments performed with coadsorbed oxygen confirm that O(a) is the oxidizing agent.