The objectives of this project are: (1) to determine the sites for propylene adsorption and activation on cuprous oxide (Cu20) surfaces, (2) to determine the degree of charge transfer between the catalyst and the adsorbed intermediate, (3) to determine if the promotion effect of methyl bromide is due to a chemical effect or a "macroscopic" electrical effect associated with Fermi level pinning on this semiconducting catalyst surface, and (4) to study the reaction kinetics under realistic (one atmosphere) reaction conditions to test the usefulness of a metal-oxide single crystal as a model catalyst. The work will combine ultrahigh-vacuum surface science techniques with high pressure reaction measurements. Low energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) will be used to determine the site for propylene activation. Four-point probe conductivity measurements will be used to determine the partial charge on the reaction intermediates and to study the behavior of the catalyst Fermi level in the presence of methyl bromide. A combined high pressure reaction cell/UHV surface analysis system will be used to characterize the reaction kinetics of the system and to perform post-reaction analysis on the surface. The work is aimed at resolving questions about the nature of the reaction mechanism and intermediates. Besides being an important industrial reaction in its own right, this system may serve as a model for other allylic oxidations of olefins.
