Study of Cs-promoted, alpha-alumina-supported silver ethylene-epoxidation catalysts .1. Characterization of the support and As-prepared catalyst

An alpha-alumina support and a Cs-promoted Ag/alpha-Al2O3 ethylene-epoxidation catalyst prepared on this same support have been characterized using secondary electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDS), ion scattering spectroscopy (ISS), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The SEM micrographs indicate that the alpha-alumina is crystalline with a well-defined plane exposed and that the Ag covers the support surface uniformly as a thin film. The EDS data also support the assertion that both surfaces are fairly uniform with regard to composition. ISS data exhibit features due to many contaminants such as C, N, Ca, and Ni on the alpha-alumina, as well as Na and Si binder materials which are also observed with AES and XPS. The XPS chemical-state data for the O, Al, Na, C, and Ag are complex, indicating that multiple chemical states of each element are present. Apparently, Ag is present predominantly as Ago, but Ag2O and Ag metal are also present. (C) 1996 Academic Press, Inc.