ABSTRACT CTS-9412544 Umit Ozkan This is a fundamental study of the catalytic phenomena involved in the activation and partial oxidation of methane and ethane. The objectives include investigation of the natures of the active sites responsible for alkane activation and oxygen insertion on supported and unsupported vanadia and molybdena catalysts, control of selectivity on these sites by modifiers (both promoters and inhibitors) such as alkali metals, phosphorus, and halides, the roles of coreactants and additives on the reaction schemes, and the reaction networks responsible for partial oxidation of methane and ethane. Catalysts are characterized both before and after reaction using BET surface-area measurements, pore size distribution, X-ray diffraction, X-ray fluorescence, laser Raman spectroscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, secondary-ion mass spectroscopy, and thermal analysis techniques. In - situ laser Raman characterization is combined with isotopic labelling to identify oxygen insertion sites. Steady- state and transient kinetic studies and isotopic labelling are used as mechanistic probes to examine the catalytic routes to partial and complete oxidation. Methane and ethane are readily available inexpensive feedstocks, and the conversion of methane to formaldehyde or methanol and ethane to ethylene or acetaldehyde has been a major objective of catalytic technology. These conversions are easy to achieve, but the fine control needed to isolate these products has been elusive; most processes produce mainly carbon monoxide and carbon dioxide which are formed both from competitive reaction pathways and from further oxidation of the indended products. Better understanding of the operative mechanisms will permit new control strategies to solve this classical problem.
