Methane oxidation over dual redox catalysts

The objective of this research is to develop approaches to direct catalytic oxidation of methane over oxides that are doubly doped with transition metal ions. The desired process aims at employing a double redox mechanism, where one redox couple is utilized for activation of oxygen and another for the trapping of CH{sub 3} radicals. The methyl radicals can either recombine, giving C{sub 2} hydrocarbons, or be converted, via electron transfer reaction, to carbocations. The latter species can react with surface OH{sup {minus}} groups to form methanol or formaldehyde. To choose from several possible catalytic systems, this research initially involved the characterization of the micromorphology and crystalline dimensions of zinc oxide catalysts doped with Cu, Fe, and Sn by scanning electron microscopy. In addition, the determination of surface composition and oxidation states by X-ray photoelectron spectroscopy was carried out. A newly constructed high temperature catalytic testing system has been calibrated (flow meters and temperature controllers), tested for possible gas leaks and integrated with a gas chromatographic analytical unit. A preliminary catalytic test study over a Cu/Fe/ZnO sample was performed. The following products of the methane coupling reaction was found: C{sub 2}H{sub 6}, C{sub 2}H{sub 4} and H{sub 2}O together with CO{sub 2}. The maximum space time yield of 14 mmol C{sub 2} hydrocarbons/g cat/h was obtained at 848{degrees}C