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The investigation of the catalytic properties of the CaF_2 modifiedCeO_2 catalysts for the methane oxidative coupling (MOC) to prepare C_2 hydro-carbons indicated that most of the CaF_2 modified CeO_2 catalysts were efficientfor the MOC reaction. Addition of CaF_2 to CeO_2 can make the C_2 selectivity in-crease from 2. 2％ (over CeO_2) to 46-63％, and the CH_4 conversion increasefrom 26％ to 28-30％. When the CeO_2 content was decreased within a defi-nite region, the activity and C_2 selectivity of the catalysts increased remark-ably. The XRD characterization revealed that F~-—O~(2-)exchange happened be-tween CaF_2 and CeO_2 phases. TPD, XPS, Raman and ESR experiments indicat-ed that O~-, O_2~(2-) and O_2~-species were formed over CeO_2/CaF_2 catalysts. Withthe increase of CaF_2 content in the catalysts, the kinds and the surface concen-trations of the above mentioned oxygen species decreased, while the C_2 selectivi-ty increased.
The investigation of the catalytic properties of the CaF_2 modified CeO_2 catalysts for the methane oxidative coupling (MOC) to prepare C_2 hydro-carbons indicates that most of the CaF_2 modified CeO_2 catalysts were efficient for the MOC reaction. Addition of CaF_2 to CeO_2 can make the C_2 selectivity in-crease from 2.2% (over CeO 2) to 46-63%, and the CH 4 conversion increase from 26% to 28-30%. When the CeO 2 content was decreased within a definitive region, the activity and C 2 selectivity of The XRD characterization revealed that F ~ - O ~ (2-) exchange happened be-tween CaF_2 and CeO_2 phases. TPD, XPS, Raman and ESR experiments indicat-ed that O ~ -, O_2 ~ (2-) and O_2 ~ -species were formed over CeO_2 / CaF_2 catalysts. With these increase of CaF_2 content in the catalysts, the kinds and the surface concen- trations of the above mentioned oxygen species decreased, while the C_2 selectivi- ty increased.