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The reaction between CO2 and ZSM-5- and SiO2-supported Mo2C catalysts, found to be active in the aromatization of methane, has been studied in a flow and static system by measuring changes in the gas composition. The reaction was also followed with X-ray photoelectron spectroscopy. The decomposition of CO2 occurred above 823 K to give CO and O atoms. Using 13CO2 it was possible to establish that a fraction of O atoms oxidized the carbon of Mo2C into CO, the other part reacted with Mo to give MoO x species. The ratio of 13CO/12CO varied between 5 and 6.0. XPS study confirmed the oxidation of Mo resulting in the formation of Mo ions of various oxidation states. Although the dominant oxidation state is Mo6+ at every temperature, Mo4+ and Mo5+ were present in the sample even after the reaction at 1073 K. The reaction proceeded at a faster rate on Mo2C/ZSM-5 than on Mo2C/SiO2.

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