Adsorption and Reaction of CO_2 and Mo_2C Catalyst

摘要

The reaction between CO_2 and ZSM-5 and SiO_2-supported Mo_2C catalysis, 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 CO_2 occurred above 823 K to give CO and O atoms. Using ~(13)CO_2 it was possible to establish that a fraction of O atoms oxidized the carbon of Mo_2C into CO, the other part reacted with Mo to give MoO_x species. The ratio of ~(13)Co/~(12)Co 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 Mo~(6+) at every temperature, Mo~(4+) and Mo~(5+) were present in the sample even after the reaction at 1073 K. The reaction proceeded at a faster rate on Mo_2C/ZSM-5 than on Mo_2/SiO_2.