Isotopic exchange measurements of the rates of adsorption/desorption and interconversion of CO and CO2 over chromia-promoted magnetite: Implications for water-gas shift

Isotopic exchange measurements were used to investigate the adsorption/desorption and inter-conversion of CO and CO2 on chromia-promoted magnetite at 565 and 627 K. The interconversion between CO and CO2 was shown to take place through surface adsorbed species. Furthermore, the rate of interconversion was limited by the rates of adsorption/desorption, indicating either that adsorbed CO and CO2 are in equilibrium on the surface or that the adsorption of CO and CO2 leads to the same surface species, e.g., a surface carbonate species. A kinetic model for the water-gas shift over magnetite is proposed, and the results of the isotopic exchange measurements and volumetric adsorption data are used to estimate the rate and equilibrium constants for this model.