Temperature-programmed reaction of pre-adsorbed CO on iron catalyst: new experimental evidence for competition model

Abstract

The hydrogenation of carbon monoxide on iron catalyst has been studied by the temperature-programmed reaction of pre-adsorbed CO with hydrogen. Two peaks attributed to methane formation appear m the TPR spectra; the first one is sharp and centered at lower temperatures, the second broad with a maximum at higher temperature. The low temperature peak corresponds to the hydrogenation of active surface carbon created from the dissociation of adsorbed CO, while the high temperature peak is shown to originate from the decarbidation of iron carbide. By computer calculation and data fitting, all experimental spectra can be fully explained by a competition for the surface carbon between carbidation of iron and hydrogenation to form methane. The TPR data is consistent with the time-dependent behavior observed by isothermal kinetic studies of the CO hydrogenation on iron catalysts. The results also provide independent experimental evidence for the Competition Model.