Modeling of surface intermediates under forced periodic conditions applied to CO2 methanation

Forced oscillations of the carbon dioxide concentration in a hydrogen feed were applied to the carbon dioxide methanation reaction with simultaneous gas phase and surface analysis. The response of the gas phase and surface species to these repeated dynamic conditions show a time shift following the sequence CO₂ → formate → CO → methane, but can be modeled by a simple model involving one single adsorbed surface intermediate and a reservoir in equilibrium with this intermediate. The dynamic behavior of this intermediate is very close to the variation of the IR absorption band associated with formate and carbonate species.