High temperature sorption of carbon dioxide on perovskite-type metal oxides

Understanding chemical sorption of carbon dioxide on perovskite-type oxides is important to applications of these metal oxides as sorbents, membranes and catalysts in several separation and reaction processes. The present study reports on equilibrium and kinetic data for chemical sorption of carbon dioxide on Sr0.5Ca0.5Co0.5Fe0.5O3. At temperatures below 750 °C the sorption process can be described by the classical theory for chemical sorption by means of the gas–solid reaction. The equilibrium carbon dioxide sorption capacity is independent but the sorption kinetic rate is a strong function of temperature and carbon dioxide pressure. Above 750 °C, the equilibrium carbon dioxide sorption capacity decreases with increasing temperature and decreasing carbon dioxide pressure. It is suggested that at the high temperatures the reaction products include solid solution of SrCO3/SrO and CaCO3/CaO, respectively. The equilibrium carbon dioxide sorption capacity depends on the conversion of the carbonate to the corresponding metal oxide determined by temperature and carbon dioxide partial pressure.