Mid-temperature CO2 deoxygenation to CO over Fe-CeO2

CO2 capture and utilization is a must for easing the global warming caused by the uses of fossil fuels. We examine M-CeO2 (M = Cu, Co, and Fe @M/Ce = 2/8) prepared by coprecipitation and hard template synthesis. Fe-CeO2 is the only one showing thermal CO2 deoxygenation to CO at below 700 degrees C after reduction. XRD analyses of as prepared Fe-CeO2 demonstrate the presence of segregated Fe2O3 and CeO2 phases with partial mixing. Both Fe2O3 phase and CeO2 phase show redox during sequential TPR (temperature-programmed reduction)-CO2-TPRx (temperature-programmed reaction) up to 700 degrees C. The evolved Fe0 after TPR appears to be the main active phase for CO2 deoxygenation which becomes oxidized back to Fe2O3 after CO2-TPRx. The results indicate that the interface (interphase) between Fe-domain and CeO2-domain is involved leading to the observed deoxygenation reactivity. That the stripped oxygen from CO2 over Fe-domain can spillover to CeO2 domain is considered as a possible explanation. We perform isothermal CO2 deoxygenation test at 600 degrees C over TPR-treated Fe-CeO2 using oxygen-conducting membrane reactor, and the CO2 deoxygenation capacity is found significantly higher than that observed when in the absence of oxygen conducting membrane. This demonstrates not only the possible oxygen spillover but also the possibility of achieving a sustainable CO2 deoxygenation process.