CeO2-Modified Fe2O3 for CO2 Utilization via Chemical Looping

Abstract

Both pure and mixed CeO2–Fe2O3 were prepared for CO2 reduction to CO by chemical looping. The crystallographic structure of the investigated materials was monitored in situ during H2 reduction and CO2 oxidation. A solid solution of iron in ceria was identified. Up to 70 wt % CeO2, a distinct Fe2O3 hematite phase occurred next to the solid solution. At higher CeO2 content, no diffraction patterns corresponding to iron oxide phases were present, but upon H2 temperature programmed reduction, a metal iron phase appeared. The Fe2O3 phase at lower CeO2 content, during H2 temperature programmed reduction, completely reduced at 700 °C while the solid solution was only partially reduced. For all investigated samples, CO2 reoxidized iron in one-step to Fe3O4 from 500 °C during temperature programmed oxidation. Adding CeO2 to Fe2O3 was beneficial for the materials activity and stability. Isothermal redox cycles were performed without significant loss of CO2 conversion. The highest CO yield was obtained for 20 wt % CeO2–Fe2O3, but 50 and 70 wt % CeO2–Fe2O3 were the most stable combinations.