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Iron-based oxygen carriers with a CeO2support have interesting redox applications in chemical-looping combustion (CLC). CeO2behaves as an active support for many oxygen carrier applications because of the reversible release of lattice oxygen. High temperature processes may lead to improved process efficiency; however, the poor thermal stability of CeO2gives rise to a need for oxygen carriers that can resist sintering and agglomeration and maintain reactivity after multiple reduction and oxidation (redox) cycles during in situ gasification chemical-looping combustion (iG-CLC) at 1100 °C. In the present study, Fe-based oxygen carriers on CeO2, ZrO2, and Ce0.75Zr0.25O2supports were prepared by a coprecipitation method. The redox stability, reactivity, and sintering of the oxygen carriers were evaluated to investigate the effect of the CeO2–ZrO2solid solution support. The oxygen transport capability was evaluated in a drop tube fixed-bed reactor under iG-CLC conditions with coal char at 1100 °C for 10 redox cycles. The CeO2–ZrO2solid solution improved the oxygen mobility of the support from the creation of more oxygen defects. The Fe–Ce oxygen carrier had the highest oxygen transport capability because of the formation of cerium orthoferrite (CeFeO3) during high temperature reduction. The Fe–Ce–Zr oxygen carrier showed improved reactivity over the Fe–Ce oxygen carrier as the number of redox cycles increased. The oxygen carriers, before and after multiple redox cycles, were characterized by X-ray diffraction, scanning electron microscopy, and surface/pore analysis.

Chemical-looping combustion with oxygen uncoupling (CLOU) is a process using gaseous or solid hydrocarbon fuels and is a promising carbon capture and storage (CCS) technology. In CLOU, combustion of the fuel is achieved through the release of gaseous O2from an oxygen carrier material such as CuO and is favored at high temperatures and low O2partial pressures. The primary objectives of this study were to (1) compare values for the apparent rate constant kov(T) for the overall rate of reduction of a CuO carrier, either alone or in the presence of coal char obtained from the pyrolysis of Powder River Basin (PRB) coal, and (2) develop and validate a computational fluid dynamics (CFD) model for the CuO/PRB coal char system based on known kinetics of the individual CuO and Cu2O reduction, combustion, and gasification reactions. Two oxygen carriers consisting of 20 wt % CuO/Al2O3and 9 wt % CuO/Al2O3were prepared by physical mixing and by incipient wetness impregnation (IWI), respectively. Kinetic analyses were conducted in the temperature range of 850–1100 °C. The CFD model typically reproduced experimental values of kov(T) to within ±10%. The increase in kov(T) caused by addition of only 0.075 g of PRB char per gram of CuO was modest at 1100 °C, but was more than 3-fold at 850 °C. Combustion and gasification of the coal char not only produced CO, opening another pathway for CuO reduction in addition to the CLOU reaction, but also resulted in the over-reduction of Cu2O to the undesired metallic Cu. Production of Cu metal increased with respect to char loading.