CO conversion over LaFeO3 perovskite during chemical looping processes: Influences of Ca-doping and oxygen species

As a critical intermediate substance or a target product, CO plays a vital role in the chemical looping processes. The control of CO conversion is significant since chemical looping processes with various target products have different requirements for CO content. In the present work, the CO oxidation behaviors with different oxygen species were investigated experimentally and theoretically with Ca-substituted lanthanum ferrite (LaFeO3) as the oxygen carrier to regulate the CO conversion. The results showed that the CO2 yield increased significantly when the adsorbed oxygen species was removed, suggesting that the lattice oxygen was the active oxygen species. It was consistent with the calculation result that the energy barrier of CO oxidation with lattice oxygen was lower than that with surface adsorbed oxygen. Moreover, the CO2 yield increased with the increase of Ca concentration, indicating that Ca doping was favorable for lattice oxygen migration and further promoted CO oxidation.