Microstructural Stability of Tailored CaMn0.875-xFexTi0.125O3-δ Perovskite Oxygen Carrier Materials for Chemical Looping Combustion

CaMn1-xTixO3-delta are state-of-the-art perovskite-type oxygen-carrier materials (OCMs) used in gaseous fluidized-bed chemical looping combustion (CLC), which is currently undergoing upscaling and demo campaigns in several large pilot plants around the world. CLC requires control of oxygen release and uptake by the oxygen-carrier material. The flexibility of the perovskite's structure allows a wide range of substitutions, which can be beneficial for tuning the properties. In this study, we investigate the beneficial effect of iron substitution on the microstructural stability of tailored CaMn0.875-xFexTi0.125O3-delta perovskite oxygen carrier materials for chemical looping combustion. The redox performances of the substituted compounds under different reducing atmospheres are discussed. During operation in a fixed-bed reactor, methane conversion occurred without any soot formation. It was demonstrated that iron substitution improved the spontaneous release of oxygen and the oxygen-transfer capacity of the material for moderate iron substitution close to x = 0.15. Iron substitution also effectively limited the degradation of the microstructure of the particles during redox cycling.