High-Pressure Reduction Kinetics of Ca₂Fe₂O₅ for Advanced Chemical Looping Steam Reforming

Ca2Fe2O5 stands out as a promising oxygen carrier for chemical looping applications due to its remarkable redox stability and its ability to be completely regenerated by H2O while producing a pure H2 stream. This work systematically investigates the effect of pressure (1 to 20 bar) on the reduction kinetics and the stability (up to 50 cycles) of this oxygen carrier. A comprehensive kinetic model has been developed by integrating experimental data and structural observations, making use of the nucleation and growth (JMAEK) model with an Avrami exponent of 1.5. The total pressure was found to have only a negligible effect on the reduction rate, while the temperature and H2 mole fraction in the feed dominated the kinetics. Steam oxidation was governed by internal mass transfer limitations under the experimental conditions adopted, leading to lower reaction rates as the total pressure increases due to a decrease in the effective diffusivity of the gas. These findings demonstrate the cyclic stability of Ca2Fe2O5 under pressurized conditions and pave the way for its application in the implementation of high-pressure integrated chemical looping processes.