Gas-solid reaction models of Sr(CuxFe1-x-yTiy)O3-δ perovskite-based oxygen carriers for chemical looping combustion.

Oxygen-deficient Sr(CuxFe1-x-yTiy)O3-δ perovskites have been proposed as innovative oxygen carriers for chemical looping combustion (CLC) and related processes. This study investigates the gas-solid reaction kinetics and underlying mechanisms of Sr(CuxFe1-x-yTiy)O3-δ perovskites in reducing and oxidizing environments via thermogravimetric analysis. Sixteen gas-solid reaction models were examined, and Arrhenius equation parameters were calculated using a model-fitting method. Scanning electron microscopy was utilized to explore the structural changes in perovskites and confirm the calculated results. Results indicated that the reduction of Sr(CuxFe1-x-yTiy)O3-δ perovskites occurred in two stages, with an initial rapid stage that lasted for ∼20 s and a longer stage that was best fit by the R3 model for Cu-containing specimens (activation energy [Ea] values of 38-72 kJ·mol-1) or the F1 model for Cu-free specimens (Ea = 90.3-91.6 kJ·mol-1). By contrast, the oxidation of Sr(CuxFe1-x-yTiy)O3-δ perovskites occurred rapidly in a single stage that was best fit by the R2 model for Cu-containing specimens (Ea = 8.6-14.7 kJ·mol-1) and the F1 model for Cu-free specimens (Ea = 11.1-11.9 kJ·mol-1). Also, the ability to reoxidize reduced Sr(CuxFe1-x-yTiy)O3-δ perovskites using carbon dioxide indicated their applicability in chemical looping carbon dioxide splitting, and the results may be applicable to similar processes using these materials. The study findings elucidate the behavior and reduction pathways of these novel oxygen carriers, potentially contributing to more efficient CLC processes.