Air separation and selective oxygen pumping via temperature and pressure swing oxygen adsorption using a redox cycle of SrFeO₃ perovskite

The achievement of low oxygen partial pressures is beneficial in a number of applications, including the production of nitrogen for the Habor-Bosch process, one of the largest industrial chemical processes. It has been suggested in the literature that a redox cycle can be utilized for selective oxygen adsorption, with the potential for application in oxygen separation and compression processes. In this work we demonstrate this concept and show the feasibility of using a temperature and pressure swing redox cycle to chemically absorb oxygen gas at a low partial pressure of 10⁻⁶ bar. The redox material used was the perovskite oxide SrFeO₃, chosen for its relatively low reduction temperature and strong oxygen affinity. The material's intrinsic thermodynamics and low temperature kinetics were both investigated using thermogravimetric analysis. Multiple reduction and oxidation experiments were conducted, with oxidation performed under both synthetic air and inert gas with 1% O₂ concentration. The results show successful trials of oxygen removal resulting in inert gasses with ppm level oxygen impurities and no degradation of the material over multiple cycles. Thermodynamic considerations suggest that with further development this technology could offer a very attractive, reversible cycle for the removal of oxygen impurities from gas streams, particularly in combination with conventional pressure swing adsorption.