The low-cost and environmentally friendly perovskite-type oxide of Sr 1−x Ca x FeO 3-δ was proposed here as a new oxygen sorbent usable in a high-temperature pressure-swing adsorption (HT-PSA) process for oxygen production (separation) from air. The oxygen sorption/desorption properties of the Sr 1−x Ca x FeO 3-δ samples (x = 0−1.0) were examined at 550 °C by means of thermogravimetric analysis (TGA). Among the examined samples, Sr 0.76 Ca 0.24 FeO 3-δ (x = 0.24) was found to exhibit the largest value (7.8 cm 3 g −1 ) for the amount of reversibly sorbed/desorbed oxygen by the change in oxygen concentration between air (21 vol % O 2 ) and 5 vol % O 2 . For such an excellent oxygen sorption/desorption behavior to be verified, the oxygen content (oxygen nonstoichiometry, 3-δ) in Sr 0.76 Ca 0.24 FeO 3-δ was estimated as a function of ambient oxygen concentration. The oxygen content of Sr 0.76 Ca 0.24 FeO 3-δ was sensitive to the oxygen concentration and varied largely with its change, especially in the range of 5−21 vol % O 2 . Thus, it is expected that the large change in oxygen content can result in the large amount of reversibly sorbed/desorbed oxygen even by a small pressure-swing amplitude. Actually, the Sr 0.76 Ca 0.24 FeO 3-δ pellet sample was evaluated as an oxygen sorbent for the HT-PSA process by using a small-column apparatus. As a result, the amount of oxygen production for the Sr 0.76 Ca 0.24 FeO 3-δ pellet sample indicated 4.9 cm 3 g −1 per cycle at 600 °C. This value was approximately two times larger than that for the benchmark sample of La 0.1 Sr 0.9 Co 0.9 Fe 0.1 O 3-δ (LSCF1991).

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Oxygen sorption/desorption properties of SrCo x Fe1–x O3−δ were examined as an oxygen sorbent for a high-temperature pressure-swing adsorption (HT-PSA) process. Perovskite-type structure of the SrCo x Fe1–x O3−δ powder samples was observed in the composition range of 0 ≤ x ≤ 0.85, by using XRD measurements. A temperature-programmed-desorption (TPD) measurement revealed that the oxygen desorption temperature in N2 for the perovskite-type SrCo x Fe1–x O3−δ samples was lowered with increasing x. Consequently, the oxygen desorption temperature of the SrCo0.85Fe0.15O3−δ sample exhibited around 300 °C, which was the lowest of those of the examined samples. A high-temperature X-ray diffraction (HT-XRD) measurement suggested that the oxygen desorption of SrCo0.85Fe0.15O3−δ in N2 occurred, accompanying the phase transition from perovskite-type structure to brownmillerite structure. Isothermal oxygen sorption/desorption behavior of the SrCo x Fe1–x O3−δ samples was examined by means of thermogravimetric analysis (TGA). As a result, it was confirmed that the amount of sorbed oxygen for the SrCo0.85Fe0.15O3−δ sample gave 11.7 cm3 g–1 at 300 °C, which was larger than that (8.6 cm3 g–1) for a benchmark oxygen sorbent (La0.1Sr0.9Co0.9­Fe0.1O3−δ). In order to obtain oxygen-enriched air by using the SrCo0.85­Fe0.15O3−δ pellet sample as the oxygen sorbent, the oxygen separation from synthetic air was carried out by using a small-scale PSA apparatus equipped with a vacuum pump. It was confirmed that the 45 vol % oxygen-enriched air was obtained even at 300 °C, by using this apparatus.