文摘
The low-cost and environmentally friendly perovskite-type oxide of Sr1–xCaxFeO3-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 Sr1–xCaxFeO3-δ samples (x = 0–1.0) were examined at 550 °C by means of thermogravimetric analysis (TGA). Among the examined samples, Sr0.76Ca0.24FeO3-δ (x = 0.24) was found to exhibit the largest value (7.8 cm3 g–1) for the amount of reversibly sorbed/desorbed oxygen by the change in oxygen concentration between air (21 vol % O2) and 5 vol % O2. For such an excellent oxygen sorption/desorption behavior to be verified, the oxygen content (oxygen nonstoichiometry, 3-δ) in Sr0.76Ca0.24FeO3-δ was estimated as a function of ambient oxygen concentration. The oxygen content of Sr0.76Ca0.24FeO3-δ was sensitive to the oxygen concentration and varied largely with its change, especially in the range of 5–21 vol % O2. 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 Sr0.76Ca0.24FeO3-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 Sr0.76Ca0.24FeO3-δ pellet sample indicated 4.9 cm3 g–1 per cycle at 600 °C. This value was approximately two times larger than that for the benchmark sample of La0.1Sr0.9Co0.9Fe0.1O3-δ (LSCF1991).