Sr1-xCaxFeO3-δ as a New Oxygen Sorbent for the High-Temperature Pressure-Swing Adsorption Process

The low-cost and environmentally friendly perovskite-type oxide of Sr1-xCaxFeO3-delta 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-delta samples (x = 0-1.0) were examined at 550 degrees C by means of thermogravimetric analysis (TGA). Among the examined samples, Sr0.76Ca0.24FeO3-delta (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-delta) in Sr0.76Ca0.24FeO3-delta was estimated as a function of ambient oxygen concentration. The oxygen content of Sr0.76Ca0.24FeO3-delta 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 Sr0.76Ca0.24FeO3-delta 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-delta pellet sample indicated 4.9 cm(3) g(-1) per cycle at 600 degrees C. This value was approximately two times larger than that for the benchmark sample of La0.1Sr0.9Co0.9Fe0.1O3-delta (LSCF1991).