Chapter 16: Perovskite Membranes for High Temperature Oxygen Separation

Dense perovskite membranes with mixed oxygen-ionic and electronic conductivity can selectively transport oxygen from the feed side of the membrane at a high oxygen partial pressure to the permeate side at a low oxygen partial pressure. High temperatures of about 800 to 900 °C guarantee sufficient high oxygen flux due to the increased oxygen ion mobility with increasing temperature. Production of high purity oxygen (theoretically up to 100 %) using a oxygen transporting perovskite membrane can be realized by increased oxygen partial pressure on the feed side which can be realized by pressurized air or oxygen-enriched air, and by reduced oxygen partial pressure on the permeate side, which can be used by vacuum pumps or by using steam as sweep gas. The gradient of the oxygen partial pressure across the membrane as driving force can be increased thus increasing the oxygen flux.

Other examples demonstrate the use of oxygen transporting perovskite membranes in membrane reactors. On the feed side oxygen is produced by e.g. thermal water splitting or NO_x decomposition. The produced oxygen is then removed as oxygen ion (O²⁻) to the other side of the membrane, where it is consumed by a partial oxidation of methane to synthesis gas (a CO:H₂ mixture of the ratio 1:2) or by the oxidative alkane dehydrogenation to the corresponding olefins.