Hydrogen production from fossil and renewable sources using an oxygen transport membrane

Oxygen transport membranes (OTMs) made of mixed ion-electron conductors can be used to increase the production of hydrogen from fossil and renewable sources. This study describes two methods for producing hydrogen with La0.7Sr0.3Cu0.2Fe0.8O3−δ (LSCF7328), an OTM material that is easily prepared, exhibits good mechanical properties, and is stable in severe gas conditions. In tests with thin-film (thickness ≈22 μm) LSCF7328 membranes, hydrogen was produced by flowing simulated product streams from CO2 gasification of coal on one side of the OTM and steam on the other side. In this method, the so-called coal gas on the oxygen-permeate side drives the removal of oxygen from the other side of the OTM, where hydrogen and oxygen are produced by water splitting. With CO (99.5% purity) flowing on the oxygen-permeate side, the hydrogen production rate was measured to be ≈4.7 cm3/min-cm2 at 900 °C, indicating that hydrogen can be produced at a significant rate by using product streams from coal gasification. This process also yields a CO2-rich product stream that is ready for sequestration. In another test, a tubular LSCF7328 was found to increase the hydrogen production from ethanol reforming by supplying high-purity oxygen from air.