Hydrogen separation through the use of mixed oxygen ion and electron conducting membranes (I): theoretical analysis

Membrane-based processes are becoming increasingly important in the field of industrial gas separation. Such processes are attractive from the standpoint of high separation selectivity and high conversion ratios in cases involving gas phase and gas–solid reactions. In particular, the application of dense ceramic mixed ionic and electronic conducting membranes to separate gases such as oxygen through ambipolar transport of oxygen ions and electrons and hydrogen through ambipolar transport of protons and electrons from gas mixtures at elevated temperatures (>500°C) is gaining increasing importance. As a specific example, the requirement of high-purity tonnage hydrogen with less than 10 ppm carbon monoxide impurity levels would be absolutely essential for low-temperature proton exchange membrane fuel cells to gain wide market acceptance. We analyze herein a novel membrane-based hydrogen separation process which has heretofore not been widely reported in the literature.