PdAu/YSZ composite hydrogen separation membranes with enhanced stability in the presence of CO

• Published in: Journal of membrane science Vol. 611; no. -
• Main Authors: Lundin, Sean-Thomas B., Patki, Neil S., Zhang, Zhenyu, Fuerst, Thomas F., Wolden, Colin A., Way, J. Douglas
• Format: Journal Article
• Language: English
• Published: United States Elsevier 23.06.2020
• Subjects: 08 HYDROGEN; Carbon monoxide tolerance; Carbon solubility; Coking resistance; Hydrogen separation; Palladium-gold (PdAu) composite membrane
• ISSN: 0376-7388; 1873-3123

The effects of gold composition on the tolerance of palladium-based composite membranes to CO exposure was studied under the presence of high CO concentrations. Membranes with PdAu compositions ranging up to 41% by mass were exposed to binary 50/50 H2/CO gas atmospheres and both hydrogen flux and purity were monitored over time. It was observed that the highest gold composition (41%) suffered no degradation in membrane performance in terms of permeate hydrogen purity and hydrogen permeation flux during the 48 h exposure. Furthermore, for lower gold compositions, X-ray diffraction patterns suggested that carbon entered the film and could be removed by exposure to a non-CO containing gas mixture over time. However, removal of the carbon adversely affected purity; interestingly, some of the purity decline could be reversed upon re-exposure to the CO gas mixture. It is hypothesized that carbon loading in the palladium films causes lattice expansion and may even fill pore defects, thus lowering leaks through the Pd films. Furthermore, this study suggests that a membrane exposed to a CO mixture should not be cycled between CO and non-CO environments, but rather run continuously for best performance. Additionally, the choice of Pd-alloy and metal composition should be considered in regard to its carbon solubility to best predict lifetime performance.