Effect of H2S on the Performance and Long-Term Stability of Pd/Cu Membranes

• Published in: Industrial & engineering chemistry research 2009-04, Vol.48 (8), p.4030-4039
• Main Authors: Pomerantz, Natalie, Ma, Yi Hua
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical engineering; Exact sciences and technology; Separations
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie801947a

The objective of this work was to fabricate palladium membranes with a Pd/Cu alloy top layer and to investigate the performance and long-term stability of the membranes in small concentrations of H2S. The Pd/Cu alloy membranes with compositions of 8, 18, and 19 wt % copper were fabricated using the electroless deposition method on porous Inconel supports and characterized for several thousand hours in H2, helium, and 45−55 ppm H2S/H2 mixtures in the temperature range of 350−500 °C. Upon exposure to the H2S/H2 mixture at 500 °C, the Pd/Cu membranes lost ∼80% of the hydrogen permeance, because of the H2S forming surface sulfides and blocking H2 adsorption sites, with the amount of permeance lost increasing with decreasing temperature. Reintroducing pure H2 recovered some of the hydrogen permeance, showing that some of the H2S poisoning was irreversible. The amount of irreversible poisoning increased as the H2S exposure time increased and the exposure temperature decreased, because of the exothermic nature of H2S adsorption. The helium leak rate of the Pd/Cu membranes decreased after the poisoning experiments, possibly because of sulfur that segregated to the grain boundaries of the Pd/Cu deposits.