Influence of steam and carbon dioxide on the hydrogen flux through thin Pd/Ag and Pd membranes

✍ Scribed by F.C. Gielens; R.J.J. Knibbeler; P.F.J. Duysinx; H.D. Tong; M.A.G. Vorstman; J.T.F. Keurentjes

• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 687 KB
• Volume: 279
• Category: Article
• ISSN: 0376-7388
• DOI: 10.1016/j.memsci.2005.12.002

✦ Synopsis

The influence of CO 2 and steam on the H 2 permeation behavior of high-flux Pd/Ag alloy and Pd membranes has been determined. The membranes -fabricated with microsystem technology (MEMS technology) -are 1.0 and 0.5 m thick; the thin membranes will reveal inhibitive effects more strongly than relatively thick membranes. The H 2 flux through the membranes has been studied for periods of more than 80 h during and after addition of CO 2 or H 2 O to the feed. Measurements have been carried out at 623, 673 and 723 K.

The largest flux reductions found are 70 and 69% at 623 K for H 2 O and CO 2 , respectively. After stopping the steam addition the H 2 permeance restores to its original value. After stopping the CO 2 addition the H 2 permeance increases, but to a value lower than before the CO 2 addition. Surprisingly large time constants have been found for the transient permeance behavior. The inhibitive effect caused by the addition of CO 2 is almost certainly caused by the formation of CO and H 2 O by the reverse water gas shift (WGS) reaction. Besides by adsorption of CO 2 , CO and H 2 O, a far stronger inhibitive effect is caused by carbon, which is formed by the dissociation of CO and CO 2 .