Dense metallic membranes degradation

However, dense metal membranes present a few challenges that have, to date, prevented their widespread industrial implementation. The best performing materials, Pd and Pd-alloys, are expensive. Pure Pd displays high H2 permeability and can operate at elevated temperatures, but suffers performance degradation because of poisoning and corrosion from exposure to conmum contaminants (H2S, NH3, CO, CO2, and Hg), hydride formation, and other factors, which will be described in following sections. Pd-alloys can display better chemical stability and mechanical strength than pine Pd, but often at the expense of permeability. 

Gasification and Associated Degradation Mechanisms Applicable to Dense Metal Hydrogen Membranes... 

Morreale B, Cifemo J, Howard B, Ciocco M, Marano J, lyoha O, et al. Gasification and associated degradation mechanisms applicable to dense metal hydrogen membranes. In Bose AC, editor. Inorganic membranes for energy and environmental applications. New York Springer Science + Business Media, LLC. 2009. p. 173-201. 

Exposures of some metal oxide membranes, both dense and porous, to extreme pH conditions (e.g., pH less than 2 or greater than 12) can cause structural degradations, particularly with extended contact time. The extent of degradation depends on the specific phase of the material, porosity, and temperature. Steam can also be deleterious to some metal oxide and Vycor glass membranes. For example, as mentioned earlier, porous glass membranes undergo slow structural changes upon exposure to water due to partial dissolution of silica. 

Gehrke et al. [ 131 ] recently used a dip-coating process to deposit photocatalytic TiO nanoparticles (P25, Evonik) on a metallic filter material (micro-sieve). The fouling repellent and photocatalytic nanocoatings degraded the water impurities close to the micro-sieve surface before a dense cake layer was formed. This kind of surface activation is, however, restricted to chemically robust materials, excluding polymeric membranes that would be degraded by the induced oxidation process [125]. 

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