Hydrogen separation membranes characteristics

E. Kikuchi and S. Uemiya, Preparation of supported thin palladium-silver alloy membranes and their characteristics for hydrogen separation. Gas Sep. Purif. 5 261 (1991). 

To compete successfully with conventional hydrogen separation technologies, such as pressure swing adsorption or polymer membranes, or to be used in a membrane reactor successfully, palladium membranes must possess the following characteristics [4] ... 

The selective layer, that allows separating the hydrogen from the other gases, is strictly connected with the chemical and physical membrane characteristics. 

Maher, G.C., Poulidi, D., Thursfield, A., Pascual, M.J., Jurado, J.R., and Metcalfe, I.S. (2010) Hydrogen permeation characteristics of a SrCeOa-based ceramic separation membrane thermal, aging and surfece-modification effects. Solid State Ionics, 181, 230-235. 

As can be seen from Table 1, the starting membrane exhibits almost pure Knudsen separation characteristics, as can be expected from a state-of-the-art mesoporous y-alumina membrane. The ideal Knudsen permselectivities are H2 N2=3.74, He N2=2.65, H2 CC>2=4.69, which are in agreement with the measured permselectivities. After 43 minutes of CVI in experiment num-ber 1, the hydrogen permeance had decreased to 4.0 10 mol/m sPa, but the permselectivity towards nitrogen had increased to 43, which is far above the Knudsen value. 

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