Hydrogen permeation measurements were carried out by using an Ag 23 wt%-Pd alloy membrane of
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thickness at temperatures from 773 to 873 K. Contrary to some reported results, hydrogen permeation flux was not affected by the co-existence of
H2O up to 9.5%at 873 and 773 K under non-pressurized conditions. Further addition of
CO2 up to 27.9%,
CH4 up to 6.8%, CO up to 4.6%did not reduce the permeation flux. Similarly, permeation flux was not affected in a pressurized system with
H2O up to 63%, 5%of CO with 30%of
H2O, 20%of
CH4 with 15%of
H2O, under 0.29 MPa pressurization at 873 K. From the hydrogen partial pressure dependence of the permeation flux, the rate determining step was concluded to be the bulk diffusion of H in the membrane under the abovementioned conditions.