The effects of gas mixtures on hydrogen permeation through Pd–Ag/V–Ni alloy composite membrane

The effects of gas mixtures on hydrogen permeation through Pd–Ag coated V–Ni composite membranes were investigated by gas permeation technique in the temperature range of 473–673 K at atmospheric pressure. Dense Pd–25Ag layer was sputtered on the V–15Ni alloy film prepared by arc-melting. Hydrogen permeation experiments for as-prepared Pd–Ag/V–Ni composite membrane were carried out with pure hydrogen and different gas mixtures of H2/CO2 and H2/H2S. Long-term permeation tests were performed with the mixture feed of 30%-CO2 in H2 and 11 ppm-H2S in H2. As the percentage of gas impurity increased, the hydrogen permeability decreased. However, the composite membrane did not suffer irreparable damage when exposed to CO2 and the flux value for pure hydrogen was readily recovered by post-treatment in the permeation system. For the H2S impurity, the interaction with the membrane surface was significantly different compared to CO2. Membrane permeability rapidly deteriorated when exposed to a small percentage of H2S. Nevertheless, the membrane does not seem to be damaged as the permeability was fully recovered by longer post-treatment with pure hydrogen.

► Pd–Ag coated V–15Ni composite membranes for hydrogen permeation.
► Both impurities of CO2 and H2S display negative effects on hydrogen permeability through Pd–Ag/V–Ni membrane.
► A trace of H2S severely reduces H2 permeability of the Pd–Ag/V–Ni composite membrane at low temperature (<300 °C).