Hydrogen permeation through palladium-based alloy membranes in mixtures of 10% methane and ethylene in the hydrogen

The effects of poisoning by methane and ethylene in hydrogen gas on the hydrogen permeation through Pd-rich Pd-Y(Gd)-Ag and Pd-Y-In(Sn,Pb) ternary solid solution alloys have been investigated using mixture gases of H-2 + 10% CH4 and H-2 + 10% C2H4 at temperatures between 523 and 723 K and input gas pressures between 400 and 667 kPa. In addition to these alloys, pure Pd, some Pd-Ag based alloys and Pd-8.0 at.% Y(Gd) alloys were also examined for comparison. The hydrogen permeabilities in these alloys under both the mixtures are reduced compared to that under pure hydrogen gas. The reduction in permeability through Pd-8.0 at. % Gd and Pd-Y(Gd)-Ag alloy series is larger than that for Pd-Y-In(Sn,Pb) alloys, and the reduction for the CH4-mixture gas is larger than that for the C2H4-mixture. In the former mixture gas, the reduction in permeability increases with an increase of temperature, although for pure Pd it decreases, while in the latter mixture gas the reduction decreases with increasing temperature, except for Pd-8.0 at.% Y alloy. The XPS analysis on the alloy surfaces before and after permeation experiments showed that the intensity of the C-1s spectrum observed for all the alloys decreased with an increase of Ar+ sputter etching time; after 5 min sputtering the peak intensity returned to that of the initial sample state. No spectra due to any carbides nor carbon deposition were observed. Thus, the reduction in hydrogen permeability through the alloys under both mixture gases can be attributed to the decrease in effective area due to the adsorption of the impurity gases for the dissociation process of hydrogen molecules. Copyright (C) 1996 International Association for Hydrogen Energy