HYDROGEN PERMEATION THROUGH PALLADIUM ALLOY MEMBRANES IN MIXTURE GASES OF 10-PERCENT NITROGEN AND AMMONIA IN THE HYDROGEN

The effects of poisoning by nitrogen and ammonia in the hydrogen gas o n hydrogen permeation through Pd-rich Pd-Y(Gd)-Ag and Pd-Y-In(Sn, Pb) alloy series have been investigated using mixture gases of both H-2 10% N-2 and H-2 + 10% NH3 at temperatures between 523 and 723 K, and i nput gas pressures between 400 and 667 kPa. In addition to these alloy series, pure Pd, some Pd-Ag based alloys and Pd-8.0 at.% Y(Gd) alloy were examined for comparison. The hydrogen permeabilities under both t he mixtures are reduced more or less compared to that under pure hydro gen gas, especially the reduction in permeability through the Pd-8.0 a t.% Gd and Pd-Y(Gd)-Ag alloy series, which have higher permeability un der pure hydrogen gas, is larger than that for the Pd-Y-In(Sn, Pb) all oy series. The reduction rates, however, in these alloys are smaller t han those under mixture gases of H-2 + 10% CO(CH4 C2H4) examined previ ously. Under the N-2-mixture gas the reduction in permeability for the Pd-Y(Gd)-Ag, Pd-8.0 at.% Y(Gd) and Pd-24.0 at.% Ag alloys increases r elatively largely with an increase of temperature, while under the NH3 -mixture gas, the reduction for all the alloys except for Pd-24.0 at.% Ag alloy have a tendency to decrease with increasing temperature. Wit h respect to the temperature dependence of the reduction in hydrogen p ermeability, the Pd97.5-xYxIn2.5 (x = 6.0), Pd97.5-xYxSn2.5 (x = 5.8), Pd-8.0 at.% Y and ''B'' alloys have relatively high resistance to the poisoning by N-2 and NH3 in the hydrogen, but the resistance of Pd-8. 0 at.% Y alloy is limited to only the NH3-mixture. The reduction in hy drogen permeability through the alloys under both the mixtures can be attributed to the decrease in effective area due to the adsorption of the impurity gases for the dissociation process of hydrogen molecules. (C) 1997 International Association for Hydrogen Energy.