Hydrogen permeation through palladium alloy membranes in mixture gases of 10% nitrogen and ammonia in the hydrogen

Abstract

The effects of poisoning by nitrogen and ammonia in the hydrogen gas on 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% NH 3 at temperatures between 523 and 723 K, and input 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 the mixtures are reduced more or less compared to that under pure hydrogen gas, especially the reduction in permeability through the Pd-8.0 at.% Gd and Pd-Y(Gd)-Ag alloy series, which have higher permeability under pure hydrogen gas, is larger than that for the Pd-Y-In(Sn, Pb) alloy series. The reduction rates, however, in these alloys are smaller than those under mixture gases of H 2 + 10% CO(CH 4, C 2H 4) examined previously. 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 relatively largely with an increase of temperature, while under the NH 3-mixture gas, the reduction for all the alloys except for Pd-24.0 at.% Ag alloy have a tendency to decrease with increasing temperature. With respect to the temperature dependence of the reduction in hydrogen permeability, the Pd 97.5− x Y x In 2.5 ( x = 6.0), Pd 97.5− x Y x Sn 2.5 ( x = 5.8), Pd-8.0 at.% Y and “B” alloys have relatively high resistance to the poisoning by N 2 and NH 3 in the hydrogen, but the resistance of Pd-8.0 at.% Y alloy is limited to only the NH 3-mixture. The reduction in hydrogen 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.