Influence of vacuum degree on hydrogen permeation through a Pd membrane in different H2/N2 gas mixtures

Palladium (Pd) membranes for industrial applications have gained much interest as of late. The purification of hydrogen through Pd membranes has therefore been proposed as a viable solution to traditional separation methods. Hydrogen permeation can be enhanced when coupled with a vacuum at the permeate side. In this study, the effect of different degrees of vacuum pressures on H2 permeation through a high-permselectivity Pd membrane in different binary gas mixtures was investigated and compared to those without vacuum. Three feed gases containing H2 concentrations of 90, 70, and 50 vol% were used. Hydrogen permeation rates were studied at 320, 350, and 380 °C under vacuum pressures ranging between 0 and −60 kPa. An increase in vacuum degree intensified H2 permeation. However, best performance improvements were observed at lower H2 concentrations, lower temperatures, and also at lower vacuum pressures for all gas mixtures. The highest performance improvement of 88.83% was with the gas mixture containing 50% H2 at 320 °C with a −15 kPa vacuum pressure. Hence, from an efficiency point of view, lower temperatures and vacuum pressures were preferred for all the gas mixtures. Activation Energies were also relatively lower for conditions with a vacuum for all gas mixtures.