Hydrogen Permeation Performance Comparison among Palladium and Other Membranes with Different Permeation Laws

Abstract

Palladium membranes are useful to produce pure hydrogen by allowing only hydrogen to pass through. However, palladium, a platinum group metal, is limited in resources and expensive. Therefore, alternative membranes are intensively being developed including other metal membranes, porous ceramic membranes, etc. Comparison among them is essential in the development but difficult because these membranes obey different permeation laws. To overcome this difficulty, pressure-dependent permeance is applied to membranes of different thicknesses and different materials: pure palladium membranes 50 μm and 200 μm thick, a pure niobium membrane, and a silica membrane without pressure dependence in permeance. The result demonstrates that pressure-dependent permeance can describe hydrogen permeation flux more precisely than the conventional square-root law and that it enables comparison among membranes with different thicknesses made of different materials. Suitable operating pressure conditions for each membrane are proposed according to the comparison.