Modelling of metallic supported PdAg membranes with inter-diffusion barrier

Metallic supported palladium-based membranes require an additional inter-diffusion barrier between the metallic support and the palladium-based selective layer. This porous layer can also function as a smoothening layer to allow for the deposition of a thinner palladium-based layer. The disadvantage of adding this extra layer is that it increases the overall mass transfer resistance of the membrane. In this work, the (relative) resistance of this layer was determined by developing a multi-layer model for the metallic supported palladium-based membrane with inter-diffusion barrier. Permeation experiments and characterizations were performed before and after the deposition of the inter-diffusion barrier and PdAg layer. The experimental data was used to fit the critical parameters for the multi-layer permeation model. The resulting model could then be used to determine the pressure drop induced by each layer of the membrane. The results revealed that the thin PdAg layer causes more than 90% of the total mass transfer resistance of the membrane (100% H 2 , T = 400–500 °C and Δp = 3 bar). To mitigate the contribution of the selective layer on the overall mass transfer resistance of the membrane, implementing a strategy to enhance the membrane permeance is therefore required. This could in the first place be achieved by improving the selective layer deposition methodology, but also by reducing the thickness of the PdAg layer. However, accomplishing such a reduction has significant challenges when considering metallic supports. • The mass transfer resistance of a metallic supported PdAg membrane was assessed. • The transport parameters of each membrane layer were fitted. • The PdAg layer induces more than 92.5% of the mass transfer resistance. • Thinner PdAg layers will significantly reduce the overall mass transfer resistance.