Versatile and Resistant Electroless Pore-Plated Pd-Membranes for H₂-Separation: Morphology and Performance of Internal Layers in PSS Tubes

Abstract

Pd-membranes are interesting in multiple ultra-pure hydrogen production processes, although they can suffer inhibition by certain species or abrasion under fluidization conditions in membrane reactors, thus requiring additional protective layers to ensure long and stable operation. The ability to incorporate intermediate and palladium films with enough adherence on both external and internal surfaces of tubular porous supports becomes crucial to minimize their complexity and cost. This study addresses the incorporation of CeO2 and Pd films onto the internal side of PSS tubes for applications in which further protection could be required. The membranes so prepared, with a Pd-thickness around 12–15 μm, show an excellent mechanical resistance and similar performance to those prepared on the external surface. A good fit to Sieverts’ law with an H2-permeance of 4.571 × 10−3 mol m−2 s−1 Pa−0.5 at 400 °C, activation energy around 15.031 kJ mol−1, and complete ideal perm-selectivity was observed. The permeate fluxes reached in H2 mixtures with N2, He, or CO2 decreased with dilution and temperature due to the inherent concentration-polarization. The presence of CO in mixtures provoked a higher decrease because of a further inhibition effect. However, the original flux was completely recovered after feeding again with pure hydrogen, maintaining stable operation for at least 1000 h.

Keywords

• palladium
• electroless plating
• composite membrane
• intermediate layer
• PSS
• internal surface