New membrane based on Pd-SiO2 catalyst on PSS/NaX for hydrogen separation: Design and optimization

Palladium (Pd)-SiO2 catalysts coated porous stainless steel (PSS)/NaX nanozeolites membranes were prepared via the sol–gel method and their application were evaluated for hydrogen separation. The hydrothermally synthesized NaX nanozeolite was coated by vacuum-assisted method on the PSS surface. The morphology of membranes were characterized using SEM analysis. The Box-Behnken design was used to determination the relationship between the variable input synthesis and process parameters such as: NaX content (0.5-1.5 g), Pd percentage (5-15 %), pressure difference (2-4 bar) and temperature (350-450 ˚C) and the corresponding output parameters including: hydrogen permeation flux, HPF and H2/N2 ideal gas selectivity, IGS. By optimization of the parameters, the experimental maximum hydrogen permeation flux and ideal selectivity were found to be 1.2×10-7 and 720 respectively. Moreover, the performance of the fabricated membrane were investigated for different mixtures of H2/N2 in the optimum condition. The results indicated that hydrogen fluxes and H2/N2 ideal selectivity were decreased by increasing in N2 content. The obtained results suggest that the simultaneous optimization of synthetic and process parameters could be effective for the performance enhancement of Pd-based membranes for hydrogen separation.