Effect of dry/wet-phase inversion method on fabricating polyetherimide-derived CMS membrane for H2/N2 separation

The research investigated carbon molecular sieve (CMS) membranes through the dry/wet-phase inversion method from the casting polyetherimide (PEI) on alumina support for hydrogen separation. Different coating techniques such as dry method (slide casting followed by drying under vacuum; and spin coating followed by drying under vacuum); and wet method (spin coating and then later kept in an isopropyl alcohol (IPA)/water coagulating bath) at different pyrolysis temperatures of 550, 600, 650 °C min−1 were also investigated.The membranes were extensively characterized by field emission scanning electron microscopy (FE-SEM) for surface morphology studies and thermo gravimetric analysis (TGA) for thermal properties. The best performance was obtained from CMS membranes fabricated with the dry-phase method (slide casting/vacuum) and pyrolysis at 600 °C, where the H2/N2 permselectivity was 16.2. In contrast with the wet-phase, the increase in gas permselectivity by the dry-phase (slide casting/vacuum) was believed to be due to the quick solidification that prevents rearrangement of polymer aggregates and coalescence of the nascent voids formed due to the spinodal or nucleation growth.