Gas permeation characteristics of heterogeneous ODPA-BIS P polyimide membranes at different temperatures

Abstract

Heterogeneous carbon molecular sieves and hypercrosslinked polystyrene microparticles adsorbent-based membranes with a (ODPA-BIS P) polyimide binder were prepared. The effect of adsorbent particles on the gas transport properties of heterogeneous membranes was studied. Permeability, diffusion and solubility coefficients of He, CO2, O-2 and N-2 were estimated for homogeneous and heterogeneous membranes at a feed pressure of 1 atm for different temperatures between 25 and 60 degrees C. It was observed that adsorbent-filled (ODPA-BIS P) polyimide membranes exhibit higher gas permeability in comparison with adsorbent-free membrane, while permselectivity is maintained. The results also showed that the adsorbents enhance significantly gas diffusivity in (ODPA-BIS P) polyimide membrane, whereas the gas solubility is clearly reduced. In both type of heterogeneous membranes, gas permeation and diffusion are thermal activated processes described by the Arrhenius equation, whereas the Sorption process is exothermic. The addition of both type of adsorbents to the (ODPA-BIS P) polyimide membrane increases the activation energy of permeability, this is mainly due to a significant increase of the heat of sorption, because the activation energy for diffusion is slightly decreased.