Influence of temperature on gas transport properties of tetraaminodiphenylsulfone (TADPS) based polybenzimidazoles

Abstract Polybenzimidazoles have been the focus of increasing study due to their good H2/CO2 separation properties and high thermal stability. Gas transport properties of a series of polybenzimidazoles based on a tetraaminodiphenylsulfone (TADPS) monomer have been characterized at temperatures from 35 to 190 °C. Permeability increases with increasing temperature for all gases, and activation energies of permeation increase with increasing gas size with the exception of CO2. CO2 exhibits a lower activation energy of permeation than H2 or He, presumably due to strong sorption effects. Gas separations with TADPS-based PBIs are strongly size selective, with CO2/N2, CO2/CH4, and N2/CH4 selectivities decreasing with increasing temperature. However, H2/CO2 selectivities increase with increasing temperature due to a lower activation energy of permeation for CO2 than for H2. All PBIs tested move toward the upper right on the H2/CO2 upper bound as temperature increases. Estimated diffusivities increase significantly with temperature, indicating high activation energies of diffusion that are consistent with the strongly size-sieving nature of these materials.