Surface modification of polyimide membranes by diamines for H2 and CO2 separation

Abstract

The separation of H2/CO2 is technologically important to produce the next generation fuel source, hydrogen, from synthesis gas. However, the separation efficiency achieved by polymeric membranes is usually very low because of both unfavourable diffusivity selectivity and solubility selectivity between H2 and CO2. A series of novel diamino-modified polyimides has been discovered to enhance the separation capability of polyimide membranes especially for H2 and CO 2 separation. Both pure gas and mixed gas tests have been conducted. The ideal H2/CO2 selectivity in pure gas tests is 101, which is far superior to other polymeric membranes and is well above the Robeson's upper-bound curve. Mixed gas tests show an ideal selectivity of 42 for the propane-1,3-diamine-modified polyimide. The lower selectivity is a result of the sorption competition between H2 and the highly condensable CO2 molecules. However, both pure gas and mixed gas data are better than other polymeric membranes and above the Robeson's upper-bound curve. It is evident that the proposed modification methods can alter the physicochemical structure of polyimide membranes with superior separation performance for H 2 and CO2 separation © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.