(695d) Highly Permeable Polyimide Membranes by Simultaneously Cavities Formation and Cross-Linking for Gas Separation

Aromatic polyimides have been used widely in gas separation applications due to their excellent thermal and mechanical properties. In order to minimize the foot print of membrane systems, high permeability is always desired for membrane materials. Although polyimide structure could be tailored successfully with higher permeability, it is also companied with sacrifice of gas selectivity. In the present work, the novel polyimide membranes have been achieved by heat treatment of polyimide membranes comprising thermal liable cyclodextrin units. During the high temperature treatment, the decomposition of cyclodextrin will produce various small molecular gases to be released and leave a lot of connected cavities in the membrane matrix. In addition, the dimension of channels which connect to difference cavities also could be tuned by following thermal induced cross-linking reaction, so that the resulted polyimide membranes could be applied for Propane/Propylene, CO2/CH4, CO2/N2 and O2/N2 et al, based on the final channel size. The separation performance of above mentioned gas pairs all overcome the trade-off line for the polymeric membranes. For example, the membranes thermally treated under 425oC have shown the excellent natural gas separation performance of a 100 fold increment in CO2 permeability (above 4000 barrer), while maintain the CO2/CH4 selectivity at the accepted level. In addition, the thermal treated polyimide membranes show excellent anti-plasticization performance due to the cross-linked structure.