Gas separation properties of mixed-matrix membranes containing porous polyimides fillers

• Porous polyimides were used as fillers in gas separation polyimide membranes.
• Good and rapid dispersion was achieved due to the chemical affinity filler/matrix.
• Porous fillers increased the gas permeability of less permeable matrices.
• For highly permeable matrices the effect of the porous filler was unappreciable.

Two series of mixed-matrix membranes were prepared by adding three organic polymeric fillers into polyimide matrices to explore the effect of the filler on the membrane preparation, properties and gas separation performance.The fillers were two mesoporous polyimides, with specific surface areas of 605 and 715 m2/g, and a microporous one. The polymer matrices used in this study were a commercial polyimide, Matrimid®, and a synthetic polyimide. Due to the chemical affinity between the fillers and the matrices, very good and quick dispersion was achieved in all cases. The spectral characteristics and the thermal properties of the mixtures did not greatly differ from those of the pristine polyimides, as it was checked by FT-IR, TGA and DSC. The gas separation properties of Matrimid® were significantly improved when using the mesoporous fillers because the permeability coefficients were increased up to 3.4 times while the selectivity was maintained or even exceeded. However, when the synthetic matrix, which has much more permeability than Matrimid®, was used, no significant increases in these parameters were observed upon incorporating the porous fillers.

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