Copolyimide mixed matrix membranes with oriented microporous titanosilicate JDF-L1 sheet particles

JDF-L1 is a microporous titanosilicate exhibiting a layer structure with pore size of about 3 Å. It is consequently an attractive material to separate H2-containing mixtures. This is the reason why JDF-L1, after disaggregation by means of hexadecyltrimethylammonium surfactant, has been combined with a carboxyl group containing copolyimide (6FDA-4MPD/6FDA-DABA 4:1) to produce mixed matrix membranes, which were applied to the separation of H2/CH4 and O2/N2 mixtures. Additionally, due to the sheet growth habit of JDF-L1 crystals, a preferential horizontal orientation of the JDF-L1 filler particles dispersed into the polymer was expected. This preferential orientation, which was achieved when the polymer solution concentration used during the membrane casting process was relatively low, has been studied by optical and electronic microscopy, X-ray diffraction and polarized Raman spectroscopy. A quantitative analysis was carried out applying Cussler's model for mixed matrix membranes with oriented flakes.

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► Due to the sheet growth habit of JDF-L1 crystals, a preferential horizontal orientation of the JDF-L1 filler particles dispersed into the mixed matrix membrane was achieved.
► The H2/CH4 selectivity increased with higher amounts of filler material from 21.3 for the pure polymer to 35.6 in the MMM.
► The O2/N2 selectivity was not affected by the filler but a stronger barrier effect was observed.