Three types of polyimide membranes viz., Matrimid, Kapton and P84, were prepared by solution casting and solvent evaporation method to study the permeation of CO 2 and CH 4 gases. Barrier properties were investigated as a function of feed pressure for pure gases and feed composition for the binary mixtures of CO 2 and CH 4 . Kapton polyimide, prepared by imidization of polyamic acid, showed an increase in permeability, but reduction in selectivity, due to the occurrence of plasticization at higher feed CO 2 concentrations. Matrimid was found to exhibit the highest permeability and was studied in greater detail, due to the feasibility in its scale-up into a hollow fiber modular configuration for commercial application. Matrimid was characterized by Fourier transform infrared (FTIR) spectroscopy and X-ray diffractometry (XRD) to assess the intermolecular interactions and to understand the separation profiles. The effect of feed flow was evaluated by studying the permeation behavior of flat sheet membrane in dead-end operation mode with the hollow fiber module operated in crossflow feed mode. For pure gases, Matrimid hollow fiber membrane exhibited a CO 2 permeability of 12.7 Barrers with a CO 2 /CH 4 selectivity of 40 at the feed pressure of 20 bar. At the same pressure, for binary mixture feed of 5 mol % CO 2 in methane, the module gave a permeability of 7.4 Barrers with a selectivity of 21. The total binary mixture permeability was determined at the feed CO 2 concentrations varying from 0 to 20 mol % to demonstrate the preferential sorption of CO 2 in Matrimid membrane.

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Nanocomposite membranes of poly(vinyl alcohol)-polyaniline (PANI)-coated titanium dioxide (PVA-PANI-TiO 2 ), as well as TiO 2 , cross-linked with glutaraldehyde were tested for their suitability in dehydrating aqueous mixtures of 1,4-dioxane or tetrahydrofuran (THF) by pervaporation (PV). The effect of feed composition and filler loading on PV separation performance was examined. Sorption studies were performed in feed mixtures to assess the extent of interaction between membranes and feed components. The addition of a small amount of nano-sized filler particles into a cross-linked PVA membrane was responsible for an increase in membrane selectivity to water. Among the cross-linked nanocomposite PVA membranes, TiO 2 coated with 0.5 wt% PANI gave higher sorption than other membranes. Sorption of the cross-linked (unfilled) PVA membranes was higher compared to all the nanocomposite membranes. Addition of filler particles reduced the extent of sorption with improved membrane performance.