Exfoliated zeolite Nu-6(2) as filler for 6FDA-based copolyimide mixed matrix membranes

Exfoliated zeolite Nu-6(2)-6FDA-4MPD/6FDA-DABA copolyimide mixed matrix membranes (MMMs) were prepared and used for gas separation. The interaction of the polymer and the filler was investigated for copolyimides with different carboxyl group concentrations and hydrogen bonding was found to take place between the hydroxyl groups on the surface of the zeolite and the carboxylic groups of the polymer. Exfoliated zeolite Nu-6(2) with 300 m2/g surface area was chosen as the filler due to its small pore size, appropriate chemical composition and high aspect ratio. The morphology and nature of the membranes were investigated using chromatography, 1H NMR, ATR-FTIR, TGA, SEM and TEM. Gas separation experiments were performed for H2/CH4 and O2/N2 mixtures. With MMMs containing a 4MPD:DABA molar ratio of 4:1, a maximum value of H2/CH4 selectivity of 37.9 (with 500 Barrer of H2 permeability) was achieved with a 5.3 wt.% of zeolite, while a maximum O2 permeability of 147 Barrer (with a O2/N2 selectivity of 4.0) was obtained with a 9.7 wt.% of zeolite.