286505 Design of ZIF/Polyimide Mixed Matrix Membrane for Olefin/Paraffin Separations

Tuesday, October 30, 2012: 4:55 PM
403 (Convention Center )
Chen Zhang, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia and William J. Koros, School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA

<>C2~C4 olefins are consumed as feedstocks to produce a variety of significant chemicals. Membrane separations have been emerging as more energy-efficient alternatives to fractional distillation to enrich olefin from olefin/paraffin mixtures. The development of high-performance membrane materials has been the key to promote membrane separations as practical approaches for large-scale industrial gas separations.

Mixed matrix membranes, formed by dispersing molecular sieve particles/platelets in polymer matrices, are promising approaches for gas/vapor separations that combine the ease of processing polymers with the superior separation performance of molecular sieves. The selection of molecular sieving phase and polymer phase is crucial to fabrication of mixed matrix membranes with intact polymer-sieve adhesion and favorable gas transport properties. Zeolitic imidazolate frameworks (ZIFs) are microporous crystalline solids with zeolite or zeolite-like topologies. The favorable adsorption and molecular sieving properties of ZIFs enable the possibility of being used as selective adsorbents as well as membrane materials.

Our study suggests that with appropriate choice of ZIF and polymer, enhanced and industrially attractive permeability and permselectivity can be simultaneously obtained in the ZIF/polymer mixed matrix membrane. ZIF-8/6FDA-DAM mixed matrix dense films were fabricated with hydrophobic ZIF-8 as the molecular sieving phase and a high performance polyimide 6FDA-DAM as the polymer phase.  Permeation properties of the neat 6FDA-DAM dense film and ZIF-8/6FDA-DAM mixed matrix dense films were studied with pure propylene (C3H6) and propane (C3H8) feeds as well as a 50/50 (vol %) C3H6/C3H8 mixture feed. Pure gas permeation showed significantly enhanced mixed matrix ZIF-8/6FDA-DAM membrane C3H6/C3H8 separation performance compared to the pure 6FDA-DAM membrane. A C3H6 permeability of 56 Barrers and C3H6/C3H8 ideal selectivity of 31 was found in ZIF-8/6FDA-DAM mixed matrix membrane with 48 wt % ZIF-8 loading. These results are 258 % and 150 % higher than the pure 6FDA-DAM membrane, respectively for permeability and selectivity. Mixed gas permeation also verified that selectivity enhancements were achievable in mixed gas environment by ZIF-8.


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See more of this Session: Membranes for Gas Separations II
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