A new superior competitor for exceptional propylene/propane separations: ZIF-67 containing mixed matrix membranes
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© 2016 Elsevier B.V. All rights reserved. Recently, the ZIF-67 molecular sieve has emerged as an excellent substitute for the ZIF-8 counterpart due to its potentially high C3H6/C3H8 separation performance. Here, for the first time, we investigated the effect of ZIF-67 in mixed matrix membranes (MMMs) for C3H6/C3H8 separations by integrating them into 6FDA-DAM polymer matrix. The 6FDA-DAM/ZIF-67 (80/20 wt/wt) MMMs achieved an ideal selectivity of 29.9 and a separation factor of 19 under single and equimolar mixed gas conditions, respectively, at 35 °C. The intrinsic C3H6/C3H8 separation performance of ZIF-67 was estimated from our experimental transport results based on the Maxwell model. The calculation demonstrated its superior C3H6/C3H8 selectivity of 251, which is twice of that of ZIF-8, supporting the high molecular sieving capacity of ZIF-67 containing MMMs. Moreover, a thorough investigation on the temperature-dependent gas transports elucidated that the energetic selectivity is a major contributor for the high C3H6/C3H8 diffusivity selectivity in ZIF-67 containing MMMs. However, the minimum aperture size of ZIF-67 (4.5 Å), derived by the cuboid dimensions of C3H6 and C3H8, substantially sacrificed the C3H6/C3H8 entropic selectivity of ZIF-67 containing MMMs. Lastly, the defect-free incorporation of ZIF-67 nanoparticles into 6FDA-DAM polymer matrix effectively retarded physical aging process, maintaining the excellent separation performance of the associated MMMs for 75 days.
author list (cited authors)
An, H., Park, S., Kwon, H. T., Jeong, H., & Lee, J. S.