Preparation of ZIF-8 Membranes supported on Polymer Hollow Fibers using Microwave-assisted Seeding and Secondary Growth
Moon Joo Lee1, Mohamad Rezi Abdul Hamid1, Jongmyeong Lee3, Ju Sung Kim3, Young Moo Lee3 and Hae-Kwon Jeong*1,2
1Artie
McFerrin Department of Chemical Engineering and 2Department of Materials
Science and Engineering, Texas A&M University, College Station, TX 77843-3122
3Department of Energy Engineering, College of Engineering, Hanyang University, Seoul 133-791, Republic of Korea
* Corresponding author: hjeong7@tamu.edu
Separation of olefin/paraffin mixtures, e.g. propylene/propane, is one of the most challenging separations due to the similarity of their physicochemical properties. Currently, an energy intensive cryo-distillation process is employed. Though energy-efficient membrane-based separation processes are drawing significant interest, no membranes are commercially available for olefin/paraffin separations mainly due to the limitations of current membrane materials and processing methods to fabricate their membranes with large membrane areas.1-3
Zeolitic-imidazolate frameworks (ZIFs), a sub-class of metal-organic frameworks (MOFs) with zeolite topology, are highly crystalline nanoporous materials with aperture sizes of typically less than 5 Å. ZIFs composed of metal ions (typically Zn2+ and Co2+) and imidazole-derived organic linkers,4 have been extensively studied for gas separation applications. Specifically, ZIF-8 is shown very promising as a new membrane material for propylene/propane separation because the effective pore size is in between the size of propylene and propane. While several ZIF-8 membranes showed high propylene/propane separation factors, however, there are critical issues for their commercial applications: 1) high cost of membranes and 2) low productivities. To increase the productivity and to reduce the cost of ZIF-8 membranes, polymeric hollow fibers have been utilized as substrates, but only a few of the resulting ZIF-8 membranes showed promising propylene/propane separation performances.6-9
Herein, we would like to present a microwave-based method to prepare well inter-grown ZIF-8 membranes on polymeric hollow fibers readily. The method is modified based on our previously reported microwave-assisted seeding and secondary growth technique.10 Densely-packed nano-sized ZIF-8 seed crystals were rapidly prepared on either inner or outer surface of hollow fibers under microwave heating. Subsequently, seed crystals were secondarily grown into continuous ZIF-8 films on polyimide hollow fibers. The thickness of the resulting ZIF-8 membranes was much smaller than any ZIF-8 membranes grown on polymer hollow fibers reported, which are several micrometers in thickness. The effects of synthesis parameters and fiber morphologies on the microstructures of ZIF-8 membranes will be discussed. Finally, the gas separation performances of ZIF-8 membranes will be presented.
References and Notes
1 Koros, William J. and Fleming, G.K. (1993) “Membrane-based gas separation”, Journal of Membrane Science, 83, pp l-39
2 Baker RW., (2002) “Future Directions of Membrane Gas Separation Technology” Industrial & Engineering Chemistry Research., 41 (6), pp 1393-1411
3 Tanaka, K., Taguchi, A., Hao, JQ, Kita, H., and Okamoto, K., (1996) “Permeation and separation properties of polyimide membranes to olefins and paraffins”, Journal of Membrane Science, 121, pp 197-207
4 Park KS, Ni Z, Côté AP, et al., (2006) “Exceptional chemical and thermal stability of zeolitic imidazolate frameworks”, Proceedings of the National Academy of Sciences, 103 (27), pp 10186-10191
5 Zhang C, Lively RP, Zhang K, Johnson JR, Karvan O, Koros WJ., (2012) “Unexpected Molecular Sieving Properties of Zeolitic Imidazolate Framework-8”, The Journal of Physical Chemistry Letters., 3 (16), pp 2130-2134.
6 Andrew J. Brown, Nicholas A. Brunelli, Kiwon Eum, Fereshteh Rashidi, J. R. Johnson, William J. Koros, Christopher W. Jones, Sankar Nair, (2014) “Interfacial microfluidic processing of metal-organic framework hollow fiber membranes”, Science, 345, 6192, pp 72-75
7 FernandoCacho-Bailo, SilviaCatalán-Aguirre, MirenEtxeberría-Benavides, Oğuz Karvan, VictorSebastian, CarlosTéllez, JoaquínCoronas (2015) “Metal-organic framework membranes on the inner-side of a polymeric hollow fiber by microfluidic synthesis”, Journal of membrane science, 476, pp 277-285
8 Kiwon Eum, Chen Ma, Ali Rownaghi, Christopher W. Jones, and Sankar Nair (2016) “ZIF‑8 Membranes via Interfacial Microfluidic Processing in Polymeric Hollow Fibers: Efficient Propylene Separation at Elevated Pressures”, ACS Applied materials and interfaces, 8, pp 25337 – 25342
9 Anne M. Marti, Wasala Wickramanayake, Ganpat Dahe, Ali Sekizkardes, Tracy L. Bank, David P. Hopkinson, and Surendar R. Venna (2017) “Continuous Flow Processing of ZIF‑8 Membranes on Polymeric Porous Hollow Fiber Supports for CO2 Capture”, ACS Applied materials and interfaces, 9, pp 5678-5682
10 Kwon HT, Jeong H-K., (2013), “Highly propylene-selective supported zeolite-imidazolate framework (ZIF-8) membranes synthesized by rapid microwave-assisted seeding and secondary growth”, Chemical Communications, 49, pp 3854-3856