Title: Enhancing the propylene/propane separation performances of ZIF-8 membranes by post-synthetic surface polymerization
Zeolitic-imidazole framework-8 (ZIF-8) membranes have shown exceptional propylene/propane separation performances. Their commercial applications have, however, been impeded by several challenges. One such challenge is the difficulty of managing microstructural defects ( i.e. , grain boundary defects) in a consistent manner, leading to poor membrane performances and ultimately to a reproducibility issue. Herein, we introduce a new effective strategy to seal the microstructural defects of polycrystalline ZIF-8 membranes using post-synthetic surface polymerization which consists of two steps: (1) introduction of initiator ligands on the membrane surface by post-synthetic ligand exchange and (2) in situ polymerization of poly(methyl methacrylate) (PMMA) via atom transfer radical polymerization. The ZIF-8 membranes were fully covered with ultra-thin PMMA layers of sub-10 nm thickness, increasing the propylene/propane separation factor from ∼60 to ∼106 with unexpectedly increased propylene permeance, effectively improving the membrane reproducibility. The enhanced separation properties of the PMMA-coated ZIF-8 membranes were attributed to the ultra-thin PMMA layers as well as to the possible facilitated propylene transport by Cu ions in the PMMA layers. more »« less
Lee, Dennis T.; Corkery, Peter; Park, Sunghwan; Jeong, Hae-Kwon; Tsapatsis, Michael(
, Annual Review of Chemical and Biomolecular Engineering)
In the last decade, zeolitic imidazolate frameworks (ZIFs) have been studied extensively for their potential as selective separation membranes. In this review, we highlight unique structural properties of ZIFs that allow them to achieve certain important separations, like that of propylene from propane, and summarize the state of the art in ZIF thin-film deposition on porous substrates and their modification by postsynthesis treatments. We also review the reported membrane performance for representative membrane synthesis approaches and attempt to rank the synthesis methods with respect to potential for scalability. To compare the dependence of membrane performance on membrane synthesis methods and operating conditions, we map out fluxes and separation factors of selected ZIF-8 membranes for propylene/propane separation. Finally, we provide future directions considering the importance of further improvements in scalability, cost effectiveness, and stable performance under industrially relevant conditions.
In this article, zeolitic-imidazolate framework-8 (ZIF-8) and its mixed metal CoZn-ZIF-8 were synthesized via a rapid microwave method. The products were characterized by Raman spectroscopy, XPS, XRD, EDX, TEM, NanoSEM, TGA, and DSC. The gas adsorption properties of samples were determined using C 3 and C 4 hydrocarbons, including propane, propylene, isobutane and n -butane at a temperature of 25 °C. The adsorption equilibrium and kinetics of these gases on various ZIFs were studied. It was noted that ZIF-8 and mixed metal CoZn-ZIF-8 samples start to adsorb these gases after certain pressures which are believed to result in the opening of their nano-gates ( i.e. , 6-membered rings) to allow the entry of gas molecules. The nanogate opening pressure value ( p 0 ) for each ZIF towards different gases was determined by fitting adsorption equilibrium data against a modified form of the Langmuir adsorption isotherm model. It was observed that the value of p 0 differs significantly for each gas and to various extents for various ZIFs. Therefore, it is possible that the distinct values of p 0 afford a unique technique to separate and purify these gases at the industrial scale. The overall mass transfer coefficient values of the adsorption process were also investigated.
Despite the high potential of zeolite MFI membranes for the separation of important hydrocarbons, their impact on industrial hydrocarbon separations has been limited by challenges in scalable fabrication methods and use of high‐cost membrane supports. Here a one‐step method for fabrication of highly selective and thin (<1 µm) MFI zeolite membranes on low‐cost α‐alumina hollow fiber supports is demonstrated. This is enabled by use of a highly concentrated silicate precursor gel containing MFI nanocrystals that induces a compact membrane layer at the support surface in a single‐step membrane synthesis. These one‐step crystallized MFI hollow fiber membranes show excellent characteristics for butane isomer separation (n‐butane permeance > 10−7mol m−2s−1Pa−1andn‐butane/i‐butane separation factors > 50 ), as well as for removal of natural gas liquids (butane, propane, and ethane) from methane at elevated feed pressures up to 9 bar. It is further demonstrated that the scalability of the current strategy by successful fabrication of a high‐quality ten‐membrane module in a single synthesis batch.
Wang, Tongshuai; Liang, Siwei; Qi, Zhen; Biener, Monika; Voisin, Thomas; Hammons, Joshua A.; Tran, Ich C.; Worsley, Marcus A.; Braun, Tom; Wang, Y. Morris; et al(
, Materials Horizons)
Multi-functional membranes with high permeance and selectivity that can mimic nature's designs have tremendous industrial and bio-medical applications. Here, we report a novel concept of a 3D nanometer (nm)-thin membrane that can overcome the shortcomings of conventional membrane structures. Our 3D membrane is composed of two three-dimensionally interwoven channels that are separated by a continuous nm-thin amorphous TiO 2 layer. This 3D architecture dramatically increases the surface area by 6000 times, coupled with an ultra-short diffusion distance through the 2 – 4 nm-thin selective layer that allows for ultrafast gas and water transport, ∼900 l m −2 h −1 bar −1 . The 3D membrane also exhibits a very high ion rejection ( R ∼ 100% for potassium ferricyanide) due to the combined size- and charge-based exclusion mechanisms. The combination of high ion rejection and ultrafast permeation makes our 3DM superior to the state-of-the-art high-flux membranes whose performances are limited by the flux-rejection tradeoff. Furthermore, its ultimate Li + selectivity over polysulfide or gas can potentially solve major technical challenges in energy storage applications, such as lithium – sulfur or lithium – O 2 batteries.
Kaner, Papatya; Dudchenko, Alexander V.; Mauter, Meagan S.; Asatekin, Ayse(
, Journal of Materials Chemistry A)
Membrane separations are simple to operate, scalable, versatile, and energy efficient, but their broader use is curtailed by fouling or performance decline due to feed component depositing on the membrane surface. Surface functionalization with groups such as zwitterions can mitigate the adsorption of organic compounds, thus limiting fouling. This can be achieved by using surface-segregating copolymer additives during membrane manufacture, but there is a need for better understanding of how the polymer structure and architecture affect the effectiveness of these additives in improving membrane performance. In this study, we aim to explore the impact of the architecture of zwitterionic copolymer additives for polyvinylidene fluoride (PVDF)-based membranes in fouling mitigation and ionic strength response. We prepared membranes from blends of PVDF with zwitterionic (ZI) copolymers with two different architectures, random and comb-shaped. As the random copolymer, we used poly(methyl methacrylate- random- sulfobetaine-2-vinyl pyridine) (PMMA- r -SB2VP) synthesized by free radical polymerization. The comb-shaped copolymer was synthesized by grafting SB2VP side-chains from a PVDF backbone by controlled radical polymerization. Membranes were fabricated from PVDF-copolymer blends containing up to 5 wt% ZI copolymer. Compared to the additive-free PVDF membrane, water permeance increased five-fold with 5 wt% addition of either copolymer. The comb copolymer additive led to better resistance to fouling by a saline oil-in-water emulsion and to simulated protein adsorption in Atomic Force Microscopy (AFM) force measurements. The additive architecture had a significant influence on how membranes respond to changes in feed salinity, which is known to affect intra- and inter-molecular interactions in zwitterionic polymers. The random copolymer containing membrane showed a small and mostly reversible decrease in its permeance with salinity. In contrast, the comb copolymer-containing membrane underwent a conformational reorganization in saline solutions that leads to an irreversible permeance decrease, increased zwitterionic group content on the membrane surface, and smoother surface topography. The higher mobility of the zwitterionic groups in the comb-shaped architecture facilitates reorganization of the zwitterionic side-chains in response to ionic strength. Overall, this study establishes a new approach for developing highly fouling resistant membranes and defines how the architecture of a zwitterionic copolymer additive impacts the ionic strength response and fouling resistance of the membrane.
Park, Sunghwan, Cho, Kie Yong, and Jeong, Hae-Kwon. Enhancing the propylene/propane separation performances of ZIF-8 membranes by post-synthetic surface polymerization. Retrieved from https://par.nsf.gov/biblio/10385279. Journal of Materials Chemistry A 10.4 Web. doi:10.1039/d1ta08705c.
Park, Sunghwan, Cho, Kie Yong, & Jeong, Hae-Kwon. Enhancing the propylene/propane separation performances of ZIF-8 membranes by post-synthetic surface polymerization. Journal of Materials Chemistry A, 10 (4). Retrieved from https://par.nsf.gov/biblio/10385279. https://doi.org/10.1039/d1ta08705c
Park, Sunghwan, Cho, Kie Yong, and Jeong, Hae-Kwon.
"Enhancing the propylene/propane separation performances of ZIF-8 membranes by post-synthetic surface polymerization". Journal of Materials Chemistry A 10 (4). Country unknown/Code not available. https://doi.org/10.1039/d1ta08705c.https://par.nsf.gov/biblio/10385279.
@article{osti_10385279,
place = {Country unknown/Code not available},
title = {Enhancing the propylene/propane separation performances of ZIF-8 membranes by post-synthetic surface polymerization},
url = {https://par.nsf.gov/biblio/10385279},
DOI = {10.1039/d1ta08705c},
abstractNote = {Zeolitic-imidazole framework-8 (ZIF-8) membranes have shown exceptional propylene/propane separation performances. Their commercial applications have, however, been impeded by several challenges. One such challenge is the difficulty of managing microstructural defects ( i.e. , grain boundary defects) in a consistent manner, leading to poor membrane performances and ultimately to a reproducibility issue. Herein, we introduce a new effective strategy to seal the microstructural defects of polycrystalline ZIF-8 membranes using post-synthetic surface polymerization which consists of two steps: (1) introduction of initiator ligands on the membrane surface by post-synthetic ligand exchange and (2) in situ polymerization of poly(methyl methacrylate) (PMMA) via atom transfer radical polymerization. The ZIF-8 membranes were fully covered with ultra-thin PMMA layers of sub-10 nm thickness, increasing the propylene/propane separation factor from ∼60 to ∼106 with unexpectedly increased propylene permeance, effectively improving the membrane reproducibility. The enhanced separation properties of the PMMA-coated ZIF-8 membranes were attributed to the ultra-thin PMMA layers as well as to the possible facilitated propylene transport by Cu ions in the PMMA layers.},
journal = {Journal of Materials Chemistry A},
volume = {10},
number = {4},
author = {Park, Sunghwan and Cho, Kie Yong and Jeong, Hae-Kwon},
}
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