Tailoring the Separation Behavior of Hybrid Organosilica Membranes by Adjusting the Structure of the Organic Bridging Group (original) (raw)
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Heterogeneous zeolite-based membranes with polymeric binder were tested for the separation of hydrogen and methane. The separation process was characterized by parameters such as permeability, selectivity, and diffusion flux. The prepared membranes are superior to homogeneous polymeric membranes in permeability and diffusion flux. For H / CH separation 2 4 selectivity equal to 10 was attained.
Truly combining the advantages of polymeric and zeolite membranes for gas separations
Science
Mixed-matrix membranes (MMMs) have been investigated to render energy-intensive separations more efficiently by combining the selectivity and permeability performance, robustness, and nonaging properties of the filler with the easy processing, handling, and scaling up of the polymer. However, truly combining all in one single material has proven very challenging. In this work, we filled a commercial polyimide with ultrahigh loadings of a high–aspect ratio, CO 2 -philic Na-SSZ-39 zeolite with a three-dimensional channel system that precisely separates gas molecules. By carefully designing both zeolite and MMM synthesis, we created a gas-percolation highway across a flexible and aging-resistant (more than 1 year) membrane. The combination of a CO 2 -CH 4 mixed-gas selectivity of ~423 and a CO 2 permeability of ~8300 Barrer outperformed all existing polymer-based membranes and even most zeolite-only membranes.
Microstructural Optimization of a Zeolite Membrane for Organic Vapor Separation
Science, 2003
A seeded growth method for the fabrication of high-permeance, high-separation-factor zeolite (siliceous [Si 96 O 192 ]-MFI) membranes is reported. The method consists of growing the crystals of an oriented seed layer to a well-intergrown film by avoiding events that lead to a loss of preferred orientation, such as twin overgrowths and random nucleation. Organic polycations are used as zeolite crystal shape modifiers to enhance relative growth rates along the desirable out-of-plane direction. The polycrystalline films are thin (ϳ1 micrometer) with single grains extending along the film thickness and with large in-plane grain size (ϳ1 micrometer). The preferred orientation is such that straight channels with an open diameter of ϳ5.5 angstroms run down the membrane thickness. Comparison with previously reported membranes shows that these microstructurally optimized films have superior performance for the separation of organic mixtures with components that have small differences in size and shape, such as xylene isomers.
Small Structures, 2021
Solution-processible amorphous glassy polymers of intrinsic microporosity (PIM) are promising microporous organic materials for membrane-based gas-and liquid separations due to their high surface area and internal free volume, thermal and chemical stability and, most importantly, excellent separation performance. This review provides an overview of the most recent developments in the design and transport properties of novel ladder PIM materials, polyimides of intrinsic microporosity (PIM-PIs), functionalized PIMs and PIM-PIs, PIMs-derived thermally rearranged (TR) and carbon molecular sieve (CMS) membrane materials as well as PIM building block-containing thin-film composite membranes for a wide range of energy-intensive gas-and liquid separations. In less than two decades, PIMs have significantly lifted the performance upper bounds in H2/N2, H2/CH4, O2/N2, CO2/N2, and CO2/CH4 separations. However, PIMs are still limited by their insufficient gas-pair selectivity to be considered as promising materials for challenging industrial separations such as olefin/paraffin separations. An optimum pore size distribution is required to further improve the selectivity of a PIM for a given application. Specific attention is given to the potential use of PIM-based CMS membranes for energy-intensive CO2/CH4, N2/CH4, C2H4/C2H6 and C3H6/C3H8 separations, and thin-film composite membranes containing PIM building blocks for liquid separations.
Journal of Industrial and Engineering Chemistry
Polymeric membrane technology has received extensive attention in the field of gas separation, recently. However, the tradeoff between permeability and selectivity is one of the biggest problems faced by pure polymer membranes, which greatly limits their further application in the chemical and petrochemical industries. To enhance gas separation performances, recent works have focused on improving polymeric membranes selectivity and permeability by fabricating mixed matrix membranes (MMMs). Inorganic zeolite materials distributed in the organic polymer matrix enhance the separation performance of the membranes well beyond the intrinsic properties of the polymer matrix. This concept combines the advantages of both components: high selectivity of zeolite molecular sieve, and mechanical integrity as well as economical processability of the polymeric materials. In this paper gas permeation mechanism through polymeric and zeolitic membranes, material selection for MMMs and their interacti...
Preparation of Zeolite-filled Polymeric Membranes for Pervaporation
Separation processes are widely used in industry since chemical conversions are often in complete. Membrane technique is one of the most attractive separation methods because of its low cost and high selectivity. Zeolitic membranes have gained considerable attention during the last decade. The incorporation of zeolites into rubbery polymers has been shown experimentally to enhance both the permeability and selectivity in pervaporative separation of organic compounds from water. Pervaporation is a promising membrane technique for separation of volatile organic compounds (VOCs) /water mixtures. Polydimethylsiloxane (PDMS) is widely used in different areas as an elastomer or a sealant. In this study, homogeneous PDMS membranes and mixed membranes were prepared by solution casting technique by introducing hydrophilic or hydrophobic zeolites into the polymer matrix. The prepared membranes were tested in a laboratory scale pervaporation experimental setup. The effects of experimental para...
Pervaporation Separation of Ethanol-Water Mixtures by Zeolite-Filled Polymeric Membranes
2009
The incorporation of zeolites into rubbery polymers has been shown experimentally to enhance both the permeability and selectivity in pervaporative separation of organic compounds from water. Pervaporation is a promising membrane technique for separation of volatile organic compounds (VOCs) /water mixtures. Polydimethylsiloxane (PDMS) is widely used in different areas as an elastomer or a sealant. In this study, homogeneous PDMS membranes and mixed membranes were prepared by solution casting technique by introducing hydrophilic or hydrophobic zeolites into the polymer matrix. The prepared membranes were tested in a laboratory scale pervaporation experimental set-up. The effects of experimental parameters such as the type and composition of zeolites on permeation flux and separation factors were investigated. When tested on ethanol/water mixtures, the zeolite-filled membrane of hydrophobic origin was found to give much higher selectivity for ethanol compared to that of hydrophilic na...
Fundamentals and applications of pervaporation through zeolite membranes
Journal of Membrane Science, 2004
Zeolite membranes have uniform, molecular-sized pores, and they separate molecules based on differences in the molecules' adsorption and diffusion properties. Zeolite membranes are thus well suited for separating liquid-phase mixtures by pervaporation, and the first commercial application of zeolite membranes has been for dehydrating organic compounds. Because of the large number of zeolites that can be prepared, zeolite membranes have also been used to remove organic compounds from water, separate organic mixtures, and remove water from acid solutions on the laboratory scale. The fundamental aspects of separations by pervaporation through zeolite membranes are reviewed, and examples of the selectivities and fluxes obtained are presented. Some aspects of these separations are similar to gas-phase separations using zeolite membranes, but feed-side coverages are close to saturation during pervaporation, making competitive adsorption and molecule-molecule interactions more important during multicomponent diffusion. Some of the topics that are discussed include: (1) the use of feed fugacities to predict separation selectivities; (2) the effects of coverage, competitive adsorption, heats of adsorption, molecular sizes, temperature, membrane structure, non-zeolite pores, concentration polarization, and support resistance on transport and separations; (3) the ability of one molecule to slow down or speed up another molecule in the zeolite pores, and (4) the techniques used to measure adsorption and diffusion properties. Several possibilities for improving understanding and effectiveness of pervaporation through zeolite membranes are also suggested.