• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.481-487
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• 2010

Recently membrane-based gas separation has attracted a great deal of research interests due to the growing demands on greener technologies. Current membrane-based gas separation is dominant by polymer membranes and limited mostly to non-condensable gases even though condensable gases such hydrocarbon isomers are much more attractive. This is primarily due to the limitations of polymer materials. Zeolites and their composites with polymer can offer alternative to current polymeric membranes owing to their superior separation and chemical/thermal properties. This review is intended to provide a brief overview on zeolite and zeolite/polymer composite membranes for gas separation applications.

• Membrane Journal
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• v.27 no.1
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• pp.1-42
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• 2017

Metal-organic frameworks (MOFs) are nanoporous materials that consist of organic and inorganic moieties, with well-defined crystalline lattices and pore structures. With a judicious choice of organic linkers present in the MOFs with different sizes and chemical groups, MOFs exhibit a wide variety of pore sizes and chemical/physical properties. This makes MOFs extremely attractive as novel membrane materials for gas separation applications. However, the synthesis of high-quality MOF thin films and membranes is quite challenging due to difficulties in controlling the heterogeneous nucleation/growth and achieving strong attachment of films on porous supports. Microwave-based synthesis technology has made tremendous progress in the last two decades and has been utilized to overcome some of these challenges associated with MOF membrane fabrication. The advantages of microwaves as opposed to conventional synthesis techniques for MOFs include shorter synthesis times, ability to achieve unique and complex structures and crystal size reductions. Here, we review the recent progress on the synthesis of MOF thin films and membranes with an emphasis on how microwaves have been utilized in the synthesis, improved properties achieved and gas separation performance of these films and membranes.

• Proceedings of the Membrane Society of Korea Conference
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• 1994.04a
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• pp.51-52
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• 1994

High permeability, selectivity and stability are the basic properties also required for membrane gas separations. The $CO_2$ separation by liquid membranes has been developed as a new technique to improve the permeability and selectivity of polymeric membranes. Sirkar et al.(1) have atlempted the hollow-fiber contained liquid membrane technique under four different operational modes, and permeation models have been proposed for all modes. Compared to a conventional liquid membrane, the diffusional resistance decreased by the work of Teramoto et al.(2), who referred to a moving liquid membrane. Recently, Shelekhin and Beckman (3) considered the possibility of combining absorption and membrane separation processes in one integrated system called a membrane absorber. Their analysis could be predicted effectively the performance of flat sheet membrane, however, there are restrictions for considering a flow effect. The gas absorption rate is determined by both an interfacial area and a mass transfer coefficient. It can be easily understood that although the mass transfer coefficients in hollow fiber modules are smaller than in conventional contactors, the substantial increase of the interfacial area can result in a more efficient absorber (4). In order to predict a performance in the general system of hollow-fiber membrane absorber, a gas-liquid mass transfor should be investigated inevitably. The influence of liquid velocity on both a mass transfer and a performance will be described, and then compared with experimental results. A present study is attempted to provide the fundamentals for understanding aspects of promising a hollow-fiber membrane absorber.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1023-1028
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• 2014

Protonated caffeine ($CH^+$) and glucosamine ($GH^+$) overlapped in an analysis with ion mobility spectrometryquadrupole mass spectrometry. Ethyl lactate vapor (L) at different concentrations from 0 to 22 mmol $m^{-3}$ was added as a buffer gas modifier to separate these signals. The drift times of $CH^+$ and $GH^+$ increased with L concentration. The drift time increase was associated to clustering equilibria of $CH^+$ and $GH^+$ with one molecule of L and the equilibrium of $GH^+$ was more displaced to the formation of $GLH^+$ than that of $GLH^+$. $GH^+$ clustered more to L than $CH^+$ because $GLH^+$ formed more stable hydrogen bonds (26.30 kcal/mol) than $GLH^+$ (24.66 kcal/mol) and the positive charge in $GH^+$ was more sterically accessible than in $CH^+$. The aim of this work was to use theoretical calculations to guide the selection of a buffer gas modifier for IMS separations of two compounds that overlap in the mobility spectra and predict this separation, simplifying that empirical process.

• Membrane Journal
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• v.30 no.6
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• pp.450-459
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• 2020

Membrane-based separations have the potential to reduce energy consumption and environmental impact associated with conventional processes. However, many researches have been done to develop new membrane materials with greater selectivity and permeability. Here, we report highly selective membranes by introducing bulky ethyl substituents into the polyimide. The ethyl group in the ortho position to the imide nitrogen interferes the chain packing and increases chain stiffness and the distance between the polymer chains. The polyimide membranes were synthesized from various aromatic dianhydrides and 4,4'-methylenebis(2,6-diethylaniline) (MDEA). The synthesized membranes with increased gas diffusion length due to bulky substituents showed improved propylene/propane (C3H6/C3H8) selectivity. Single gas permeation showed high C3H6/C3H8 selectivity of 14.5, and C3H6 permeability of 7.0 barrer was found in MDEA-polyimide. Mixed-gas permeation results also demonstrate that MDEA-polyimide can achieve high selectivity in mixed-gas environment. Furthermore, this approach could significantly increase the feasibility of economic propylene separation compared to conventional polymer materials.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.848-852
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• 2005

The two important problems to solve before the industrialization of the iodine-sulfur (IS) process are (i) methods to separate $H_2SO_4$ and HI and (ii) to maintain constant components. However undesired reaction was occurred and $H_2S$ and S were formed during the Bunsen reaction. It is necessary to forbid the undesired reaction between $H_2SO_4$ and HI by separating the two acids into two different layers. The experimental conditions for the present study was chosen in such a way that to achieve the separation between the two acids and minimize the side reaction. $H_2S$ formation was reduced and the separations of the two liquids were occurred at $H_2O$ molar fraction from 0.86 to 0.909. But the separations between the two liquids were not occurred at $H_2O$ molar fraction more than 0.92.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.27-30
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• 1999

Poly(phenylene oxide)s were used to prepare flat, integrally skinned self-supporthed asymmetric membranes by dry-wet phase separption. The intrinsic ideal gas selectivity of poly- (2,6-dimethy-1,4-phenylene oxide) (PMPO) was retained in the membranes, and improved by a coating with silicone rubber. Polymers of the same class were coated of UF supports with a silicon rubber gutter layer, yielding composite membranes with high flux but lower selectivity. The effect of th glutaraldehyde cross-linking of sodium alginate (SA) membranes on the mobility of water and ethanol has been studied with pfg nmr. Crosslinking reduces water self-diffusion, and does not seem to be stable on the timescale of weeks.

• Journal of environmental and Sanitary engineering
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• v.16 no.1
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• pp.61-65
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• 2001

To review mass transfer trays from a process of view, the dependence of efficiency in loading ranges and maximum loadings with an acceptable efficiency of traditional tray have to be known. It is reported about the performance of the metallic Dualflex, relatively new high performance packing. Absorption, desorption and rectification tests as well as pressure drop and maximum capacity are concerned, indicate the superiority of the Dualflex over the general packing of comparable, main process. The process engineering characteristics show that Dualflex can be applied for all mass transfer precesses and it is to be recommended especially for those high capacity separations which requite allow low pressure drop because of the thermal sensibility of the product or because of the need of energy saving.

• Korean Membrane Journal
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• v.1 no.1
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• pp.50-58
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• 1999

Symmetric asymmetric and composite perfluoropolymer membranes made with HYFLON AD have been prepared and evaluated. Porous and non porous symmetric membranes have been prepared by solvent evaporation with various processing conditions. Non-contact atomic force microscopy (AFM) was used to investigate the membrane morphology in air. Analysis of the images gave quantitative imformation on the surface pore strcture in particular on the pore size distributin. Possible useful uses of porous membranes are envisaged in the field of gas-liquid separations such as membrane contactors (MSc) Molecular Dynamics(MD) simulations structure of HYFLON AD 60X copolymer supporting these results are also reported. Amorphous perfluoropolymer membranes appears to be ideal other than in MCs when separation processes have to be performed in hostile environments i.e. high temperatures and aggressive non-aqueous media such as chemicals and solvents. In these cases HYFLON AD mem-branes can exploit the outstanding resistance of perfluoropolymers.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.124-127
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• 2004

Many studies have examined the use of liquid membranes for various processes such as separations of isomers, gas, organic mixtures, and removal of specific ions. It has been reported that liquid membranes show high selectivity. However, it is difficult to apply the liquid membranes to practical industrial processes because of the low stability of the liquid membranes.(omitted)