• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.250-255
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• 2011

In this study, by using the polymeric membrane separation process, the $CO_{2}/CH_{4}$ separation and $H_{2}S$ removal from biogas were performed in order to $CH_{4}$ purification and enrichment for the fuel cell energy source application. Fibers were spun by dry/wet phase inversion method. The module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy(SEM) studies showed that the produced fibers typically had an asymmetric structure; a dense top layer supported by a porous, sponge substructure. The permeance of $CO_{2}$ and $CO_{2}/CH_{4}$ selectivity increased with pressure and temperature. Mixture gas with increasing pressure and temperature, removal efficiency of the $CO_{2}$ and $H_{2}S$ were decreased while concentration of $CH_{4}$ was increased up to 100%. When retentate flow rate was increased with the decreasing of pressure and temperature the $CH_{4}$ recovery ratio in retentate side was increased while the $CH_{4}$ purity in retentate side was decreased.

• Membrane Journal
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• v.5 no.1
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• pp.35-43
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• 1995

For several years lots of attempts have been made to establish the liquid membrane-based techniques for separations of gas mixtures especially containing carbon dioxide. A more effective system to separate $CO_{2}$ from flue gases, a circulatory hollow-fiber membrane absorber(HFMA) consisting of absorption and desorption modules with vacuum mode, has been considered in this study. Gas-liquid mass transfer has been modeled on a membrane module with non-wetted hollow-fibers in the laminar flow regime. The influence of an absorbent flow rate on the separation performance of the circulatory HFMA can be predicted quantitatively by obtaining the $CO_{2}$ concentration profile in a tube side. The system of $CO_{2}/N_{2}$ binary gas mixture has been studied using pure water as an(inert) absorbent. As the absorbent flow rate is increased, the permeation flux(i.e., defined as permeation rate/membrane contact area) also increases. The enhanced selectivity compared to the previous results, on the other hand, shows the decreasing behavior. It has been found obviously that the permeation flux depends on the variations of pressure in gas phase of desorption module. From an accurate comparison with the results of conventional flat sheet membrane module, the advantageous permeability of this circulatory HFMA can be clearly ascertained as expected. Our efforts to the theoretical model will provide the basic analysis on the circulatory HFMA technique for a better design and process.

• Membrane Journal
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• v.29 no.1
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• pp.51-60
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• 2019

In order to improve gas separation properties of polymeric membranes which have been widely applied in the industry field, aluminosilicate hollow nanoparticles named as allophanes were synthesized by sol-gel method and formulated in Poly(dimethylsiloxane) (PDMS) matrix to investigate the gas separation properties of PDMS membrane. Transmission electron microscope (TEM), Energy dispersive X-ray analysis (EDX), X-ray diffractometer (XRD), Surface area and pore size analyzer (BET) and Fourier transform infrared spectrophotometer (FTIR) were carried out to characterize the synthetic allophanes. Then the PDMS mixed matrix membranes were prepared by adding different volume fraction of allophanes. To examine the effect of allophanes addition in PDMS matrix using unmodified allophane and modified ones, the gas permeation experiments were performed using oxygen, nitrogen, methane and carbon dioxide. As the volume fraction of modified allophane increased up to 4.05 Vol% the permeability of four test gases through PDMS mixed matrix membranes increased. Also, the selectivity of $O_2/N_2$ and $CO_2/CH_4$ increased with the contents of the modified allophane. Further improvement of gas separation properties of PDMS mixed matrix membranes containing higher volume percent of allophanes can be expected as long as well dispersion of allophanes in PDMS matrix can be achieved for better PDMS membranes.

• Membrane Journal
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• v.33 no.6
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• pp.362-368
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• 2023

This research article explores the application of Polymer of Intrinsic Microporosity (PIM-1) as a cutting-edge material for CO₂ gas separation membranes in response to the escalating global concern over climate change and the imperative to reduce greenhouse gas emissions. The study delves into the synthesis, molecular weight control, and fabrication of PIM-1 membranes, providing comprehensive insights through various characterization techniques. The intrinsic microporosity of PIM-1, arising from its unique crosslinked and rigid structure, is harnessed for selective gas permeation, particularly of carbon dioxide. The article emphasizes the tunable chemical properties of PIM-1, allowing for customization and optimization of gas separation membranes. By controlling the molecular weight, higher molecular weight (H-PIM-1) membranes are demonstrated to exhibit superior CO₂ permeability and selectivity compared to lower molecular weight counterparts (L-PIM-1). The study's findings highlight the critical role of molecular weight in tailoring PIM-1 membrane properties, contributing to the advancement of next-generation membrane technologies for efficient and selective CO₂ capture-an essential step in addressing the pressing global challenge of climate change.

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.460-464
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• 2011

Poly(ether-block-amide)(PEBA, $PEBAX^{TM}$) resin is a thermoplastic elastomer combining linear chains of hard-rigid polyamide block interspaced soft-flexible polyether block. It was believed that the hard polyamide block provides the mechanical strength and permeation selectivity, whereas gas transport occurs primarily through the soft polyether block. The objective of this work was to investigate the gas permeation properties of carbon dioxide and methane for $PEBAX^{TM}$-1657 membrane and compare with those obtained for other grade of $PEBAX^{TM}$, $PEBAX^{TM}$-2533. And the organic/inorganic hybrid membranes were prepared using $PEBAX^{TM}$ and TEOS(tetraethoxysilane) by sol-gel process, and gas permeation properties were studied. $PEBAX^{TM}$-2533 membrane exhibited higher gas permeability coefficients than $PEBAX^{TM}$-1657 membrane. This was explained by the increase of chain mobility. The permeability coefficients for $PEBAX^{TM}$/TEOS hybrid membranes were higher than pure $PEBAX^{TM}$ membranes. This results were explained by the reduction of crystallinity of polyamide block by the introduction of TEOS. Ideal separation factor of hybrid membranes does not change much. This might be due to the increase of solubility selectivity.

• Membrane Journal
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• v.15 no.4
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• pp.310-319
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• 2005

This paper describes the preliminary study on the development of multi-stage membrane demonstration plant for removal of carbon dioxide from flue gas stream being emitted from LNG boiler in thermal power generation plant. The prerequisite requirement is to design and develop the membrane process producing a $99\%\;CO_2$ with $90\%$ recovery from LNG flue gas of 1,000 $Nm^3$/day. Asymmetric polyethersulfone hollow fiber membranes and membrane modules developed in this laboratory[1] were used in this study. Using the permeation data for the hollow fiber membranes, modelling on the membrane module and multi-stage membrane process was done to meet the requirement condition of the process design. The effects of the operating pressure of feed and permeate side and feed concentration on $CO_2$ purity and recovery were investigated experimentally with the developed hollow fiber modules. These experimental results matched well with theoretical modelling results.

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.179-186
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• 2020

In this study, chitosan/zeolite composites were prepared by using basalt-based zeolite impregnated with aqueous chitosan solution for the adsorptive separation of CO₂. The prepared composites were characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption analysis. In addition, the adsorption equilibrium isotherms for CO₂ and N₂ were measured at 298 K using a volumetric adsorption system, and the results were analyzed by applying adsorption isotherm equations (Langmuir, Freundlich, and Sips) and energy distribution function. It was found that CO₂ adsorption capacities were well correlated with the structural characteristics of chitosan and zeolite, and the ratio of elements [N/C, Al/(Si + Al)] formed on the surface of the composite. Moreover, the CO₂/N₂ adsorption selectivity was calculated under the mixture conditions of 15 V : 85 V, 50 V : 50 V, and 85 V : 15 V using the Langmuir equation and the ideal adsorption solution theory (IAST).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.21-27
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• 2016

Global warming due to greenhouse gas emissions is considered as a major problem worldwide, and many countries are making great efforts to reduce carbon dioxide emissions. Many technologies in post-combustion, pre-combustion and oxy-fuel combustion $CO_2$ capture have been developed. Among them, a hybrid pre-combustion $CO_2$ capture system of a water gas shift (WGS) reactor and a membrane gas separation unit was investigated. The 2 stage WGS reactor integrated high temperature shift (HTS) with a low temperature shift (LTS) was used to obtain a higher CO conversion rate. A Pd/Cu dense metal membrane was used to separate $H_2$ from $CO_2$ selectively. The performance of the hybrid system in terms of CO conversion and $H_2$ separation was evaluated using a 65% CO, 30 % $H_2$ and 5% $CO_2$ gas mixture for applications to pre-combustion $CO_2$ capture. The experiments were carried out over the range of WGS temperatures ($200-400^{\circ}C$), WGS pressures (0-20bar), Steam/Carbon (S/C) ratios (2.5-5) in a feed gas flow rate of 1 L/min. A very high CO conversion rate of 99.5% was achieved with the HTS-LTS 2 stage water gas shift reactor, and 83% $CO_2$ was concentrated in the retentate using the Pd/Cu membrane.

• Membrane Journal
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• v.22 no.1
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• pp.16-22
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• 2012

The influence of co-existing gases on the hydrogen permeation without sweep gas was studied through a Pd-coated $V_{99.8}B_{0.2}$ alloy membrane. Membranes have been investigated in the pressure range 1.5-8.0 bar under pure hydrogen, hydrogen-carbon dioxide and hydrogen-carbon monoxide gas mixture without sweep gas at $400^{\circ}C$. Preliminary hydrogen permeation experiments without sweep gas have been confirmed that hydrogen flux was $40.7mL/min/cm^2$ for a Pd-coated $V_{99.8}B_{0.2}$ alloy membrane (thick : 0.5 mm) using pure hydrogen as the feed gas. In addition, hydrogen flux was $21.4mL/min/cm^2$ for $V_{99.8}B_{0.2}$ alloy membrane using $H_2/CO_2$ as the feed gas. The hydrogen permeation flux decreased with decrease of hydrogen partial pressure irrespective of pressure when $H_2/CO_2$and $H_2/CO$mixture applied as feed gas respectively and permeation fluxes were satisfied with Sievert's law in different feed conditions. It was found from XRD, SEM/EDX results after permeation test that the Pd-coated $V_{99.8}B_{0.2}$ alloy membrane had good stability and durability for various mixtures feeding condition.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.9
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• pp.1027-1034
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• 2007

This research was focused on the selective separation of $CO_2$ or $CH_4$ from mixture of these gases, by controlling the size of pore or pore gate. Pitch based activated carbon fibers(ACF) were used as adsorbents. The size of pore gate was controlled by the molecule having similar size to that of pore opening. After the adsorption of adsorbate on pore surface, planar molecules such as benzene and naphthalene covered the pore gate. The slow release of adsorbate from the pores covered by planar molecules makes apertures between planar molecules covering pore gate and this structure can be fixed by rapid pyrolysis. The control of pore gate using benzene as covering molecules could not accomplished due to the simultaneous volatilization of benzene and adsorbate$(CO_2)$ caused by similar temperatures of benzene volatilization and adsorbate desorption. Therefore we replaced benzene with naphthalene looking for the stability at a $CO_2$ desorption temperature. The naphthalene molecule was adsorbed on the ACF up to 15% of ACF weight and showed no desorption until $100^{\circ}C$, indicating that the molecule could be used as a good cover molecule. Naphthalene could cover almost all the pore gate, reducing BET surface area from 753 $m^2/g$ to 0.7 $m^2/g$. A mixed gas$(CO_2:CH_4=50:50)$ was adsorbed on the naphthalene treated OG-7A ACF. The amount of $CO_2$ adsorption increased with total pressure, whileas thai of $CH_4$ was not so much influenced on the pressure, indicating that $CO_2$ made more compounds on the ACF surface along with total pressure increase. The most $CO_2$ and the least $CH_4$ were adsorbed in the condition of 0.4 atm, resulting in the highly pure $CH_4$ left in ACF.