• Korean Journal of Materials Research
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• v.14 no.2
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• pp.157-162
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• 2004

The object of this research is to develop a carbon molecular sieve(below CMS) which can separate selectively to convert mixture gases spout at waste landfill into fuel. And this research is meaningful from the viewpoint of a quality improvement of CH$_4$ gas and an utilization of by-product. CMS was prepared using coconut shell powder as starting material and the effects of activators, temperature and modifier on the reaction were investigated in this research. Also, pore diameter, surface area of CMS and adsorption rate were measured and studied by cahn balance and ASAP2010. Its specific surface area and pore distribution were controlled easily at 800^{\circ}C and adsorption rate was very good. The CMS prepared in this research is shown to be able to separate landfill gases very effectively.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.183-186
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• 2004

Nano particles-containing CMS membranes were prepared by pyrolysis of polyimides dispersed uniformly with precursors and their gas separation performances were examined, to elucidate the permeation mechanism and to further improve the gas separation performance. Consequently, it was suggested that the separation performance could be controlled by doping nano-particles in the CMS membranes, and that optimization of various factors, such as the size, content, and dispersion state of the nano particles would contribute for further improvement of the gas separation performance.

• Korean Membrane Journal
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• v.4 no.1
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• pp.25-35
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• 2002

The gas permeation properties have been studied on carbon molecular sieve (CMS) membranes prepared by pyrolysis of P84 polyimide under various conditions. P84 polyimide shows high permselectivities (O$_2$/N$_2$= 9.17 and CO$_2$/N$_2$= 35) for various gas pairs and has a good processibility because it is easily soluble in high polar solvents such as N-methylpyrrolidinone (NMP), dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc). After pyrolysis under Ar flow, the change in the heating rate was found to affect the gas permeation properties to some extent. The permeabilities of the selected gases were shown to be in the order He ＞ CO$_2$＞ O$_2$＞ N$_2$for all the CMS membranes, whose order was in accordance with the order of kinetic gas diameters. It also revealed that the pyrolysis temperature considerably influenced the gas permeation properties of the CMS membranes derived from P84 polyimide. The CMS membranes pyrolized at 700$\^{C}$ temperature exhibited the highest permeability with relatively targe loss in permselectivity. This means that the pyrolysis temperature should be varied in accordance with target gases to be separated.

• Membrane Journal
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• v.7 no.1
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• pp.15-21
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• 1997

Carbon molecular sieve (CMS) membranes were synthesized by the pyrolysis of polymeric precursors. The CMS materials had oxygen-nitrogen selectivities much higher than those observed for the polymeric precursors. Typically molecular sieving materials have diffusion selectivities much higher than polymeric materials. This has been identified as a result of higher entropic selectivity of the molecular sieving materials. A study of the development of molecular sieving properties as the polymeric precursor is pyrolyzed into a CMS material will offer us an insight into polymeric molecular structures needed for enhanced entropic selectivity membrane materials.

• Applied Chemistry for Engineering
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• v.33 no.5
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• pp.488-495
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• 2022

Activated carbon (AC) and carbon molecular sieve (CMS) have attracted attention as porous materials for recovery and separation of greenhouse gases. The carbon molecular sieve having uniform pores is used for collecting and separating gases because it may selectively adsorb a specific gas. The size and uniformity of pores determine the performance of the CMS, and chemical vapor deposition (CVD) is widely used to coat the surface with a predetermined thickness in order to control the CMS's micropores. This CVD method can be used to control the size of pores in CMS manufacturing, but it must be optimized because of its various experimental variables. Therefore, in order to produce AC and CMS for gas adsorption and separation, this review focuses on various activation processes and pore control technologies by CVD and surface treatment.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.527-534
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• 2012

The adsorption dynamics of activated carbon (AC) and carbon molecular sieve (CMS) beds were studied to recover ethylene from FCC fuel gas. In this study, the FCC fuel gas used consisted of six-component mixture ($CH_4/C_2H_4/C_2H_6/C_3H_6/N_2/H_2$,32:15:14:2:12:25 vol.%). And the breakthrough experiments of adsorption and desorption were carried out. The breakthrough sequence in the AC bed was $H_2$ < $N_2$ < $CH_4$ < $C_2H_4$ < $C_2H_6$ while the sequence in the CMS bed was $H_2$ < $CH_4$ < $N_2$ < $C_2H_6$ < $C_2H_4$. The separation performance of the CMS bed during the adsorption step was lower than that of the AC bed. However, due to the characteristics of kinetic separation, the CMS bed could remove $CH_4/N_2$ as well asthe molecules that are larger than $C_2H_6$, which was not easy to be done by the AC bed. Since it was hard to regenerate the adsorption bed by simple depressurization, vacuum regeneration should be adopted. As a result, the pressure vacuum swing adsorption (PVSA) process, consisting of CMS pretreatment process and AC main process, was suggested to recover ethylene efficiently.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.323-328
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• 2010

In this work, an intention to synthesize the carbon molecular sieve (CMS) with ideal sieving properties from palm shell has been attempted. The process includes three main stages: carbonization, carbon dioxide activation and polymer deposition using polyfurfuryl alcohols. Palm shell based activated carbon (AC) produced by carbon dioxide activation was used as raw material in synthesis of CMS. After preparing palm shell based AC, optimum concentration ratio of furfuryl alcohols and formaldehyde to AC for CMS synthesis was obtained in this study. Deposition of polyfurfuryl alcohols on the palm shell based AC was then carried out prior to carbonization. These polymer deposited AC was subjected to carbonization at $700-900^{\circ}C$ under inert condition. All the microporous materials were analyzed using micromeritics ASAP/2020. The results show that optimum concentration ratio of furfuryl alcohol and formaldehyde to AC is 1:2.5. The micropore with pore width less than 7 ${\AA}$ was formed on the polymer deposited AC at $700^{\circ}C$, $800^{\circ}C$ and $900^{\circ}C$ for 1.5 hours. Carbonization temperature at $900^{\circ}C$ for 1.5 hours was found to be optimum for CMS synthesis. The CMS produced under this condition has pore width of 5.884 ${\AA}$.

• Membrane Journal
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• v.14 no.2
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• pp.99-107
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• 2004

Carbon molecular sieve (CMS) membranes were prepared by pyrolysis of polyimides having carboxylic acid groups and applied to the hydrogen separation. The polymeric membranes having carboxylic acid groups showed different steric properties as compared with polymeric membranes having other side groups ($-CH_3$ and $-CF_3$) because of the hydrogen bond between the carboxylic acid groups. However, the microporous CMS membranes were significantly affected by the decomposable side groups evidenced from the wide angle X-rat diffraction, nitrogen adsorption isotherms, and single gas permeation measurement. Furthermore, the gas separation properties of the CMS membranes were essentially affected by the pyrolysis temperature. As a result, the CMS membranes Prepared by Pyrolysis of polyimide containing carboxylic acid froups at $700^{\circ}C$ showed the $H_2$ permeability of 3,809 Baller [$1{\times}10^{-10}$ H $\textrm{cm}^$(STP)cm/$\textrm{cm}^2$.s.cmHg], $H_2$/$N_2$, selectivity of 46 and $H_2$/$CH_4$ selectivity of 130 while the CMS membranes derived from polyimide showed the H$_2$ permeability of 3,272 Barrer, $H_2$/$N_2$ selectivity of 136 and $H_2$/$CH_4$ selectivity of 177.

• Membrane Journal
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• v.26 no.3
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• pp.220-228
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• 2016

Carbon molecular sieve (CMS) hollow fiber membranes were prepared by carbonizing a polyimide precursor manufactured by non-solvent induced phase separation process. Gas separation performance of CMS hollow fiber membrane was investigated on the effect of three carbonization conditions. CMS membrane with the highest gas separation performance was obtained at the pyrolysis temperature of $250-450^{\circ}C$: $N_2$, $SF_6$, and $CF_4$ permeance were 20, 0.32, 0.48 GPU, respectively, and $N_2/SF_6$ and $N_2/CF_4$ selectivities were 62 and 42, respectively. In the $SF_6/CF_4/N_2$ mixture gas test, when the stage cut was 0.2, the recovery ratio of $SF_6$ and $CF_4$ was over 99% and 98%. $SF_6$ concentration ratio was 4.5 times higher than the $SF_6$ concentration at the feed side. From the results, it was concluded that CMS membrane was one of the promising membranes for recovery Perfluorocompound gases process.

• Membrane Journal
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• v.23 no.5
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• pp.332-342
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• 2013

In the present study, carbon molecular sieve (CMS) hollow fiber membranes were prepared by carbonizing a methyl imide hollow fiber precursor, which was spun by non-solvent induced phase separation process. And effects of carbonization parameters such as pre-oxidation, pyrolysis, and post-oxidation on the gas permeation were systematically investigated. CMS membrane having the highest gas flux was obtained by carbonizing the precursor through a combined process of air pre-oxidation at $250^{\circ}C$ for 2h, nitrogen pyrolysis at $550^{\circ}C$ for 2h, and oxygen post-oxidation at $250^{\circ}C$ for 2h. The optimized membrane showed a considerable gas permeance : the $H_2$, He, $CO_2$ permeances were 69.72, 35.61, 31.01 GPU, respectively, and the $O_2$ and $N_2$ permeances were ignorable. Therefore, it was clear that the prepared CMS hollow fiber membrane was a promising membrane for recovering small gases such as hydrogen and hellium and carbon dioxide.