• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.478-485
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• 2012

Polymers are widely used as membrane material for performing the separation of various gaseous mixtures due to their attractive permselective properties and high processability. The separation characteristics of $CH_4$ and $CO_2$ mixed gas using polyamide composite membrane has been studied in this work. The sample gas was prepared by mixing pure methane and carbon dioxide. Permeation tests were carried out at different operation conditions. Feed flow rates were varied between 800~1000 $cm^3/min$, and the stage cuts were varied between 50~60%. The gas inlet pressure and the temperature were varied as 6 bar and $30{\sim}70^{\circ}C$, respectively. The effects of the above mentioned parameters were investigated to estimate the permeability of $CH_4$ and $CO_2$, and the selectivity of $CO_2$ was also calculated for all conditions. The Arrhenius plots were also performed to obtaine the activation energies of $CH_4$ and $CO_2$ permeabilities.

• Membrane Journal
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• v.30 no.6
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• pp.420-432
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• 2020

Random copolymers made of both 'polymer of intrinsic microporosity (PIM-1)' and Ellagic acid were prepared for the first time by a facile one-step polycondensation reaction. By combining the highly porous and contorted structure of PIM (polymers with intrinsic microporosity) and flat-type hydrophilic ellagic acid, the membranes obtained from these random copolymers [(PIM-co-EA)-x] showed high CO2 permeability (> 4516 Barrer) with high CO2/N2 (> 23~26) and CO2/CH4 (> 18~19) selectivity, that surpassed the Robeson upper bound (2008) for both pairs of the gas mixture. Incorporation of flat-type ellagic acid into the PIM-1 not only enhances the gas permeability by disturbing the kinked structure of PIM-1 but also increases the selectivity of CO2 over N2 and CH4, due to an increase of rigidity and polarity in the resultant copolymer membranes.

• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.483-489
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• 2007

Polyaniline (PANI)/Polyimide (PI) membranes were prepared and the effects of PANI contents and doping on the structural properties and gas separation properties were studied. The polyamic acid (PAA) solution was prepared by the polycondensation reaction of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 4,4'-oxydianiline (ODA) in 1-methyl-2-pyrrolydinone (NMP) solvent. The PANI/PI blends were obtained by mixing PAA solution and PANI solution, and were doped with 1 M aqueous HCl solution for 24 h. The structural characterizations of the as-cast and doped membranes were examined by FT-IR, XRD, and TGA. The gas permeation experiments with $H_2$, $CO_2$, $O_2$, $N_2$, and $CH_4$ were carried out by variable pressure method at $30^{\circ}C$ and 5 atm. For all gases tested, the permeability coefficients of the blends decreased with increasing PANI content and the magnitude of permeability was in the order of $H_2$ > $CO_2$ > $O_2$ > $N_2$ > $CH_4$. The permeability for PANI/PI membranes decreased after the doping process while the permselectivity increased. For $H_2/CH_4$ separation, the doped PANI/PI (75/25) membrane has a permselectivity of 991.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.8
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• pp.586-591
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• 2013

This experiment was performed to enhance $CH_4$ purity of landfill gas by applying gas separator membrane for purified nitrogen gas production. 1:6 area ratios of $1^{st}$ to $2^{nd}$ membrane module was suitable for $CH_4$ recovery. After separation membrane system was installed, 249 tries were performed. Average permeability for $CH_4$ was 28.4% and for $CO_2$ was 94.3%. This can explain nitrogen gas separator membrane can be applied to collect $CH_4$ from LFG. However, nitrogen permeability only reached up to 16.5%. Therefore, the final purified landfill gas concentration was rounded up to 69.7% for $CH_4$, 4.3% for $CO_2$ and 26.0% for $N_2$. For the high degree of $CH_4$ purity, $N_2$ should be kept at least under 2.0% by controlling air inflow to landfill.

• Membrane Journal
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• v.30 no.6
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• pp.443-449
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• 2020

In this study, CO2 separation experiment was performed on a CH4/CO2 mixed gas using a ceramic hollow fiber membrane contactor module (HFMC). In order to fabricate high-durability HFMC, a high-durability hollow fiber membrane was prepared and evaluated. HFMC was fabricated using the prepared hollow fiber membrane, and the experiment used a mixture of CH4/CO2 (30% CO2, CH4 balance) and monoethanolamine (MEA). During HFMC operation, the effect of gas and absorbent pressure on the CO2 removal efficiency was evaluated. The CO2 removal efficiency increased as the gas pressure increased, and the CO2 absorption flux also showed a tendency to increase with the liquid flow rate. In addition, when the CO2 absorption rate was less than 40%, LTS-1, a counter-current form where the absorbent enters from the bottom, has higher CO2 removal performance than LTS-2, a countercurrent form in which the absorbent enters from the top. and when the absorption rate was 40% or higher, LTS-2 had higher performance than LTS-1.

• Membrane Journal
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• v.23 no.6
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• pp.450-459
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• 2013

2,3,5,6-Tetramethyl-1,4-phenylenediamine (TMPD) based polyimide (PI) were crosslinked with 1,2-Diaminoethane (DAE) and 1,6-Diaminohexane (DAH) to enhance gas transport properties. Fourier transform infrared (FT-IR) studies show that imide groups were converted into amide groups during crosslinking process. Thermogravimetric analysis (TGA) results indicate that the degradation temperature of crosslinked PI membranes decreased after crosslinking. This is due to degradation of alkyl group in crosslinking agent. The d-space of crosslinked PI membranes decreased with increasing crosslinking time. The ideal permeability for $CH_4$, $N_2$, $O_2$, and $CO_2$ decreased after crosslinking and the ideal permeability of crosslinked PI membranes induced by DAH is larger than that by DAE. In contrast, the permselectivity of $CO_2/CH_4$, $CO_2/N_2$ and $O_2/N_2$ increased during crosslinking. For the gas pair of $CO_2/CH_4$, the maximum increment is about 39.5% after 6 minutes of DAE crosslinking. Also, that of $O_2/N_2$ gas pair is about 20.5% after 6 minutes of DAE crosslinking. According to these result, DAE is more suitable for enhanced permselectivity than DAH. On the contrary, DAE is not useful for $CO_2/N_2$ separation due to reduction in $CO_2/N_2$ permselectivity after 3 minutes DAE crosslinking.

• Membrane Journal
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• v.25 no.1
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• pp.27-31
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• 2015

PEBAX[poly(ether-block-amide)]-NaY zeolite composite membrane was studied on the permeability of penetrant $H_2$, $N_2$, $CO_2$ and $CH_4$ and the selectivity. When the NaY zeolite contents of PEBAX-NaY zeolite membranes were increased, the permeability of $H_2$ was increased, but the permeability of $N_2$, $CH_4$ and $CO_2$ was decreased. By the addition of NaY zeolite into PEBAX, the gas selectivity for $H_2$, $N_2$ and $CO_2$ was decreased except the increase of selectivity of $H_2/N_2$. $CO_2/N_2$, $H_2/CO_2$ and Gas/$CH_4$. The highest selectivity among these gases was from $CO_2$. In particular, the gas selectivity for $CO_2$ was the greatest with a value of 12~156.

• Journal of the Korean Society of Combustion
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• v.4 no.2
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• pp.97-108
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• 1999

This numerical study was to investigate the effect of $CO_2$ addition on the structures and NOx formation characteristics in $CH_4$ counterflow diffusion flame. The importance of radiation effect was identified and $CO_2$ addition effect was investigated in terms of thermal and chemical reaction effect. Also the causes of NOx reduction were clarified by separation method of each formation mechanisms. The results were as follows : The radiation effect was intensified by $CO_2$ addition. Thermal effect mainly contributed to the changes in flame structure and the amount of NO formation but the chemical reaction effect also cannot be neglected. The reduction of thermal NO was dominant with respect to reduction rate, but that of prompt NO was dominant with respect to total amount.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.511-517
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• 2002

The complex 1 $([Cp*Fe(CO)_2]_2-(\mu-CH=CH-CH=CH))$ which have butadiene as a bridge were synthesized from $Cp*(CO)_2FeK$ and cis-3,4-dichlorocyclobutene. The derivatives of complex 1 where one or two carbonyl groups are replaced by phosphine ligands have been prepared by photochemical substitution. The new derivatives $([Cp*Fe(L)_2]_2-(\mu-CH=CH-CH=CH))$ where L = $(Ph_2PCH_2CH_2PPh_2)$ and $([Cp*Fe(CO)(L)]_2-(\mu-CH=CH-CH=CH))$ where L : $PPh_3$ have been characterized from $^^1H-$, $^^13C-$,$^^31P-NMR$ and elemental analysis. Obtained complexes have been studied in electrochemical experiment and UV/VIS-near-IR. The mixed-valence radical cation forms of complex 2, 3 species were found to be delocalized as the Class III. Based on the separation of the waves ($\triangle E$ : 0.470 ~ 0.605 V), the efficiency of electronic communication between two metal centers of cation species leading to stabilization relative to neutral species. The phosphine-substitute complexes (2, 3) displays two reversible oxidation waves and oxidation state of metal centers-dependent color change, electrochromism, was observed from yellow to orange and deep blue in methylene chloride.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.414-422
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• 2008

Adsorption experiments for $H_2$, $CH_4$, CO, $CO_2$ on activated carbon and zeolite 5A were performed by static volumetric method. A 4-bed pressure swing adsorption (PSA) process was to study separation of hydrogen from multi-component mixture gases ($H_2$ 72.2%, $CH_4$ 4.06%, CO 2.03%, $CO_2$ 21.6%). Dual-site langmuir (DSL) isotherm showed good or fair agreement with the experimental results. The optimum height of activated carbon layer was 55 cm with breakthrough results on the packing ratio of activated carbon to zeolite 5A. In PSA process, the effects of the process parameters such as total cycle time ($T_c$), ${\Delta}P$ at the provide purge step and adsorption pressure on the PSA performance were studied experimentally and theoretically.