• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.67-76
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• 2018

In this study, PDMS-HNT and PDMS-mHNT composite membranes were prepared by the addition of halloysite nanotube (HNT) and modified HNT (mHNT) to PDMS. To investigate the physico-chemical characteristics of composite membranes, analytical methods such as FT-IR, XRD, TGA, and SEM were utilized. The gas permeability and selectivity properties of $N_2$ and $CO_2$ were evaluated. In particular, the PDMS-HNT with 10 wt% HNT and PDMS-mHNT with 5 wt% mHNT showed the highest $CO_2/N_2$ selectivity and $CO_2$ permeability at $35^{\circ}C$, respectively. Overall, PDMS-HNT and PDMS-mHNT composite membranes improved the $CO_2/N_2$ selectivity compared to that of using PDMS membrane.

• Proceedings of the Materials Research Society of Korea Conference
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• 2006.11a
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• pp.17.2-17.2
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• 2006

• Journal of Internet Computing and Services
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• v.23 no.5
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• pp.9-15
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• 2022

This paper proposes a coordinated multi-point communication (CoMP) method with channel selection to improve performance of a macro user equipment (MUE) in a dense small-cell network environment in a building located within coverage of a macro base station (MBS). In the proposed CoMP method, in order to improve the performance of the MUE located in the building, A small-cell base station (SBS) selects a channel with lower interference to the neighboring MUE and transmits appropriate signals to the MUE requiring CoMP. Simulation results show that the proposed CoMP method improves the performance of the MUE by up to 164% and 51%, respectivley, compared to a random channel allocation based traditional SBS network and CoMP method.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.679-687
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• 2020

In this study, poly(ether-block-amide) (PEBAX)/zeolitic imidazolate framework-8 (ZIF-8)-polyetherimide (PEI), and PEBAX/amine-modified ZIF-8 (amineZIF-8)-PEI composite membranes were prepared by varying the contents of ZIF-8 and amineZIF-8. Also the gas permeability properties of N2 and CO2 were investigated for each composite membrane. The N2 and CO2 permeability of the PEBAX/ZIF-8-PEI composite membrane increased as the ZIF-8 content increased, while the CO2/N2 selectivity gradually decreased. In the case of the PEBAX/amineZIF-8-PEI composite membrane, the permeability of N2 decreased slightly, and CO2 increased till amineZIF-8 amount was 0.5 wt% and then decreased when the content increased further. The CO2/N2 selectivity was the highest with a value of 78.3 at 0.5 wt% of amineZIF-8. because the amine modification in the amineZIF-8 improves the compatibility between PEBAX and amineZIF-8, It seems that amineZIF-8 was evenly dispersed in PEBAX, which could be greatly influenced by the porousity of ZIF-8 and also the affinity of amine toward CO2.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.228.1-228.1
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• 2010

선택적 CO 산화반응(PrOx)을 위한 Ru이 고분산 담지된 $Ru/{\alpha}-Al_2O_3$ 촉매를 증착-침전법(deposition-precipitation)으로 제조하였다. 용액의 pH와 aging 시간에 따른 Ru 입자의 크기 변화와 분산도의 영향을 살펴보았으며 함침법(impregnation)으로 비교 촉매를 제조하였다. 촉매의 특성분석은 BET, TPR, CO-Chemisorption분석을 수행하여 촉매의 비표면적, 환원특성, 분산도를 알 수 있었다. 특성분석결과, 증착-침전법으로 제조한 $Ru/{\alpha}-Al_2O_3$ 촉매가 함침법으로 제조한 촉매에 비해 분산도가 높았으며, pH별 촉매 제조에서는 pH6.5로 제조한 촉매가 22.06%로 가장 높은 분산도를 보였다. 또한, 담체의 비표면적 영향에 따른 Ru 입자의 분산도를 살펴보기 위해 ${\gamma}-Al_2O_3$와 ${\alpha}-Al_2O_3$ 담체를 적용한 결과, 비표면적이 작은 ${\alpha}-Al_2O_3$ 담체 표면에서 Ru 분산도가 ${\gamma}-Al_2O_3$ 담체에 비해 높았다. 이는 기공이 발달하여 비표면적이 넓은 ${\gamma}-Al_2O_3$ 담체는 소량의 Ru을 고분산 담지 시 담체 표면보다는 기공 내에 담지 되는 양이 많아 실제 반응 시 반응에 참여하는 표면 활성 금속양이 적음을 알 수 있다. 특히, 선택적 산화반응과 같이 표면에서 빠른 반응이 일어나는 경우, 기공 내부의 활성금속이 반응에 참여하기 어려워 반응 활성이 낮음을 PrOx 반응실험을 통해 확인할 수 있었다. PrOx test 조건은 GHSV 250000~60000, 온도는 80~200도, 람다값은 2~4로 성능 비교하여 실험 하였다. PrOx의 성능평가 결과 담체를 ${\alpha}-Al_2O_3$를 사용하여 deposition-precipitation방법으로 제조한 pH6.5 촉매에서 $100{\sim}160^{\circ}C$에서 90%의 가장 높은 CO conversion을 가지고 18%의 선택도를 가졌다.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.490-494
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• 2016

This paper describes the very efficient and highly enantioselective ring opening of terminal epoxides with alkyl and arene sulfonic acid. The dinuclear chiral (salen) Co complexes bearing Lewis acids of Al, Ga and In catalyze the reaction enantioselectively in the presence of tetrabutylammonium chloride using tert-butyl methyl ether as a solvent. The variation of the anion of the tetra butyl ammonium salt has significant impact on the reactivity and selectivity of the asymmetric ring opening of phenyl glycidyl ether with p-toluenesulfonic acid. The order of reactivity and selectivity was found to be $Cl^-$ > $l^-$ > $Br^-$ > $OH^-$. Strong synergistic effects of the different Lewis acid centers of Co-Al, Co-Ga and Co-In complexes were observed in the catalytic process. The dinuclear chiral salen catalyst containing $AlCl_3$ was found to be most active and highly enantioselective (91% ee).

• Membrane Journal
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• v.32 no.5
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• pp.325-335
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• 2022

In this study, zeolitic imidazolate framework-9 (ZIF-9) was synthesized and Pebax/ZIF-9 mixed membranes were prepared by varying the content in poly(ether-b-amide)-1657 (Pebax-1657), and then a single gas (N₂, CO₂) was permeated to investigate the gas permeation characteristics of the mixed membrane. As the ZIF-9 content incorporated into the pure Pebax membrane increased, the N₂ permeability gradually decreased, and the CO₂ permeability increased up to the Pebax/ZIF-9 3 wt% mixed membrane, and then decreased at the content thereafter. And among the mixed membranes, the Pebax/ZIF-9 3 wt% mixed membrane showed the highest selectivity of 69.3 by selectively accepting CO₂ as the gate-opening phenomenon occurred for the polar gas, CO₂. In addition, both the CO₂ permeability and the CO₂/N₂ selectivity increased, resulting in the closest Robeson upper-bound.

• Membrane Journal
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• v.24 no.3
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• pp.185-193
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• 2014

PDMS (polydimethylsiloxane)-HNT (halloysite nanotube) composite membranes were prepared with different amounts tendency of HNT 5, 10, 20 and 30 wt% and rubbery polymer PDMS. The characteristics of these membranes were studied by FT-IR, XRD, TGA, and SEM. Gas permeation experiment were performed under condition of $25^{\circ}C$ and $3kg/cm^2$. Gas permeability of $N_2$, $H_2$, $CH_4$, and $CO_2$ and selectivity were investigated by increasing the amount of HNT contents in the PDMS. In $H_2$, $N_2$, $CH_4$, and $CO_2$ gases, as increasing HNT contents from 0 to 30 wt%, decreasing value of the permeability were observed. The selectivity of ($CO_2/N_2$) was shown in the range of 14 to 44 and the range of selectivity of ($CO_2/CH_4$) was 3.0 to 7.0.

• Membrane Journal
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• v.30 no.1
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• pp.46-56
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• 2020

In this study, poly (ether-block-amide) (PEBAX)/poly (ethylene) glycoldiacrylate (PEGDA)/zeolitic imidazolate framework-8 (ZIF-8)-polyethersulfone (PES) composite membranes were prepared. The gas permeation properties of N₂ and CO₂ were investigated for each composite membrane. First, the gas permeability in the PEBAX/PEGDA-PES composite membrane decreased with increasing PEGDA content for each molecular weight at PEGDA250, PEGDA575, and PEGDA-700 g/mol. The CO₂/N₂ selectivity showed a constant value and gradually increased with increasing PEGDA content after 30 wt% PEGDA, and PEBAX/PEGDA250 50 wt%-PES prepared by adding PEGDA250 g/mol 50 wt% showed a selectivity of 15.1. This is because as the PEGDA content increases, the number of diacrylate groups increases, and the CO₂ affinity due to the ether structure of PEGDA increases. Gas permeation properties according to ZIF-8 were investigated for composite membranes of PEGDA 0 to 30 wt%, with CO₂/N₂ selectivity almost constant for each molecular weight. The permeability of N₂ and CO₂ gradually increased with increasing ZIF-8 content, and CO₂/N₂ selectivity was the highest at 3.4 in PEBAX/PEGDA250 g/mol 30 wt%/ZIF-8 20 wt%-PES composite membrane.

• Membrane Journal
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• v.22 no.2
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• pp.142-154
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• 2012

In order to remove $CO_2$ from the DME plant process, we investigated the composite membrane with rubbery polymers as the separation layer and its separation performance of $CO_2$ and $H_2$. Hollow fiber membranes for supporting layer were prepared by solution spinning method. In case of using PDMS as a separation layer, the composite membranes showed the permeation rates of $CO_2$ were over 300 GPU and minimum $CO_2/H_2$ selectivitties were 4.3 and in case of using PEBAX as a separation layer, the composite membranes showed the permeation rates of $CO_2$ were over 120 GPU and minimum $CO_2/H_2$ selectivities were 5.