• Title/Summary/Keyword: Trifluoromethane

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Effects of Oxygen Enrichment on the Structure of Premixed Methane/Fluorinated Compound Flames (메탄-불소계 화합물의 예혼합화염 구조에서 산소 부화의 효과)

  • Lee, Ki-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.8
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    • pp.839-845
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    • 2011
  • We performed numerical simulations of freely propagating premixed flames at atmospheric pressure to investigate the influence of trifluoromethane on $CH_4/O_2/N_2$ flames under oxygen enrichment. Trifluoromethane significantly contributed toward a reduction in flame speed, the magnitude of which was larger in terms of the physical effect than the chemical effect. More trifluoromethane could be added and consumed on oxygen-enriched $CH_4/O_2/N_2$ flames. $CHF_3$ was decomposed primarily via $CF_3{\rightarrow}CF_2{\rightarrow}CF{\rightarrow}CF:O{\rightarrow}CO$ and $CHF_3+M{\rightarrow}CF_2+HF+M$ played an important role in oxygen-enhanced flames. When an inhibitor was added to oxygen-enriched flames, the position of the maximum concentration of active radicals was shifted to a relatively low temperature range, and the net rate of OH became higher than that of H.

Preparation of Iodine Compound Using Trifluoromethane (트리플루오르메탄을 이용한 요오드화합물의 제조)

  • Choi, Woo-Jin;Ahn, Sung-Hwan;Jang, Young-Jun;Kim, Kyu-Sung;Kim, Myung-Soo;Park, Hong-Soo;Hahm, Hyun-Sik
    • Journal of the Korean Applied Science and Technology
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    • v.21 no.4
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    • pp.359-363
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    • 2004
  • Reaction conditions and catalysts were investigated for direct $CF_3I$ synthesis. Optimum reaction temperature was determined by pyrolysis of $CF_3H$ and catalytic reactions. Reactions with changing oxygen concentration were performed. As a result, yield of $CF_3I$ increased with decreasing oxygen concentration. Catalytic activity was changed with the weight ratio of the used metal salts. This result was stemmed from the change in the pore size of activated carbon by the metal salts. The optimum reaction conditions were: $600^{\circ}C$, space velocity of $45hr^{-1}$, and with 7wt% KF/AC catalyst.

Ionic Conductivity of Anion Receptor Grafted Siloxane Polymers for Solid Polymer Electrolytes

  • Lee, Won-Sil;Kim, Dong-Wook;Lee, Chang-In;Woo, Seong-Ihl;Kang, Yong-Ku
    • Journal of Electrochemical Science and Technology
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    • v.2 no.1
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    • pp.26-31
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    • 2011
  • We have prepared siloxane polymers grafted with trifluoromethane-sulfonylamide and oligoether side chains for solid polymer electrolytes with enhanced ionic conductivity. The grafted trifluoromethane sulfonylamide groups seem to be effective as an anion recepting site to enhance the ionic conductivity of the solid polymer electrolyte. The anion receptor grafted siloxane polymers showed one order of magnitude higher ionic conductivity than the siloxane polymers without anion receptor grafts. The fitting parameter A of the VTF plot which was related to the carrier density of the electrolyte increased with increasing the number of grafted anion receptor. The results of experiment indicate that the anion-complexing site of the anion receptor grafted polymer host effectively traps the anions. The anion receptor grafted polymer was found to be a promising material for lithium polymer batteries.

Electrochemical properties of gel copolymer- electrolyte based on Phosphonium ionic liquid

  • Cha, E.H.;Lim, S.A.;Park, J.H.;Kim, D.W.;Park, J.H.
    • Journal of the Korean Electrochemical Society
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    • v.11 no.4
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    • pp.304-308
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    • 2008
  • Noble Poly (lithium 2-acrylamido-2-methyl propane sulfonate) and its copolymer with N-vinyl formamide based on trihexyl (tetradecyl) phosphonium acetate [$(C_6H_{13})_3$ P ($C_{14}H_{29}$) $CH_3COO$; $P_{66614}$ $CH_3COO$] and trihexyl (tetradecyl)phosphonium bis(trifluoromethane sulfonyl) amide ([$(C_6H_{13})_3P(C_{14}H_{29})$] [TFSA];$P_{66614}TFSA$) were prepared and analyzed to determine their characteristics and properties. The ionic conductivity of a copolymer based $P_{66614}TFSA$ ionic liquid system exhibits a higher conductivity ($8.9{\times}10^{-5}Scm^{-1}$) than that of a copolymer based $P_{66614}CH_3COO$ system ($1.57{\times}10^{-5}Scm^{-1})$. The charge on the TFSA anion is spread very diffusely through the S-N-S core and particularly in the trifluoromethane groups, and this diffusion results in a decreased interaction between the cation and the anion. The viscosity of $P_{66614}TFSA$ (39 cP at 343 K) and $P_{66614}CH_3COO$ (124 cP at 343 K), which is very hydrophobic, was fairly high. High viscosity leads to a slow rate of diffusion of redox species. The ionic conductivity of copolymer of a phosphonium ionic liquid system also exhibits higher conductivity than that of a homopolymer system. Phosphonium ionic liquids were thermally stable at temperatures up to $400^{\circ}C$.

Electrical property of organic solvent dispersible poly(3,4-ethylenedioxythiophene) / polymeric ionic liquid complex (유기용제 분산형 poly(3,4-ethylenedioxythiophene) / 고분자 이온성 액체 복합체의 전기적 특성)

  • Lee, Tae-Hee;Kim, Tae-Young;Duong, Ha Thi Thuy;Suh, Min-Won;Kim, Jong-Eun;Suh, Kwang-S.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.146-147
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    • 2008
  • Poly(3,4-ethylenedioxythiophene) (PEDOT) / poly(1-vinyl-3-ethylimidazolium bis(trifluoromethane sulfonyl)imide) (poly(ViEtIm $^+TFSI^-$) complex was prepared for organic solvent dispersible conductive nano particles. By molar ratio, PEDOT / poly(ViEtIm $^+TFSI^-$) complex was polymerized and dispersed in propylene carbonate by 1 wt%. The maximum conductivity of the complexes was $1.2\times10^{-1}$ S/cm.

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Emission Characteristics of HFC-23 (CHF3)/HCFC-22 (CHClF2) between Different Air Masses in Northeastern Asia (동북아시아 지역에서의 공기괴별 HFC-23/HCFC-22의 배출특성)

  • Li, Shanlan;Kim, Joo-Il;Kim, Kyung-Ryul;Muhle, Jens
    • Journal of Korean Society for Atmospheric Environment
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    • v.26 no.5
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    • pp.490-498
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    • 2010
  • HCFC-22 (chlorodifluoromethane, $CHClF_2$), one of the major components in various refrigeration, is emitted mostly from developing countries, as its consumption is not limited until 2013 by the Montreal Protocol. In addition, HFC-23 (trifluoromethane, $CHF_3$), a by-product in the manufacture of HCFC-22, is also a powerful greenhouse gas. Here, we discuss the regional emission characteristics of these compounds based on high-frequency in-situ measurements using the "Medusa" GC-MS system. HCFC-22 and HFC-23 baseline concentrations measured at Gosan (Jeju Island, Korea) from November 2007 to December 2008 increased by 1.8 ppt/yr and 0.6 ppt/yr, respectively. Pollution events of these compounds were observed, very frequently (e.g., ~2~3 times) at Gosan than baseline levels. All the measurement data were divided into four groups by simultaneously considering the ratio (HFC-23/HCFC-22) and concentration (HCFC-22) at Trinidad Head (TH, California, USA). The residence time of trajectories were then analyzed in each of the four groups. The results exhibited the existence of a strong correlation with air mass origin for each group: 1) Air masses originating from Siberia in the north and from the Pacific in the south had ratios of 0.08~0.12 and concentrations of 196.9~254.3 ppt which is highly comparable to background air at TH. 2) Air masses passing over the Southern China exhibited similar ratios but higher HCFC-22 concentrations. 3) Air masses passing over the Northern China had ratios of 0.12~0.21. 4) Air masses passing over Korea and/or Japan had ratios of 0.01~0.08. Our results suggest that the HFC-23/HCFC-22 ratio can be used as a good indicator for the assessment of the pollution with Chinese origin. We also confirmed differences in air masses traveling over Northern and Southern China, most likely due to differences in air mass travelling speed over these regions before arriving at Gosan. This signature may be treated as one of the critical components in identifying the emission sources from different parts of China.

Preparation and Gas Permeability Measurements of PVDF-HFP/Ionic Liquid Gel Membranes (PVDF-HFP/이온성 액체 겔 분리막 제조 및 기체 투과도 측정)

  • Ko, Youngdeok;Park, Doohwan;Baek, Ilhyun;Hong, Seong Uk
    • Applied Chemistry for Engineering
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    • v.25 no.6
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    • pp.559-563
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    • 2014
  • It is well known that $CO_2$ can be dissolved easily in imidazolium-based room temperature ionic liquids (RTILs). Because of the high $CO_2$ solubility in RTILs, membranes containing RTILs can separate easily gas mixtures such as $CO_2/N_2$ and $CO_2/CH_4$. In this study, we prepared poly(vinylidene fluoride)-hexafluoropropyl copolymer (PVDF-HFP) gel membranes with several RTILs and measured permeabilities of several gases. When the anion of ionic liquids was tetrafluoroborate($BF{_4}^-$), both $CO_2$ permeability and selectivities decreased as the carbon number of the cation increased. When the cation of ionic liquids was 1-ethyl-3-methylimidazolium[emim], $CO_2$ permeability of gel membranes containing bis(trifluoromethane) sulfoneimide($Tf_2N^-$) anion was double compared to those containing tetrafluoroborate($BF{_4}^-$) anion. However, $CO_2/N_2$ and $CO_2/CH_4$ selectivities of the $Tf_2N^-$ case were decreased, whereas the $H_2$ selectivity was almost the same for two cases.

Synthesis of D-1,3-Dioxolane and D-1,3-Oxathiolane Pyrimidine Nucleosides (D-1,3-Dioxolane 및 D-1,3-Oxathiolane 피리미딘 뉴크레오사이드의 합성)

  • Hong, Joon-Hee;Cha, Ma-Rie;Shin, Seong-Eun;Choi, Bo-Gil;Chung, Byung-Ho;Kim, Joong-Hyup;Lee, Chong-Kyo;Chung, Won-Keun;Chun, Moon-Woo
    • YAKHAK HOEJI
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    • v.38 no.6
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    • pp.703-711
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    • 1994
  • We synthesized D-1,3-dioxolanyl acetate from D-mannose using Frazer-Reide reaction and D-1,3-oxathiolanyl acetate from either D-mannose or D-galactose in good yields. These acetates were conjugated with various disilylated pyrimidine base using trimethylsilyl trifluoromethane sulfonate as a Lewis acid catalyst to obtain 32 different D-nucleosides.

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Electrochemical Characterization of Lithium Polyelectrolyte Based on Ionic Liquid

  • Cha, E.-H.;Lim, S.-A.;Kim, D.-W.;Choi, N.-S.
    • Journal of the Korean Electrochemical Society
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    • v.12 no.3
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    • pp.271-275
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    • 2009
  • Five novel lithium polyelectrolyte-ionic liquid systems, using poly (lithium 2-acrylamido-2-methyl propanesulfonate; PAMPSLi) were prepared and their electrochemical properties were measured. The ionic conductivity of the PAMPSLi/1-ethyl-3-methylimidazolium tricyano methanide (emImTCM) system was exhibited high conductivity (1.28 $\times$ $10^{-3}$ $S/cm^{-1}$). The high conductivity and low viscosity of PAMPSLi/emImTCM system is due to the high flexibility of imidazolium cation and dissociation of lithium cation from the polymer chains. The PAMPSLi/N,N-dimethyl-N-propyl-Nbutylammonium tricyanomethanide ($N_{1134}TCM$) and PAMPSLi/N, N-dimethyl-N-propyl-N-butylammonium dicyanamide ($N_{1134}DCA$) systems showed fairly high conductivity (6.3 $\times$ $10^{-4}$ $S/cm^{-1}$, 6.0 $\times$ 10.4 S/cm.1). PAMPSLi/Trihexyl (tetradecyl) phosphonium bis (trifluoromethane sulfonyl) amide ($P_{66614}TFSA$) exhibited low conductivity (2.22 $\times$ $10^{-5}$ $Scm^{-1}$) and thermally stable over 400$^{\circ}C$.

Electrochemical Properties of Lithium Sulfur Battery with Silicon Anodes Lithiated by Direct Contact Method

  • Kim, Hyung Sun;Jeong, Tae-Gyung;Kim, Yong-Tae
    • Journal of Electrochemical Science and Technology
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    • v.7 no.3
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    • pp.228-233
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    • 2016
  • It is hard to employ the carbon materials or the lithium metal foil for the anode of lithium sulfur batteries because of the poor passivation in ether-based electrolytes and the formation of lithium dendrites, respectively. Herein, we investigated the electrochemical characteristics of lithium sulfur batteries with lithiated silicon anode in the liquid electrolytes based on ether solvents. The silicon anodes were lithiated by direct contact with lithium foil in a 1M lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) solution in 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) at a volume ratio of 1:1. They were readily lithiated up to ~40% of their theoretical capacity with a 30 min contact time. In particular, the carbon mesh reported in our previous work was employed in order to maximize the performance by capturing the dissolved polysulfide in sulfur cathode. The reversible specific capacity of the lithiated silicon-sulfur batteries with carbon mesh was 1,129 mAh/g during the first cycle, and was maintained at 297 mAh/g even after 50 cycles at 0.2 C, without any problems of poor passivation or lithium dendrite formation.