• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.126-126
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• 2017

Using first principles calculations we unveil fundamental mechanism of hydrolysis reactions of two hazardous chemicals $PCl_3$ and $POCl_3$ with molecular water clusters nearby. It is found that the water molecules play a key role as a catalyst significantly lowing the activation barriers by transferring its protons to the reaction intermediates. Interestingly, torsional angles of molecular complexes at transition states are identified as a vital descriptor on the reaction rate. Analysis of charge distribution over the complexes further reinforces the finding with atomic level correlation between the torsional angle and variation of the orbital hybridization state of P in the complex. Electronic charge separation (or polarization) enhances thermodynamic stability of the activated complex at transition state and reduces the activation energy through hydrogen bonding network with water molecules nearby. Calculated potential energy surfaces (PES) for the hydrolysis reactions of $PCl_3$ and $POCl_3$ depict their two contrastingly different profiles of double- and triple-deep wells, respectively. It is ascribed to the unique double-bonding O=P in the $POCl_3$. Our results on the activation free energy show well agreements with previous experimental data within $7kcalmol^{-1}$ deviation.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.149-149
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• 2009

Generally, Nafion ionomer is used in the polymer electrolyte fuel cell (PEFC) electrodes to achieve high power density. At the high temperature operation of PEFC, however, ionic conductivity of Nafion remarkably decreased due to the evaporation of water in Nafion polymer. Recently, many researchers have focused on using the Ionic Liquids(ILs) instead of water in Nafion polymer. ILs have intrinsic properties such as good electrochemical stability, high ionic conductivity, and non-flammability. Especially, ILs play a crucial role in proton conduction by the Grottuss mechanism and act as water in water-free Nafion polymer. However, it was found that the ILs was leached out of the polymer matrix easily. In this study, we prepared membrane electrode assemblies with various contents of ILs. The effect of ILs in the electrode of each designed was investigated by a cyclic voltammetry measurement and the cell performance obtained through a single cell test using H2/Air gases. Electrodes with different contents of ILs in catalyst layer were examined at high temperature and low humidified condition.

• 한국수소및신에너지학회논문집
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• 제13권3호
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• pp.214-223
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• 2002

Kinetic and effectiveness factors for methanol steam reforming using commercial copper-containing catalysts in a plug flow reactor were investigated over the temperature ranges of $180-250^{\circ}C$ at atmospheric pressure. The selectivity of $CO_2$/$H_2$ was almost 100%, and CO products were not observed under reaction conditions employed in this work. It was indicated that $CO_2$ was directly produced and CO was formed via the reverse water gas shift reaction after methanol steam reforming. The intrinsic kinetics for such reactions were well described by the Langmuir-Hinshelwood model based on the dual-site mechanism. The six parameters in this model, including the activation energy of 103kJ/mol, were estimated from diffusion-free data. The significant effect of internal diffusion was observed for temperature higher than $230^{\circ}C$ or particle sizes larger than 0.36mm. In the diflusion-limited case, this model combined with internal effectiveness factors was also found to be good agreement with experimental data.

• Macromolecular Research
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• 제17권8호
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• pp.557-562
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• 2009

The free radical polymerization of styrene was initiated with azobis(isobutyronitrile) in the presence of benzene sulfonyl chloride. Analysis of the terminal structures of the obtained polystyrene with $^1H$ NMR spectroscopy revealed the presence of a phenyl sulfonyl group at the ${\alpha}$-end and a chlorine atom at the ${\omega}$-end of each polystyrene chain. The terminal chlorine atom in the polystyrene chains was further confirmed through atom transfer radical polymerization (ATRP) of styrene and methyl acrylate using the obtained polystyrenes as macroinitiators and CuCl/2,2'-bipyridine as the catalyst system. GPC traces of the products obtained in ATRP at different reaction times were clearly shifted to higher molecular weight direction, indicating that nearly all the macroinitiator chains initiated ATRP of the second monomers. In addition, the number-average molecular weights of the polystyrenes increased directly proportional to the monomer conversions, and agreed well with the theoretical ones.

• Bulletin of the Korean Chemical Society
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• 제8권2호
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• pp.102-105
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• 1987

2-Methoxy-6-methyl-3,4-dihydro-2H-pyran ($1_a$), 2-ethoxy-3,6-dimethyl-3,4-dihydro-2H-pyran ($1_b$), and 2-ethoxy-3-methyl-6-ethyl-3,4-dihydro-2H-pyran ($1_c$) were prepared by (4 + 2) cycloaddition reaction from the corresponding vinyl ketones and alkyl vinyl ethers. Compounds $1_{a-c}$ were ring-open polymerized by cationic catalyst to obtain alternating head-to-head (H-H) copolymers. For comparison, copolymer of head-to-tail (H-T) was also prepared by free radical copolymerization of the mixture of the corresponding monomers. The H-H copolymer exhibited some differences in its $^1H$ NMR and IR spectra. However, significant differences were showed between the H-H and H-T copolymers in the $^{13}C$ NMR spectra. Also noteworthy was that$T_g$ value of H-H copolymer was higher than that of the corresponding H-T structure. Decomposition temperature of the H-H copolymer was lower than that of the H-T copolymer. All the H-H and H-T copolymers were soluble in common solvents.

• Bulletin of the Korean Chemical Society
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• 제22권7호
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• pp.669-672
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• 2001

Pseudo-first-order rate constants have been measured spectrophotometrically for the title reactions. The plot of kobs vs the concentration of alkali metal ethoxides is linear for the reactions performed in the presence of complexing age nt, 18-crown-6 ether, but curved upwardly for the corresponding reactions performed in the absence of the complexing agent, indicating that the alkali metal ions studied in this study behave as a catalyst. The catalytic effect was found to increase in the order Li+ << K+ ${\leq}$ Na+. Second-order rate constants were determined for the reactions with dissociated free ethoxide (kEtO-) and with ion paired alkali metal ethoxides (kEtO-M+ ) from ion pairing treatments. The magnitude of catalytic effect (kEtO-M+/kEtO-) was found to be 2.3, 9.5 and 8.7 for the reaction of 8-(5-nitroquinolyl) 2-furoate, while 1.4, 3.6 and 4.2 for that of 4-nitrophenyl 2-furoate, indicating that the catalytic effect is larger in the reaction of the former substrate than in that of the latter one. The larger catalytic effect was attributed to two possible complexing sites with alkali metal ions in the former substrate.

• Corrosion Science and Technology
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• 제21권6호
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• pp.514-524
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• 2022

Carbon emissions from fuel consumption have been pointed by scientists as the cause of global warming. In particular, fossil fuels are known to emit more carbon when burned than other types of fuels. In this regard, International Maritime Organization has announced a regulation plan to reduce carbon dioxide emissions. Therefore, recently, Liquefied Natural Gas propulsion ships are responding to such carbon reduction regulation. However, from a long-term perspective, it is necessary to use carbon-free fuels such as hydrogen and ammonia. Nitrogen oxides might be generated during ammonia combustion. There is a possibility that incompletely burned ammonia is discharged. Therefore, rather than being used as a direct fuel, Ammonia is only used to reduce NO_X such as urea solution in diesel vehicle Selective Catalyst Reduction. Currently, LPG vehicle fuel feed system studies have evaluated the durability of combustion injectors and fuel tanks in ammonia environment. However, few studies have been conducted to apply ammonia as a ship fuel. Therefore, this study aims to evaluate corrosion damage that might occur when ammonia is used as a propulsion fuel on ships.

• Korean Chemical Engineering Research
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• 제47권6호
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• pp.762-767
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• 2009

해외 열대작물 씨앗에서 추출한 식물성 오일을 이용하여 바이오디젤을 생산하고 물성분석을 통해 차량연료로서의 사용가능성을 검토하는 연구를 수행하였다. 유리지방산 함량이 높은 열대작물 오일의 효율적인 바이오디젤 생산을 위해서는 유리지방산을 산촉매로 에스테르화한 후 전이에스테르화 반응하는 2단계 반응공정의 적용이 필요하였다. 전처리(에스테르화) 반응에 적합한 촉매를 선정하기 위해 3가지 산 촉매의 비교실험 수행 결과 황산이 최적 촉매임을 확인하였고, 반응표면분석법(response surface method, RSM)에 의해 도출한 최적 반응조건은 황산 촉매 0.982%와 메탄올 26.7%로 나타났다. 전이에스테르화 반응에 대한 최적화 실험을 반응표면분석법에 근거하여 수행하고, 결과로 KOH 촉매 1.24%, 메탄올 22.76%로 확인되었지만 본 연구팀의 선행 실험의 반응조건(KOH 0.8%)보다 과량의 촉매가 투입된 것으로 나타났다. 이에 대한 확인실험으로 메탄올과 촉매 투입량에 대한 추가 실험을 수행하였으며, 그 결과로서 최적 반응조건으로 KOH 촉매 0.8%와 메탄올:오일 몰비 6.2:1로 도출하였으며 반응생성물의 분석결과 지방산 메틸에스테르(fatty acid methyl ester, FAME) 100.8%, 산가 0.45 mgKOH/g, 수분 0.00%, 산화안정성 0.70 h, 총 글리세롤 함량 0.04%, Mono-glyceride 함량 0.04%, Di-glyceride 함량 0.01%, Tri-glyceride 함량 0.00%, 동점도($40^{\circ}C$에서) $4.041mm^2/s$, 저온필터막힘점 $1.0^{\circ}C$로 주요 바이오디젤 품질규격을 만족하는 것으로 나타났다.

• 청정기술
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• 제30권1호
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• pp.47-54
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• 2024

비식용 작물인 네팔산 Jatropha 씨앗으로부터 추출한 식물성 오일을 원료로 사용하고, 에스테르화 반응과 전이에스테르화 반응으로 구성된 2-step 공정을 거쳐서 바이오디젤로 전환하였다. Jatropha 오일에 함유되어 있는 유리지방산과 메탄올과의 에스테르화 반응에 Amberlyst-15 촉매를 적용하였으며, 자트로파 오일의 산가를 11.0으로부터 0.26 mgKOH/g까지 낮추었다. 산가가 0.26 mgKOH/g인 Jatropha 오일과 메탄올을 원료로 사용하고 NaOH/γ-Al₂O₃ 촉매를 사용하여 전이에스테르화 반응을 통해서 바이오디젤을 제조하였다. NaOH 담지량이 3 wt%에서 25 wt%로 증가함에 따라 비표면적은 129 m²/g에서 28 m²/g으로, 기공 부피는 0.249 m³/g에서 0.129 cm³/g으로 감소하였다. 또한, NaOH의 담지량이 증가할수록 NaOH/γ-Al₂O₃ 촉매의 염기점의 양과 세기가 동시에 증가하였다. NaOH/γ-Al₂O₃ 촉매의 최적 NaOH 담지량은 12 wt%인 것을 확인하였다. NaOH/γ-Al₂O₃ 촉매를 이용한 Jatropha oil의 전이에스테르화 반응에서 최적 온도를 65 ℃로 선정하였다. 교반속도가 150 RPM 이하의 조건에서는 전이에스테르화 반응 속도가 외부 물질 전달의 영향을 받았으나, 그 이상의 교반속도에서는 외부 물질 전달의 영향이 크지 않았다.

• 대한환경공학회지
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• 제22권2호
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• pp.241-249
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• 2000

난분해성 폐수인 사진현상폐수의 $UV/H_2O_2$ 및 $H_2O_2$의 고급산화에 의한 오염물질의 제거 실험을 실시하였다. $UV/H_2O_2$ 산화에서 $H_2O_2$의 분해로 $OH^-$ 라디칼이 발생되는데 파장 190~300 nm의 UV가 반응의 촉매 역할을 한다. $OH^-$ 라디칼은 수명은 짧으나 강력한 산화력을 갖고 있는데, 이 산화력은 폐수처리에서 폐수나 액상 폐기물의 유기물질을 제거하는데 이용된다. 본 연구에서 기존의 tube형 반응조의 단점을 보완한 UV-자유반사 반응조를 제작하여 사용하였으며 UV원으로는 수은 고압램프가 이용되었다. 본 실험에서는 반응시간과 $H_2O_2$ 주입량 및 pH 변화에 따른 오염물의 처리효율의 변화를 조사하였는데 $H_2O_2$의 주입량이 증가할수록 처리효율이 높았으나 그 차이는 미미하였으며, pH 8에서 보다는 3에서 처리효율이 약간 높았으나 그 차이 역시 크지 않았다. 본 연구에서 사진현상폐수 처리의 적정 운전조건은 pH 8, $H_2O_2$ 주입량은 유입수의 COD를 기준으로 한 1.3배 화학량론적 주입으로 나타났는데, 5시간의 처리에서 $COD_{Cr}$, TOC 및 색도의 제거효율은 각각 약 47.5%, 75.0% 및 91.5%로 나타났다. 반응 후 생분해성의 지표인 BOD/COD 비는 초기 0.04에서 0.21로 약 5.3배 증가하였다.