• Proceedings of the Korean Fiber Society Conference
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• 1996.10a
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• pp.124-130
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• 1996

The hydrocarbons containing more than 10 carbons(0.1% of total volume, C10+), residue of aromatization from aliphatic hydrocarbons, were condensated in the presence of catalyst aluminumchloride and cocatalyst nitrobenzene(NB) to be pitchs with desirable properties. The properties of pitch were affected by the concentration of cocatalyst chosen 20 and 30wt.%. The pitch with 30wt.% NB showed higher carbon yield and lower crystallinity than that with 20wt.% NB. The two pitches were heat treated at 1000C and measured of charge/discharge capacity of the carbon as an anode. The carbon prepared at 20wt.% NB exhibited excellent cyclic stability with a capacity of 218mAh/.g and that at 30wt.% exhibited rather low cyclic stability with higher capacity of 235mAh/g.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.282-287
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• 2005

Palladium membranes, which are permselective to hydrogen separation, were used for the hydrogen purification and in membrane reactors for improving conversions by shifting the reaction equilibrium. Palladium/ceramic composite membranes were prepared by electroless plating technique and then etched in titanium chloride ($TiCl_4$) as a post treatment to enhance the membrane's durability. These membranes were used for membrane reactors in water gas shift (WGS) reaction. CO conversions for the membrane reactor were obtained according to experimental parameters and compared to the traditional reactor without a palladium/ceramic membrane. As a result, CO conversion using palladium membrane reactor at an appropriate condition was over 20~25% greater than that without the membrane reactor. The stability in the long-term test of up to 120 h for WGS reaction with the membrane reactor was good without the degredation of CO conversion.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.619-623
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• 1998

The influences of reaction temperature, HF/DCM mole ratio, contact time and catalyst type on activity and selectivity of difluoromethane synthesis via hydrofluoriation of dichloromethane over fluorinated catalyst have been studied. It has been found that fluorinated $Cr/Al_2O_3$ catalysts, show better performance compared to pure fluorinated $Al_2O_3$ catalyst and then, non-treated catalysts demonstrate better than catalysts pretreated with hydrogen and air. The results show that the optimum reaction conditions are found as follows : reaction temperature at $340^{\circ}C$, mole ratio of HF/DCM 5 or above and contact time 20 sec. or above. With these conditions the maximum attainable yield of difluoromethane has been found to be greater than 80%. In particular, the activity and the selectivity of difluoromethane do not change with the reaction time on stream up to 8 hours.

• Applied Chemistry for Engineering
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• v.33 no.4
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• pp.367-372
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• 2022

The effect of the addition of a polyvinylchloride (PVC) non-solvent to a PVC-tetrahydrofuran (THF) solution on the surface properties of the PVC thin film was analyzed. The non-solvents used were composed of alcohol-based and non-alcoholic ones. Surface morphologies of PVC thin films according to the addition of the non-solvent were compared. In addition, the hydrophobic properties relying on the surface characteristics were compared. The micro-bubbles generated in the preparation of PVC-THF solution affected the surface morphology of the thin film. In order to implement the normal surface physical properties of the coating thin film at the relatively high concentration of PVC-THF solution, the selection of appropriate drying method was required. When an alcohol-based non-solvent was added, a PVC thin film having a granular porous surface was obtained and exhibited super hydrophobic properties. The volume ratio of the PVC-THF solution to the non-solvent affects the surface shape of the coating thin film. The larger the amount of non-solvent was added, the more advantageous it was to form a super hydrophobic PVC thin film.

• Journal of the Korean Chemical Society
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• v.40 no.4
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• pp.243-248
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• 1996

New routes have been developed for the practical syntheses of dl-Muscone(1) employing cyclopentadecanone(2) as the starting material. In this experiment, addition of bromine to cyclopentadecanone in dried E. Ether solution with a trace of $AlCl_3$ as the catalyst were produced 2-bromocyclopentadecanone(3). This process was enhanced formation of regioselective enolate anion at $C_2$ position. 2-Bromocyclopentadecanone was put into $Li_2CO_3$-LiBr-DMF solution at 140∼150$^{\circ}C$, were produced trans- and cis-2-cyclopentadecen-1-one(4) mixture. Other by-products were reduced by control of reaction temperature and time. Trans- and cis-2-cyclopentadecen-1-one(4) mixture was directly put into dried E. Ether solvent and induce to react dropwise with $CH_3MgBr-Cu_2Cl_2$ complex, all of them got into 1,4-addition, dl-Muscone (1) was formed as the result. Conculsion, through three steps procedure from cyclopentadecanone(2) to dl-Muscone(1), the pure dl-Muscone was obtained with the high proportion of 85%, and synthetic cost was able to be much lower than any other conventional methods as there were no chemical separating steps.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.394-402
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• 2013

The new complex catalysts were synthesized by the reaction of titanium compounds (titanium chloride or titanium butoxide) and diamines in this work, and they showed very high catalytic activities for the cyclododecatriene (CDT) synthesis from 1,3-butadiene through trimerization. CDT synthetic reaction was performed in an autoclave reactor, and the effects of reaction temperature, type of catalyst, catalyst amount added into the system, the mole ratio of Al/Ti and immobilization method were investigated on the yield of product CDT. The titanium complex catalyst combined to diamine with 1:1 ratio showed high selectivity to CDT more than 90%. The ratio of TTT-CDT/TTC-CDT isomers in the product revealed as different values, depending on the type of diamine combined to titanium and Ti/diamine ratios. Those homogeneous complexes could be used as a heterogenized catalyst after anchoring on the supports, and the immobilized titanium catalyst retained the catalytic activities for several times in the recycled reactions without leaching. The carbon support containing titanium has exhibited superior activity to the silica support. Especially, when the titanium complex was anchored on the support which was fabricated by the hydrolysis of tripropylaminosilane itself, the resulting titanium catalyst showed the highest BD conversion and CDT selectivity.

• Resources Recycling
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• v.32 no.1
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• pp.21-32
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• 2023

Because the application of lithium has gradually increased for the production of lithium ion batteries (LIBs), more research studies about recycling using solvent extraction (SX) should focus on Li⁺ recovery from the waste solution obtained after the removal of the valuable metals nickel, cobalt and manganese (NCM). The raffinate obtained after the removal of NCM metal contains lithium ions and other impurities such as Na ions. In this study, we optimized a selective SX system using di-(2-ethylhexyl) phosphoric acid (D2EHPA) as the extractant and tri-n-butyl phosphate (TBP) as a modifier in kerosene for the recovery of lithium from a waste solution containing lithium and a high concentration of sodium (Li⁺ = 0.5 ~ 1 wt%, Na⁺ = 3 ~6.5 wt%). The extraction of lithium was tested in different solvent compositions and the most effective extraction occurred in the solution composed of 20% D2EHPA + 20% TBP + and 60% kerosene. In this SX system with added NaOH for saponification, more than 95% lithium was selectively extracted in four extraction steps using an organic to aqueous ratio of 5:1 and an equilibrium pH of 4 ~ 4.5. Additionally, most of the Na⁺ (92% by weight) remained in the raffinate. The extracted lithium is stripped using 8 wt% HCl to yield pure lithium chloride with negligible Na content. The lithium chloride is subsequently treated with high purity ammonium bicarbonate to afford lithium carbonate powder. Finally the lithium carbonate is washed with an adequate amount of water to remove trace amounts of sodium resulting in highly pure lithium carbonate powder (purity > 99.2%).

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.621-629
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• 2016

Recently, the researches on quantitative structure activity relationship (QSAR) for describing toxicities or activities of chemicals based on chemical structural characteristics have been widely carried out in order to estimate the toxicity of chemicals in multiuse facilities. Because the toxicity of chemicals are explained by various kinds of molecular descriptors, an important step for QSAR model development is how to select significant molecular descriptors. This research proposes a statistical selection of significant molecular descriptors and a new QSAR model based on partial least square (PLS). The proposed QSAR model is applied to estimate the logarithm of partition coefficients (log P) of 130 polychlorinated biphenyls (PCBs) and lethal concentration ($LC_{50}$) of 14 PCBs, where the prediction accuracies of the proposed QSAR model are compared to a conventional QSAR model provided by OECD QSAR toolbox. For the selection of significant molecular descriptors that have high correlation with molecular descriptors and activity information of the chemicals of interest, correlation coefficient (r) and variable importance of projection (VIP) are applied and then PLS model of the selected molecular descriptors and activity information is used to predict toxicities and activity information of chemicals. In the prediction results of coefficient of regression ($R^2$) and prediction residual error sum of square (PRESS), the proposed QSAR model showed improved prediction performances of log P and $LC_{50}$ by 26% and 91% than the conventional QSAR model, respectively. The proposed QSAR method based on computational toxicology can improve the prediction performance of the toxicities and the activity information of chemicals, which can contribute to the health and environmental risk assessment of toxic chemicals.

• Journal of Korea Foundry Society
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• v.43 no.5
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• pp.230-240
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• 2023

The pitting corrosion behavior of 329LD cast lean duplex stainless steel and CF3M cast austenitic stainless steel was investigated in chloride environments. The pitting corrosion resistance of the 329LD alloy was superior to that of the CF3M alloy because the pitting potential, passive region, and critical pitting temperature of the low Ni-low Mo 329LD alloy were higher than those of the high Ni-medium Mo commercial CF3M alloy. There are two main reasons for the enhancement of the pitting corrosion resistance of high Cr-low Momedium N 329LD alloy compared to the low Cr-medium Mo CF3M alloy: First, the pitting resistance equivalent number (PREN_δ+γ) value of the 329LD alloy is higher than that of the CF3M alloy. Second, the passive region of the 329LD alloy is larger than that of the CF3M alloy. It indicates that the synergistic effect of the three elements by adding high Cr and low Mo-medium N to the 329LD alloy enhances the passivity of the passive film, thereby increasing the pitting corrosion resistance. It was verified that based on the PREN_γ of austenite (γ) and PREN_δ of ferrite (δ) values calculated using an N-factor of 16, the pitting corrosion of the 329LD alloy was selectively initiated at the γ-phases because PREN_γ value of austenite (γ) was smaller than that of ferrite (δ), and finally propagated from the γ-phase to the δ-phase.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.229-229
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• 1994

선택성이 높고 뛰어난 약효를 지닌 항 바이러스제의 개발은 신약개발의 중요한 영역중에 하나이다. 현재 AIDS 치료제로 사용되고 AZT를 비롯하여 항virus 효과를 나타내는 약물의 대부분은 구조적으로 nucleoside계에 속하는 화합물로서 수 많은 약리학적 연구 및 합성 화학적 연구가 이루어져 왔다. 특히 합성 화학적 측면에서 이들 화합물의 합성은 크게 두가지로 나누어지는데 그것은 sugar 부위의 변형을 통한 방법과 염기 부위의 변형을 통한 방법에 의해 새로운 항 바이러스제를 개발하는 것이다. 최근의 연구 동향에 있어서 주목할 만한 변화의 하나는 sugar 부위의 구조적 변형을 시도하는데 있어서 종래의 5원환 형태에서 환이 개열된 형태의 acyclic nucleoside에 대한 연구가 이루어져 좋은 효과를 거두고 인다는 사실이다. Acyclovir, Ganciclovir등 의 개발이 그것이다. 본 연구에서는 종래의 acyclic nucleoside가 ribose sugar의 2'번 및 3'번 탄소를 제거한 acyclic ether 형태로 되어있는 것과는 다르게 ether 부위의 산소를 탄소 치환한 carbo-acyclic nucleoside를 합성하고자 하였다. Acyclic nucleoside를 합성하고자 하였다. Acyclic nucleoside의 side chain의 conformation이 항 바이러스 작용을 나타내는데 필수 불가결한 점을 감안할때, carbo-acyclic nucleoside계 화합물은 보다 다양하게 변형될 수 있는 장점을 가지고 있다. 이러한 관점에서 side chain의 2'번 및 3'번 탄소는 side chain의 conformation을 좌우하는 결정적 요인으로 작용할 것으로 판단된다. 따라서 본 연구에서는 이들 탄소를 중심으로한 분자수식을 시도하기로 하고 bioisosterism을 이용하여 3'위치의 수소를 fluoride로 치환한 화합물을 설계하여 합성을 시도하였다.silyl group-5'-무치환 화합물을 tosyl, azido화 한다음 desilylation하여 얻었다. 목적하는(1) 화합물의 diasteromer 인 2',3'-dihydroxy-5'-무치환 유도체(3)는 (4)화합물 합성시 얻은 hemiactal을 key intermediate로 하여 TsNHNH$_2$, NaB(CN)H$_3$ 및 NaOAc로 처리하므로서 얻을수 있었다. 이들 화합물들의 각종 DNA 및 RNA virus에 대한 항 바이러스작용을 검토한 결과 현저한 항 바이러스 작용을 나타내지 않았다.분화유도 활성을 나타내어 항종양제로의 개발에 많은 흥미가 기대된다.기대된다.oxylic acid (compound 10)를 합성하였다.10^{－7}$ M)에 의한 단백인산화에 대하여는 더 미약한 억제-효과를 나타내었다. 이상의 결과는 PDE-1과 항우울약들의 항혈소판작용은 PKC-기질인 41-43 kD와 20 kD의 인산화를 억제함에 기인되는 것으로 사료된다.다. 것으로 사료된다.다.바와 같이 MCl에서 작은 Dv 값을 갖는데, 이것은 CdCl$_{4}$$^{2-}$ 착이온을 형성하거나 ZnCl$_{4}$$^{2-}$ , ZnCl$_{3}$$^{-}$같은 이온과 MgCl$^{+}$, MgCl$_{2}$같은 이온종을 형성하기 때문인것 같다. 한편 어떠한 용리액에서던지 NH$_{4}$$^{+}$의 경우 Dv값이 제일 작았다. 바. 본 연구의 목적중의 하나인 인체유해 중금속이온인 Hg(II), Cd(II)등이 NaCl같은 염화물이 함유된 시료용액에 공해이온으로 존재할 경우 흡착에 의한 제거가 가능하다. 한편 이같은 중금속이온의 흡착실험은 특히 해수중의 금속이온의 회수연구에도