• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.694-699
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• 1997

Normal-phase HPLC was used to separate the useful phospholipids, PE, PI and PC in soybean lecithin. The mobile phase used in this experiments were haxane, isopropanol and methanol, the gradient mode was applied as the three components could not be separated by the isocratic mode. To find the optimum separation condition, the concentration profiles of effluents were calculated from the plate theory and the capacity factor in step-gradient mode. From the calculated results, PE was separated with hexane/isopropanol/methanol = 90/5/5vol.% in isocratic mode and PI and PC were resolved in the conditions of 10min gradient time and the second mobile phase of hexane/isopropanol/methanol=50/20/30vol.% in step-gradient mode. The agreement between the calculated concentration profile and experimental data was good, so the methodology developed in this work can be used to obtain the optimum separation condition in gradient mode.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.265-272
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• 2023

Lignocellulosic biomass is essential to pretreatment because of having rigid structures and a lot of lignin. Among methods of pretreatment, using THF solvents has the advantage of being easy to reuse. THF (Tetrahydrofuran) used as a co-solvent with water or ionic solvent that is inexpensive and can remove lignin over a wide range of reaction conditions. NaOH (Sodium hydroxide) has been demonstrated to preferentially solvate lignin from cellulose. Thus, NaOH was used as a pretreatment co-solvent for the fractionation of lignin by destroying the ether bond to amend for hydrolysis and expand the surface area of cellulose and hemicellulose. In this experiment, lignin was removed by the NaOH/THF co-solvent pretreatment process to characteristics for the pretreatment and obtain the optimal levulinic acid conversion yield through the acid catalyst conversion process. the NaOH/THF co-solvent system was conducted in various ratios of co-solvent under a total of 16 conditions. And the temperature was 180 ℃ during to 60 mins. The optimum condition of co-solvent is NaOH 5 wt%/THF 90:10(v/v%), 76.8% glucan content was obtained through this co-solvent pretreatment, and 90.1% lignin was removed. In the acid catalyst conversion process, which is a subsequent pretreatment process, the experiment was conducted under the conditions of 30 to 90 min of reaction time and 160 ℃ to 200 ℃ reaction temperature. The optimum condition of acid catalyst conversion process is 60min reaction time under of 180 ℃, and it obtained 84.7% of levulinic aicd conversion yield.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.433-437
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• 2013

Electrical discharge plasma created in a multi-channel porous ceramic membrane-supported catalyst was applied to the decomposition of a volatile organic compound (VOC). For the purpose of improving the oxidation capability, the ceramic membrane used as a low-pressure drop catalyst support was loaded with zinc oxide photocatalyst by the incipient wetness impregnation method. Alternating current-driven discharge plasma was created inside the porous ceramic membrane to produce reactive species such as radicals, ozone, ions and excited molecules available for the decomposition of VOC. As the voltage supplied to the reactor increased, the plasma discharge gradually propagated in the radial direction, creating an uniform plasma in the entire ceramic membrane above a certain voltage. Ethylene was used as a model VOC. The ethylene decomposition efficiency was examined with experimental variables such as the specific energy density, inlet ethylene concentration and zinc oxide loading. When compared at the identical energy density, the decomposition efficiency obtained with the zinc oxide-loaded ceramic membrane was substantially higher than that of the bare membrane case. Both nitrogen and oxygen played an important role in initiating the decomposition of ethylene. The rate of the decomposition is governed by the quantity of reactive species generated by the plasma, and a strong dependence of the decomposition efficiency on the initial concentration was observed.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.321.1-321.1
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• 2013

높은 광흡수 계수를 갖는 Cu(In,Ga)Se2(CIGS) 화합물 박막 소재는 고효율 태양전지 양산을 위해 가장 전도유망한 재료이나 상대적으로 매장량이 적은 In 및 Ga을 사용한다는 소재적 한계가 있다. Cu2ZnSnSe4(CZTSe) 혹은 Cu2ZnSnS4(CZTS)와 같은 Cu-Zn-Sn-Se계 화합물 반도체는 CIGS 내 희소원소인 In과 Ga이 범용원소인 Zn 및 Sn으로 대체된 소재로써 미래형 저가 태양전지 개발을 위해 활발히 연구되고 있는데, 그 화합물 조합에 따라 0.8eV부터 1.5eV까지의 에너지 밴드갭을 갖는 것으로 알려져 있다. 본 연구에서는 열분해법으로 CZTS 나노 입자를 합성하였다. 용매로 Oleylamine을 사용하였는데, $260{\sim}340^{\circ}C$의 온도 범위에서 5시간 30분 동안 CZTS 나노입자를 합성하였고, $300^{\circ}C$에서 5시간 30분~9시간까지 합성하였다. 헥산을 이용하여 원심분리기와 초음파세척기로 용매인 Oleylamine을 제거하였고, 진공오븐에서 건조된 CZTS 분말의 FE-SEM (Field Emission Scanning Electron Microscope), XRD (X-Ray Diffraction), EDS (Energy Dispersive Spectroscopy) 분석 등을 통해 합성온도에 따른 구조적, 화학적 조성 변화를 조사하였다.

• Journal of the Korean Magnetics Society
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• v.11 no.6
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• pp.256-261
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• 2001

These experiments were carried out to examine the effects of element substitution of Zn and La-Zn for Sr-ferrite. The calcined properties of Zn and La-Zn element substitution were examined, and also the sintered magnetic properties were compared with the stoichiometric condition. The magnetization properties of calcined SrM materials is as follows; M$\_$s/ : 61.06 emu/g. Also, the magnetization properties of calcined Zn$\_$0.3/-SrM materials is as follows; M$\_$s/ : 66.90 emu/g. The sintered magnetic properties of (La-Zn)$\_$0.3/-SrM composition is as follows; B$\_$r/ : 4.21 kG, BH$\_$max/: 4.19 MGOe.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.286-291
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• 1997

Taxol which is recognized as a powerful anticancer reagent was extracted from yew extract and separated by NP-HPLC (Normal-PhaseHigh Performance Liquid Chromatography). The experiments were performed in the isocratic mode with $5{\mu}l$ to $100{\mu}l$ injection volume and 1ml/min mobile phase flow rate. The major mobile phase was hexane and small amounts of ethanol, methanol, 1-propanol and isopropanol were added to change the retention behavior. Prior to a real sample, the artificial mixture of taxol, cephalomannine and 10-deacetyltaxol was tested. They are hard to be separated because of similar chemical structures. The experimental results showed that the proper composition of mobile phase for separating the three components was found 96% hexane and 4% ethanol(vol.%) or 96% hexane, 2% 1-propanol and 2% methanol(vol.%). Compared to the run time of 80 minutes for the binary system, the mixture was separated within 50 minutes with the less amount of mobile phase for the ternary system. Finally, $1{\mu}g$ of taxol was separated from yew tree extracts under the optimum operating conditions.

• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.136-141
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• 2007

The decomposition of chlorinated methanes including $CCl_4$, $CCl_3H$, and $CCl_2H_2$ was carried out using a thermal plasma process and the characteristics of the process were investigated. The thermal equilibrium composition was analyzed with temperature by Fcatsage program. The decomposition rates at various process parameters including the concentration of reactants, flow rate of carrier gas, and quenching rate, were evaluated, where sufficiently high conversion over 92% was achieved. The generation of main products was strongly influenced by the reaction atmosphere; carbon, chlorine, and hydrogen chloride at neutral condition; carbon dioxide, chlorine, and hydrogen chloride at oxidative condition. The decomposition mechanism was speculated considering the results from Factsage and the identification of generated radicals and ionic species. The main decomposition pathways were found to be dissociative electron attachment and oxidative by radicals formed in a plasma state.

• Applied Chemistry for Engineering
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• v.2 no.4
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• pp.393-398
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• 1991

An experimental reactor system was devised and employed to examine catalytic coal gasification. A 4-kw tungsten halogen lamp heater combinded with a graphite sample basket coated with silicon nitride film made rapid heating and cooling possible. Also a small graphite cap on the thermocouple tip which located just beneath the sample basket helped remarkably to read real temperatures. Silicon nitride film on the basket and the cap showed very good protection against the reaction between graphite and oxidant gases during the experiments. The weight of specimen could be continuously measured without disturbance.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.294-299
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• 1998

To prove pseudo-homopolymerization(PHP) method indirectly for general system which includes more than one growing radicals per particle, Mayo-Lewis equation of bulk copolymer system was derived form probability equation about instantaneous copolymer composition of emulsion copolymer system during interval II. From Extended Smith-Ewart equation proposed by Ballard et al. in emulsion copolymerization, exact solution was obtained for 0-1 system (i.e., the system containing no more than one growing radical per particle). From the exact solution, average number of radicals per particle and instantaneous copolymer composition were predicted to reach the steady state which a few minutes. So the reliability of this approximation method could by proved directly for 0-1 system. Styrene-butadiene(St-Bu) and Styrene-methyl methacrylate (St-MMA) system were used for model calculations.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.749-754
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• 2005

For the binary system of methanol/3-methyl-1-butanol mixture vapor-liquid equilibrium data were measured isothermally at 50, 55, 60, 65, and $70^{\circ}C$. An empirical relation to predict vapor-liquid equilibrium data was obtained from the above measured data. The predicted values compared with the measured ones were in a good agreement, within accuracy ${\pm}0.0007$. The excess molar volume, measured for the binary system of methanol/3-methyl-1-butanol mixture, was positive $V^Eover$ the entire composition range. The maximum values were shown to be about $0.096cm^3/mol$ at x= 0.683.