• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.553-557
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• 2014

Sulfonated polypropylene (S-PP) is prepared by sulfuric acid-acetone aldol condensation reaction of polypropylene (PP) separator to yield hydrophilic separator surface with a moderate amount of $-SO_3H$ groups. Activated carbon supercapacitor is also fabricated adopting the S-PP separator coated with potassium polyacrylate (PAAK) hydrogel polymer electrolyte. As a result, the hydrophilic surface of S-PP separator involves better physical and electrochemical properties such as decrease in contact angle, improvements of wettability, electrolyte uptake, and ionic conductivity to give higher specific capacitance and long cycle-life.

• Journal of Energy Engineering
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• v.20 no.1
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• pp.36-43
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• 2011

Plant biomass has been proposed as an alternative source of petroleum-based chemical compounds. Especially, aromatic chemical compounds can be obtained from lignin by depolymerization processes because the lignin consist of complex aromatic materials. In this study, kraft lignin, the largest emitted substance among several kinds of lignin in Korea, was used as a starting material and was characterized by solid-state $^{13}C$-Muclear Magnetic Resonance($^{13}C$-NMR), Fourier Transform Infrared Spectroscopy(FT-IR), Elemental Analysis(EA). The depolymerization of kraft lignin was studied at water-phenol mixture solvent in near critical region and the experiments were conducted using a batch type reactor. The effects of water-to-phenol ratio and reaction temperature($300-400^{\circ}C$) were investigated to determine the optimum operating conditions. Additionally, the effects of formic acid as a hydrogen-donor solvent instead of $H_2$ gas were examined. The chemical species and quantities in the liquid products were analyzed using gas chromatography-mass spectroscopy(GC-MS), and solid residues(char) were analyzed using FT-IR. GC-MS analysis confirmed that the aromatic chemicals such as anisole, o-cresol(2-methylphenol), p-cresol(4-methylphenol), 2-ethylphenol, 4-ethylphenol, dibenzofuran, 3-methyl cabazole and xanthene were produced when phenol was added in the water as a co-solvent.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.214-220
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• 2013

Hydrophobic coating on a silicate-based yellow phosphor ($Sr_2SiO_4:Eu^{2+}$) was carried out by using hexamethyldisiloxane (HMDSO) precursor in an atmospheric pressure dielectric barrier discharge plasma reactor, eventually to improve the long-term stability and reliability of the phosphor. The phosphor powder samples were characterized by a scanning electron microscope (SEM), a transmission electron microscope (TEM), a fluorescence spectrophotometer and a contact angle analyzer. After the coating was prepared, the contact angle of the phosphor powder increased to $133.0^{\circ}$ for water and to $140.5^{\circ}$ for glycerol, indicating that a hydrophobic layer was formed on its surface. The phosphor coated with HMDSO exhibited photoluminescence enhancement up to 7.8%. The SEM and TEM images of the phosphor powder revealed that the plasma coating led to a morphological change from grain-like structure to smooth surface with 31~46 nm thick hydrophobic layer. The light emitting diode (3528 1 chip LED) fabricated with the coated phosphor showed a substantial enhancement in the reliability under a special test condition at $85^{\circ}C$ and 85% relative humidity for 1,000 h (85/85 testing). The plasma-mediated method proposed in this work may be applicable to the formation of 3-dimensional coating layer on irregular-shaped phosphor powder, thereby improving the reliability.

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.612-620
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• 2016

Aqueous mineral carbonation process, in which $CO_2$ is captured through the reaction with aqueous calcium oxide (CaO) solution, is one of CCU technology enabling the stable sequestration of $CO_2$ as well as economic value creation from its products. In order to enhance the carbon capture efficiency, it is required to maximize the dissolution rate of solid reactants, CaO. For this purpose, the proper design of a reactor, which can achieve the uniform distribution of solid reactants throughout the whole reactor, is essential. In this paper, the effect of internal reactor designs on the solid dispersion quality is studied by using CFD (computational fluid dynamics) techniques for the pilot-scale reactor which can handle 40 ton of $CO_2$ per day. Various combination cases consisting of different internal design variables, such as types, numbers, diameters, clearances and speed of impellers and length and width of baffles are analyzed for the stirred tank reactor with a fixed tank geometry. By conducting sensitivity analysis, we could distinguish critical variables and their impacts on solid distribution. At the same time, the reactor design which can produce solid distribution profile with a standard deviation value of 0.001 is proposed.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.320-324
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• 2011

TOPO/TOP capped CdSe nanoparticles were synthesized via thermal-solvent method. The 540 nm green and 620 nm red emitting CdSe nanoparticles were obtained by controlling the reaction time and temperature. Phosphor conversion white LED was produced combining a 460 nm emitting InGaN LED chip as an excitation source with 540 and 620 nm CdSe nanoparticles as phosphors. The single or double phosphor layer was fabricated by mixing with epoxy, and investigated the effects on the luminous properties of the white LED. The single phosphor layer white LED showed 5.78 lm/W with CIE of (0.36, 0.45) in reddish white, and the double phosphor layer white LED showed 7.28 lm/W with that of (0.32, 0.34) in pure white at 20 mA. When the 400 nm near-UV LED was applied to optical pumping source, the luminous efficiency of white LED was enhanced to 8.76 lm/W.

• Journal of Marine Bioscience and Biotechnology
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• v.7 no.1
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• pp.1-10
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• 2015

Bio diesel has advantages to reduce GHG(Greenhouse Gas) compare with the fossil fuel by using oil comes from plant/animal sources and even waste such as used cook oil. The diversity of energy feeds brings the positive effects to secure the national energy mix. In this circumstance, micro-algae is one of the prospective source, though some technical barriers. We analyzed the bio diesel which was derived from Dunaliella tertiolecta LB999 through the BD100 quality specifications designated by the law. From that result, it is revealed that the oxidation stability is one of the properties to be improved. In order to find the reason for low oxidation stability, we analyzed the oxidation tendency of each FAME components through some methods(EN 14111, EN14112, EN16091). In this study, we could find the higher double bond FAME portion, the more oxidative property(C18:1${\ll}C18:3$) in bio diesel and main unsaturated FAME group is acted as the key component deciding the bio diesel's oxidation stability. It is proved experimentally that C18:3 FAME are oxidized easily under the modified accelerated oxidation test. We also figure out low molecular weight hydrocarbon and FAME were founded as a result of thermal degradation. Some alcohol and aldehydes were also made by FAME oxidation. In conclusion, it is necessary to find the way to improve the micro-algal bio diesel's oxidation stability.

• Korean Chemical Engineering Research
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• v.52 no.6
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• pp.720-726
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• 2014

PEM fuel cell vehicles have been getting much attraction due to a sort of highly clean and effective transportation. The onboard fuel processor, however, is inevitably required to supply the hydrogen by conversion from some fuels since there are not enough available hydrogen stations nearby. A lot of studies have been focused on analyses of ATR reactor under the assumption of thermo-neutral condition and those of the optimized process for the minimization of energy consumption using thermal efficiency as an objective function, which doesn't guarantee the maximum hydrogen production. In this study, the analysis of optimization for 100 kW PEMFC onboard fuel processor was conducted targeting various fuels such as gasoline, LPG, diesel using newly defined hydrogen efficiency and keeping simply synthesized heat exchanger network regardless of external utilities leading to compactness and integration. Optimal result of gasoline case shows 9.43% reduction compared to previous study, which shows the newly defined objective function leads to better performance than thermal efficiency in terms of hydrogen production. The sensitivity analysis was also done for hydrogen efficiency, heat recovery of each heat exchanger, and the cost of each fuel. Finally, LPG was estimated as the most economical fuel in Korean market.

• Journal of Applied Biological Chemistry
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• v.57 no.4
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• pp.379-386
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• 2014

Chromatin is an instructive DNA structure that can widely respond to external signals. An important change of chromatin is the modifications of histone for this regulation. There are accumulating lists of these modifications and the complexity of their action is gradually understood. It is evident that histone modifications play important roles in most biological processes that are involved in the expression or repression of DNA. The surface of nucleosomes is susceptible to multiplicity of modifications. Chromatin modifications can play either by eliminating chromatin contacts or by recruiting non-histone proteins to chromatin. Many of these regulations seem to be epigenetically inherited. Thus, histone modifications are closely correlated with many fundamental biological processes in animal, plant and microbial kingdoms. Failures of histone modification lead, in general, to defective chromosome condensation or decondensation, impeding many biological functions including development, maturation, and protection against various diseases.

• Clean Technology
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• v.13 no.4
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• pp.287-292
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• 2007

[ $M/Al_2O_3$ ] (M = Mn, Fe, Co, Ni, Cu) catalysts supported on commercial alumina ($Al_2O_3$) were prepared by an impregnation method, and were applied to the hydrogen production by auto-thermal reforming of ethanol. It was revealed that each catalyst retained its own metallic phase and product distribution strongly depended on the identity of active metal. Among the catalysts prepared, $Ni/Al_2O_3$ and $Co/Al_2O_3$ showed the best catalytic performance in the auto-thermal reforming of ethanol. However, the reaction mechanisms over these two catalysts were different. Ni/Al_2O_3 catalyst showed 100% ethanol conversion at $500^{\circ}C$, but it exhibited a rapid decrease in hydrogen selectivity. Although $Co/Al_2O_3$ catalyst showed an excellent performance in hydrogen selectivity, on the other hand, no significant improvement in hydrogen yield was observed due to the low ethanol conversion over the catalyst.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.330-334
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• 2013

Mixtures of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and silica nanoparticles are coated on the surface of a silk fabrics separator. The coated separators are finally prepared by injecting an electrolyte solution and then characterized for use of lithium-ion battery separator/electrolyte. In the preparation, various contents of dibutylphthalate (DBP) as a plasticizer are used to enhance the formation of micropores within the coated membrane. The coated silk fabrics separators are characterized in terms of ionic conductivity, drenching rate, and electrochemical stability, and the charge-discharge profiles of lithium-ion batteries adopting the coated separators are also examined. As a result, the coated silk fabrics separator prepared using DBP 40~50 wt% and silica shows the superior separator properties and high-rate capability. This is due to (i) high sustainability of silk fabrics, (ii) the formation of micropores with the coated layer membrane by DBP, (iii) increase in drenching rate by silica nanoparticles to involve great enhancements in specific surface area and ionic conductivity.