• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.56-61
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• 2016

In this study, the effect of natural minerals on the reaction kinetics for lignite-$CO_2$ gasification was investigated. After physical mixing of lignite from Meng Tai area with 5 wt% of each natural mineral catalysts among Dolomite, Silica sand, Olivine and Kaolin, $CO_2$ gasification was performed using TGA at each 800, $850^{\circ}C$ and $900^{\circ}C$. The experimental data was analyzed with volumetric reaction model (VRM), shrinking core model (SCM) and modified volumetric reaction model (MVRM). MVRM was the most suitable among three models. As increasing the reaction temperature, the reaction rate constant became higher. With natural mineral catalysts, the reaction rate constant was higher and activation energy was lower than that of without catalysts. The lowest activation energy, 114.90 kJ/mol was obtained with silica sand. The highest reaction rate constant at $850^{\circ}C$ and $900^{\circ}C$ and lower reaction rate constant at $800^{\circ}C$ were obtained with Kaolin. Conclusively, the better catalytic performance could be observed with Kaolin than that of using other catalysts when the reaction temperature increased.

• Journal of the Korean Society of Combustion
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• v.2 no.1
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• pp.29-38
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• 1997

In this study, the experimental and numerical investigations of the ignition of methane-air mixtures by a electrically heated wire have been carried out. In order to define the initial condition and make the analysis simple, the following control unit was developed; which heats the wire to the setting temperature in a very short time, and maintains the wire temperature constant until ignition. Experiments with the feedback control have been performed using nickel and platinum wires in normal gravity and microgravity. From experimental results, ignition temperatures in normal gravity are higher than those in microgravity, however, the dependences of ignition temperature on equivalence ratio are not affected by natural convection. Numerical calculations, including catalytic reaction for platinum, have been performed to analyze the experimental results in microgravity. Numerical results show that reactants near platinum wire are consumed by catalytic reaction, therefore, the higher temperature is needed to ignite the mixture with platinum wire.

• Journal of Microbiology and Biotechnology
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• v.9 no.1
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• pp.1-8
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• 1999

Most carbohydrates exist in nature in an insoluble state, which reduces their susceptibility towards various carbohydrases. Accordingly, they require intensive pretreatment for structural modification to enhance an enzyme reaction. The direct conversion of insoluble carbohydrates has distinct advantages for special types of reaction, especially exo-type carbohydrase; however, its application is limited due to structural constraints. This paper introduces two novel heterogeneous enzyme reaction systems for direct conversion of insoluble carbohydrates; one is an attrition coupled enzyme reaction system containing attrition-milling media for enhancing the enzyme reaction, and the other is a heterogeneous enzyme reaction system using extruded starch as an insoluble substrate. The direct conversion of typically insoluble carbohydrates, including cellulose, starch, and chitin with their corresponding carbohydrases, including cellulase, amylase, chitinase, and cyclodextrin glucanotransferase, was carried out using two proposed enzyme reaction systems. The conceptual features of the systems, their reaction characteristics and mechanism, and the industrial applications of the various carbohydrates are analyzed in this review.

• Journal of Microbiology and Biotechnology
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• v.6 no.6
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• pp.432-438
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• 1996

Native crystalline chitin was hydrolyzed in an agitated bead reaction system using crude chitinase excreted from Aspergillus fumigatus JC-19. The reaction was enhanced significantly, and the concentration and yield of reducing sugar after 48 hours were measured to be 35.42 g/I (w/v) and 0.64, respectively, around 1.86 times higher than those of the conventional system that was carried out without glass beads. The effect of reaction conditions, such as the amounts of chitin, chitinase and glass beads, and the size of glass bead, were examined. Ball milled chitin was also hydrolyzed in the agitated bead reaction system, the conversion yield and reaction rate of ball milled chitin for 24 hours increased up to 0.87 and 48.02 g/I, respectively. Chitinase showed relatively high stability in the agitated bead reaction system, particularly in the presence of enzyme stabilizer, $Ca^{++}$, which played a critical role in preventing the deactivation of chitinase by the physical impact of glass beads. The variations of the structural features of chitin during the reaction were followed by SEM and X-ray diffraction, and the enhanced hydrolysis reaction was caused by both the fragmentation of chitin particles and the destruction of the crystalline structure owing to the synergic effects of the attrition of glass beads and the hydrolytic action of chitinase.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3410-3414
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• 2013

Atom-economical esterification is of great importance in green chemistry. In this work, we demonstrated the catalyst and additive free esterification of alcohols by their reaction with 2-acyl-4,5-dichloropyridazin-3(2H)-ones without solvent at $100^{\circ}C$. Aliphatic and aromatic alcohols were converted into the corresponding esters in good to excellent yields. It is noteworthy that the reaction is solvent-free, atom-economic, easy-workup, and rapid and that the process is inexpensive.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.42-48
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• 2013

Potassium N-heterobiaryltrifluoroborates were successfully prepared via a selective Cu-catalyzed C-N coupling reaction. The $BF_3K$ moiety was well tolerated under the reaction conditions involving CuI and dimethyl-ethylenediamine (DMEDA) in the presence of DMSO. The Pd-catalyzed Suzuki-Miyaura cross couplings of potassium N-heterobiaryltrifluoroborates with bromoarenes were studied to prepare the N-heterotriaryl compounds. Moreover, homocoupling, iodination, and hydroxylation of potassium N-heterobiaryltrifluoroborates provided the corresponding products in high yields.

• Bulletin of the Korean Chemical Society
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• v.28 no.7
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• pp.1089-1090
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• 2007

• Proceedings of the Korean Biophysical Society Conference
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• 1996.07a
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• pp.46-46
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• 1996

To elucidate the mechanism for the cross-linking reaction in the glycation or Maillard reaction, we studied the reaction between proteins, and a three-carbon ${\alpha}$-ketoaldehyde, methylglyoxal. When Cu, Zn-SOD was incubated with 200 mM of methylglyoxal, the peroxidase activity as well as the superoxide dismutase activity was reduced. This reduction is accompanied by the decrease of the anion binding affinity of the enzyme. (omitted)

• Journal of Ginseng Research
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• v.36 no.3
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• pp.256-262
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• 2012

Reactive oxygen species play critical role in kidney damage. Free radical-scavenging activities of Panax ginseng are known to be increased by heat-processing. The structural change of ginsenoside and the generation of Maillard reaction products (MRPs) are closely related to the increased free radical-scavenging activities. In the present study, we have demonstrated the Maillard reaction model experiment using ginsenoside Re and glycine mixture to identify the renoprotective effect of MRPs from ginseng or ginsenosides. Ginsenoside Re was transformed into less-polar ginsenosides, namely Rg2, Rg6 and F4 by heat-processing. The free radical-scavenging activity of ginsenoside Re-glycine mixture was increased in a temperature-dependant manner by heatprocessing. The improved free radical-scavenging activity by heat-processing was mediated by the generation of antioxidant MRPs which led to the protection of LLC-PK1 renal epithelial cells from oxidative stress. Although the free radical scavenging activities of less-polar ginsenosides were weak, they could protect LLC-PK1 cells from oxidative stress. Therefore, MRPs and less-polar ginsenosides contributed to the combined renoprotective effects against oxidative renal damage.

• Environmental Analysis Health and Toxicology
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• v.1 no.1
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• pp.47-54
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• 1986

The immunopotentiating effect of ethanol extract, butanol fraction and petroleum ether extract of Panax ginseng on the immunotoxicity of benzo(a)pyrene were investigated in mice. A single administration of benzo(a)pyrene induced an apparent but relatively transient reduction in HY titer, Arthus reaction, delayed type hypersensitivity, rosette forming cell and natural killer cell activity Ethanol extract very significantly restored HY titer, Arthus reaction. RFC and natural killer cell activity. Butanol fraction have no effect. But petroleum ether extract very significantly restored humoral and cellular immune response and especially natural killer cell activity.