• Journal of the Korean Applied Science and Technology
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• v.27 no.1
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• pp.6-13
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• 2010

Esterification reaction between succinic acid and 1,4-butanediol was kinetically investigated in the presence of nontoxic organometallic compound catalyst(ESCAT-100E) at $150-190^{\circ}C$. The reaction rates measured by the amount of distilled water from the reaction vessel. The Esterification reaction was carried out under the first order conditions respect to the concentration of reactants, respectively. The overall reaction order was 2nd. The linear relationship was shown between apparent reaction rate constant and reciprocal absolute temperature. By the Arrhenius plot the activation energy have been calculated as 376.13 kJ/mol under nontoxic organometallic compound catalyst and also apparent reaction rate constant, k' was found to obey first kinetics with respect to the concentration of catalyst.

• Journal of the Korean Chemical Society
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• v.18 no.4
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• pp.251-258
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• 1974

The rate constants for the nucleophilic substitution reactions of substituted benzoyl chlorides with p-nitroaniline in such solvents as acetone, acetonitrile, methanol, ethanol, etc. were conductometrically determined, and the activation thermodynamic parameters were also evaluated. In result, the reaction rates were faster in protic solvents than in aprotic solvent; in the solvents of similar property, the reaction rate in the solvent of the large dielectric constant was faster than that in the solvent of the small dielectric constant. Hammett plots in individual solvents showed the straight lines with positive slope; and we concluded that the reaction occurred via the addition-elimination mechanism.

• Korean Journal of Food Science and Technology
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• v.21 no.3
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• pp.425-429
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• 1989

Functional relationships of carotenoid destruction and nonenzymatic browning during red pepper drying were established by the dynamic test using the moisture-temperature-quality history curve in actual drying experiments. The dependence of the rate constants on temperature and moisture content was established and analysed assuming that carotenoid destruction and nonenzymatic browning are the first order and the zero order reaction, respectively. Carotenoid destruction rate constant was high at high moisture and high temperature, and had a minimum value at some intermediate moisture content. As dependence of rate constant on temperature, activation energy of carotenoid decolorization ranged from 7.7 to 27.4 kcal/mol, showing higher value at higher moisture content. Nonenzymatic browning showed higher rate at higher temperature and higher moisture content. Activation energy of browning was in the range of 7.5-20.2 kcal/mol with higher value at higher moisture level.

• Korean Journal of Food Science and Technology
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• v.33 no.6
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• pp.706-713
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• 2001

The influencing factor in drying characteristics of fluidized bed drying with different drying conditions for husked barley were carried out. This fluidized drying mechanism of husked barley was consisted of consecutive two falling rate parts, first falling rate period and second falling rate period without showing constant rate period. The drying rate constant was increased with decreasing charged amount and relative humidity and increasing air temperature and air velocity. Since the drying rate constant expressed by Arrhenius type equation in the falling rate period showed good linearity, the falling rate period was condsidered as the controlling step. The activation energy of first falling step was 1,100 cal/gmol, while for second falling step the values showed 1,600 cal/gmol.

• Polymer(Korea)
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• v.30 no.4
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• pp.305-310
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• 2006

The hybrid cation exchange fibers using graft copolymer of styrene onto PE/PP with PET trunk polymers were synthesized by electron beam preirradiation. The degree of grafting showed 123% value at 80% concentration of styrene. And also, amount of sulfonyl group in the ion exchanger was showed 3.3 mmol/g at 70% concentration of styrene and their values were constant after 70%. The tensile strength for fibers was lower than trunk fibers, and their value of ion exchange fibers were also below than copolymer. It was $0.206kgf/mm^2$ value. The breakthrough time for Ca and Mg ions of hybrid cation exchange fibers were increased with the increase in the pH and temperature. The breakthrough of Mg was slower the mixture than single Mg solution. Adsorption rate constant for Ca, Mg ions and maximum ion exchange capacity were 0.012, 0.011 L/mg.h and 47.06, 42.83 mg/g, and also, activation energies were 2169 and 1534 J/mol, respectively.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.94-102
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• 1993

The effects of temperature and of $Na_2O$ and $SiO_2$ contents on the crystallization of zeolite A were studied, by examining crystallization curves and particle size distributions of final products at various crystallization conditions. Crystallization process could be simulated adopting the assumptions of constant linear growth rate and equilibrium between amorphous solid phase and soluble species. Rate constants were determined by comparing the simulated crystallization curves with experimental data. Rate constant for linear growth increased with temperature and crystallization rate at different mole ratio of $Na_2O/H_2O$ correlated reasonably well with increase of soluble species. The rate constant of crystallization did not increase with increase in mole ratio of $Na_2O/H_2O$, but the rate of nuclei formation and the fraction of soluble species were enhanced. The rate constants for linear growth of zeolite A were determined as $0.07{\sim}0.24{\mu}m{\cdot}min^{-1}$ at these experimental conditions Apparent activation energy was estimated as $49kJ{\cdot}mol^{-1}$.

• Journal of the Korean Chemical Society
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• v.14 no.1
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• pp.85-89
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• 1970

The rate of the bromine-exchange reaction between gallium bromide and isopropyl bromide in nitrobenzene was measured at 19$^{\circ},\;25^{\circ}$ and 40$^{\circ}C$., using isopropyl bromide labelled with Br-82. The results indicated that the exchange reaction was second order with respect to gallium bromide and first order with respect to isopropyl bromide. The third-order rate constant determined at 19$^{\circ}C$. was 3.2 ${\times}10^{-2}l^2{\cdot}mole^{-2}sec^{-1}$. The activation energy, the enthalpy of activation and the entropy of activation for the exchange reaction were also determined.

• Journal of Magnetics
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• v.4 no.1
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• pp.13-16
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• 1999

Magnetic viscosities of a commercialized metal evaporated tape were measured as a function of sweeping rate in VSM at room temperature. Within several seconds in the viscosity measurement, curves are downward concave and more concave with increasing sweeping rate when magnetization were plotted as a logarithmic function of time. However, magnetization varied as a logarithmic function of time after several seconds. Magetic viscosity coefficient gradually increased with increasing sweeping rate and then kept a constant value at a rate faster than 61.5 Oe/s. It was supposed that magnetic viscosity occurs during field sweeping, which was in good agreement with Sharrock's model qualitatively. Activation volume decreased with increasing sweeping rate, which was due to the fact that magnetic viscosity coefficients increased with sweeping rate while irreversible susceptibilities were not affected by sweeping rate.

• Korean journal of food and cookery science
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• v.15 no.4
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• pp.363-369
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• 1999

The study was carried out to compare the reaction rate of caramel type browning reaction of xylose(XY), glocose(GL), sucrose(SU), glucose+citric acid(GLCA), glucose+sodiumcitrats(GLSC), glucose+glycine(GLGC) heated at 60, 80, 100, 120 and 140$^{\circ}C$ for 24 hours, respectively. 1. The color intensity (absorbance at 490 nm) of the browning reaction mixtures tends to increase as the browning reaction time gets longer and the browning of reaction temperature gets higher. But the degree of the intensity of SU and GLCA changes very little. 2. The reaction rate constant (K) was increased rapidly above 120$^{\circ}C$ and appeared maximum at 140$^{\circ}C$, especially GLGC (140.25) was the highest. The activation energy (Ea) of sugars. XY had the highest value (124.36 J/mol), while SU the lowest(104.68 J/mol). Mixtures of GLGC was shown to have higher activation energy (144.94 J/mol) than the sugar alone and Q$\_$10/ values of GLGC were 1.68-2.85. 3. The residual amount of reactants such as xylose, glucose, sucrose, citric acid, sodium citrate and glycine in each browning mixture were decreased upon the browning reaction temperature increasing. In the GLCA, GLSC and GLGC browning mixtures, respectively, the residual amounts of glucose were less than those with amino acid, organic acid and their salt.

• Journal of the Korean institute of surface engineering
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• v.18 no.1
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• pp.5-11
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• 1985

Titanium was deposited onto AISI-430 stainless steel by chemical vapor deposition from $TiI_4\;and\;H_2$ gas mixture. Effects of temperature, flow rate of the gas, and $TiI_4$ partial pressure on the deposition rate were thoroughly investigated. The deposition rate of Ti was found to be constant at the given temperature and was increased with increasing temperature. The rate is controlled by surface reaction at the flow rate of gas higher than 500 ml/min, whereas at the flow rate lower than that by diffusional process. It is also interesting to note that the reaction mechanism changes at 1050$^{\circ}C$, at temperatures lower than 1050$^{\circ}C$ the activation energy is 56.9 Kcal/mol, whilst at temperatures higher than that is 8.3 Kcal/mol.