• Korean Chemical Engineering Research
• /
• 제47권4호
• /
• pp.410-417
• /
• 2009

중간세공크기(mesopore)의 MCM41에 Imidazole을 담지시킨 CP-MS41 고체 입자의 촉매를 사용하여 GMA 용액에 $CO_2$를 흡수시켜 $CO_2$의 흡수기구로부터 GMA와 $CO_2$의 반응속도론을 고찰하였다. 대기압에서 회분식 흡수조를 사용하여 임펠러의 교반속도, 50 rpm, 촉매, 2 g, 반응온도, 60, 70, $80^{\circ}C$, GMA의 농도, $0.1{\sim}3.0kmol/m^3$, 용제, DMA, NMP, DMSO에서 측정한 $CO_2$의 흡수속도와 경막설에 의한 물질수지식을 사용하여 반응속도상수를 구하였다.

• 한국수소및신에너지학회논문집
• /
• 제18권3호
• /
• pp.334-341
• /
• 2007

Al film(135.5 nm thick) with Pd film(39.6 nm thick) was made by thermal evaporation method. Electrical resistance change by hydrogen absorption and desorption was measured with four point measurement method. Even though Al film(135.5 nm thick) did not absorb any hydrogen at room temperature, Al/Pd film absorbed hydrogen at upto 640 torr pressure. Hydrogen absorption kinetics was monitored by measuring resistance change of the sample in the temperature range from $25^{\circ}C$ to $40^{\circ}C$. Absorption activation energy of Al/Pd film was about 10.7 and 17.7 kcal/mol H for 1st stage and last stage respectively at 1 torr hydrogen pressure. This activation values are bigger than that of Pd film, but are much less than that of Al film. This result indicates there is possibility that Al can be storage material for hydrogen by using Pd film evaporation on it.

• 한국수소및신에너지학회논문집
• /
• 제29권1호
• /
• pp.90-96
• /
• 2018

Reaction characteristics and kinetics of a oxygen carrier (OCN717-R1SU) for chemical looping combustion (CLC) have been investigated using TGA by changing gas concentration (10-30 vol.% $CH_4$) and reaction temperature ($825-900^{\circ}C$). Reaction rate of OCN717-R1SU increased as temperature increased and it was found that reaction is delayed at the initial reaction regime. Johnson-Mehl-Avrami (JMA) model was adopted to explain the reaction phenomenon. The activation energy (E) determined by JMA model in reduction reaction of OCN717-R1SU is $151.7{\pm}2.03kJ/mol$ and pre-exponential factor and JMA exponent were also obtained. The parameters calculated in this study will be applied in design of the reactor and operation conditions for CLC process.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제11권3호
• /
• pp.223-229
• /
• 2006

In this study, we have conducted kinetics and modelling studies of Centella asiatica cell growth and substrate uptake, in an attempt to evaluate cell growth for a better understanding and control of the process. In our bioreactor cultivation experiment, we observed a growth rate of 0.18/day, a value only 20% higher than was seen in the shake flask cultivation trial. However, the observed maximum cell dry weight in the shake flask, 10.5g/L, was 14% higher than was achieved in the bioreactor. Ninety seven percentage confidence was achieved via the fitting of three unstructured growth models; the Monod, Logistic, and Gompertz equations, to the cell growth data. The Monod equation adequately described cell growth in both cultures. The specific growth rate, however, was not effectively predicted with the Logistic and Gompertz equations, which resulted in deviations of up to 73 and 393%, respectively. These deviations in the Logistic and Gompertz models may be attributable to the fact that these models were developed for substrate-independent growth and fungi growth, respectively.

• 한국환경과학회지
• /
• 제22권10호
• /
• pp.1327-1335
• /
• 2013

Na-A zeolite (Z-Cl) was synthesized from coal fly ash, which is a byproduct of coal combustion for the generation of electricity. The adsorption of $Cu^{2+}$ and $Zn^{2+}ions$ onto Z-C1 was investigated via batch tests over a range of temperatures (303.15 to 323.15 K). The resultant experimental equilibrium data were compared to theoretical values calculated using model equations. With these results, the kinetics and equilibrium parameters of adsorption were calculated using Lagergren and Langmuir-Freundlich models. The adsorption kinetics revealed that the pseudo second-order kinetic mechanism is predominant. The maximum adsorption capacity ($q_{max}$) values were 139.0-197.9 mg $Zn^{2+}$/g and 75.0-105.1 mg $Cu^{2+}/g$. Calculation of the thermodynamic properties revealed that the absorption reactions for both $Cu^{2+}$ and $Zn^{2+}$ were spontaneous and endothermic. Collectively, these results suggest that the synthesized zeolite, Z-C1, can potentially be used as an adsorbent for metal ion recovery during the treatment of industrial wastewater at high temperatures.

• 대한가정학회지
• /
• 제11권1호
• /
• pp.44-56
• /
• 1973

The effect of the temperature and the time of scalding, and the addition of various seasoning on the remaining % of total Vitamin C contained in Spinach (Spinacia oleracea) was studied and discussed by means of chemical kinetics. The quantitative measurements of total Vitamin C were made by 2,4-dinitrophenyl hydrazine (DNPH) method with Clinical Electrophotometer (Fisher). The sample spinach contains 39.88mg. % of total vitamin C on the average, and the ratio of oxidized and reduced forms of Vitamin C is 1 : 4.7. When the sample spinach was scalded, the kinetics of the decrease of the remaining total vitamin C. % was observed to follow the first order reactions regardless of the temperatures applied (i,e. 70$^{o}$ , 80$^{o}$ , 90$^{o}$ and 100$^{o}$ ) with half-life range of 2.10 - 1.47 minutes. In the case of the addition of various seasonings, the addition of various seasonings, the kinetics remaining Vitamin C % showed to be the zero order reactions regardless of the kinds of seasonings and storage temperatures. With the addition of seasonings, the stability of Vitamin C was found to be increased in the order table salt+sesame oil+vinegar+soybean sauce, without seasoning, table salt+sesame oil, table salt+sesame oil+soybean sauce.

• Composites Research
• /
• 제28권3호
• /
• pp.99-103
• /
• 2015

본 논문에서는 복합재료 제조공정 중 온도에 따른 경화 반응을 이해하고 열분석을 수행하였으며, 이 결과를 바탕으로 온도에 따른 수지의 경화도 및 비열의 변화를 수식화하였다. 온도에 따른 경화도와 비열은 DSC와 MDSC (Modulated DSC)를 활용하여 측정하였다. DSC와 MDSC 분석은 Isothermal과 Dynamic 조건으로 수행하여 Cure Kinetics, 유리전이온도 및 비열을 측정하고, 회기 분석 방법을 이용하여 물성거동을 수학적으로 모델링하였다.

• Bulletin of the Korean Chemical Society
• /
• 제26권2호
• /
• pp.260-264
• /
• 2005

The nature of the active site of Tobacco acetohydroxyacid synthase (AHAS) in the substrate- and cofactorbinding was studied by kinetics and fluorescence spectroscopy. The substrate saturation curve does not follow Michaelis-Menten kinetics at different temperatures (7, 21 and 37 ${^{\circ}C}$), pH (6.5, 7.5 and 8.5) and buffers (Tris-HCl and MOPS). The concentration of one half of the maximum velocity ($S_{0.5}$) decreased in the following order: pyruvate $\gt$ ThDP $\approx$$Mg^{+2}$ $\gt$ FAD. However, the catalytic efficiency (K$_{cat}/S_{0.5}$) inversely decreased in the following order; FAD $\gt$ $Mg^{+2}$ $\approx$ThDP $\gt$ pyruvate, indicating that the cofactors by in decreasing order; FAD, $Mg^{+2}$, ThDP, affect the catalysis of AHAS. The dissociation constant ($K_d$) of the intrinsic tryptophan fluorescence decreased with the same tendency of the concentration of one half of the maximum velocity ($S_{0.5}$) decreasing order. This data provides evidence that the substrate and cofactor binding natures of the active site, as well as its activation characteristics, resemble those of other ThDP-dependent enzymes.

• Bulletin of the Korean Chemical Society
• /
• 제25권5호
• /
• pp.726-736
• /
• 2004

In this paper, kinetics of reaction between Bromophenol blue (BPB) and $OH^-$, called fading, has been studied through a spectrophotometric method in the presence of nonionic Triton X-100 (TX-100), anionic sodium dodecyl sulfate (SDS) and cationic dodecyl trimethylammonium bromide (DTAB) surfactants. The influence of changes in the surfactant concentration on the observed rate constant was investigated. The results are treated quantitatively by pseudophase ion-exchange (PPIE) model and a new simple model called "classical model". The binding constants of BPB molecules to the micelles and free molecules of surfactants, their stoichiometric ratios and thermodynamic parameters of binding have been evaluated. It was found that SDS has nearly no effect on the fading rate up to 10 mM, whereas TX-100 and DTAB interact with BPB which reduce the reaction rate. By the use of fading reaction of BPB, the binding constants of SDS molecules to TX-100 micelles and their Langmuir and Freundlich adsorption isotherms were obtained and when mixtures of DTAB and TX-100 were used, no interaction was observed between these two surfactants.

• 소성∙가공
• /
• 제26권1호
• /
• pp.48-54
• /
• 2017

The dissolution and precipitation of Nb, which has been known as strong carbide-forming element, play a key role in controlling phase transformation kinetics of microalloyed steels. In this study, we analyzed both numerically and experimentally the precipitation behavior of Nb-microalloyed steel and its effect on the austenite decomposition during cooling. Nb precipitation in austenite matrix could be predicted by the thermo-kinetic software MatCalc, in which interfacial energy between precipitate and matrix is calculated. The simulated precipitation kinetics fairly well agrees with the experimental observations by TEM. Austenite decomposition, which is strongly affected by Nb precipitation during cooling, was measured by dilatometry and was modeled on the basis of a Johnson-Mehl-Avrami-Kolmorgorov(JMAK) equation. It was confirmed that the dissolved Nb delays the austenite decomposition, whereas, the precipitated Nb accelerates phase transformation during the austenite decomposition.