• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.722-729
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• 1992

Mg-and Zn-ferrites having spinel structure, a kind of complex oxides showing the advantageous properties of constituently single metal oxides, were selected to find a relationship between their catalytic activities in the dehydrogenation of ethylbenzene to styrene and the catalytic properties. For the structural and physical analyses of ferrites, XRD, BET, DTA, XPS, TEM and TPD methods were employed. Potassium added to the catalyst played a role of bifunctional promoter which brought the electronic effect as well as the structural one for the increment of particle dispersion. K-addition decreased acid strength of the catalyst by neutralization and increased its acidity. In the dehydrogenation of ethylbenzene, K-addition let the selectivity to styrene be constant throughout the reaction by the proper acid strength of the ferrite for the reaction, which could be obtained from the neutralization of strong acid sites by potassium.

• Applied Biological Chemistry
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• v.39 no.1
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• pp.1-8
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• 1996

A one-stage, continuous-flow bioreactor with both immobilized and suspended cells was used to investigate the roles of lipid supplements in ethanol production by Saccharomyces cerevisiae. The reactor performance and the level of alcohol dehydrogenase(ADH) activities of the suspended cells, grown under various conditions, were measured. When ergosterol and/or oleic acid were added with surfactants to the yeast culture grown under non-aerated conditions, remarkable increases in ethanol production and cell growth was achieved, but specific ADH activities were not affected. Especially, no difference of specific ADH activities of the suspended cells grown under aerated and non-aerated condition was observed. The addition of the surfactant as a supplement also resulted in significant increases in ethanol production, cell growth, and specific ADH activity. When ergosterol and oleic acid were added to the yeast culture exposed to higher ethanol concentration($>40\;g/{\ell}$) level, ethanol production, cell growth, and specific ADH activity were increased, but the addition of surfactant was as effective as at lower ethanol concentration level. The results indicated that lipid supplements were more effective at higher ethanol concentration level than at lower ethanol concentration level during ethanol production. ADH isozyme patterns of the yeast cultures grown under various conditions on starch gel electrophoresis showed only one major band, probably ADH I. The migrating distance of the major isozyme, however, varied slightly according to the culture conditions of the cells. No apparent correlation was found between specific ADH activity and amount of ethanol produced. Cell mass was more important factor for ethanol production than specific ADH activity of the cells.

• Journal of the Korean Chemical Society
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• v.24 no.4
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• pp.315-321
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• 1980

A steady-state kinetic study on a dye-coupled cytoplasmic polyol dehydrogenase from G. melanogenus was carried by the initial velocity measurements in the direction of the polyol oxidation and the product inhibition by D-fructose. For the initial rate experiments, D-mannitol and D-sorbitol were employed as the specific polyol substrates and 2,6-dichlorophenolin-dophenol (DPIP) as the specific cofactor substrate for the enzyme. When the polyol and DPIP were examined by varying one of substrates and by fixing the second, the corresponding reciprocal plots showed the typical parallel pattern. This suggests that the enzyme from G. melanogenus proceeds by a Ping Pong Bi-Bi mechanism in which the polyol may account as the first reactant-in, and the ketose formed as the first product-out, respectively. The product inhibition patterns obtained by D-fructose (one no-inhibition, one non-competitive, and two competitive) may also provide an additional conformatory evidence for the above mechanism. Based on the kinetic parameters obtained, it was also suggested that the rate-limiting step in the direction of polyol oxidation is associated with the release of the ketose from the Enzyme${\cdot}$Polyol complex.

• Journal of the Korean Chemical Society
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• v.19 no.6
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• pp.423-427
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• 1975

Changes in the electrical conductivity of gallium doped zinc oxide during the dehydrogenative oxidation of ethanol between 250 and $350^{\circ}C$ have been studied. Both dehydrogenation and dehydration of ethanol takes place on ZnO. At $300^{\circ}C$ and above formation of $CO_2$ was observed accompanied by an increase in the electrical conductivity. This seems to be due to oxidation of CO formed by the decomposition of acetaldehyde. Addition of oxygen to ethanol increases the amount of acetaldehyde formed, while no change is observed in ethylene formation. It may be that oxygen which is present primarily as $O^-$ provides a favorable site for the adsorption of ethanol and for subsequent hydrogen substraction.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.575-583
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• 2019

The results of the catalytic reaction by pulsed injection of reactants are useful for studying the initial reaction characteristics in the case of many coke invloved reactions. The dehydrogenation characteristics of alumina supported platinum tin catalysts were investigated by pulsed injection of propane. The yield of propylene was maximized when the reduction time of propane injection catalyst was $550^{\circ}C$. Raman analysis showed that the amount of coke was very small when PtSn (4.5) catalyst was used and the short contact time was simulated by propane pulse injection. n order to differentiate the degree of dispersion of platinum, PtSn (4.5) catalyst was sintered at $900^{\circ}C$ with hydrogen, and then the temperature of air - redispersion was varied and propane pulse was injected. As a result, conversione and yield were the highest when air-redispersion temperature is $600^{\circ}C$. The lower the air-redispersion temperature, the higher the selectivity. As the tin content in the platinum catalyst increased, the propane conversion was lowered, but the selectivity to propylene increased and the yield increased. From this, it can be seen that the tin-added platinum catalyst is less active than the platinum catalyst from the beginning of the reaction, which is less affected by coke. The dehydrogenation reaction by the propane pulse injection shows a higher conversion rate than the result of continuous injection due to the formation of COx, and the amount of coke is very small. Decrease in selectivity due to the formation of COx can be reduced by increasing the reduction temperature and time.

• Clean Technology
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• v.18 no.2
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• pp.162-169
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• 2012

Pt-Sn/${\theta}-Al_2O_3$ catalyst for n-butane dehydrogenation reaction was prepared by incipient wetness method. To confirm the physicochemical properties of Pt-Sn/${\theta}-Al_2O_3$ catalyst, the characterization was performed using X-ray diffraction (XRD), $N_2$ sorption analysis, temperature programmed desorption of $NH_3$ ($NH_3$-TPD), temperature programmed reduction of $H_2$ ($H_2$-TPR) techniques. Also, the catalytic activities of Pt-Sn/${\theta}-Al_2O_3$ for n-butane dehydrogenation was tested as a function of pretreatment temperature, pretreatment time, reaction temperature, and the partial pressure of n-butane and hydrogen. The sum of selectivities to n-butenes consisting of 1-butene, cis-2-butene, and trans-2-butene was almost constant 95% in the range of conversion of n-butane 5-55%. The activation energy calculated from Arrhenius equation was $82.4kJ\;mol^{-1}$ and the reaction orders of n-butane and hydrogen from Power's law were 0.70 and -0.20, respectively.

• Proceedings of the Korean Environmental Health Society Conference
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• 2005.11a
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• pp.110-114
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• 2005

인공적으로 디젤류에 오염시킨 5kg의 토양이 충전된 두 개의 실험 column을 이용해서 외부 온도변화 효과를 최소화하기 위해서 $25^{\circ}C{\pm}2.5$로 유지시켰으며, 유량속도도 10ml/min로 일정하게 유지시켰다. 또한 수분은 활동범위 능력의 $60{\sim}80%$에서 유지시켰다. 따라서 연속식과 간헐 주입식 모드를 운전비용의 감소 및 효율의 향상 측면에서 모드의 평가를 위한 방법으로 이용기간 동안 총세균 수, 유류분해균 수의 변화, 탈수소효소 활성도의 변화 추이 분석을 하였다. 두 venting 모드별로 본 총 종속영양균 수와 유류분해균 수는 모두 대등한 성장률을 보였으며, 반응일 수에 따라 비교된 탈수소효소 활성도 반응 90일 동안 비슷한 활성을 유지 했다.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.2
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• pp.152-158
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• 2004

Hydrogen has been considered as an important and essential future energy source. But the storage of the hydrogen is a difficult problem and many studies were focused on this matter. However, the MTH-system (methylcyclohexane, toluene, hydrogen) was proposed for storage of hydrogen by Taube et al. and that is the reaction of hydrogen with toluene to give methylcyclohexane. One toluene molecule can store six hydrogen atoms to form methylcyclohexane. In this form the hydrogen can be easily stored in liquid organic hydrides and transported at ambient pressure in tanks. Hence, this study is focused on the catalytic dehydrogenation of methylcyclohexane. Since supported platinum and nickel were employed as catalysts in literature, in this study, porous Pt and Ni were prepared and tested for the dehydrogenation reaction. When the porous Pt catalyst was applied to the dehydrogenation it showed higher activity in the reaction and higher selectivity to toluene. Specially at higher pressure, it showed almost 100 % conversion and 100 % selectivity and hence porous platinum could be considered as best for the given reaction.

• Journal of the Korean Chemical Society
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• v.55 no.1
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• pp.81-85
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• 2011

$V_{0.9}Sb_{0.1}O_x$ systems, bulk and deposited on different supports (five types of $\gamma$-aluminas, $\alpha$-alumina, silica-alumina, silica gel, magnesium oxide), have been tested in the oxidative dehydrogenation (ODH) of iso-butane. Catalytic performance of VSb oxides has shown to be highly dependent on the support and the nature of the support decreasing in a series: $\gamma$-$Al_2O_3$ > $\alpha$-$Al_2O_3$ > Si-Al-O > $SiO_2$ $\approx$ MgO $\gg$ unsupported. Variation of the V-Sb-O-loading in the studied range of coverage (0.5-2 theoretical monolayer) only slightly influences the catalysts' activity and selectivity. The best catalytic performance of $\gamma$-alumina-supported $V_{0.9}Sb_{0.1}O_x$ systems can be explained by the optimal surface interaction between support and supported components resulting in the formation of well-spread amorphous active $VO_x$-component with vanadium in a high oxidation state.

• Applied Chemistry for Engineering
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• v.2 no.3
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• pp.279-288
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• 1991

Mg- and Zn-ferrites having spinel structure, a kind of complex oxides showing the advantageous properties of constituent single metal oxides, were selected to find a relationship between their catalytic activities in the dehydrogenation of ethylbenzene to styrene and the catalytic properties. For the structural and physical analyses of ferrites, XRD, BET, TG/DTA, ESCA, TEM, and TPD methods were employed. The effects of Cr-substitution were intensively studied by the experimental methods mentioned above. Chromium which showed a preferential tendency to diffuse to the surface acted as a structural promoter by increasing surface area and stability of catalyst structure. In the dehydrogenation of ethylbenzene, catalytic activity, and the effects of Cr-substitution were investigated. Oxygen mobility was decreased with the amount of Cr-substitution in $MgCr_xFe_{2-x}O_4$, which resulted in the increase of selectivity to styrene and the suppression of total oxidation.