• Clean Technology
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• v.15 no.4
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• pp.273-279
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• 2009

$SF_6$, which has a high global warming potential, can be decomposed to sulfur and fluorine compounds through hydrolysis by $H_2O$ or oxidation by $O_2$ over solid acid catalysts. In this study ${\gamma}-Al_2O_3$ was employed as the solid acid catalyst for the abatement of $SF_6$ and its catalytic activity was investigated with respect to the reaction temperature and the space velocity. The catalytic activity for $SF_6$ decomposition by the hydrolysis reached the maximum at and above 973 K with the space velocity of $20,000\;ml/g_{-cat}{\cdot}h$, exhibiting a conversion very close to 100%. When the space velocity was lower than $45,000\;ml/g_{-cat}{\cdot}h$, the conversion was maintained at the maximum value. On the other hand, the conversion of $SF_6$ by the oxidation was about 20% under the same conditions. The SEM and XRD analyses revealed that the ${\gamma}-Al_2O_3$ was transformed to ${\alpha}-Al_2O_3$ during the hydrolysis and to $AlF_3$ during the oxidation, respectively. The size of $AlF_3$ after the oxidation was over $20\;{\mu}m$, and its catalytic activity was low due to the low surface area. Therefore, it was concluded that the hydrolysis over ${\gamma}-Al_2O_3$ was much more favorable than the oxidation for the catalytic decomposition of $SF_6$.

• Journal of the Korean Chemical Society
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• v.43 no.1
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• pp.85-91
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• 1999

The second order rate constants for the hydrolysis of substituted phenyl N,N-diethyl-P-benzylphosphonamidates (2,4-$(NO_2)_2$, 4-$NO_2$, 4-CN, 4-Cl, 4-H)in 20% dioxane-water (v/v) have been determined by UV/Vis spectrophotometric method at various temperatures. The activation parameters (Ea, ${\Delta}H^{\neq}$,${\Delta}S^{\neq}$) were calculated from the rate constants and the reaction constant ($\rho$) was also estimated by Hammett equation. The activation entropies of the title reactions show considerably negative values, this result is not consistent with a dissociative mechanism (EA) in which a positive or a slightly negative value of the entropy of activation should be expected. Further, kinetic evidence for an associative mechanism (AE) was obtained from the linear free energy relationship. By the results of kinetic study for the alkaline hydrolysis of substituted phenyl N,N-diethyl-P-benzylphosphonamidates, it may be concluded that these reactions proceed through an associative mechanism.

• KSBB Journal
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• v.19 no.1
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• pp.38-41
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• 2004

Enantioselective hydrolysis for the producing chiral epichlorohydrin from its racemic substrate was investigated using epoxide hydrolase activity of Rhodosporidium toruloides SJ-4. The effects of reaction parameters including pH, temperature, initial substrate concentration on initial hydrolysis rate and enantioselectivity were analyzed and optimized. The addition of detergent, Tween 20, enhanced the hydrolysis rate and enantioselectivity. Chiral (R)-epichlorohydrin with high optical purity (＞99% ee) and yield of 25% (theoretically 50% maximum yield) was obtained from its racemate of 20 mM.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.468-470
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• 2008

열중량반응기와 미분반응기를 이용하여 ABS의 열분해 및 생성물분포 특성을 연구하였으며 미분반응기를 이용한 실험의 열분해온도는 $410{\sim}450^{\circ}C$이었다. 각 상의 열분해생성물의 수율은 무게측정을 통해 얻었으며 액상생성물의 탄소수분포는 GC-SIMDIS 방법을 통해 측정하였다. 열중량 분석실험에서는 측정할 수 없었던 다량의 고상잔류물의 생성을 회분식 미분반응기실험을 통해 확인할 수 있었다. 반응온도와 시간이 증가할수록 액상생성물의 수율과 평균분자량은 감소하였으나 액상생성물 중의 스티렌모노머의 생성은 두드러지게 증가하였다. ABS 열분해 반응에서 말단절단의 속도계수인 활성화에너지 값은 54.1kcal/mole이었다.

• Journal of Nutrition and Health
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• v.9 no.4
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• pp.54-58
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• 1976

Deterioration of ascorbic acid content is the important factor in the food quality. The degradation of ascorbic acid undergoes as a first-order of reaction in the presence of excess oxygen content. However, under the limited oxygen content, ascorbic acid decomposes as a psudo-first order of reaction. The ascorbic acid, in this study, under the limited dissolved oxygen content in the presesce of iron(III) and copper(II) decomposed as first-order reaction with a little influence in rate constant and the light was an accelerating factor on the ascorbic acid degradation.

• Journal of the Korean Society of Tobacco Science
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• v.5 no.2
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• pp.55-62
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• 1983

Four of non- isothermal methods evaluating kinetics have been studied by using differential scanning calorimetry (DSC) and thermogravimetry (TG) and applied for kinetics of the thermal decomposition of cellulose. It is concluded that the heating evolution methods with DSC and approximative methods with TC can lead to satisfactory kinetic analysis. Results calculating the reacting order and the activation energy of cellulose decomposition were 1/2 order and 42kcaB/mol, respectively.

• Journal of Energy Engineering
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• v.14 no.2 s.42
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• pp.105-111
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• 2005

In this study, the photocatalytic degradtion of D-glucose with the micro channel reactor was performed on the various experimental conditions. To apply the $TiO_2$ coating on the micro channel reactor, $TiO_2$ solution was synthesized by hydrolysis of titanium oxysulfate. The feeding rate was proportional to degradation rate of D-glucose solution over the micro channel reactor. Also, the reaction rate constant and Langmuir adsorption coefficient were calculated under various experimental conditions. And the results of these system photonic efficiencies were calculated. This study aims to understand the photocatalytic degradation characteristics on $TiO_2$ coating in the micro channel reactor experimented by the feed batch reaction system.

• Journal of environmental and Sanitary engineering
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• v.13 no.1
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• pp.32-43
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• 1998

혐기성대상과정중 메탄생성균(methanogenic bacteria)에 의한 메탄생성시 주요 기질인 아세트산 (acetic acid)을 분해할 경우에 여러 가지 복합기질 중 아미노산 첨가에 의한 분해속도증가에 미치는 영향과 투입한 아미노산이 미생물에 의하여 생체량으로 합성되는 정도를 고찰하였다. 실험결과 메탄생성균은 glycine, serine, threonine, aspartic acid, trytophan 등의 혐기성미생물의 생체량합성에 필요한 물질을 투입할 경우에 아세트산의 분해속도가 증가하였으며, 여러 가지 아미노산을 혼합하여 주입한 결과 분해속도가 17% 향상되었다. 한편, 메탄생성균의 lysing에 의하여 생성된 유기물은 메탄이나 이산화탄소의 최종산물로 전환되기보다는 새로운 메탄생성균의 생체량을 형성하는데 직접 이용되었으며, 아세트산의 분해속도를 52% 증가시켰다. 단순기질(sole substrate)과 복합기질(complex substrate)의 분해는 미생물의 생체량합성에 필요한 여러 가지 중간대사산물간의 상호자극효과에 의하여 복합기질이 용이한 것으로 나타났으며, 유입기질내 활성이 강한 슬러지의 농도는 혐기성처리에 매우 중요한 부분을 차지하였다.

• Journal of the Korean Chemical Society
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• v.20 no.1
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• pp.48-55
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• 1976

The rate constants of the derivatives of N-(2,4-dinitrophenyl)-benzimidoyl chloride were determined at various pH and a rate equation which can be applied over wide pH range was obtained. The reaction mechanism of hydrolysis of N-(2,4-dinitrophenyl)-benzimidoyl chloride which has not been studied carefully earlier in acidic and basic solution can be fullly explained by the rate equation obtained. The rate equation reveals that, beow pH 7.00, the hydrolysis of benzimidoyl chloride proceeds through $S_N2$ reaction to form a carbonium ion intermediate.Above pH 8.5, however, the hydrolysis proceeds through the $S_N2$ type reaction which depends on hydroxide ion and imidoyl chloride concentration. At pH 7.0∼8.5, two reactions occur competitively.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.709-714
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• 2002

To investigate the decomposition kinetics of poly(ethylene terephthalate) the high pressure molten-polymer injector has been devised. Using the experimental apparatus equipped with batch reactor and high pressure molten-polymer injector the decomposition of PET has been performed at constant pressure of 250 bar and 300, 320, $340^{\circ}C$, respectively. At each temperature conditions the conversions after initial 1 minute have shown very high values such as 76-90%. As the temperature increases the conversion reaches more than 98% at 10 minutes. Based on the second order reaction model the reaction rate constants have been obtained. We can calculate the conversions within 2% errors utilizing optimized rate constants. The activation energy for the decomposition of PET at subcritical conditions has shown to be 54.4 kJ/mol.