• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.152-152
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• 2013

Mechanism of energy conversion from chemical to electrical during exothermic catalytic reactions at the metal surfaces has been a fascinating and crucial subject in heterogeneous catalysis. A metal-semiconductor Schottky nanodiode is novel device for direct detection of chemically induced hot electrons which have sufficient energy to surmount the Schottky barrier. We measured a continuous chemicurrent during the hydrogen oxidation under of 760 Torr of O2 and 6 Torr of H2 by using Pt/Si and Pt/TiO2 nanodiodes at reaction temperatures and compared the chemicurrent with the reaction turnover rate. The thermoelectric current was measured by carrying out an experiment under O2 condition for elimination of the background current. Gas chromatograph and source meter were used for measurement of the chemical turnover rate and the chemicurrent, respectively. The correlation between the chemicurrent and the chemical turnover rate under hydrogen oxidation implies how hot electrons generated on the metal surface affect hydrogen oxidation.

• 자원리싸이클링
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• 제26권4호
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• pp.3-8
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• 2017

산화-환원반응은 수용액에서 일어나는 여러 중요한 반응중 하나이다. 산화-환원반응의 평형을 해석하는 것은 습식제련에서 침출, 분리 및 전기화화반응과 같은 단위공정을 설계하는데 있어 큰 도움이 된다. Frost도를 작성하는 방법을 설명하고, Frost도와 Latimer 표로부터 불균등화반응과 균등화반응이 일어나는 조건을 해석하였다. 또한 Frost도로부터 얻을 수 있는 정보에 대해 고찰하였다.

• Membrane and Water Treatment
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• 제9권6호
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• pp.405-419
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• 2018

Persulfates (i.e., peroxymonosulfate and peroxydisulfate) are capable of oxidizing a wide range of organic compounds via direct reactions, as well as by indirect reactions by the radical intermediates. In aqueous solution, persulfates undergo self-decomposition, which is accelerated by thermal, photochemical and metal-catalyzed methods, which usually involve the generation of various radical species. The chemistry of persulfates has been studied since the early twentieth century. However, its environmental application has recently gained attention, as persulfates show promise in in situ chemical oxidation (ISCO) for soil and groundwater remediation. Persulfates are known to have both reactivity and persistence in the subsurface, which can provide advantages over other oxidants inclined toward either of the two properties. Besides the ISCO applications, recent studies have shown that the persulfate oxidation also has the potential for wastewater treatment and disinfection. This article reviews the chemistry regarding the hydrolysis, photolysis and catalysis of persulfates and the reactions of persulfates with organic compounds in aqueous solution. This article is intended to provide insight into interpreting the behaviors of the contaminant oxidation by persulfates, as well as developing new persulfate-based oxidation technologies.

• 한국응용과학기술학회지
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• 제17권2호
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• pp.89-93
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• 2000

The oxidation of methane was carried out in six different configurations of plasma reactors in order to study the radical reactions inside and outside of the plasma zone and to explore the method to control them. Various radicals and reactive molecules, such as CH, $CH_{2}$, $CH_{3}$, H, and O(from $O_{2}$) were generated in the plasma. A variety of products were produced through many competing reaction pathways. Among them. partial oxidation products were usually not favored, because the intermediates leading to the partial oxidation products could be oxidized further to carbon dioxides easily. It is important to control the free radical reactions in the plasma reactor by controlling the experimental conditions so that the reactions leading to the desired products are the major pathways.

• 공업화학
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• 제28권6호
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• pp.619-625
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• 2017

본 연구에서는 하이드로퍼옥시 라디칼 생성단계에서 반응 부산물로 생성되는 과산화수소를 정량하여 수산화라디칼의 생성 및 비스페놀 A (BPA)의 분해특성을 조사하였다. 라디칼 연쇄반응이 일어나지 않는 조건에서는 Criegee mechanism과 동일하게 오존에 의한 직접산화반응만이 BPA를 분해시키는 것으로 나타났다. 라디칼 연쇄반응이 일어나는 pH 6.5 및 9.5의 조건에서는 비선택적 산화반응이 일어나 수산화라디칼의 생성을 간접적으로 확인할 수 있었다. 투입된 촉매에 의한 BPA의 분해효율은 $O_3$/PAC ${\geq}$ $O_3/H_2O_2$ > $O_3$/high pH > $O_3$ alone 공정 순으로 나타났다. 오존/촉매공정들의 산화반응 동안에는 0.03~0.08 mM의 과산화수소가 지속적으로 측정되었다. $O_3$/high pH 공정의 경우, BPA가 반응시작 50 min 만에 완전히 분해되었지만, TOC (총유기탄소) 제거율은 29%로 산화반응 중 생성된 중간물질을 충분히 산화시키지 못하는 것으로 나타났다(선택적 산화반응). $O_3/H_2O_2$ 및 $O_3$/PAC 공정에서는 BPA가 반응시작 40 min 만에 완전히 분해되었으며, TOC 제거율은 각각 57% 및 66% 정도로 반응 중간체들을 산화(비선택적 산화반응)시키는 것으로 나타났다.

• 대한화학회지
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• 제61권4호
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• pp.204-210
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• 2017

이 연구에서는 2009개정 교육과정 및 화학 I 교과서에 제시된 전자 이동 모델과 산화수 변화 모델의 서술방식을 분석하고, 화학교육전공 교사들을 대상으로 각 모델의 제한 조건에 대한 인식을 알아보았다. 교육과정과 교과서에서는 전자 이동 모델, 산화수 변화 모델을 제시하고 있으나, 각 모델의 제한 조건을 무시한 혼성 모델도 있었다. 혼성 모델은 공유결합 물질의 산화 환원 반응을 전자 이동 모델로 기술하거나 산화수 개념으로 설명하는 경우에도 가상적인 전자 이동과 실제적인 전자 이동을 혼동하게 하는 문제를 가진다. 산화 환원 반응에 대한 화학교육전공 교사들의 인식을 조사하기 위하여 설문지 및 면담을 실시하였다. 연구 결과, 많은 교사들이 각 모델의 제한 조건을 인식하지 못하고 있었으며, 혼성 모델로 인해 산화 환원 반응을 산 염기반응과 구분하는데 어려움을 가지는 것으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제27권1호
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• pp.106-110
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• 2006

Photocatalytic electron transfer reactions of aryl benzyl sulfides using 2,4,6 triphenylpyrilium tetrafluoroborate ($TP^+BF_4^-$) resulted in the oxidation of these sulfides to the corresponding sulfoxides and also in most cases in the C-S bond cleavage of them along with formation of aromatic aldehydes. In these reactions, the formation of sulfide radical cation has been proposed, which undergoes either oxidation to the corresponding sulfoxide or C-S bond cleavage to the formation of aromatic aldehydes. The further oxidation of sulfoxides to sulfones has not been observed. The influence of substrate structures on the reaction pathways as well as the role of $O_2$ in this respect is discussed.

• 한국수산과학회지
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• 제6권1_2호
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• pp.37-43
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• 1973

In this paper, non-enzymatic browning reactions as a factor of self stability of boiled and dried anchovy were studied to discuss the effect of water activity to the discoloring reaction and the preservative moisture content. The development of rancidity of the fish meat was also mentioned since the fish is fatty and the lipid oxidation is a functional deteriorative reaction. Fresh anchovies were boiled in $10\%$ salt solution immediately after the catch, sun dried, and stored at room temperature ($20^{\circ}C$) for two months in humidistat chambers maintaining different levels of water activity as described in Table 1. The pigments formed by non-enzymatic browning reations were extracted in two fractions, those were chloroform-methanol soluble and water dialyzed fraction, and analyzed spectrophotometrically at the wavelength of 460 nm. These two fractions were considered, respectively to be the brown pigments formed by lipid oxidation reactions for the formler and for the latter, to be the pigments developed by sugar-amino or Maillard reaction. The oxidation of lipid in anchovy meat during the storage was measured as the changes in Peroxide value and the color development of thiobarbituric acid reaction. It is summarized from the results that the rate of both reactions, lipid oxidation and browning, was affected by water activity levels. In regard to the changes in peroxide and TBA value during the storage, the propagation of lipid oxidation was obviously accelerated at lower humidities whereas the development of browning progressed at the higher. These two reactions occurring simultaneously and contrary in activity resulted in that the rate of deterioration occurring oxidatively or by browning, was the minimum at the water activity of 0.32-0.45 which were $7-9\%$ as moisture content and slightly higher value than that of monolayer (Aw=0.21, $5.11\%$ as moisture content). It is also noted that the lipid oxidative browning was presumed to dominate sugar-amino reactions so that the rate of browning of the meat was ultimately depended on the development of rancidity although sugar-amino reactions initiated earlier than the other at the first ten days of storage, particulary at higher humidity. At the lower humidity sugar-amino reactions were occurred gradually but lower levels in color development in contrast to the consistent increase in lipid oxidative browning.

• Carbon letters
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• 제18권
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• pp.18-23
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• 2016

Polyacrylonitrile (PAN)-based carbon fibers have high specific strength, elastic modulus, thermal resistance, and thermal conductivity. Due to these properties, they have been increasingly widely used in various spheres including leisure, aviation, aerospace, military, and energy applications. However, if exposed to air at high temperatures, they are oxidized, thus weakening the properties of carbon fibers and carbon composite materials. As such, it is important to understand the oxidation reactions of carbon fibers, which are often used as a reinforcement for composite materials. PAN-based carbon fibers T300 and T700 were isothermally oxidized in air, and microstructural changes caused by oxidation reactions were examined. The results showed a decrease in the rate of oxidation with increasing burn-off for both T300 and T700 fibers. The rate of oxidation of T300 fibers was two times faster than that of T700 fibers. The diameter of T700 fibers decreased linearly with increasing burn-off. The diameter of T300 also decreased with increasing burn-off but at slower rates over time. Cross-sectional observations after oxidation reactions revealed hollow cores in the longitudinal direction for both T300 and T700 fibers. The formation of hollow cores after oxidation can be traced to differences in the fabrication process such as the starting material and final heat treatment temperature.

• 한국응용과학기술학회지
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• 제22권1호
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• pp.56-61
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• 2005

Methanol was synthesized by homogeneous and catalytic reactions of partial oxidation of methane. The effect of pressure, temperature and oxygen concentration on methanol synthesis was investigated. The catalyst used was Bi-Cs-Mg-Cu-Mo mixed oxide. The partial oxidation reaction was carried out in a fixed bed reactor at 20${\sim}$46 bar and $450{\sim}480^{\circ}C$ and oxygen concentration of 5.3${\sim}$7.7mol%. The results were compared with results of homogeneous reaction performed at the same conditions. Methane conversions of the homogeneous and catalytic reactions increased with temperature. Methanol selectivity of the homogeneous reaction decreased with increasing temperature. However, the methanol selectivity of catalytic reaction increased with temperature. For both homogeneous and catalytic reactions, the methane conversions were around 5%. This may be due to the low oxygen concentration. Methanol selectivity of the catalytic reaction was higher than that of homogeneous one.