• Bulletin of the Korean Chemical Society
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• 제22권8호
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• pp.889-896
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• 2001

The reaction of gas-phase atomic bromine with highly covered chemisorbed hydrogen atoms on a silicon surface is studied by use of the classical trajectory approach. It is found that the major reaction is the formation of HBr(g), and it proceeds th rough two modes, that is, direct Eley-Rideal and hot-atom mechanism. The HBr formation reaction takes place on a picosecond time scale with most of the reaction exothermicity depositing in the product vibration and translation. The adsorption of Br(g) on the surface is the second most efficient reaction pathway. The total reaction cross sections are $2.53{\AA}2$ for the HBr formation and $2.32{\AA}2$ for the adsorption of Br(g) at gas temperature 1500 K and surface temperature 300 K.

• 청정기술
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• 제17권4호
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• pp.370-378
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• 2011

가스상 원소수은의 산화수은으로의 산화에 대한 $V_2O_5-WO_3/TiO_2$ 계 SCR 촉매의 활성이 조사되었다. 상용 SCR 촉매의 경우 원소수은 산화반응에 산화제로 작용하는 HCl의 존재 및 반응조건에 상관없이 반응 후의 모든 촉매에서 수은성분이 검출되지 않았다. 이는 $V_2O_5-WO_3/TiO_2$ 계 SCR 촉매에서 HCl에 의한 원소수은의 산화는 수은이 촉매표면에 거의 흡착되지 않는 Eley-Rideal mechanism에 의해 진행되는 것을 나타내는 결과이다. $V_2O_5$ 함량에 따라 수은 산화활성이 크게 증가되는 것으로부터 $V_2O_5$가 수은산화 반응에 주된 활성점 임을 확인할 수 있었다. 그러나 $V_2O_5$ 함량에 따라 TOF는 감소하는데 이는 촉매 표면에 존재하는 $V_2O_5$의 구조에 따라 수은산화 활성에 차이가 있다는 것을 의미한다. 동일한 반응온도와 HCl 농도에서 산화 조건에 비해 SCR 조건에서 원소수은의 산화활성은 크게 낮은 것으로 나타났다.

• 공업화학
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• 제5권4호
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• pp.580-587
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• 1994

고정층 상압 유통식 반응기에서 메탄의 전화율 10% 미만의 범위에서 $Na^+(50wt%)/MgO$ 촉매를 사용하여 반응온도 710, 730, 750, 770, $790^{\circ}C$에서 메탄과 산소의 분압을 변화시켜 가면서 메탄의 oxidative coupling반응을 수행하여 이산화탄소와 에탄의 생성속도를 구하고 curve fitting으로 속도식을 증명하였다. Langmuir-Hinshelwood, Rideal-Redox, Eley-Rideal형 반응 메카니즘 중에서 Langmuir-Hinshelwood형 반응 메카니즘이 실험 결과와 가장 잘 일치하였으며, $CH_3{\cdot}$의 생성에 관여하는 산소종은 촉매 표면의 $O_2{^-}$ 또는 $O_2{^{2-}}$으로 제시할 수 있었고, 이때의 활성화 에너지는 약 39.3kcal/mol이었다. 또한, curve fitting결과 $CO_x$을 생성하는 산소의 화학 양론계수 x는 약 1.5이었으며, 이로부터 $CH_3{\cdot}$의 일부가 표면산소에 의해서 산화반응을 거쳐 $CH_3O_2{\cdot}*$ 형성을 추측할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제24권7호
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• pp.986-992
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• 2003

We have calculated the probability of the OH formation and energy deposit of the reaction exothermicity in the newly formed OH, particularly in its vibrational motion, in the gas-surface reaction O(g) + H(ad)/Si → OH(g) + Si on the basis of the collision-induced Eley-Rideal mechanism. The reaction probability of the OH formation increases linearly with initial excitation of the HSi vibration. The translational and vibrational motions share most of the energy when the H-Si vibration is initially in the ground state. But, when the initial excitation increases, the vibrational energy of OH rises accordingly, while the energies shared by other motions vary only slightly. The product vibrational excitation is significant and the population distribution is inverted. Flow of energy between the reaction zone and the solid has been incorporated in trajectory calculations. The amount of energy propagated into the solid is only a few percent of the available energy released in the OH formation.

• 태양에너지
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• 제15권2호
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• pp.91-99
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• 1995

분무열분해법으로 $SnO_2$ 박막을 증착하여 반응변수들이 증착에 미치는 영향을 연구하였다. 분무용액의 농도가 0.01M인 경우 증착온도가 낮을 때에는 증착과정이 표면반응의 지배를 받으며 증착온도가 증가함에 따라 $400^{\circ}C$까지는 물질전달의 지배율이 증가한다. $400^{\circ}C$ 이상에서는 분무압력이 낮을 때는 물질전달의 지배율이 증가한다. $400^{\circ}C$ 이상에서는 분무압력이 낮을 때는 물질전달에 의해, 분무압력이 높을 때는 표면반응에 의해 지배를 받는다. 분무용액의 농도가 증가함에 따라 증착속도는 증가하였으며 본 실험의 경우 Rideal-Eley 기구에 의해 증착반응이 일어났다. 기판의 온도가 증가함에 따라 증착속도는 증가하다가 $400^{\circ}C$ 이상에서는 균일한 핵생성에 의하여 증착속도는 감소하였다. 분무지속 시간에 비례하여 증착층의 두께는 증가하였으며 기판과 증착층간에는 물리적인 접착을 이루고 있다.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.985-994
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• 1997

The reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on Fe(110) surface is studied by use of classical trajectory procedures. Flow of energy between the reaction zone and bulk solid phase has been treated in the generalized Langevin equation approach. A London-Eyring-Polanyi-Sato energy surface is used for the reaction zone interaction. Most reactive events are found to occur in strong single-impact collisions on a subpicosecond scale via the Eley-Rideal mechanism. The extent of reaction is large and a major fraction of the available energy goes into the vibrational excitation of H2, exhibiting a vibrational population inversion. Dissipation of reaction energy to the heat bath can be adequately described using a seven-atom chain with the chain end bound to the rest of solid. The extent of reaction is not sensitive to the variation of surface temperature in the range of Ts=0-300 K in the fixed gas temperature, but it shows a minimum near 1000 K over the Tg=300-2500 K.

• 한국재료학회지
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• 제16권5호
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• pp.323-328
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• 2006

In situ electrical conductivity measurements on $V_2O_5WO_3/TiO_2$ catalysts were carried out at between 100 and $300^{\circ}C$ under pure oxygen, NO and $NH_3$ to investigate the reaction mechanism for ammonia SCR (selective catalytic reduction) de NOX. The electrical conductivity of catalysts changed irregularly with supply of NO. It was, however, found that the electrical conductivity change with ammonia supply was regular and the increase of electrical conductivity was mainly caused by reduction of the labile surface oxygen. The electrical conductivity change of catalysts showed close relationship with the conversion rate of NOx. Variation of conversion rate in atmosphere without gaseous oxygen also showed that labile lattice oxygen is indispensable in the initial stage of the de NOx reaction. These results suggest that liable lattice oxygen acts decisive role in the de NOx mechanism. They also support that de NOx reaction occurs through the Eley?Rideal type mechanism. The amount of labile oxygen can be estimated from the measurement of electrical conductivity change for catalysts with ammonia supply. This suggests that measurement of the change can be used as a measure of the de NOx performance.

• Korean Chemical Engineering Research
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• 제50권2호
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• pp.358-364
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• 2012

철 촉매를 이용한 Fischer-Tropsch 합성 반응과 수성 가스 전환 반응에 대한 반응 메커니즘과 반응 속도식을 5 채널 고정층 반응기를 이용하여 조사하였다. 실험 조건은, 반응물 합성가스 $H_2$/CO 비 0.5~2, 반응물 공급 유량 60~80 ml/min, 반응 온도 $255{\sim}275^{\circ}C$로서 반응 압력은 1.5 MPa을 유지하였다. F-T 합성 반응의 반응 속도식($r_{FT}$)은 반응 속도 결정 단계로서 분자로 흡착된 CO와 기상의 수소 분자와의 반응을 바탕으로 하는 Eley-Rideal 반응 메카니즘을 통해 계산되었고, WGS 반응의 반응 속도식($r_{WGS}$)은 formate 중간체 생성 반응을 반응 속도 결정 단계로 가정하여 결정되었다. 실험 결과, F-T 합성 반응의 반응 속도식과 WGS 반응의 반응 속도식은 각각 탄화수소 생성과 $CO_2$ 생성에 대한 반응 속도 실험값을 잘 모사하였고, 또한 power law에 근거한 CO 전환 반응에 대한 반응 속도식도 실험값과 잘 일치하였다. 이처럼, 각각의 반응 메카니즘을 바탕으로 도출된 반응 속도식($r_{FT}$, $r_{WGS}$, $-r_{CO}$)은 실험값과 여러 가지 기존 문헌에서 보고된 반응 속도식 모델과 잘 일치하였다.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1527-1533
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• 2011

The reaction of gas-phase atomic hydrogen with oxygen atoms chemisorbed on a silicon surface is studied by use of the classical trajectory approach. We have calculated the probability of the OH formation and energy deposit of the reaction exothermicity in the newly formed OH in the gas-surface reaction H(g) + O(ad)/Si${\rightarrow}$ OH(g) + Si. All reactive events occur in a single impact collision on a subpicosecond scale, following the Eley-Rideal mechanism. These events occur in a localized region around the adatom site on the surface. The reaction probability is dependent upon the gas temperature and shows the maximum near 1000 K, but it is essentially independent of the surface temperature. The reaction probability is also independent upon the initial excitation of the O-Si vibration. The reaction energy available for the product state is carried away by the desorbing OH in its translational and vibrational motions. When the initial excitation of the O-Si vibration increases, translational and vibrational energies of OH rise accordingly, while the energy shared by rotational motion varies only slightly. Flow of energy between the reaction zone and the solid has been incorporated in trajectory calculations, but the amount of energy propagated into the solid is only a few percent of the available energy released in the OH formation.

• Bulletin of the Korean Chemical Society
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• 제20권10호
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• pp.1136-1144
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• 1999

The collision-induced reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on a silicon (001)-(2×1) surface is studied by use of the classical trajectory approach. The model is based on reaction zone atoms interacting with a finite number of primary system silicon atoms, which then are coupled to the heat bath, i.e., the bulk solid phase. The potential energy of the Hads‥Hgas interaction is the primary driver of the reaction, and in all reactive collisions, there is an efficient flow of energy from this interaction to the Hads-Si bond. All reactive events occur on a subpicosecond scale, following the Eley-Rideal mechanism. These events occur in a localized region around the adatom site on the surface. The reaction probability shows the maximum near 700K as the gas temperature increases, but it is nearly independent of the surface temperature up to 700 K. Over the surface temperature range of 0-700 K and gas temperature range of 300 to 2500 K, the reaction probability lies at about 0.1. The reaction energy available for the product states is small, and most of this energy is carried away by the desorbing H2 in its translational and vibrational motions. The Langevin equation is used to consider energy exchange between the reaction zone and the bulk solid phase.