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CuO/ZnO/Al2O3 촉매에서 저온 역수성가스 전환반응 속도 연구
Kinetic Study of the Reverse Water-Gas Shift Reaction over CuO/ZnO/Al2O3 Catalyst at Low Temperature
한국에너지기술연구원 분리공정연구센터, 305-343 대전시 유성구 장동 71-2
Separation Process Research Center, Korea Institute of Energy Research, 71-2, Jang-dong, Yusung-gu, Daejeon, 305-343, Korea
jmkim@kier.re.kr
HWAHAK KONGHAK, October 2003, 41(5), 558-563(6), NONE
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Abstract
역수성가스 전환반응(RWGS)의 CuO/ZnO/Al2O3에 대한 반응 메커니즘과 반응 속도식을 미분 반응기를 이용하여 조사하였다. 실험은 523 K, 2.9-5.7 atm 하에서 수행하였고, 반응 속도에 대한 반응물 농도 영향을 조사하기 위해 P0CO2와 P0H2를 변화시켰다. 그 결과 P0CO2와 P0H2가 작을 때에는 반응 속도가 두 반응물의 분앞에 모두 영향을 받으며, H2분압에 대한 반응 차수는 0이며, CO2 분압에 대한 반응 차수는 0.23으로 나타났다. 실험에서 얻은 결과를 power law와 Langmuir-Hinshelwood 메커니즘, 그리고 Cu가 활성점으로 작용하는 surface redox 메커니즘을 통해 모델링하였다. 그 결과 surface redox 메커니즘에서 유추된 반응 속도식은 power law에 의한 반응 속도식과 잘 일치하며, 여기서 계산된 r0는 실험에서 얻은 결과를 잘 나타냄을 알 수 있었다. 또한 생성물 P0CO에 대한 반응 속도 의존성 실험에서 surface redox 메커니즘에서 나타난 CO 농도와 반응 속도식 사이의 관계가 잘 일치함을 확인하였다. 이로서 523 K, 저온에서의 역수성가스 전환반응은 촉매의 활성점인 Cu의 산화-환원에 의한 surface redox 메커니즘에 의해 이루어짐을 알 수 있었다.
The kinetics and reaction mechanism of the reverse water-gas shift reaction (RWGS) over CuO/ZnO/Al2O3 catalysts were studied using a differential reactor. The experiments were carried out at 523 K and 2.9-5.7 atm. Effect of reactants composition on the reaction rate was checked by changing P0CO2 and P0H2. When the P0CO2 and P0H2 were low, the reaction rate was dependent on partial pressures of both reactants and there was a strong dependency on P0H2. At high P0CO2 and P0H2, reaction order with P0H2 was zero, and order with P0_x000D_
CO2 was 0.23. The data was analysed using rate equations based on power law, Langmuir-Hinshelwood mechanism, and surface redox mechanism in which Cu was considered as an active site. The reaction rate derived from surface redox mechanism matched well with the reaction rate derived from power law, and the calculated r0 values, based on surface redox mechanism, was in good agreement with the experimental values. Also, a linear relationship between P0CO and reaction rate indicated that the surface redox mechanism was operative under these conditions. Therefore, it was conclued that_x000D_
the RWGS at 523 K proceeds by surface redox mechanism via oxidation and reduction of the Cu active site.
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