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이원금속 촉매의 접촉개질 반응 성능 연구
Ⅰ. Pt-Mo 이원금속의 특성과 반응성
Studies of Bimetallic Catalysts Performance in Naphtha Reforming
1. The Nature and Reactivity of Pt-Mo Bimetallic Catalysts
HWAHAK KONGHAK, February 1997, 35(1), 29-34(6), NONE
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Abstract
γ-Al2O3에 담지된 Pt-Mo 이원금속의 특성에 대한 전ꑦ적인 연구를 27Al NMR, 129Xe NMR, TEM 그리고 수소흡착 측정 등을 통하여 수행하였다. 또한 n-hexane 탈수소고리화 반응을 선정하여 연구하였다. Pt-Mo 이원금속 시료들에 대한 129Xe NMR 스펙트럼에서의 화학적 변위는 Mo의 양을 증가시킴에 따라 줄어들었다. 이것은 Pt-Mo 이원금속입자의 형성을 의미한다고 볼 수 있다. 1wt% Pt/γ-Al2O3에 Mo를 0.1-0.5wt% 첨가한 Pt-Mo 이원금속 촉매의 n-hexane 탈수소고리화 반응에 대한 촉매 반응성은, 비활성성분인 Mo가 Pt입자의 표면을 덮음으로써 활성성분들인 Pt을 잃어버리게 되기 때문에, Mo의 양이 증가함에 따라 급격히 줄어들었다. 그러나 1wt% Pt/γ-Al2O3에 0.01wt% Mo를 첨가한 Pt-Mo 이원금속 촉매의 경우는 활성이 증가하였다. 이것은 Mo가 아주 소량으로 첨가된 경우에는 Pt와 γ-Al2O3 사이의 계면에 존재하게 되어 Pt 입자를 안정화시키고 전자적인 효과도 발생되기 때문에 반응성이 촉진되는 것으로 사료된다.
The formation of Pt-Mo bimetallic clusters on γ-Al2O3 has been investigated using magic angle spinning 27Al NMR spectroscopy, 129Xe NMR spectroscopy, transmission electron microscopy, hydrogen chemisorption and catalytic dehydrocyclization of n-hexane. The chemical shift in 129Xe NMR for the Pt-Mo/γ-Al2O3 system decreased with the addition of Mo, indicating the formation of Pt-Mo bimetallic clusters. The formation of the bimetallic clusters with the addition of 0.1-0.5wt% Mo to 1wt% Pt/γ-Al2O3 led to a remarkable decrease in the catalytic activity, probably due to the Pt atoms being masked physically by the Mo atoms located on the surface of the Pt particles. On the contrary, the catalytic activity increased significantly when 0.01wt% Mo was added. The small quantity of Mo seemed to be located at the Pt-alumina interface, stabilizing the cluster by anchoring to the support. Electronic effects due to the Mo addition may also be suggested to enhance the activity.
Keywords
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