形成一个稳定的表面氧金属循环,产生乙烯氧化物
1Center for Catalytic Science and Technology, Department of Chemical Engineering, University of Delaware, Newark, Delaware 19716, USA.
Journal of the American Chemical Society
|January 10, 2002
概括
银表面上的乙烯氧化物 (EO) 形成了一个稳定的中间体,表面氧金属循环,可以环闭以再生EO. 这一发现对于理解白银催化乙烯环氧化至关重要.
科学领域:
- 表面科学是一门学科.
- 不同质的催化剂.
- 化学动力学 化学动力学
背景情况:
- 乙烯环氧化是一种重要的工业过程.
- 精确的银催化乙烯环氧化机制仍在研究中.
- 了解表面中间体是优化催化效率的关键.
研究的目的:
- 为了研究乙烯氧化物 (EO) 在Ag111表面的吸附和反应途径.
- 为了确定在EO反应中形成的表面中间体的性质.
- 为了阐明表面中间体在白银催化乙烯环氧化中的作用.
主要方法:
- 温度编程消毒 (TPD) 是指温度编程消毒的方法.
- 高分辨率电子能量损失光谱 (HREELS) 是一种高分辨率的电子能量损失光谱.
- 密度函数理论 (DFT) 的计算.
主要成果:
- 氧化在140K时分子吸附,在200K时无反应地去吸附.
- 在250K时,EO经历环开裂,形成稳定的表面中间体,被确定为氧金属循环.
- 氧金属循环中间体可以在300K反应以重塑EO,激活能量与乙烯环氧化相匹配.
结论:
- 这项研究提供了表面氧金属循环环闭合形成EO的第一个证据.
- 氧金属循环被提议作为白银催化乙烯环氧化中的关键中间体.
- 来自单晶和支持的催化剂的光谱数据支持氧金属循环的意义.
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