过渡状态的和对n-基的解中的反应性和选择性的影响
David W Flaherty1, Enrique Iglesia
1Department of Chemical Engineering, University of California at Berkeley , Berkeley, California 94720, United States.
Journal of the American Chemical Society
|November 26, 2013
概括
度,而不是度,决定了金属催化剂上的n-基中的C-C键裂变. 这项研究解释了链条长度和旋转如何影响键断裂,这是碳化合物解的关键因素.
科学领域:
- 不同质的催化剂.
- 化学动力学 化学动力学
- 表面科学是一门学科.
背景情况:
- 碳化合物解对于能源和化学工业至关重要.
- 了解金属催化剂上的C-C键裂解机制对于过程优化至关重要.
- 以前的模型往往忽略了对反应速率和选择性的显著性贡献.
研究的目的:
- 阐明了基本的热力学和机械原理,控制了Ir,Rh和Pt集群上的n-基中的C-C键裂变.
- 解释对在确定C-C键裂变的速度和位置方面的占主导地位.
- 为碳化合物解提供可通用的框架,适用于各种催化系统.
主要方法:
- 统计力学和过渡状态 (TS) 理论的应用.
- 对过渡状态结构的动力数据和光谱证据的分析.
- 激活度 (ΔH‡) 和度 (ΔS‡) 的热力学处理.
主要成果:
- 在去除原子后,C-C键裂解率与中间覆盖率成正比.
- 观察到高激活度 (217257 kJ mol-1),独立于链条长度和键位.
- 由H2形成驱动的大型正激活 (164259 J mol-1 K-1),是键裂的主要因素.
- 链的链长和旋转决定了C-C键裂变的首选位置,解释了对非终端键的偏好.
结论:
- 对n-基解的动力学和选择性起着主导作用.
- 该模型准确地预测了基于链旋转的C-C键裂解位置.
- 这种机械和热力学方法将古典理论的实用性扩展到复杂的催化解反应.
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