离子在岩道中的起源和稳定性
Meng Wang1, Nicholas R Jaegers1,2, Mal-Soon Lee1
1Institute for Integrated Catalysis , Pacific Northwest National Laboratory , Richland , Washington 99354 , United States.
Journal of the American Chemical Society
|January 31, 2019
概括
水显著改变了酸性石位,将布伦斯特德酸位转化为水合离子. 这种转化会影响质子的移动性和催化活性,即使水度低.
科学领域:
- 催化剂
- 材料科学
- 物理化学
背景情况:
- 酸性化物是各种化学过程中的重要催化剂.
- 水的存在可以显著地影响石的催化位点的性质和活性.
- 了解水-化物相互作用是优化催化性能的关键.
研究的目的:
- 通过与水的相互作用来研究酸Brønsted位点的分子水平变化.
- 描述形成的物种及其对质子移动性的影响.
- 阐明水在改变石的催化性质中的作用.
主要方法:
- 使用高分辨率固态核磁共振 (NMR) 光谱来研究水与地质石的相互作用.
- 基于密度功能理论 (DFT) 的初始分子动力学模拟用于在不同温度和水度下建模这些相互作用.
- 化学转移计算和与已知的酸性系统 (例如,HClO4) 的比较有助于物种识别.
主要成果:
- 水与酸Brønsted位相互作用,在广泛的水活性和温度范围内形成水合离子 (H3O+).
- 给这些水合离子分配了9ppm的特征性NMR信号.
- 增加水含量最初通过削弱键和形成离子-水团来增强质子的移动性,但过多的水可以阻碍它.
- 桥接基和水之间的快速质子交换发生在140°C以上,即使水的存在最小.
结论:
- 水从根本上改变了石的Brønsted酸位,将它们转化为离子.
- 热岩框架内的质子的移动性受到水度和温度的显著影响.
- 这些发现为热催化物诱导变化的机制提供了关键的见解,这与催化剂设计和过程优化有关.
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