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从¹⁵N固态NMR和TiK边缘X射线吸收的TS-1中的反应部位的性质

Lukas Lätsch¹, Christoph J Kaul¹, Alexander V Yakimov¹

¹Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 2 Zurich 8093, Switzerland.

Journal of the American Chemical Society

|October 21, 2024

概括

含的焦化物 (TS-1) 是主要的催化剂. 新的低温15N ssNMR和XANES方法揭示了Ti位点的详细结构和反应性,这对于选择性氧化反应至关重要.

科学领域:

不同质的催化
材料科学
固态化学

背景情况:

含的化物,特别是化-1 (TS-1),是使用过氧化进行选择性氧化的重要异质催化剂.
尽管进行了广泛的研究,但TS-1内的Ti位点的精确结构和反应性仍然不完全理解.
使用探针分子进行的表征提供了洞察力,但尚未完全阐明这些催化中心的动态性质.

研究的目的:

综合描述TS-1中的Ti位点,重点关注它们在各种条件下的结构,反应性和动态行为.
通过量化易斯酸位及其在催化过程中的作用来确定TS-1催化剂的结构-活性关系.
为了证明低温15N ssNMR和Ti K-edge XANES方法对详细催化剂分析的有用性.

主要方法:

低温15N神奇角旋转 (MAS) 固态NMR (ssNMR) 光谱使用吸附作为探针分子.
在不同的条件下对一系列TS-1样本进行TiK边缘X射线吸收近边缘结构 (XANES) 光谱 (脱水,水化,用H2O2,用皮里丁).
计算机建模以补充实验数据并阐明反应机制.

主要成果:

脱水的TS-1主要表现出易斯酸位,而添加水则产生布伦斯特德酸位,其度与水负载相关.
结合15N ssNMR和Ti K-edge XANES方法,可以量化易斯酸位点,并开发结构-活性描述器.
与H2O的反应导致酸性桥梁西拉诺位 (Ti-OH-Si) 的形成,并使Ti协调从4到5发生变化,这是XAS证实的.

结论:

该研究使用先进的光谱技术成功阐明了TS-1中Ti位点的详细结构和动态反应性.
开发的方法提供了一个强大的工具来量化TS-1催化剂中的活性位点和建立结构-活性关系.
了解布伦斯特德酸位的形成和Ti的协调变化对于优化TS-1在选择性氧化反应中的性能至关重要.

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