Toward a Unified Identification of Ti Location in the MFI Framework of High-Ti-Loaded TS-1: Combined EXAFS, XANES, and DFT Study
Toward a Unified Identification of Ti Location in the MFI Framework of High-Ti-Loaded TS-1: Combined EXAFS, XANES, and DFT Study
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在高钛负载 TS-1 的 MFI 框架中统一识别钛位置：EXAFS、XANES 和 DFT 组合研究
DOI：
10.1021/acs.jpcc.6b05087
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发表时间：
2016-09-15
影响因子：
3.7
通讯作者：
Chen, Dongliang
中科院分区：
文献类型：
--
作者：
Doug, Juncai;Zhu, Hailiang;Chen, Dongliang
Titanium silicalite-1 (TS-1) has been shown to be a heterogeneous catalyst with remarkable efficiency and selectivity; however, the nature of the active Ti site in the MFI framework remains elusive. Here we report combined experimental and theoretical research on Ti distribution in the 12 crystallographically distinct T sites of the MFI framework in high-Ti-loaded TS-1 (2.7 wt % in TiO2). Using a multishell fit to extended X-ray absorption fine structure, we show that T4 is the most populated site, in marked contrast to the preferential substitution sites and the definitely excluded sites assumed hitherto by diffraction studies. The identification is supported by a good agreement between calculated and experimental X-ray absorption near-edge structure studies and by full periodic density functional theory (DFT) computation. In spite of having the identical most favored site, the preference order for the remaining sites predicted by DFT does not fully match the experimental results. This suggests that Ti distribution in the resulting TS-1 framework is positively correlated with the thermodynamic stability of pure material but can be affected by other factors such as interdefects. These new insights may facilitate the bottom-up design of new zeolites with tailored catalytic performance and studies on mechanisms of various oxidation reactions.
