Bai Risheng, Song Yue, Lätsch Lukas, Zou Yongcun, Feng Zhaochi, Copéret Christophe, Corma Avelino, Yu Jihong
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University Changchun 130012 China
Instituto de Tecnología Química, Universitat Politècnica de València-Consejo Superior de Investigaciones Científicas Valencia 46022 Spain
Chem Sci. 2022 Aug 29;13(36):10868-10877. doi: 10.1039/d2sc02679a. eCollection 2022 Sep 21.
In the MFI zeolite crystallization process, the classical crystallization mechanism based upon the addition of silica species is often concomitant with the nonclassical route that is characteristic of the attachment of silica nanoparticle precursors. However, the factors that govern the preferences for each mechanism remain unclear. In this work, we present the impact of switching between these two crystallization pathways on the active sites and the resulting catalytic performance of the titanosilicate TS-1 zeolite. By controlling the self-assembled precursor structures in the early crystallization stage which are mediated by the Ti and HO in the reaction system, we could achieve the preferred modes of crystal growth of the TS-1 zeolite. We indicate that by directing the predominant crystallization path from the classical to the nonclassical route, it is possible to generate more stable bridging peroxo species upon reaction with hydrogen peroxide, as confirmed by O solid-state nuclear magnetic resonance spectroscopy, thus substantially increasing the catalytic performance of the resulting TS-1 for olefin epoxidation.
在MFI型沸石的结晶过程中，基于添加硅物种的经典结晶机制通常伴随着以硅纳米颗粒前体附着为特征的非经典途径。然而，决定每种机制偏好的因素仍不清楚。在这项工作中，我们展示了在这两种结晶途径之间切换对钛硅酸盐TS-1沸石的活性位点和最终催化性能的影响。通过控制反应体系中由Ti和HO介导的早期结晶阶段的自组装前体结构，我们可以实现TS-1沸石晶体生长的优选模式。我们表明，通过将主要结晶路径从经典途径引导至非经典途径，与过氧化氢反应时有可能生成更稳定的桥连过氧物种，这通过O固态核磁共振光谱得到证实，从而大幅提高所得TS-1用于烯烃环氧化的催化性能。
