分子筛催化剂酸碱中心相互作用的固体核磁共振研究

Zeolite catalysts have been widely utilized in modern chemical and petrochemical industries due to their high catalytic activities, selectivity, and environmentally friendly properties. Both the framework structures and acidity/basicity properties have been demonstrated to play crucial roles in governing the catalytic performances. Therefore, a quantitative description of the roles of structural and acidic/basic properties on catalytic performances and reaction mechanism of the zeolite-catalyzed systems should be beneficial for the rational design of zeolite catalysts. To achieve this objective, state-of-the-art solid-state NMR (SSNMR) techniques are employed in the present object to, (i) develop a comprehensive characterization approach to evaluate the acidity/basicity properties of zeolite catalysts based on the corresponding NMR parameters of adsorbed probe molecules; (ii) determine the spatial interactions between various active centers (Brønsted/Brønsted acids, Brønsted/Lewis acids, Lewis/Lewis acids, acids/bases) by combining with advanced 2D spectroscopy; (iii) explore the influence of different modification conditions on the framework structures, acidity/basicity properties, and catalytic performances of zeolite catalysts. Furthermore, in conjunction with theoretical calculations, it is a promising and powerful tool capable of providing quantitative description of the relevant structure-activity correlations on the local surfaces of various solid catalysts, thus promoting our fundamental understanding of the reaction mechanism involved during heterogeneous catalysis at the molecular level, and further guiding the modification, design, and application of novel zeolite catalysts in the petrochemical industry.

由于具有环境友好、反应活性高等优点，分子筛在工业上应用非常广泛。分子筛的骨架结构与酸碱性共同决定其催化反应活性，然而，由于人们对分子筛结构、酸碱性与催化反应性能之间的构效关系认识不足，导致在工业分子筛催化剂的选择和改性方面存在诸多的盲目性。因此，如何准确定量地表征分子筛的结构与酸碱性就显得尤为重要。本项目拟建立一套完善的依据探针分子NMR谱学参数来评估分子筛催化剂酸碱特性的表征方法，同时结合先进的二维NMR相关谱技术研究不同强度的酸碱活性中心（B酸/B酸、B酸/L酸、L酸/L酸、酸/碱）之间的相互作用。并以此作为基础考察不同改性条件对分子筛骨架结构、酸碱特性及催化性能的影响。辅以理论计算，从宏观和微观两个层面揭示特定分子筛表现出优异催化反应性能的本质，从而准确构建分子筛结构、酸碱性与催化反应活性之间的构效关系，为工业催化剂的合成、选择与改性提供参考。

分子筛等固体催化材料的活性中心结构/酸性与其催化反应性能密切相关，准确构建活性中心结构/酸性与催化反应活性之间的构效关系能够为高效工业固体酸催化剂的合成、选择与改性提供理论指导，具有重要的现实意义与应用价值。针对这一固体酸催化领域亟待解决的关键基础前沿科学问题，本项目围绕固体催化材料的酸特性表征，取得了如下研究结果：1）拓展了NMR探针分子技术与二维NMR谱学相结合表征固体催化材料酸特性的方法，为不同活性中心之间空间相互作用机制的研究奠定了基础；2）利用拓展的NMR探针分子实验技术确定了几类分子筛和氧化物的酸特性，建立了样品中多活性中心之间的空间相互作用网络，并进一步揭示了几种活性中心的局域精细结构；3）结合NMR探针分子实验与理论模拟，阐明了固体催化剂活性中心结构/酸性与催化反应性能之间的关联。