固体酸中多活性中心协同作用的超快魔角旋转固体NMR研究

Solid acid catalysts, an new type of environmentally friendly catalysts, have been used extensively in chemical and petroleum industries to replace the highly corrosive, hazardous, and polluting liquid acids. The acidic properties and structures of active sites in solid acid catalysts play a crucial role in the adsorption behavior of reactant molecules, the scission and rearrangement of chemical bonds, resulting in the formation of intermediates and products, thus endowing solid acid catalysts with special catalytic activities. Solid-state NMR has been proven to be a powerful tool to study the surface acidity and the interactions among various active sites in solid acids. Especially the application of ultrafast magic angle spinning (MAS) techniques, which has significantly grown in recent years thanks to the progresses in both probe and magnet technology, is becoming a new advanced solid-state NMR technique in the fields of the structure analysis, as well as the catalytic behaviros. In this proposal, our research will focus on the synergy among multi-active-sites in solid acids. It is necessary to develope a new two dimensional double-quantum ultrafast MAS NMR techniques to study the detailed acid features and synergistic effect among various active sites in solid acids at relative high field. The combination of ultrafast MAS technique with DFT quantum chemical calculations, will provide new insights into the synergy mechanism of several typical solid acid catalysts, and improve the synthesis, modification and applications of solid acids.

固体酸是一种环境友好型催化剂，在石油化学工业中越来越多的固体酸被用来替代高腐蚀、高危险与高污染的液体酸。固体酸催化剂的表面酸性、活性中心结构直接影响反应物分子的吸附方式、化学键断裂及重组，进而影响反应中间体和产物的生成，因此决定了其独特的催化反应性能。固体核磁共振是研究固体酸催化剂表面酸性和各种活性中心之间相互作用的一种强有力手段，超快魔角旋转是近年来随着固体NMR谱仪硬件发展所产生的一种新的核磁共振技术。本项目主要针对固体酸中多活性中心之间的协同作用开展研究工作。发展较高场下用于固体酸表面酸性位（活性中心）结构及相互作用研究的二维超快魔角旋转同核双量子固体NMR新方法，采用超快魔角旋转条件下的各种高级固体NMR实验技术并结合量化计算，揭示几类典型的固体酸催化剂中各种活性中心之间协同作用的微观机制，为多相催化机理的研究，高性能固体酸催化剂的合成、改性和应用提供理论基础。

脱铝分子筛的酸性、催化活性和选择性都比其相对应的未脱铝分子筛提高很多，脱铝分子筛中各种活性中心之间的协同作用一直以来都吸引了大量学者的关注。本项目采用1H 双量子固体NMR（DQ-MAS NMR）研究了脱铝沸石分子筛中Brønsted/Lewis之间的空间邻近性，采用27Al DQ-MAS NMR研究了脱铝分子筛中骨架铝和非骨架铝之间的空间邻近性。采用NMR探针分子技术研究了脱铝分子筛的酸性，发现酸性明显增强，证实了在脱铝分子筛中存在Brønsted/Lewis协同效应。研究了不同类型分子筛协同效应之间的差异。另外，固体核磁共振在功能材料研究方面也取得了一序列阶段性进展。