介孔多酸/有机硅复合材料的孔结构可控合成及催化性能研究

The design of active and recyclable mesostructured heterogeneous materials is one of the research topics and pioneer projects in the field of oxidation catalysis. In this project, a series of mesostructured organosilica impregnated polyoxometalates materials were developed by using one-step co-condensation technique. Alkyl bissilylated organosilicate agents as the matrix and polyoxometalates as the active components, composite materials with two-dimensional hexagonal p6mm, three-dimensional cubic Im3m, and three-dimensional interconnected pore geometries were obtained selectively by turning preparation conditions (like type of alkyl bissilylated organosilicate agents, type of triblock copolymer surfactant and using co-solvent). The composite materials were wellcharacterized by spectroscopy methods, X-ray diffraction analysis, transmission electron microscopy, and nitrogen sorption analysis to investigate the morphology and surface textural properties. And their catalytic performances were tested in the epoxidation of alkenes (styrene, cyclohexene, and 1-phenylcyclohexene), with O2 and H2O2 as an oxygen source. In this system, influences of experimental factors as well as the reaction mechanism are studied by the epoxidation of alkenes; meanwhile, the practical application of the system is evaluated through studies on the catalytic stability and reusability of the composite materials. It is expected to provide important fundamental data for practical application of the epoxidation.

设计制备不同孔几何形貌及可循环使用的介孔复合材料是氧化催化领域的研究热点。本项目采用一步合成技术制备结构骨架可控的有机硅负载多金属氧酸盐介孔复合材料。以桥联有机硅为载体、多金属氧酸盐为活性物种，通过调控制备条件可实现对介孔结构复合催化剂的孔道结构有序性和几何形貌的可控合成，可获得具有优异表面物理化学性质的二维六方，三维立方和三维交联结构的系列有序介孔多酸/有机硅复合材料。通过各种表征手段，阐明多金属氧酸盐与有机硅载体之间的相互作用机制。以直链烯烃、环烯烃及具有芳香结构的烯烃选择性氧化生成烯烃环氧化物的反应为模型反应，探索催化活性与催化剂骨架微观结构的关系，考查重要试验参数对催化剂催化性能的影响，并研究氧化催化反应的机理；考查骨架结构可控的多酸/有机硅复合催化剂活化处理手段和循环使用情况，为烯烃环氧化物的合成提供新思路，为其实际应用奠定基础。

探讨与理解固体酸非均相催化氧化及酸催化反应是催化化学研究的重要内容之一，对设计和制备高效基于固体酸的杂化催化材料具有重要指导意义。本项目采用桥联有机硅为载体、多金属氧酸盐为活性物种，通过调控制备条件获得具有优异表面物理化学性质的有序介孔多酸/二氧化硅以及多酸/有机硅复合材料。分别在双氧水作为氧化剂的条件下，研究了多酸/二氧化硅以及多酸/有机硅复合材料催化氧化苯乙烯的反应活性。发现多酸/二氧化硅以及多酸/有机硅复合材料的催化氧化活性与其表面物理化学性质、孔道结构的有序度和几何形貌、以及母体多酸的结构密切相关相关；实验结果发现，多酸/二氧化硅的催化体系，苯甲醛的产率为25.1%；而多酸/有机硅复合材料的催化体系，苯甲醛的产率上升到57.4%。在温和反应条件下，与无机硅负载多酸复合催化剂相比，有机硅负载多酸的复合催化剂大大的提高了苯甲醛的产率，且苯甲醛的选择性也较高。通过多酸/有机硅复合催化剂活化处理手段和循环使用实验，证实了多酸/有机硅复合催化剂至少可以循环使用三次而未见催化氧化活性降低，为其实际应用奠定基础。