Modification Of Mesoporous Silica And Preparation, Characterization And Properties Of The Mesoporous Composites

Great amount of work was dedicated to zeolites and related crystalline molecular sieves, the dimensions and accessibility of pores were restrained to the sub-nanometer scale. This limited the application of these pore systems to small molecules. Recently, ordered mesoporous materials with uniform pore diameters and high specific surface area have been widely used as catalysts, catalyst supports, chemical sensors, electrical and optical devices, hosts for the inclusion of compounds and nanosize clusters, and shape/size selective adsorbents for environmentally hazardous chemicals. In the early 1990s, the discovery of mesoporous materials offers an opportunity for silicate as versatile catalysts and catalyst supports for conversion of large molecules and molecule groups. However, the weak hydrothermal stability of these materials greatly limits their extensive uses.Periodic mesoporous silica SBA-15, as a developing material with periodic inorganic and surfactant-based structure, is a new type of mesoporous molecular sieve with larger pores, thicker walls, and much higher hydrothermal stability than MCM-41 which attracts researcher's attentions during the past years. SBA-15 molecular sieves attract considerable and increasingly growing attention because of their remarkable properties. They are easy to synthesize and their pore sizes can be tailored within a wide range. Surface properties of SBA-15 materials can be modified by incorporating heteroatoms. Moreover, plenty of silanol groups present in the amorphous SiO₂ wall, which can not only be used as functional groups but also be utilized to anchor other active sites. The ease of surface modification promises wide application of SBA-15 molecular sieves in many fields. Being promising catalysis or catalysis supporter, they should have uniform shape, be dispersive and not easy to agglomerate. But most of synthesized mesoporous materials have irregular shapes or sizes and tend to agglomerate, which will decrease the potential performance of this kind of nanomaterials and bring more difficulty to recycle in the coming application. Meanwhile, chemical modification was applied to various fields as a functionized method. More and more researchers have devoted to functionizing SBA-15 with organic or inorganic species and improving the properties of the mesoporous silica molecular sieves. This dissertation mainly consists of the following several aspects:1. Mesoporous silica SBA-15 was prepared through the hydrothermal treatment in strong acid media. The as-synthesized samples show the uniform pore size and long-distance ordered arrangement of hexagonal structure, which is typically ordered mesoporous structure. Though the orthogonal experiments, SBA-15 products with uniform morphology of bundles of pearl-like chains were obtained...