Crystallization and Catalytic Applications of Mesoporous Silica

This thesis is composed of two parts: the first part focuses on the application of heterogeneous catalysts in Kharasch reaction; the second part focuses on the synthesis of the ZSM-5 crystalline framework in the structure of SBA-15 in order to improve the catalytic activities. n the first part, CuCl/bipyridine catalysts were immobilized to mesoporous materials including SBA-15, SBA-1 and MCM-41 with or without amino-functional groups by absorption in solvents. The supported catalysts were used for cyclisation of unsaturated tri-halogenated compound. These kinds of cyclisation reactions are also called Kharasch reaction which is often catalyzed by homogeneous catalysts. The Cu (I) catalyst was easily leached when CH2Cl2 was the solvent, while the leaching problem was avoided by using toluene as the solvent. Although pure CuCl/bipyridine is not as efficient in catalyzing Kharasch reaction in toluene as in CH2Cl2, higher reaction rate was obtained in toluene over the supported materials. The activity and recycling of the catalysts were discussed. In addition, the effects of different supports, microwave technology, and the combination of ionic liquid in Kharasch reaction were studied. n the second part, we tried to synthesize ZSM-5/SBA-15 composite materials. Both ZSM-5 and SBA-15 are porous SiO2 material. ZSM-5 has crystalline framework and relative high acidity. It is an effective catalyst in many acid-catalyzed reactions. However, its pore size limits its applications from reactions involving macromolecules. SBA-15 has an ordered mesoporous structure, good thermal stability, but a relatively low acidity because its framework is amorphous. The purpose of this work is to transform the amorphous framework of mesoporous SBA-15 to the crystalline microporous wall. Tetrapropylammonia bromide (TPABr) was used as the template to synthesize crystalline framework and as-synthesized SBA-15 (without calcination) is the silicon source. The reaction conditions including pH value and the reaction time of crystallization for the synthesis of SBA-15 were varied to find the optimal reaction condition. In addition Al3+ ions were introduced to the framework of SBA-15 to examine the acidity of the Al-SBA-15 materials.