The work presented in this thesis addressed the synthesis, characterization and application of new type of zeolite materials possessing micro-/mesoporous structural hierarchy.
Zeolite is a crystalline material possessing uniform micropores (0.3 < diameter < 2 nm) of molecular dimension. The molecular sieving ability of zeolite has enabled the creation of selective separation (ion exchange, sorption, etc.) and catalytic processes. In particular, zeolites with various structures constitute one of the most widely used classes of acid catalyst in industry. However, in many applications, slow diffusion into the microporous structure imposes a diffusion limitation on reaction rate. The diffusion limitation also accelerates coke formation at pore entrances, which significantly reduces catalytic activity and recyclibility of zeolite catalysts. To solve these problems, several attempts to synthesize zeolite with a large external surface area, hence with facile molecular diffusion into zeolite structure, were made in the past. In the present work, zeolites possessing tunable mesoporous structure were synthesized by adding a rationally designed amphiphilic organosilane surfactant into conventional alkaline zeolite synthesis mixtures. The zeolite products were rigorously characterized by a complementary combination of X-ray diffraction (XRD), $N_2$ adsorption, scanning and transmission electron microscopy. The analysis results reveal that the present method is suitable as a direct synthesis route to ‘hierarchical’ zeolites that contain secondary mesoporosity as well as the intrinsic zeolite microporosity. The mesopore diameters can be finely tailored, similar to the ordered mesoporous silicas having amorphous frameworks. The hierarchical zeolite exhibited a narrow, small-angle XRD peak, which is characteristic of the short-range correlation between mesopores, similar to disordered wormhole-like mesoporous materials.
The synthesis of the crystalline aluminosilicate mater...