Synthesis Of Hierarchical Pentasil Zeolites Using Single Molecular Template

To enhance the accessibility of the catalytic active sites in the zeolites, improve the diffusion properties of zeolite and broaden the scope of its utility, hierarchical zeolites aggregated/assembled by the nanocrystals have been paid important attentions, In present, hierarchical zeolites can be synthesized by post-treatment or with additional secondary templates/additives added. This dissertation focuses on the synthesis, characterizations and catalytic properties of hierarchical Pentasil zeolites. There are three parts in the dissertation.In the first part, mesoporous ZSM-5 zeolites can be one-step synthesized using ethylamine, butylamine and n-octylamine as single template. The carbon chain length of templates and SiO2/AlO3 ratio influenced zeolite morphology. Using tetrapropyl ammonium bromide as template, the effect of template content and crystallization temperature combined with the catalytic activity were investigated. Hierarchical zeolite aggregate could be synthesized with tuned parameters, where smaller particles and larger mesopore volume led to higher activity in the alkylation reaction between phenol and tert-butanol.In the second part, silicalite-2 synthesized from a clear solution of TBAOH-TEOS-H2O was studied. The effects of template/SiO2, SiO2/Al2O3, H2O/SiO2 and crystallization time on the morphology of silicalite-2 were investigated. In the molar composition 0.25 TBAOH:1.0 TEOS:25 H2O, particles less than 50 nm are obtained. Low TBAOH/TEOS and H2O/TEOS favor the formation of silicalite-2 aggregates. Contrarily, silicalite-1 only showed isolated particles under otherwise same conditions.The third part is to synthesize MFI/MEL intergrowth zeolite. Using tetrabutyl ammonium hydroxide as single template, the addition of different small molecule additives led to the formation of MEL/MFI intergrowth zeolites. The effect of silicon source, template content, type and amount of small molecule additives were investigated. It shows that ethanol as additive is preferred. When alcohol/TEOS equals to 1, MEL/MFI intergrowth samples were obtained.