Citation
Burkett, Sandra Louise (1995) Mechanisms of structure direction in zeolite synthesis. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/t6kk-w159. https://resolver.caltech.edu/CaltechETD:etd-11102005-104907
Abstract
The mechanisms by which the geometries of organic structure-directing agents are translated into the product pore architectures in the synthesis of pure-silica and aluminosilicate zeolites are investigated by numerous spectroscopic techniques and variations in synthesis gel composition. For the tetrapropylammonium- and 1,6-hexanediamine-mediated syntheses of pure-silica ZSM-5 (Si-ZSM-5), 1H-29Si CP MAS NMR is performed between the protons of the organic species and the silicon atoms of the zeolite framework precursors in a deuterated synthesis medium to probe the interactions between the organic and inorganic components. The origin of structural specificity in the synthesis of pure-silica zeolites in the presence of structure-directing agents is attributed to the formation of favorable intermolecular van der Waals interactions within inorganic-organic composite species that form the key components in zeolite self-assembly. Investigation of the 1H-29Si CP MAS NMR profiles of silicate gels containing tetraalkylammonium cations that do not induce the formation of a crystalline zeolite product suggest the significance of hydrophobic hydration of the organic component in the formation of the inorganic-organic composite structures that is essential to the synthesis of pure-silica zeolites. For the syntheses of the hexagonal (EMT) and cubic (FAU) polymorphs of the aluminosilicate zeolite faujasite in the presence of 18-crown-6 and 15-crown-5, respectively, a combination of NMR and vibrational spectroscopic techniques and variations in the synthesis compositions are used to elucidate the structure-directing roles of the crown ethers. Sodium/crown ether complexes facilitate and direct the assembly of sodium-templated extended aluminosilicate structures via ion-dipole interactions to form the EMT and FAU products. Thus, for the synthesis of Si-ZSM-5 and the synthesis of EMT and FAU, two different mechanisms of structure direction and self-assembly via the formation of extended inorganic or inorganic-organic composite species are proposed.
Item Type: | Thesis (Dissertation (Ph.D.)) |
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Subject Keywords: | Chemistry ; zeolite synthesis |
Degree Grantor: | California Institute of Technology |
Division: | Chemistry and Chemical Engineering |
Major Option: | Chemistry |
Thesis Availability: | Public (worldwide access) |
Research Advisor(s): |
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Thesis Committee: |
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Defense Date: | 14 November 1994 |
Record Number: | CaltechETD:etd-11102005-104907 |
Persistent URL: | https://resolver.caltech.edu/CaltechETD:etd-11102005-104907 |
DOI: | 10.7907/t6kk-w159 |
Default Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. |
ID Code: | 4491 |
Collection: | CaltechTHESIS |
Deposited By: | Imported from ETD-db |
Deposited On: | 10 Nov 2005 |
Last Modified: | 16 Apr 2021 23:11 |
Thesis Files
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PDF (Burkett_sl_1995.pdf)
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