An investigation into the effect of framework constituents on the sorption properties of MFI-type zeolites and AEL-type zeotypes has been carried out. ZSM-5 with different amounts of framework aluminium was readily syn-thesised. It was found that the distribution of template (tetrapropylammo-nium ions, TPA) between a low and a high temperature form, and the water capacity of the calcined zoelites both depended linearly on the aluminium content. The temperature of oxidative degradation of the template and the energy associated with this degradation were also found to depend upon the aluminium content. A series of TPA-silicalites with different alkali and alkaline earth metal ions has been prepared. The sodium and potassium forms were found to crystallise most rapidly, while the barium and the caesium ones were considerably slower. AEL-type zeotypes have been prepared from aluminophosphate gels containing different amounts of silicon. These did not produce materials with the expected Al/P ratio of one. The amount and degradation temperature of the template and the zeotype water capacity after template removal were found to depend on the framework aluminium content; in these cases this appears the dominant framework component. An attempt was made to synthesise a series of microporous silicophos-phates and, although crystalline products were prepared, their structures could not be determined and they could not be obtained in a form suitable for sorption studies. An isopiestic equilibration technique was used to study the sorption of glycerol and a series of sodium alkylsulphonates from aqueous solution. The glycerol uptake was found to depend upon the framework aluminium content; ZSM-5 with approximately 1 aluminium per unit cell was found to be most effective. The sorption behaviour was also found to depend on the cation in the silicate, the effects being larger than expected in view of the small number of inorganic ions occluded during synthesis. The framework aluminium content was also found to be important for the sorption of glycerol by the AEL materials. These zeotypes were insufficiently resilient to lattice attack for the sorption of the alkylsulphonates to be studied. The MFI materials, however, showed a gradation in sorption properties, which could be interpreted in terms of the hydrophilicity/hydrophobicity of both the zeolite frameworks and the alkylsulphonate sorbates, though the results are less clear cut than those obtained with glycerol and there may be other important considerations.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:663434 |
| Date | January 1991 |
| Creators | Walters, Gordon H. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13185 |
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