This thesis concerns the hydrothermal stability of two zeolite molecular sieves with the MFI structure, ZSM-5 and its 'aluminium free' form silicalite. Silicalite was synthesised from low pH alkali metal free aqueous gels at 95°C and characterised by XRD, SEM, DTA and TG. ZSM-5 was crystallised from similar reaction mixtures but with the addition of aluminium salts. It was found that the incorporation of aluminium into the ZSM-5 framework was favoured by higher reaction temperatures (l50°C) and the use of aluminium nitrate. Solubilities were measured for silicalite, ZSM-5, ZSM-11, ZSM-39, ZSM-48 and EU-4 at temperatures up to 95°C. The solubilities were influenced by framework structure, the presence of template within the zeolite channels and the aluminium content of the lattice. Solubility measurements over a range of liquid/solid ratios showed that calcined silicalite was contaminated with about 1% amorphous silica. Treatment with liquid water over the temperature range 95 to 230°C was used to remove amorphous silica and alnminosilicate species from silicalite and ZSM-5. This hydrothermal treatment had many other effects on the properties of these materials. The water uptake, orthorhombic to monoclinic symmetry transition, framework Si/Al ratio and thermal properties were all affected. SEM showed that the inside of the silicalite crystals was more soluble than the outer surface. The use of hydrothermally treated H-ZSM-5 as a catalyst for but-1-ene isomerisation showed that the treatment could have a marked effect on catalytic behaviour, and particularly on product selectivity.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:234005 |
| Date | January 1988 |
| Creators | Young, David |
| Contributors | Lowe, B. M. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/9864 |
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