Novel H+ -sulfori"ated poly( styrene-co-divinylbenzene) ion-exchange resins have been prepared with· higher acid strength and higher thermal stabilities than conventionai ion-exchange resins. An objective of the study has been to increase the understanding of the relationships between resins structures, acidities and acid catalytic activities in aqueous and non-aqueous media. Some related materials, supported sulfonic acid catalysts, have been prepared using HMS (hexagonal mesoporous silicas) and SBA 15 as supports. These catalysts were characterised in terms of surface area and pore size distribution from nitrogen adsorption, powder X-ray diffraction, cation exchange capacity, thermogravimetric analysis and FT-Raman spectroscopy. These functionalised inorganic materials have been compared with their organic counterparts to improve the understanding of these systems. Both of these ranges of catalysts, with varying level of sulfonation, have been characterised by ammonia adsorption microcalorimetry in the absence of solvent. The resulting molar enthalpies of ammonia adsorption have been interpreted in terms of the relative strength of acid sites. The same catalysts have also been neutralised in a titration microcalorimeter (TITRYS) in which the materials have been held under a solvent (water, acetonitrile, cyclohexane) and a base probe compound titrated into the sample cell in the same solvent. Molar enthalpies of neutralisation measured for thes'e solid acid catalysts in this way have been compared with molar enthalpies of neutralisc:!ion for similar acid groups (sulfonic acids) in homogeneous solutions. The resulting molar enthalpies of neutralisation in non-aqueous solvents have been interpreted in terms of the relative strength of acid sites. In addition, FT-Raman spectroscopy has been used to study the sulfonic acid groups in the resin gels and comparison made with similar acid groups in homogeneous aqueous solutions. These in turn have been compared with catalytic data measured for the sulfonated catalysts in three liquid phase reactions. Variation in measured acidity (with and without) solvent, catalytic activities have been interpreted in terms of structural features of the catalysts and their interaction with solvents.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:288505 |
| Date | January 2003 |
| Creators | Koujout, Said |
| Publisher | University of Huddersfield |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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