M.Sc. / Polymerization of a-olefins by metallocene-based catalysts, is an ever expanding field with current scientific research continuing in an endeavor to develop chiral catalysts with greater stereospecificity and activities. However, the application of metallocene catalysts in oligomerization reactions of a-olefins has been somewhat neglected. This is despite the fact that metallocene catalysis can offer a convenient route to the synthesis of higher a-olefin oligomers. Furthermore, by utilizing an assortment of functional group transformations, a-olefin oligomers can serve as intermediates for a variety of specialty chemicals. Notwithstanding the possibility of employing alternative ligands in catalysis, the use of non-cyclopentadienyl-based complexes is a topic that has only recently been considered. Comparative studies of a series of analogous complexes is lacking in this field and thus a pertinent study of a number of known metallocene complexes was executed in this project. Furthermore, an industrially applicable process for oligomerization was sought after. This was in fact achieved by subjecting the a-olefins 1-pentene, 1- hexene and 1-octene, to oligomerization conditions with a previously unreported and lowered methylaluminoxane ratio. This reaction proved to be highly selective to dimer formation of the three aforementioned higher a-olefins. In order to gain more insight into the oligomerization process, the progress of the reaction was also followed. Only zirconium complexes were synthesized and furthermore, the induction of oligomerization as opposed to polymerization (using compounds known to be active solely as polymerization catalysts), was attempted by increasing the reaction temperature. The second part of this project entailed the synthesis and subsequent testing of zirconium catalysts containing non-cyclopenatadienyl-based ligands. These complexes have frameworks with chelating phenolate or naphtholate ligands. These complexes were tested for oligomerization, but results proved to be negative.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:9016 |
| Date | 13 August 2012 |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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