Preparation of higher alpha olefin oligomers

M.Sc.The economic growth of a country can be stimulated by value-adding to basic resources e.g., chemical intermediates. Alpha olefins are products of the Sasol Fischer-Tropsch process and oligomerization is one of the most significant beneficiation processes available for these alpha olefins. Alpha olefin oligomers obtained from the cationic oligomerization with BF3/ROH, have been used mainly as base stocks in synthetic lubricants. These oligomers consist of a mixture of isomeric products that complicates the investigation and rational modification of this and other closely related oligomerization processes. A comparison of these isomeric mixtures to alkane standards could assist in the study of these processes, but almost no standards are available. This project was aimed, in part, at establishing a methodology for the synthesis of 1-pentene model oligomers. A model branched 1-pentene dimer and trimer as well as a precursor to the analogous tetramer were prepared. The syntheses of other model oligomers in conjunction with the comparison of the properties of model oligomers with different branching patterns will certainly be of value. Some of the main classes of catalysts were evaluated for the oligomerization of higher alpha olefins and especially of 1-pentene. The BF3/n-BuOH cationic oligomerization of 1-pentene yielded dimers, trimer, tetramers and pentamers consisting of a large number of isomers and the product distribution peaked at the trimer. This is in agreement with previous results for other monomers. Radical oligomerization of 1-pentene with organic peroxide initiators proceeded in low yield. Dimers and trimers consisting of a mixture of isomers were mainly formed. Metallocene catalysts offer a convenient route to single component, structurally well characterized alpha olefin oligomers. A variety of functional group transformations and consequent applications are possible for these oligomers. The general nature of the oligomerization of 1-pentene, 1-hexene and 1-octene with allocene/methylaluminoxane catalysts was investigated. The influence of different metals, the number of cyclopentadienyl groups and substitution on the cyclopentadienyl groups in the metallocene moiety, the reaction temperature and the purity of the monomer were studied. By employing the appropriate metallocene in combination with methylaluminoxane, higher alpha olefin dimers and trimers could be formed in high yield at ambient temperatures. Cp2ZrC12 was the most active of the metallocene catalysts and single isomers were formed with high selectivity. The etallocene-based oligomerization of higher alpha olefins offers great scope for further research and promises a new era in olefin oligomerization