Towards Selective Ethylene Tetramerization

dc.contributor.authorShaikh, Yacoob
dc.description.abstractThere is an increasing trend towards advancing the understanding and development of ethylene oligomerization catalysts, both in academia and industry. The metal of choice in this chemistry is invariably chromium, which has shown great versatility in selective trimerization/tetramerization, non-selective oligomerization and polymerization of ethylene. While much success has been achieved in ethylene trimerization, the same con not be said about tetramerization catalysis. Aminophosphine based ligands have demonstrated their ability towards selective 1-octene production, however, the popular PNP catalyst is able to achieve only 70% selectivity. In order to explore the possibility of developing and enhancing the selectivity of chromium based ethylene tetramerization catalyst, this thesis work was undertaken. The ligand systems we chose for our work were bidentate aminophosphine based (PN(CH2)nNP), which has yielded interesting selective oligomerization. Subtle modifications were found to result in drastic changes in selectivity, from tetramerization (PN(CH2)3NP) to trimerization (PN(CH2)2NP). We managed to successfully develop the first truly selective (over 90%) 1-octene catalyst with polymer-free behavior. Further modifications on the ligand framework, where one atom of Si was used to link the two NP units, resulted in non-selective oligomerization, in which case we determined that the oxidation-state of chromium is a key player. We explored other modifications on our selective ligands in which one of the arms on the bidentate ligand was replaced with a base-donor amine, phosphine or pyridine, and resulted in interesting selectivity changes. The final modification that we tested was a novel N(CH2)2P ligand and found it to be a highly active, non-selective oligomerization catalyst.
dc.publisherUniversité d'Ottawa / University of Ottawa
dc.subjectYacoob Shaikh
dc.subjectEthylene Tetramerization
dc.subjectselective oligomerization
dc.subjectchromium catalysis
dc.subjectligand synthesis
dc.subjectnon-selective oligomerization
dc.subjectethylene trimerization
dc.subjectring-expansion mechanism
dc.subjectbi-metallic mechanism
dc.subjectlinear alpha olefin
dc.subjectethylene oligomerization
dc.subjectkhalid albahily
dc.subjectsandro gambarotta
dc.subjectNP ligand
dc.titleTowards Selective Ethylene Tetramerization
dc.faculty.departmentChimie / Chemistry
dc.contributor.supervisorGambarotta, Sandro
dc.embargo.termsimmediate / Science / Science
uottawa.departmentChimie / Chemistry
CollectionThèses, 2011 - // Theses, 2011 -

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