Ethylene Tetramerisation: A Structure-Selectivity Correlation

Boitumelo F. Makume, Cedric W. Holzapfel, Munaka C. Maumela, J. Alexander Willemse, Jan A. van den Berg

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

The effect of ethylene tetramerisation ligand structures on 1-octene selectivity is well studied. However, by-product formation is less understood. In this work, a range of PNP ligand structures are correlated with the full product selectivity and with catalyst activity. As steric bulk on the N-substituent increases, the product selectivity shifts from >10 % to < 3% of both C6 cyclics and C16+ by-products. 1-Octene peaks at ca. 70%. Thereafter, only 1-hexene increases. Similar selectivity changes were observed for ortho-Ph-substituted PNP ligands. The C10-14 selectivity was less affected by the ligand structure. The ligand effect on the changes in selectivity is explained mechanistically. Lastly, an increase in ligand steric bulk was found to improve catalyst activity and reduce polymer formation by an order of magnitude. It is proposed that steric bulk promotes formation of cationic catalytic species which are responsible for selective ethylene oligomerisation.

Original languageEnglish
Pages (from-to)2308-2315
Number of pages8
JournalChemPlusChem
Volume85
Issue number10
DOIs
Publication statusPublished - 1 Oct 2020

Keywords

  • ethylene oligomerisation
  • ligands
  • reaction mechanisms
  • selectivity
  • structure-activity relationships

ASJC Scopus subject areas

  • General Chemistry

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