Cr-based heterogeneous catalysts for olefin polymerization are responsible for a large fraction of the world's production of high density polyethylene. The active sites involve Cr-C bonds that are generated during initiation by reaction of an oxide-supported Cr precursor with ethylene. These sites were modeled by supporting organochromium precursors onto silica. Kinetic studies of ethylene polymerization show that alkylchromium(III) sites are kinetically competent while alkylchromium(IV) sites are not. Nevertheless, the mechanism by which such sites are formed from inorganic chromium(II) sites appears to involve alkylchromium(IV) intermediates. Candidates for these sites, which undergo Cr-C bond homolysis, and evidence for the initiation reaction in the industrial catalyst, will be discussed.

Molecular level understanding of heterogeneous catalysts for olefin polymerization

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.