Olefin polymerization on Cr(III)/SiO<inf>2</inf>: Mechanistic insights from the differences in reactivity between ethene and propene

Murielle F. Delley, C. S. Praveen, András P. Borosy, Francisco Núñez-Zarur, Aleix Comas-Vives, Christophe Copéret

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

© 2017 Elsevier Inc. Silica-supported well-defined Cr(III) sites, which polymerize ethene, are barely reactive towards propene while they copolymerize propene and ethene, a reactivity pattern similar to what is observed for the Phillips catalyst. In contrast to ethene, propene is only polymerized in low amounts and by a small fraction of sites, while during propene/ethene copolymerization small amounts of olefinic oligomers are formed. This difference of reactivity pattern among various olefins is further examined by DFT calculations using periodic amorphous models, focusing on the initiation of polymerization by olefin insertion into the Cr–O bond vs. the heterolytic C–H activation of the alkene. For both mechanisms, we found that the initial activation displays similar energetics for propene and ethene, while the subsequent propene insertion associated with chain growth becomes rather demanding, which rationalizes the observed difference of reactivity between ethene and propene.
Original languageAmerican English
Pages (from-to)223-230
Number of pages8
JournalJournal of Catalysis
DOIs
StatePublished - 1 Jan 2017

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