The Role of Catalyst Support, Diluent and Co-Catalyst in Chromium-Mediated Heterogeneous Ethylene Trimerisation

Lamb, M.J.; Apperley, D.C.; Watson, M.J.; Dyer, P.W.

Abstract

Sequential treatment of a previously-calcined solid oxide support (i.e. SiO2, γ-Al2O3, or mixed SiO2–Al2O3) with solutions of Cr{N(SiMe3)2}3 (0.71 wt% Cr) and a Lewis acidic alkyl aluminium-based co-catalyst (15 molar equivalents) affords initiator systems active for the oligomerisation and/or polymerisation of ethylene. The influence of the oxide support, calcination temperature, co-catalyst, and reaction diluent on both the productivity and selectivity of the immobilised chromium initiator systems have been investigated, with the best performing combination (SiO2−600, modified methyl aluminoxane-12 {MMAO-12}, heptane) producing a mixture of hexenes (61 wt%; 79% 1-hexene), and polyethylene (16 wt%) with an activity of 2403 g gCr−1 h−1. The observed product distribution is rationalised by two competing processes: trimerisation via a supported metallacycle-based mechanism and polymerisation through a classical Cossee-Arlman chain-growth pathway. This is supported by the indirect observation of two distinct chromium environments at the surface of the oxide support by a solid-state 29Si NMR spectroscopic study of the Cr{N(SiMe3)2}x/SiO2−600 pro-initiator.

Citation

Lamb, M., Apperley, D., Watson, M., & Dyer, P. (2018). The Role of Catalyst Support, Diluent and Co-Catalyst in Chromium-Mediated Heterogeneous Ethylene Trimerisation. Topics in Catalysis, 61(3-4), 213-224. https://doi.org/10.1007/s11244-018-0891-8

• Journal Article Type: Article
• Online Publication Date: Jan 16, 2018
• Publication Date: Apr 1, 2018
• Deposit Date: Jan 31, 2018
• Publicly Available Date: Jan 31, 2018
• Journal: Topics in Catalysis
• Print ISSN: 1022-5528
• Electronic ISSN: 1572-9028
• Publisher: Springer
• Peer Reviewed: Peer Reviewed
• Volume: 61
• Issue: 3-4
• Pages: 213-224
• DOI: https://doi.org/10.1007/s11244-018-0891-8
• Public URL: https://durham-repository.worktribe.com/output/1367460