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Titanium-based phenoxy-imine catalyst for selective ethylene trimerization: effect of temperature on the activity, selectivity and properties of polymeric side products

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Abstract

The reactivity of a phenoxy-imine-ether system (FI)TiCl3/MAO was studied toward selective ethylene trimerization. This system was shown to either trimerize or polymerize ethylene depending on the reaction temperature. Its selectivity switches from a significant production of the trimerization product, 1-hexene (85 wt%, 520–450 kg1-hexene gTi−1 h−1) between 30 and 40 °C, to a moderate polyethylene formation (70–80 wt%, 60–70 kgpolyethylene gTi−1 h−1) at a higher reaction temperature (T > 60 °C). Polymerization was investigated based on an original “polymer-to-catalyst” strategy aiming at identifying the active species responsible for this side reaction. Using DSC, SEC and high temperature 13C NMR analyses, polyethylenes were found to exhibit high molar masses (>105 g mol−1) and a low 1-hexene content (<1 mol%) at any temperature. Kinetic studies support that trimerization and polymerization species are generated from the catalyst precursor at 40 °C but a parallel process may occur at a higher temperature. The increase of dispersity to 4.6 at 80 °C suggests a change from single to multi-site catalysis. The poor comonomer incorporation ability of the active species is reminiscent of a molecular Ziegler–Natta or a bulky post-metallocene catalyst.

Graphical abstract: Titanium-based phenoxy-imine catalyst for selective ethylene trimerization: effect of temperature on the activity, selectivity and properties of polymeric side products

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Supplementary files

Article information


Submitted
11 Oct 2019
Accepted
04 Dec 2019
First published
09 Dec 2019

Catal. Sci. Technol., 2020, Advance Article
Article type
Paper

Titanium-based phenoxy-imine catalyst for selective ethylene trimerization: effect of temperature on the activity, selectivity and properties of polymeric side products

A. Cordier, P. Breuil, T. Michel, L. Magna, H. Olivier-Bourbigou, J. Raynaud, C. Boisson and V. Monteil, Catal. Sci. Technol., 2020, Advance Article , DOI: 10.1039/C9CY02056J

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