Issue 6, 2020

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

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

Supplementary files

Article information

Article type
Paper
Submitted
11 10 2019
Accepted
04 12 2019
First published
09 12 2019

Catal. Sci. Technol., 2020,10, 1602-1608

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, 10, 1602 DOI: 10.1039/C9CY02056J

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