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Issue 3, 2016
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Structure–performance relationships of Cr/Ti/SiO2 catalysts modified with TEAl for oligomerisation of ethylene: tuning the selectivity towards 1-hexene

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Abstract

A study on the influence of H2 and the degree of titanation of a Cr/SiO2 Phillips polymerisation catalyst on the selective oligomerisation of ethylene induced by pre-contacting the catalyst with triethylaluminium (TEAl) is presented. Ethylene oligomerisation reactions were performed at 373 K and 1 bar, inside a quartz reactor of a specially designed operando experimental setup, which allowed examination of the catalysts by UV-vis-NIR diffuse reflectance spectroscopy, while the gas phase was continuously monitored by on-line mass spectroscopy and subsequently analysed by gas chromatography. With this combination of techniques, it was possible to acquire detailed insight into the different distributions of produced oligomers, which were highly dependent on the catalyst structure. The addition of small amounts of Ti significantly changes the electronic environment of Cr oligomerisation sites by the formation of Cr–O–Ti–O–Si linkages, favouring β-H transfer and increasing the selectivity towards butene at the expense of 1-hexene. Moreover, we show that ethylene oligo-/polymerisation reactions follow at least two different pathways, i.e. metallacycle for olefinic species with a broken Schulz-Flory distribution, and Cossee–Arlman for other hydrocarbon species.

Graphical abstract: Structure–performance relationships of Cr/Ti/SiO2 catalysts modified with TEAl for oligomerisation of ethylene: tuning the selectivity towards 1-hexene

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Publication details

The article was received on 08 Sep 2015, accepted on 27 Oct 2015 and first published on 18 Nov 2015


Article type: Paper
DOI: 10.1039/C5CY01512J
Citation: Catal. Sci. Technol., 2016,6, 731-743
  • Open access: Creative Commons BY-NC license
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    Structure–performance relationships of Cr/Ti/SiO2 catalysts modified with TEAl for oligomerisation of ethylene: tuning the selectivity towards 1-hexene

    D. Cicmil, I. K. van Ravenhorst, J. Meeuwissen, A. Vantomme and B. M. Weckhuysen, Catal. Sci. Technol., 2016, 6, 731
    DOI: 10.1039/C5CY01512J

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