The Effect of Substituents in PNPN[BOND]H Ligands on Activity and Selectivity of a Chromium-Based Catalyst System for Highly Selective Ethylene Trimerization

Authors

  • Stefan Heinig,

    1. Linde AG, Linde Engineering Division, Dr.-Carl-von-Linde-Str. 6-14, 82049 Pullach (Germany), Fax: (+49) 8974454981
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  • Dr. Anina Wöhl,

    1. Linde AG, Linde Engineering Division, Dr.-Carl-von-Linde-Str. 6-14, 82049 Pullach (Germany), Fax: (+49) 8974454981
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  • Dr. Wolfgang Müller,

    Corresponding author
    1. Linde AG, Linde Engineering Division, Dr.-Carl-von-Linde-Str. 6-14, 82049 Pullach (Germany), Fax: (+49) 8974454981
    • Linde AG, Linde Engineering Division, Dr.-Carl-von-Linde-Str. 6-14, 82049 Pullach (Germany), Fax: (+49) 8974454981
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  • Dr. Mohammed H. Al-Hazmi,

    1. Saudi Basic Industries Corporation, P.O. Box 42503, Riyadh 11551 (Saudi Arabia)
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  • Dr. Bernd H. Müller,

    1. Leibniz-Institut für Katalyse an der Universität Rostock e.V. Albert-Einstein-Str. 29 A, 18059 Rostock (Germany), Fax: (+49) 381128151176
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  • Dr. Normen Peulecke,

    1. Leibniz-Institut für Katalyse an der Universität Rostock e.V. Albert-Einstein-Str. 29 A, 18059 Rostock (Germany), Fax: (+49) 381128151176
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  • Prof. Dr. Uwe Rosenthal

    Corresponding author
    1. Leibniz-Institut für Katalyse an der Universität Rostock e.V. Albert-Einstein-Str. 29 A, 18059 Rostock (Germany), Fax: (+49) 381128151176
    • Leibniz-Institut für Katalyse an der Universität Rostock e.V. Albert-Einstein-Str. 29 A, 18059 Rostock (Germany), Fax: (+49) 381128151176
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Abstract

The influence of ligand substituents on a highly selective homogeneous catalyst system for the trimerization of ethylene to 1-hexene consisting of chromium(III) acetylacetonate, a ligand with a PNPN[BOND]H backbone, tetraphenylphosphonium chloride as chlorine source, and triethyl aluminum as activator was investigated. These N-modified and P-modified ligands, which differ strongly in their electronic and steric properties of the substituents, were tested in the ethylene trimerization at three temperatures (50, 70, and 90 °C). Interestingly, the substituents at the N atoms of the PNPN[BOND]H-backbone had only little effect on the catalytic activity, on 1-hexene selectivity, and on thermal stability of the catalyst system, whereas the substituents at the P atoms significantly influenced the efficiency of the system. This is even more surprising as the PNP ligand from SASOL for ethylene tetramerization is much more sensitive against substituent variation at its N atom.

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