Of Poisons and Antidotes in Polypropylene Catalysis

Quenched‐flow studies of MgCl2‐supported Ziegler–Natta catalysts were combined for the first time with 13C NMR fingerprinting of the nascent polymer and conclusively proved that, depending on the catalyst formulation, propene polymerization can be slowed down significantly by the occurrence of the f...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2016-07, Vol.55 (30), p.8590-8594
Main Authors: Yu, Yue, Busico, Vincenzo, Budzelaar, Peter H. M., Vittoria, Antonio, Cipullo, Roberta
Format: Article
Language:English
Subjects:
alkenes
hydrogen
kinetics
NMR spectroscopy
polymerization
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Summary:Quenched‐flow studies of MgCl2‐supported Ziegler–Natta catalysts were combined for the first time with 13C NMR fingerprinting of the nascent polymer and conclusively proved that, depending on the catalyst formulation, propene polymerization can be slowed down significantly by the occurrence of the few regiodefects (2,1 monomer insertions), changing active sites into dormant sites. Catalysts modified with ethylbenzoate show little dormancy. The more industrially relevant phthalate based catalysts, instead, are highly dormant and require the presence of H2 to counteract the deleterious effect of this self‐poisoning on productivity and stereoselectivity. The occasional occurrence of regiodefects in Ziegler–Natta propene polymerizations has long been suspected to change active sites into dormant sites. Herein, combining quenched‐flow kinetic studies with 13C NMR fingerprinting of the nascent polymer, this behavior is shown to occur, but depends on system formulation. The data also confirm that H2 is a powerful antidote to catalyst self‐poisoning.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201602485