Determination of the number of active centers in Ziegler-Natta polymerizations of olefins

Mejzlík, Jiří; Lesná, Marie; Kratochvíla, Ján

doi:10.1007/bfb0037613

Cited by 22 publications

(11 citation statements)

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“…The conclusion was that x * is low (between 1 and 10 %), but whether this holds at later stages of the polymerization is unclear. Alternatively, the growing chains can be labeled with radioactive tags (such as 14 CO or CH 3 OT); this approach yielded somewhat larger x * values (up to 20 %), but the underlying chemistry is delicate, and the possibility of multiple tagging or partial inclusion of aluminum‐bound chains in the count cannot be ruled out.…”

Section: Typical Formulations and Performance Of Mgcl2‐supported Zn Cmentioning

confidence: 99%

Of Poisons and Antidotes in Polypropylene Catalysis

Busico

Budzelaar

et al. 2016

Angew Chem Int Ed

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Quenched-flow studies of MgCl2 -supported Ziegler-Natta catalysts were combined for the first time with (13) C 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.

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Section: Typical Formulations and Performance Of Mgcl2‐supported Zn Cmentioning

confidence: 99%

Of Poisons and Antidotes in Polypropylene Catalysis

Busico

Budzelaar

et al. 2016

Angew Chem Int Ed

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“…chain. More, side reactions have been already identified with Ziegler-Natta catalyst systems with this technique[74,77,78,80]. In addition, CO can insert under a fast regime into the Zrpolymeryl bond but can also further react under a slower regime to give multiple insertion products or copolymerization[38,65,76,77].…”

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confidence: 99%

Quantification of active sites in single-site group 4 metal olefin polymerization catalysis

Desert

Carpentier

Kirillov

2019

Coordination Chemistry Reviews

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This review gives an overview of approaches and techniques used for the assessment of active sites count in homogeneous group 4 metal single-site α-olefin polymerization. The main advantages and limitations of these methods, in particular their ability to selectively and quantitatively discern the catalytic sites effectively at work, leaving aside dormant sites and other metal species not directly involved in propagation, as well as the results of their application onto some important single-site olefin polymerization catalyst systems are exemplified. The associated mechanistic information is of interest for engineering more efficient catalytic systems reluctant towards side reactions.

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“…[7] Figure 3 shows a linear relation between the number of macromolecules and the polymer yield. Extrapolation to zero yield allows evaluation of the number of active sites.…”

Section: Initial Kinetic Profilementioning

confidence: 99%

“…Extrapolation to zero yield allows evaluation of the number of active sites. This can be expressed by: [7,10] …”

Section: Initial Kinetic Profilementioning

confidence: 99%

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Diffusion Interface Technique for Determination of Initial Polymerization Kinetics

Skoumal

Cejpek

Chêng³

2005

Macromol. Rapid Commun.

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Summary: A new procedure for the investigation of initial kinetics in a slurry olefin polymerization with a Ziegler‐Natta catalyst has been developed. It is based on the accurate timing of short polymerizations that result from the immediate start of a reaction between a catalyst separated in an oil phase and the remaining components of the system upon their being mixed together. The polymer samples are suitable for 13C NMR analysis and the number of active sites could be calculated.

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Determination of the number of active centers in Ziegler-Natta polymerizations of olefins

Cited by 22 publications

References 0 publications

Of Poisons and Antidotes in Polypropylene Catalysis

Of Poisons and Antidotes in Polypropylene Catalysis

Quantification of active sites in single-site group 4 metal olefin polymerization catalysis

Diffusion Interface Technique for Determination of Initial Polymerization Kinetics

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