Study of Multi‐Site Nature of Supported Ziegler‐Natta Catalysts in Ethylene‐Hexene‐1 Copolymerization

Matsko, Mikhail A.; Echevskaya, L. G.; Захаров, В. А.; Nikolaeva, Marina; Mikenas, Tatiana B.; Vanina, Marina P.

doi:10.1002/masy.200950816

Cited by 39 publications

(48 citation statements)

References 24 publications

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“…1, curves 5 and 6). The increase in activity upon copolymerization on Ti‐based supported catalysts when compared with homopolymerization was noted earlier in numerous works 1, 6–10, 23, 24…”

Section: Resultssupporting

confidence: 67%

“…Thus, comonomer acts as an additional chain transfer agent upon copolymerization. However, it should be noted that in most studies6–8, 10, 11, the data on the effect of comonomer on M w of polymers were obtained upon copolymerization in the presence of hydrogen, which is the most efficient chain transfer agent and predominantly determines molecular weight of the resulting polymers. To obtain the more detailed quantitative data on the reactions of chain transfer with α‐olefins, it is reasonable to investigate the effect of α‐olefin on M w and molecular weight distribution (MWD) of polymers produced on supported Ziegler catalysts in the absence of hydrogen.…”

Section: Introductionmentioning

confidence: 99%

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Copolymerization of ethylene with α‐olefins over supported titanium–magnesium catalysts. II. Comonomer as a chain transfer agent

Nikolaeva

Matsko

Mikenas

et al. 2012

J of Applied Polymer Sci

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The data on the effect of comonomer (propylene and 1‐hexene) on molecular weight (Mw), molecular weight distribution (MWD), and content of terminal double bonds were obtained for ethylene/α‐olefin copolymers produced over a supported titanium–magnesium catalyst (TMC) upon polymerization in the absence of hydrogen. The experimental data on the effect of comonomer concentration on Mw of polymers were used to calculate the ratios between the effective rate constants of chain transfer with monomer and the propagation rate constant. It was shown that the effective rate constant of chain transfer with monomers increases in the row of monomers: ethylene < 1‐hexene < propylene. Meanwhile, the data on the effect of copolymers on content of terminal double bonds of various types demonstrate that different reactions of chain transfer with comonomer may simultaneously occur during copolymerization. It results in simultaneous formation of terminal vinylidene and trans‐vinylene bonds. Therefore, the calculated rate constants of chain transfer with comonomer are complex values, which include the rate constants of chain transfer with comonomer occurring via different mechanisms. The data on MWD, short chain branching (SCB) and terminal double bonds content of different types were obtained by molecular weight fractionation of copolymers followed by the analysis of narrow fractions. The analysis of the data on MWDs of SCB and terminal double bonds shows that active sites of the TMC are considerably heterogeneous with respect to the rates of different chain transfer reactions with monomers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

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Section: Resultssupporting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Copolymerization of ethylene with α‐olefins over supported titanium–magnesium catalysts. II. Comonomer as a chain transfer agent

Nikolaeva

Matsko

Mikenas

et al. 2012

J of Applied Polymer Sci

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“…In theory, each type of active site produces polymer with an MWD that can be described by Flory's most probable distribution. Using the resolution technique, the average molecular weight of polymer produced at each site, as well as the mass fraction of polymer produced at each site, were determined. The MWD curves for samples PP1, PP2, PP3, and PP4 produced over catalysts TMC‐PE and TMC‐PP (Figure ) were deconvoluted into Flory components.…”

Section: Resultsmentioning

confidence: 99%

A comparative study of ethylene and propylene polymerization over titanium–magnesium catalysts of different composition

Nikolaeva

Matsko

Mikenas

et al. 2014

J of Applied Polymer Sci

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New data on the molecular weight characteristics of polypropylene (PP) and polyethylene (PE) were obtained from the polymerization over supported titanium–magnesium catalysts differing in their compositions (presence and absence of internal and external donors). Internal and external donors were found to affect the molecular weight of polymers in a different manner for ethylene and propylene polymerization. The introduction of the internal donor increases the molecular weight of PP and does not affect the molecular weight of PE. The effect of external donor introduced to catalytic system on the polymer molecular weight depends on catalyst composition: for a catalyst without internal donor, the introduction of the external donor increases the molecular weight of PP and does not affect that of PE. In the case of catalyst with the internal donor, the introduction of the external donor increases the molecular weight of PP and substantially decreases that of PE. The data on polymerization degree of the polymers produced under conditions when chain transfer with hydrogen was the dominant reaction were used to calculate the ktr normalH/kp values for ethylene polymerization over the catalysts of different composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40658.

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“…Deconvolution is a technique used to identify the number of active site types and mass fraction and chain microstructures of polymers produced on each active site type. Deconvolution of MWD obtained from gel permeation chromatography (GPC) and deconvolution of CCD obtained from temperature rising elusion fractionation (TREF) or crystallization analysis fractionation (Crystaf), have been investigated. However, the discrepancy in the estimated number of active site types and mass fractions of polymers produced on each active site type has been reported when MWD and CCD of the same sample are deconvoluted separately .…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Deconvolution of MWD and CCD of Ethylene/1‐Olefin Copolymers Using Genetic Algorithm

Nanthapoolsub

Anantawaraskul

Saengkhamkhom

2013

Macromolecular Symposia

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Summary Multiple‐site‐type catalytic systems produce ethylene/1‐olefin copolymers with broad molecular weight distribution (MWD) and chemical composition distribution (CCD) because each active site type produces chains with distinct chain microstructures. Simultaneous deconvolution of the MWD and CCD can be used to identify the number of active site types and chain microstructures produced on each active site type by performing parameter estimation to minimize the sum of the squares of differences between experimental and model data. However, conventional optimization algorithms often rely on the adequate initial guess. In this work, a genetic algorithm, which is a stochastic optimization search heuristic that mimics the natural evolution process, was implemented during the simultaneous deconvolution. The proposed approach was validated with simulated data of model ethylene/1‐butene copolymers produced using a system with three active site types.

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Study of Multi‐Site Nature of Supported Ziegler‐Natta Catalysts in Ethylene‐Hexene‐1 Copolymerization

Cited by 39 publications

References 24 publications

Copolymerization of ethylene with α‐olefins over supported titanium–magnesium catalysts. II. Comonomer as a chain transfer agent

Copolymerization of ethylene with α‐olefins over supported titanium–magnesium catalysts. II. Comonomer as a chain transfer agent

A comparative study of ethylene and propylene polymerization over titanium–magnesium catalysts of different composition

Simultaneous Deconvolution of MWD and CCD of Ethylene/1‐Olefin Copolymers Using Genetic Algorithm

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