Recent data on the number of active centers and propagation rate constants in olefin polymerization with supported ZN catalysts

Захаров, В. А.; Букатов, Г. Д.; Барабанов, А. А.

doi:10.1002/masy.200450903

Cited by 39 publications

(36 citation statements)

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“…As compared to the data reported in literatures for ethylene and propylene homopolymerizations with similar supported ZN catalysts, the initial values of k pE and k pP reported in this work are similar to those reported by Zakharov et al 33 but evidently lower than those reported by Terano and coworkers 34 The ratio of k pE /k pP was the highest in the first 30 s, and then decreased with time. As compared to the data reported in literatures for ethylene and propylene homopolymerizations with similar supported ZN catalysts, the initial values of k pE and k pP reported in this work are similar to those reported by Zakharov et al 33 but evidently lower than those reported by Terano and coworkers 34 The ratio of k pE /k pP was the highest in the first 30 s, and then decreased with time.…”

Section: Rate Constantssupporting

confidence: 89%

Kinetics of short‐duration ethylene–propylene copolymerization with MgCl₂‐supported Ziegler–Natta catalyst: Differentiation of active centers on the external and internal surfaces of the catalyst particles

Khan

Guo

Zhang

et al. 2017

J of Applied Polymer Sci

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Ethylene-propylene copolymerization with a TiCl 4 /MgCl 2 type ZN catalyst was conducted for different durations from 30 to 600 s, and changes of polymerization rate, concentration of active centers ([C*]) and copolymer chain structure with time were traced. The copolymerization rate decayed with time, but [C*]/[Ti] increased in the same period. This was attributed to release of more active sites through disintegration of catalyst particles by the growing polymer phase. Ethylene content of the copolymer quickly decreased in the period of 30-90 s, meaning that the active centers activated in the reaction process have stronger ability of incorporating propylene than those activated at the very beginning. The copolymer samples were fractionated into two parts, namely n-heptane soluble fraction (random copolymer) and insoluble fraction (segmented copolymer with high ethylene content). With continuation of the copolymerization, active centers producing the random copolymer chains increased much faster than active centers producing the segmented copolymer chains, and became the dominant centers after 120 s. Consequently, proportion of the soluble fraction sharply increased with time. All these results indicate that the active centers located on the external surface of catalyst particles are highly different from those buried inside the particles.

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Section: Rate Constantssupporting

confidence: 89%

Kinetics of short‐duration ethylene–propylene copolymerization with MgCl₂‐supported Ziegler–Natta catalyst: Differentiation of active centers on the external and internal surfaces of the catalyst particles

Khan

Guo

Zhang

et al. 2017

J of Applied Polymer Sci

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“…The ratios between the rate constant of chain transfer to comonomer and the propagation rate constant for propylene ( k

_{tr}^{Pr}

) and 1‐hexene ( k

_{tr}^{Hex}

) are equal to 1.7 × 10 −4 and 4.4 × 10 −5 , respectively. It was found in Ref 28. that k p upon ethylene polymerization on TMC is equal to 1.2 × 10 4 L mol −1 s −1 .…”

Section: Resultsmentioning

confidence: 95%

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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“…They are somewhat higher than that of the TiCl 4 /MgCl 2 -AlEt 3 catalyst (12 000 L Á (mol Á s) À1 at 70 8C). [22] Effect of Support on the Number of Active Centers, Propagation Rate Constant and PE Molecular Mass and MMD According to the data in ref. [7] homogeneous LFeCl 2 -MAO and LFeCl 2 -AlR 3 catalysts are almost inactive at elevated polymerization temperatures (!50 8C).…”

Section: Effect Of Hydrogen On the Number Of Active Centers And Propamentioning

confidence: 99%

Kinetic Study of Ethylene Polymerization Over Supported Bis(imino)pyridine Iron (II) Catalysts

Барабанов

Букатов

Захаров

et al. 2006

Macro Chemistry & Physics

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Summary: The number of active centers (CP) and propagation rate constants (kP) for polymerization of ethylene with supported catalysts LFeCl2/SiO2, LFeCl2/Al2O3 and LFeCl2/MgCl2 (L = 2,6‐(2,6‐(Me)2C6H3NCMe)2C5H3N), activated by an Al(i‐Bu)3 co‐catalyst, were determined by a method of polymerization inhibition with radioactive 14CO. In contrast to homogeneous systems based on LFeCl2, the supported catalysts are highly active and stable in ethylene polymerization at 70–80 °C. In the presence of hydrogen, the activity of the supported catalysts substantially increases (2–4 fold). The data obtained on the effect of hydrogen on the calculated CP and kP values suggests that for ethylene polymerization without hydrogen, the “dormant” active centers are formed in the catalytic systems. A scheme for the formation of these “dormant” centers and their reactivation in presence of hydrogen is suggested. For the investigated supported catalysts the CP values were found to be only 2 to 4% of the total iron complex content in the catalysts. The kP value for the catalysts prepared using different supports (SiO2, Al2O3 and MgCl2) were close (3.2 × 104 to 4.5 × 104 L · (mol · s)−1 at 70 °C). The support composition affects neither the molecular mass (MM) nor the molecular mass distribution (MMD) of the polymers produced. The obtained CP and kP values and data on the polymer MM and MMD lead to conclusion that the nature of the support has almost no effect on the structure of the active centers and the distribution of their reactivity.Effect of support on the MMD of PE produced over supported LFeCl2 catalysts.magnified imageEffect of support on the MMD of PE produced over supported LFeCl2 catalysts.

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Recent data on the number of active centers and propagation rate constants in olefin polymerization with supported ZN catalysts

Cited by 39 publications

References 0 publications

Kinetics of short‐duration ethylene–propylene copolymerization with MgCl₂‐supported Ziegler–Natta catalyst: Differentiation of active centers on the external and internal surfaces of the catalyst particles

Kinetics of short‐duration ethylene–propylene copolymerization with MgCl₂‐supported Ziegler–Natta catalyst: Differentiation of active centers on the external and internal surfaces of the catalyst particles

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

Kinetic Study of Ethylene Polymerization Over Supported Bis(imino)pyridine Iron (II) Catalysts

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Recent data on the number of active centers and propagation rate constants in olefin polymerization with supported ZN catalysts

Cited by 39 publications

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Kinetics of short‐duration ethylene–propylene copolymerization with MgCl2‐supported Ziegler–Natta catalyst: Differentiation of active centers on the external and internal surfaces of the catalyst particles

Kinetics of short‐duration ethylene–propylene copolymerization with MgCl2‐supported Ziegler–Natta catalyst: Differentiation of active centers on the external and internal surfaces of the catalyst particles

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

Kinetic Study of Ethylene Polymerization Over Supported Bis(imino)pyridine Iron (II) Catalysts

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Kinetics of short‐duration ethylene–propylene copolymerization with MgCl₂‐supported Ziegler–Natta catalyst: Differentiation of active centers on the external and internal surfaces of the catalyst particles

Kinetics of short‐duration ethylene–propylene copolymerization with MgCl₂‐supported Ziegler–Natta catalyst: Differentiation of active centers on the external and internal surfaces of the catalyst particles