Diffusion Interface Technique for Determination of Initial Polymerization Kinetics

Skoumal, Miroslav; Cejpek, Igor; Chêng, Chu-yüan

doi:10.1002/marc.200400565

Cited by 5 publications

(4 citation statements)

References 9 publications

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“…Skoumal et al employed oil to separate catalytic system from the monomer‐saturated heptane solution, and demonstrated the high mass transfer resistance of monomer in oil. [ 52 ] Thus there are reasons to believe that the lower activity of gas phase prepolymerization we obtained in the presence of oil is attributed to the mass transfer resistance imposed by the mineral oil covering on the surface of the catalyst particle. As an additional argument, the activity in the main stage polymerization (see Figure 15 and the following text) was higher for the entry with extra oil compared to the entry without extra oil, in accordance with the active sites number reported here.…”

Section: Resultsmentioning

confidence: 99%

An Experimental Investigation of the Impact of Gas Phase Prepolymerization of Propylene

McKenna

2020

Macro Reaction Engineering

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A systematic investigation is carried out on the gas phase of propylene during the initial instants of polymerization. The results confirm the positive impact of small amounts of mineral oil on the initial reaction rate and morphology. It is shown that polymerizing under conditions of mild temperature and pressure alone are not enough to achieve the same result. It is found that the presence of mineral oil, and low temperature of polymerization can be used to control the morphology of polymer particles and to obtain high activity in the main reaction. If enough oil is used, moderate to high temperatures of prepolymerization are acceptable in terms of controlling morphology but can compromise the activity of the main polymerization. It is also observed that the way in which the oil is introduced has an impact on the kinetics and particle morphology. Separate addition of oil from the precatalyst gives rise to relatively flat kinetics during prepolymerization and highest rate during main polymerization. To account for the activity enhancement, a selective quench‐labeling study employing methyl propargyl ether shows that the presence of mineral oil appears to increase the fraction of active titanium by a factor of almost 2.

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Section: Resultsmentioning

confidence: 99%

An Experimental Investigation of the Impact of Gas Phase Prepolymerization of Propylene

McKenna

2020

Macro Reaction Engineering

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“…found that in propylene polymerization with a preactivated supported ZN catalyst, the initiation was completed within a few seconds. Skoumal et al . also observed a quick initiation in propylene polymerization.…”

Section: Introductionmentioning

confidence: 88%

“…Among these problems, the formation or initiation of catalytic centers in the first few minutes of olefin polymerization is especially important, as it will profoundly influence the kinetics, particle morphology, and polymer chain structure of the whole polymerization process. Many researchers have reported the kinetics and particle morphology of ZN‐catalyzed olefin polymerization in the initial stage . In a recent work, Busico et al .…”

Section: Introductionmentioning

confidence: 99%

Kinetics of short‐duration ethylene polymerization with MgCl₂‐supported Ziegler–Natta catalyst: Two‐stage initiation evidenced by changes in active center concentration

Khan

Guo

et al. 2017

J of Applied Polymer Sci

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The kinetics of ethylene polymerization with a TiCl 4 /MgCl 2 -type Ziegler-Natta catalyst was studied. Changes in polymerization activity and concentration of active centers ([C*]) in the first 5 min were determined. Initiation of the active centers was found to proceed in two stages. In the first stage, [C*]/[Ti] quickly rose to about 1% in less than 30 s and then remained stable in the subsequent 60 s. Then the [C*]/[Ti] value started to increase again, forming the second buildup stage. The polymerization activity was found to change roughly in parallel with the change in [C*]/ [Ti]. Changes in the polymer/catalyst particle morphology and polymer molecular weight distribution with polymerization time were studied. A mechanistic model was proposed to explain the two-stage kinetics: initiation of active sites on the outer surface of catalyst particles takes place in the first stage, and initiation of active sites buried inside the particles takes place in the second stage. These buried sites are released when the catalyst particles are fragmented by the expanding polymer phase.

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“…Despite extensive fundamental studies in this field over the past decades, there are still many unsolved problems concerning the polymerization mechanism and relationships between catalyst structure and polymerization behaviors. The kinetics and mechanism of ethylene and propylene polymerizations with Z–N catalysts have been studied in a broad span of reaction durations ranging from less than 1 s to more than one hour [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. When ethylene and propylene polymerizations with the same catalyst are compared, several peculiarities in the reaction kinetics have been reported.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study on Kinetics of Ethylene and Propylene Polymerizations with Supported Ziegler–Natta Catalyst: Catalyst Fragmentation Promoted by Polymer Crystalline Lamellae

Zhang

Jiang

et al. 2019

Polymers

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The kinetic behaviors of ethylene and propylene polymerizations with the same MgCl2-supported Ziegler–Natta (Z–N) catalyst containing an internal electron donor were compared. Changes of polymerization activity and active center concentration ([C*]) with time in the first 10 min were determined. Activity of ethylene polymerization was only 25% of that of propylene, and the polymerization rate (Rp) quickly decayed with time (tp) in the former system, in contrast to stable Rp in the latter. The ethylene system showed a very low [C*]/[Ti] ratio (<0.6%), in contrast to a much higher [C*]/[Ti] ratio (1.5%–4.9%) in propylene polymerization. The two systems showed noticeably different morphologies of the nascent polymer/catalyst particles, with the PP/catalyst particles being more compact and homogeneous than the PE/catalyst particles. The different kinetic behaviors of the two systems were explained by faster and more sufficient catalyst fragmentation in propylene polymerization than the ethylene system. The smaller lamellar thickness (<20 nm) in nascent polypropylene compared with the size of nanopores (15–25 nm) in the catalyst was considered the key factor for efficient catalyst fragmentation in propylene polymerization, as the PP lamellae may grow inside the nanopores and break up the catalyst particles.

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Diffusion Interface Technique for Determination of Initial Polymerization Kinetics

Cited by 5 publications

References 9 publications

An Experimental Investigation of the Impact of Gas Phase Prepolymerization of Propylene

An Experimental Investigation of the Impact of Gas Phase Prepolymerization of Propylene

Kinetics of short‐duration ethylene polymerization with MgCl₂‐supported Ziegler–Natta catalyst: Two‐stage initiation evidenced by changes in active center concentration

Comparative Study on Kinetics of Ethylene and Propylene Polymerizations with Supported Ziegler–Natta Catalyst: Catalyst Fragmentation Promoted by Polymer Crystalline Lamellae

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Diffusion Interface Technique for Determination of Initial Polymerization Kinetics

Cited by 5 publications

References 9 publications

An Experimental Investigation of the Impact of Gas Phase Prepolymerization of Propylene

An Experimental Investigation of the Impact of Gas Phase Prepolymerization of Propylene

Kinetics of short‐duration ethylene polymerization with MgCl2‐supported Ziegler–Natta catalyst: Two‐stage initiation evidenced by changes in active center concentration

Comparative Study on Kinetics of Ethylene and Propylene Polymerizations with Supported Ziegler–Natta Catalyst: Catalyst Fragmentation Promoted by Polymer Crystalline Lamellae

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Kinetics of short‐duration ethylene polymerization with MgCl₂‐supported Ziegler–Natta catalyst: Two‐stage initiation evidenced by changes in active center concentration