Polymerization mechanism forin situ supported metallocene catalysts

Chu, Kyung-Jun; Soares, João B. P.; Penlidis, Alexander

doi:10.1002/(sici)1099-0518(20000201)38:3<462::aid-pola10>3.0.co;2-o

Cited by 69 publications

(66 citation statements)

References 10 publications

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“…[25] The authors reported that the polyethylene particles replicated the support morphology and suggested a mechanism where active sites were located on the silica surface (internal and external). Fink and coworkers showed an unusual ethylene polymerization using metallocene/ SMAO systems, which had triisobutylaluminium present in solution.…”

Section: Meso-scale Polymerization Mechanismmentioning

confidence: 99%

“…The approach to support the catalyst in situ was shown recently using several metallocene catalysts. [25] It comprises contacting catalyst and methylaluminoxane (MAO)-treated support directly inside the polymerization reactor, without any prior manipulation of catalyst components. The result is a supported catalyst with high productivity, and a polymer product with controlled morphology and high bulk density.…”

Section: Introductionmentioning

confidence: 99%

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Polyethylene Made with In Situ Supported Ni-Diimine/SMAO: Replication Phenomenon and Effect of Polymerization Conditions on Polymer Microstructure and Morphology

Simon

Patel

Soares³

et al. 2001

Macromol. Chem. Phys.

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The catalyst prepared by supporting in situ 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediiminenickel(II) dichloride (1) on silica–methylaluminoxane (SMAO) has high activity for ethylene polymerization, although it is less active than the unsupported system 1/MAO. No external alkylaluminum cocatalyst needs to be added to the in situ supported system. Short chain branches are produced without addition of α‐olefin comonomer, due to the chain‐walking mechanism. Ethylene pressure and polymerization temperature affect the degree of short chain branch formation. At constant ethylene pressure, when the polymerization temperature rises, the short chain branch content also increases. For a given ethylene pressure, there is a threshold polymerization temperature above which polymer particle agglomeration starts to occur. For the conditions investigated herein, from 30 to 50°C the morphology of the polymer particles replicates that of the support. At 55°C, polyethylene starts to become soluble in the reaction medium, and therefore morphological control is gradually lost. Above 70°C, only soluble polymer is produced. Similar results are observed by keeping the temperature constant and changing the ethylene pressure.

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Section: Meso-scale Polymerization Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polyethylene Made with In Situ Supported Ni-Diimine/SMAO: Replication Phenomenon and Effect of Polymerization Conditions on Polymer Microstructure and Morphology

Simon

Patel

Soares³

et al. 2001

Macromol. Chem. Phys.

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“…Presented as a support, silica provides the heterogeneous system with great advantages over the homogeneous system such as, giving the obtained polymer with good morphology and decreasing reactor fouling in the system [3]. Nevertheless, there was a crucial disadvantage in heterogeneous copolymerization that is, supporting material, often declining the catalytic activity of the system.…”

Section: Introductionmentioning

confidence: 99%

A Comparative Study of in situ and ex situ Impregnation for LLDPE/Silica Composites Production

Chaichana¹,

Shiono²,

Praserthdam³

et al. 2012

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Abstract. The two different kinds of impregnation (in situ and ex situ) were used in the heterogeneous copolymerization of ethylene and 1-hexene for production of LLDPE/silica composite. For the ex situ impregnation, MMAO cocatalyst was immobilized firmly onto the silica support through washing and drying step before introducing the powder of MMAO/silica support into the copolymerization system. For the in situ impregnation, MMAO was only contacted with silica support for the short period of time before bringing all of the slurry of MMAO/silica support into the copolymerization system. By comparing the catalytic activity between two methods, it was found that the in situ impregnation provided the higher one beneficial from the lower interaction between MMAO and silica due to lower contacting time. The lower interaction enhanced the reactivity of MMAO toward zirconocene catalyst during activation process thus leading to the higher catalytic activity. The said interaction can be proven by thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) analysis. In addition, the obtained polymers were further characterized by means of scanning electron microscopy (SEM), 13 C-NMR spectroscopy (NMR) and differential scanning calorimetry (DSC).

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“…[1][2][3][4][5] Recently, it has been demonstrated that the increased polymerization activity can be attributed to a significant lowering of the monomer diffusion barrier in ethylene homopolymerization. 6 The aforementioned studies were based on the use of MgCl 2 -supported Ziegler-Natta catalysts.…”

Section: Introductionmentioning

confidence: 99%

Effects of propylene prepolymerization on ethylene/1‐hexene and ethylene/1‐octene copolymerization with an immobilized metallocene catalyst

Smit¹,

Zheng²,

Loos³

et al. 2006

J. Polym. Sci. A Polym. Chem.

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An investigation of the effects of a propylene prepolymerization on ethylene/1‐hexene and 1‐octene copolymerization with a silica‐supported zirconocene catalyst revealed that the prepolymerization not only resulted in an increase in the catalyst activity but also gave copolymers with narrower chemical composition distributions. The positive effects of the prepolymerization were ascribed to a more complete fragmentation of the support particle, as illustrated by the uniform cross section of a polyethylene particle prepared with prepolymerization.

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Polymerization mechanism forin situ supported metallocene catalysts

Cited by 69 publications

References 10 publications

Polyethylene Made with In Situ Supported Ni-Diimine/SMAO: Replication Phenomenon and Effect of Polymerization Conditions on Polymer Microstructure and Morphology

Polyethylene Made with In Situ Supported Ni-Diimine/SMAO: Replication Phenomenon and Effect of Polymerization Conditions on Polymer Microstructure and Morphology

A Comparative Study of in situ and ex situ Impregnation for LLDPE/Silica Composites Production

Effects of propylene prepolymerization on ethylene/1‐hexene and ethylene/1‐octene copolymerization with an immobilized metallocene catalyst

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