Effects of external electron donor on catalyst active sites in propylene polymerization

Lim, Sinye; Choung, Suk-Jin

doi:10.1002/(sici)1097-4628(19980307)67:10<1779::aid-app11>3.0.co;2-s

Cited by 10 publications

(3 citation statements)

References 2 publications

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“…When DDS is used as external donor, the catalyst activity all decreased. It is widely accepted that the addition of electron donor generally decreases polymerization activity because nonstereospecific sites on catalyst are selectively poisoned by external donor 11, 12…”

Section: Resultsmentioning

confidence: 99%

Molecular weight distribution of polyethylene catalyzed by Ziegler–Natta catalyst supported on MgCl₂ doped with AlCl₃

Chen

Fan

Liao³

et al. 2006

J of Applied Polymer Sci

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Ti-based Ziegler-Natta catalysts supported on MgCl 2 doped with AlCl 3 were prepared by the reaction of MgCl 2 /AlCl 3 -ethanol adduct with TiCl 4 . No AlCl 3 crystallites were found in the AlCl 3 -doped catalysts by WAXD analysis, suggesting that AlCl 3 /MgCl 2 solid solution was formed. The effect of doping on the catalyst performance in ethylene polymerization was investigated. The results showed that the catalysts based on AlCl 3 -doped MgCl 2 support exhibited a slightly higher activity than did the MgCl 2 -supported catalyst and the molecular weight distribution (MWD) of polyethylene (PE) markedly increased (from 10.8 to 47.9) with the increase of AlCl 3 content in catalysts. The changes in catalyst's active center distribution were studied based on nonlinear fitting of the polymer GPC curves by multiple Flory functions. It was found that increase of types of active centers by introducing AlCl 3 into the support should be responsible for the broadening of MWD of PE.

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Section: Resultsmentioning

confidence: 99%

Molecular weight distribution of polyethylene catalyzed by Ziegler–Natta catalyst supported on MgCl₂ doped with AlCl₃

Chen

Fan

Liao³

et al. 2006

J of Applied Polymer Sci

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“…Nas reações de propeno, em particular, a polimerização estereoespecífica requer a adição de bases de Lewis * para promover o envenenamento seletivo de sítios não-estereoespecíficos e/ ou transformação de sítios atáticos remanescentes em centros altamente isoespecíficos (resultando em aumento da isotaticidade e da cristalinidade do polímero formado). Além disso, a presença das bases de Lewis ajuda a prevenir a aglomeração do suporte do catalisador durante a etapa de síntese, favorecendo o controle posterior de morfologia e porosidade do polímero durante a polimerização [4,[9][10][11] . Sistemas catalíticos Ziegler-Natta são usualmente heterogêneos, sendo que o catalisador encontra-se usualmente disperso sobre uma fase sólida (suporte catalítico) que também contém uma base de Lewis (doador interno).…”

Section: Morfologia Das Partículas De Polímerounclassified

Uma revisão sobre polimerização de olefinas usando catalisadores Ziegler-Natta heterogêneos

Machado

Pinto

2011

Polímeros

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Resumo: A produção em larga escala de materiais poliméricos de elevado interesse industrial, provenientes da polimerização estereoespecífica de olefinas, tornou-se possível depois do advento dos catalisadores Ziegler-Natta. Classificados genericamente em seis gerações, esses catalisadores apresentam diferentes desempenhos em relação ao grau de especificidade do polímero, à atividade e ao controle de morfologia da partícula, o que propicia o desenvolvimento de resinas poliolefínicas com características e propriedades muito variadas. O objetivo principal desse trabalho é revisar e discutir algumas das questões fundamentais que estão relacionadas com as reações de polimerização de olefinas realizadas com catalisadores heterogêneos. Dá-se ênfase particular aos fatores determinantes para a condução apropriada dos processos industriais, como, por exemplo, a fragmentação controlada do catalisador, o fenômeno de replicação das características estruturais do catalisador e o controle da morfologia da partícula de polímero, a importância da prepolimerização e os efeitos relacionados à transferência de calor e massa durante a reação. Discutem-se também aspectos relacionados à modelagem dos sistemas de polimerização e às técnicas experimentais usadas para o estudo do fenômeno de fragmentação das partículas de catalisador. Palavras-chave: Polimerização de olefinas, catalisadores Ziegler-Natta, morfologia das partículas poliméricas, fragmentação catalítica, modelagem. A Survey on Olefins Polymerization Using Heterogeneous Ziegler-Natta CatalystsAbstract: Large-scale production of polymer materials of high industrial value through stereospecific polymerization of olefins became possible only after the advent of Ziegler-Natta catalysts. Usually grouped into six different generations, these catalysts present distinct activity and allow for production of polymer materials with distinct degrees of stereospecificity, morphology and end-use properties. The main objective of this work is to review and discuss some of the fundamental issues related to olefins polymerization reactions performed with heterogeneous catalysts. Particular emphasis is given to factors that affect the performances of real industrial processes, such as the catalyst fragmentation, the control of the final particle morphology and the morphological replication phenomena, the heat and mass transfer limitations during the polymerization reaction and the prepolymerization stage. Aspects related to the modeling of polymerization reactors and to the experimental study of catalyst fragmentation are also discussed. Keywords: Olefins polymerization, Ziegler-Natta catalysts, polymeric particles morphology, catalyst fragmentation, modeling. IntroduçãoO advento dos catalisadores Ziegler-Natta para polimerizar olefinas como o eteno e o propeno representou um grande marco na história dos processos químicos em geral e dos processos de polimerização em particular. A aplicação destes sistemas catalíticos aos processos de polimerização propiciou o controle de características esté...

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“…In general, during the propylene polymerization by the fourth‐generation Ziegler–Natta catalyst, external donors are necessary, which can not only improve PP isotacticity significantly, but also has an important impact on polymerization activity, the molecular weight distribution (MWD) and microstructure of polymer 5–20. There are several reports about the effect of external donor on the sequence length distribution of PP in the polymer chains.…”

Section: Introductionmentioning

confidence: 99%

The effect of the mixed external donors on the sequence length distribution of polypropylene

Chang

Ren

Dang

et al. 2012

J of Applied Polymer Sci

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The effects of different mixed external donors on the crystallization behavior and sequence length distribution of polypropylene prepared by MgCl2‐supported TiCl4 Ziegler–Natta catalyst were studied through successive self‐nucleation and annealing (SSA) technique. The SSA results show that the crystallization ability and the relative contents of long isotactic sequence length gradually increase with the increase of the relative component of Donor‐1 (cyclohexylmethyldimethoxysilane, dicyclohexyl(dimethoxy)silane, and dipiperidinedimethoxysilane) in the different mixed external donors when the ratio of the mixed external donors/Ti (Si/Ti) is unchanged. The thickness distribution of lamellar also becomes broader, indicating the sequence length distribution of polypropylene gets broader. The crystallization ability and the relative contents of long isotactic sequence length of polypropylene prepared by the mixed cyclohexylmethyldimethoxysilane and n‐propyltriethoxysilane (CN) external donors are lowest. However, the effect of the mixed dicyclohexyl(dimethoxy)silane and n‐propyltriethoxysilane (HN) and the mixed dipiperidinedimethoxysilane and n‐propyltriethoxysilane (PyN) external donors on the crystallization ability and sequence length of polypropylene are more significantly. Especially, the relative content of long isotactic sequence length increases sharply from 0.2 to 27.5% in the polypropylene chain of sample prepared by the mixed PyN external donors when the proportion of Donor 1 is running up to 90%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

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Effects of external electron donor on catalyst active sites in propylene polymerization

Cited by 10 publications

References 2 publications

Molecular weight distribution of polyethylene catalyzed by Ziegler–Natta catalyst supported on MgCl₂ doped with AlCl₃

Molecular weight distribution of polyethylene catalyzed by Ziegler–Natta catalyst supported on MgCl₂ doped with AlCl₃

Uma revisão sobre polimerização de olefinas usando catalisadores Ziegler-Natta heterogêneos

The effect of the mixed external donors on the sequence length distribution of polypropylene

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Effects of external electron donor on catalyst active sites in propylene polymerization

Cited by 10 publications

References 2 publications

Molecular weight distribution of polyethylene catalyzed by Ziegler–Natta catalyst supported on MgCl2 doped with AlCl3

Molecular weight distribution of polyethylene catalyzed by Ziegler–Natta catalyst supported on MgCl2 doped with AlCl3

Uma revisão sobre polimerização de olefinas usando catalisadores Ziegler-Natta heterogêneos

The effect of the mixed external donors on the sequence length distribution of polypropylene

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Product

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Molecular weight distribution of polyethylene catalyzed by Ziegler–Natta catalyst supported on MgCl₂ doped with AlCl₃

Molecular weight distribution of polyethylene catalyzed by Ziegler–Natta catalyst supported on MgCl₂ doped with AlCl₃