Stopped-Flow Techniques in Ziegler Catalysis

Liu, Boping; Matsuoka, Hitoshi; Terano, Minoru

doi:10.1002/1521-3927(20010101)22:1<1::aid-marc1>3.0.co;2-t

Cited by 100 publications

(77 citation statements)

References 15 publications

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“…Both of these lead to the improvement of polymerization activity and the isotacticity of the polymer. In our previous study [5] on stopped-flow polymerization, the multiple active sites were treated uniformly and linear increase of polymerization activity and M n of polymer with polymerization time was obtained, indicating a quasi-living polymerization characteristic. The C* and k p of active site were constant within the short polymerization time.…”

Section: Resultsmentioning

confidence: 99%

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Effects of Electron Donors on Active Sites Distribution of MgCl₂‐Supported Ziegler‐Natta Catalysts Investigated by Multiple Active Sites Model

Wang

Murayama

Liu

et al. 2005

Macro Chemistry & Physics

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Summary: The stopped‐flow polymerization of propylene catalyzed by a Ziegler‐Natta catalyst in the presence of internal and external electron donors was carried out. The influence of the electron donors on the active sites of the catalyst was investigated using a multiple active site model. The variation of each group of active sites, such as the concentration and kp of each site at various polymerization times, can be obtained from this model. It was found that an electron donor mainly affects the aspecific active site by reducing its concentration and increasing its kp. The isospecific site is only slightly altered in terms of concentration and its kp because of steric hindrance.Variation of [C*] of each active site of TiCl4/MgCl2‐AlEt3 at various polymerization times.imageVariation of [C*] of each active site of TiCl4/MgCl2‐AlEt3 at various polymerization times.

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Section: Resultsmentioning

confidence: 99%

“…[2][3][4] For simplification, previous researchers treated active sites uniformly, [5] in other words, different types of active sites with different stereospecificity and kinetic parameters were mathematically considered to be the same. In fact, several groups of active sites are formed at the early stage of polymerization.…”

Section: Introductionmentioning

confidence: 99%

Effects of Electron Donors on Active Sites Distribution of MgCl₂‐Supported Ziegler‐Natta Catalysts Investigated by Multiple Active Sites Model

Wang

Murayama

Liu

et al. 2005

Macro Chemistry & Physics

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“…O método Stopped-Flow ¶ (SFM) [92] , comumente usado em estudos de cinética homogênea e para análises de polimerizações em solução e em suspensão [93][94][95] , também é extensamente empregado para estudo do desenvolvimento morfológico de partículas poliméricas em polimerizações conduzidas com catalisadores heterogêneos em experimentos realizados com tempos de polimerização extremamente curtos em condições industriais de operação [96][97][98][99][100][101][102][103][104] . Seguindo o conceito similar ao SFM, Machado et al [105] desenvolveram um novo aparato experimental (denominado de Short Stop Reactor ** -SSR) especialmente para o estudo da polimerização nascente e a fragmentação de catalisadores heterogêneos em polimerizações de olefinas conduzidas em fase gasosa.…”

Section: A Etapa De Prepolimerizaçãounclassified

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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“…The stopped-flow polymerization of propylene and the determination of the kinetic parameters were carried out in accordance with the method reported previously [6,8,[12][13][14][15]. The propylene polymerization was typically performed with a catalyst (ca.…”

Section: Stopped-flow Polymerizationmentioning

confidence: 99%

“…Recently, the stopped-flow technique has been demonstrated to be one of the most powerful methods for studying the kinetic and stereospecific natures of the active sites on the heterogeneous Ziegler-Natta catalysts used for propylene polymerization [8]. The polymerization reaction proceeds within an extremely short period (ca.…”

Section: Introductionmentioning

confidence: 99%

Effects of various poisoning compounds on the activity and stereospecificity of heterogeneous Ziegler–Natta catalyst

Tangjituabun

Kim

Hiraoka³

et al. 2008

Science and Technology of Advanced Materials

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A TiCl 4 /ethylbenzoate/MgCl 2 Ziegler-Natta catalyst was pretreated with chemically different poisoning compounds to investigate their effects on the catalyst activity and stereospecificity for propylene polymerization. The poisoning power on the activity was in the order of methanol > acetone > ethyl acetate. A kinetic analysis using the stopped-flow method revealed that addition of the poisoning materials decreased the activity through the reduction of the number of active sites, whereas the catalyst isospecificity was hardly affected by these materials.

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Stopped-Flow Techniques in Ziegler Catalysis

Cited by 100 publications

References 15 publications

Effects of Electron Donors on Active Sites Distribution of MgCl₂‐Supported Ziegler‐Natta Catalysts Investigated by Multiple Active Sites Model

Effects of Electron Donors on Active Sites Distribution of MgCl₂‐Supported Ziegler‐Natta Catalysts Investigated by Multiple Active Sites Model

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

Effects of various poisoning compounds on the activity and stereospecificity of heterogeneous Ziegler–Natta catalyst

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Stopped-Flow Techniques in Ziegler Catalysis

Cited by 100 publications

References 15 publications

Effects of Electron Donors on Active Sites Distribution of MgCl2‐Supported Ziegler‐Natta Catalysts Investigated by Multiple Active Sites Model

Effects of Electron Donors on Active Sites Distribution of MgCl2‐Supported Ziegler‐Natta Catalysts Investigated by Multiple Active Sites Model

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

Effects of various poisoning compounds on the activity and stereospecificity of heterogeneous Ziegler–Natta catalyst

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Effects of Electron Donors on Active Sites Distribution of MgCl₂‐Supported Ziegler‐Natta Catalysts Investigated by Multiple Active Sites Model

Effects of Electron Donors on Active Sites Distribution of MgCl₂‐Supported Ziegler‐Natta Catalysts Investigated by Multiple Active Sites Model