On the Mechanism of Polypropene Growth over MgCl2/TiCl4 Catalyst Systems

Cecchin, G.; Marchetti, E.; Baruzzi, Giovanni

doi:10.1002/1521-3935(20010601)202:10<1987::aid-macp1987>3.0.co;2-b

Cited by 84 publications

(80 citation statements)

References 11 publications

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“…Other works subsequently contributed to the establishment of a basis of the fragmentation and growth mechanisms, including the following concepts: that there is a multigranular structure and that polymer growth takes place on the primary grains of the catalyst; that final polymer particles replicate the shape of the catalyst particles; that the polymerization rates may be reduced due to diffusion limitations; and, that the support breaks up due to the generation of mechanical stresses in the pores. [4,5] The nascent phase of these polymerizations has been widely studied, but more from the point of view of exploring the relation between the crystallization, formation of the polymer chains and the impact of monomer transport upon the polymer morphology. [6][7][8][9][10][11][12][13] In spite of the importance of studies regarding the development of polymer particle morphology, the real impact of the reaction conditions on the morphogenesis of the polymer particles has not been completely explained.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Initial Stages of Gas‐Phase Ethylene Polymerizations with a SiO₂‐Supported Ziegler–Natta Catalyst

Machado

Lima

Pinto

et al. 2009

Macro Reaction Engineering

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The very early stages of gas‐phase ethylene polymerization on an SiO2‐supported Ziegler–Natta catalyst were studied with the help of a short‐stop reactor. The short‐stop‐reactor‐based technique was useful in studying nascent polymerization, providing insights at very short, controlled times into important phenomena regarding catalyst fragmentation and the activation and deactivation of catalyst sites that take place during the very early stages of the reaction. Experimental results indicate that the growth of the polymer chains occurs at unsteady conditions during the initial stages of the polymerization. Hydrogen has a strong influence on the initial kinetics, leading to a significant decrease of polymerization activity. Polymer crystallinity increases with the reaction time, probably due to the formation of long chains with a high degree of crystallinity.magnified image

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Section: Introductionmentioning

confidence: 99%

Evaluation of the Initial Stages of Gas‐Phase Ethylene Polymerizations with a SiO₂‐Supported Ziegler–Natta Catalyst

Machado

Lima

Pinto

et al. 2009

Macro Reaction Engineering

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“…Por exemplo, verificou-se que o grão catalítico apresenta uma estrutura multipartícula (formada por grãos primários), que o crescimento polimérico se dá sobre os grãos primários do catalisador, que as partículas de polímero nascente reproduzem a forma da partícula de catalisador (fenômeno de replicação catalítica), que pode ocorrer limitação no mecanismo de difusão devida à elevada reatividade monomérica, etc. [53] . De forma simplificada, o mecanismo de fragmentação pode ser representado da maneira descrita a seguir.…”

Section: Fragmentação Do Catalisador Heterogêneounclassified

“…Neste cenário, inúmeros trabalhos teóricos e/ou experimentais foram desenvolvidos com a finalidade de entender como a morfologia da partícula polimérica é afetada pelas condições de polimerização [23,27,30,36,41,53,55,57,58,61,62,69,80,81,83, . A Tabela 1 ilustra alguns dos fenômenos, que devem ser considerados Tabela 1.…”

Section: Modelos Aplicados à Fragmentação De Catalisadores Heterogêneosunclassified

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 catalyst particle morphology characteristics (particle shape and size distribution, pore volume, pore size distribution, bulk density, and so on) greatly influence plant operation efficiency, polymerization kinetics, and final polymer morphology. [1][2][3][4] For example, a catalyst with bad morphology causes failure in polymer morphology control, which leads to serious trouble in plant operation, such as fouling or sheeting, broadening the residence time distribution in the reactor, etc. Because of these reasons, supported catalysts with superior morphology (spherical with a moderate particle size, narrow particle size distribution, and high bulk density) are always desired.…”

Section: Introductionmentioning

confidence: 99%

Initial Particle Morphology Development in Ziegler‐Natta Propylene Polymerization Tracked with Stopped‐Flow Technique

Taniike

Thang

Binh

et al. 2011

Macro Chemistry & Physics

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In this study, the particle morphology development at the very initial stage of propylene polymerization using a spherical Mg(OEt)2‐based ZN catalyst was precisely tracked by applying stopped‐flow and short‐time slurry polymerizations. Electron microscope observation and mercury porosimetry derived a comprehensive view of the initial particle morphology development. The polymer first filled macropores, which were mainly located in the middle layer of the catalyst particles, then caused the fragmentation of the middle layer, and finally triggered the fragmentation of the particle core in a stepwise manner. Thus, key effects of the layered catalyst architecture and spatial distribution of macropores were discovered on the initial morphology control of catalytic olefin polymerization. magnified image

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On the Mechanism of Polypropene Growth over MgCl2/TiCl4 Catalyst Systems

Cited by 84 publications

References 11 publications

Evaluation of the Initial Stages of Gas‐Phase Ethylene Polymerizations with a SiO₂‐Supported Ziegler–Natta Catalyst

Evaluation of the Initial Stages of Gas‐Phase Ethylene Polymerizations with a SiO₂‐Supported Ziegler–Natta Catalyst

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

Initial Particle Morphology Development in Ziegler‐Natta Propylene Polymerization Tracked with Stopped‐Flow Technique

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On the Mechanism of Polypropene Growth over MgCl2/TiCl4 Catalyst Systems

Cited by 84 publications

References 11 publications

Evaluation of the Initial Stages of Gas‐Phase Ethylene Polymerizations with a SiO2‐Supported Ziegler–Natta Catalyst

Evaluation of the Initial Stages of Gas‐Phase Ethylene Polymerizations with a SiO2‐Supported Ziegler–Natta Catalyst

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

Initial Particle Morphology Development in Ziegler‐Natta Propylene Polymerization Tracked with Stopped‐Flow Technique

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Product

Resources

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Evaluation of the Initial Stages of Gas‐Phase Ethylene Polymerizations with a SiO₂‐Supported Ziegler–Natta Catalyst

Evaluation of the Initial Stages of Gas‐Phase Ethylene Polymerizations with a SiO₂‐Supported Ziegler–Natta Catalyst