Modeling of morphogenesis of growing polyolefin particles

Grof, Zdeněk; Košek, Juraj; Marek, M.

doi:10.1002/aic.10549

Cited by 65 publications

(74 citation statements)

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“…The tendency of the catalyst particles to form the onion-ring-like structure decreased with increasing catalyst F. The results of this study provide an additional experimental perspective to ongoing modeling efforts in particle fragmentation during olefin polymerization over heterogeneous catalysts. 34,35,46 …”

Section: Discussionmentioning

confidence: 98%

“…32 The lower activity at high 1-hexene concentrations could also have been due to the softening of the high 1-hexene content copolymer at the prevailing polymerization temperature; this would have rendered it less effective in fracturing the catalyst particle. 31,[33][34][35] The synergistic effect of a-olefins during ethylene polymerization is widely observed with conventional Ziegler-Natta and metallocene catalysts, 16,36,37 and both physical and chemical effects have been used to explain the phenomenon. Wester and Ystenes 15 observed a significant increase in ethylene polymerization activity over coarsely grained catalyst on propylene addition, but no activity enhancement was observed with the finely grained catalyst, which suggests that physical changes in the catalyst were (at least partly) responsible for the activity enhancement.…”

Section: Moderate a H Values [10-20 T Of Pe (Mol Ofmentioning

confidence: 99%

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Influence of support friability and concentration of α‐olefins on gas‐phase ethylene polymerization over polymer‐supported metallocene/methylaluminoxane catalysts

Hammawa

Wanke

2007

J of Applied Polymer Sci

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The effects of support friability (F) and ethylene/comonomer ratios were investigated over supported metallocene/methylaluminoxane catalysts prepared with nine different porous polymeric supports and various comonomer concentrations with a 2-L reactor operated in the semibatch gas-phase mode at 808C and 1.4 MPa. F of the supports was measured with a newly devised method. The performance of the supported catalysts depended on support F as follows. The average homopolymerization activities varied from less than 6 t of polyethylene (PE) (mol of Zr)À1 h À1 for low-F catalysts to 10-20 t of PE (mol of Zr)À1 h À1 for moderate-F catalysts and up to 100 t of PE (mol of Zr) À1 h À1 for the high-F catalysts. The presence of 1-hexene and propylene comonomers increased the activity of the low-F catalysts by up to 20-fold and 50-fold, respectively; that is, there were very marked comonomer effects. Activity enhancement by 1-hexene was less than 3-fold for the moderate-F catalysts, whereas the high-F catalysts showed little activity enhancement. Sometimes, 1-hexene even resulted in activity reductions. Very different particle morphologies were obtained with the catalysts of different F's.

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Section: Discussionmentioning

confidence: 98%

Section: Moderate a H Values [10-20 T Of Pe (Mol Ofmentioning

confidence: 99%

Influence of support friability and concentration of α‐olefins on gas‐phase ethylene polymerization over polymer‐supported metallocene/methylaluminoxane catalysts

Hammawa

Wanke

2007

J of Applied Polymer Sci

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“…Recentemente, Grof et al [141,142] propuseram uma nova abordagem para modelagem da morfologia de partículas poliméricas em crescimento (Figura 6). De acordo com os autores, a partícula polimérica pode ser descrita como um elevado número de microelementos que apresentam interações (binárias e ternárias) viscoelásticas.…”

Section: Modelos Morfológicos Estenoz E Chiovettaunclassified

“…Segundo Grof et al [141,142] o modelo proposto é capaz de predizer o surgimento de boa parte das morfologias de partículas poliméricas obtidas de catalisadores heterogêneos empregados em polimerizações industriais, como por exemplo a existência de macrocavidades, de partículas ocas, a formação de finos, a existência de problemas de replicação da partícula de catalisador, etc. Apesar de promissora, a abordagem proposta por Grof et al [141,142] pode não ser realista o suficiente para descrever os instantes iniciais da polimerização de olefinas, principalmente porque o modelo considera que a partícula catalítica pode ser representada por um aglomerado de micro elementos já fragmentadas desde o início da polimerização.…”

Section: Modelos Morfológicos Estenoz E Chiovettaunclassified

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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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Product Morphology in Olefin Polymerization with Polymer Supported Metallocene Catalysts

Wanke

2010

Handbook of Transition Metal Polymerization Catalysts

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Modeling of morphogenesis of growing polyolefin particles

Cited by 65 publications

References 44 publications

Influence of support friability and concentration of α‐olefins on gas‐phase ethylene polymerization over polymer‐supported metallocene/methylaluminoxane catalysts

Influence of support friability and concentration of α‐olefins on gas‐phase ethylene polymerization over polymer‐supported metallocene/methylaluminoxane catalysts

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

Product Morphology in Olefin Polymerization with Polymer Supported Metallocene Catalysts

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