Particle Growth During the Polymerisation of Olefins on Supported Catalysts, 1 – Nascent Polymer Structures

McKenna, Timothy F. L.; Martino, Audrey Di; Weickert, G.; Soares, João B. P.

doi:10.1002/mren.200900025

Cited by 119 publications

(132 citation statements)

References 77 publications

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“…For a more in-depth discussion of the process of catalyst fragmentation and growth, the reader is referred to earlier works from our group as well as the references therein. 2,3 It is well known that the morphology of growing polymer particles as well as the properties of nascent polymer evolve very quickly during the early instants of a polymerization. [4][5][6][7][8][9][10][11] This phase of the reaction can be crucial in ensuring adequate polymer properties, obtaining or maintaining stable reactor operation, preventing fines generation, and avoiding temperature excursions and catalyst deactivation.…”

Section: Introductionmentioning

confidence: 99%

Packed‐bed reactor for short time gas phase olefin polymerization: Heat transfer study and reactor optimization

et al. 2011

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A specially conceived packed-bed stopped flow minireactor (3 mL) suitable for short gas phase catalytic reactions has been used to study the start-up of ethylene homopolymerization with a supported metallocene catalyst. Focus has been put on the heat transfer characteristics of the supported catalysts and on understanding the relationship between the initial rate and the relative gas/particle velocities and the influence of particle parameters in the packed bed. We performed a comprehensive study on the influence of various physical parameters on the heat transfer regime at start up conditions. The catalyst activity as well as the polymer morphology is shown to be dependent on heat transfer regime. The knowledge thus obtained is applicable to industrial problems like catalyst injection in fluidized beds and helps preventing experimental artifacts due to overheating in following studies.

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Section: Introductionmentioning

confidence: 99%

Packed‐bed reactor for short time gas phase olefin polymerization: Heat transfer study and reactor optimization

et al. 2011

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“…Sabe-se que na polimerização de olefinas o polímero formado é uma réplica morfológica quase perfeita do catalisador ZieglerNatta heterogêneo empregado na reação [1,21,23] . Portanto, o controle morfológico das partículas de polímero pode ser efetuado através do controle de morfologia (por exemplo, tamanho, forma, densidade, textura e porosidade) do catalisador.…”

Section: Morfologia Das Partículas De Polímerounclassified

“…A elevada atividade dos catalisadores Ziegler-Natta traz como benefício imediato a redução significativa dos resíduos de catalisador, minimizando problemas de toxicidade, corrosão e envelhecimento precoce das peças finais, além de também permitir a redução de investimentos e custos de operação do processo [20,21] . De acordo com Galli [11] , o desenvolvimento dos catalisadores heterogêneos ‡ (principalmente aqueles suportados em MgCl 2 ) reduziu quase a zero algumas das restrições usuais de processo, como a separação e recuperação de material atático e a remoção de resíduos metálicos do catalisador.…”

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 addition, it is shown experimentally that the polydispersity of polymer at the initial moments of the polymerization is very high, suggesting the existence of significant concentration or temperature gradients. Although at very low degree of polymerization, multigrain structure is detected in SEM and TEM photographs of a nascent polymer [1,26,27], but micrograins merge into larger structures and form agglomerations when the reaction advances. These agglomerates would contain several fragments and could make larger structures in fully grown particles [28].…”

Section: Introductionmentioning

confidence: 97%

Effect of fragment size distribution on reaction rate and molecular weight distribution in heterogeneous olefin polymerization

2015

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Particle Growth During the Polymerisation of Olefins on Supported Catalysts, 1 – Nascent Polymer Structures

Cited by 119 publications

References 77 publications

Packed‐bed reactor for short time gas phase olefin polymerization: Heat transfer study and reactor optimization

Packed‐bed reactor for short time gas phase olefin polymerization: Heat transfer study and reactor optimization

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

Effect of fragment size distribution on reaction rate and molecular weight distribution in heterogeneous olefin polymerization

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