Heat Transfer and Nascent Polymerisation of Olefins on Supported Catalysts

Olalla, Béatriz; Broyer, Jean-Pierre; McKenna, Timothy F. L.

doi:10.1002/masy.200851101

Cited by 18 publications

(15 citation statements)

References 10 publications

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“…11,29,30 In these previous studies, triethylaluminium (TEA)-treated silica was used as the inert diluent. This implies that solid liquid extraction is necessary to recover the polymer for analysis.…”

Section: Inert Seedbedmentioning

confidence: 99%

“…29 Using this reactor, it was shown that it is possible to develop a relationship between how the heat transfer rate is controlled (governed mainly by gas flow rate) and the start-up kinetics of the polymerization of ethylene on a supported metallocene catalyst. It has also been used to show how a variation in the gas phase thermal conductivity can alter consistently the temperature profiles in the reactor thus giving very different values of catalyst activity.…”

Section: Introductionmentioning

confidence: 99%

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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: Inert Seedbedmentioning

confidence: 99%

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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“…40 ms) performed with a quenched-flow apparatus. More recently, Olalla et al [25] improved the original gas-phase short-stop technique [5,26] in order to study heat transfer in gas-phase olefin polymerization on supported catalyst; they found that the rate of reaction has a very strong influence on the rate of fragmentation and also showed that the shape of the rate curve is dependent on the initial conditions of the polymerization, suggesting that the mechanism of fragmentation of the catalyst carrier depends on the start-up of the polymerization. The latter observation confirmed an earlier result of Knocke et al [27] These and other articles in a similar vein all point to the fact that fragmentation influences the morphology, but that the rate of polymerization during the fragmentation step and the physical properties of the polymer present during this stage all interact in a complex manner.…”

Section: Introductionmentioning

confidence: 97%

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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“…Esta técnica permite o acompanhamento simultâneo do crescimento da partícula polimérica e da cinética de polimerização em polimerizações em fase gasosa. Pater et al [82,83] descreveram um Recentemente, Ollala et al [110] e Tioni et al [111] usaram o SSR [105] para estudar o mecanismo de transferência de calor em polimerizações de eteno em fase gasosa, conduzidas com catalisadores heterogêneos. De acordo com os autores, a taxa de polimerização exerce um forte efeito sobre a fragmentação, apresentando forte dependência com as condições iniciais da polimerização.…”

Section: Técnicas Experimentais Para Avaliação Da Fragmentação Catalíunclassified

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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Heat Transfer and Nascent Polymerisation of Olefins on Supported Catalysts

Cited by 18 publications

References 10 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

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

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Heat Transfer and Nascent Polymerisation of Olefins on Supported Catalysts

Cited by 18 publications

References 10 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

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

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