The particle as microreactor: catalytic propylene polymerizations with supported metallocenes and Ziegler–Natta catalysts

Weickert, G.; Meier, G. B.; Pater, J.T.M.; Westerterp, K.R.

doi:10.1016/s0009-2509(98)00441-2

Cited by 64 publications

(60 citation statements)

References 6 publications

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“…14 In general, catalyst fragmentation depends mainly on two factors: hydraulic pressure generated by the formed polymer inside the catalyst pores and the rigidity of the support material. 15 The support must have a mechanical strength great enough to withstand handling and low enough to break down during polymerization. 16 Several published articles have explained the fragmentation of different catalyst systems.…”

Section: Introductionmentioning

confidence: 99%

Study of the morphology and kinetics of novel Ziegler–Natta catalysts for propylene polymerization

Abboud

Denifl

Reichert

2005

J of Applied Polymer Sci

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ABSTRACT:The morphological and kinetic characteristics of novel Ziegler-Natta catalysts were studied. Catalysts were prepared by Borealis Polymers Oy using a new synthesis technique (emulsion technology). Video microscopy was used to study the growth of single catalyst particles during polymerization in the gas and liquid phases. The distribution of single particle activity was very narrow in the catalyst without external support and was rather broad in the the silica-supported catalyst. Video microscopy of molten polymer particles allowed observation of the process and degree of fragmentation of the catalyst particles. A correlation between the activation period during the initial stage of polymerization and catalyst fragmentation was found. Fragmentation was faster and more uniform with the catalyst without external support than with the silica-supported catalyst. Scanning electron microscopy provided information on morphology evolution and shape replication of the catalyst particles. With the catalyst without external support, good shape replication was observed, and compact and spherical particles were formed. With the silica-supported catalyst, shape replication was poor, and nonspherical porous polymer particle were formed. Modeling of the kinetics of propylene polymerization was done using a simple threestep reaction scheme neglecting mass and heat transport effects.

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Section: Introductionmentioning

confidence: 99%

Study of the morphology and kinetics of novel Ziegler–Natta catalysts for propylene polymerization

Abboud

Denifl

Reichert

2005

J of Applied Polymer Sci

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“…Magnesium chloride with typically 10% TiCl 3 initially forms the continuous phase, but is distributed within the polymer after reaching yields higher than 1 g polymer / g catalyst, which can be the case < 1 second under "industrial" conditions. For the characterization of the single particle behaviour, see [24][25][26][27][28].…”

Section: The Scientific Prospective On Slurry and Gas Phasementioning

confidence: 99%

“…Weickert et al, in 1999 [25] investigated the influence of the concentration of inert materials on the rate of polymerization for the first time. They found that when the concentration of inert material was increased, the reaction rate decreased.…”

Section: Nitrogen Influencementioning

confidence: 99%

Comparison of catalytic ethylene polymerization in slurry and gas phase

Daftari‐Besheli¹

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“…46 Na realidade, a fragmentação deve ocorrer pela combinação desses dois mecanismos e, dependente da massa (ou volume) de polímero formado em determinada região do catalisador. 47 A Figura 2 ilustra os dois mecanismos de fragmentação.…”

Section: Materias Empregados Como Suportesunclassified

“…Muitos trabalhos têm empregado a difusão como único mecanismo de transporte envolvido na polimerização. 48 Entretanto, Weickert et al 47 apontaram que apenas a difusão não pode explicar os resultados experimentais, principalmente para catalisadores de alta atividade, e que o mecanismo principal de transporte para o interior da partícula deveria ser a advecção (convecção), devido à existência de um gradiente de pressão dentro da mesma (nos poros) e o meio reacional externo. Esse gradiente, que garantiria o transporte advectivo, seria criado pelo rápido consumo de monômero pelos sítios ativos.…”

Section: Figura 2 Ilustração Dos Possíveis Mecanismos De Fragmentaçãounclassified

Catalisadores metalocênicos suportados para a produção de poliolefinas: revisão das estratégias de imobilização

Fisch¹,

Cardozo²,

Secchi³

et al. 2011

Quím. Nova

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Recebido em 19/4/10; aceito em 13/11/10; publicado na web em 18/2/11 SUPPORTED METALLOCENE CATALYSTS FOR POLYOLEFIN PRODUCTION: REVIEW OF THE IMMOBILIZATION STRATEGIES. The inadequacy of strategies used for the heterogeneization of metallocene catalysts is pointed out as one of the main causes of the lack of industrial employability of such polymerization catalysts. The main problems are the necessity of large quantity of MAO (cocatalyst) and the inability to control molecular mass distribution of the polymers. Based on this background, the main strategies for the heterogeneization of metallocenes are here reviewed. The advantages and disadvantages of each strategy are presented and discussed on theoretical and practical perspective. Considering the results reported on the different researches, outcomes of heterogeneization strategies are pointed out.Keywords: supported metallocene; polymerization; heterogeneous catalysis. INTRODUÇÃOCatalisadores para a produção de poliolefinas têm sido continuamente estudados desde o advento dos catalisadores Ziegler-Natta. Ao longo desses esforços, diferentes tipos de complexos foram investigados, dentre eles os metalocenos. Pertencente a essa classe, o titanoceno (Cp 2 TiCl 2 ) foi estudado por volta de 1950 na polimerização de olefinas utilizando-se um alquil alumínio para sua ativação. Nesses estudos, a atividade catalítica encontrada não foi suficientemente alta (>100 g pol g cat -1 h -1 ) para justificar maiores investimentos em pesquisas relacionadas a esses complexos. A aplicação industrial desses catalisadores tornou-se possível somente após as pesquisas de Sinn e Kaminsky 1 no final da década de 70, com a descoberta do papel cocatalítico do metilaluminoxano (MAO), gerado a partir da hidrólise parcial do trimetil alumínio (TMA). O sistema resultante metaloceno/MAO mostrou-se dotado de elevada atividade catalítica, até então não atingível com alquil alumínios comuns no papel de cocatalisadores. A partir desse momento, teve então início uma intensa atividade de pesquisa industrial e acadêmica buscando solucionar outros problemas relacionados à adaptação dos metalocenos às plantas industriais de polimerização já existentes, que operam com catalisadores Ziegler-Natta heterogêneos, em sua grande maioria. Aliado a isso, pesquisas voltaram-se ao desenvolvimento de novos complexos organometálicos, metalocênicos e não metalocêni-cos (os denominados pós-metalocenos), passíveis de produzir novos materiais poliméricos. [2][3][4][5][6][7] A Figura 1 ilustra o desenvolvimento das pesquisas para os catalisadores Ziegler-Natta, metalocenos e não metalocenos em termos do número anual de publicações. A Figura 1a mostra claramente o crescimento gradual das pesquisas envolvendo catalisadores Ziegler-Natta a partir do início da década de 60, atingindo um patamar nos meados da década de 80 e mantendo-se relativamente constante desde então. A Figura 1b evidencia o crescimento exponencial das pesquisas com foco nos complexos metalocênicos após a descoberta do MAO como cocatalisador, no final ...

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The particle as microreactor: catalytic propylene polymerizations with supported metallocenes and Ziegler–Natta catalysts

Cited by 64 publications

References 6 publications

Study of the morphology and kinetics of novel Ziegler–Natta catalysts for propylene polymerization

Study of the morphology and kinetics of novel Ziegler–Natta catalysts for propylene polymerization

Comparison of catalytic ethylene polymerization in slurry and gas phase

Catalisadores metalocênicos suportados para a produção de poliolefinas: revisão das estratégias de imobilização

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