Binary metallocene supported catalyst for propylene polymerization

Marques, Maria de Fátima Vieira; Pombo, Carla C; Silva, Rodrigo A; Conte, Anunciata

doi:10.1016/s0014-3057(02)00269-0

Cited by 20 publications

(10 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…By applying this arithmetic calculation to the nine physical mixtures carried out, it can be concluded that the variation between calculated and experimental catalytic activity is 14.5 % on average. Nevertheless, this correlation does not hold for hybrid catalysts, because when hybrid catalysts are employed, the participation of each active center is random [12][13][14][15][16], so catalytic activity may change depending on the homogeneity in the hybrid catalyst when both metallocenes are anchored on the silica support. Thus, in this case the activities are considerably Kg PP/mol Zr·h·bar, which is closer to 2100 achieved by the hybrid catalyst.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, in this case the activities are considerably Kg PP/mol Zr·h·bar, which is closer to 2100 achieved by the hybrid catalyst. In comparison with individual catalysts, hybrid catalysts present a decrease of activity due to the interaction between both active catalytic centers [12][13][14][15][16].…”

Section: Resultsmentioning

confidence: 99%

“…However, this method involves additional processes and increases costs considerably [9], and 3) Combination of a binary or multicomponent catalytic system in a single reactor with the subsequent cost saving. This last method can comprise a combination of a heterogeneous Ziegler-Natta catalyst and a homogeneous metallocene catalyst providing a means to control the MWD and polydispersity of the polyolefin [10] but a disadvantage of this particular binary system comes from triethyl-aluminium (TEA) used to activate Ziegler-Natta since it has a serious detrimental effect on metallocene active sites [11] Therefore, an economical and attractive route is to use two or more metallocenes simultaneously yielding a polypropylene mixture consisting on the polymer fractions produced by each metallocene [12][13][14][15][16]. In this sense, it is important to decide which metalocenes will be present in the catalytic system, since they should have different kinetic responses, such as different propagation and termination rate constants, in order to produce a blend of polymeric chains with different predominant molecular weights.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Bimodal polypropylene through binary metallocene catalytic systems: comparison between hybrid and mixed heterogeneous catalysts

et al. 2016

View full text Add to dashboard Cite

Polypropylene with wider or bimodal molecular weight distribution is required for numerous applications since low molecular weight chains improve processability and high molecular weight fraction is required to get good mechanical properties. There are several routes to achieve a bimodal resin but the use of a binary catalytic system seems to be the most attractive, particularly with metallocenes combination. From a previous work two metallocenes were selected because they lead to polypropylenes with average molecular weights that differ in one order of magnitude. Two types of binary systems have been investigated, hybrid catalysts (two metallocenes loaded on the same support) and physical mixtures (two independent supported metallocenes that are introduced to the reactor and start the polymerization together), using different ratios, i.e., 25-75, 50-50, 75-25, at three reaction temperatures, i.e., 30, 50 and 70°C. Most of the binary catalytic systems lead to bimodal molecular weight distributions. Polypropylenes produced by mixed catalysts are greatly influenced by the most active catalyst, while in PP coming from hybrid catalysts, as there is a strong interaction between both metallocenes, each one contributes according to its presence in the hybrid catalyst. Therefore, properties of obtained bimodal polypropylenes are quite influenced by the ratio between both metallocenes.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Bimodal polypropylene through binary metallocene catalytic systems: comparison between hybrid and mixed heterogeneous catalysts

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Esse resultado tem sido atribuído à possível interação entre os metalocenos combinados produzindo complexos bimetálicos inativos, inclusive durante a preparação do catalisador heterogêneo. 58 Além disso, a combinação do Cp 2 ZrCl 2 com (nBuCp) 2 ZrCl 2 não apresentou polímeros com mais alta polidispersão, ou mesmo uma distribuição bimodal, conforme era esperado pelos pesquisadores. 59 Esses resultados podem ser atribuí- De acordo com o exposto, é explícita a necessidade de uma boa seleção do par de metalocenos a combinar de forma a produzir um polímero com uma desejada distribuição de massa molar.…”

Section: Figura 6 Polidispersões Para a Blenda De Diferentes Fraçõesunclassified

Alargamento da distribuição de massa molar de polímeros sintetizados com catalisadores metalocênicos dual-site

Santos¹,

Fisch²,

Cardozo³

et al. 2008

Quím. Nova

View full text Add to dashboard Cite

. The main topics related to the use of dual-site catalysts in the production of polymers with broad molecular weight distribution are reviewed. The polymerization using dual-site catalysts is more economical and allows to produce a higher quality product than other processes, such as polymer blend and multistage reactors. However, the formulation of these catalysts is quite complicated since the same catalyst must produce distinct polymer grades. In addition, the release of patents concerning the combination of metallocenes and new technologies for polymerization shows that polymerization processes using dual-site catalysts are of current industrial interest.Keywords: metallocene; dual-site; molecular weight distribution. INTRODUÇÃOCatalisadores para a produção de poliolefinas têm sido continuamente estudados e melhorados desde o advento do primeiro catalisador Ziegler-Natta. Ao longo desses esforços, diferentes tipos de complexos foram investigados, entre eles os metalocenos. Durante a década de 50, o titanoceno (Cp 2 TiCl 2 ) foi um dos primeiros metalocenos a ser estudado. Nesses estudos, esse catalisador não apresentou uma atividade suficientemente alta para possibilitar uma aplicação industrial ao ser ativado com um alquil alumínio comum. Infelizmente, essa conclusão pode ser estendida para os demais metalocenos. Os catalisadores metalocênicos tornaram-se atrativos industrialmente após os estudos de Sinn e Kaminsky, no final da década de 70, que apresentaram o co-catalisador metilaluminoxano (MAO) formado pela hidrólise parcial de trimetilalumínio (TMA) como agente de ativação. Com esse cocatalisador, os metalocenos polimerizam com atividades mais altas e adequadas ao emprego em processos industriais. 1-3 A partir desse ponto, iniciaram-se intensivas pesquisas direcionadas para solucionar problemas relacionados aos processos industriais, principalmente de adaptação aos processos Ziegler-Natta heterogêne-os já existentes. Além disso, pesquisas relacionadas a novos tipos de estruturas organometálicas metalocênicas e não-metalocênicas foram e continuam em desenvolvimento. [4][5][6] Os sistemas metalocênicos permitem produzir polímeros com alta atividade catalítica, podendo ser até 100 vezes superior à atividade de um catalisador Ziegler-Natta convencional. Além disso, os metalocenos sintetizam quase todos os tipos de polímeros estéreo-específicos, como os polipropilenos isotático, sindiotático, hemitático e de bloco, graças principalmente à simetria e à esfera de coordenação do metal de transição. 7 Os polímeros sintetizados com esses catalisadores apresentam uma distribuição estreita de massa molar, isto é, polímeros com polidispersão próxima a dois, o que é atribuído à existência de apenas um tipo de sítio ativo. Embora uma distribuição estreita permita uma melhora nas suas propriedades mecânicas, esses polímeros não apresentam boas propriedades reológicas, necessárias à processabilidade da resina, especialmente para altas massas molares. [8][9][10] Para a obtenção de polímeros com uma distribuição de massa...

show abstract

“…Also catalytic systems based on zirconocene have been implemented for the polymerization of propylene in situ by impregnation on commercial silica using different impregnation techniques. Some results show increase in the molecular weight of the polymer …”

Section: Introductionmentioning

confidence: 99%

Preparation of polypropylene‐based nanocomposites using nanosized MCM‐41 as support and in situ polymerization

González

Quijada

Yazdani‐Pedram

et al. 2016

Polymer International

View full text Add to dashboard Cite

show abstract

Binary metallocene supported catalyst for propylene polymerization

Cited by 20 publications

References 13 publications

Bimodal polypropylene through binary metallocene catalytic systems: comparison between hybrid and mixed heterogeneous catalysts

Bimodal polypropylene through binary metallocene catalytic systems: comparison between hybrid and mixed heterogeneous catalysts

Alargamento da distribuição de massa molar de polímeros sintetizados com catalisadores metalocênicos dual-site

Preparation of polypropylene‐based nanocomposites using nanosized MCM‐41 as support and in situ polymerization

Contact Info

Product

Resources

About