Stopped-flow polymerizations of ethene and propene in the presence of the catalyst systemrac-Me2Si(2-methyl-4-phenyl-1-indenyl)2ZrCl2/methylaluminoxane

Busico, Vincenzo; Cipullo, Roberta; Esposito, V.

doi:10.1002/(sici)1521-3927(19990301)20:3<116::aid-marc116>3.0.co;2-a

Cited by 82 publications

(101 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…An interesting feature of the whole catalyst family is an unusually low [for Ziegler-Natta catalysis (26)(27)(28)] turnover frequency, as if the polymerization occurred ''at slow motion.'' In particular, for the most sterically congested catalysts 4, 6, and 7 we measured average chain growth times of several hours at 25°C (under the conditions described in Materials and Methods).…”

Section: The Coordination Around Zr Is Distorted-octahedral With Tranmentioning

confidence: 99%

Design of stereoselective Ziegler–Natta propene polymerization catalysts

Busico

Cipullo

Pellecchia

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

After five decades of largely serendipitous (albeit formidable) progress, catalyst design in Ziegler-Natta olefin polymerization, i.e., the rational implementation of new active species to target predetermined polyolefin architectures, has ultimately become a realistic ambition, thanks to a much deeper fundamental understanding and major advances in the tools of computational chemistry. In this article, we discuss, as a case history, a unique class of stereorigid C 2-symmetric bis(phenoxy-amine)Zr(IV) catalysts with controlled kinetic behavior. A large variety of polypropylene microstructures have been obtained with these catalysts by modulating the steric demand of one key substituent, without altering the nature and symmetry of the ancillary ligand framework, under the guidance of computer modeling. This unusual achievement is relevant per se and for the perspective implications in catalyst discovery.enantioselectivity ͉ olefin polymerization ͉ polypropylene

show abstract

Section: The Coordination Around Zr Is Distorted-octahedral With Tranmentioning

confidence: 99%

Design of stereoselective Ziegler–Natta propene polymerization catalysts

Busico

Cipullo

Pellecchia

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

show abstract

“…O método Stopped-Flow ¶ (SFM) [92] , comumente usado em estudos de cinética homogênea e para análises de polimerizações em solução e em suspensão [93][94][95] , também é extensamente empregado para estudo do desenvolvimento morfológico de partículas poliméricas em polimerizações conduzidas com catalisadores heterogêneos em experimentos realizados com tempos de polimerização extremamente curtos em condições industriais de operação [96][97][98][99][100][101][102][103][104] . Seguindo o conceito similar ao SFM, Machado et al [105] desenvolveram um novo aparato experimental (denominado de Short Stop Reactor ** -SSR) especialmente para o estudo da polimerização nascente e a fragmentação de catalisadores heterogêneos em polimerizações de olefinas conduzidas em fase gasosa.…”

Section: A Etapa De Prepolimerizaçãounclassified

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

Machado

Pinto

2011

Polímeros

View full text Add to dashboard Cite

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...

show abstract

“…For metallocene/MAO-catalyzed ethylene and propylene polymerization, the average lifetime of a growing chain is typically less than seconds, and time-related effects can only be observed with stopped-flow techniques. [11] The fit of the first-order copolymerization equation serves only for illustration. Detailed 13 C NMR analysis of the microstructure has revealed that the penultimate model (second-order Markovian statistics) describes the E-N copolymerization better.…”

Section: Determination Of Kinetics Parameters and Number Of Active Sitesmentioning

confidence: 99%

“…Busico et al [11] have used Equation (3) to quantify the kinetics of the stopped flow polymerizations of ethylene and propylene.…”

Section: Determination Of Kinetics Parameters and Number Of Active Sitesmentioning

confidence: 99%

“…It allows us to use 'standard' laboratory equipment and procedures, and to study effects, which for a-olefins can usually only be observed by stopped-flow techniques. [11] Living polymerization of a-olefins has received much attention in recent years [11,12] and various catalyst systems have been proposed to achieve this. [13] However, living polymerizations of olefins with metallocenes in combination with MAO are quite rare.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Kinetic Studies of the Copolymerization of Ethylene with Norbornene by ansa‐Zirconocene/Methylaluminoxane Catalysts: Evidence of a Long‐Lasting “Quasi‐Living” Initial Period

Jansen

Mendichi

Tritto

2003

Macro Chemistry & Physics

View full text Add to dashboard Cite

Copolymers of ethylene (E) with norbornene (N) were synthesized using the catalysts rac‐Et(Ind)2ZrCl2/MAO (1), 90%rac/10%meso‐Et(4,7‐Me2Ind)2ZrCl2/MAO (2), and rac‐H2C(3‐t‐BuInd)2ZrCl2/MAO (3). Catalyst activity, molar mass (MM), and copolymer composition were studied as a function of time. The polymers showed an unusually narrow molar mass distribution (MMD) and a significant increase of their MM with time for up to one hour, suggesting a “quasi‐living” polymerization at 30 °C. The experimental data were fitted to kinetic equations and the propagation and transfer reactions were described in quantitative terms. Norbornene greatly depressed the propagation rate, along with the chain transfer rate. The more sterically hindered catalysts of the series showed lower propagation and chain transfer turnover frequency than 1 and yielded polymers with a low (2) to very low (3) norbornene content. The presence of norbornene in solution seemed to be one of the main factors responsible for the observed “quasi‐living” character of the copolymerization, probably due to coordination of norbornene to the active site. Time‐resolved kinetic studies also allowed for the calculation of the fraction of active metal centers, ranging from 56% (3) and 66–68% (1) to 94% (2) of the total zirconium present, depending on catalyst structure.

show abstract

Stopped-flow polymerizations of ethene and propene in the presence of the catalyst systemrac-Me2Si(2-methyl-4-phenyl-1-indenyl)2ZrCl2/methylaluminoxane

Cited by 82 publications

References 12 publications

Design of stereoselective Ziegler–Natta propene polymerization catalysts

Design of stereoselective Ziegler–Natta propene polymerization catalysts

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

Kinetic Studies of the Copolymerization of Ethylene with Norbornene by ansa‐Zirconocene/Methylaluminoxane Catalysts: Evidence of a Long‐Lasting “Quasi‐Living” Initial Period

Contact Info

Product

Resources

About