Study on the role of methylalumoxane in homogeneous olefin polymerization

Resconi, Luigi; Bossi, Sandro; Abis, Luigi

doi:10.1021/ma00222a029

Cited by 199 publications

(121 citation statements)

References 2 publications

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“…All samples displayed a broad resonance at ␦ ϭ Ϫ0.20 ppm assigned to the methyl protons of the oligomeric [O-Al(CH 3 )-] compounds, confirming the result reported by Resconi et al 2 A sharp singlet at ␦ ϭ Ϫ0.36 ppm assigned to the free Al 2 (CH 3 ) (TMA) was observed in Figure 3 The resonance at ␦ ϭ Ϫ0.58 ppm has not been reported for MAO in previous literature.…”

Section: Figuresupporting

confidence: 88%

“…Both have a sharp singlet at ␦ ϭ Ϫ0.36 ppm assigned to the methyl protons of TMA, as already reported by Resconi et al, 2 and another small one at ␦ ϭ Ϫ0.58 ppm not reported in the published literature was also observed, which will be discussed later.…”

Section: Tmasupporting

confidence: 80%

“…It may be concluded that at relatively lower concentration, the spectrum mainly displays the resonance of the residual TMA and MAO with low molecular weight (2), and at higher concentration it displays that of MAO with relatively high molecular weight (3). It can also be concluded that the hydrolysis concentration of TMA is important for the molecular weight of MAO after the same reaction time.…”

Section: Influence Of the Hydrolysis Concentration Of Tmamentioning

confidence: 91%

“…Ueyama et al 8 first observed that the proton resonance of dimerized MAO at ␦ ϭ Ϫ0.95 ppm, whereas Resconi et al 2 reported that the resonance of MAO with high molecular weight was observed at ␦ ϭ Ϫ0.20 ppm. The resonance at ␦ ϭ Ϫ0.58 ppm was intermediate between that of the protons of MAO with high molecular weight (Ϫ0.20 ppm) (1) and that of Me 2 AlOAlMe 2 and thus was assigned to MAO with low molecular weight (2) (Ϫ0.95 ppm), corresponding to the middle stage of the reaction from low molecular weight to high molecular weight.…”

Section: Figurementioning

confidence: 99%

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In situ1H- and27AL-NMR studies on metallocene catalyst systems?Catalysts for olefin polymerization

Zhang¹,

Duan²,

Zheng³

et al. 2000

J. Appl. Polym. Sci.

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ABSTRACT:The process of partial hydrolysis reaction of TMA with water and the interaction of zirconocene dichloride (Cp 2 ZrCl 2 ) with TMA, MAO, and the in situ partially hydrolyzed products of TMA were studied by in situ Al-NMR spectroscopy. The 1 H-NMR spectra of MAO samples and the in situ hydrolyzed products of TMA with water under different conditions are different. A new peak at ␦ ϭ Ϫ0.58 ppm in 1 H-NMR spectra is observed, and is supposed to be due to the methyl resonance of MAO with low molecular weight. Alkylation reaction is observed between Cp 2 ZrCl 2 and TMA, MAO, and the in situ hydrolyzed products of TMA, and TMA is supposed to be the actual alkylating agent.27 Al-NMR studies show that MAO is tetra-coordinated.

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Section: Figuresupporting

confidence: 88%

Section: Tmasupporting

confidence: 80%

Section: Influence Of the Hydrolysis Concentration Of Tmamentioning

confidence: 91%

Section: Figurementioning

confidence: 99%

See 2 more Smart Citations

In situ1H- and27AL-NMR studies on metallocene catalyst systems?Catalysts for olefin polymerization

Zhang¹,

Duan²,

Zheng³

et al. 2000

J. Appl. Polym. Sci.

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“…For example, AlMe 3 can cause variation in catalytic productivity and also changes in the properties of the polymer [115][116][117]. Activation of zirconocene complexes with AlMe 3 can lead to a small amount of activity but are significantly less productive than their MAO-activated analogues [118]. The presence of AlMe 3 leads to the formation of heterobimetallic species of the type [L n M(l-Me 2 )AlMe 2 ]…”

Section: Alme 3 and Its Effects On Alkyl Cations And Polymerisationmentioning

confidence: 99%

Group 4 metal complexes for homogeneous olefin polymerisation: a short tutorial review

2015

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The discovery of transition metal-catalysed polymerisation of olefins in the 1950s by Ziegler and Natta was of huge importance. Over the last 30 years, the interest in homogenous polymerisation has not only grown but has changed focus from primarily studying the metallocene complexes of Group 4 to widespread exploration of postmetallocene systems. This is a consequence of extensive patenting of the metallocene catalyst systems, as well as for general interest in the improvement of polyolefin catalysis. The plastics industry produces more than 10 7 tonnes of polyethylene, polypropylene and polystyrene each year worldwide, and the study of well-defined homogenous catalysts is invaluable in uncovering the mechanism of polymerisation and the fundamental properties of the active species. This short Tutorial Review gives an overview of homogenous transition metal Ziegler-Natta catalysis in general as well as an overview of a selection of Group 4 post-metallocene catalysts. An overview of the synthesis and reactions of alkyl cations relevant to olefin polymerisation is also given. Finally, this review summarises recent advances in bimetallic catalysts for olefin polymerisation.

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Ethylene coordination, insertion, and chain transfer at a cationic aluminum center: A comparative study withAb Initio correlated level and density functional methods

2000

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The performance of correlated ab initio methods and DFT methods was compared for the propagation and chain transfer steps of ethylene polymerization by a model aluminum–amidinate system, [{HC(NH)2}AlCH2CH3]+. All methods agree that the main chain transfer mechanism is β‐hydrogen transfer to the monomer (BHT), and that this is substantially easier than propagation; implications for the real Jordan system are discussed briefly. Counterpoise corrections are necessary to obtain reasonable olefin complexation energies. Activation energies are consistently lower at DFT (BP86, B3LYP) than at ab initio levels [MP2, MP3, MP4, CI, CCSD(T)]; the differences are particularly large (16 kcal/mol) for the BHT reaction. This is suggested to be related to the known problem of DFT in describing hydrogen bridged systems. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 398–410, 2000

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Study on the role of methylalumoxane in homogeneous olefin polymerization

Cited by 199 publications

References 2 publications

In situ1H- and27AL-NMR studies on metallocene catalyst systems?Catalysts for olefin polymerization

In situ1H- and27AL-NMR studies on metallocene catalyst systems?Catalysts for olefin polymerization

Group 4 metal complexes for homogeneous olefin polymerisation: a short tutorial review

Ethylene coordination, insertion, and chain transfer at a cationic aluminum center: A comparative study withAb Initio correlated level and density functional methods

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