Influence of Aluminium Alkyl Compounds on the High-Pressure Polymerization of Ethylene with Ternary Metallocene-Based Catalysts. Investigation of Chain Transfer to the Aluminium

Götz, Christian; Rau, Alexander; Luft, Gerhard

doi:10.1002/1439-2054(20020101)287:1<16::aid-mame16>3.3.co;2-0

Cited by 9 publications

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“…Industrial applications of homogeneous Ziegler–Natta catalysts1–5 have attracted recent research interest, and a high‐pressure polymerization process seems one of the most promising methods for that aim 6. There have been reports on polymerizations with group‐4 metallocene catalysts under high pressures such as 100–200 MPa,7–12 and we previously reported the remarkable effect of high pressures up to 1500 MPa on metallocene‐catalyzed α‐olefin polymerizations 13–17. The catalytic activity was greatly enhanced by high pressures and reached its maximum at 250–500 MPa.…”

Section: Introductionmentioning

confidence: 87%

Nickel‐ and palladium‐catalyzed olefin polymerization under high pressures

Suzuki

Masubuchi

et al. 2002

J. Polym. Sci. A Polym. Chem.

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The polymerization of 1-hexene under high pressures (100 -750 MPa) was investigated with nickel-␣-diimine complex/methylaluminoxane and palladium-␣-diimine complex/methylaluminoxane as catalyst systems. The catalytic activity of both the nickel and palladium complexes monotonously increased as pressure rose and became two to four times higher than that observed at atmospheric pressure. Palladium catalysts gave poly(1-hexene)s with higher molecular weights under high pressure, whereas nickel-catalyzed high-pressure polymerizations gave polymers with higher molecular weights only at rather low monomer concentrations. The living-like character in the palladium-catalyzed polymerizations was somewhat enhanced under higher pressures, whereas the nickel-catalyzed polymerizations under high pressures were not living. More branches were found in the polymers produced by nickel catalysts at higher pressures. The chain-transfer reaction seemed to be accelerated by the high pressure in the nickel-catalyzed reactions, although this was not apparent in the palladium-catalyzed reactions. Dimers formed and were accompanied by high molecular weight polymers when nickel catalysts were used under high pressures and at high monomer concentrations. The possibility that very congested five-coordinated species act as key intermediates for the dimerization is discussed.

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Section: Introductionmentioning

confidence: 87%

Nickel‐ and palladium‐catalyzed olefin polymerization under high pressures

Suzuki

Masubuchi

et al. 2002

J. Polym. Sci. A Polym. Chem.

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“…These Zr/Al heterobimetallics appear to be involved in chain transfer , and have been assumed to be “dormant” and incapable of inserting olefin themselves. − We have therefore examined the kinetics of exchange between trimethylaluminum and these adducts, first observed by Bochmann, of the general formula [Cp 2 M(μ-Me) 2 AlMe 2 ] + ( 2 ), where M = Ti, Zr, Hf.…”

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confidence: 99%

Effectiveness in Catalyzing Carboalumination Can Be Inferred from the Rate of Dissociation of M/Al Dimers

Petros

Norton

2004

Organometallics

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“…This suggests that when the amount of TIBA is high enough to alkylate and clean up the reaction medium, the catalytic activity is not significantly modified. However, it was reported, for a related system, that for very high Al concentrations the productivity decreases 17. This is a very positive feature of this catalytic system when compared with its analogous one, activated in the presence of MAO, which normally requires higher ratio of Al/Zr 18…”

Section: Resultsmentioning

confidence: 85%

High‐temperature and high‐pressure ethylene polymerization using a cationic activated metallocene catalytic system

Oliveira

Brandão

Freitas

et al. 2008

Polymer International

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BACKGROUND: Normally, olefin polymerization via metallocene-based catalysis occurs under mild conditions. However, most technology developed for polyolefin production is designed for more severe temperature and pressure processes. Attaining more thermally stable metallocene systems for industrial applications is an important challenge for researchers. RESULTS:A systematic study of ethylene homopolymerization at higher temperatures and pressures, employing the ternary system Ph 2 C(Cp)(Flu)ZrCl 2 /PhNHMe 2 B(C 6 F 5 ) 4 /(i-Bu) 3 Al, is presented The optimal activity for this system is achieved with a Zr/B/Al molar ratio of 1/6/250 and a temperatures of around 130 • C. However, the amount of activator strongly affects the molecular weight and the polydispersity of the polymers produced. Polyethylene produced with Zr/B/Al molar ratios between 1/2/250 and 1/6/250 show no significant difference in their temperature of fusion (T m ) and their crystallinity (X c ). In contrast, in the presence of activator amounts higher than 1/6/250, both the temperature of fusion and polymer crystallinity undergo a steep decrease. All polymers presented lamellar morphology when the activator was present, and an amorphous aspect when the activator was not employed. CONCLUSION:The presence of the activator is essential for thermal stabilization of the catalytic system. Variation of the Zr/B/Al ratio leads to modifications of the catalytic activity as well as to the properties of the polymers synthesized.

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Influence of Aluminium Alkyl Compounds on the High-Pressure Polymerization of Ethylene with Ternary Metallocene-Based Catalysts. Investigation of Chain Transfer to the Aluminium

Cited by 9 publications

References 0 publications

Nickel‐ and palladium‐catalyzed olefin polymerization under high pressures

Nickel‐ and palladium‐catalyzed olefin polymerization under high pressures

Effectiveness in Catalyzing Carboalumination Can Be Inferred from the Rate of Dissociation of M/Al Dimers

High‐temperature and high‐pressure ethylene polymerization using a cationic activated metallocene catalytic system

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