Results 171 to 180 of about 1,886 (220)

“Oscillating” Metallocene Catalysts: How Do They Oscillate?

Angewandte Chemie International Edition, 2002
Based on the results of a series of propylene polymns. using oscillating metallocene catalysts of type [(2-Ar-indenyl)2ZrCl2] (Ar = C6H5 or 3,5-(t-Bu)2-4-MeO-C6H2) with various cocatalysts (MAO, TIBAl), the oscillating behavior of the zirconocenes is discussed with respect to the rac/meso stereochem. outcome of the obtained polypropylenes.
BUSICO, VINCENZO, CIPULLO, ROBERTA, Kretschmer Winfried P, TALARICO, GIOVANNI, VACATELLO, MICHELE, Van Axel Castelli Valeria   +5 more
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Supported Metallocene Catalysts

CATTECH, 2000
Single-site olefin polymerization catalysts have been researched extensively and are now achieving wide acceptance in the polyolefin industry. To achieve commercial significance in the majority of today's commercial processes, these soluble catalysts must be immobilized on a carrier.
Edmund M. Carnahan, Grant B. Jacobsen
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“Oscillating” Metallocene Catalysts:  What Stops the Oscillation?

Journal of the American Chemical Society, 2003
The 150 MHz (13)C NMR microstructural analysis of polypropylene samples produced with two representative "oscillating" metallocene catalysts of largely different steric hindrance, namely [(2-(3,5-di-tert-butyl-4-methoxyphenyl)indenyl)(2)ZrP](+) and [(2-phenylindenyl)(2)ZrP](+) (P = polymeryl), and the implications on the origin of the stereocontrol are
BUSICO, VINCENZO, Van Axel Castelli Valeria, Aprea Paola, CIPULLO, ROBERTA, Segre Annalaura, TALARICO, GIOVANNI, VACATELLO, MICHELE   +6 more
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Polymerization of propene by post‐metallocene catalysts

Macromolecular Symposia, 2004
AbstractIn the last few years several non‐metallocene catalysts have been disclosed as efficient catalysts for the stereospecific polymerization of propene.In this paper we summarize some recent literature data and some new results concerning the stereochemical mechanism of propene polymerization promoted by late transition metal systems and group 4 ...
LAMBERTI, Marina, MAZZEO, Mina, PAPPALARDO D, ZAMBELLI A, PELLECCHIA, Claudio   +4 more
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Hard versus Soft Materials as Supports for Metallocene and Post‐Metallocene Catalysts

Macromolecular Reaction Engineering, 2009
AbstractThe influence of organic supports on the polymerization behavior of post‐metallocene catalysts is studied and compared with similarly supported titanium and zirconium metallocenes. The effects of the immobilization, activation, and polymerization process were studied by video microscopy, laser confocal fluorescence microscopy, SEM, and TEM.
Naundorf, C., Ferrari, D., Rojas, G., Fink, G., Klapper, M., Müllen, K.   +5 more
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Inversion of stereoselectivity in a metallocene catalyst

Macromolecular Rapid Communications, 1996
AbstractInversion of stereoselectivity of a particular metallocene (Me2Si(Flu) (N‐t‐Bu)ZrCl2) (Me: methyl, Flu: fluorenyl, t‐Bu: tert‐butyl) from syndiospecific into isospecific was observed by changing the cocatalyst from methylaluminoxane (MAO) to [Ph3C]+ [B(C6F5)4]−/AliBu3 (iBu:isobutyl).
Tetsunosuke Shiomura, Tadashi Asanuma, Norihide Inoue   +2 more
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Heterogenization of Metallocene Catalysts for Alkene Polymerization

Angewandte Chemie International Edition, 1999
Beyond mere convenience: In large-scale industrial processes for alkene polymerization the essentially homogeneous metallocene/activator catalyst systems are heterogenized (example shown) to improve polymer properties. New mesoporous and organic catalyst supports and their application in this field of catalysis are described.
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Metallocene and Ziegler-Natta Catalysts

2021
Fifty years ago, Karl Ziegler and Natta won the Nobel Prize for their discovery of the catalytic polymerization of ethylene and propylene using titanium compounds with aluminum-alkyls as co-catalysts. Polyolefins are constantly growing and are now one of the most important highconsumption polymers. New metallocene/methylaluminoxane (MAO) catalysts have
Vinod Vishwakarma, Sandeep, Kulkarni, S.G.   +1 more
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Heterogeneous Metallocene Catalysts

1995
Copolymerizations of olefins were carried out with the SiO2-, AI2O3- and MgCl2-supported Et[IndH4]2ZrCl2 catalysts combined with AIR3 as cocatalyst and the results were compared with those obtained previously in the presence of homogeneous Et[IndH4]2ZrCl2-MAO catalyst.
Kazuo Soga, Manabu Kaminaka, Hyun Joon Kim, Takeshi Shiono   +3 more
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Metallocene catalysts for olefin polymerization

Coordination Chemistry Reviews, 1999
Abstract The discovery of metallocene methylaluminoxane (MAO) catalysts has opened a frontier in the area of organometallic chemistry, polymer synthesis and processing. A great number of different titanocenes and zirconocenes have been synthesized that give tailored polymers of totally different structures, let control polymer tacticity, molecular ...
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