Results 221 to 230 of about 6,795 (264)

Rare-Earth Ziegler−Natta Catalysts:  Carboxylate−Alkyl Interchange

Organometallics, 2002
Alkylated rare-earth-metal centers are definitely formed in “Mischkatalysatoren”:  the homoleptic, tailor-made rare-earth carboxylate complexes {Ln(O2CC6H2iPr3-2,4,6)3}n (Ln = Y, La, Nd, Lu) react with trimethylaluminum to yield hexane-soluble monolanthanide complexes of the larger elements featuring a η2-coordinating tetraalkylaluminate ligand and a ...
Fischbach, Andreas, Perdih, Franc, Sirsch, Peter, Scherer, Wolfgang, Anwander, Reiner   +4 more
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Polyethylenimines: Multidentate Electron Donors for Ziegler–Natta Catalysts

The Journal of Physical Chemistry C, 2017
Polyethylenimines, polymers bearing amino functionalities, are studied for the first time as internal electron donors for Ziegler–Natta catalysts. An advantage of polyethylenimines (PEIs) compared to the conventional phthalate electron donors is their relative harmlessness. Interaction of PEI with MgCl2 support was studied using computational (DFT; M06-
Ville H. Nissinen, Mikko Linnolahti, Andrey S. Bazhenov, Tuula T. Pakkanen, Tapani A. Pakkanen, Peter Denifl, Timo Leinonen, Kumudini Jayaratne, Anneli Pakkanen   +8 more
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Accelerating the Research Approach to Ziegler–Natta Catalysts

Industrial & Engineering Chemistry Research, 2016
Despite 60 years of history and a stunning success, Ti-based Ziegler–Natta catalysts for the production of isotactic polypropylene remain black-box systems, and progress still relies on trial and error. This represents a limitation in a moment when the most widely used industrial systems, containing phthalates as selective modifiers, need to be ...
BUSICO, VINCENZO, CIPULLO, ROBERTA, Mingione, Alessio, Rongo, Luca   +3 more
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Amalgamation of ziegler‐natta and metallocene catalysts

Macromolecular Symposia, 1997
AbstractThe MgCl2 supported half titanocenes and Ti(4, 4, 4‐trifluoro‐1‐phenyl‐1, 3‐butanedionato)2Cl2 catalysts were synthesized and applied to propene polymerization. Without supporting on MgCl2, those complexes displayed almost no activity even using methylaluminoxane (MAO) as cocatalyst.
K. Soga, J. Jin, E. Kaji, T. Uozumi, Y. Suzuki   +4 more
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Synthesis of highly improved Ziegler‐Natta catalyst

Journal of Applied Polymer Science, 2009
AbstractThe effects of media viscosity, mixing speed, and injection time on catalyst average particle size (APS), particle size distribution (PSD), and morphology in both conditions, with and without emulsifier, were investigated. Supports were prepared using a so‐called recrystallization method; then they were catalyzed under the same condition.
Majid Monji, Saeed Pourmahdian, Mohammad Vatankhah, Faramarz Afshar Taromi   +3 more
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Ziegler-Natta catalysts for olefin polymerizations

Progress in Polymer Science, 1997
Abstract This article reviews the recent developments of Ziegler-Natta and metallocene catalysts for olefin polymerizations. The roles of magnesium dichloride and electron donors on the activity and stereospecificity of Ziegler-Natta catalysts, as well as the roles of methylalumoxane and ligands on the activation and performance of metallocene ...
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Ethylene polymerization with heterogeneous Ziegler-Natta catalysts

Polymer Bulletin, 1995
TiCl4/SiO2, Ti(OC4H9)4/SiO2, MgCl2/TiCl4/SiO2 and MgCl2/Ti(OC4H9)4/SiO2 catalysts were prepared by treating silica gel with TiCl4, Ti(OC4H9)4, MgCl2/TiCl4 or MgCl2/Ti(OC4H9)4 in tetrahydrofuran (THF) solution. Ethylene polymerization was performed with these catalysts activated by common alkylaluminum compounds. The influence of magnesium dichloride on
Luiz Claudio de Santa Maria, Fernanda M. B. Coutinho, Marcos L. Dias, Maria C. M. Gonçalves   +3 more
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Stereochemical Control in Ziegler-Natta Catalysts

1987
The remarkably high level of stereoselectivity associated with magnesium chloride-based catalysts is realized only in the presence of a selectivity control agent (SCA), frequently an aromatic ester.1 The usual effect of the SCA is to reduce activity while significantly enhancing stereoselectivity.2 Fortunately, the reduction in productivity (65%) is ...
S. E. Wilson, W. L. Callender, R. C. Job
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Particle Control of Supported Ziegler-Natta Catalysts

1987
A good catalyst for olefin polymerization should exhibit, among other characteristics, good morphological control of the resulting polymers, as well as high activity, control of the molecular weight and molecular weight distribution. Thus, in regard to the polymer morphology, particles with spherical shape, having an average diameter of about 500 u, no
A. Muñoz-Escalona, J. G. Hernández, J. A. Gallardo, A. Sustic   +3 more
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Stereospecificity of Heterogeneous Ziegler-Natta Catalysts

1985
The most prominent feature of heterogeneous Ziegler-Natta catalysts is their ability to produce isotactic olefin polymers exhibiting a combination of outstanding mechanical characteristics. This ability adds a new dimension to the description of the catalysts and the polymerization processes: the study of catalyst and polymerization parameters ...
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