Propene polymerization using homogeneous MAO-activated metallocene catalysts: Me2Si(Benz[e]Indenyl)2ZrCl2/MAO vs. Me2Si(2-Me-Benz[e]Indenyl)2ZrCl2/MAO
| Autor: | Hans-Herbert Brintzinger, Franz Dr Langhauser, David Fischer, Rolf Mülhaupt, Udo M. Stehling, Stephan Jüngling |
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| Rok vydání: | 1995 |
| Předmět: |
Order of reaction
Polymers and Plastics Chemistry Organic Chemistry Chain transfer Homogeneous catalysis Propene Catalysis chain transfer methylalumoxane 1-insertion chemistry.chemical_compound Polymerization zirconocene polymerization end groups hydrogen ddc:540 Polymer chemistry Materials Chemistry Ziegler–Natta catalyst Metallocene |
| Zdroj: | Journal of Polymer Science Part A: Polymer Chemistry. 33:1305-1317 |
| ISSN: | 1099-0518 0887-624X |
| DOI: | 10.1002/pola.1995.080330813 |
| Popis: | Propene was polymerized at 40°C and 2-bar propene in toluene using methylalumoxane (MAO) activated rac-Me2Si(Benz[e]Indenyl)2ZrCl2 (BI) and rac-Me2Si(2-Me-Benz[e]Indenyl)2ZrCl2 (MBI). Catalyst BI/MAO polymerizes propene with high activity to afford low molecular weight polypropylene, whereas MBI/MAO is less active and produces high molecular weight polypropylene. Variation of reaction conditions such as propene concentration, temperature, concentration of catalyst components, and addition of hydrogen reveals that the lower molecular weight polypropylene produced with BI/MAO results from chain transfer to propene monomer following a 2,1-insertion. A large fraction of both metallocene catalyst systems is deactivated upon 2,1-insertion. Such dormant sites can be reactivated by H2-addition, which affords active metallocene hydrides. This effect of H2-addition is reflected by a decreasing content of head-to-head enchainment and the formation of polypropylene with n-butyl end groups. Both catalysts show a strong dependence of activity on propene concentration that indicates a formal reaction order of 1.7 with respect to propene. MBI/MAO shows a much higher dependence of the activity on temperature than BI/MAO. At elevated temperatures, MBI/MAO polymerizes propene faster than BI/MAO. |
| Databáze: | OpenAIRE |
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