Effects of MgCl2 Crystallographic Structure on Active Centre Formation in Immobilized Single-Centre and Ziegler–Natta Catalysts for Ethylene Polymerization
✍ Scribed by Rubin Huang; Federica Malizia; Gianni Pennini; Cor E. Koning; John C. Chadwick
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 261 KB
- Volume
- 29
- Category
- Article
- ISSN
- 1022-1336
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✦ Synopsis
Abstract
The ability of a MgCl~2~ support to activate a transition metal catalyst has been found to depend both on the crystallographic structure of the support and on the nature of the catalyst. A high degree of crystallographic disorder can be very effective for the immobilization and activation of titanium and vanadium complexes, but is not necessarily effective for zirconocene activation. A highly disordered support prepared by the reaction of MgBu~2~ with HCl gave high activity with TiCl~4~ but low activity with (n‐PrCp)~2~ZrCl~2~. High polymerization activities with the zirconocene were only obtained with supports of type MgCl~2~/AlR~n~(OEt)~3−n~ prepared from the reaction of AlR~3~ with MgCl~2~ · 1.1EtOH. These supports are characterized by additional peaks in the X‐ray diffraction pattern, indicating the presence of a crystalline structure which is absent in the other supports and contains highly Lewis acidic sites able to generate the active metallocenium species.
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