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Polymerization of ethylene using zirconocenes supported on swellable cation-exchanged fluorotetrasilicic mica

Paper ID Volume ID Publish Year Pages File Format Full-Text
42969 45949 2009 7 PDF Available
Title
Polymerization of ethylene using zirconocenes supported on swellable cation-exchanged fluorotetrasilicic mica
Abstract

Supported catalysts consisting of Cp2ZrCl2 and cation-exchanged fluorotetrasilicic mica (Mn+-mica, Mn+ = Na+, Mg2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+) were prepared and employed in the ethylene polymerization or ethylene/1-hexene copolymerization in the presence of R3Al. The catalysts consisting of swellable Mg2+-mica and Zn2+-mica (both calcined at 200 °C) and Cp2ZrCl2 displayed high activity for the polymerization reaction. By contrast, when Mg2+-mica and Zn2+-mica were calcined above 250 °C, the swellability was lost, and the activities of Cp2ZrCl2 supported on these non-swellable micas were significantly reduced. The relationship between the activity and swellability of mica was clearly observed both in ethylene polymerizations employing (n-BuCp)2ZrCl2 in place of Cp2ZrCl2 and in ethylene/1-hexene copolymerizations using Cp2ZrCl2. The role of Mn+-mica for the activation of the metallocene complex was investigated by surface observation using a scanning electron microscope and by XRD measurements of the catalysts after polymerization of ethylene for a short time. The results of the surface observations indicated that polyethylene was produced on the edges of Mn+-mica lamellas at the initial stage of the polymerization. The XRD measurements show that the regularity of the stacked lamellas was immediately lost at this stage. The catalyst prepared by removing free Cp2ZrCl2 (i.e., unsupported Cp2ZrCl2, Cp2ZrCl2 dissolved into the catalyst slurry) showed extremely low activity, suggesting that the most of the active sites were formed through the reactions of Mn+-mica and free Cp2ZrCl2. These results indicate that the lamellas of Mn+-mica are peeled off at the initial stage of the polymerization and that exposed metal cations react with free-Cp2ZrCl2 to form additional active species. The swellability of Mn+-mica strongly affects the formation of additional active sites, and therefore the supported catalysts based on non-swellable Mn+-mica displayed only low activities.

Graphical abstractThe catalyst Cp2ZrCl2 supported on cation-exchanged fluorotetrasilicic mica showed a high activity for ethylene polymerization in the presence of R3Al. The results of SEM observation for the catalyst surface after polymerization for a short time indicated that the polymerization began on Cp2ZrCl2 located at the edges of the mica sheet.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Metallocene catalyst; Ethylene/1-hexene copolymerization; Swellability of mica
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Polymerization of ethylene using zirconocenes supported on swellable cation-exchanged fluorotetrasilicic mica
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 360, Issue 2, 1 June 2009, Pages 192–198
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us