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On the sensitivity of metallocene catalysts toward molecular hydrogen during ethylene polymerization
Author(s) -
Blom Richard,
Dahl Ivar M.
Publication year - 1999
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19990201)200:2<442::aid-macp442>3.0.co;2-i
Subject(s) - metallocene , polymer chemistry , polymerization , catalysis , ethylene , chemistry , hydrogen , polymer , post metallocene catalyst , chain transfer , organic chemistry , radical polymerization
Polymerization of ethylene has been performed with heterogenised metallocene catalysts in the presence of hydrogen as chain transfer agent in a slurry semi‐batch reactor. On‐line GC analyses show that both Cp 2 ZrCl 2 /MAO/SiO 2 and Cp* 2 ZrCl 2 /MAO/SiO 2 are much more reactive toward hydrogen as compared to commercial catalysts such as CrO/SiO 2 and CrCp 2 /SiO 2 . While narrow molecular weight distributions are obtained for the polymer produced with the metallocene catalysts in the absence of hydrogen, broad distributions are obtained when hydrogen is present. The broadening is at least partly a consequence of the way hydrogen is introduced, but especially for Cp* 2 ZrCl 2 /MAO/SiO 2 , more than one active site might be present. Polymerizations with deuterium show that both metallocene catalysts react cleanly with deuterium, forming —CH 2 D fragments.