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Analysis of supported zirconocenes by x‐ray emission and absorption techniques
Author(s) -
Loureiro Silvia R.,
Silveira Fernando,
Pires Gilvan P.,
Alves Maria do C.,
Stedile Fernanda C.,
dos Santos João Henrique Z.,
Bichinho Kátia M.,
Teranishi Toshiharu
Publication year - 2004
Publication title -
x‐ray spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.447
H-Index - 45
eISSN - 1097-4539
pISSN - 0049-8246
DOI - 10.1002/xrs.753
Subject(s) - cyclopentadienyl complex , catalysis , polymerization , chemistry , microanalysis , metal , metallocene , molar ratio , polymer chemistry , nuclear chemistry , inorganic chemistry , analytical chemistry (journal) , organic chemistry , polymer
Metal contents in supported zirconocene catalysts were comparatively determined by x‐ray fluorescence spectroscopy and Rutherford backscattering spectrometry. A series of supported zirconocenes was prepared by grafting sequentially Cp 2 ZrCl 2 (Cp = cyclopentadienyl) and (nBuCp) 2 ZrCl 2 on to silica. The addition order and molar ratio of the two catalysts were varied. The grafted metal content was shown to be coherent between the two techniques and was between 0.37 and 0.53 wt% Zr/SiO 2 . The steric effect played by the ligand influences the final zirconocene grafted content. No influence of the grafting order was observed. Nevertheless, catalyst systems in which (nBuCp) 2 ZrCl 2 was either immobilized in the first place or at a higher molar ratio were shown to be more active in ethylene polymerization. Extended x‐ray absorption fine structure analysis in the Zr‐edge showed that systems bearing Cp 2 ZrCl 2 and (nBuCp) 2 ZrCl 2 in a 1:3 molar ratio afforded a more disoriented system. According to electron probe microanalysis, the metal distribution in the catalyst particle was more uniform than that resulting from the immobilization of solely (nBuCp) 2 ZrCl 2 on silica. Copyright © 2004 John Wiley & Sons, Ltd.