Haag, Mônica Carcuchinski; Krug, Cristiano; Dupont, Jairton; de Galland, Griselda Barrera; dos Santos, João Henrique Zimnoch; Uozumi, Toshiya; Sano, Tsuneji; Soga, Kazuo
Effects of Al/Zr ratio on ethylene–propylene copolymerization with supported-zirconocene catalysts
Teil von
  • Journal of molecular catalysis. A, Chemical, 2001, Vol.169 (1), p.275-287
Ort / Verlag
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ScienceDirect Journals (5 years ago - present)
Effects of heterogenization parameters on compositional and catalytic properties of Et(Ind) 2ZrCl 2 supported on silica modified with MAO were evaluated using data on metal loading, catalyst activity in ethylene–propylene copolymerization, and polymer properties. The supported catalysts were prepared according to a 2 3 factorial design for multivariate analysis. The parameters studied were: MAO concentration in impregnation, Et(Ind) 2ZrCl 2 concentration in grafting, and immobilization temperature for both metallocene and organoaluminum. The grafting solution was monitored by UV–VIS spectroscopy, while the resulting catalyst systems were characterized by inductively-coupled plasma-optical emission spectroscopy (ICP-OES), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS). At high statistical significance, both MAO and Et(Ind) 2ZrCl 2 concentrations during preparation affected the determination of the final Al/Zr ratio on silica. The catalyst systems were tested in ethylene–propylene copolymerizations using external MAO as cocatalyst. Relationships were observed between (i) catalyst activity and the binding energy of Zr 3d 5/2 electrons and (ii) Al/Zr ratio on silica and the average ethylene incorporation. The polymer samples presented narrow molecular weight distribution, but according to differential scanning calorimetry (DSC), and cross-fractionation chromatography (CFC) data, catalyst systems with given Al/Zr ratios might yield different crystallites, suggesting a plural distribution of chemical composition.

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