Abstract
Supported catalysts for ethylene polymerization have been prepared by interaction of Cp 2ZrX 2 (Cp= η 5-C 5H 5, X=Cl or CH 3) with silica chemically modified by (CH 3) 3SiCl (TMCS) or trialkylaluminium compounds AlR 3 (R=C 2H 5 (TEA) and i C 4H 9 (TIBA)). The interactions between the modificators and the silica surface have been examined by 1 H solid-state MAS NMR spectroscopy, DRIFTS and chemical analysis. The Cp 2Zr(CH 3) 2/SiO 2–TMCS catalyst showed a fairly high activity in ethylene polymerization (30–300 kg PE(mol Zr·h·bar) −1) even in the absence of any cocatalysts specially added. The addition of the cocatalyst (MAO or TIBA) led to a further increase in the activity of the supported catalysts. Polyethylene obtained with the Cp 2Zr(CH 3) 2/SiO 2–TMCS catalyst without any cocatalyst consisted of uniform polymer particles of a spherical shape replicating that of the silica particles, whereas the shapeless aggregates of finely dispersed polymer particles similar to those usually obtained with homogeneous systems were produced with the same supported catalyst in the presence of the MAO cocatalyst.
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