The role of the support in the performance of grafted metallocene catalysts

Abstract

A series of supports - differing in their textural properties, the nature of their surface sites, and in their crystallinities - were investigated in the sequential grafting reaction of Cp2ZrCl2 and (nBuCp)2ZrCl2 mixtures. The catalyst systems were analyzed by Rutherford backscattering spectrometry, AFM, EXAFS, and nitrogen adsorption. All systems were shown to be active in ethylene polymerization reactions when methylaluminoxane was used as the cocatalyst. Experimental results are discussed in terms of the relationships between the grafted metal content, the catalyst activity, the surface roughness and polarity, the interatomic Zr-C and Zr-O distances of the grafted species and the molecular weights of the resulting polyethylenes. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.