Catalysts Based on Supported Metallocenes forα-Olefin Polymerization

Abstract

The central purpose of this work is to develop and efficient way to attach the metallocene to a support without diminishing its catalytic activity. This article describes several methods to prepare supported EtInd 2 ZrCl 2 (EBI) on MAO/SiO 2 , varying the washing step durations and washing step temperatures. The best method is the one that supports 0.7% Zr on MAO/SiO 2 with a final content of Al near 5.8%. It seems that this method combines high efficiency in MAO usage at the preparation step and high activity in propylene polymerization. The activity of the supported catalysts EBI/MAO/SiO 2 decreases to the third of the soluble catalysts EBI/MAO with the same Al/Zr molar ratio. Zr contents higher than 0.7% produce catalysts with lower productivities. Probably, a MAO coverage on SiO 2 that is higher than a monolayer is not useful in order to stabilize the zirconocene on the MAO/SiO 2 support. This paper reports the kinetics of the supported catalysts and a discussion about the shape of the curves and the stability of the catalysts is appended. The molecular weight of poly(propylene) obtained with supported catalyst increases, especially for the best preparation, comparing it with material obtained with the soluble one. The regioregularity of poly(propylene) increases when a Lewis Base (ethyl benzoate-E.B.) is added as external additive to the system EBI/MAO/SiO 2 and the activity of the supported catalyst is improved.