Catalysts Based on Supported Metallocenes forα-Olefin Polymerization

FERREIRA, M. L.; DAMIANI, D. E.

MACROMOLECULAR CHEMISTRY AND PHYSICS

WILEY-V C H VERLAG GMBH

Año: 2001 vol. 202 p. 694 - 700

1022-1352

The central purpose of this work is to developan efficient way to attach the metallocene to a supportwithout diminishing its catalytic activity. This articledescribes several methods to prepare supportedEtInd2ZrCl2 (EBI) on MAO/SiO2 , varying the washingstep durations and washing step temperatures. The bestmethod is the one that supports 0.7% Zr on MAO/SiO2with a final content of Al near 5.8%. It seems that thismethod combines high efficiency in MAO usage at thepreparation step and high activity in propylene polymerization.The activity of the supported catalysts EBI/MAO/SiO2 decreases to the third of the soluble catalyst EBI/MAO with the same Al/Zr molar ratio. Zr contents higherthan 0.7% produce catalysts with lower productivities.Probably, a MAO coverage on SiO2 that is higher than amonolayer is not useful in order to stabilize the zirconoceneon the MAO/SiO2 support. This paper reports thekinetics of the supported catalysts and a discussion aboutthe shape of the curves and the stability of the catalysts isappended. The molecular weight of poly(propylene)obtained with supported catalyst increases, especially forthe best preparation, comparing it with material obtainedwith 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/SiO2 and the activity of the supported catalyst is improved.