REVERSIBLE AND IRREVERSIBLE DEACTIVATION OF PROPENE POLYMERIZATION USING HOMOGENEOUS CP2ZRCL2 METHYLALUMINOXANE ZIEGLER-NATTA CATALYSTS

The kinetics of propene polymerization in the presence of homogeneous Cp2ZrCl2/methylaluminoxane catalysts in toluene at 2 bar have been investigated at 0, 20, 40 and 60-degrees-C. The narrow polypropylene molecular weight distributions, M(w)/M(n) < 2.4, indicate the presence of uniform catalytically active sites (C star). By assuming the existence of a reversible followed by an irreversible reaction, both of second order, which lead to formation of the catalytically inactive complexes I1 and I2, respectively, we propose the kinetic scheme 2 C star reversible I1 --> I2 to predict the decay of the polymerization rate as a function of time. At low temperatures there is predominantly reversible deactivation.