KINETIC INVESTIGATION OF THE ACTIVE-SITES PRECURSORS ON MGCL2-SUPPORTED ZIEGLER CATALYST THROUGH INTERACTION WITH A LEWIS BASE

The initial polymerization stage of propene with a MgCl2-supported Zie gler catalyst after the pre-treatment with a Lewis base was examined a s a study of the stereospecificity of the active sites precursors. A d rastic depressing effect on the catalyst activity occurs, accompanied by an increase in stereospecificity, by the direct interaction of cycl ohexylmethyldimethoxysilane (CMDMS) with the catalyst before the polym erization. The kinetic study of the polymerization indicated that the active sites concentration ([C]) decreases drastically by the catalys t pre-treatment with CMDMS. On the other hand, the increase of propaga tion rate constant (k(p)) is relatively small and corresponds to the m oderate increase of the mmmm pentad fraction. This is an indication th at the interaction of the Lewis base with the active sites precursors prevents formation of the active sites and that inhibition occurs pref erentially at the aspecific precursor.