Polymerization of olefins in the presence of Ziegler-Natta catalysts containing COCl3

The reasons for the Low activity of vanadium-based Ziegler-Natta catalysts in the polymerization of ethylene have been discussed. A very easy and rapid reduction of vanadium(IV) as well as vanadium(III) to the inactive vanadium(II) form by an organoaluminum cocatalyst in the VOCl3/Et(2)AlCl system was confirmed. Deactivation of active sites was found to increase as the catalyst aging time and polymerization temperature are increased. Deposition of the relatively unstable vanadium catalyst on a MgCl2(THF)(2) support resulted in stabilized vanadium active sites because of suppressed reduction to the inactive state of lower valency. Optimum conditions were established for of the synthesis of a high-activity and high-stability supported vanadium catalyst. This catalyst system produced PE-UHMW. The specific role of MgCl2(THF)(2) as a carrier of Ziegler-Natta type catalysts was discussed in terms of catalytic properties of various titanium and vanadium systems.