The nature of the promoting effect of propylene on ethylene polymerization over supported Ziegler-Natta catalysts

The promoting effect of alpha-olefin (propylene) on polymerization of ethylene over Ziegler-Natta catalysts was investigated in a two-stage homo-and co-polymerization of ethylene and propylene, ethylene and 3-methyl-1-butene over titanium-magnesium catalysts and aluminum hydroxide-supported vanadium catalysts differing in structure and composition. With the catalysts, the enhancement effect is related to the increase in the number of ethylene active centers. This increase is related to the catalyst matrix structure and morphology of the nascent polymer and is determined by the liability of the catalyst matrix to become fragmented by the nascent polymer.