Abstract
The TiCl3 (AA)-(C2H5) nAlCl8-n (n=3, 2, 1.5) catalysts was heated at 95-155°C before polymerization and compared the activity of polymerization for propylene. Before heat treatment the activity of the catalysts was in the order of (C2H5) 3Al>(C2H5) 2AlCl>(C2H5) 1.5AlCl1.5 for aluminium components. After heat treatment at 95C° and for 60min, activity of TiCl3-(C2H5) 2AlCl and TiCl3-(C2H4) 1.5AlCl1.5 systems reached 2.3 and 3.8 times of the activity of untreated catalysts respectively, whereas TiCl3-(C2H5) 3Al system decreased the activity. During heat treatment, total concentration of alkylaluminium compounds in solution did not changed substantially, but ethyl groups of alkylaluminium compounds was gradually replaced by chlorine atoms. These results are explained by alkylation reaction of TiCl3 followed by reduction to TiCl2. The active species are suggested to be the complex of alkyltitaniumchlorides with alkylaluminium compounds.
