TEMPERATURE-PROGRAMMED DECOMPOSITION OF A MGCL2/THF/TICL4 BIMETALLIC COMPLEX CATALYST AND ITS EFFECT ON ETHYLENE POLYMERIZATION RATE

Abstract

A MgCl2/THF/TiCl4 bimetallic complex catalyst was prepared by reacting magnesium chloride with titanium tetrachloride in tetrahydrofuran, followed by precipitation with excess n-hexane. The products formed during the thermal treatment of the MgCl2/THF/TiCl4 bimetallic complex catalyst were THF and 1,4-dichlorobutane as identified by MS, FTIR, and C-13 NMR. The amount of 1,4-dichlorobutane formed during thermal treatment decreased with an increase of the Mg/Ti ratio. It was suggested that some of THF coordinated to Ti reacted with adjacent Cl to form 1,4-dichlorobutane. Ethylene polymerization was performed at 70-degrees-C with bimetallic complex catalysts thermally pretreated at various temperatures. When the temperature of the thermal treatment of the MgCl2/THF/TiCl4 bimetallic complex catalyst (Mg/Ti = 5.2) was below 108-degrees-C, the catalytic activity increased, while the activity decreased above 140-degrees-C. However, the catalytic activity of the MgCl2/THF/TiCl4 bimetallic complex catalyst (Mg/Ti = 16.5) heated above 80-degrees-C decreased. This indicated that the thermal stability of the catalyst decreased with an increase of the Mg/Ti ratio.