The kinetics and mechanism of the polymerization of α-olefins in the presence of complex catalysts

Abstract

As was shown in previous work [1] during the polymerization of ethylene in the presence of titanium tetrachloride and tri-ethyl-aluminium, a sharp fall in the rate of polymerization with time is observed and is connected with a conversion which is taking place in the catalyst itself. The components of the catalyst react so readily with each other, that even a considerable reduction of the temperature (from 70 to 56°) does not succeed in slowing down the process of conversion of the catalyst to the less active form, and in stabilizing the catalytic system at a high level of activity. Because of the rapid interaction of TiCl 4 and Al(C 2H 5) 3 it is experimentally difficult to establish how the utilization and dissociation of the most active catalytic complex takes place and what the activity of the system is at the zero moment of time, when the composition of the catalyst must consist only of TiCl 4 and Al(C 2H 5) 3. As a result of the supposition, that the decrease of the catalytic activity of the system with time, is, in the first place, connected with a strong reduction of titanium we chose, for the subsequent investigations, di-iso-butyl-aluminium chloride, the reducing properties of which are less than those of tri-ethyl-aluminium [2]. A study of the kinetics of the polymerization of ethylene in the presence of TiCl 4+Al( iso-C 4H 9) 2Cl was carried out ethylene pressures from 50 to 250 mm, with ratios of Al( iso-C 4H 9) 2Cl: TiCl 4 from 0.69: 1 to 3.3:1, at intervals of temperature from 30 to 70°, in a medium of heptane.