Ethylalumoxanes and ethylchloroalumoxanes as components of catalyst for propylene polymerization

Ethylalumoxanes and ethylchloroalumoxanes as components of Ziegler‐Natta catalysts for polymerization of propylene have been studied. The influence of the degree of hydrolysis of triethyl aluminium [(Et 3 Al) and diethylaluminium chlorilp (Et 2 AlCl) 2 ] in the range 0.5–1.5:1 on the activity and the stereospecificity of the catalytic systems was determined (the degree of hydrolysis is defined as the molar ratio H 2 O/organoaluminium compound). It was found that the activity of the catalytic system ethylalumoxane‐ TiCl 4 is a little higher than the activity of the Et 2 AlCl‐TiCl 4 system. The ethylchloroalumoxane‐TiCl 4 system is about six times more active than the classical Ziegler‐Natta system. Our studies showed that alumoxanes react with TiCl 4 as follows: (a) to form compounds of the AlOTiCl 3 type; (b) to exchange alkyl groups for chlorine; (c) to form donor‐acceptor complexes. Reactions of types (b) and (c) occur mainly in the cases of alumoxanes of low degree of hydrolysis (0.5–0.7). In cases of alumoxanes of a degree of hydrolysis equal to 0.7–1.0, reactions of all three types occur, and for alumoxanes of degree of hydrolysis >1.0 reactions of types (a) and (c) are preferred.