Study of the reactions between titanium tetrachloride and ethylaluminium compounds in hydrocarbon solution: III. Solid reaction products and the formantion of catalyst systems for olefin polymerization

The brown precipitate obtained at 80°C, and the purple precipitate prepared at 170°C from AlEt3 and TiCl4 at an Al/Ti ratio 1/3, both consist essentially of TiCl3 in which about one sixth of the Ti is replaced by Al and a few percent of the chlorine by ethyl. The brown precipitate gives the X‐ray diagram of β‐TiCl3, whereas the purple one gives that of γ‐TiCl3. Magnetic measurements showed that already at ambient temperature precipitates of the β‐TiCl3 structure gradually change into products with the γ‐TiCl3 structure. On treating the brown precipitates with AlEt3 they change into nearly amorphous black products with an atom ratio of chlorine to (Al + Ti) considerably lower than two. The composition and structure of the purple precipitates are much less affected by this treatment, the effect of AlEt3 being stronger than that of AlEt2Cl. It seems that the catalyst systems so obtained only polymerize propene to a highly isotactic polymer if the crystalline substrate is not more than slightly converted at its surface.