Lower valent titanium-aluminum halides

Unsaturated hydrocarbons, e.g. ethylene and propylene, are polymerized in the presence of a Ziegler/NaHa catalyst containing aluminium halide and a lower halide of titanium; this halide material is made by reaction between aluminium and titanium tetrahalide in the presence of free halogen (see Division C1). The catalyst also contains an organo-metallic compound, e.g. metal alkyl or aryl or metal alkyl halide, the metal being of groups I-III of the Periodic Table, e.g. A1.ALSO:Material containing aluminium halide and a lower halide of titanium is made by reducing a titanium tetrahalide with aluminium in the presence of free halogen. The stoichiometric ratio of titanium tetrahalide to aluminium is at least unity; 1-50 moles halogen per 100 moles titanium tetrahalide are employed. Liquid diluent, e.g. aromatic hydrocarbons or chlorinated hydrocarbons, may be present, or excess of titanium tetrahlide, if liquid, may be used as reaction medium. The reaction, which commences at ambient temperature, is performed under reflux, preferably in an inert atmosphere, e.g. Ar or N2. A slurry is obtained, from which a solid is recovered, e.g. by filtration or distillation. The halogen, preferably sufficient only to initiate the reaction, may be added to the liquid before or after the aluminium. Further liquid may be added after the initial reaction. The aluminium is preferably finely divided: e.g. 0.5 m diameter particles. The material may be used as a nucleating agent in vapour phase oxidation of TiCl4 to form TiO2. For use as Ziegler/Natta catalyst, the dry product may be milled either dry or in liquid vehicle, e.g. the polymerization medium (see Division C3).