Polymerization of propylene with γ‐Al₂O₃‐ or SiO₂‐supported titanium tetrachloride catalyst

Abstract

Abstract The preparation of γ‐Al 2 O 3 ‐ and SiO 2 ‐supported titanium tetrachloride catalysts for the polymerization of propylene is described. The ESR spectra of these products, measured at −196°C, display broad signals with g ‐values of 1,942 and 1,952 in the cases of γ‐Al 2 O 3 and SiO 2 , respectively, which are assignable to Ti(III) species. The concentration of the Ti(III) species depends strongly upon the conditions of treatment. With these products as catalysts the polymerization of propylene takes place at 40 −75°C in the absence of any activator. The polymerization activity significantly depends upon the conditions of catalyst treatment, but it is approximately proportional to the concentration of the Ti(III) species. The molecular weight and the isotacticity of the resulting polymer remain almost unchanged. These results lead to the conclusion that Ti(III) is the active species in these catalysts.