CATALYST FOR THE POLYMERIZATION OF OLEFINS

CATALYST FOR THE POLYMERIZATION OF OLEFINS A solid component of catalyst, active in the polymerization of propylene and other .alpha.-olefins in stereoregular polymers, is obtained: (i) by treating a non-activated silica support in particles with a tin tetrahalide, to at least partially block the hydroxylic groups of the silica and to obtain a blocked silica; (ii) by impregnating the blocked silica with magnesium dialkyl or magnesium alkyl halide to make the magnesium compound react with the tin compound and with possible residual hydroxylic groups of the silica and to obtain a support; (iii) by halogenating the support by contact with a halogenating agent selected from the halides of tin, antimonium or silicon to obtain a halogenated support; (iv) by titanating the halogenated support with an excess of a titanium tetrahalide to obtain a titanated support; (v) by putting the titanated support in contact with a Lewis base, to obtain a solid component of catalyst.