Abstract: There is disclosed a process for the stereoregular polymerization of alpha-olefins or mixtures thereof with ethylene, conducted in the presence of highly active and stereospecific new catalysts. The catalysts are obtained from the reaction of a particular Al-alkyl compound which is at least in part in the form of a complex and/or a substitution reaction product with an ester of an oxygenated organic or inorganic acid, with a supported component characterized by having surface area exceeding certain values or showing a particular X-rays spectrum, and obtained by contacting a Ti halogenated compound, preferably in the form of a complex with an electron-donor compound, with a support comprising a Mg or Mn bihalide.In the catalysts the ratio between the Ti compound, expressed in Ti g-atoms, and the g moles of the ester and the electron-donor compound, when present, is lower than 0.3.

Abstract: There are disclosed new starting components for use in preparing catalysts for the polymerization and copolymerization of olefins. The new starting components are compounds having the general formulae R.sub.2 AlOR" and/or RAl (OR").sub.

Abstract: Alpha-olefins C.sub.3 -C.sub.6 are polymerized stereospecifically with the aid of catalysts obtained by mixing(a) a catalyst-forming component which is an addition and/or substitution product of an electron-donor compound (or a Lewis base) with an aluminum trialkyl, or an addition product of an electron-donor compound with an alkyl aluminum compound containing two or more Al - atoms bound to each other through an oxygen or nitrogen atom with(b) a supported catalyst-forming component which is the product obtained by contacting a titanium compound, preferably in the form of an addition product with an electron donor, with a carrier which is a mixture of an active anhydrous Mg or Mn dihalide and a solid organic material which is inert to all other components of the catalyst including the Mg or Mn dihalide carrier.