METODO PER LA PREPARAZIONE DI UN CATALIZZATORE A BASE DI ZIRCONIO O AFNIO E PROCESSO DI POLIMERIZZAZIONE O COPOLIMERIZZAZIONE DI COMPOSTI INSATURI IMPIEGANTE LO STESSO

A catalyst comprising zirconium and/or hafnium is prepared by the following steps: (a) vaporization in vacuo of magnesium and reaction of the thus obtained vapour with a compound of quadrivalent titanium in the presence of a halogen donor and of a compound of zirconium and/or hafnium; (b) thermal treatment of a mixture comprising an alcohol of the formula ROH, wherein R is an aliphatic, linear or branched chain, containing from 1 to 10 carbon atoms, optionally substituted by one or more aromatic groups, and the solution prepared in step (a); (c) thermal treatment of a mixture comprising an organometallic aluminium compound of the formula AIR'3-yXy wherein R' is a hydrocarbon radical, X is a halogen atom and y is a number of from 0 to 2 inclusive, such that 1