High-activity catalyst for use in production of polyethylene

The present invention relates to a high activity catalyst composition for the (co-)polymerisation of ethylene, optionally with an alpha olefin of 3 to 10 carbon atoms, comprising a catalyst precursor and an organoaluminium cocatalyst, wherein the catalyst precursor consists of: (i) a silica carrier material, having from 0.3 to 1.2 mmoles of OH groups per gram of silica, (ii) a dialkylmagnesium compound of the formula RMgR1, where R and R1 are the same or different C2-C12 alkyl groups, in an amount comprised between 0.5 to 1.5 mmoles of dialkylmagnesium per gram of silica, (iii) a tetraalkyl orthosilicate, in which the alkyl groups contain from 2 to 6 carbon atoms, in an amount comprised between 0.2 to 0.8 mmoles per gram of silica, (iv) a chlorinated compound (X) having the formula RnSiCl4-n, wherein each R is the same or different and is hydrogen or an alkyl group and n is an integer from 0 to 3, in an amount comprised between 0.2 to 4 mmoles of X per gram of silica, and (v) a titanium compound in an amount comprised between 0.3 to 1.5 mmoles per gram of silica.