Catalyst precursor particles, their preparation and use

Abstract

A method for preparing a catalyst precursor for an olefin polymerization catalyst involves the use of aqueous or alcoholic solutions of a chromium salt and of boric acid and aluminum carboxylate for deposition onto an inorganic support material, such as a silica xerogel. The chromium salt, aluminum carboxylate and boric acid are sufficiently soluble for deposition from a single solution to be effective. The catalyst precursor can be activated by calcination to form a catalyst for homo- or co-polymerisation of α-olefins which has productivity and melt flow index for the resulting polymer or copolymer which is comparable to results obtained with catalysts prepared by prior art organometallic routes. The activation of the catalyst precursor gives reduced levels of toxic or noxious fumes during activation compared to use of organometallic sources of chromium or aluminum.