Use of alkylaluminum compounds and hydroxyl-containing compounds to initiate polymerization of ethylene with chromium oxide catalysts

A method for smoothly and reliably initiating polymerization of ethylene with a supported chromium oxide catalyst, with smaller amounts of catalyst and in substantially shorter periods of time then heretofore required, by adding an alkylaluminum compound and a hydroxyl-containing compound to the reactor of a polymerization reaction system prior to the commencement of polymerization and subjecting said alkylaluminum compound and hydroxyl-containing compound to suitable conditions of temperature and pressure for a time sufficient for said alkylaluminum compound to react completely with the moisture present in said reactor and said hydroxyl-containing compound.