Ethylene polymerization using supported vanadium catalyst

Claim 1

A process for producing ethylene polymers which comprises polymerizing ethylene with or without at least one C 3 to C 10 alpha-olefin monomer in the gas phase at a temperature between about 10° C. to about 115° C., by contacting the monomers with a catalyst composition comprising: (A) a supported precursor consisting essentially of a vanadium compound and modifier impregnated on a solid, inert carrier, said carrier consisting essentially of silica or alumina and being free of preparative chemical treatment with an alkylaluminum compound prior to formation of the supported precursor, said supported precursor composition being prepared by impregnating said carrier first with the vanadium compound and subsequently with the modifier, (1) said vanadium compound being the reaction product of: (a) a vanadium trihalide of chlorine, bromine or iodine; and (b) an electron donor which is a liquid, organic Lewis base in which said vanadium trihalide is soluble, said electron donor being selected from the group consisting of alkyl esters of aliphatic and a romatic carboxylic acids, aliphatic ketones, aliphatic amines, alkyl and cycloalkyl ethers, and mixtures thereof; and (2) said modifier having the formula: MX.sub.a wherein: M is AlR.sub.(3-a) and wherein each R is independently alkyl, provided that the total number of aliphatic carbon atoms in any one R group may not exceed 14; X is chlorine, bromine or iodine; and a is 1 or 2; and said modifier being employed in an amount of from 0.2 to 2.5 moles per mole of electron donor present in said vanadium compound; (B) a cocatalyst having the formula: AlR.sub.3 wherein R is as previously defined; and (C) a promoter having the formula: R'.sub.b CX'.sub.(4-b) wherein: R' is hydrogen or unsubstituted or halosubstituted lower alkyl; X' is halogen; and b is 0, 1 or 2.