CATALYST COMPOSITION FOR USE IN THE POLYMERIZATION AND COPOLYMERIZATION OF ETHYLENE

摘要

An ethylene polymerization catalyst comprising two tran- sition metal components on a support with one of the two tran- sition metals in the form of a metallocene. An aluminum alkyl activator for the non-metallocene transition metal component is also present. The support is an anhydrous material prepared by reacting (i) a silanol-containing silica impregnated with a mag- nesium alkyl with (ii) an alcohol. The catalyst produces ethylene copolymer in a single reactor with a bimodal molecular weight distribution. The polymerization is practiced in a reactor (10) comprising a reaction zone (12), a velocity reduction zone (14) and a distributor plate (20). The reaction zone (12) comprises a bed of growing polymer particles and a minor amount of cata- lyst particles fluidized by the continuous flow of polymerizable and modifying gaseous components. The distribution plate dif- fuses the recycle gas. The recycle gas is separated in the cy- clone separator (22) from the catalyst particles, passes through the cooler (24), and is further compressed in compressor (25), passes through a heat exchanger (26), combines with a fresh feed and enters the reaction zone (12) through the distributor plate (20). When a desirable degree of polymerization has been ac- complished the polymer particles with bimodal molecular weight distribution are recovered from the reactor.