| 摘要 |
An ethylene polymerization catalyst comprising two transition metal components on a support with one of the two transition 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 magnesium 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 catalyst particles fluidized by the continuous flow of polymerizable and modifying gaseous components. The distribution plate diffuses the recycle gas. The recycle gas is separated in the cyclone 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 accomplished the polymer particles with bimodal molecular weight distribution are recovered from the reactor. |
