Novel SiO₂‐Supported Silyl‐Chromate(Cr)/Imido‐Vanadium(V) Bimetallic Catalysts Producing Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular‐Weight Distribution

Abstract

Novel SiO 2 ‐supported silyl‐chromate(Cr)/imido‐vanadium(V) (Cr‐imidoV) bimetallic catalysts for ethylene and ethylene/α‐olefin polymerization are investigated. These catalysts are prepared using the residual surface hydroxyl groups in SiO 2 ‐supported imido‐vanadium catalysts to further support bis(triphenylsilyl) chromate (BC) in order to get the merits from both the SiO 2 ‐supported imido vanadium catalyst and the SiO 2 ‐supported silyl chromate S‐2 catalyst. By investigation of the polymerization behavior and the microstructures of their polymers, several vital factors such as the addition amount of imido vanadium active centers and the dosage of 1‐hexene in the ethylene homopolymerization and ethylene/1‐hexene copolymerization are systematically investigated. Compared with the traditional S‐2 catalyst and our previously reported SiO 2 ‐supported silyl‐chromate(Cr)/vanadium(V)‐oxide (Cr‐V) bimetallic catalyst, the novel Cr‐imidoV bimetallic catalysts show even higher activity and better 1‐hexene incorporation ability, together with higher molecular weight (MW) and bimodal molecular‐weight distribution (MWD). image