Novel SiO₂‐Supported Chromium Oxide(Cr)/Vanadium Oxide(V) Bimetallic Catalysts for Production of Bimodal Polyethylene

Abstract

Novel SiO 2 -supported Cr-V bimetallic oxides catalysts, which were capable of one-pot synthesizing polyethylene with bimodal molecular weight distribution, had been successfully developed. These catalysts were prepared with a simple introduction of vanadium oxide onto the traditional Phillips CrO x /SiO 2 catalyst. The polymerization activity over the Cr-V bimetallic catalysts was significantly improved compared with the V-free Phillips CrO x /SiO 2 catalyst. Moreover, the bimodal ethylene/1-hexene copolymer prepared by the novel catalyst showed a better short chain branch distribution with more 1-hexene comonomer inserted into the PE chains with high molecular weight, which would be favorable for the long term mechanical properties of the bimodal PE as potential high grade pipe materials.

Vanadium Modification Effects on the (SiO2/MgO/MgCl2)•TiClxZiegler-Natta Polyethylene Catalyst

“…In the recent research, our group introduced vanadium active species into the chromium-based catalysts and successfully developed three series of novel Cr -V bimetallic catalysts: (1) SiO 2 -supported silyl-chromate(Cr)/ vanadium-oxide(V) bimetallic catalyst; (2) SiO 2 -supported silyl-chromate(Cr)/imido-vanadium(V) bimetallic catalyst; and (3) SiO 2 -supported chromium oxide(Cr)/ vanadium oxide(V) bimetallic catalyst. [21][22][23] Compared with the traditional industrial Cr-based catalysts (UCC S-2 catalyst and Phillips catalyst), these novel Cr -V bimetallic catalysts showed higher activity, better 1-hexene incorporation ability, and produced bimodal MWD polyethylene with better short chain branch distribution (SCBD) through synergistic effect between the chromium and vanadium species. More recently, we developed another novel catalyst through the introduction of chromium species into the (SiO 2 /MgO/MgCl 2 )·TiCl x ZN catalyst, and this Cr-modifi ed ZN catalyst presented better catalytic properties with 13% higher activity, 40% higher hydrogen response, and 20% higher 1-hexene incorporation ability with better SCBD.…”

A Novel SiO2‐Supported Fluorine Modified Chromium–Vanadium Bimetallic Catalyst for Ethylene Polymerization and Ethylene/1‐Hexene Copolymerization

“…A series of fluorine modified Cr–V bimetallic catalysts, Cr–V bimetallic catalysts, and fluorine modified Phillips catalysts was prepared by coimpregnation or two‐step impregnation method. The chromium loading was 1.0 wt% and the Cr/V molar ratio was 2:1 …”

“…However, the loading of fluorine accelerates the sintering of supports at high activation temperature, and the ESCR properties of the obtained copolymers are inadequate resulting from the imperfect SCBD. As the active component of classic vanadium–magnesium catalysts, vanadium was introduced to some traditional catalysts to take advantage of its higher 1‐hexene incorporation ability in the ethylene/1‐hexene copolymerization . A series of vanadium‐modified Phillips catalysts were prepared by Matta et al through coimpregnation procedures for enhancing the branching ability of Phillips catalyst in ethylene polymerization .…”

“…As the active component of classic vanadium–magnesium catalysts, vanadium was introduced to some traditional catalysts to take advantage of its higher 1‐hexene incorporation ability in the ethylene/1‐hexene copolymerization . A series of vanadium‐modified Phillips catalysts were prepared by Matta et al through coimpregnation procedures for enhancing the branching ability of Phillips catalyst in ethylene polymerization . Cheng et al successfully developed the novel chromium–vanadium (Cr–V) bimetallic catalysts with vanadium oxide onto the Phillips catalyst to significantly enhance the activity .…”

Polymer Reaction Engineering in China

“…[8] Prof. Boping Liu developed a novel SiO 2 -supported chromium/vanadium bimetallic catalyst for bimodal polyethylene. [9] Dr. Wen-Hua Sun of Institute of Chemistry of the Chinese Academy of Science investigated the performance of a cobalt catalyst in ethylene polymerization. [10] Prof. Qinmin Pan of Suzhou University presented a novel method for polybutadiene degradation and diene-based telechelic oligomer synthesis through olefin cross metathesis.…”