| 摘要 |
A catalyst system for the polymerization of ethylene, comprising a particulate inorganic oxide supporting a chromium oxide being in a reduced oxidation state and a metallocene compound having the formula Cp2ZrR'R'', wherein each Cp, being equal or different, is an unsubstituted or substituted cyclopentadienyl compound, and R' and R', independent of each other, are selected from the group comprising alkyls having 1 to 6 carbon atoms, unsubstituted or substituted benzyl, and phenoxy substituted with alkyls having 1 to 6 carbon atoms; or R' or R'' may be a halide. The catalyst system is prepared by a method comprising the steps of calcining the support, joining onto the surface of the support a chronium-organic compound, subjecting the obtained catalyst precursor to oxidizing conditions to obtain the chromium in an oxidized state, reducing the oxidized chromium to obtain a main part thereof in a bivalent oxidation state, and contacting the reduced catalyst with the metallocene compound.
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