| 摘要 |
A highly active catalyst for polymerizing ethylene to polyethylene and copolymers of ethylene with alpha-olefins having a narrow molecular weight distribution, a method of making the catalyst and a method of polymerizing in which the catalyst is prepared by forming a mixture of a porous support of silica, alumina, zirconia, thoria or mixtures and a chromium compound and an alkyl ester of boron containing 1-7 carbon atoms in the alkyl group or a halide of boron capable of reacting with the chromium compound and activating this mixture at an elevated temperature in a fluidized bed with a substantially dry reducing gas followed by fluidizing with an oxidizing gas at an elevated temperature.
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