| Abstract: | The polymerization of ethylene was studied with supported catalysts prepared by the reaction of Zr(benzyl)4 and Al2O3. The influence of the preparation of the catalysts and the reaction conditions on the overall rate of the polymerization was established. The rate exhibits a maximum which depends on the thermal pretreatment of the support and the quantity of the fixed Zr(benzyl)4. The concentration of the active centres of the catalysts was determined by quenching the polymerization with labelled butanol. The catalysts possess active centres which have different rates of propagation for ethylene. The decrease of the polymerization rate is caused by chemical reaction. The higher the concentration of free hydroxyl groups on the catalyst, the higher the rate of deactivation. Hydrogen in the monomer feed produces a decrease or an increase of the polymerization rate depending on the preparation of the catalysts. |
