| Abstrakt: |
In order to reveal the formation mechanism of the active species in ethylene polymerization, the reduction of three kinds of molybdenum oxides, I, II, and III, which are insoluble in aq 10 M-NH3, soluble in aq NH3but insoluble in water, and soluble in water respectively, was studied under a hydrogen pressure of 170 Torr over the temperature range 350–450 °C. The reduction rate of oxides I and II followed Elovich kinetics with a variable activation energy which increased with the progress of reduction, while that of III followed Elovich kinetics in the multiple kinetic stages and the minimum in apparent activation energy for the reduction lies at the reduction extent of MoO2.7-2.6. The final states of reduction of I, II, and III were MoO2.8-2.6, MoO2.0and MoO2.2-2.1, respectively. The amount of Mo(V) in each oxide was determined by ESR measurements. The results indicate that Mo(V) in the II is related to the decrease of the apparent activation energy on reduction of III through their mutual interaction. A formation mechanism of the active species, Mo(V) in III, was proposed. |
