Chromium oxide catalysts for the polymerization of ethylene

Summary

• 1. The activity of the catalyst depends on the relative amounts of Cr^VI and Cr^III and on the extent of the dehydration of the aluminum silicate. The deactivation of the catalyst is due to the more complete removal of active oxygen occurring either at too high a temperature or when the supply of air is inadequate.

• 2. In the course of the thermal treatment of the catalyst aluminum oxide enters into chemical reaction with CrO₃, and this retards the reduction of Cr^VI to Cr¹¹¹. No interaction is observed between silicon oxide and CrO₃.

• 3. The activation of the catalyst at high temperatures is necessary only for the dehydration of the aluminum silicate, as the maximum amount of Cr^VI is present before the heating and the interaction between Cr compounds and alumina starts at low temperatures (103–108°).

• 4. The chromium catalyst investigated has high sorptive power and is readily reduced to Cr111 under the action of high temperature and hydrocarbons.

• 5. Spent catalysts can be regenerated.