Latent metallocene catalyst systems for olefin polymerization
View Patent ↗A metallocene catalyst may be temporarily and reversibly passivated by contact with an effective amount of a passivating compound selected from the group of oxygen, oxygen-containing compounds, and nitrogen-containing compounds.
1. A method for temporarily and reversibly passivating an active metallocene catalyst system supported on a suitable carrier comprising contacting the catalyst system with a passivator selected from oxygen, oxygen-containing compounds and nitrogen-containing compounds prior to transfer to a polymerization reactor, transferring the passivated metallocene catalyst to the polymerization reactor, and reactivating the passivated metallocene catalyst system in the reactor by contact with an alkylating agent.
2. The method of claim 1 wherein said metallocene catalyst system comprises a Group 4 or Group 5 metallocene and a cocatalyst.
3. The method of claim 1 wherein said metallocene catalyst system comprises a zirconium metallocene and an aluminoxane.
4. The method of claim 1 wherein said oxygen-containing compound is selected from metal alkoxides, ethers and cyclic ethers.
5. The method of claim 1 wherein said nitrogen-containing compound is selected from alkylamines, cycloalkylamines, and metal amides.
6. The method of claim 1 wherein said passivator is oxygen.
7. The method of claim 1 wherein the activity of said catalyst system after contacting with said passivator, as determined by catalyst yield in an olefin polymerization process, is no greater than 50% of the activity of the catalyst system before contacting with said passivator.
8. The method of claim 1 wherein an active supported metallocene catalyst system comprising a zirconium metallocene and an aluminoxane and is temporarily and reversibly passivated by contacting said catalyst system with an effective amount of a passivator selected from the group consisting of oxygen, oxygen-containing compounds and nitrogen-containing compounds, said supported catalyst system after contacting with said passivator having an activity as determined by catalyst yield in an olefin polymerization process, no greater than 50% of the activity of the catalyst system before contacting with said passivator.
9. The method of claim 1 wherein the alkylating agent is a metal alkyl.
10. The method of claim 9 wherein the akylating agent is an aluminum alkyl.
11. The method of claim 9 wherein the akylating agent is trialkylaluminum.
12. The method of claim 9 wherein the akylating agent is trimethylaluminum.