A Method for Increasing Catalyst Productivity in A Staged Metallocene Reactor System To Reduce Effects Of Hydrogen Generation
Publication Date: 2004-Dec-20
The IP.com Prior Art Database
This invention describes a method to enable the production of higher molecular weight polymers in a metallocene catalyzed staged reactor system. The production of higher molecular weight polymers is made possible by the addition of any catalyst activity increasing agent(s) to the second or subsequent reactor(s). Metallocene catalysts can become limited in the highest molecular weight achievable by producing low levels of hydrogen, a polymer chain transfer agent, during polymer chain growth. These low levels of hydrogen can limit the maximum molecular weight produced by inflating the hydrogen-to-ethylene concentration that controls molecular weight. This phenomenon becomes an even greater limitation in the first reactor of a staged reactor system, where the ethylene concentration is held low to retain catalyst activity for later reactors. By the addition of a catalyst activity enhancing agent in the second (or subsequent) reactor(s), the ethylene concentration in the first reactor can be increased. This decreases the hydrogen-to-ethylene concentration in this reactor and allows the production of higher molecular weight polymers normally not achievable in a staged reactor system.