Modeling and analysis of ethylene/norbornene copolymerization with ansa-zirconocene/methylaluminoxane catalysts in a continuous polymerization reactor

The kinetics of ethylene/norbornene copolymerization with rac-Et(1-indenyl)(2)ZrCl2 (1) and [2,2'-Me(1,3-Me2CP)(2)]ZrCl2 (2) catalysts with modified methylaluminoxane are analyzed through experimentation and theoretical modeling. These catalysts show that the rate of norbornene incorporation into the copolymer is strongly catalyst dependent. For example, while catalyst I shows a decreasing polymerization rate with an increase in the norbornene concentration, catalyst 2 shows a monotonically increasing polymerization rate with an increase in the norbornene concentration for a norbornene/ethylene mole ratio up to 50 in the bulk liquid phase. Both terminal and penultimate models are developed to describe the rate process with these catalysts. It is shown that for both catalyst systems the penultimate model yields a more accurate description of the copolymerization kinetics than the terminal model. The penultimate model has also been applied to a continuous copolymerization reactor system with catalyst 2. The copolymerization was also carried out in a continuous stirred tank reactor. The model simulation results and the experimental data of norbornene conversion, solid content, and glass transition temperature profiles obtained from a laboratory-scale continuous reactor operation have been compared. Interestingly, the model simulations show that the ethylene concentration in the bulk liquid phase is much lower than the saturated ethylene concentration, suggesting that mass-transfer resistance might be present for the ethylene gas in reaching the catalytic sites in the liquid phase.