Gas-Phase Ethylene/Hexene Copolymerization with Metallocene Catalyst in a Laboratory-Scale Reactor

Gas-phase ethylene and hexene copolymerization using a silica-supported (n-BuCp)2ZrCl2 metallocene catalyst has been investigated in a 2 L laboratory reactor. Replicate experimental runs were conducted to confirm the reproducibility of measured responses, which included polymerization rate, reactant concentrations, and copolymer properties. Comparisons of polymerization rate profiles and catalyst activity were made using a number of designed experimental runs. The experiments revealed that triisobutyl aluminum scavenger was the most important cause of low catalyst activity, and a low initial polymerization rate that was followed by a rate increase. The effects of other influencing factors, including residence time, temperature, pressure, concentration of reactants, catalyst, and cocatalyst, were also investigated. As expected, hydrogen concentration and hexene concentration had significant effects on molecular weight and shortchain branching, respectively. In addition, hexene enhanced the polymerization rate and catalyst activity, while cocatalyst and hydrogen both led to a lower polymerization rate. The results from this study provide important quantitative information that will be used for parameter estimation in fundamental models.