SYNOPSISA kinetic modeling study was conducted for the Ziegler-Natta polymerization of butadiene with cobalt octoate/DEAC/water catalyst. The model equations for the single and dual active site models were analytically solved, and the closed-form expressions for conversion and both number and weight average molecular weights were obtained. The expressions for conversion and number average molecular weight are identical for both models. Also, the expressions of weight average molecular weight are similar for both models, but the expression for the dual active site model includes an additional scalar parameter. The parameter can be regarded as a "correction factor of weight average molecular weight," which reflects the effect of dual active sites on the polydispersity. Using the expressions, a simple and noniterative kinetic modeling algorithm was established, and the parameter estimates were obtained. The estimated value of the correction factor ranges from 1.2 to 1.5 depending on the experimental data. The modeling results indicate the validity of the dual active site model.

SYNOPSISThe reaction mechanism and subsequent kinetics for polymerization of butadiene using cobalt-based Ziegler-Natta catalysts have been investigated by many researchers. Kinetic models developed from these investigations can be used to predict the monomer conversion quite accurately; however, it is difficult to develop models that accurately predict the molecular weight as a function of time or conversion. In this paper, an attempt is made to model the reaction mechanism for the polymerization of butadiene using the cobalt octoatel diethyl aluminum chloride/water catalyst system with data taken from the literature. A dual active site mechanism is proposed and incorporated in a kinetic model. In this case, all reaction steps except the formation of byproducts step have two rate constants. The simulation results predict the molecular weight as a function of conversion and time better than results from previously published models.