Kinetics of propylene bulk polymerization with a spherical Ziegler-Natta catalyst

Experiments were carried out in a novel laboratory reactor with an on-line monitor and a control system to study the kinetics of bulk polymerization of propylene in both gas and liquid phases. Flory-Huggins equation was used to estimate the monomer concentration in the amorphous region of the polymer. The time evolution of polymerization rate under all conditions followed the same pattern, with a fast decay in the early stage of the polymerization and a relatively slow decay in the later stage. Two nth-order decay models were developed to describe the polymerization rates. Experimental data were used to estimate the model parameters. It was found that the apparent activation energies in both phases were similar to each other, while the decay order in the liquid phase was found to be 1.7 that was lower than that in the gas phase process. It implied that less thermal runaway was achieved in the liquid process. The model described the experimental results well. © 2006 Elsevier B.V. All rights reserved.