Propene polymerization with a magnesium chloride‐supported ziegler catalyst, 1. Principal kinetics

The main kinetic behavior of the slurry polymerization of propene with a MgCl2‐supported TiCl4/C6H5COOC2H5 catalyst, activated by Al(C2H5)3, was studied, Examination of the dependence of the polymerization rate on temperature and concentrations of Al(C2H5)3 and of propene resulted in a Langmuir‐Hinshelwood rate law with the number of polymerization centers dependent on time. The Polymerization rate as function of the polymerization temperature shows a maximum, which is compatible with the rate law. The analysis of the phenomenon of an optimum temperature gave 15 KJ. mol−1 and 36 KJ. Mol −1 for the activation energy of the rate determining step and the adsorption energy of Al(C2H5)3, respectively. Examination of the rapid decay of the polymerization rate showed that the main part of the decay is represented by a second order decay independent of the amount of polymer produced, which can be understood by a second order decay of surface sites by Al(C2H5)3. The number of active centers of the catalyst in gas phase polymerization was estimated applying the inhibition method with carbon monoxide. The results show a constant value for the propagation rate constant, Kp, during the second order rate decay. The observed polymerization kinetics strongly suggest the existence of two kinds of polymerization centers (isotactic and atactic).