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

Abstract

Abstract The main kinetic behavior of the slurry polymerization of propene with a MgCl 2 ‐supported TiCl 4 /C 6 H 5 COOC 2 H 5 catalyst, activated by Al(C 2 H 5 ) 3 , was studied, Examination of the dependence of the polymerization rate on temperature and concentrations of Al(C 2 H 5 ) 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(C 2 H 5 ) 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(C 2 H 5 ) 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, K p , during the second order rate decay. The observed polymerization kinetics strongly suggest the existence of two kinds of polymerization centers (isotactic and atactic).