Analytical and kinetic approaches for the basic type of MgCl2‐supported high yield catalysts

Thermal analysis in combination with infrared spectroscopy was applied to investigate the states of ethylbenzoate (EB) and TiCl4 in the simple type of the MgCl2‐supported high‐yield catalysts. A further attempt was made to evaluate kinetic parameters in the initial stage of propylene polymerization (< 1s) by a stopped flow method. The catalysts employed in the present study were prepared by co‐grinding MgCl2 and TiCl4 · EB complex. Thermal analysis and infrared spectroscopy showed that TiCl4 · EB complex decomposes during co‐grinding process. It was also indicated that EB, thus produced, has strong interaction with MgCl2. This was consistent with observations made by infrared spectroscopy. It was deduced that EB and TiCl4 are supported at separate sites of MgCl2 in the co‐ground catalyst. Kinetic parameters including rate constants of propagation (kp) and transfer (ktr), and concentration of polymerization centers ([C*]) were determined. The values of kp and ktr remained almost constant throughout the range of co‐grinding time, but [C*] increased with time of co‐grinding. No significant changes in the value of ktr were observed. Accordingly, the improvement of catalyst activity was attributed to an increase in [C*] rather than kp. These results lead to the conclusion that the complex decomposes during the co‐grinding to yield EB and TiCl4 which interact only with MgCl2.