PHILLIPS-TYPE POLYMERIZATION CATALYSTS - KINETIC-BEHAVIOR AND ACTIVE-CENTER DETERMINATION

The kinetic behaviour of a Phillips-type catalyst in the presence of aluminium alkyls has been studied as a function of ethylene pressure in the range 1-11 atm. The results highlight the importance of catalyst fragmentation, which is further substantiated by morphological electron microscopic studies. Active centre concentration studies have been carried out using a (CO)-C-14 radio-labelling technique which enabled values of active propagating centres and rate coefficients to be obtained, both of which were found to depend on the ethylene pressure. Only a small percentage of the chromium (3.2-7.3%) is found to be involved in active centres. These results provide valuable information concerning the factors controlling ethylene polymerization by this type of catalyst.