Distinct behaviour of Ti and Hf supported catalysts in the polymerization of different monoalkenes

MgCl2 supported Ti and Hf catalysts were comparatively tested with respect to the polymerization of differently shaped monoalkenes. The ratio between the average polymerization rates of Ti and Hf catalysts during the first 120 min (V(p)Ti/V(p)Hf) is 10 for ethylene, increases to 63 for propylene and returns to approximately 12-20 for higher or bulkier monoalkenes, suggesting a distinct shape selectivity of active sites