Effective activation of metallocene catalyst with AlMCM-41 in propylene polymerization

AlMCM-41 was prepared by a post-synthesis alumination of MCM-41 and applied to propylene polymerization with rac-ethylene(bisindenyl)zirconium dichloride and triisobutylaluminium. The resulting catalyst system gave selectively isotactic polypropylene and the polymer yield was strongly dependent upon the evacuation temperature in the pretreatment of the AlMCM-41 before use. From the linear relationship between the polymer yield and the number of Lewis acid sites on the AlMCM-41 evaluated by pyridine adsorption, it was found that Lewis acid sites on AlMCM-41 are able to activate effectively the metallocene compound, resulting in the formation of active species.