Supported metallocene polymerization catalysis

Zirconocene supported on alumina or magnesium chloride exhibits modest olefin polymerization activity but not when it is supported directly on silica. The surface silanol as well as siloxane groups must be passivated with appropriate reagents. A very active and stereospecific supported catalyst was obtained by first reacting silica with methylalumoxane and bisphenol A before the impregnation of the ansa-zirconocene precursor. The main difference between a homogeneous and supported catalyst is that at the same gross amount of metallocene, the net concentration of it in the pores of a support material is several orders of magnitude greater than it exists in solution thus the rate of deactivation in the former case is correspondingly faster than in the latter. Most other supported metallocene catalysts based on supports such as zeolites, cyclodextrin, polymeric MAO, synthetic polymers, etc., are poor in olefin polymerization for this and other reasons discussed.