An IR-Spectroscopic Study of the State of Zirconium in Supported Zirconocene Catalysts

The surface compounds of zirconium in SiO2/MAO/Cp2ZrMe2 (I) and SiO2/Cp2ZrMe2 (II) catalysts were studied by the IR spectroscopy of adsorbed CO at 93-293 K. It was found that the bridging and terminal complexes of CO were formed on the surface of the catalysts at 93 K; the adsorption of CO was reversible. At 293 K, CO was irreversibly inserted into the Zr-Me bond with the formation of various acyl compounds of zirconium; these compounds were characterized by absorption bands in the region 1495-1750 cm-1 in the IR spectrum. These data suggested the heterogeneity of the surface composition of zirconocene catalysts Iand II. Catalyst I, which was active in ethylene polymerization, contained surface zirconium complexes that can be considered as the precursors of active centers for ethylene polymerization.