Zeolite supported polymerization catalysts: Copolymerization of ethylene and α-olefins with metallocenes supported on HY zeolite

Abstract

Copolymerization of ethylene with higher α-olefins, such as 4-methyl-1-pentene, 1-hexene, 1-octene and 1-dodecene, was carried out with both aspecific and isospecific bridged metallocene complexes, comparing the catalytic behaviour following metallocene supportation on methylalumoxane-pretreated HY zeolite (SiO 2/Al 2O 3=5.7). A decrease in specific activity was generally observed after adsorption on zeolite of both non bridged and ansa-metallocene complexes, though molecular weights of the copolymers were found to be higher especially when employing α-olefins as polymerization solvents. On the other side, the incorporation of the α-olefin comonomer was reduced in the case of supported biscyclopentadienylzirconium dichloride, whereas similar contents of olefin units were incorporated in the copolymers prepared with soluble or supported ansa-zircono- or hafnocene. NMR analysis and DSC determined melting points of the produced copolymers are connected with a shape selectivity effect promoted by the support.