Immobilization of a zirconium complex bearing bis(phenoxyketimine) ligand on MCM-41 for ethylene polymerization

A novel zirconium complex bearing bis(phenoxyketimine) ligand (1) bis((3,5-di-tert-butyl-C6H2-2-O)PhCN(2,4-di-fluoro-C6H3))ZrCl2 (2) was prepared and successfully immobilized on a mesoporous molecular sieve MCM-41 in chemical method. Results of slurry polymerization of ethylene with MCM-41-supported catalyst (MC) indicated that the morphologies of polyethylene obtained differed greatly in heptane and toluene. Homogeneous catalyst 2 exhibited a very high initial activity in ethylene polymerization at room temperature resulting in great viscosity of the system. When immobilized on MCM-41, MC showed a smooth yet highly active kinetic behavior. With MAO as the cocatalyst, the effects of Al/Zr molar ratio and polymerization temperature on catalytic activity and properties of polyethylene obtained were investigated. The results showed that polyethylene obtained with MC possessed higher molecular weight (Mn) and broader molecular weight distribution (Mw/Mn) than those formed with its homogeneous counterpart.