Ethylene polymerization over (nBuCp)2ZrCl2/MAO catalytic system supported on aluminosilicate SBA‐15 mesostructured materials

Heterogeneous metallocene catalysts were prepared by incipient wetness impregnation of AlSBA‐15 (Si/Al = 4.8, 15, 30, 60, and ∞) mesostructured materials with (nBuCp)₂ZrCl₂/MAO. For comparative purposes commercial silica and silica–alumina (Si/Al = 4.8) supports were also impregnated with the MAO/metallocene catalytic system. A combination of X‐ray powder diffraction, nitrogen adsorption–desorption isotherms at 77 K, transmission electron microscopy, ICP‐atomic emission spectroscopy, and UV–vis spectroscopic data, were used to characterize the supports and the heterogeneous catalysts. Ethylene polymerizations were carried out in a schlenk tube at 70 °C and 1.2 bar of ethylene pressure. The polyethylene obtained was characterized by GPC, DSC, and SEM. Catalysts prepared with mesostructured SBA‐15 supports exhibited better catalytic performance than those supported on amorphous silica and silica–alumina. In general, higher ethylene polymerization activity was achieved if (nBuCp)₂ ZrCl₂/MAO catalytic system was heterogenized using supports with lower pore size in the range of the mesopores and lower Si/Al ratio. All catalysts produced high‐density polyethylene, with high crystallinity values and fibrous morphology when SBA‐15 mesostructured materials were used as supports. POLYM. ENG SCI., 2008. © 2008 Society of Plastics Engineers