Metallocene catalyst supported on chemically modified silica for production of ethylene-propylene copolymers

In the present work Et(IndH(4))(2)ZrCl(2) was immobilized on silica previously modified with different chemical compounds, namely VOCl(3), SnCl(4), Bu(3)SnH, Me(2)SiHCl, polymethylhydrosiloxane (PMHS) and such systems were compared to methy-laluminoxane (MAO) pretreated systems. Bu(3)SnH-modified silica led to the highest zirconocene grafted content. Zr 3d(5/2) binding energy determined by X-ray spectroscopy (XPS) was shown to increase for Et(IndH(4))(2)ZrCl(2) supported on silica modified with VOCl(3), MAO and Bu(3)SnH, suggesting the generation of more electron deficient surface species. All systems were shown to be active in ethylene-propylene copolymerization, presenting higher activity than those prepared by grafting the zirconocene on bare silica. Aging test with MAO-mediated systems showed that the catalyst bearing 2.0 wt.% Al/SiO(2) kept its catalyst activity at least for 3 months after preparation. (C) 2002 Elsevier Science B.V. All rights reserved.