Heterogeneous Polymerization of Ethylene and 1-Hexene with Me 3 SiCp 2 ZrH 3 AlH 2 /SiO 2 Activated with MAO RebecaGonza´lez, 1 Elsa Morales, 1 MaricelaGarcı´a, 1 Javier Revilla, 2 Rogelio Charles, 2 Scott Collins, 3 Gregorio Cadenas, 1 Luis Lugo, 2 OdiliaPe´rez * 1 Summary: The aluminohydride of zirconocene Me 3 SiCp 2 ZrH 3 AlH 2 was supported on pre-treated SiO 2 , and its catalytic activity for ethylene polymerization and ethylene-1- hexene copolymerization was evaluated in order to compare with the corresponding activity of the complex in solution. As expected for systems based on metallocenes, the aluminohydride of zirconocene complex showed higher activity in solution than in suspension, however its thermal and kinetic stability was significantly increased. The effect of the co-catalyst concentration (MAO) on the activity and the molecular weight of the polymers are also reported in this study, finding that in heterogeneous phase low concentrations of MAO were used to activate the pre-catalyst. The MW of the polymers and copolymers synthesized with the supported Me 3 SiCp 2 ZrH 3 AlH 2 /SiO 2 could be controlled by adding molecular hydrogen (H 2 ) as chain transfer agent in the polymerization and copolymerization reactions. Keywords: aluminohydride of zirconocene; ethylene and 1-hexene copolymerization; H 2 effect; heterogeneous polymerization Introduction Advances in olefin polymerization using single site catalysts (SSC), based on metallocenes, have produced many grades of polyolefins with precise control of their microstructures, molecular weights (MW) and molecular weight distributions (MWD). [1] In order to be used in industrial slurry or gas phase processes, metallocene com- pounds have been heterogenized on differ- ent kinds of inorganic supports, by means of several methods reported in the litera- ture. [2] The most applied method for supporting metallocenes, involves the use of silica, previously modified with MAO (SiO 2 /MAO) according to the route sum- marized by Ribeiro et al. [2a] In previous work, we reported the use of a metallocene system based on zirconocene aluminohydride complexes, activated with the Lewis acids B(C 6 F 5 ) 3 and MAO, for ethylene polymerization in homogeneous phase. The catalytic system showed very high activities, 40–50% superior to the traditional activation method involving the corresponding zirconocene dichlorides and MAO. [3] Zirconocene aluminohydride complexes have been studied in detail since 1990 by several research groups. [4,5] They reported a dynamic association of zirconocene dihy- drides and alane (AlH 3 ) in solution, which in the case of Me 3 SiCp 2 ZrH 3 AlH 2 , led to the formation of three different aggregates that co-crystallized in the unit cell. [4b] These complexities of the aluminohy- drides of zirconocenes were considered in Macromol. Symp. 2009, 283–284, 96–102 DOI: 10.1002/masy.200950913 96 1 Centro de Investigacio ´n en Quı ´mica Aplicada, Blvd. Enrique Reyna 140 Saltillo, Coah. Me ´ xico C.P. 25253 E-mail: odilia@ciqa.mx 2 Centro de Investigacio ´ n y Desarrollo Tecnolo ´ gico, Ave. de los Sauces No. 87, Parque Industrial Lerma, Edo. de Me ´ xico, C.P. 52000 E-mail: javier.revilla@desc.com.mx 3 Department of Polymer Science, The University of Akron, Akron OH 44325-3909 Copyright ß 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim