Articulo Molecular Catalysis

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites areprohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright

Author's personal copy
Journal of Molecular Catalysis A: Chemical 307 (2009)98–104

Contents lists available at ScienceDirect

Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata

Novel supported catalysts for ethylene polymerization based on aluminohydride-zirconocene complexes
Rogelio Charles a,b , Rebeca González-Hernández a , Elsa Morales a , Javier Revilla b , Luis E. Elizalde a , Gregorio Cadenas a , Odilia Pérez-Camachoa,∗∗ , Scott Collins c,∗
a

Centro de Investigación en Química Aplicada, Saltillo, Coahuila, Mexico Centro de Investigación y Desarrollo Tecnológico, Lerma, Edo. de México, Mexico c Department of Polymer Science, The University of Akron, Akron, OH 44325-3909, United States
b

a r t i c l e

i n f o

a b s t r a c t
Ethylene polymerization using catalysts derived from activation ofzirconocene aluminohydride complexes, supported on silica, pretreated with methylaluminoxane (MAO), is described. The novel catalyst compositions were compared to those using conventional zirconocene dichloride complexes and characterized by SEM/EDX and DRIFT spectroscopy. Supported catalysts were prepared which featured various surface Al:Zr ratios. When using excess MAO as both activator andscavenger, the catalysts containing the most Zr per g of support gave rise to the most active formulations; the high activities in the presence of excess MAO are due, in part, to catalyst leaching prior to and/or during polymerization. When triisobutylaluminum (TIBAL) was used as scavenger, the supported catalysts that featured a higher surface Al:Zr ratio had higher activity than those prepared at thelower Al:Zr ratios. The activity of the aluminohydride complexes was significantly higher than that of the corresponding dichloride complexes, when activated by MAO while the in the presence of TIBAL, there was little difference in performance between the two catalyst precursors. © 2009 Elsevier B.V. All rights reserved.

Article history: Received 13 November 2008 Received in revised form 12January 2009 Accepted 10 March 2009 Available online 24 March 2009 Keywords: Polymerization Metallocene Supported DRIFT Aluminohydride

1. Introduction Supported catalysts based on metallocene complexes of the group 4 elements are in commercial use for the production of poly(olefins). While a wide variety of approaches to the supporting of metallocene complexes have been investigated [1], by farthe most common approach involves reaction of a metallocene dichloride with silica that has been pre-treated with methylaluminoxane (MAO) or with an alkylaluminum compound that can generate MAO on the support [2]. These chemically treated supports chemisorb significant quantities of metallocene dichloride complexes, though not all of the metal on the support is alkylated or activated for olefinpolymerization. In particular, the patent literature emphasizes the use of supported catalysts where the surface Al:Zr ratio is between 100:1

∗ Corresponding author. Tel.: +1 330 972 7259; fax: +1 330 972 5290. ∗∗ Corresponding author. E-mail addresses: odilia@ciqa.mx (O. Pérez-Camacho), collins@uakron.edu (S. Collins). 1381-1169/$ – see front matter © 2009 Elsevier B.V. All rights reserved....