Effect of a Lewis Acid additive on active sites formation in zirconocene catalyst systems: A DFT study

Article

Authorship

BELELLI, PATRICIA GABRIELA ; Damiani, Daniel Eduardo ; Castellani, Norberto Jorge

Date

2004

Publishing House and Editing Place

Elsevier Science

Magazine

JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, vol. 208 (pp. 147-158) Elsevier Science

Summary Information provided by the agent in SIGEVA

Comparative theoretical analysis of optimized geometries and electronic structures of Cp2ZrCl2/methylaluminoxane (MAO) system and its interactions with a third component was performed. The additive studied was a Lewis acid compound: AlCl3. Density functional theory (DFT), that included exchange and correlation effects, was employed with Gaussian basis sets. Additive enhances the cocatalyst Lewis acid character and, indirectly, it modifies the electrophilicity of Zr atom. By comparing the geomet... Comparative theoretical analysis of optimized geometries and electronic structures of Cp2ZrCl2/methylaluminoxane (MAO) system and its interactions with a third component was performed. The additive studied was a Lewis acid compound: AlCl3. Density functional theory (DFT), that included exchange and correlation effects, was employed with Gaussian basis sets. Additive enhances the cocatalyst Lewis acid character and, indirectly, it modifies the electrophilicity of Zr atom. By comparing the geometrical structure and charge distribution of the site with and without AlCl3 it is possible to understand the reasons of polymerization performance improvement. Previous experimental results for these systems have showed a notable increase in ethylene and propylene polymerization activity. © 2003 Elsevier B.V. All rights reserved.