Mesoporous Ga-MCM-41 as support for metallocene catalysts: Acidity–activity relationship

Several Ga-MCM-41 materials, prepared using different synthesis and template removal procedures, were used for the immobilisation of Cp2ZrCl2 by a direct impregnation method. Supports were carefully characterised by XRD, N2 adsorption, ICP-AES, AAS, XPS and FTIR (using pyridine as probe molecule for acid sites), in order to assess their structural features, chemical composition (bulk and surface) and surface acidity properties.Supported catalysts were tested for the polymerisation of ethylene, using methylaluminoxane (MAO) as cocatalyst/activator. The relationships established between concentration/strength of acid sites of Ga-MCM-41 and the catalytic performance of zirconocene dichloride supported in these materials demonstrate that the behaviour of the catalytic systems analysed in this paper is compatible with existing models for the interaction of single-site olefin polymerisation catalysts with other inorganic acidic oxides.

Graphical abstractA model is presented for the interactions between Cp2ZrCl2 and the acid sites present in Ga-MCM-41 materials, establishing an interpretation of the catalytic behaviour based on an acidity–activity relationship.Figure optionsDownload full-size imageDownload as PowerPoint slide