Analysis of heterogenized zirconocene catalysts using a micro-PIXE technique

Et(Ind)2ZrCl2 and MAO co-catalyst, which polymerize ethylene and propylene, were heterogenized on partially dehydroxylated Davison silica 955, following the method of equilibrium adsorption. The dispersion of these catalyst components on the silica support was investigated by measuring the spatial concentration profiles of Si, Al, and Zr using a micro-PIXE technique. These components were found to be uniformly distributed over the support irrespective of the variation in the heterogenization procedures and the experimental conditions used. The Si∶Al ratios determined by the micro-PIXE technique were similar to those measured by the spectrophotometric method. However, the Al∶Zr ratios measured by the former were somewhat lower than those determined by the latter. Micro-PIXE measurements confirmed the presence of several trace impurities such as K, Ca, Ti, Fe, Ni, Cu, and Zn which may potentially poison the resulting catalyst.