Role of Titanium in Ti/SiO2-Supported Metallocene-based Olefin Polymerization Catalysts. Part 2: Particle Fragmentation

Abstract

A commercial SiO2 modified by the addition of a TiO2 layer on its surface and pore walls offers a support for metallocene-based ethylene polymerization catalysts with a 35 % improved catalytic activity. The effect of such support modification on the catalyst particle fragmentation during polymerization reactions were assessed. This was performed by exposing the internal cross-section of several SiO2 and Ti/SiO2-based metallocene catalyst particles, polymerized at a wide range of reaction conditions, with a Focused-Ion Beam Scanning Electron Microscope (FIB-SEM), followed by a semi-quantitative analysis of polymer, catalyst and macropores of each 2D image obtained. The titanation of the SiO2 lead to a support framework that fractures earlier and more efficiently. This was evidenced by the presence of several empty (polymer-free) cracks along the support dense-shell, found more extensively in the Ti-modified polymerized catalyst particle, which also resulted in a more sustained polymerized particles macroporosity during the course of the reaction.