Effects of Spatial Distributions of Active Sites in a Silica-Supported Metallocene Catalyst on Particle Fragmentation and Reaction in Gas-Phase Ethylene Polymerization

This work presents the experimental investigation ofthe effects of intraparticle catalyst site distribution on the catalystparticle fragmentation in gas-phase ethylene polymerization over asilica-supported metallocene catalyst (rac-dimethylsilylbis(2-meth-yl-4-phenylindenyl)-dimethyl zirconium) with methylaluminoxane(MAO) as a cocatalyst. The supported catalysts with differentspatial distributions of Al and Zr were prepared by varying thecatalyst immobilization conditions, and the catalyst metaldistributions were analyzed using the focused ion beam (FIB)and scanning electron microscopy-energy-dispersive spectroscopy(SEM-EDX) techniques. The experimental data showed thatimpregnation time and catalyst solution concentration had strongeffects on the radial distributions of Zr in silica particles andfinesformation during the gas-phase polymerization of ethylene. The supported catalyst with a high Zr concentration near the exteriorregion of a catalyst particle generated morefines than a supported catalyst with uniformly distributed Zr during the gas-phasepolymerization, suggesting that the optimal distribution of catalyst sites needs to be considered in designing the silica-supportedcatalyst for improved control of polymer particle morphology

Automated summary

This research investigates the effects of intraparticle catalyst site distribution on the fragmentation of catalyst particles in gas-phase ethylene polymerization. The experimental results show that the impregnation time and catalyst solution concentration strongly influence the distribution of Zr in silica particles and the formation of fines during the polymerization process.