Ethylene Polymerization over Metallocene Catalysts Supported on Highly Fibrous Silica Nanoparticles

The polymerization of ethylene over a metallocene catalyst supported on amorphous fibrous silica nanoparticles of 250-300 nm in diameter has been investigated. The fibrous silica nanoparticles with large surface area and open pore entrances offer minimal diffusion resistances for the catalyst immobilization onto the silica surface. These fibrous silica particles are synthesized using reverse micelles as a template to grow silica emanating outward as protrusions or platelets from a small silica core. The fibrous silica platelets are free of internal pores and the metallocene catalyst components are anchored onto the external surface of each silica platelet. With the progress of polymerization, partial fragmentation of silica platelets occurs but the main body of the fibrous silica nanoparticles remains intact and they grow into polymer particles of 3-5 mu m. Since all the active sites are present on the external surface of the silica platelets, the catalyst activity has been found to be much higher than the conventional microporous silica particlessupported catalyst with comparable surface area.