Hybrid silica based catalysts prepared by the encapsulation of zirconocene compound via non-hydrolytic sol-gel method for ethylene polymerization

Different hybrid silica-encapsulated metallocene catalysts were prepared by a non-hydrolytic sol-gel method and evaluated in ethylene polymerization. The employed organic groups to modify the silica network were methyl, octyl, octadecyl, vinyl, phenyl, chloropropyl, iodopropyl and glycidoxypropil and the encapsulated catalyst was bis(cyclopentadienyl)zirconiun IV chloride. The catalysts were characterized in terms of zirconium content, structure and texture via Fourier transform infrared spectroscopy, x-ray absorption spectroscopy, nitrogen porosimetry and small angle x-ray scattering and morphology by transmission electronic microscopy. The polymerzation activity results varied in the range of 1650-2850 kg PE/mol Zr.p.h, showing an increase for all the hybrid materials if compared to the non-hybrid one. Polymers characteristics such as crystallinity, melting temperature and molecular weight were shown to be affected by the nature of the organic moieties present on the catalyst support. These findings highlight the material potentiality for tuning the product characteristics depending on the organosilane present on the catalyst system.