Nano-Sized Silica Supported Me2Si(Ind)2ZrCl2/MAO Catalyst for Ethylene Polymerization

Nano-sized and micro-sized silica particles were used to support a zirconocene catalyst [racemic-dimethylsilbis(1-indenyl)zirconium dichloride], with methylaluminoxane as a cocatalyst. The resulting catalyst was used to catalyze the polymerization of ethylene in the temperature range of 40-70 degrees C. Polyethylene samples produced were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). Nano-sized catalyst exhibited better ethylene polymerization activity than micro-sized catalyst. At the optimum temperature of 60 degrees C, nano-sized catalyst's activity was two times the micro-sized catalyst's activity. Polymers obtained with nano-sized catalyst had higher molecular weight (based on GPC measurements) and higher crystallinity (based on XRD and DSC measurements) than those obtained with micro-sized catalyst. The better performances of nano-sized catalyst were attributed to its large external surface area and its absence of internal diffusion resistance. SEM indicated that polymer morphology contained discrete tiny particles with thin long fiberous interlamellar links. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 1169-1175, 2012