A supported zirconocene-methylaluminoxane catalyst for ethylene polymerization

Abstract

Slurry polymerization of ethylene over biscyclopentadienyl zirconium dichloride (Cp2ZrCl2) - trimethylaluminum (TMA) catalyst system on silica support modified with dimethyldichlorosilane (Cl2Si(CH3)2 and methylaluminoxane (MAO) was investigated to reveal the effect of aluminium/zirconium (AI/Zr) mole ratio, catalyst concentration and polymerization temperature. From the experimental results, it was found that the catalytic activity was the highest at AI/Zr mole ratio of 3000, Cp2ZrCl2 catalyst concentration of 5.0x10-5 mol/l and polymerization temperature of 60ํC. In addition, the effect of silane compounds, viz, telrachlorosilane (SiCl4). trichloromethylsilane (Cl3SiCH3), dichlorodimethylsilane (Cl2Si(CH3)2) and chlorotrimethylsilane (CISi(CH3)3) on the catalytic activity using the above polymerization conditions was studied. It was observed that the sequence of catalytic activity is SiCl4>Cl3SiCH3>Cl2Si(CH3)2>CISi(CH3)3. All polymers obtained with these catalyst systems have spherical morphology, melting temperature (Tm) in the range of 131.67-134.60ํC and narrow molecular weight distribution (MWD) between 1.41 and 1.66.