Slurry polymerization of ethylene using bisupported Ziegler-Natta catalyst of SiO2/MgCl2(ethoxide type)/TiCl4/TEA system

Bisupported Ziegler-Natta catalyst of SiO2/MgCl2 (ethoxide type) /TiCl4 was prepared for polymerization of ethylene. SiO2 and Mg(OEt)2 were used as supports. Although MgCl2 known as best support for Ziegler-Natta catalyst, but due to high surface area and excellent morphological performance of SiO2, it was chosen as a support as well. Three catalysts of the above mentioned type were prepared using different ratios of Mg:Si and different methods of preparation of the catalyst. Triethylaluminum (TEA) was used as cocatalyst. The optimum molar ratio of Al:Ti=59.7:1 was obtained as the basis of polymer yield. Hydrogen gas was used as chain transfer agent. Increasing H2 concentration decreased the productivity of the catalyst. The effect of temperature between 40 to 70°C and the effect of monomer pressure of 1.5 to 7 bar on polymerization behaviour were studied, while the optimum ratio of Al:Ti and 25 mL/L H2 was used. Increasing temperature to 60°C increased the polymer yield obtained, but the-higher temperature, however, decreased the productivity of the catalyst. Increasing pressure of monomer sharply increases the productivity of the catalyst. Viscosity average molecular weight (M¯v) for some polymers obtained were determined. Increasing Al concentration and H2 decreased M¯v of polymer obtained.