Kinetics of Slurry and Gas Phase Polymerizations of Ethylene Using a Novel Heterogeneous Ziegler-Natta Catalyst of Specific Morphology

Ethylene polymerization with MgCl2/TiCl4/TEAI, as a Ziegler-Natta catalyst, was carried out by slurry and gas phase processes. This catalyst was synthesized with a deliberate morphology by controlling the rate of recrystallization. The particle size distribution of the catalyst was very narrow which provided good stability in the reactor. The effects of temperature, monomer and hydrogen partial pressure on the catalyst activity and its deactivation coefficient were evaluated. The kinetic parameters such as deactivation rate coefficient and activation and deactivation energies were determined for both processes. It was found that deactivation rate coefficient decreased by increased temperature of maximum 70 degrees C, while it decreased beyond this temperature. The initial rate of reaction in slurry and gas phase ethylene polymerizations increased by increasing the reaction temperature to maximum 80 degrees C and in comparison, at longer reaction times (>20 min) it showed a drop with maximum reaction temperature of 70 degrees C. It was also found that the deactivation rate coefficient of gas phase polymerization decreased by increasing the partial pressure (concentration) of hydrogen. The catalyst productivity for slurry phase polymerization of ethylene increased by increasing the Al/Ti molar ratio as high as 90 and beyond this ratio the catalyst productivity dropped for the same polymerization.