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

Ethylene polymerization with MgCl2/TiCl4/TEAl, as a Ziegler-Natta catalyst, wascarried out by slurry and gas phase processes. This catalyst was synthesizedwith a deliberate morphology by controlling the rate of recrystallization. Theparticle size distribution of the catalyst was very narrow which provided good stabilityin the reactor. The effects of temperature, monomer and hydrogen partial pressureon the catalyst activity and its deactivation coefficient were evaluated. The kineticparameters such as deactivation rate coefficient and activation and deactivationenergies were determined for both processes. It was found that deactivation ratecoefficient decreased by increased temperature of maximum 70°C, while it decreasedbeyond this temperature. The initial rate of reaction in slurry and gas phase ethylenepolymerizations increased by increasing the reaction temperature to maximum 80°Cand in comparison, at longer reaction times ( 20 min) it showed a drop with maximumreaction temperature of 70°C. It was also found that the deactivation rate coefficient ofgas phase polymerization decreased by increasing the partial pressure (concentration)of hydrogen. The catalyst productivity for slurry phase polymerization of ethyleneincreased by increasing the Al/Ti molar ratio as high as 90 and beyond this ratio thecatalyst productivity dropped for the same polymerization.