Gas-phase polymerization of propylene with a highly active Ziegler-Natta catalyst

The polymerization of propylene in the gas phase has been studied with the same high-activity catalyst as was used for liquid-phase polymerizations in earlier work. Catalyst injection, the influence of the support bed, and pr econtacting of the catalyst with the cocatalyst and the electron donor have been investigated. Furthermore, different ways of prepolymerization were t ested. The kinetics can be described with the same model as was used for th e liquid-phase polymerizations. The reaction rate was proportional to the p ressure at pressures above 5 bar; at lower pressures the rates are lower. C omparison of the reaction rates in the gas phase and liquid phase showed th e rates in the gas phase were still lower than in the liquid phase. The fas t decay observed in the gas-phase polymerizations indicated that thermal ru naway and deactivation may occur at temperatures above 40 - 45 degrees C.