as-phase polymerization of ethylene over a prepolymerized MgCl2

supported TiCl4. catalyst was compared with slurry polymerization. An accelerationtype or hybrid-type rate behavior for the slurry polymerization

but a decay-type rate behavior for the gas-phase polymerization have been observed. The difference in the apparent kinetics between these two processes could result from monomer diffusion resistance in the slurry polymerization and overheat effect in the gas-phase polymerization. The measurment of the oxidation states of titanium in the catalyst indicated that more titanium ions were reduced to lower oxidation state in the gas-phase process than in the slurry process. The preepolymerization temperature and yield also remarkably affected the polymerization activity and kinectic behavior.