Ethylene Homopolymerization by Ziegler-Natta (TiCl4/MgCl2) Catalyst through Full Factorial Experimental Design

Abstract

Full factorial experimental design (23) for the evaluation of slurry ethylene polymerization in the presence of an industrial TiCl4/MgCl2 Ziegler-Natta catalyst was employed. The following parameters were used as independentvariables: Al/Ti molar ratio, reaction temperature and hydrogen partial pressure. The total polymerization pressure was 9 bar. Catalyst activity, MFI (melt flow index) and melting temperature were statistically analyzed through response surface method. Hydrogen partial pressure had the most and temperature had the least effect on catalyst activity. Catalyst activity was affected by binary interactions of Al/Ti molar ratio-hydrogen partial pressure and temperature-hydrogen partial pressure. No interaction of temperature-Al/Ti molar ratio was found. Hydrogen partial pressure, temperature and their interaction had the strongest influence on MFI. Cubic models were employed for describing the surface responses of catalyst activity and melt flow index as a function of operating variables. The effects of Al/Ti molar ratio, reaction temperature, hydrogen partial pressure and their interactions were not significant from statistical point of view. Therefore no cubic model was employed.

Keywords

• polyethylene
• polymerization
• experimental design
• ziegler-natta
• slurry