Comparative study of Ziegler-Natta catalyst synthesis for ethylene polymerization

Abstract

Nowadays, polyethylene becomes more usage in olefin industries. Ziegler-Natta catalyst was used to synthesize polyethylene Therefore, it is important to develop this catalyst efficiently to obtain the high activity and can be used to synthesize polymer that we desire. For this research, MgCl2 synthesized by the recrystallization method and Mg(OEt)₂ synthesized by the chemical reaction method were chosen to investigate synthesis parameters which affect on the catalytic activity. Synthesis parameters include that paddle speed, holding temperature and dropping rate. The results showed that the paddle speed at 100 and 200 rpm gave the highest catalytic activity for recrystallization and chemical reaction method, respectively. For the recrystallization method, the holding temperature had little effect on activity and holding temperature at 90 ℃ exhibited the highest activity for the chemical reaction method. Dropping rate had only little effect on activity. Sensitivity of parameters on catalytic activity were compared both recrystallization and chemical reaction method. It was found that recrystallization method was more sensitive than chemical reaction method for paddle speed effect due to more viscosity. For holding temperature effect, chemical reaction method was more sensitive than recrystallization method because inactive species from conversion Mg(OEt)₂ to MgCl₂ can be dissolved back into the solvent at high temperature by chemical reaction method. Both recrystallization and chemical reaction methods were not sensitive to the dropping rate effect. The best synthesis catalyst condition of each method was used to compare activity. Activity from recrystallization method was higher than that from chemical reaction due to more amount of Ti³⁺ present.