Effects of Temperature and Cocatalyst Concentration on the Number of Active Sites in a TiCl۴/Mg(OEt)۲ Catalyst for Ethylene Polymerization

The slurry polymerization of ethylene was studied by employing a (TiCl۴/Mg(OEt)۲/TEA) catalyst system in hexane. The effects of triethylaluminum concentration and temperature on polymer yield and polymer viscosity average molecular weight, Mv, were investigated. The maximum polymer yield was obtained at an Al/Ti molar ratio of ۱۲۴. The highest yield and Mv were achieved at ۶۰ °C. The concentration of active sites of the obtained catalyst system for ethylene polymerization was evaluated as a function of Al/Ti molar ratio and polymerization temperature. Increasing Al/Ti molar ratio from ۶۲ to ۱۲۴ raised the active site concentration of catalyst, [C*], from ۰.۰۰۰۳ to ۰.۰۰۱۷, whereas a further increase in Al/Ti molar ratio from ۱۲۴ to ۲۳۱ reduced [C*] from ۰.۰۰۱۷ to ۰.۰۰۱۳. Similarly, increasing the temperature from ۴۰ °C to ۶۰ °C increased the [C*] from ۰.۰۰۰۲ to ۰.۰۰۱۷, but when temperature was increased above the optimum value, [C*] decreased.

Keywords:

Active Site Concentration , Triethylaluminum , Ziegler-Natta Catalyst , Ethylene Polymerization , Molecular Weight