Effect of cocatalyst combination in titanium-based ziegler-natta catalyst on olefin polymerization

Abstract

This research focused on effect of cocatalyst types (TEA, TnOA, and TEA+TnOA) on titanium-based Ziegler-Natta catalyst in olefin polymerization both in slurry and gas-phase systems. This study has been divided into four sections. The commercial titanium-based catalyst was selected to investigate effect of reaction temperature and oxidation state of titanium from ESR measurement on slurry ethylene and propylene polymerization in the first and the second parts, respectively. The commercial catalyst with TEA exhibited the highest activity in ethylene polymerization. However, divalent, and trivalent of titanium (Ti2+ and Ti3+) was active in ethylene polymerization to produce more polymer. Stability of Ti3+ was demonstrated to assist insertion of 1-hexene. Hence, propylene polymerization under different reaction temperatures was conducted to evaluate the titanium oxidation state (Ti3+). The ESR results revealed that TEA+TnOA at 50oC can stabilize titanium (III) state.

Regarding to the third and fourth parts, different magnesium sources supported-catalyst; MgCl2 (Cat A), MgO (Cat B), and Mg(OEt)2 (Cat C); were compared in gas-phase ethylene polymerization. The modification of supported catalyst could improve the performance of catalyst and polymer. The results presented that Cat C or Mg(OEt)2 reacting with TEA showed the highest catalytic activity for both homo- and co-polymerization of ethylene. The addition of 1-hexene as comonomer could improve the activity and higher comonomer response called as “comonomer effect”. Moreover, the polymer obtained in gas-phase process exhibited remarkably better morphology than in slurry process.