Effect of electron donors and extraction on ziegler-natta catalyst preparation for propylene polymerization

Abstract

This research is aimed to improve the extraction method in the preparation of Ziegler-Natta catalyst used for PP production. The TiCl4/MgCl2-SiO2 Ziegler-Natta catalysts with added internal electron donor, dibutylphathalate (DBP), were prepared. Extraction by decant method was compared with reflux method (used in industry). The conditions of decant extraction such as time, cycle of decant, and volume of extract solvent were studied. Ti, Mg and Cl contents were analyzed as well as the residual solvent and DBP. Catalytic performance and stereospecific properties of polypropylene (PP) were compared. Experimental results show that the extraction by the decant method gave the higher residual quantity of DBP on the catalyst than that from the reflux method. In addition three different external electron donors were compared. It was found that cyclohexyl methyl dimethoxysilane (C-donor) gave best productivity (24,141 g PP/g cat.) when C-donor/Ti ratio = 5 was used. Surface of catalysts were examined by SEM. The crude catalyst shows more roughly surface than the extracted catalysts. The catalyst after extraction by both methods show good morphology. The PP polymers replicate their catalyst shape.