Influence of internal and external electron-donors in a supported ziegler-natta catalyst on isotacticity of polypropylene

The slurry polymerization of propylene with TiCl4-AlEt3 catalyst system on MgCl2 support was investigated to study the effect of addition of internal electron donor and external electron donor to polypropylene synthesis. The suitable conditions are Al/Ti molar ratio of 167, at propylene presure of 100 psi, and at the temperature of 90ํC. Internal electron donor used in this study was diethyl phthalate and external electron donor used were tetraethoxysilane (TES), methyltriethoxysilane (MTES), dimethyldiethoxysilane (DMDES), trimethylethoxysilane (TMES), and phenyltriethoxysilane (PTES) at molar ratio of external electron donor/Al of 0.05. It was found that the presence of the internal electron donor in TiCl4-AlEt3 catalyst on MgCl2 support attributes the higher activity while the isotactivity remains unchanged. The number of alkoxy groups in external electron donor had an effect on catalyst activity and isotacticity of polypropylene. It was also observed that the sequence of the change of the activity by different external electron donors was the same irrespective of the presence or absence of internal electron donor and also not depended on the methods of the preparation of the catalyst.