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K. Czaja, В. Król



Comparison of the generation II with IV heterogeneous Ziegler–Natta catalysts used in propylene polymerizations


Polimery 1998, No 5, 287


DOI: dx.doi.org/10.14314/polimery.1998.287


Summary

An unsupported TiCl3-based catalyst (generation II), modified with n-butyl ether and AlEt2Cl3, was compared with a MgCl2/dibutyl phthalate/AlEt3/cyclohexylmethyldimethoxysilane catalyst system (generation IV) in propylene polymerizations. The latter (magnesium-supported) was fund to be more than 20 times as active as the former and more stereospecific, but to yield PP with a lower molecular weight (Table 2). The kinetics of the polymerizations studied with either of the catalyst, and involving the determination of concentrations of active sites [C0*] and elementary reaction rate constants (Table 4) based on earlier kinetic models, showed the C0*-values in the magnesium-supported catalyst to be much higher than those in the unsupported catalyst, thereby bearing out the higher activity of the former, whereas the propagation rate (krp) remained practically unaffected.


Keywords: active sites, titanium catalyst of generation II, Ti-Mg catalyst of generation IV, kinetics of propylene polymerization, elementary re action rates


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