The polymerization of propylene with VCl3 and aluminum alkyls has been studied. The decrease of the polymerization rate with the increase of the polymerization temperature, in the presence of the catalytic system VCl3‐Al(C2H5)3, is connected with the surface reduction of VCl3 to VCl2. When using Al(C2H5)2Cl at temperatures below 90°C. no reduction of VCl3 is detectable, and the rate of polymerization regularly increases with increasing temperature. Using VCl3 in combination with Al(C2H5)3 the stereospecificity is higher than in the case of Al(C2H5)2Cl, in contrast to catalytic systems based on violet TiCl3.
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Natta et al. (1964) studied this question.
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