General Aspects of Propylene Polymerization

Kinetic studies concerning TiCk/MgClj catalysts for propylene polymerization are relatively scarce. 

As is well known, all these systems are characterized by the lack of constant polymerization rate. Early work carried out at Montedison laboratories 96) has shown that, besides a productivity which is more than a hundred times higher than that of TiCl3 0.3 A1C13—AlEt2Cl, they demonstrate the following principal features  

Such experimental results have been rationalized by assuming a chemical deactivation of some of the active centers and the presence of at least two types of species on the catalytic surface These two are isospecific polymerization centers which are unstable with time, and only slightly specific polymerization centers which, in turn, are stable with time. The latter appear to be preferentially and reversibly poisoned by the outside donor. 

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