The function of amines in conventional and supported Ziegler-Natta catalysts

✍ Scribed by M.C. Sacchi; I. Tritto; P. Locatelli

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 336 KB
• Volume: 24
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(88)90140-1

✦ Synopsis

A study was made of the effect of Et~ N and 2, as donor additives on the catalysts (a) MgC12/TiC14/AIEt 3 , (b) f-TiC13/AIEt 3 and (c) 6-TIC13/ZnEt 2 for propylene polymerization. The productivity trends show a maximum, at low base concentration, in the presence of the A1Et 3 based catalysts (a) and (b), due (especially for TMPip) to a noticeable increase of the isotactic fraction. At the same base concentration, both amines cause a minimum of productivity in the presence of the ZnEt2 based catalyst (c). These findings indicate that the amines may exert at least two different and concurrent effects: (i) poisoning of both isotactic and atactic sites; (ii) activation of the isotactic sites. Either the former or the latter effect prevails, depending on the equilibrium reactions in which the amines and the alkyl metal are involved.