Effect of different donors on kinetics of Zn catalysts and molecular weight of the obtained polypropylene

FERREIRA, MARÍA LUJÁN; DAMIANI, DANIEL E.

JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

ELSEVIER SCIENCE BV

Año: 1999 vol. 150 p. 53 - 69

1381-1169

This paper studies MgCl2/internal donor/TiCl4//external donor/AlEt3 catalytic systems where ethyl benzoate (E.B.) or 2,2,6,6 tetramethylpiperidine (TMPiP) are used as internal and external donors. E.B. as external donor does not change the molecular weight of the product with TMPiP as internal donor. The molecular weight of polypropylene decreases drastically and global productivity and stereoselectivity are very low with MgCl2/internal Donor/TiCl4//external donor/AlEt3 when TMPiP is the external and internal donor. In this case the insoluble fraction in n-heptane is highly stereospecific and the molecular weight is similar to commercial products. We present a new explanation of these results, based on Ystenes proposal, comparing both precatalysts.