[mlundo]

hallo everyone

I have searched a lot but I was not able to find the procedure to prepare the Ziegler-Natta Catalyst, that´s to say in what proportion I have to mix the TiCl4 and the Al(CH2CH3)3 co-catalyst, and in what solvent should I do this.

thank you in advance

Filippo

[michaelmotes]

Catalyst recipes based on TiCl4, MgCl2, and THF: The active ingredient
in these catalysts is a Ti-Mg complex formed in a reaction between TiCl4 and
MgCl2 in THF (tetrahydrofuran) solution. Each of the two
starting compounds forms THF-soluble complexes, MgCl2· (THF)2 and
TiCl4 . (THF)2. Mixing the two solutions produces bimetallic complexes of well-
defined structures. The [Ti]:[Mg] ratio in the complexes
ranges from 1:1 to 1:5 depending of the ratio between TiCI4 and MgCl2 in solution.
Most of the complexes are ionic, e.g:

TiCI4 . (THF)2 + 2 MgCl2 . (THF)2-(THF) [Mg2(u-Cl)3 . (THF)6]+ [TiCl5 . THF]-

These complexes are active polymerization catalysts by themselves.
However, they are usually placed into silica pores. Hydroxyl groups are
removed from the silica surface, first by calcining it at 600°C and then by treating
remaining silanol groups with AlEt3. Solution of TiCl4
and MgCl2 in THF is mixed with the treated silica and then THF is removed
by evaporation at 50-60°C causing the ionic Ti-Mg complex to precipitate within
silica pores.
These solid products, when combined with AlEt3, form very active polymerization
catalysts. However, they have several deficiencies. including relatively
poor reactivity toward 1-alkenes. This deficiency was alleviated by pre-treating the
solid catalysts with mixtures of trialkylaluminum compounds and AlEt2Cl,
a step resulting in the removal of a part of THF from the crystalline complexes.