Novel catalyst systems of the Ziegler-Natta catalysts

Catalyst systems of the Ziegler-Natta catalysts, containing, as active ingredients DOLLAR A a) a solid component comprising a compound of titanium or vanadium, a compound of magnesium, a particulate inorganic oxide as support and an internal electron donor, DOLLAR A as well as cocatalyst DOLLAR a b) an aluminum compound and DOLLAR a c) optionally a further, external electron donor, DOLLAR a wherein the particulate, inorganic oxide used has a specific surface area of ​​350 up to 1000 m · 2 · / g and an average particle diameter DOLLAR I1 in the range of having 5 to 60 mum and consisting of particles composed of primary particles having an average particle diameter DOLLAR I2 in the range of 1 to 10 mum and which contain between the primary particles cavities or channels in which the macroscopic proportion of voids or channels having a diameter greater 1 mum to the particles of the inorganic oxides in the range of 5 to 30 vol .-% and wherein the molar ratio between the compound of magnesium and particulate inorganic oxide from 0.5: 1 to 2.0: 1.