Abstract: Silica supported catalyst composition useful in olefin polymerization, having a SiO2 content not more than 70 weight %, a transition metal (M) content between 2.5 and 9.1 weight %, a magnesium content between 0.5 and 3.3 weight %, an aluminium content between 0.3 and 5 weight % and a chlorine content between 5 and 30 weight %. The silica support has, prior to addition of catalytically active ingredients, a residual surface hydroxyl content between 0.6 and 2 mmole/g of silica, and the molar ratio of transition metal (M) to magnesium is between 0.3 and 2.5.

Abstract: The present invention provides a new process for preparing a catalyst for the gas phase polymerization of olefins wherein the sequence of addition of the catalyst components and the selection of the said components provides a catalyst composition which exhibits a superior response to hydrogen, a surprisingly high productivity and an improved activity profile. The catalyst consists of compounds of a group IV transition metal, Mg, C1 and A1 supported on a silica support.

Abstract: An ethylene homopolymer having a density of from about 0.956 to about 0.970 g/cm3 and a high load melt index (190° C. and 21.6 kg) of from about 7 to about 21 g/10 min. A continuous polymerization process for the production of the ethylene homopolymer, in the presence of a diluent chosen from the group consisting essentially of n-butane, n-hexane, n-heptane, isobutane, isopentane, isooctane, 2,2-dimethylpropane, cyclopentane, cyclohexane and their mixtures, wherein ethylene is brought into contact with a chromium oxide catalyst deposited on an inorganic support containing from about 0.1 to about 5 wt % chromium and activated at a temperature from about 600 to about 900° C., at a polymerization temperature from about 55 to about 150° C., the ethylene concentration in the diluent being from about 1 to about 10 mol %. A composition consisting essentially of the ethylene homopolymer, the composition having a density of from about 0.956 to about 0.

Abstract: Cocatalytic composition resulting from bringing an organoaluminium halide (A) into contact with an electron-donating organic compound (ED) selected from esters, amides and ketones, the organoaluminium halide (A) possessing an atomic ratio halogen (X)/aluminium (Al) of greater than 1 and less than 1.3, the halide (A) and the compound (ED) being employed in a mole ratio halide (A)/compound (ED) of greater than 20. Catalytic systems which are usable for the polymerization of alpha-olefins, comprising such a cocatalytic composition and a solid based on titanium trichloride complexed with an electron-donating compound.

Abstract: Process for the polymerization of alpha-olefins, which is carried out in the presence of a catalyst system comprising:(1) a solid based on completed titanium trichloride;(2) an organometallic compound of metals of groups IA, IIA, IIB and IIIB of the Periodic Table, and(3) an electron-donor organic compound, the solid (1) based on complexed titanium trichloride having been preactivated by being brought into contact with a preactivator comprising the product of reaction of a trialkylaluminum or alkylaluminum chloride compound (a) and of a compound (b) chosen from hydroxyaromatic compounds whose hydroxyl group is sterically hindered, then isolating the predetermined solid (1) from the medium in which it was found.This process enables propylene to be polymerized with an improved stereospecificity without any significant decrease in catalyst activity.

Abstract: Cocatalytic composition resulting from bringing an organoaluminium halide (A) into contact with an electron-donating organic compound (ED) selected from esters, amides and ketones, the organoaluminium halide (A) possessing an atomic ratio halogen (X)/aluminium (Al) of greater than 1 and less than 1.3, the halide (A) and the compound (ED) being employed in a mole ratio halide (A)/compound (ED) of greater than 20.Catalytic systems which are usable for the polymerisation of alpha-olefins, comprising such a cocatalytic composition--and a solid based on titanium trichloride complexed with an electron-donating compound.