Abstract: The present invention relates to a process for polymerizing at least one olefin with the aid of a catalyst containing at least one organometallic compound of a transition metal possessing at least one ligand of cyclopentadienyl or substituted cyclopentadienyl type. The polymerization is carried out in gas phase or in suspension in a liquid polymerization medium selected amongst saturated or unsaturated hydrocarbons, in the presence of hydrogen and a polymerization component selected amongst halogenated hydrocarbons. The combined use of hydrogen and halogenated hydrocarbon in such a polymerization process simultaneously improves the catalyst activity and the molecular weight control of the polymer.

Abstract: The present invention relates to an ethylene polymerization process carried out with the aid of a catalyst system of the Ziegler-Natta type consisting essentially of titanium, halogen and magnesium. The process is performed such that the ethylene polymerization takes place in the presence of a polychlorinated saturated hydrocarbon compound. The halogenated hydrocarbon compound is used in a quantity such that the molar ratio of the halogenated hydrocarbon compound to titanium of the catalyst is in the range from 0.01 to 1.8. Preferably the halogenated hydrocarbon compound is chloroform or trichloro-1,1-ethane.

Abstract: The present invention relates to a solid catalyst suitable for polymerizing olefins in a heterogeneous process, the catalyst consisting of spheroidal particles having a narrow particle size distribution and comprising (i) a support containing magnesium dichloride and an electron-donor free from labile hydrogene, (ii) a zirconium metallocene, and (iii) optionally an organoaluminium compound which is an aluminoxane preferably. The solid catalyst may be used in the form of a prepolymer comprising a polyethylene or a copolymer of ethylene and an active zirconium metallocene catalyst essentially consisting of atoms of Zr, Mg, Cl and Al, preferably in the form of spheriodal particles. The solid catalyst or the prepolymer may be used for producing polyethylene or copolymer of ethylene having from 0.5 to 20 ppm of Zr and a molecular weight distribution from 2 to 5, in the form of a powder having a bulk density from 0.3 to 0.55 g/cm.sup.3, preferably consisting of spheroidal particles.

Abstract: The present invention relates to an alpha-olefin prepolymer catalytically active in an alpha-olefin (co-)polymerization comprising a transition metal, an organometallic compound and an antistatic agent. The prepolymer can be prepared by contacting the antistatic agent with a catalyst comprising the transition metal and the organometallic compound before or during an alpha-olefin prepolymerization. It can also be prepared by contacting the antistatic agent with an alpha-olefin prepolymer after a prepolymerization. It can also be prepared by a combination of the two methods. The prepolymer can be introduced into a gas phase (co-)polymerization medium for preparing polyolefin directly in a dry powder form, with a reduced amount of sheeting and agglomerates.

Abstract: The present invention relates to a catalyst and a process for preparing a catalyst suitable for polymerization of olefins. The process is carried out in a hydrocarbon liquid medium and comprises successively contacting a refractory oxide support with (a) a dialkylmagnesium optionally with a trialkylaluminium, (b) a particular monochloro organic compound, (c) a titanium and/or vanadium compound(s), and then (d) with ethylene optionally mixed with a C.sub.3 -C.sub.8 alpha-olefin in the presence of an organo-aluminium or organozinc compound to form a prepolymerised catalyst. The catalyst has a high activity, particularly in a gas phase polymerization of ethylene, and has a great ability of copolymerizing alpha-olefins with ethylene.

Abstract: The present invention relates to a catalyst and a process for preparing a catalyst suitable for polymerization of olefins. The process is carried out in a hydrocarbon liquid medium and comprises successively contacting a refractory oxide support with (a) a dialkylmagnesium optionally with a trialkylaluminium, (b) a particular monochloro organic compound, (c) a titanium and/or vanadium compound(s), and then (d) with ethylene optionally mixed with a C.sub.3 -C.sub.8 alpha-olefin in the presence of an organo-aluminium or organozinc compound to form a prepolymerized catalyst. The catalyst has a high activity, particularly in a gas phase polymerization of ethylene, and has a great ability of copolymerizing alpha-olefins with ethylene.

Abstract: The present invention relates to a solid catalyst suitable for polymerizing olefins in a heterogeneous process, the catalyst consisting of spheroidal particles having a narrow particle size distribution and comprising (i) a support containing magnesium dichloride and an electron-donor free from labile hydrogen, (ii) a zirconium metallocene, and (iii) optionally an organoaluminium compound which is an aluminoxane preferably. The solid catalyst may be used in the form of a prepolymer comprising a polyethylene or a copolymer of ethylene and an active zirconium metallocene catalyst essentially consisting of atoms of Zr, Mg, Cl and Al, preferably in the form of spheriodal particles. The solid catalyst or the prepolymer may be used for producing polyethylene or copolymer of ethylene having from 0.5 to 20 ppm of zr and a molecular weight distribution from 2 to 5, in the form of a powder having a bulk density from 0.3 to 0.55 g/cm.sup.3, preferably consisting of spheroidal particles.

Abstract: Peroxidic complexes of vanadium, niobium or tantalum, wherein the metal is linked to an oxygen molecule carrying two negative charges, are used either as reactants for the oxidation of olefinic substrates or hydrocarbons, or as hydrocarbons oxidation catalysts, particularly for converting olefinic compounds to epoxides or aliphatic or aromatic hydrocarbons to the corresponding alcohols or phenols.