Abstract: Presulfurizing process and presulfurization promoter for a desulfurization catalyst to be used in a hydrodesulfurization unit of petroleum refinery of high molecular hydrocarbons, in which fresh metal oxide in said desulfurization catalyst is sulfurized with hydrogen sulfide produced from sulfur-containing compounds in a feed stream. In the invention, a compound having mercapto alkylthio group: HS—CmH2m—S— (in which “m” is an integer of 2 to 4) is added as promoter at a proportion of 10 ppm to 0.5% by weight and presulfurization is promoted at 180 to 260° C.

Abstract: The invention relates to the synthesis of difluoromethane by gas-phase catalytic fluorination of methylene chloride.

Abstract: The present invention relates to a latex containing two populations of particles of polymers based on vinyl chloride, respectively exhibiting mean diameters of between 0.9 and 1.3 &mgr;m and between 0.15 and 0.3 &mgr;m, in proportions such that the ratio by weight of the population with the lesser mean diameter to that with the greater mean diameter is between 0.4 and 0.7. Other subjects of the present invention are processes for the manufacture of the said latex and its application in fluid plastisols and foams of very good cellular quality.

Abstract: This composition, which is useful as a binder in the preparation of synthetic resin concretes or mortars, bonding primers or finishing coats, comprises (A) a system of monomers comprising: (a1) 50-90 parts of a dicyclopentenyloxyalkyl eater: where R=H or CH3; n=1 or 2; and R1=C2-C6 alkylene; (a2) 0-25 parts of at least one heavy (meth)acrylate giving a homopolymer with a Tg higher than that of a homopolymer of (a1); (a3) 0-25 parts of at least one heavy (meth)acrylate giving a homopolymer with a Tg lower than that of a homopolymer of (a1); (a4) 0-25 parts of at least one monomer containing at least two (meth)acrylic unsaturations; and (B) 5-30 parts of at least one poly(allyl glycidyl ether); and (C) an initiating system chosen from (C1) to (C4): (C1) 0.1-3 parts of at least one organic peroxide derived from a C3-C18 hydrocarbon compound and 0.1-2 parts of at least one aromatic amine; (C2) 0.

Abstract: The invention relates to the synthesis of difluoromethane by gas-phase catalytic fluorination of methylene chloride. To lengthen the lifetime of the catalyst the operation is carried out in the presence of chlorine.

Abstract: Activator solid support for metallocenes as catalysts in the polymerization of olefins, characterized in that it consists of a group of support particles for a solid catalytic component, which are formed from at least one porous mineral oxide, the said particles having been modified in order to carry, on the surface, aluminium and/or magnesium Lewis-acid sites of formula: functionalization agent having reacted with —OH radicals carried by the base particles of the support, the functionalization reaction having been followed by a fluorination reaction. Also disclosed is a catalytic system including a metallocene catalyst, which has optionally been subjected to a prealkylation treatment; a cocatalyst; and an activator solid support for metallocene, as defined above.

Abstract: The invention relates to a process for the preparation of nitrosyl chloride from a solution of nitrosylsulphuric acid in sulphuric acid and from hydrogen chloride, the said process being characterized in that the solution of nitrosylsulphuric acid is substantially free of water and that aqueous hydrochloric acid and gaseous hydrogen chloride are used in amounts such that the molar ratio of aqueous hydrochloric acid to nitrosylsulphuric acid is between 0.25 and 1.2 and the molar ratio of aqueous hydrochloric acid and of gaseous hydrogen chloride to nitrosylsulphuric acid is between 1.25 and 5.

Abstract: In order to isomerize a hydrofluorocarbon having a certain thermodynamic stability (HFC 1) into a hydrofluorocarbon of greater thermodynamic stability (HFC 2), the hydrofluorocarbon HFC 1 is subjected to a heat treatment in the presence of hydrogen at a temperature above 500° C. This process, which does not require the use of a catalyst, applies especially to the isomerization of 1,1,2,2-tetrafluoroethane into 1,1,1,2-tetrafluoroethane.

Abstract: The invention relates to thermoplastic master batches having at least one copolymer (A) of ethylene and of at least one unsaturated carboxylic acid ester as support and comprising vulcanization agents for rubbers. The invention also relates to a process for the preparation of master batches containing vulcanization agents and having a thermoplastic ethylene copolymer as support, this process consisting in using an extruder.

Abstract: The invention relates to a method of preparing polyamides, in which, in a first step, the anionic polymerization of at least one lactam is carried out and then, in a second step, a heat treatment is carried out on the polymer obtained, which has a distribution of the molar masses measured by SEC having a shape close to a Gaussian curve with a high-mass tail, at a high enough temperature and for a long enough time so as to obtain a unimodal distribution of the molar masses.

Abstract: The invention relates to alkoxysilacycloalkanes, to the process for their preparation and to their use in the polymerization of olefins. The introduction of these alkoxysilacycloalkanes into the olefin polymerization environment makes it possible to raise the heptane-insolubles content of the polymer finally formed.

Abstract: The present invention relates to a process for the manufacture of particles comprising magnesium chloride, which may serve as a support for a catalytic component for the polymerization of olefins, this process comprising a step of placing in contact between solid particles, an organomagnesium derivative and a chlorinating agent for the organomagnesium derivative. The process affords excellent control over the morphology of the support particles, particles of catalytic component and polymer particles.

Abstract: Water-in-water dispersions based on water-soluble polymers can be prepared using a polymer dispersant containing hydrophobic units. The dispersions of the invention are stable on storage and are of low viscosity.

Abstract: The invention relates to aqueous saline dispersions containing a water-soluble polymer and a dispersant based on a polymer, preferably a cationic polymer, containing hydrophobic units.

Abstract: The present invention relates to crosslinkable hot-melt adhesive compositions in the form of prepolymer containing free isocyanate functional groups; the said prepolymer results from the reaction of a polyisocyanate and of a copolymer (A) of ethylene and of at least one unsaturated carboxylic acid ester and containing hydroxyl functional groups. These adhesives are crosslinked by the ambient moisture.

Abstract: The invention relates to a method for shutting down an electrolysis cell with a membrane and an oxygen-reducing cathode, which comprises, after the electrical power and oxygen supplies have been disconnected, in emptying the oxygen compartment and filling it with demineralized water having a pH≦7 and in keeping this water in the oxygen compartment throughout the shutdown period.

Abstract: The invention relates to compositions comprising a matrix of an alloy of (a) polyamide and (b) polymer having polyamide blocks and polyether blocks, dispersed in which matrix is a crosslinked phase (c), the said compositions having a melt strength of more than 1.5 and a flexural modulus at 23° C. (in accordance with ISO 178-93) of less than 700 MPa and preferably between 50 and 250 MPa. Such a composition is useful for manufacturing extrusion blow-moulded parts, especially for cars. It also relates to articles additionally comprising a part made of polyamide and polyolefin or of a mixture of polyamide and polyolefin.

Abstract: The invention relates to a stabilized bimetal catalyst comprising an electrically conductive support and a metallic deposited coating consisting of a first metal M1 chosen from platinum and silver and a second metal M2, different from the first and chosen from the group consisting of platinum, silver, gold, ruthenium, iridium, rhodium and osmium. The invention also relates to a process for obtaining such a catalyst.

Abstract: In order to remove the methanesulphonyl chloride entrained by the gaseous HCl by-product, an amount of water ranging from 0.01 to 20%, relative to the mass of HCl to be treated, is injected into the HCl gas flow and the temperature is lowered to a value below or equal to 15° C.

Abstract: Mixed fluorination catalyst comprising one or more nickel and chromium oxides, halides and/or oxyhalides deposited on a support composed of aluminium fluoride or of a mixture of aluminium fluoride and alumina, characterized in that the weight of nickel/weight of chromium ratio is between 0.08 and 0.25, preferably between 0.1 and 0.2.