Atochem

Elf Atochem S.a.

Produits Chimiques Ugine Kuhlmann

Comurhex

Comurhex Societe Pour La Conversion De L'uranium En Metal Et Hexafluorure

Roland Bachelard

Jean-Pierre Disson

Philippe Joubert

Pierre Ravenel

Annick Faure

Robert Barral

Yves Correia

Rene Clair

Alain Petit

Bruno Morlhon

Maurice Lamalle

Bernard Jean Gurtner

Robert Koeppel

Patrick Germanaz

Pierre Lakodey

Hydrocarbons, e.g., ethylene, are steady-state catalytically oxychlorinated into chlorocarbons, e.g., 1,2-dichloroethane, by fluidizing a fluidizable charge by directing a gaseous feedstream containing a hydrocarbon therethrough and therein oxychlorinating such hydrocarbon, the gaseous feedstream further comprising an oxygen-containing gas and gaseous hydrochloric acid and the fluidizable charge comprising immixture of a catalytically effective amount of an oxychlorination catalyst and particles of a catalytically and chemically inert solid substance, and which further comprises introducing a solution or suspension of a catalytically active copper compound into such fluidized charge during the oxychlorination reaction.

Catalytic oxychlorination of hydrocarbons to produce chlorocarbons

Ceramic preforms comprising monocrystalline hexagonal platelets of .alpha.-alumina, well adopted for conversion into refractory bricks or ceramic composites, are prepared by crystallizing a settled fine powder of amorphous alumina, transition alumina or alumina hydrate, advantageously in the presence of a fluoro-compound flux, into a coherent mass of such hexagonal platelets of .alpha.-alumina.

Ceramic preforms comprising monocrystalline hexagonal platelets of

Gamma-aluminum oxynitride ground powders, white in color and well suited for conversion into optically transparent ceramic shaped articles, 100% of the particles of which being less than 10 .mu.m in size and exhibiting a transmittance of at least 8%, are prepared by grinding particulate gamma-aluminum oxynitride agglomerates having a porosity of greater than 75%, such agglomerates themselves being produced by interreacting dry powdery admixture of aluminum nitride, alpha-alumina, and an alumina of high specific surface area or precursor thereof.

Optically transparent gamma-aluminum oxynitride powders and ceramic

The invention relates to a continuous process for the preparation of aluminum nitride by the carbonitriding of alumina. According to this process, a reaction that uses alumina, carbon, and a resin that generates carbon by pyrolysis is performed in a methodical reactor. The invention relates to a continuous process for the preparation of aluminum nitride by the carbonitriding of alumina.

Continuous process for the preparation of aluminum nitride by the

The present invention relates to a new process for the manufacture of fine powder of silicon nitride, to this powder and to the sinters obtained from the latter. The process comprises the reaction, in a nitrogen countercurrent and in continuous fashion, of silica, carbon and a seed crystal, in the presence of a volatile compound of a metal chosen from the group consisting of Be, Mg, Ca, Sr, Ge, Sn, Ti, Hf, Na and Ba, in a reaction zone possessing a temperature gradient, comprising a hot zone in which the said metal compound passes into the gaseous state and a cold zone in which the said metal compound in the gaseous state condenses, the said metal compound in the gaseous state being carried from the hot zone to the cold zone by the nitrogen countercurrent.

Continuous process for the preparation of silicon nitride by

Ceramic preforms comprising monocrystalline hexagonal platelets of .alpha.-

Aluminum nitride (AlN) is continuously produced by continuously carbonitriding a continuously replenished charge of alumina, for example successive charges of alumina/carbon extrudates, in a reaction zone comprising at least one conduit, the ratio of the exchange surface area/volume of which at least one conduit ranging from 5 to 50 m.sup.-1, preferably from 10 to 50 m.sup.-1, and continuously withdrawing product AlN therefrom.

Carbonitriding of alumina to produce aluminum nitride

The invention relates to a continuous process for the preparation of aluminium nitride by the carbonitriding of alumina. According to this process, the reaction, which employs alumina, carbon and nitrogen, is carried out in a moving-bed reactor characterized in that the reaction area has a plurality of conduits.

Whisker-free particulates of silicon nitride (Si.sub.3 N.sub.4), e.g., spheres, beads, or a variety of other shaped articles exhibiting a regular and controlled particle size, are produced by incorporating a primary reaction mixture of silica and carbon into a porous, carbon-based matrix material, next carbonitriding the composite thus formed, and characteristically eliminating excess carbon from the carbonitrided composite.

Production of whisker-free Si.sub.3 N.sub.4 particulates by

Macrocrystalline .alpha.-alumina hexagonal platelets, well adapted as reinforcing materials and polishing agents, are prepared by calcining admixture of transition or hydrated alumina and a fluorocompound flux, such fluorocompound flux having a melting point of up to 800.degree. C. and, in the molten state, serving to dissolve the transition/hydrated alumina.

Macrocrystalline .alpha.-alumina hexagonal platelets

A process is disclosed for producing sintered mixed metal oxide nuclear f pellets containing UO.sub.2 and the oxide of at least one other fissionable or rare earth element M, the pellets being directly soluble in nitric acid without nitric acid additive or prior treatment of the pellets. The process comprises the steps of mixing together nitrate solutions of the elements, concentrating the mixture of solutions, thermally denitrating the concentrated nitrate mixture without additives, to obtain an intermediate mixed oxide powder, calcining the intermediate mixed oxide powder, reducing the calcined mixture, stabilizing the uranium oxide UO.sub.2 in the reduced oxide mixture, shaping and pressing the resulting stabilized, reduced oxide mixture to obtain pellets of green material, sintering the pellets of green material and grinding the sintered pellets. The intermediate steps of this process produce mixed oxide powders of high flowability and good sinterability without the necessity of crushing which tends to produce troublesome effluent or dangerous aerosols of solids.

Process for producing sintered mixed oxides which are soluble in nitric

Metal carbide and metal nitride powders produced by the carbothermal reduction of one or more metal oxides reacted with a binder material and a carbonaceous additive or optionally, a binder capable of supplying carbon to the reaction. The metal oxides are selected from among SiO.sub.2, Al.sub.2 O.sub.3, TiO.sub.2, ZrO.sub.2, HfO.sub.2 and B.sub.2 O.sub.3 and are combined with the binder in the presence of carbon to form granules having a controlled pore volume. The granules are then subjected to a carbothermal reduction reaction, in the presence of a nitrogen or a neutral atmosphere, to produce metal nitrides or metal carbides respectively, having an excess of carbon incorporated therein. The product is subsequently heated to react the excess carbon within the compound with oxygen from the atmosphere to form carbon monoxide gas, which may be removed by an optional exhaust system. The remaining metal carbide or metal nitride powder may then be collected and used in various applications such as the production of ceramic objects.

Metal carbide and nitride powders

Method of making metal carbide and nitride powders

Process for the preparation of pulverulent metallic oxides with predetermined reactivity which is adjusted by the specific surface area, which are intended to be subjected to subsequent conversions, by thermal treatment of corresponding nitrates in the form of an aqueous solution or of a solids material, consisting of hydrated uranyl nitrate, on its own or in admixture with at least one of thorium nitrate, cerium nitrate and plutonium nitrate, which process is characterized in that it consists of two treatment stages:

Growing community of inventors

Lyons, France

Roland Bachelard