Pechiney Electrometallurgie

Pechiney Recherche

Dominique Dubots

Jean-Louis Guille

Francis Dubrous

Pierre Faure

Sylvain Hantzer

Pierre Toulouse

The disclosure teaches a method for obtaining porous solids of refractory carbide with a large specific surface area. An exclusively organic, polymeric and/or copolymerizable compound, for example a resin, which can be coked and to provide a solid carbon skeleton, is mixed with a powder of metal, or metalloid, or a compound thereof which can be reduced by carbon. The mixture is shaped, the organic compound is cross-linked or hardened, and the compound is heat treated from 500.degree. to 1000.degree. C. to coke it, then heat treated to carburize it.

Method of obtaining porous solids based on refractory carbide

Abrasive and/or refractory products comprising at least one compound from the group of oxynitrides of one or more metals or metalloids (such as Al, Mg, alkaline earth metals, Si, Ti or Zr) and obtained by melting and solidification.

Abrasive and/or refractory products based on melted and solidified

A porous refractory carbide with a large specific surface area is disclosed. The refractory carbide has a skeleton of metallic or metalloid refractory carbide and has a bimodal open porosity with a group of pores of 1 to 100 microns and a group of pores smaller than 0.1 micron.

Binodal metallic carbide and its use as a catalyst

The invention relates to a catalytic system and to a method of producing such a system. The catalytic system consists of a support on which the catalytically active product is deposited. The support has mechanical or physical properties which are of interest in terms of the required working conditions, but a poor specific surface area. The catalytically active product, a metallic carbide, is obtained by coating the support in a suspension of a reducible compound of the metal in a solution of an organic compound, carbonizing this compound, reducing the metallic compound and carburizing the metal. The carbide thus obtained has a high specific surface area. Preferably, the support consists of silicon carbide produced by carbonizing a paste containing silicon, carbon and an organic resin. The invention is applicable to any form of catalyst but in particular to the monolithic catalysts intended for treating exhaust gases.

Catalytic system particularly for the postcombustion of exhaust gases

Electrically melted multiphase material based on alumina and aluminium

The invention is directed to a process for the production of fine grains of silicon carbide which are formed by an agglomerate of submicronic grains having a specific surface area that is at least 100 m.sup.2 .multidot.g.sup.-1, which are intended in particular to serve as a carrier for catalysts for petrochemistry, and for catalytic reactions at elevated temperature which can attain 1000.degree. C., the process comprising reacting vapors of silicon monoxide SiO on carbon, being characterized by: generating vapors of SiO in a first reaction zone by heating a mixture SiO.sub.2 +Si at a temperature of between 1100.degree. and 1400.degree. C., under a pressure of between 0.1 and 1.5 hPa; and, in a second reaction zone, contacting the SiO vapors with reactive carbon in the divided state with a specific surface area that is at least equal to 200 m.sup.2 .multidot.g.sup.-1 at a temperature of between 1100.degree. and 1400.degree. C. Preferably, the reactive carbon is doped by an addition of from 1 to 10% by weight of a metallic element selected from uranium, cerium, titanium, zirconium, hafnium and lanthanides.

Process for the production of silicon carbide with a large specific

The invention relates to a process for the preparation of silicon carbide whiskers by the reaction, in a non-oxidizing atmosphere, at a temperature of at least 1300.degree. C., of a charge composed of a mixture of carbon black and a source of silicon oxide, in which process the carbon black has an oxidability rate (measured by heating in air for 30 minutes at 600.degree. C.) of at least 85%, the silicon oxide source has a grain size of less than 100 .mu.m and the rate of rise in temperature between 1300.degree. and 1600.degree. C. is less than 30.degree. C.min.sup.-1 per minute if a static atmosphere prevails and at most 25.degree. C.min.sup.-1 if gas percolated. A stage of from 5 min to 5 h at 1600.degree. C. is optionally carried out. The carbon is preferably introduced into the reaction mixture in an over-stoichiometric quantity relative to the silica. The excess carbon is removed at the end of the reaction by oxidation in air at about 600.degree. C.

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Le Fayet, France

Dominique Dubots