Abstract: A composition for purifying exhaust gases of an internal combustion engine capable of consuming fuel with lean air-fuel ratios includes elements adsorbing the NOx present in the exhaust gases, in the presence of excess oxygen and releasing the adsorbed NOx when the oxygen concentration of the exhaust gases decreases. The NOx adsorbing element includes in combination: a first composition comprising a support and an active phase, the active phase being based on manganese and at least another element A selected among, alkalines and alkaline-earths, the manganese and element A being chemically bound; a second composition including a support and an active phase based on manganese and at least another element B selected among alkalines, alkaline-earths and rare earths, the second composition having or being capable of having a specific surface area of at least 80 m2/g after being calcined at 800° C., and furthermore, a reducing and/or three-way catalyst function is incorporated in the NOx adsorbing element.

Abstract: A device for purification of exhaust gases of an internal combustion engine capable of achieving combustion of a fuel with lean air-fuel ratios. A NOx-adsorbing mechanism is installed in the exhaust line of the engine. That NOx-adsorbing mechanism can absorb the NOx present in the exhaust gases in the presence of excess oxygen and can release the absorbed NOx when the oxygen concentration of the exhaust gases decreases. The NOx-adsorbing mechanism does not contain any composition capable of acting as an NOx reduction catalyst, and especially no precious metal, and further a three-way catalyst is installed in the exhaust line downstream from the NOx-adsorbing mechanism.

Abstract: A composition based on cerium oxide and on zirconium oxide and, optionally, on a yttrium, scandium or rare-earth metal oxide. The cerium/zirconium atomic proportion is at least 1. The compound exhibits a specific surface, after calcination for 6 hours at 900° C. of at least 35 m2/g and an oxygen storage capacity at 400° C. of at least 1.5 ml of O2/g. The composition is prepared by mixing, in a liquid medium, a cerium compound, a zirconium compound and, if appropriate, a yttrium, scandium or rare-earth metal compound; heating and calcining the precipitate obtained; and using a zirconium solution having an amount of base necessary to reach the equivalent point during an acid/base titration of the solution having a molar ratio of OH−/Zr≦1.65. The composition thus obtained is used in the manufacture of multi-functional catalysts.

Abstract: The invention relates to a composition based on zirconium oxide and comprising cerium oxide which has a specific surface of at least 30 m2/g after calcination for 6 hours at 900° C. and which is provided in the form of a pure solid solution of cerium oxide in zirconium oxide. According to another embodiment, this composition can additionally comprise a doping element and can exhibit a specific surface of at least 25 m2g after calcination for 6 hours at 1000° C. A process for the preparation of these compositions comprises the following stages: a mixture is prepared, in liquid medium, containing a zirconium compound and a cerium(IV) compound; the said mixture is heated at a temperature greater than 100° C.

Abstract: A method for processing soot containing one or more rare earths, wherein said soot is contacted with an oxygen-containing gas, is disclosed. The method comprises (a) preparing an aqueous phase comprising a dispersion of at least one oxygenated metal compound; (b) simultaneously or consecutively contacting a suspension from step (a) with an organic phase including at least one amphiphilic agent and preferably an organic mixture or compound as the solvent; and c recovering the organic phase. Said oxygenated metal compound is produced by means of a method according to which a solution including at least one soluble rare-earth salt, usually an acetate and/or a chloride, is prepared; the solution is contacted with a basic medium and the resulting reaction mixture is maintained at a basic pH; and the precipitate formed by atomization or freeze-drying is recovered. Said method is useful in inorganic synthesis and catalysis.