Cerium- and zirconium-based mixed oxides
AssigneeRhodia Operations
InventorsSimon Ifrah, Wie Li, Valérie Buissette, Stéphane Denaire, Rui Miguel Jorge Coelho Marques
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Abstract
Provided is a composition comprising at least a cerium- and zirconium-based mixed oxide comprising zirconium, cerium, lanthanum and optionally at least one rare earth other than cerium and lanthanum, obtained by an advantageous process; the mixed oxide exhibiting a high thermal resistance and are in particular capable of maintaining a large specific surface area even in use in a high temperature environment. Also provided are a process for the synthesis of the compositions, a catalytic system, and a process for treatment of exhaust gasses.
Claims14
A composition comprising at least a cerium- and zirconium-based mixed oxide comprising zirconium, cerium, lanthanum and optionally at least one rare earth other than cerium and lanthanum;
- said mixed oxide exhibiting a specific surface area (SBET) comprised between 35 and 50 m2/g, after calcination at 1100° C. for 4 hours under air, wherein the composition is obtained by a process comprising in this order at least the following steps:
- (a) reacting a basic compound with an aqueous solution comprising at least a zirconium chloride salt, a cerium salt and optionally at least one rare earth salt, other than cerium salt and lanthanum salt, said aqueous solution containing sulphate anion (SO42−), to form a hydroxide precipitate;
- (b) separating off the precipitate from the liquid medium;
- (c) heating the precipitate obtained in step (b) in an aqueous medium and optionally in presence of lanthanum salt with a basic compound;
- (d) optionally adding lanthanum salt, optionally with a basic compound;
- (e) adding an organic texturing agent;
- (f) separating off the precipitate from the liquid medium;
- and
- (g) calcining the precipitate.
A composition comprising at least a cerium- and zirconium-based mixed oxide consisting of cerium, zirconium, lanthanum, and optionally at least one rare earth other than cerium and lanthanum;
- said mixed oxide exhibits a specific surface area (SBET) comprised between 35 and 50 m2/g, after calcination at 1100° C. for 4 hours under air, wherein the composition is obtained by a process comprising in this order at least the following steps:
- (a) reacting a basic compound with an aqueous solution comprising at least a zirconium chloride salt, a cerium salt and optionally at least one rare earth salt, other than cerium salt and lanthanum salt, said aqueous solution containing sulphate anion (SO42−), to form a hydroxide precipitate;
- (b) separating off the precipitate from the liquid medium;
- (c) heating the precipitate obtained in step (b) in an aqueous medium and optionally in presence of lanthanum salt with a basic compound;
- (d) optionally adding lanthanum salt, optionally with a basic compound;
- (e) adding an organic texturing agent;
- (f) separating off the precipitate from the liquid medium;
- and
- (g) calcining the precipitate.
Dependencies are inferred from the claim text.