Rhone-poulenc Chimie

Rhodia Chimie

Olivier Touret

Thierry Chopin

Lionel Bonneau

Gabriel Vilmin

Gilbert Blanchard

Thierry Birchem

Michele Pijolat

Pierre Macaudiere

Eric Quemere

Marie Prin

Jacques Lemaire

Maryline Aubert

Denis Petta

Alain Bouruetaubertot

Valerie Visciglio

Herve Guichon

Pierre MacAudiere

Michel Soustelle

Composition based on zirconium oxide and cerium oxide, preparation method therefor and use thereof

Storage-stable colloidal organic sols comprise suspended tetravalent metal oxide particulates in an organic diluent medium, notably cerium dioxide particulates, the tetravalent metal oxide particulates having a particle size d,no greater than 200 nanometers and being complexed with at least one amphiphilic organic acid, and either said tetravalent metal oxide particulates comprising agglomerates of crystallites, the d,of which being no greater than 5 nanometers and at least 90% of said agglomerates comprising from 1 to 5 crystallites, and/or said at least one amphiphilic organic acid has from 11 to 50 carbon atoms and is branched in at least one of the &agr;-, &bgr;-, &ggr;- or &dgr;-positions relative to the atom bearing the acidic hydrogen.

Colloidal organic sols comprising tetravalent metal oxide/organic acid complexes

Organic sol comprising at least one oxygenated rare-earth compound,

Vehicular emissions are reduced/purified via combustion of the hydrocarbon fuel therefor, e.g., diesel fuel, in the presence of a cerium compound, preferably a cerium (IV) compound, to produce soots having depressed ignition temperatures that contain effective purifying amounts of aggregates of ceric oxide crystallites, the largest particle size dimension of which ranging from 50 .ANG. (5 nanometers) to 10,000 .ANG. (1,000 nanometers) and the crystallite sizes of which, measured by Debye-Scherrer technique, ranging from 50 .ANG. (5 nanometers) to 250 .ANG. (25 nanometers).

Aggregates of ceric oxide crystallites and reduction of vehicular

Colloidal dispersions of finely divided particulates, well suited for the production of catalysts for the catalytic conversion of exhaust gases emanating from internal combustion engines, notably vehicular exhaust gases, comprise at least one rare earth compound and, optionally, at least one compound of at least one other element selected from among those of groups IVa, VIIa, VIII, Ib, IIb, IIIb and IVb of the Periodic Table, said particulates being at least 50% dispersible in water.

Dispersible rare earth compositions and colloidal suspensions/catalysts

Catalytic composition comprising a mixture of cerium oxide with

The invention relates to new compositions based on ceric oxide having an improved oxygen storage capacity, these compositions being characterized in that they contain, besides ceric oxide, at least one oxide of another metallic element M chosen from the group consisting of iron, bismuth, nickel, tin and chromium or one of their mixtures, this oxide preferably being in solid solution with the abovementioned cerium oxide. The process of synthesis of these compositions consists in first of all preparing an intimate mixture between (i) a ceric oxide or a ceric hydroxide and (ii) at least one additive consisting of a hydroxide or a salt, thermally decomposable to an oxide, of the metallic element M, and in then calcining this mixture so as to obtain the desired composition based on oxides. The compositions according to the invention are particularly useful in the manufacture of catalysts and/or catalyst supports, especially those intended for treating exhaust gases from internal combustion engines.

Composition based on ceric oxide, preparation and use

Composition precursor and mixed cerium and zirconium oxide-based

Thermally stable/highly reducible catalyst compositions, well suited for the catalytic conversion of exhaust gases emanating from internal combustion engines notably vehicular exhaust gases, comprise alumina, the oxides of cerium praseodymium and zirconium, and, optionally, at least one other oxide of bismuth, of a rare earth, or of an element of group VIII of the Periodic Table, and exhibit a stabilized hydrogen-absorption capacity up to a temperature of at least 1,000.degree. C.

Thermally stable/highly reducible catalyst compositions comprising

Cerium/zirconium mixed oxides (optionally including yttrium values), comprising solid solutions thereof, having contents of zirconium of up to 60 atom % and having thermally stable, very high specific surface areas at least greater than 80 m.sup.2 /g, preferably at least 100 m.sup.2 /g and more preferably at least 150 m.sup.2 /g, are well suited as catalysts and/or catalyst supports, notably for the treatment/conversion of vehicular exhaust gases; such Ce.sub.x Zr.sub.1-x O.sub.2 particulates are conveniently prepared by thermally treating an aqueous solution of soluble compounds of cerium and zirconium (and optionally yttrium), e.g. the nitrates thereof, present in the desired stoichiometric amounts, and thence recovering and, if appropriate, calcining the reaction product thus formed.

Cerium/zirconium mixed oxide catalysts having high/stable specific

Process for the catalytic conversion of exhaust gases using

Ceric oxide (ceria) particulates exhibiting a particularly small crystallite size, well suited for catalyst/catalyst carrier applications, include a specific surface-stabilizing amount of silicon values (preferably less than 1% by weight thereof, expressed as SiO.sub.2) and have a specific surface of at least 40 m.sup.2 /g after calcination at 800.degree. C. for 6 hours and of at least 20 m.sup.2 /g after calcination at 1,000.degree. C. for 6 hours; such CeO.sub.2 particulates are advantageously prepared by (a) suspending certain ceric hydroxides in a basic aqueous reaction medium containing a silicon compound, (b) autoclaving the resulting suspension, (c) cooling and depressurizing such medium of reaction, (d) separating a ceric hydroxide therefrom, and (e) calcining the ceric hydroxide thus separated.

B.E.T. specific surface-stabilized ceria

Porous alumina-based compositions having high specific surface areas, well adopted for catalyst applications and prepared by precipitation/hydrothermal treatment/calcination technique, comprise an alumina matrix having from 10% to 50% by weight of at least one rare earth or alkaline earth metal second element dispersed therein, having a pore volume, corresponding to pores of a diameter less than 100 nm, ranging from 1.2 cm.sup.3 /g, at least 80% of which corresponding to pores having a diameter ranging from 10 nm to 100 nm, after heat treatment at a temperature of 350.degree. C. and having a pore volume, also corresponding to pores of a diameter less than 100 nm, ranging from 0.6 cm.sup.3 /g to 1.5 cm.sup.3 /g, at least 90% of which corresponding to pores having a diameter ranging from 20 nm to 100 nm, after heat treatment at a temperature of 1,200.degree. C. for four hours.

Alumina-based compositions and catalysts having high specific surface

Unique compositions based on at least one crystalline rare earth sesquisulfide, well suited for the coloration of a wide variety of substrates, e.g., cosmetics, plastics, paints and rubbers, contain a dopant amount of at least one alkali/alkaline earth metal, at least a fraction of which being included within the crystal lattice of such at least one rare earth sesquisulfide.

Rare earth sesquisulfide compositions comprising alkali/alkaline earth

Thermally stable ceric oxide-based compositions, well suited as catalysts/catalyst supports for a wide variety of reactions, notably for the catalytic conversion of exhaust gases emanating from internal combustion engines, comprise particulates of immixture of a major amount of ceric oxide with at least one other metal oxide of magnesium, gallium, boron, scandium, or mixture thereof, and having a specific surface greater than 10 m.sup.2 /g after calcination at 800.degree. C.

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La Rochelle, France

Olivier Touret