Anan Kasei Co., Ltd.

Rhodia Operations

Bernard Pacaud

Emmanuel Rohart

Eisaku Suda

Olivier Larcher

Stephan Verdier

Shigeru Aozasa

Hirofumi Takemori

Lianxin Dai

Catalyst compositions for the treatment of vehicular exhaust gases are based on zirconium and cerium oxides, have a cerium oxide content of at most 50% by weight, a level of reducibility of at least 95% after calcination in air at 600&#xb0;, and a specific surface area after calcination for 4 hours at 1100&#xb0; of at least 15 m/g; such compositions are prepared by forming an aqueous mixture containing zirconium and cerium compounds, by heating this mixture to at least 100&#xb0; and, after the heating, adjusting it to a basic pH, by adding a surfactant additive to the precipitate obtained from this mixture and by calcinating the precipitate in an inert gas or under vacuum at a temperature of at least 900&#xb0; and then in an oxidizing atmosphere at a temperature of at least 600&#xb0;.

Catalyst compositions for the treatment of vehicular exhaust gases comprise zirconium oxide and cerium oxide, and have a high reducibility and a stable specific surface area

The present invention relates to ceric oxide that has excellent heat resistance and oxygen absorbing and desorbing capability useful as a co-catalyst material suitable for a catalyst for purifying exhaust gas, that is capable of maintaining a large specific surface area even in use in a high temperature environment, and that is suitable for use in a high temperature environment, yet capable of exhibiting high oxygen absorbing and desorbing capability also in a lower temperature range, a method for preparing such ceric oxide, and a catalyst for purifying exhaust gas utilizing such ceric oxide. The ceric oxide is an oxide composed essentially of ceric oxide, and has a specific surface area of not smaller than 30.0 m/g after calcination at 900&#xb0; C. for 5 hours.

Ceric oxide and method for production thereof, and catalyst for exhaust gas clarification

The invention provides a cerium based composite oxide and its production method, which hardly forms aggregates, is composed of particular acicular particles providing sinterable ceramic materials, has a sharp particle size distribution, and inhibited from aggregating. The composite oxide contains 0.1&#x2013;50 mol % of metal such as Y, Sc, or rare earth elements excluding Ce and Pm, in terms of oxides, and 50 to 99.9 mol % of cerium in terms of oxides, wherein the composite oxide takes the acicular primary particle form having an average aspect ratio of 1.05&#x2013;10.0, or secondary particle form, aggregates of the primary particles. The composite oxide containing the primary and second particles have a BET specific surface area of 5 to 40 m/g, an average particle size of 0.1 to 0.5 &#x3bc;m, and a particle size distribution index represented by formula (1) of not higher than 1.6:Particle Size Distribution Index=(84&#x2212;16)/(2&#xd7;50).&#x2003;&#x2003;(1)

Cerium based composite oxide, sintered product thereof and method for preparation thereof

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Nishinomiya, Japan

Bernard Pacaud