Abstract:
Provided is a catalyst composition capable of preventing decrease in catalytic activity due to grain growth of noble metal under high temperature or under change in oxidation reduction or further for long term use, and of achieving excellent catalytic activity over a long time. The catalyst composition containing a composite oxide represented by the following general formula (1): €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒAO·x(B 2-y C y O 3-± )€ƒ€ƒ€ƒ€ƒ€ƒ(1) (wherein A represents an element selected from monovalent elements, divalent elements and lanthanides; B represents a trivalent element; and C represents a noble metal; x represents an integer of 1 to 6; y represents an atomic ratio satisfying the following relation: 0
Abstract:
The exhaust gas purifying catalyst disclosed here includes a substrate 10 and a catalyst coat layer 30 formed on the surface of the substrate 10. The catalyst coat layer 30 is formed in a laminate structure having two layers, with a first layer 34 being nearer to the surface of the substrate 10 and a second layer 32 being relatively further from this surface. The second layer 32 includes a carrier and a noble metal supported on the carrier. The first layer 34 is a noble metal-free layer that does not contain a noble metal but does contain an OSC material having oxygen storage capacity.
Abstract:
The exhaust gas-purifying catalyst of the invention contains oxide particles having interdispersed therein A crystallites that are loaded with a noble metal and B crystallites that are not loaded with a noble metal. The A crystallites loaded with a noble metal are composed of an oxide containing at least one of zirconium (Zr) and cerium (Ce). The B crystallites not loaded with a noble metal are composed of a cerium (Ce)-containing oxide which has a higher Ce content (mol %) than the oxide making up the A crystallites. The oxide particles have a specific surface area after 5 hours of heat treatment at 1,150°C in open air of 30 m 2 /g or more.
Abstract:
An exhaust gas-purifying catalyst 1 which offers high exhaust gas purification performance is achieved. The exhaust gas-purifying catalyst 1 includes a first oxide particle 10 with an oxygen storage capacity, one or more second oxide particles 20 partially or entirely covering a surface of the first oxide particle 10 and having an oxygen storage capacity lower than that of the first oxide particle 10, an average particle diameter D av of the one or more second oxide particles 20 being smaller than that of the first oxide particle 10, and precious metal particles 30 supported on at least one of the second oxide particles 20.
Abstract:
Catalyst compositions containing novel perovskite-type double oxides permitting reversible entrance and exit of noble metals, namely, catalyst compositions containing perovskite-type double oxides represented by the general formula (1): AxA’wByB’(1-y-z)NzO3±σ wherein A is at least one element selected from among alkaline earth metals; A’ is at least one element selected from among rare earth elements; B is a tetravalent rare earth element; B’ is at least one element selected from among transition elements (except tetravalent rare earth elements, Rh, Pd and Pt); N is at least one element selected from among Rh, Pd and Pt; x and w are atomic ratios satisfying the relationships: 0.8
Abstract:
Disclosed is an exhaust gas purifying catalyst (1) containing a rare earth element, an alkaline earth element, zirconium and a noble metal. The atomic ratio of the alkaline earth element relative to the sum of the rare earth element and zirconium is not less than 10 at%. A part of the rare earth element and a part of zirconium form a complex oxide together with at least a part of the alkaline earth element, and this complex oxide and a part of the noble metal form a solid solution.
Abstract:
The exhaust gas-purifying catalyst 10 of the invention includes a noble metal 20, and crystallites 30 that form CZ composite metal particles which serve as a carrier supporting the noble metal and contain at least zirconium (Zr) and cerium (Ce). The CZ composite oxide particles (crystallites) 30 further contain crystal growth-suppressing fine particles 40 which are fine metal particles comprising primarily a metallic element M that melts at 1,500°C or above and which suppress crystal growth by the CZ composite oxide particles. The content of the metallic element M included in the CZ composite oxide particles 30, expressed in terms of the oxide thereof, is 0.5 mol % or less of the total oxide.