In relation to a Cu-based delafossite-type oxide that is effective as an exhaust gas purification catalyst, Cu is placed in a high catalytic activity low-valence state, whereby a novel Cu-based delafossite-type oxide having higher activity than in the past is provided. Proposed is a delafossite-type oxide for an exhaust gas purification catalyst that is represented by a general formula ABO.sub.2, wherein Cu and Ag are contained in the A site of the general formula, one or two or more elements selected from the group consisting of Mn, Al, Cr, Ga, Fe, Co, Ni, In, La, Nd, Sm, Eu, Y, V, and Ti are contained in the B site of the general formula, and Ag is contained at a ratio of 0.001 at. % or more and less than 20 at. % in the A site of the general formula.

This disclosure is directed to catalyst compositions, catalytic articles for purifying exhaust gas emissions and methods of making and using the same. In particular, the disclosure relates to a catalytic article including a catalytic material on a substrate, wherein the catalytic material has a first layer and a second layer. The first layer provides effective lean NO.sub.x trap functionality and the second layer provides effective three-way conversion of carbon monoxide, hydrocarbons, and nitrogen oxides (NO.sub.x).

An exhaust gas cleaning catalyst is provided with a fire-resistant three-dimensional structural body, a first catalyst layer provide on a first surface side of the fire-resistant three-dimensional structural body, and a second catalyst layer provided on a side of the first catalyst layer opposite to the fire-resistant three-dimensional structural body. The first catalyst layer contains: a complex oxide including cerium and zirconium; and elemental rhodium. The second catalyst layer contains: a complex oxide including cerium and zirconium; and elemental palladium. The amount of cerium included in the second catalyst layer, in terms of cerium dioxide, is 10-25 g per liter of the fire-resistant three-dimensional structural body.

Provided is a catalyst device that makes it possible to efficiently purify exhaust gas. A catalyst device that comprises: a carrier that is formed by stacking and rolling a metal-foil-shaped flat plate and a metal-foil-shaped corrugated plate and that carries a catalyst; and an outer cylinder that houses the carrier and supports the carrier such that one end part of the carrier is oriented toward an exhaust gas upstream side and another end part of the carrier is oriented toward an exhaust gas downstream side. The flat plate and the corrugated plate have a plurality of holes and are covered by a coating film that includes a catalyst substance. The coating film that covers the downstream side of the holes is thicker than the coating film that covers the upstream side of the holes.

A Pd-supporting Zr-based composite oxide wherein by having a Zr-containing composite oxide support and Pd supported thereon and by showing, upon XAFS (X-ray absorption fine structure) analysis, a maximum peak in a Pd bond distance range of 2.500-3.500 Å, the maximum peak being located in a position of 3.050-3.110 Å.

A novel catalyst constituent material for combustion gas purification, which has an extremely good ratio of contact between each catalyst metal particle and an exhaust gas; and catalyst device which uses this catalyst constituent material for combustion gas purification; and a method for producing this catalyst constituent material for combustion gas purificaton. The catalyst constituent obtained by mixing catalyst metal particles and a pore-forming material that disappears at high temperatures into a catalyst supporting material which is a slurry containing fine ceramic particles. The pore-forming material also contains long fibers of cellulose nanofibers and/or short fibers of cellulose nanofibers.

A three-way catalyst article, and its use in an exhaust system for internal combustion engines, is disclosed. The catalyst article for treating exhaust gas comprising: a substrate comprising an inlet end and an outlet end with an axial length L; a first catalytic region comprising a first platinum group metal (PGM) component and a first oxygen storage capacity (OSC) material, wherein the first OSC material has a fresh specific surface area (SSA) of at least 10 m.sup.2/g; and wherein the first OSC material has an SSA difference of no more than 30 m.sup.2/g between the fresh first OSC material and the aged first OSC material.

A method for manufacturing a catalyst includes depositing a catalyst slurry containing at least a catalyst metal and water on a support, depositing particles of a water-absorbing polymer on a surface of the catalyst slurry, expanding the particles to a predetermined size with the water present in the catalyst slurry, and firing the support having the catalyst slurry and the particles deposited on the catalyst slurry.

A ceria-zirconia-based composite oxide oxygen storage material with a fast oxygen storage rate having an OSC ability enabling fast response to changes in exhaust gas which does not greatly fluctuate in composition, but varies at a fast rate near the stoichiometric air-fuel ratio, an exhaust gas purification catalyst, and a honeycomb structure for exhaust gas purification are provided. A ceria-zirconia-based composite oxide oxygen storage material, which oxygen storage material has a molar ratio of cerium and zirconium, by cerium/(cerium+zirconium), of 0.33 to 0.90, has an ion conductivity measured by an AC impedance method of 1×10.sup.−5S/cm or more at 400° C., and contains metal ions M of one or more types of rare earth elements selected from Sm.sup.3+, Eu.sup.3+, Pr.sup.3+, Gd.sup.3+, and Dy.sup.3+ with a coordination number of over 7.0 in an amount of 0.5 mol % to 15 mol % with respect to the total amount of cations.

A process for removing hydrocarbons from a feed stream containing hydrocarbons includes introducing ozone to the feed stream to produce an ozone doped stream containing ozone and hydrocarbons, and contacting the ozone doped stream with a supported metal catalyst at a temperature of from 100° C. to 300° C. to produce a treated stream, wherein the supported metal catalyst comprises iron supported on a support selected from aluminosilicates, silica-aluminas, silicates and aluminas. A process for removing NOx from a feed stream containing NOx, and an apparatus for removing hydrocarbons and/or NOx from a feed stream containing hydrocarbons and/or NOx are also provided.