The present invention provides an exhaust gas purifying catalyst including a first catalyst layer (12). The first catalyst layer (12) includes a first section (14) and a second section (15) in an exhaust gas flow direction, the first section (14) being located on an upstream side in the exhaust gas flow direction relative to the second section (15). The first section (14) and the second section (15) both contain a catalytically active component including a specific element. A concentration of the specific element is higher in the first section (14) than in the second section (15). A concentration gradient of the specific element contained in the first section (14) in a thickness direction of the catalyst layer (12) is milder than a concentration gradient of the specific element contained in the second section (15) in the thickness direction.

The present invention relates to a mixed oxide with enhanced resistance and NO.sub.x storage capacity. The mixed oxide may be used as a component of a NO.sub.x trap material in an exhaust system of an internal combustion engine. The invention also relates to a method for treating an exhaust gas from an internal combustion engine using the mixed oxide.

A mixed oxide, a catalytic composition, a catalytic wall-flow monolith, the use of the mixed oxide and the process of the preparation of the mixed oxide. The mixed oxide comprises zirconium, cerium, lanthanum and optionally at least one rare earth element other than cerium and other than lanthanum. The catalytic composition and the wall-flow monolith comprise the particles of the mixed oxide. The use of the mixed oxide is in the preparation of a coating on a filter. The process of preparation of the mixed oxide consists jet milling. The mixed oxide is a compromise between a calibrated size and a low viscosity when in the form of an aqueous slurry while retaining a high specific surface area and a high pore volume.

The present disclosure provides a method of forming a selective catalytic reduction (SCR) catalyst, the method including receiving a first iron-promoted zeolite having a first iron content, and treating the iron-promoted zeolite with additional iron in an ion exchange step to form a second iron-promoted zeolite with a second iron content, the second iron content being higher than the first iron content. A selective catalytic reduction (SCR) catalyst composition including an ironpromoted zeolite having at least about 6 weight percent iron, based on total weight of the ironpromoted zeolite, wherein the iron content of the zeolite was added to the zeolite in at least two separate steps is also provided herein.

The present disclosure relates a hydrogen-annealed bimetallic oxide of Formula I: A.sub.xO.sub.2—B.sub.yO.sub.z, wherein the A is a metal selected from Hf, Ti, or Zr; B is a metal selected from Ce, Zn, Fe or Co; x is in the range of 1-2; y is in the range of 1-4; and z is in the range of 1-6. The present disclosure further relates to a convenient process for preparing the hydrogen-annealed bimetallic oxide and a method for catalytically treating an exhaust stream is also disclosed herein.

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.

The present invention relates to a NOx storage material comprising a cerium-based mixed oxide comprising cerium, oxygen, and a first rare earth metal other than cerium, wherein said NOx storage material further comprises a second rare earth metal other than cerium; wherein said first rare earth metal is different to said second rare earth metal; and wherein said second rare earth metal is disposed or supported on the surface of the cerium-based mixed oxide.

Compositions, articles, and methods related to a three-way-catalyst composition comprising a perovskite-type compound of formula (I): La.sub.zB.sub.1-qB′.sub.qO.sub.3±δ or formula (II):[BO.sub.x].sub.y:[La.sub.zBO.sub.3±δ].sub.1-y and a non-redox active component; wherein B or B′ is Fe, Mn, Co, Ni, Cu, Ti, or Zr; q is in a range from about 0 to about 0.5; x is from about 1 to about 2.5; y is from about 1 to about 30 wt %; z is about 0.6 to about 1.1; δ is in a range from about 0 to about 0.6.

The present disclosure provides a catalyst for reducing CO and HC which is a core-shell particle including a core and a shell surrounding the core, the core includes metal oxide nanoparticles and noble metal nanoparticles fixed to the metal oxide nanoparticles, and the shell includes zirconia (ZrO.sub.2), and a layer from which the metal oxide is removed between the core and the shell is included.

A four-way conversion catalyst for treating a gasoline engine exhaust gas has a porous wall flow filter substrate with an inlet end, outlet end, substrate axial length extending between the inlet and outlet end, and passages defined by porous internal walls of the substrate, the passages having inlet passages with an open inlet and closed outlet, and outlet passages having a closed inlet and open outlet. The internal wall pores have a three-way conversion catalytic in-wall coating with an oxygen storage compound and a platinum group metal supported on a refractory metal oxide. On at least a portion of the internal wall surface defining the interface between the internal walls and the passages, the catalyst has a porous on-wall coating from the internal wall surface to the passage. The coating has porous oxidic compound and platinum group metal content of 0 to 0.001 wt. %, of the total coating weight.