A catalyst for abating a nitrogen oxide includes: a honeycomb substrate including a plurality of cell passages partitioned by a cell barrier rib; and a coating layer positioned on the internal side of the cell passages. The coating layer includes a support including Mg-substituted alumina (MgAl.sub.2O.sub.4), ceria (Ce), and a composite ceria; and Ba and a noble metal catalyst selected from the group consisting of Pt, Pd, Rh and combinations thereof, which are supported on the support. Also provided is a catalyst system for abating a nitrogen oxide includes the coating layer.

When sizes of particles supporting a catalyst metal remain relatively large but sizes of particles not supporting a catalyst metal are minimized among metal oxide particles included in a catalyst coating layer, it is possible to decrease a thickness of the catalyst coating layer while maintaining durability and improve gas diffusibility of the coating layer. Therefore, a thickness of the catalyst coating is decreased without decreasing durability and a catalyst can exhibit high exhaust gas purification performance even under high load conditions.

A catalyst converter includes: a substrate (1) having a cell structure formed of a center area (1A) having the highest cell density, a peripheral area (1C) having the lowest cell density, and an intermediate area (1B) having the cell density between that of the center area and that of the peripheral area; a first catalyst layer formed in the center area (1A); a second catalyst layer formed in the intermediate area (1B); and a third catalyst layer formed in the peripheral area (1C). A length in a longitudinal direction of the second catalyst layer is longer than that of the first catalyst layer. A length in the longitudinal direction of the third catalyst layer is longer than that of the second catalyst layer. A ratio of the length in the longitudinal direction of the first catalyst layer to the length of the substrate is 65% or more.

This honeycomb catalyst is provided with a honeycomb unit in which a plurality of through holes are arranged in parallel in a longitudinal direction with being separated by partition walls, wherein the honeycomb unit contains a zeolite and an inorganic binder, the zeolite satisfies all of conditions (A) to (D): (A) having a CHA structure in which the composition ratio of SIO.sub.2/Al.sub.2O.sub.3 is less than 15; (B) having Cu being carried by 3.5 to 6.0 wt % with respect to zeolite; (C) having an average particle diameter of 0.05 to 1 μm; and (D) being contained by 150 to 350 g/L with respect to the whole of the honeycomb unit, and excellent NOx purifying performance, reduction of water absorption and displacement, and inhibition of crack occurrence can be exerted.

The honeycomb structure includes a honeycomb structure body made of a zeolite material containing at least a coarse particle zeolite having a large average particle diameter (coarse zeolite particles). A fine particle zeolite having an average particle diameter smaller than that of the coarse particle zeolite (fine zeolite particles), and an inorganic bonding material, the coarse particle zeolite (the coarse zeolite particles) is a chabazite type zeolite in which an average particle diameter of primary particles is 2 μm or more and 6 μm or less, and in the fine particle zeolite (the fine zeolite particles), an average particle diameter of primary particles is 0.02 μm or more and smaller than 2 μm, and in the zeolite material which is comprised the honeycomb structure body, a ratio of a volume of pores having pore diameters of 0.02 to 0.15 μm to a volume of all pores is 42% or less.

[Summary]

[Problem]

The problem addressed by the present invention lies in providing an exhaust gas purification filter which can efficiently treat particulate matter in exhaust gas.

[Solution]

The present invention provides an exhaust gas purification filter including a substrate comprising a plurality of porous partitions, wherein the partitions form an exhaust gas flow path, a porous catalytic layer is provided on the partitions and the catalytic layer having a thickness of 10 μm or greater is provided over at least 20% of the total length of the partitions in the lengthwise direction thereof, and the catalytic layer having a thickness of 10 μm or greater is not present on the partitions 15 mm from an outflow side.

Hydrocarbon (HC) traps are disclosed. The HC trap may include a first zeolite material having an average pore diameter of at least 5.0 angstroms and configured to trap hydrocarbons from an exhaust stream and to release at least a portion of the trapped hydrocarbons at a temperature of at least 225° C. The HC trap may also include a second zeolite material having an average pore diameter of less than 5.0 angstroms or larger than 7.0 angstroms. One or both of the zeolite materials may include metal ions, such as transition, Group 1A, or platinum group metals. The HC trap may include two or more discrete layers of zeolite materials or the two or more zeolite materials may be mixed. The multiple zeolite HC trap may form coke molecules having a relatively low combustion temperature, such as below 500° C.

A core-shell oxide material comprises: a core which comprises a ceria-zirconia based solid solution powder having at least one ordered phase of a pyrochlore phase and a κ phase; and a shell which comprises an alumina based oxide disposed on at least a portion of a surface of the core.

A honeycomb structure has partition walls defining a plurality of polygonal cells which become through channels for a fluid, a structure end face vertical to an axial direction has at least two cell regions possessing mutually different cell structures and surrounded by circumferential portions, and in the cell regions adjacent to each other, to first partition walls of a first cell structure of one first cell region, second partition walls of a second cell structure of the other or second cell region are tilted.

An exhaust gas-purifying catalyst material includes first oxide particles having an average particle diameter D.sub.av of 1 μm to 95 μm and having an oxygen storage capacity, second oxide particles having an average particle diameter D.sub.av of 0.05 μm to 0.5 μm, containing a metal element, and having no oxygen storage capacity, precious metal particles, and acidic oxide particles. The material has a correlation coefficient ρ of 0.45 or more obtained using first characteristic X-ray intensity for the metal element contained in the second oxide particle, second characteristic X-ray intensity for an element other than oxygen contained in the acidic oxide particle, and third characteristic X-ray intensity for a precious metal element contained in the precious metal particle.