A nanocrystal-sized cerium-zirconium-aluminum mixed oxide material includes at least 20% by mass zirconium oxide; between 5% to 55% by mass cerium oxide; between 5% to 60% by mass aluminum oxide; and a total of 25% or less by mass of at least one oxide of a rare earth metal selected from the group of lanthanum, neodymium, praseodymium, or yttrium. The nanocrystal-sized cerium-zirconium-aluminum mixed oxide exhibits hierarchically ordered aggregates having a dso particle size less than 1.5 μm, and retains at least 80% of surface area and pore volume after ageing at temperature higher than 1000° C. for at least 6 hours. The nanocrystal-sized cerium-zirconium-aluminum mixed oxide material is prepared using a co-precipitation method followed by milling the dried and calcined oxide material. The nanocrystal-sized cerium-zirconium-aluminum mixed oxide material forms a particulate filter that may be used in an exhaust system arising from a gas or diesel engine

An exhaust gas purification filter is used so as to support a NO.sub.X purification catalyst. The exhaust gas purification filter includes a honeycomb structure portion and a plug portion. The honeycomb structure portion includes a partition wall and cells. Numerous pores are formed in the partition wall. The cells are partitioned by the partition walls and form a flow path for an exhaust gas. The plug portion alternately seals an inflow end surface or an outflow end surface for the exhaust gas in the cells. The partition wall has a gas permeability coefficient that is equal to or greater than 0.35×10.sup.−12 m.sup.2, a pore volume ratio of pore diameters of 9 μm or less that is equal to or less than 25%, and an average pore diameter that is equal to or greater than 12 μm.

Provided is an exhaust gas purifying filter used with a HC purifying catalyst supported thereon. Numerous pores are formed in partitions of the exhaust gas purifying filter. In a cross-section of the partition, pores are open at a passage surface, having an open end of which the opening diameter is 50 μm or larger. In the cross-section of the partitions, the partitions include a narrow part where a pore diameter is 5 μm or more and the pore diameter becomes a minimum in a region. In the cross-section of the partitions, the region is positioned between a pair of virtual lines L.sub.1 and L.sub.2 extending from opposing sides of the opening end to a passage surface positioned opposite to the opening end along the wall thickness direction X, Z. The pore diameter at the narrow part is 6% or more and less than or equal to 20% of the opening diameter.

The present disclosure provides a monolith substrate used for an exhaust gas purifying catalyst that improves purification performance, a method for producing such monolith substrate, and an exhaust gas purifying catalyst comprising such monolith substrate. The present disclosure relates to a monolith substrate comprising an alumina-ceria-zirconia composite oxide and alumina, a method for producing such monolith substrate, and an exhaust gas purifying catalyst comprising such monolith substrate.

Catalyst regeneration processes that include measures for controlling emissions generated during the regeneration are described. The present invention further relates to catalytic processes for producing various chlorinated aromatic compounds that include provisions for controlling emissions during catalyst regeneration.

The invention provides a process for preparing a methane oxidation catalyst, a methane oxidation catalyst thus prepared and a method of oxidizing methane.

In order to provide an exhaust gas purification catalyst capable of purifying hydrocarbons, carbon monoxide, and nitrogen oxides in exhaust gas at low temperatures, the exhaust gas purification catalyst according to the present invention includes: a region (2) containing palladium and yttrium on a three-dimensional structure (1), and a first region (3) and a second region (4) provided on the region (2) in order from an inflow side of exhaust gas to an outflow side of exhaust gas. The concentration of yttrium contained in the first region (3) and/or the second region (4) is higher than the concentration of yttrium contained in the region (2).

Systems are provided for a diesel oxidation catalyst. In one example, the diesel oxidation catalyst comprises a washcoat with different catalytically active portions for reacting with one or more of carbon containing compounds and NO.sub.x. The diesel oxidation catalyst is located upstream of a particulate filter in an exhaust passage.

An exhaust gas purification catalyst device has catalyst coating layers, which extend from the upstream side to the downstream side of the exhaust gas flow. The catalyst coating layers each have at least three zones present in order from the upstream side to the downstream side of the exhaust gas flow, and each of these at least three zones is an oxidation catalyst zone or a reduction catalyst zone. In the uppermost layer of an oxidation catalyst zone, the total number of atoms of platinum and palladium is greater than the number of atoms of rhodium; in the upper most layer of a reduction catalyst zone, the number of atoms of rhodium is greater than the total number of atoms of platinum and palladium. The oxidation catalyst zones and the reduction catalyst zones alternate at least twice in the exhaust gas flow direction.

The invention relates to a three-way catalytic converter, which is suitable, in particular, for the removal of carbon monoxide, hydrocarbons and nitrogen oxides out of the exhaust gas of combustion engines operated with stoichiometric air-fuel mixture. The three-way catalytic converter is characterized in that it has a high oxygen storage capacity after aging and consists of at least two catalytically active layers.