Provided is a catalytic converter in which the entire catalyst constituting the catalytic converter can be efficiently utilized to purify exhaust gas, and the emission of hydrogen sulfide can be suppressed. A catalytic converter 10 includes catalyst layers 2A, 2B formed of a noble metal catalyst that are formed on cell wall surfaces of a substrate 1 having a cell structure in a longitudinal direction of the substrate 1 in which gas flows, in which the substrate 1 has a center region 1A having a relatively high cell density and a peripheral region 1B having a relatively low cell density, and lengths of the catalyst layers 2A, 2B of the center region 1A and the peripheral region 1B in the longitudinal direction are the same as each other, or the length of the catalyst layer 2B in the longitudinal direction is shorter than that of the catalyst layer 2A.

A catalytic system is provided which comprises a tubular reactor and at least one catalyst particle located within the tubular reactor. The catalyst particles have a particular geometric form which promotes heat transfer with the tubular reactor. Certain specific catalyst particles are also provided.

The present disclosure relates to an exhaust gas control catalyst including a base and a catalyst coating layer having a two-layer structure on the base. The catalyst coating layer includes a lower layer on the base, and an upper layer on the lower layer. The upper layer of the catalyst coating layer contains Rh particles in which a mean particle diameter measured by observation using a transmission electron microscope is 1.0 nm or more and 2.0 nm or less and a particle-diameter standard deviation σ is 0.8 nm or less. A length of the upper layer from an end face on a downstream side in an exhaust gas flow direction falls within a range of 70% or more and 100% or less of a total length of the base.

The present invention relates to a method for producing a platinum-based alloy powder, the method comprising a heat treatment of a mixed powder containing a platinum-based powder composed of at least one selected from the group consisting of platinum and platinum compound, a platinum group metal-based powder composed of at least one selected from the group consisting of iridium, rhodium, palladium, and compound containing at least one of them, and an alkaline-earth metal compound, wherein specific surface area of the platinum group metal-based powder is 30 m.sup.2/g or more and D90 of the mixed powder is 1.0 μm or less. According to the method for producing a platinum-based alloy powder of the invention, it is possible to produce a platinum-based alloy powder that has a desired particle diameter, also has a sharp particle size distribution, and has high purity and crystallinity.

The present invention relates to a high-performance polyoxometalate catalyst and a method of preparing the same. More particularly, the present invention provides a high-performance polyoxometalate catalyst, the activity and selectivity of which may be improved by controlling the content of vanadium and the like and which has superior reproducibility and may unsaturated carboxylic acid from unsaturated aldehyde in a high yield for a long time, a method of preparing the same, and the like.

The present invention provides materials for improving the ignition of gaseous reactants in metal catalyzed oxidation reactions comprising a metal catalyst gauze, preferably, a platinum/rhodium catalyst gauze, having in contact therewith, from 0.25 to 1.5 wt. %, based on the weight of the metal catalyst gauze, of one or more pieces of previously used metal catalyst gauze. Further, methods of making the metal catalyst materials comprise shaping the pieces of previously used metal catalyst gauze and placing them equidistant from each other in contact with or on the surface of the metal catalyst gauze. And methods of using the materials comprise feeding into the reactor a gas mixture of oxygen or air and one or more reactant gases, and igniting the gas mixture at the surface of one or more or all of the pieces of previously used metal catalyst.

The present disclosure provides an exhaust gas purification material and an exhaust gas purification device that can efficiently remove harmful components even after being exposed to high temperature. Such exhaust gas purification material comprises metal oxide particles and noble metal particles supported on the metal oxide particles. The noble metal particles have a particle size distribution with a mean of 1.5 nm and 18 nm and a standard deviation of less than 1.6 nm.

The invention relates to a catalyst system for reducing nitrogen oxides, which comprises a nitrogen oxide storage catalyst and an SCR catalyst, wherein the nitrogen oxide storage catalyst consists of at least two catalytically active washcoat layers on a supporting body, wherein a lower washcoat layer A contains cerium oxide, an alkaline earth compound and/or alkali compound, as well as platinum and palladium, and an upper washcoat layer B, which is arranged over the washcoat layer A, contains cerium oxide, platinum and palladium, and no alkali compound and no alkaline earth compound. The invention also relates to a method for converting NOx in exhaust gases of motor vehicles that are operated by means of engines that are operated in a lean manner.

A supported catalyst having rhodium particles with an average diameter of less than 1 nm disposed on a support material containing magnetic iron oxide (e.g. Fe.sub.3O.sub.4). A method of producing the supported catalyst and a process of reducing nitroarenes to corresponding aromatic amines employing the supported catalyst with a high product yield are also described. The supported catalyst may be recovered with ease using an external magnet and reused.

An oxidation catalyst composite for abatement of exhaust gas emissions from a lean burn engine is provided, the catalyst composite including a carrier substrate having a length, an inlet end and an outlet end, and an oxidation catalyst material coated on the carrier substrate. The oxidation catalyst material can include a first layer and a second layer. The first layer can include a first oxygen storage component that includes ceria and is impregnated with a palladium (Pd) component and a second component including one or more of magnesium (Mg), rhodium (Rh), and platinum (Pt). The second layer can include a refractory metal oxide component impregnated with platinum (Pt) and palladium (Pd), wherein the ratio of Pt to Pd is in the range of about 0:10 to about 10:0.