A catalyst for decomposing an organic substance, the catalyst having a body which has a plurality of pores and the body contains a perovskite-type composite oxide represented by A.sub.xB.sub.yM.sub.zO.sub.w, where the A contains at least one selected from Ba and Sr, the B contains Zr, the M is at least one selected from Mn, Co, Ni, and Fe, 1.001x1.1, 0.05z0.2, y+z=1, and w is a positive value that satisfies electrical neutrality. The average pore diameter of the plurality of pores is 49 nm to 260 nm and the pore volume of each of the plurality of pores is 0.08 cm.sup.3/g to 0.37 cm.sup.3/g.

A honeycomb-structured catalyst for decomposing an organic substance, which includes a catalyst particle. The catalyst particle contains a perovskite-type composite oxide represented by A.sub.xB.sub.yM.sub.zO.sub.w, where the A contains at least of Ba and Sr, the B contains Zr, the M is at least one of Mn, Co, Ni, and Fe, y+z=1, 1.001x1.05, 0.05z0.2, and w is a positive value that satisfies electrical neutrality. The toluene decomposition rate is greater than 90% when toluene is decomposed using the honeycomb-structured catalyst subjected to a heat treatment at 1200 C. for 48 hours and a gas that contains 50 ppm toluene, 80% nitrogen, and 20% oxygen as a volume concentration as a target at a space velocity of 30,000/h and a catalyst temperature of 400 C.

A catalyst for gasoline engine exhaust gas after-treatment, comprising Pt and optionally at least one other platinum group metal on a hydrothermal stable support material which is coated onto a gasoline particulate filter. The catalyst oxidizes particulate matter trapped in the gasoline particulate filter under low temperature and abates NO.sub.x, CO and HC. Also a process for preparing the catalyst is disclosed, and a method for after-treatment of gasoline engine exhaust gas using the catalyst is disclosed.

An exhaust gas purifier is disposed in an exhaust gas passage of an engine, and includes: a DPF for capturing PM contained in exhaust gas; an SCR catalyst provided downstream of the DPF in a direction of flow of the exhaust gas, and for reducing NO.sub.x contained in the exhaust gas for purification in the presence of NH.sub.3; an inj ection unit provided between the DPF and the SCR catalyst, and for supplying urea to the SCR catalyst so as to supply NH.sub.3 to the SCR catalyst; and an AMOX provided downstream of the SCR catalyst in the direction of flow of the exhaust gas, and for removing NH.sub.3 having passed through the SCR catalyst. The DPF does not contain Pt or Pd, and contains Rh. The AMOX contains Pt.

Described are catalytic articles comprising a substrate having a washcoat on the substrate, the washcoat containing a catalytic component having a first average (D50) particle size and a functional binder component having a second average (D50) particle size in the range of about 10 nm to about 1000 nm, wherein the ratio of the first average (D50) particle size to the second average (D50) particle size is greater than about 10:1. The catalytic articles are useful in methods and systems to purify exhaust gas streams from an engine.

A phosphorus compound-containing exhaust gas purifying catalyst includes: a refractory three-dimensional structure extending from a gas inflow side end surface to a gas outflow side end surface, the refractory three-dimensional structure having cell walls that define and form multiple gas flow paths, the gas flow paths running from the gas inflow side end surface to the gas outflow side end surface; a lower catalyst layer that contains Pd and is formed continuously from the gas inflow side end surface on the cell walls; a gas inflow side upper catalyst layer that contains Rh and is located as an uppermost layer on the cell walls; and a gas outflow side upper catalyst layer that contains Rh and is located as an uppermost layer on the cell walls.

Provided is a catalyst article for simultaneously remediating the nitrogen oxides (NOx), particulate matter, and gaseous hydrocarbons present in diesel engine exhaust streams. The catalyst article has a soot filter coated with a material effective in the Selective Catalytic Reduction (SCR) of NOx by a reductant, e.g., ammonia.

An exhaust gas-purifying three-way catalyst containing: (i) base material particles of a Nd-solid dissolved zirconia-based complex oxide comprising Nd and Zr as constituent metal elements in the following mass proportions: TABLE-US-00001 ZrO.sub.2 50 to 75% by mass; and Nd.sub.2O.sub.3 25 to 50% by mass, in terms of oxides; and (ii) Pd catalyst particles supported on the base material particles, wherein the Nd-solid dissolved zirconia-based complex oxide further contains at least one or more rare earth elements selected from the group consisting of yttrium, scandium, lanthanum, and praseodymium, as a constituent metal element, in an amount of a total of more than 0% by mass to 20% by mass or less in terms of an oxide.

Described is a selective catalytic reduction catalyst comprising a zeolitic framework material of silicon and aluminum atoms, wherein a fraction of the silicon atoms are isomorphously substituted with a tetravalent metal. The catalyst can include a promoter metal such that the catalyst effectively promotes the reaction of ammonia with nitrogen oxides to form nitrogen and H.sub.2O selectively over a temperature range of 150 to 650 C. In another aspect, described is a selective catalytic reduction composite comprising an SCR catalyst material and an ammonia storage material comprising a transition metal having an oxidation state of IV. The SCR catalyst material promotes the reaction of ammonia with nitrogen oxides to form nitrogen and H.sub.2O selectively over a temperature range of 150 C. to 600 C., and the SCR catalyst material is effective to store ammonia at temperatures of 400 C. and above. A method for selectively reducing nitrogen oxides, and a method for simultaneously selectively reducing nitrogen oxide and storing ammonia are also described. Additionally, an exhaust gas treatment system is also described.

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.