An object of the present invention is to provide means for improving the hydrogen generation properties of a hydrogen-producing catalyst. A hydrogen-producing catalyst according to one aspect of the present invention comprises Rh and a composite containing Al, Ce, and Zr. When a ratio of the number of Al atoms to the number of Ce atoms (Al/Ce) in the composite measured by X-ray fluorescence (XRF) analysis is R.sub.1 and a ratio of the number of Al atoms to the number of Ce atoms (Al/Ce) in the composite measured by an X-ray photoelectron spectroscopy (XPS) method is R.sub.2, a value of R.sub.2/R.sub.1 is greater than 2.25 and less than 5.92.

The present disclosure provides catalyst compositions capable of reducing nitrogen oxide (NO.sub.x) emissions in engine exhaust, catalyst articles coated with such compositions, and processes for preparing such catalyst compositions and articles. The catalyst compositions include metal ion-exchanged zeolites useful for selective catalytic reduction (SCR) of NO.sub.x. Further provided is an exhaust gas treatment system including such catalytic articles, and methods for reducing NO.sub.x in an exhaust gas stream using such catalytic articles.

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.

A NOx adsorber catalyst for treating an exhaust gas from a diesel engine. The NOx adsorber catalyst comprises a first region comprising a NOx adsorber material comprising a first molecular sieve catalyst. The first molecular sieve catalyst comprises a first noble metal and a first molecular sieve, and the first molecular sieve contains the noble metal. The first molecular sieve has an STI Framework Type.

The present disclosure is directed to an emission treatment system for oxidation of hydrocarbons and carbon monoxide and for NO.sub.x abatement in an exhaust stream of a lean burn engine, the emission treatment system including a low-temperature NO.sub.x adsorber (LT-NA) that includes a molecular sieve impregnated with at least one PGM component positioned in fluid communication with the exhaust stream; and an oxidation catalyst that includes a refractory metal oxide support containing manganese impregnated with platinum positioned in fluid communication with the exhaust stream, each of the LT-NA and the oxidation catalyst being disposed on a substrate. The invention provides a catalyst article combining an oxidation catalyst with a LT-NA and a related method of treatment of an exhaust gas.

The present disclosure is directed to Low Temperature NOx-Absorber (LT-NA) catalyst compositions, catalyst articles, and an emission treatment system for treating an exhaust gas, each including the LT-NA catalyst compositions. Further provided are methods for reducing a NO.sub.x level in an exhaust gas stream using the catalyst article. In particular, the LT-NA compositions include a zeolite containing a first metal component including palladium and a second metal component which is an alkaline earth metal component, an oxide of an alkaline earth metal component, a rare earth metal component, an oxide of a rare earth metal component, or a combination thereof. The LT-NA compositions exhibit increased low temperature NO.sub.x adsorption capacity and enhanced hydrothermal stability.

Provided is, for example, an exhaust gas-purifying three-way catalyst which is small in the amount of a platinum group element used, which can be early increased in temperature to a catalytically active temperature, which is suppressed in degradation in performance due to a catalyst poison included in an exhaust gas even if placed directly under an engine, and which is excellent in purification performance. An exhaust gas-purifying three-way catalyst including at least a catalyst carrier 11 and a catalyst layer 21, wherein the catalyst layer 21 has a layered structure having at least a first catalyst layer L1, a second catalyst layer L2 and a third catalyst layer L3 in the listed order, the first catalyst layer L1 contains a first composite catalyst particle including palladium supported on a first base material particle, the second catalyst layer L2 contains a second composite catalyst particle including rhodium supported on a second base material particle, the third catalyst layer L3 contains a third composite catalyst particle including palladium supported on a third base material particle, and the total coating weight Wt in the catalyst layers L1, L2, and L3 (provided that the platinum group element included in each of the catalyst layers is excluded) is 110 g/L or more and 225 g/L or less in total, per volume of the catalyst carrier 11.

There is provided a structure including: a substrate including a first and a second ends, and a porous partition wall defining a first and a second cells extending between the first and the second ends; a first catalyst; and a second catalyst. In a first area, the first catalyst is disposed on a first surface of the partition wall, and the partition wall with the first catalyst disposed on the partition wall is impermeable to gas. In a second area, the first catalyst is not provided, the second catalyst is disposed in a region including at least a part inside the partition wall, the part facing the first cell, and the partition wall with the second catalyst disposed in the partition wall is permeable to gas. In a third area, any of the first catalyst or the second catalyst is not provided, and the partition wall is permeable to gas.

The exhaust gas cleaning catalyst according is provided with a substrate and a catalyst coat layer formed on a surface of the substrate. The catalyst coat layer is formed as a laminate structure having an upper layer and a lower layer. The upper layer is a Pd-free layer that does not contain Pd, and the lower layer is a Pd-containing layer. In addition, when a region of the lower layer that corresponds to 20% of the length of the exhaust gas cleaning catalyst from the exhaust gas inlet side end towards the exhaust gas outlet side of the exhaust gas cleaning catalyst is divided into four equal regions to be each 5% of the length, the relationship A>B>C is satisfied, where A, B, and C represents the Pd content in the first, second, and third region respectively.

The invention relates to a catalyst device for purifying exhaust gases containing nitrogen oxide by using selective catalytic reduction (SCR), the catalyst device comprising at least two catalytic layers, the first layer containing vanadium oxide and a mixed oxide comprising titanium oxide and silicon oxide and the second layer containing a molecular sieve containing iron, wherein the first layer is applied onto the second layer. The invention also relates to uses of the catalyst device and a method for purifying exhaust gases.