A catalyst for removing nitrogen includes an LNT catalyst and a Cu/CeO.sub.2 catalyst physically mixed with the LNT catalyst.

An exhaust after-treatment system includes a first set of exhaust after-treatment components, a second set of exhaust after-treatment components, an inlet to the exhaust after-treatment system, an outlet from the exhaust after-treatment system, and a valve and conduit arrangement configurable in a plurality of modes, in a first mode, exhaust gas entering the inlet flows through the second set of exhaust after-treatment components, then through the first set of exhaust after-treatment components, and then through the outlet. In a second mode, exhaust gas entering the inlet flows through the second set of exhaust after-treatment components without flowing through the first set of exhaust after-treatment components, and then through the outlet in a third mode, exhaust gas entering the inlet flows through the first set of exhaust after-treatment components, then through the second set of exhaust after-treatment components, and then through the outlet.

A nitrous oxide (N.sub.2O) removal catalyst composition for treating an exhaust stream of an internal combustion engine is provided, containing a platinum group metal (PGM) component on a metal oxide-based support, wherein the N.sub.2O removal catalyst composition is in a substantially reduced form, such that it has an oxygen deficiency of about 0.05 mmol oxygen atoms/g or greater, and wherein the N.sub.2O removal catalyst composition provides effective removal of at least a portion of N.sub.2O from the exhaust stream under lean conditions at a temperature of about 350 C. or lower. N.sub.2O removal catalytic articles, systems, and methods are also provided for removing at least a portion of N.sub.2O from an exhaust stream under lean, low temperature conditions.

Provided are a novel form of AFX zeolite, a novel synthesis technique for producing pure phase small pore zeolites, a novel synthesis method for producing a zeolite with an increased Al pair content, a catalyst comprising the AFX zeolite in combination with a metal, and methods of using the same.

Exhaust gas catalysts are disclosed. One exhaust gas catalyst comprises a noble metal and a molecular sieve, and has an infrared spectrum having a characteristic absorption peak from 750 cm.sup.1 to 1050 cm.sup.1 in addition to the absorption peaks for the molecular sieve itself. The exhaust gas catalyst also comprises a noble metal and a molecular sieve, having greater than 5 percent of the noble metal amount located inside pores of the molecular sieve. The exhaust gas catalyst also comprises a first and second molecular sieve catalyst. The first molecular sieve catalyst comprises a first noble metal and a first molecular sieve, and the second molecular sieve catalyst comprises a second noble metal and a second molecular sieve. The first and second molecular sieves are different. The invention also includes exhaust systems comprising the exhaust gas catalysts, and a method for treating exhaust gas utilizing the exhaust gas catalysts.

An exhaust purification apparatus for an internal combustion engine is provided with an NO.sub.x storage and reduction type catalyst in an exhaust passage. The NO.sub.x storage and reduction type catalyst comprises a base member, an upstream side coat layer arranged on the base member, and a downstream side coat layer arranged at a downstream side in the direction of exhaust flow from the upstream side coat layer. The upstream side coat layer does not include a Ce-containing oxide but includes a precious metal catalyst. The downstream side coat layer contains a Ce-containing oxide and precious metal catalyst. A length of the upstream side coat layer is a length of 5 to 62.5% of the total length of the upstream side coat layer and the downstream side coat layer, while the remaining part of the coat layer aside from the upstream side coat layer is the downstream side coat layer.

A passive NO.sub.X adsorbent includes: palladium, platinum or a mixture thereof and a mixed or composite oxide including the following elements in percentage by weight, expressed in terms of oxide: 10-90% by weight zirconium and 0.1-50% by weight of least one of the following: a transition metal or a lanthanide series element other than Ce. Although the passive NO.sub.X adsorbent can include Ce in an amount ranging from 0.1 to 20% by weight expressed in terms of oxide, advantages are obtained particularly in the case of low-Ce or a substantially Ce-free passive NOx adsorbent.

A lean NO.sub.x trap catalyst and its use in an emission treatment system for internal combustion engines is disclosed. The lean NO.sub.x trap catalyst comprises a first layer, a second layer, and a third layer.

A lean NO.sub.x trap catalyst and its use in an emission treatment system for internal combustion engines is disclosed. The lean NO.sub.x trap catalyst comprises a first layer, a second layer, and a third layer.

NO.sub.x abatement compositions have a formula M.sub.xCu.sub.1-xFe.sub.2O.sub.4, wherein M is a substitution metal cation that can be any of cobalt, nickel, and zinc; and x is greater than zero and less than one. Such compositions can serve as direct decomposition catalysts and/or passive adsorption/storage components. Methods for synthesizing the compositions include alkaline precipitation of solutions containing nitrate salts of copper, iron, and at least one of cobalt, nickel, and zinc.