An after treatment method for a lean-burn engine is disclosed. The after treatment method is configured to control an after treatment system sequentially equipped with an ammonia production catalyst module, a selective catalytic reduction (SCR) catalyst, and a CO clean-up catalyst (CUC) on an exhaust pipe through which an exhaust gas flows and which is connected to a lean-burn engine. NH.sub.3 generation in the ammonia production catalyst module is changed according to a temperature and a temperature change rate of the SCR catalyst.

An after treatment method for a lean-burn engine is disclosed. The after treatment method is configured to control an after treatment system sequentially equipped with an ammonia production catalyst module, a selective catalytic reduction (SCR) catalyst, and a CO clean-up catalyst (CUC) on an exhaust pipe through which an exhaust gas flows and which is connected to a lean-burn engine. In the after treatment method, a rich air/fuel ratio (AFR) is controlled in multiple phases in response to detecting that conversion to the rich AFR is desired.

A method for operating an exhaust gas system is provided. The method includes determining an amount of a reducing agent to be supplied to the exhaust gas of an engine and evaluating measurements which indicate a content of nitrogen oxides in the exhaust gas downstream of a catalytic device adapted to diminish the content of nitrogen oxides. A magnitude and a frequency of the measurements are taken into account in determining the amount of the reducing agent to be supplied. A plurality of measurements is captured during a predetermined period of time. A magnitude of a measurement captured within this period of time is related to a quantity derived from the respective magnitudes of the plurality of measurements. The related measurement is utilized to determine the amount of the reducing agent to be supplied. A control assembly for operating an exhaust gas system is also provided.

An after treatment method for a lean-burn engine is disclosed. The after treatment method is configured to control an after treatment system sequentially equipped with an ammonia production catalyst module, a selective catalytic reduction catalyst, and a CO clean-up catalyst on an exhaust pipe through which an exhaust gas flows. In the after treatment method, the engine is operated sequentially at a stoichiometric air/fuel ratio (AFR) and a lean AFR prior to entering a rich AFR.

A method for preconditioning at least a part of an engine system of a vehicle. The engine system includes an engine and an exhaust aftertreatment system, EATS. The method providing predicted vehicle operational information comprising a vehicle operational initialization time and predicted engine operation, determining whether or not cold-start emissions of the predicted engine operation achieves a threshold criterium, in response to achieving the threshold criterium, preconditioning at least a part of the engine system such that at least said part of the engine system is preconditioned at a time of the vehicle operational initialization time.

Unique SCR catalyst including multiple washcoat formulations with differing performance characteristics are disclosed. One exemplary embodiment is an apparatus including a catalyst substrate defining a plurality of flow channels leading from an inlet to an outlet, a first washcoat composition distributed over a first portion of the flow channels, and a second washcoat composition distributed over a second portion of the flow channels. The first washcoat composition has a lower ammonia storage density than the second washcoat composition.

Provided are compositions, articles, systems and methods that comprise or use a catalyst composition comprising a zeolite having an LTA structure with iron, manganese or a combination thereof as an extra-framework metal. The zeolite can have a mole ratio of silica-to-alumina (SAR) of about 15 to about 70 and can contain about 0.5 to about 10 weight percent, based on the total weight of the zeolite, of extra-framework iron, manganese or a combination thereof.

The invention provides a selective catalytic reduction (SCR) catalyst effective in the abatement of nitrogen oxides (NOx), the SCR catalyst comprising a metal-promoted molecular sieve promoted with a metal selected from iron, copper, and combinations thereof, wherein the metal is present in an amount of 2.6% by weight or less on an oxide basis based on the total weight of the metal-promoted molecular sieve. A catalyst article, an exhaust gas treatment system method, and a method treating an exhaust gas stream, each comprising the SCR catalyst of the invention, are also provided. The SCR catalyst is particularly useful for treatment of exhaust from a lean burn gasoline engine.

An exhaust gas purification system for an engine includes an exhaust passage extending from the combustion chambers of the engine, and an exhaust purifying unit disposed in the exhaust passage and configured to purify exhaust gas in the exhaust passage. The exhaust purifying unit includes a carrier disposed in the exhaust passage, a first purifier having at least a function of oxidizing components in the exhaust gas. The first purifier covers, as an underlayer, an outer surface of the carrier, and a second purifier having a function of purifying the exhaust gas by reducing, using occluded ammonia, the components in the exhaust gas that have been oxidized in the first purifier. The second purifier includes a superposed portion covering, as an upper layer, an outer surface of the first purifier.

Described are SCR catalyst systems comprising a first SCR catalyst composition and a second SCR catalyst composition arranged in the system, the first SCR catalyst composition promoting higher N.sub.2 formation and lower N.sub.2O formation than the second SCR catalyst composition, and the second SCR catalyst composition having a different composition than the first SCR catalyst composition, the second SCR catalyst composition promoting lower N.sub.2 formation and higher N.sub.2O formation than the first SCR catalyst composition. The SCR catalyst systems are useful in methods and systems to catalyze the reduction of nitrogen oxides in the presence of a reductant.