An ammonia slip catalyst (ASC) comprising a first SCR catalyst, an oxidation catalyst comprising ruthenium or a Ru mixture, such as a Pt and Ru mixture, on a support comprising a rutile phase and a substrate is described. In some configurations, the ASC comprises a second oxidation catalyst. In other configurations, the ASC comprises a second oxidation catalyst and a third oxidation catalyst. The ASC's are useful for selective catalytic reduction (SCR) of NOx in exhaust gases and in reducing the amount of ammonia slip. Methods for producing such articles are described. Methods of using the ammonia slip catalyst in an SCR process, where the amount of ammonia slip is reduced, are also described.

In an engine exhaust passage, in order from an exhaust upstream side, an NO.sub.x storage and reduction catalyst, NO oxidation catalyst, NO.sub.2 reduction catalyst, and selective reduction catalyst may be arranged. An air-fuel ratio of an exhaust gas which flows into the NO.sub.x storage and reduction catalyst may be temporarily switched to a rich air-fuel ratio which may be adapted for generating ammonia from NO.sub.x which may be stored in the NO.sub.x storage and reduction catalyst. The ammonia, which may be generated by the NO.sub.x storage and reduction catalyst, may be held at the selective reduction catalyst. The NO.sub.x which flows into the selective reduction catalyst may be reduced by the ammonia. The NO oxidation catalyst and NO.sub.2 reduction catalyst may be used to make an NO ratio of the exhaust gas which flows into the selective reduction catalyst approach an optimum ratio of the selective reduction catalyst.

An exhaust system for a diesel engine is disclosed. The exhaust system may include a diesel oxidation catalyst (DOC) configured to receive exhaust gases from the engine and oxidize hydrocarbons in the exhaust gases and a passive NOx adsorber (PNA) downstream from the DOC and configured to store NOx from the exhaust gases at temperatures up to 150 C. A selective catalytic reduction (SCR) system may be downstream from the PNA and configured to reduce NOx in the exhaust gases. The PNA may be configured to release the stored NOx at temperatures above 200 C. The DOC upstream of the PNA may reduce the amount of N.sub.2O that is generated by the PNA by oxidizing hydrocarbons before they reach the PNA.

The present invention provides a deterioration diagnosis apparatus for an exhaust gas purification apparatus, including a first sensor that measures the oxygen concentration of the exhaust gas flowing into the exhaust gas purification apparatus, a second sensor that measures the oxygen concentration of the exhaust gas flowing out of the exhaust gas purification apparatus, and diagnosing means for diagnosing deterioration of the exhaust gas purification apparatus on the basis of a difference that appears between a measurement value of the first sensor and a measurement value of the second sensor when the air-fuel ratio of the exhaust gas flowing into the exhaust pas purification apparatus is switched from a lean air-fuel ratio to a rich air-fuel ratio, wherein, when the air-fuel ratio of the exhaust gas is switched from a lean air-fuel ratio to a rich air-fuel ratio, a water-gas shift reaction is generated upstream of the first sensor.

Systems and methods directed at removing HCN from an FCC process flue gas (and/or generated in the catalyst system reactions themselves) such that the final HCN output is satisfactory; while, in so doing, avoiding undesirable levels of other pollutants contained in that exhaust gas such as NOx. A system includes an assembly having a fluid catalytic cracking (FCC) unit generating a flue gas with HCN and NOx and a catalyst device placed in the flue gas line to remove HCN and NOx. The catalyst device having one or more SCR catalytic articles, as in one free of platinum group metal material (PGM) or a dual functioning SCR catalyst with PGM, or a combination of each. The assembly can be provided with an ammonia supplier and optionally an H2O supplier with associated injection for supply into the flue gas upstream of a catalytic article(s).

A dosing module for an aftertreatment system includes: a housing; a dosing cartridge removably inserted in the housing, the dosing cartridge including a needle assembly; a cover coupled to the housing, the cover covering the dosing cartridge; an inlet port inserted in the housing, the inlet port configured to receive reductant and provide the reductant to the dosing cartridge; and a filter screw coupled to the inlet port such that the filter screw is interchangeable, the filter screw including a pin, the filter screw being compressible to provide compensation for fluid expansion.

An exhaust gas aftertreatment system in the exhaust gas system of an ammonia combustion engine, wherein the exhaust gas system can be traversed by an exhaust gas flow of the ammonia combustion engine, including a passive SCR catalyst, an oxidation catalyst with which ammonia contained in the exhaust gas flow can be oxidized, and a regulated SCR catalyst. The oxidation catalyst is arranged in the exhaust gas system downstream of the passive SCR catalyst and the regulated SCR catalyst is arranged in the exhaust gas system downstream of the oxidation catalyst. The exhaust gas aftertreatment system further comprises at least one N2O decomposition catalyst arranged in the exhaust gas system upstream of the passive SCR catalyst or downstream of the passive SCR catalyst, the oxidation catalyst, and/or the regulated SCR catalyst.