An apparatus for purifying an exhaust gas includes an engine, an exhaust pipe, a first lean NOx trap (LNT) adapted to absorb nitrogen oxide (NOx) contained in the exhaust gas, to release the absorbed NOx, and to reduce the NOx contained in the exhaust gas or the released NOx or to generate ammonia (NH.sub.3), a second LNT adapted to absorb the NOx, to release the absorbed NOx, and to reduce the NOx contained in the exhaust gas or the released NOx or to generate the NH.sub.3, and a selective catalytic reduction (SCR) catalyst adapted to temporarily absorb the NH.sub.3 and to reduce the NOx contained in the exhaust gas, wherein the second LNT is positioned such that an average temperature of the second LNT is lower than that of the first LNT by 50-150 C. based on an average temperature of the exhaust gas.

Provided is: an oxidation catalyst having excellent ability to combust diesel fuel intermittently sprayed from a nozzle disposed in an exhaust pipe, the oxidation catalyst being incorporated into an exhaust gas purification device having a diesel particulate filter (DPF) or a catalyst soot filter (CSF) for collecting particulate matter from a diesel engine; and an exhaust gas purification device that uses the oxidation catalyst. An oxidation catalyst for exhaust gas purification in which a precious metal component is carried on an inorganic matrix, wherein the inorganic matrix is one or more inorganic oxides selected from the group consisting of alumina, titania, zirconia, silica, and silica-alumina, the oxidation catalyst being characterized in the use of a material in which the activation energy of diesel fuel combustion performance is 72 kJ/mol or less.

An exhaust treatment system includes an engine, an exhaust line in fluid communication with the engine, a three-way catalyst downstream of the engine on the exhaust line, a particulate filter downstream of and proximate to the three-way catalyst on the exhaust line, and a sorbent unit comprising a first sorbent and a second sorbent downstream of the three-way catalyst and the particulate filter on the exhaust line. The first sorbent and the second sorbent are proximate to a tailpipe of the exhaust line. A method of treating an exhaust emission from an internal combustion engine during an engine cold-start is also described.

The present disclosure is directed to an emission treatment system for NO.sub.x abatement in an exhaust stream of a lean burn engine. The emission treatment system includes a lean NO.sub.x trap (LNT) in fluid communication with and downstream from the lean burn engine and a low-temperature NO.sub.x adsorber (LT-NA) in fluid communication with and downstream of the LNT. Further provided is a method for abating NO.sub.x in an exhaust stream from a lean burn engine utilizing the disclosed system.

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 and a second layer.

A controlling method of exhaust gas purification system to which a lean combustion engine is applied and an LNT device, a DPF or an SDPF, and an SCR device are provided includes detecting vehicle information and determining whether the vehicle information satisfies nitrogen oxide desorption condition of the LNT device; desorbing the nitrogen oxide until the nitrogen oxide of the LNT reaches predetermined reference amount through engine rich combustion when vehicle information satisfies the nitrogen oxide desorption condition of the LNT device; injecting urea to purify the nitrogen oxide after a first period after ending of desorption of the nitrogen oxide of the LNT; desorbing sulfide of the LNT through the engine rich combustion; and injecting urea to purify the nitrogen oxide after a second period after ending of desorption of the sulfide rich combustion of the LNT.

Zoned diesel oxidation catalysts containing a higher precious metal loading in the inlet zone that the outlet zone and an equal or shorter length inlet zone are described. Emission treatment systems and methods of remediating nitrogen oxides (NOx), particulate matter, and gaseous hydrocarbons using zoned diesel oxidation catalysts are also described.

Selective catalytic reduction filter (SCRF) devices and systems incorporating the same are provided. Systems can include an exhaust gas source, an exhaust gas conduit capable of receiving an exhaust gas stream from the exhaust gas source, and an SCRF device in fluid communication therewith. The SCRF device can include a filter, a selective catalytic reduction (SCR) catalyst disposed on at least portion of the filter, and a NO.sub.x storage coating on at least a portion of the filter. The NO.sub.x storage coating can include one or more of palladium, barium, or cerium. The NO.sub.x storage coating can be biased towards the upstream side of the filter. The NO.sub.x storage coating can overlap a portion of the SCR catalyst. The system can further include a water-absorbing alkali oxide. The water-absorbing alkali oxide can be disposed within the SCRF device, the exhaust gas conduit, or in an upstream oxidation catalyst device.

A system comprising a hydrocarbon source, a downstream catalyst, and an SCR catalyst, wherein the SCR catalyst is located between the hydrocarbon source and the downstream catalyst, and wherein the downstream catalyst comprises a catalyst selected from the group consisting of a diesel oxidation catalyst (DOC), a diesel exotherm catalyst (DEC), a catalyzed soot filter (CSF), a NOx absorber, a selective catalytic reduction/passive NOx adsorber (SCR/PNA), a cold-start catalyst (CSC) or a three-way catalyst (TWC).

Methods and systems are provided for a HC trap in a bypass passage. In one example, a method may include closing a diverter valve to flow exhaust gas from a main exhaust passage to the bypass passage during a cold-start.