DE102014119503A1 - Apparatus and method for exhaust gas treatment - Google Patents

Abstract

An apparatus and method for exhaust treatment are provided. The apparatus includes a lean NOx trap (LNT), a Selective Catalytic Reduction (SCR) catalyst, and an oxygen storage catalyst containing an oxygen storage material and a noble metal sequentially passed along one Exhaust flow direction are arranged. The apparatus also includes a front lambda probe disposed upstream of the LNT, a rear lambda probe disposed downstream of the oxygen storage catalyst, and a temperature sensor configured to measure a temperature of an exhaust gas.

Description

background

Field of the invention

The present invention relates to an apparatus and a method for treating exhaust gas of a vehicle. In particular, an exhaust treatment apparatus and method that maximizes nitrogen oxide (NO _x ) reduction performance using a lambda probe and a temperature sensor without using an NO _x sensor.

Discussion of the related art

As emissions regulations are exacerbated by vehicles _DeNOx -Katalysatortechnologien such as lean _NOx trap (LNT) and Selective Catalytic Reduction-be (SCR) used in treatment devices for reducing NO _x in the exhaust gas. A DeNO _x catalyst is a type of catalyst configured to remove NO _x contained in the exhaust gas and when a reducing agent such as urea, ammonia (NH ₃ ), carbon monoxide (CO) or hydrocarbons (HC) is transferred to the exhaust gas, nitrogen oxide (NO _x ) in the DeNO _x catalyst is reduced by an oxidation-reduction reaction with a reducing agent.

In recent years, an LNT has been used as an after-treatment apparatus for removing NO _x generated in operating a lean-burn engine in the exhaust gas, and the LNT adsorbs or occludes NO _x contained in the lean-burn exhaust gas and separates the adsorbed or occluded NO _{X in} a rich atmosphere.

The SCR system is adapted to reduce NO _x efficiently by supplying a reducing agent to the SCR catalyst, and uses a method to reduce NO _x by supplying a reducing agent to the exhaust gas, unlike an exhaust gas recirculation (EGR) system Reducing NO _x by decreasing a combustion temperature of a combustion chamber by recirculating exhaust gas. The SCR system is referred to as a selective catalytic reduction system, which means that a reducing agent, such as urea, ammonia, carbon monoxide or hydrocarbons, is reacted with NO _x in the midst of oxygen and NO _x easier to react.

Further, technologies such as a Diesel Oxidation Catalyst (DOC), a Diesel Particulate Filter (DPF) or a Catalytic Particulate Filter (CPF) have been developed for post-treatment reduction of particulate matter (PM) in vehicle exhaust. Further, in recent years, an SCR to diesel particulate filter (SDPF) which both collects particulate matter and reduces NO _{x has been} developed and used. The SDPF reacts NH ₃ and NO _x in the exhaust gas on an SCR catalyst to purify these molecules in / to water and N ₂ , by applying the SCR catalyst to a porous DPF, and collects particulate matter in the exhaust gas Filter function (eg a DPF function).

In a method of determining the aging of the SCR catalyst and the SDPF catalyst, NO _x sensors are mounted upstream and downstream of the SCR or SDPF, and NO _x is measured by the NO _x sensor to determine if the SCR Catalyst or the SDPF catalyst is aged when the purification performance of the SCR or SDPF is substantially smaller. Aging can using such a method be measured directly, however, since the price of a single NO _x sensor is many times higher than that of a temperature sensor, the cost increases for implementing a method which NOx sensors upstream and downstream of the catalyst are arranged, needed.

Summary

Accordingly, the present invention provides an exhaust treatment apparatus and method that can improve or maximize the nitrogen oxide (NO _x ) reduction performance by using a lambda probe and a temperature sensor without using an NO _x sensor. It should be understood that NO _{x may} include any or all of nitrogen monoxide (NO), nitrogen dioxide (NO ₂ ), and nitrous oxide (N ₂ O).

In accordance with one aspect of the present invention, an exhaust gas treatment apparatus may comprise a lean _NOx trap (LNT), a Selective-Catalytic-reduction-(SCR) catalyst and an oxygen-storage-catalyst comprising a oxygen storage material and a noble metal, and which may be sequentially arranged along an exhaust gas flow direction. Further, a front lambda probe may be disposed upstream of the LNT, a rear lambda probe may be disposed downstream of the oxygen storage catalyst, and a temperature sensor that may be configured to measure a temperature of exhaust gas may also be provided.

In accordance with one aspect of the present invention, in a exhaust treatment process, a lean NO _x trap (LNT), a selective catalytic reduction (SCR) Catalyst and an oxygen storage catalyst containing an oxygen storage material and a noble metal may be arranged sequentially along an exhaust gas flow direction, and a front lambda probe may be disposed upstream of the LNT, and a rear lambda probe may be disposed of the oxygen storage catalyst be arranged downstream. The method may include measuring a temperature of exhaust gas through a temperature sensor. In addition, during rich operation of the vehicle internal combustion engine, NO _{x may} be removed by the SCR catalyst when NH ₃ generated by the LNT and NO _x in the exhaust gas react with each other in the SCR catalyst.

Accordingly, the exhaust gas treatment apparatus and the method of controlling the same can maximize according to the present invention, the NO _x reduction performance using an oxygen sensor and a temperature sensor, without using a _NOx sensor, or improve.

Brief description of the drawings

The drawings are provided with references for describing embodiments of the present invention, and the spirit of the present invention should be understood not only with reference to the accompanying drawings. The above and other objects, features and other advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:
The above and other features of the present invention will now be described in detail with reference to certain embodiments thereof, which are illustrated by way of illustration only in the accompanying drawings, which are given below and are therefore not limiting of the present invention, wherein:

1 FIG. 10 is an exemplary view showing a configuration of an exhaust treatment device according to an embodiment of the present invention; FIG.

2 FIG. 11 is an exemplary sectional view showing a configuration of an integral SDPF / ceria catalyst in the configuration of the embodiment incorporated in FIG 1 shown shows;

3 FIG. 4 is an exemplary view schematically showing a configuration of an exhaust treatment apparatus according to an embodiment of the present invention; FIG.

4 is an exemplary view showing a zone-applying type SCR catalyst and a ceria catalyst in the embodiment, which in 3 shown shows;

5 Fig. 10 is an explanatory view for explaining an NH ₃ generating mechanism in an LNT in the present invention; and

6 FIG. ₃ is an exemplary view describing an NH ₃ generation temperature range in the present invention. FIG.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, particular dimensions, orientations, locations and shapes, will be determined in part by the particular application and the particular environment of use. In the various figures of the drawing, the reference numerals designate the same or equivalent parts of the present invention throughout.

Detailed description

It should be understood that the term "vehicle," or "vehicle," or other similar terms as used herein, generally includes motor vehicles, such as passenger cars including sport utility vehicles (SUVs), buses, trucks , various commercial vehicles, watercraft including a variety of boats and ships, aircraft and the like, and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen powered vehicles, and other alternative fuel vehicles (eg, fuel derived from non-petroleum fuels is won). Herein, a hybrid vehicle means a vehicle having two or more drive sources, for example, vehicles that are both gasoline-powered and electric-powered.

Although the embodiments are described as using a plurality of units to perform the example process, it will be understood that the example processes may be performed by one or a plurality of modules. In addition, it should be understood that the term controller / controller refers to a hardware device having a memory and a processor. The memory is configured to store the modules and the processor is specifically configured to be said Execute modules to perform one or more processes, which are further described below.

Additionally, the control logic of the present invention may be embodied as a non-transitory, computer-readable medium on a computer-readable medium / medium that includes executable program instructions executed by a processor, controller, or the like. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disk (CD) ROMs, magnetic tape, floppy disks, flash memory, smart cards, and optical data storage devices. The computer readable recording medium may also be distributed in network coupled computer systems such that the computer readable media are distributed in a distributed fashion, e.g. by a telematics server or a controller area network (CAN), stored and executed.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms "a", "an", "the", "the" and "the" also intend to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "having" when used in this specification specify the presence of specified features, numbers, steps, activities, elements and / or components, but not the presence or addition of exclude one or more other features, numbers, steps, activities, elements, components and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

Unless specifically stated or obvious from context, the term "about" as used herein is understood to be within a range of normal tolerance in the art, for example, within 2 standard deviations of the mean. "About" may be considered within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05% or 0.01% of said value. Unless the context indicates otherwise, all numerical values provided herein are modified by the term "about."

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains can easily practice the present invention. The present invention relates to an exhaust treatment device and an exhaust treatment method by which a stricter EU6 emission standard can be overcome, and basically comprises an LNT, an SCR catalyst, and an oxygen storage catalyst.

1 FIG. 10 is an exemplary view showing a configuration of an exhaust treatment apparatus according to an embodiment of the present invention. FIG. A lean NO _x trap (LNT), a selective catalytic reduction (SCR) catalyst, and an oxygen storage catalyst may be sequentially arranged with respect to an exhaust gas flow direction to thereby produce exhaust gas consisting of a gas Internal combustion engine exits to allow to flow sequentially through the LNT, the SCR and the oxygen storage catalyst. The LNT can be a catalyst, which is provided with a high-temperature occlusion material such as Ba, is coated, and can be configured to NO _x contained in the exhaust gas under the lean atmosphere (for example, during lean operation) to adsorb or occlude and NH ₃ as a by-product, when NO _{x is converted in} a rich atmosphere (eg during rich operation). In the present invention, the SCR catalyst may be an SCR on diesel particulate filter (SDPF) configured to collect particulate matter (PM) and reduce NO _x .

The SDPF may be configured by applying an SCR catalyst material to a diesel particulate filter (DPF) configured to collect particulate matter in the diesel exhaust. NH ₃ and NO _x in the exhaust gas may react with each other on the SCR catalyst to be converted to water and N ₂ , and particulate matter in the exhaust gas may be collected by a filtering function (eg, a DPF function). The combination of the LNT and the SDPF may be included in a passive SCR catalyst system to produce by-product NH ₃ when NO _x trapped by the LNT is converted to rich atmosphere and NH _{3 derived} from the LNT is generated and NO _x in the exhaust gas react with each other in the SDPF to become purified (eg, converted into nitrogen and water). The oxygen storage catalyst may include a ceria catalyst in which ceria (CeO ₂ ) (ie, an oxide of cerium called ceria) serves as an oxygen storage material. In one embodiment of the present invention, the SDPF and the ceria catalyst may be integrally configured using (precisely) a porous filter.

2 FIG. 10 is an exemplary sectional view showing a configuration of an integral SDPF / ceria catalyst in the configuration of the embodiment incorporated in FIG 1 shown shows. The integral SDPF / ceria catalyst can have a porous filter configured to collect particulate matter in the diesel exhaust, a Selective Catalytic Reduction (SCR) catalyst layer 12 , which is attached to an exhaust inlet of the filter, and a cerium dioxide catalyst layer 13 which is attached to an exhaust gas outlet of the filter and contains ceria and a noble metal. The SCR catalyst layer 12 may comprise an applied layer containing a zeolite catalyst, and the ceria catalyst layer 13 may be formed by incorporating a noble metal (eg, the noble metal may include, but is not limited to, platinum, palladium, and rhodium) into ceria.

The filter may include a plurality of laminated filter walls 11 and facing surfaces of the plurality of filter walls 11 can form alternating exhaust gas inlets and exhaust outlets. In particular, the SCR catalyst layer (zeolite type) 12 are applied to a surface of the porous filter, and the ceria catalyst layer 13 containing ceria (oxygen storage material) and a noble metal may be applied on an opposite surface of the porous filter. The catalyst can be prepared by applying the SCR catalyst layer 12 on a surface of the inlet of the DPF filter and applying the ceria catalyst layer 13 in which a noble metal is supported by ceria, are formed on a surface of an outlet of the DPF filter. The ceria may first be applied to a surface of the outlet of the DPF filter, and a cerium dioxide catalyst layer in which a noble metal may be supported may be additionally applied before the ceria catalyst layer 13 , in which the noble metal is carried by ceria, is applied.

The integral SDPF / ceria catalyst may be provided by providing the porous filter for collecting particulate matter of the diesel exhaust gas as the main body and applying the SCR catalyst layer 12 at an exhaust inlet of the filter and applying the cerdioxod catalyst layer 13 be configured at an exhaust outlet of the filter. The filter may include a plurality of laminated filter walls 11 , which may be separated from each other by a predetermined distance. Mutually facing surfaces of the plurality of filter walls 11 can form alternating exhaust gas inlets and exhaust outlets.

Furthermore, plugs can 14 , which are configured to block rear ends of the inlets and front ends of the outlets, between the filter walls 11 be arranged to allow only the front ends of the inlets are opened while the rear ends of the inlets through the plugs 14 can be locked, and only the rear ends of the outlets can be opened while the front ends of the outlets through the plugs 14 are locked. Lambda probes L1 and L2 configured to detect an oxygen concentration in the exhaust gas may be provided on an upstream side of the LNT and a downstream side of the oxygen storage catalyst in the embodiment of FIG 1 be arranged. The upstream side lambda probe (hereinafter referred to as "front lambda probe") L1 may be disposed on the upstream side of the LNT, and the downstream side lambda probe (hereinafter referred to as "rear lambda probe") L2 may be downstream of the ceria catalyst (which is an oxygen storage catalyst) may be arranged. That is, on the downstream side of the SDPF / ceria catalyst in which the SDPF and the ceria catalyst are integrally formed by using (exactly) a porous filter.

Temperature sensors T1 and T2 may be located upstream of the SDPF (downstream of the LNT) and downstream of the ceria catalyst, and the temperature sensors T1 and T2 may be located upstream and downstream of the integral SDPF / ceria catalyst in one embodiment of the present invention.

3 FIG. 10 is an exemplary view showing a configuration of an exhaust treatment device according to another embodiment of the present invention. FIG. The LNT, the DPF (for reducing H ₂ S), the SCR catalyst and the oxygen storage catalyst may be sequentially arranged with respect to the exhaust gas flow direction to allow the exhaust gas exiting an internal combustion engine to go through them in turn. In the embodiment 3 For example, a separate DPF configured to reduce H ₂ S may be disposed between the LNT and the SCR catalyst, that is, downstream of the LNT and upstream of the SCR catalyst, and the SCR catalyst and the oxygen storage catalyst be arranged sequentially downstream of the DPF. The oxygen storage catalyst may include a ceria catalyst.

The SCR catalyst and the ceria catalyst may be formed by applying an SCR catalyst material and a ceria catalyst containing a noble metal and ceria on a surface of the carrier through which exhaust gas flows. The SCR catalyst and the ceria catalyst may therefore be an integral catalyst that uses (exactly) a support, and the support may be divided into two regions, such that an SCR catalyst material can be applied to one region and a ceria catalyst material containing a noble metal and ceria (eg an oxygen storage material) can be applied to the other region to form a zone-application type catalyst (ie an integral SCR catalyst / ceria catalyst). In other words, the SCR catalyst material and the ceria catalyst material may be applied to a front surface and a back surface of the carrier in the zone application method as in FIG 4 shown to be applied. The front side may be used as an SCR catalyst (eg zeolite type), and the backside may be used as a ceria catalyst having a catalyst layer in which a noble metal of ceria is supported. Furthermore, by applying an SCR catalyst material and a ceria catalyst material to a support, a catalyst configuration having two building blocks can be created. In other words, a configuration of two building blocks can be applied to the support in which an SCR catalyst and a ceria catalyst are combined separately.

Lambda probes L1 and L2 may be upstream of the LNT and downstream of the oxygen storage catalyst in the embodiment of FIG 3 be mounted. In such an embodiment, the upstream lambda probe (hereinafter referred to as "front lambda probe") L1 may be located upstream of the LNT, and the downstream lambda probe (hereinafter referred to as "rear lambda probe") L2 may be downstream of the ceria catalyst (which is an oxygen Storage catalyst on the downstream side of the LNT). Temperature sensors T1, T2 and T3 may be located upstream (downstream of the LNT) and downstream of the DPF and downstream of the ceria catalyst.

Although the arrangements of exhaust treatment devices according to the embodiments of the present invention with reference to 1 to 3 Such exhaust gas treatment apparatus may effectively reduce or eliminate NO _x from the SCR catalyst by using NH ₃ generated by the LNT when rich atmospheres are periodically controlled by an engine air-fuel ratio control (eg, lambda Control) to reduce NO _x stored in the LNT. In other words, NO _x can be stored in the LNT under a lean atmosphere (lean operation), and NH ₃ can be generated by a reaction in the LNT when rich atmospheres are periodically formed. In particular, NH ₃ and NO _x in the SCR catalyst can react with each other to eliminate NO _x , and the ceria catalyst, which carries a minimum amount of a noble metal, can purify CO and HC which are excessively generated in a rich atmosphere. In order to effectively generate a sufficient amount of NH _3, was then after the oxygen in the LNT was fully ejected through the rich atmosphere, a rich atmosphere for a few seconds be maintained.

An additional rich atmosphere may be maintained by using a rear lambda sensor signal, placing the SCR catalyst downstream of the LNT, adding the oxygen storage catalyst (ceria catalyst) downstream of the SCR catalyst, and mounting the rear lambda probe L2 downstream of the engine oxygen storage catalyst. A period of time in which a rich atmosphere may exist may be prolonged in response to determining that oxygen upstream of the rear lambdasound L2 is not discharged by using a signal of the rear lambda probe L2, since oxygen in the oxygen storage catalyst is not discharged even if the oxygen in the LNT is expelled under the rich atmosphere. Accordingly, an additional rich atmosphere can be maintained, and hence an amount of NH ₃ generated by the LNT can be increased, thereby improving the overall NO _x purification performance. Of course, NH _{3 produced} by the LNT may react with NO _x in the SCR catalyst, and NH ₃ may be used to purify NO _x in the SCR catalyst. According to the present invention, a period in which a rich atmosphere can be artificially increased by disposing a ceria catalyst having an oxygen storage material and a substantially small amount of a noble metal downstream of the SCR catalyst. If the lambda probe L2 is located downstream of the ceria catalyst so that an additional rich atmosphere can be maintained (eg, the period of time during which the rich atmosphere may be increased), a sufficient amount of NH ₃ can be effectively generated, and purification of NH ₃ and NO _x can be performed in the SCR catalyst, and CO and HC can be eliminated by the ceria catalyst which carries a noble metal.

5 Fig. 10 is an explanatory view for explaining an NH ₃ generation mechanism in an LNT in the present invention. In 5 the horizontal axis denotes time, and the vertical axis indicates (a) the lambda value, (b) the temperature and (c) the concentration of NH ₃ and CO in the exhaust gas. Referring to 5A , a lambda breakthrough generation timing is referred to as a breakpoint. The breakthrough point may be a time when the lambda values of the Lambda probe (front lambda probe) upstream of the LNT and the lambda probe downstream of the LNT coincide in a rich atmosphere.

It should be noted that the lambda probe downstream of the LNT may differ from the rear lambda probe L2 proposed in the present invention. In other words, the lambda probe L2, which is located downstream of the ceria catalyst (which is an oxygen storage catalyst), may include a downstream lambda probe on a back side of the LNT (upstream of the SCR catalyst (SDPF) 1 and upstream of the DPF 3 is arranged). Hereinafter, the lambda probe downstream of the LNT may be different from the rear lambda probe, and the lambda probe downstream of the LNT may be a lambda probe located downstream of the LNT rear end, the rear lambda probe being a lambda probe located downstream of the ceria catalyst (the an oxygen storage catalyst) is arranged. According to the related art, rich operation control is performed at a lambda breakthrough generation timing (defined as a time at which the lambda values of the upstream and downstream lambda sensors coincide) as in FIG 5 illustrated, finished.

Further shows 5B an exemplary temperature of exhaust gas (eg, a temperature value sensed by the temperature sensor T1 downstream of the LNT). 5C illustrates a breakthrough point (t _bt ). A breakthrough point may be defined as a time during rich operation where the lambda values of the lambda probe L1 coincide upstream of the LNT and the lambda probe downstream of the LNT. When a rich atmosphere (eg, lambda value (□) <1) is generated by an engine operation, a chemical reduction reaction formula (eg, a NO _x chemical reaction performed by storing NO _x in a rich atmosphere) before generating a break-through point may be as follows : Ba (NO ₃ ) ₂ + 3CO → 2NO + 2CO ₂ + BaCO ₃ 2NO + 2CO → N ₂ + 2CO ₂

When a concentration of oxygen in the exhaust gas is reduced in a rich atmosphere and the content of a reducing agent such as CO or HC is increased, a nitrate sealed in a substantially high temperature sealing material such as Ba may be occluded, to be converted to nitrogen N ₂ while being reduced by reducing agents such as CO or HC. The reaction formula after generating the break-through point may be as follows: CO + H ₂ O → CO ₂ + H ₂ (water gas shift) HC ₃ + 3H ₂ O → 3CO + 6H ₂ (steam reforming) 5H ₂ + 2NO → 2NH ₃ + 2H ₂ O

Generation of NH ₃ in the LNT occurs at a time when oxygen stored in the oxygen storage material of the LNT and NO _x stored in the NO _x -release material are discharged and eliminated, and H ₂ and NO (separated from the LNT or supplied from the exhaust gas) react with each other to generate NH ₃ after NO _x and O ₂ are discharged under the rich atmosphere conditions. As in 5C illustrates that most of NH ₃ can be generated during a period □, after t _bt (breakthrough point). In addition, an amount of NH _{3 may be} increased if the rich atmosphere is maintained for a period □ after t _bt .

Although, according to the related art, the rich control may be completed at a break-through point when the lambda values of the upstream and downstream lambda sensors coincide with each other, according to the present invention, a rich control may be completed when the lambda values of the front lambda probe (the lambda probe at the upstream Side of the LNT) L1 and the rear lambda probe L2 coincide with each other, whereby an additional fat control for the period ☐, after the t _{bt of} the related art, can be maintained. Since the generation of NH _{3 may} decrease if □ is set too short, and the generation of NH ₃ may be increased, while the generation of CO may be increased excessively, which may adversely affect a fuel ratio if □ set too long is the appropriate setting or optimization of ☐ according to a combustion engine state is desirable.

The additional grease control time □ (eg, within about 5 seconds) may be increased according to the downstream oxygen storage catalyst, ie, an amount of ceria of the ceria catalyst or an amount of stored oxygen, however, by such continuation of the rich operation state excessive amount of NH _{3 are} formed.

Increased NH _{3 produced} during the additional rich operating time may react with NO _x through an SCR catalyst downstream of the LNT to reduce NO _x , and increased CO and HC generated during the additional rich operating time may additionally be used of a noble metal contained in the ceria catalyst can be reduced. Major factors, engine / catalyst conditions that may affect the generation of NH ₃ may include a temperature of exhaust gas, a flow rate of exhaust gas, an extent of catalyst aging (eg, decomposition), and t _bt , and the □ time may be reduced become when t _bt decreases. Although according to the related art, the rich atmosphere for DeNO _x can be eliminated immediately after t _bt , according to various embodiments of the present invention, a substantial amount of NH ₃ can be effectively generated by exposing the rich atmosphere for an additional period □ (as in FIG 5 illustrated) after t _bt for DeNO _{x is} maintained, whereby in the SCR catalyst, an amount of NO _x in the exhaust gas can be additionally reduced.

6 Fig. 10 is an exemplary view describing an NH ₃ generation temperature range; Generation of NH ₃ starts at a substantially low temperature of about 200 ° C, and a maximum amount of NH ₃ can be generated at about 300 ° C. NH ₃ can also be generated at about 350 ° C or higher. The amount of generated NH ₃ depends on: Lambda values, a flow rate of exhaust gas and concentration.

Although embodiments of the present invention have been described in detail, the scope of the present invention is not limited thereto, but various modifications and improvements made by those skilled in the art using the basic concepts of the present invention as defined in the claims are also to be considered within the scope of the present invention.

Claims (19)

A device for exhaust gas treatment, comprising: a lean _NOx trap (LNT); a temperature sensor configured to measure a temperature of an exhaust gas; a Selective Catalytic Reduction (SCR) catalyst; and an oxygen storage catalyst including an oxygen storage material and a noble metal, wherein the LNT, the SCR, and the oxygen storage catalyst are sequentially arranged along an exhaust gas flow direction, and wherein a front lambda probe is disposed upstream of the LNT , a rear lambda probe is disposed downstream of the oxygen storage catalyst. The exhaust treatment apparatus according to claim 1, wherein the oxygen storage catalyst comprises a ceria catalyst containing ceria as the oxygen storage material. The exhaust treatment apparatus of claim 1 or 2, wherein the SCR catalyst is configured by applying an SCR catalyst layer to a porous filter configured to collect particulate matter in the diesel exhaust. The exhaust treatment apparatus according to any one of claims 1-3, wherein the SCR catalyst and the oxygen storage catalyst form an integral catalyst using a porous filter, and wherein the integral catalyst comprises: a porous filter; an SCR catalyst layer applied to an exhaust inlet of the filter; and an oxygen storage catalyst layer which is attached to an exhaust gas outlet of the filter and contains an oxygen storage material and a noble metal. The exhaust treatment apparatus of claim 4, wherein the filter is a porous filter configured to collect particulate matter in the diesel exhaust. The exhaust treatment apparatus of claim 4 or 5, wherein the filter has a plurality of multi-layer filter walls, and wherein facing surfaces of the plurality of filter walls alternately form exhaust gas inlets and exhaust outlets. The exhaust treatment apparatus of any of claims 1-6, wherein a diesel particulate filter is disposed between the LNT and the SCR catalyst. The exhaust treatment apparatus according to claim 7, wherein the SCR catalyst and the oxygen storage catalyst form an integral catalyst using a carrier, and wherein the integral catalyst is formed by applying the SCR catalyst layer and the oxygen storage Catalyst containing an oxygen storage material and a noble metal at a front portion and a rear portion of the carrier by a zone coating method. The exhaust treatment apparatus of any of claims 4-8, wherein the oxygen storage material comprises ceria. The exhaust treatment apparatus of any of claims 1-9, wherein the SCR catalyst layer of the SCR catalyst contains a zeolite catalyst. The exhaust treatment apparatus of any one of claims 1-10, wherein a rich operation for eliminating NO _x trapped in the LNT is maintained until the lambda values of the front lambda probe and the rear lambda probe coincide with each other during rich operation. A method for controlling an exhaust gas treating apparatus, wherein a lean _NOx trap (LNT), a Selective-Catalytic-reduction-(SCR) catalyst and an oxygen-storage-catalyst comprising a oxygen storage material and a Noble metal, arranged sequentially along an exhaust gas flow direction, and wherein a front lambda probe is disposed upstream of the LNT and a rear lambda probe is disposed downstream of the oxygen storage catalyst, the method comprising: measuring a temperature of exhaust gas by a temperature sensor, which in the exhaust path and eliminating NO _X by the SCR catalyst during rich operation when NH ₃ generated by the LNT and NO _x in the exhaust gas react with each other in the SCR catalyst. The method of exhaust treatment of claim 12, further comprising: Removing carbon monoxide (CO) and hydrocarbons (HC) in the exhaust gas by a noble metal contained in the oxygen storage catalyst. The method of exhaust treatment of claim 12 or 13, further comprising: maintaining rich operation to remove NO _X trapped in the LNT until the lambda values of the front lambda probe and the rear lambda probe coincide. The exhaust treatment method according to claim 14, wherein □ is a period of time (t _bt ) from the start time of rich operation to a time when the lambda values of the front lambda probe and the rear lambda probe coincide, the method further comprising: measuring a temperature of exhaust gas through a temperature sensor. The exhaust treatment method according to any one of claims 12-15, wherein the oxygen storage catalyst is a ceria catalyst having ceria as an oxygen storage material. The exhaust treatment process of any of claims 12-16, wherein the SCR catalyst is formed by applying an SCR catalyst layer to a porous filter configured to collect particulate matter in the diesel exhaust. The exhaust treatment process of any one of claims 12-17, wherein a diesel particulate filter is disposed between the LNT and the SCR catalyst. The exhaust treatment process of any of claims 12-18, wherein the SCR catalyst layer of the SCR catalyst contains a zeolite catalyst.

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