KR20180123917A - Device for purifying exhaust gas - Google Patents

Abstract

The present invention discloses an exhaust gas purifying device capable of improving exhaust gas purifying performance. The exhaust gas purifying device which is provided to purify an exhaust gas of an engine comprises: a warm-up catalytic converter (WCC) installed in an exhaust line; and an under floor catalytic converter (UCC) located on a rear end of the WCC. The WCC includes an LTA zeolite catalyst and can include a hydrocarbon absorber catalyst selectively absorbing or desorbing hydrocarbon according to a temperature of the exhaust gas.

Description

TECHNICAL FIELD [0001] The present invention relates to a device for purifying exhaust gas,

The present invention relates to an exhaust gas purifying apparatus, and more particularly, to an exhaust gas purifying apparatus capable of reducing harmful substances in exhaust gas by using an LTA zeolite catalyst having improved high-temperature performance.

Generally, a vehicle uses an engine to burn fuel, thereby generating power necessary for driving the vehicle. Combustion gas is inevitably generated in the combustion process of the fuel using the engine, and such combustion gas (exhaust gas) is released to the atmosphere through the exhaust device.

2. Description of the Related Art In recent years, as the interest in the global environment has increased, many researches and developments are under way to reduce harmful substances contained in exhaust gas emitted from vehicles.

Particularly, exhaust gas discharged from a diesel engine or a gasoline engine used in a vehicle is making a lot of efforts to reduce particulate matter and nitrogen oxides (NOx), which are particularly harmful to the global environment.

In order to reduce harmful substances contained in the exhaust gas such as particulate matter and nitrogen oxides, a filter and a catalyst are usually used. For example, the three-way catalyst is discharged from the engine when the temperature of the exhaust gas is 400 ° C or higher Such as carbon monoxide (CO), nitrogen oxides (HC), carbon monoxide (CO), nitrogen oxides, and the like, is almost completely purified, but the purification performance is deteriorated in the cold start period of the vehicle, and a large amount of harmful substances are discharged.

A hydrocarbon storage catalyst (HC Trap) and a nitrogen oxide storage catalyst (NOx trap) were introduced in order to reduce harmful substances in the exhaust gas during the cold starting period of the vehicle. After completion of the warm-up of the three-way catalyst, HC and NOX discharged in the cold start section are temporarily adsorbed in the adsorption catalyst, and HC and NOX desorbed from the adsorption catalyst at the end of the warm- And can be purified through a catalyst.

1 is a view schematically showing a structure of an exhaust gas purifying apparatus according to the prior art.

1, a catalytic device used in an exhaust gas purifying apparatus according to the related art includes a warm-up catalytic converter (WCC) installed to be directly connected to the exhaust manifold in close proximity to the engine 10, An underfloor catalytic converter (UCC) 30 installed at the bottom of the intermediate vehicle of the muffler pipe at a certain distance from the exhaust manifold, and the like. The warm-up catalytic converter 20 includes a three-way catalyst 22 and the underflow catalytic converter 30 includes a storage catalyst 32 and a three-way catalyst 34.

 That is, most Zeolite-type storage catalysts 32 are disposed in the underfloor catalytic converter 30 together with the three-way catalysts 34 because of lack of high-temperature heat resistance. Therefore, in the underfloor catalytic converter 30, the warm-up speed of the three-way catalyst 34 is slow, so that HC and NOX are desorbed before the three-way catalyst 34 is activated.

The matters described in the background section are intended to enhance the understanding of the background of the invention and may include matters not previously known to those skilled in the art.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an exhaust gas purifying apparatus capable of improving exhaust gas purifying performance by applying an LTA zeolite catalyst to a storage catalyst.

An exhaust gas purifying apparatus according to an embodiment of the present invention includes a warm-up catalytic converter (WCC) installed in an exhaust line of an exhaust gas purifying apparatus for purifying exhaust gas of an engine, The warm up catalytic converter includes a hydrocarbon storage catalyst for selectively storing or desorbing hydrocarbons according to the temperature of the exhaust gas.

The hydrocarbon storage catalyst may be disposed in an engine room of a vehicle.

The hydrocarbon storage catalyst may include an LTA zeolite catalyst.

The LTA zeolite catalyst included in the hydrocarbon storage catalyst may include at least one of an alkali metal, an alkaline earth metal, and a transition metal.

The content of the metal ion with respect to the total weight of the LTA zeolite catalyst may be 0.5 wt% to 3 wt%.

The warm-up catalytic converter may further include a three way catalyst (TWC) for purifying the hydrocarbon desorbed from the hydrocarbon storage catalyst.

The three-way catalyst and the hydrocarbon storage catalyst may be at least one of a zone coating structure, a physical mixing structure, a dual-layer structure, or an extruded zeolite substrate structure Structure.

And a control unit for controlling the exhaust gas to be lean to remove the hydrocarbon when the temperature of the exhaust gas reaches or exceeds a predetermined value and the hydrocarbon is desorbed .

An exhaust gas purifying apparatus according to an embodiment of the present invention includes a warm-up catalytic converter (WCC) installed in an exhaust line of an exhaust gas purifying apparatus for purifying exhaust gas of an engine, The warm-up catalytic converter includes a NOx storage catalyst that occludes nitrogen oxides discharged from the exhaust gas, and desorbs the stored nitrogen oxides when the temperature of the catalyst reaches a predetermined value or more.

The NOX storing catalyst may include an LTA zeolite catalyst.

The warm-up catalytic converter may include a three way catalyst (TWC) for purifying the nitrogen oxide desorbed from the NOX storing catalyst.

The three-way catalyst and the NOx storage catalyst may be at least one of a zone coating structure, a physical mixing structure, a dual-layer structure, or an extruded zeolite substrate structure Structure.

The LTA zeolite catalyst included in the NOx storage catalyst may include at least one of Pt, Pd, Rh, Ru, Ir, Os, Ag, and Au.

The content of the metal ion with respect to the total weight of the LTA zeolite catalyst may be 1 wt% to 2 wt%.

An exhaust gas purifying apparatus according to an embodiment of the present invention includes an exhaust line through which exhaust gas discharged from the engine passes and an exhaust line through which the exhaust gas is exhausted from the engine The warm-up catalytic converter includes an LTA zeolite catalyst, and includes a storage catalyst for storing or desorbing harmful substances discharged from the exhaust gas. The warm-up catalytic converter includes a warm-up catalytic converter (WCC).

The warm-up catalytic converter may further include a three way catalytic converter (TWC) for purifying the harmful substances desorbed from the adsorption catalyst.

The storage catalyst may be disposed at the front end of the three-way catalyst.

Wherein the storage catalyst includes a hydrocarbon storage catalyst for selectively storing or desorbing hydrocarbons according to the temperature of the exhaust gas, and a nitrogen oxide storage device for storing the nitrogen oxide discharged from the exhaust gas, And a NOx storing catalyst for desorbing the NOx storing catalyst.

At least one of the hydrocarbon storage catalyst and the NOx storage catalyst and the three-way catalyst may be a zone coating structure, a physical mixing structure, a dual-layer structure, or an extruded zeolite support Zeolite substrate structure.

As described above, by applying the LTA zeolite catalyst improved in high-temperature performance to the storage catalyst and arranging it in the warm-up catalytic converter close to the engine, it is possible to increase the heat resistance of the catalyst in the gasoline engine, And the like.

1 is a view schematically showing a structure of an exhaust gas purifying apparatus according to the prior art.
2 is a schematic view illustrating an exhaust system to which an exhaust gas purifying apparatus according to an embodiment of the present invention is applied.
3 is a view schematically showing a structure of an exhaust gas purifying apparatus according to an embodiment of the present invention.
4 is a view illustrating an example of forming a warm up catalytic converter with a hydrocarbon storage catalyst and a three-way catalyst according to an embodiment of the present invention.
5 is a view showing an example of forming a warm-up catalytic converter with a NOx storage catalyst and a three-way catalyst according to another embodiment of the present invention.
FIG. 6 is a view showing an example of forming a warm up catalyst converter with a hydrocarbon storage catalyst, an NOx storage catalyst, and a three-way catalyst according to another embodiment of the present invention.
FIG. 7 is a flowchart briefly illustrating a process of purifying harmful substances in an exhaust gas according to an embodiment of the present invention. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The exhaust gas purifying apparatus according to the embodiment of the present invention can be applied not only to a vehicle but also to various devices for obtaining energy by burning fossil fuel and discharging gas generated in the process to the atmosphere. In this specification, the exhaust gas purifying apparatus is applied to a vehicle, but it should not be construed as being applied only to a vehicle.

The vehicle is equipped with an engine for generating power. The engine combusts a mixture of fuel and air to convert chemical energy into mechanical energy. The engine is connected to an intake manifold to introduce air into the combustion chamber, and is connected to an exhaust manifold so that the exhaust gas generated in the combustion process is collected in the exhaust manifold and discharged to the outside of the vehicle. An injector is mounted on the combustion chamber or the intake manifold to inject fuel into the combustion chamber or the intake manifold.

The exhaust gas generated in the engine is discharged to the outside of the vehicle through the exhaust gas. The exhaust device may include an exhaust pipe and an exhaust gas recirculation (EGR) device.

The exhaust pipe is connected to the exhaust manifold to exhaust the exhaust gas to the outside of the vehicle.

The exhaust gas recirculation device is mounted on the exhaust pipe, and the exhaust gas discharged from the engine passes through the exhaust gas recirculation device. The exhaust gas recirculation device is connected to the intake manifold to mix a part of the exhaust gas with the air to control the combustion temperature. Such a combustion temperature can be adjusted by controlling ON / OFF of an EGR valve (not shown) provided in the exhaust gas recirculation device. That is, the amount of exhaust gas supplied to the intake manifold is regulated by controlling ON / OFF of the EGR valve.

The exhaust device may further include a soot filter mounted on the exhaust pipe and collecting particulate matter contained in the exhaust gas. The particulate filter may be an exhaust gas purifying apparatus according to an embodiment of the present invention for purifying harmful substances other than the particulate matter contained in the exhaust gas.

Hereinafter, an exhaust gas purifying apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a view briefly showing an exhaust system to which an exhaust gas purifying apparatus according to an embodiment of the present invention is applied, and FIG. 3 is a view schematically showing a structure of an exhaust gas purifying apparatus according to an embodiment of the present invention . At this time, the exhaust gas purifying apparatus shows only the schematic configuration necessary for the explanation according to the embodiment of the present invention, but the present invention is not limited to this configuration.

2 and 3, an exhaust gas purifying apparatus according to an embodiment of the present invention includes an exhaust line 105 through which exhaust gas exhausted from the engine 100 passes, exhaust gas exhausted from the engine 100 A warm-up catalytic converter (WCC) 200 installed on a passing exhaust line 104 and an under floor catalytic converter 200 disposed on the downstream side of the warm-up catalytic converter 200, A control unit 400 for controlling the absorption and desorption of harmful substances in the storage catalyst 210 of the warming up catalytic converter 200 and controlling the exhaust gas in a lean state according to the temperature of the exhaust gas do.

The warm-up catalytic converter 200 includes a storage catalyst 210, a three-way catalyst (TWC) 220, a front end oxygen sensor 230, and a rear end catalyst 210 disposed in an engine room of a vehicle according to an embodiment of the present invention. An oxygen sensor 240 is disposed.

The storage catalyst 210 includes an LTA zeolite catalyst having improved high-temperature performance according to an embodiment of the present invention, and absorbs or desorbs harmful substances discharged from the exhaust gas. Here, the harmful substance includes hydrocarbons and nitrogen oxides contained in the exhaust gas.

Conventional Zeolite-type occlusion catalysts have a problem that the structure collapses at 850 DEG C because of the lack of high-temperature heat resistance. However, the LTA zeolite catalyst has an advantage that the structure is maintained even after aging at a high temperature of 900 ° C. or higher. Therefore, the storage catalyst 210 according to one embodiment of the present invention can be disposed at a position close to the engine within the engine room of the vehicle by using the LTA zeolite catalyst with improved high-temperature performance.

The three-way catalyst 220 purifies the harmful substances desorbed from the storage catalyst 210.

The front stage oxygen sensor 230 and the rear stage oxygen sensor 240 sense the oxygen concentration of the exhaust gas passing through the exhaust line 105 and apply the signal to the control unit 400.

The controller 400 raises the temperature of the exhaust gas at the same time as the engine is cold and promotes the occlusion of harmful substances in the storage catalyst 210. When the temperature of the exhaust gas reaches or exceeds a predetermined value, the control unit 400 controls the exhaust gas to lean oxygen in order to remove the detoxified harmful substance .

For this purpose, the charge controller 400 may be implemented with one or more processors operating according to the program set, and the program set is programmed to perform each step of the exhaust gas purge method according to an embodiment of the present invention .

Here, the storage catalyst 210 may include at least one of a hydrocarbon storage catalyst (LTA HC Trap) including the LTA zeolite catalyst or a NOx storage catalyst (LTA NOx trap) including an LTA zeolite catalyst.

The hydrocarbon storage catalyst selectively stores or desorbs hydrocarbons according to the temperature of the exhaust gas. The NOx occlusion catalyst may occlude nitrogen oxides discharged from the exhaust gas, and when the temperature of the catalyst reaches a predetermined value or more, the adsorbed nitrogen oxides may be desorbed.

4 is a view illustrating an example of forming a warm up catalytic converter with a hydrocarbon storage catalyst and a three-way catalyst according to an embodiment of the present invention.

When the storage catalyst 210 includes the LTA HC Trap, the LTA zeolite catalyst included in the hydrocarbon storage catalyst may include at least one of an alkali metal, an alkaline earth metal, and a transition metal.

And, when the content of the metal ion is expressed as% by weight with respect to the weight of the total LTA zeolite catalyst, the content of the metal ion with respect to the total weight of the LTA zeolite catalyst may be 0.5 wt% to 5 wt%. And more preferably 0.5% by weight to 3% by weight, depending on the characteristics of the hydrocarbon storage catalyst.

4A shows an example of a physical mixing structure formed by mixing LTA HC Trap and TWC on a substrate. 4B is an example showing a zone coating structure in which LTA HC Trap is formed at the front end of the carrier and TWC is formed at the rear end of the LTA HC Trap.

4C shows an example of a dual-layer structure using LTA HC Trap and TWC. FIG. 4D shows an example of the structure of an extruded zeolite substrate constituting a carrier by LTA HC Trap.

5 is a view showing an example of forming a warm-up catalytic converter with a NOx storage catalyst and a three-way catalyst according to another embodiment of the present invention.

When the storage catalyst 210 includes the LTA NOx trap, the LTA zeolite catalyst included in the NOx storage catalyst may include at least one of Pt, Pd, Rh, Ru, Ir, Os, Ag, .

And, when the content of the metal ion is expressed as% by weight with respect to the weight of the total LTA zeolite catalyst, the content of the metal ion with respect to the total weight of the LTA zeolite catalyst may be 0.5 wt% to 5 wt%. More preferably from 1% by weight to 2% by weight, depending on the characteristics of the NOx storage catalyst.

5A is an example of a physical mixing structure formed by mixing LTA NOx Trap and TWC on a substrate. 5B is an example showing a zone coating structure in which LTA NOx Trap is formed at the front end of the carrier and TWC is formed at the rear end of the LTA NOx Trap.

5C shows an example of a dual-layer structure using an LTA NOx trap and a TWC. 5D shows an example of an extruded zeolite substrate structure constituting a carrier by LTA NOx Trap.

FIG. 6 is a view showing an example of forming a warm up catalyst converter with a hydrocarbon storage catalyst, an NOx storage catalyst, and a three-way catalyst according to another embodiment of the present invention.

6, an exhaust gas purifying apparatus according to an embodiment of the present invention includes a hydrocarbon storage catalyst (LTA HC Trap) including an LTA zeolite catalyst, an NOx storage catalyst (LTA NOx Trap) including an LTA zeolite catalyst, And the catalyst (TWC) may be combined to form the warm-up catalytic converter 200.

6A is an example of a physical mixing structure formed using the LTA HC Trap, the LTA NOx Trap, and the TWC. 6B shows a zone coating structure in which LTA HC Trap is formed at the front end of the carrier, LTA NOx Trap is formed at the rear end of the LTA HC Trap, and TWC is coated on the LTA HC Trap and LTA NOx Trap FIG.

FIG. 6C is a graph showing the results of an experiment in which the catalyst is divided into at least two bricks, and the LTA HC Trap is used as a carrier at the front end and the extruded zeolite substrate ) Structure.

FIG. 7 is a flowchart briefly illustrating a process of purifying harmful substances in an exhaust gas according to an embodiment of the present invention. FIG. The following flowcharts will be described using the same reference numerals in connection with the configurations of FIG. 2 and FIG.

Referring to FIG. 7, the exhaust gas purifying apparatus according to an embodiment of the present invention measures the temperature of the exhaust gas at the initial start of the vehicle (S102, S104).

Here, the exhaust gas purifier can model the temperature of the exhaust gas in accordance with the change of the engine operating variable, and determine the temperature of the exhaust gas in consideration of the distance from the engine exhaust valve and the heat capacity. Here, the engine operating variable includes at least one of rpm, fuel amount, air amount, exhaust gas lambda value, exhaust gas flow rate, and spark timing of the engine 100.

Then, the exhaust gas purifier raises the temperature of the exhaust gas to promote the occlusion of the harmful substances in the storage catalyst 210 (S106). Here, the harmful substance includes hydrocarbons and nitrogen oxides contained in the exhaust gas.

When the exhaust gas purifying apparatus reaches the desorption start temperature at which the harmful substances are desorbed from the storage catalyst 210, the exhaust gas is controlled to a lean state to increase the purification rate of the desorbed harmful substances (S110) .

For example, when an LTA having excellent durability at high temperature is applied to a hydrocarbon storage catalyst as an occlusion material, an exhaust gas purifying apparatus according to an embodiment of the present invention can install a hydrocarbon storage catalyst in a WCC close to the engine. Therefore, the exhaust gas purifying apparatus according to an embodiment of the present invention is advantageous for the purification of HC because the rate at which the hydrocarbon storage catalyst is activated after adsorbing the hydrocarbon (HC) is high.

Also, since it is located upstream of the three-way catalyst at the time of desorption, there is no oxygen consumption due to the oxygen storage capacity (OSC) of the three-way catalyst during lean operation. Therefore, the exhaust gas purifying apparatus according to an embodiment of the present invention can form a sufficient oxygen atmosphere and is effective for HC purification.

When the temperature of the storage catalyst 210 exceeds the predetermined desorption end temperature, the exhaust gas purification apparatus terminates lean control (S112).

As described above, the exhaust gas purifying apparatus according to an embodiment of the present invention increases the heat resistance of the catalyst in a gasoline engine by applying an LTA zeolite catalyst having improved high-temperature performance to the storage catalyst and arranging the LTA zeolite catalyst in a warm- Thereby improving the purification performance of harmful substances and improving the fuel efficiency.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And all changes to the scope that are deemed to be valid.

Claims (19)

1. An exhaust gas purifying apparatus for purifying exhaust gas of an engine, comprising:
And a warm-up catalytic converter (WCC) installed in the exhaust line,
The warm-up catalytic converter includes:
A hydrocarbon storage catalyst for selectively storing or desorbing hydrocarbons according to the temperature of the exhaust gas
And an exhaust gas purifying device for purifying exhaust gas. The method according to claim 1,
The hydrocarbon storage catalyst may contain,
An exhaust gas purifier arranged in an engine room of a vehicle. 3. The method of claim 2,
The hydrocarbon storage catalyst may contain,
LTA zeolite catalyst. The method of claim 3,
The LTA zeolite catalyst contained in the hydrocarbon storage catalyst may be,
Wherein the exhaust gas purifying apparatus comprises at least one of an alkali metal, an alkaline earth metal, and a transition metal. 5. The method of claim 4,
Wherein the content of the metal ion with respect to the total weight of the LTA zeolite catalyst is 0.5 wt% to 3 wt%. The method according to claim 1,
The warm-up catalytic converter includes:
A three way catalyst (TWC) for purifying the hydrocarbon desorbed in the hydrocarbon storage catalyst,
And an exhaust gas purifying device for purifying exhaust gas. The method according to claim 6,
Wherein the three-way catalyst and the hydrocarbon storage catalyst are adsorbed on the three-
The exhaust gas purifying apparatus is formed with at least one structure of a zone coating structure, a physical mixing structure, a dual-layer structure, or an extruded zeolite substrate structure. The method according to claim 1,
And a control unit for controlling the exhaust gas to be lean to remove the hydrocarbon when the temperature of the exhaust gas reaches or exceeds a predetermined value and the hydrocarbon is desorbed And an exhaust gas purifying device. 1. An exhaust gas purifying apparatus for purifying exhaust gas of an engine, comprising:
And a warm-up catalytic converter (WCC) installed in the exhaust line,
The warm-up catalytic converter includes:
A NOx adsorption catalyst for adsorbing nitrogen oxides discharged from the exhaust gas and desorbing nitrogen oxides occluded when the temperature of the catalyst reaches a predetermined value or more;
And an exhaust gas purifying device for purifying exhaust gas. 10. The method of claim 9,
The NOX storing catalyst includes:
LTA zeolite catalyst. 10. The method of claim 9,
The warm-up catalytic converter includes:
A three way catalyst (TWC) for purifying the nitrogen oxide desorbed in the NOx storage catalyst,
And an exhaust gas purifying device for purifying exhaust gas. 12. The method of claim 11,
Wherein the three-way catalyst and the NOx storage catalyst,
The exhaust gas purifying apparatus is formed with at least one structure of a zone coating structure, a physical mixing structure, a dual-layer structure, or an extruded zeolite substrate structure. 11. The method of claim 10,
Wherein the LTA zeolite catalyst contained in the NOx storage catalyst comprises
And at least one of Pt, Pd, Rh, Ru, Ir, Os, Ag, or Au. 14. The method of claim 13,
Wherein the content of the metal ion with respect to the total weight of the LTA zeolite catalyst is 1 wt% to 2 wt%. 1. An exhaust gas purifying apparatus for purifying exhaust gas of an engine, comprising:
An exhaust line through which the exhaust gas discharged from the engine passes, and
And a warm-up catalytic converter (WCC) installed in the exhaust line,
The warm-up catalytic converter includes:
And an LTA zeolite catalyst, wherein the absorption catalyst for adsorbing or desorbing harmful substances discharged from the exhaust gas
And an exhaust gas purifying device for purifying exhaust gas. 16. The method of claim 15,
The warm-up catalytic converter includes:
Further comprising a three way catalyst (TWC) for purifying the harmful substances desorbed from the storage catalyst. 17. The method of claim 16,
The storage catalyst,
Wherein the exhaust gas purifying apparatus is disposed at a front end of the three-way catalyst. 18. The method of claim 17,
The storage catalyst,
A hydrocarbon storage catalyst for selectively storing or desorbing hydrocarbons according to the temperature of the exhaust gas, and
A NOx adsorption catalyst for adsorbing nitrogen oxides discharged from the exhaust gas and desorbing the adsorbed nitrogen oxides when the temperature of the catalyst reaches a predetermined value or more;
And an exhaust gas purifying device for purifying exhaust gas. 19. The method of claim 18,
Wherein at least one of the hydrocarbon storage catalyst or the NOx storage catalyst and the three-
The exhaust gas purifying apparatus is formed with at least one structure of a zone coating structure, a physical mixing structure, a dual-layer structure, or an extruded zeolite substrate structure.

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