KR101416352B1 - Diesel fuel cracking catalyst and lean nox trap provided with the same - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to a diesel fuel decomposition catalyst and a nitrogen oxide storage catalyst having the same, which improve the purification efficiency of nitrogen oxide by converting hydrocarbons contained in the exhaust gas into hydrocarbons having an alcohol group having high reducing characteristics.

The nitrogen oxide storage catalyst according to an embodiment of the present invention is mounted on an exhaust pipe for discharging the exhaust gas generated in the engine to the outside and reduces the nitrogen oxide contained in the exhaust gas, Wherein the diesel fuel decomposing catalyst converts the hydrocarbon contained in the exhaust gas into a hydrocarbon having an alcohol group, and when the exhaust gas is lean, the hydrocarbon having the alcohol group is adsorbed And the nitrogen oxide storage layer absorbs the nitrogen oxide contained in the exhaust gas when the exhaust gas is lean and absorbs the nitrogen oxide which is adsorbed when the exhaust gas is rich And the nitrogen reduction layer is made of a mixture of hydrocarbons and < RTI ID = 0.0 > Using a hydrocarbon having an alcohol group generated from the carbon and the diesel fuel cracking catalyst can reduce the nitrogen oxides in the exhaust gas.

Thermal cracking, nitrogen oxide storage catalyst, diesel fuel cracking catalyst

Description

TECHNICAL FIELD [0001] The present invention relates to a diesel fuel decomposition catalyst and a nitrogen oxide storage catalyst having the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel fuel decomposition catalyst and a nitrogen oxide storage catalyst having the same, and more particularly, to a diesel fuel decomposition catalyst comprising a diesel fuel decomposition catalyst having improved efficiency of purifying nitrogen oxides by converting hydrocarbons contained in exhaust gases into hydrocarbons having alcohol groups A fuel decomposition catalyst and a nitrogen oxide storage catalyst having the same.

Generally, the exhaust gas discharged from the engine through the exhaust manifold is guided to a catalytic converter formed in the middle of the exhaust pipe to be purified, passes through the muffler and attenuates the noise, and then is discharged to the atmosphere through the tail pipe. The above-described catalytic converter is a type of diesel particulate filter (DPF), which treats contaminants contained in exhaust gas. A catalyst carrier for trapping particulate matter (PM) contained in the exhaust gas is formed in the catalytic converter, and various exhaust gases discharged from the engine are purified through a chemical conversion process.

One of the catalyst types applicable to the catalytic converter having the above-described role is a NOx trap (Lean NOx Trap). The nitrogen oxide storage catalyst adsorbs nitrogen oxides when the exhaust gas is lean (when the oxygen concentration in the exhaust gas is high) and desorbs the adsorbed nitrogen oxides when the oxygen concentration in the exhaust gas is low, so that the hydrocarbons contained in the exhaust gas Carbon monoxide is oxidized and nitrogen oxides are reduced, thereby reducing harmful substances such as hydrocarbons, carbon monoxide and nitrogen oxides contained in the exhaust gas.

On the other hand, in the case of the internal combustion engine equipped with the nitrogen oxide storage catalyst, when the amount of nitrogen oxide adsorbed on the nitrogen oxide storage catalyst is large, the oxygen concentration in the exhaust gas is arbitrarily lowered through additional injection of fuel, . This is called regeneration of the nitrogen oxide storage catalyst.

Further, when the nitrogen oxide storage catalyst is mounted on the internal combustion engine, a diesel fuel decomposition catalyst is provided to decompose the fuel to help reduce the nitrogen oxide. The diesel fuel cracking catalyst breaks down the chain link of the carbon element constituting the fuel through the thermal cracking function and the fuel is converted into ethylene (C ₂ H ₂ ) and carbon monoxide (CO) through the steam reforming function and the partial oxidation function .

Conventional diesel fuel cracking catalyst forms a reducing agent through thermal cracking and partial oxidation by oxygen. However, when oxygen reacts with the fuel, a complete oxidation reaction by oxygen occurs and carbon dioxide (CO ₂ ) is generated. As a result, the efficiency of generating a reducing agent was lowered.

In addition, the reaction of oxygen and fuel to produce a reducing agent occurred at a relatively high temperature of 250 ° C or higher, thereby further reducing the reducing agent production efficiency.

Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a diesel particulate filter which converts the hydrocarbon contained in the exhaust gas into a hydrocarbon having an alcohol- A fuel decomposition catalyst and a nitrogen oxide storage catalyst having the same.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a diesel fuel decomposition catalyst, comprising: an exhaust pipe for exhausting exhaust gas generated in an engine; A nitrogen oxide layer which oxidizes nitrogen monoxide contained in the exhaust gas to nitrogen dioxide and adsorbs part of the oxidized nitrogen dioxide when the exhaust gas leans; The other part of the hydrocarbons are converted into hydrocarbons having an alcohol group by using the nitrogen dioxide produced in the nitrogen oxide layer. When the exhaust gas is lean, the hydrocarbons having the alcohol group are adsorbed And an alcohol-generating layer.

Regardless of whether the exhaust gas is rich or lean, the nitrogen oxide layer always oxidizes nitrogen monoxide to nitrogen dioxide, and the alcohol-generating layer can always produce hydrocarbons having the alcohol group.

The diesel fuel decomposition catalyst may desorb and supply a hydrocarbon having an alcohol group adsorbed on the alcohol generating layer when the exhaust gas is rich.

When the exhaust gas is rich, the nitrogen oxide layer desorbs the adsorbed nitrogen dioxide and supplies the desorbed nitrogen dioxide to the alcohol-producing layer, thereby promoting the generation of hydrocarbons having an alcohol group.

The nitrogen oxide layer may be an alumina-ceria (Al ₂ O ₃ -CeO ₂ ) complex catalyst carrying platinum (Pt).

The alcohol generating layer may be a zeolite catalyst carrying palladium (Pd).

A nitrogen oxide storage catalyst according to another embodiment of the present invention is mounted on an exhaust pipe for exhausting exhaust gas generated in an engine to reduce nitrogen oxide contained in the exhaust gas, A diesel fuel decomposition catalyst, a nitrogen oxide storage node, and a nitrogen reduction layer, wherein the diesel fuel decomposition catalyst converts the hydrocarbon contained in the exhaust gas into a hydrocarbon having an alcohol group, and when the exhaust gas is lean, the hydrocarbon having the alcohol group The nitrogen oxide storage layer adsorbs the nitrogen oxide contained in the exhaust gas when the exhaust gas is lean, and when the exhaust gas is rich, the adsorbed nitrogen oxide is adsorbed to the nitrogen oxide storage layer, and when the exhaust gas is rich, And the nitrogen reduction layer is formed by removing the hydrocarbon and / Nitrogen oxides in the exhaust gas can be reduced using carbon monoxide and hydrocarbons having an alcohol group generated from the diesel fuel decomposition catalyst.

When the exhaust gas is rich, the nitrogen oxide storage function layer can promote the reduction of nitrogen oxide by supplying desorbed nitrogen oxide to the nitrogen reduction layer.

The diesel fuel decomposition catalyst includes a nitrogen oxide layer for oxidizing nitrogen monoxide contained in exhaust gas to nitrogen dioxide, and adsorbing a part of oxidized nitrogen monoxide when the exhaust gas is lean; The other part of the hydrocarbons are converted into hydrocarbons having an alcohol group by using the nitrogen dioxide produced in the nitrogen oxide layer. When the exhaust gas is lean, the hydrocarbons having the alcohol group are adsorbed And an alcohol-generating layer.

When the exhaust gas is rich, the diesel fuel decomposition catalyst may desorb the hydrocarbon having an alcohol group adsorbed on the alcohol generation layer and supply the hydrocarbon to the nitrogen reduction layer.

When the exhaust gas is rich, the nitrogen oxide layer desorbs the adsorbed nitrogen dioxide and supplies the desorbed nitrogen dioxide to the alcohol-producing layer, thereby promoting the generation of hydrocarbons having an alcohol group.

The nitrogen oxide layer may be an alumina-ceria (Al ₂ O ₃ -CeO ₂ ) complex catalyst carrying platinum (Pt).

The alcohol generating layer may be a zeolite catalyst carrying palladium (Pd).

The nitrogen oxide occlusion layer may be coated with barium (Ba) on the alumina support.

The nitrogen reduction layer may be coated with at least one of platinum (Pt), palladium (Pd), and rhodium (Rh) on the alumina support.

As described above, according to the present invention, the efficiency of purifying nitrogen oxides is enhanced by converting hydrocarbons contained in the exhaust gas into hydrocarbons having an alcohol group having high reducing characteristics.

Furthermore, since the reducing agent generating reaction takes place at a low temperature, the purification efficiency of the nitrogen oxide is further improved.

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

1 is a schematic view showing an example of an internal combustion engine in which a nitrogen oxide storage catalyst having a diesel fuel decomposition catalyst according to an embodiment of the present invention is mounted.

1, the internal combustion engine includes an engine 10, an exhaust pipe 20, a diesel particulate filter (DPF) 30, a nitrogen oxide storage catalyst 40 (Lean NOx trap) And a control unit 50.

The engine 10 converts chemical energy into mechanical energy by burning a mixture in which fuel and air are mixed. The engine 10 is connected to an intake manifold (not shown) to receive air into the combustion chamber 12 and connected to the exhaust manifold 16 so that the exhaust gas generated in the combustion process is supplied to the exhaust manifold 16, And then discharged to the outside of the vehicle. The first injector 14 is mounted in the combustion chamber 12 to inject fuel into the combustion chamber 12.

Although a diesel engine is exemplified here, a gasoline engine may be used. When a gasoline engine is used, the mixer is introduced into the combustion chamber 12 through the intake manifold, and an ignition plug for ignition is mounted on the combustion chamber 12 above the combustion chamber 12.

The exhaust pipe 20 is connected to the exhaust manifold 16 to exhaust the exhaust gas to the outside of the vehicle. A diesel particulate filter 30 and a nitrogen oxide storage catalyst 40 are mounted on the exhaust pipe 20 to remove hydrocarbons, carbon monoxide, and nitrogen oxides contained in the exhaust gas.

The diesel particulate filter 30 collects particulate materials (PM) contained in the exhaust gas discharged through the exhaust pipe 20. A diesel oxidation catalyst (DOC) 32 is coated on the front end of the diesel particulate filter 30 to oxidize carbon monoxide and carbon dioxide contained in the exhaust gas to carbon dioxide. The nitrogen monoxide contained in the exhaust gas Is oxidized to nitrogen dioxide. Here, the diesel oxidation catalyst 32 is coated on the front end portion of the diesel particulate filter 30, but the present invention is not limited thereto. That is, the diesel oxidation catalyst 32 may be coated over the entire area of the diesel particulate filter 30, or may be coated in a predetermined area.

A differential pressure sensor 55 is mounted on the front end and the rear end of the diesel particulate filter 30. The differential pressure sensor 55 measures a pressure difference between the front end and the rear end of the diesel particulate filter 30 and transmits a signal to the controller 50. The control unit 50 can control the diesel particulate filter 30 to regenerate when the pressure difference measured by the differential pressure sensor 55 is equal to or greater than a set value. In this case, the first injector 14 controls the fuel Soot collected in the diesel particulate filter 30 can be burned.

An oxygen sensor (60) and a second injector (70) are mounted on the exhaust pipe (20) behind the diesel particulate filter (30).

The oxygen sensor 60 measures a current lambda value (?: Excess air ratio), which is a ratio of the actual air-fuel ratio to the stoichiometric air-fuel ratio, and transmits a signal to the controller 50.

The second injector 70 is electrically connected to the controller 50 and performs secondary fuel injection in the exhaust pipe 20 under the control of the controller 50. Here, the second injector 70 is provided on the exhaust pipe 20, but the present invention is not limited thereto. That is, a separate second injector 70 may be installed in the engine 10 to perform additional injection, or the first injector 14 may perform post injection.

The nitrogen oxide storage catalyst 40 is mounted on the exhaust pipe 20 to the rear of the second injector 70 so as to adsorb nitrogen oxides or to perform a reduction reaction after desorption depending on whether the condition is satisfied or not, Purifies the contained nitrogen oxides.

A diesel fuel cracking catalyst (DFC) 42 is coated on the front end of the nitrogen oxide storage catalyst 40. Here, the diesel fuel decomposition catalyst 42 is provided in the nitrogen oxide storage device 40, but the diesel fuel decomposition catalyst 42 may be provided outside the nitrogen oxide storage device 40.

The diesel fuel decomposition catalyst 42 breaks the chain link of the carbon element through the catalytic reaction to decompose the fuel. In other words, the diesel fuel cracking catalyst 42 breaks off the carbon linkage constituting the hydrocarbon compound, which is the main component of the fuel, through the thermal cracking function for decomposing the fuel.

Thermal cracking is performed through the following procedure.

C ₁₆ H ₃₄ ? 2n-C ₈ H ₁₇ *? N C ₆ H ₁₃ *? N C ₄ H ₉ *? C ₂ H ₅ *? C ₂ H ₄

C ₁₆ H ₃₄ ? 8 C ₂ H ₄ + H ₂

Here, * denotes a radical.

As shown in FIG. 2, the diesel fuel decomposition catalyst 42 is composed of two layers of a nitrogen oxide layer 424 and an alcohol generation layer 426.

The nitrogen oxide layer 424 oxidizes the nitrogen monoxide contained in the exhaust gas to nitrogen dioxide regardless of whether the exhaust gas is rich or not, and some of the oxidized nitrogen dioxide is adsorbed on the nitrogen oxide layer 424 when the exhaust gas is lean . The nitrogen dioxide adsorbed on the nitrogen oxide layer 424 is desorbed when the exhaust gas is rich and is supplied to the alcohol generation layer 426. Further, among the oxidized nitrogen dioxide, nitrogen dioxide which is not adsorbed to the nitrogen oxide layer 424 is supplied to the alcohol generation layer 426. The nitrogen oxide layer 424 may be composed of an alumina-ceria (Al ₂ O ₃ -CeO ₂ ) complex catalyst carrying platinum (Pt). The oxidation reaction proceeding in the nitrogen oxide layer 424 is as follows.

NO + O * → NO ₂ *

The alcohol generation layer 426 adsorbs some of the hydrocarbons contained in the exhaust gas irrespective of whether the exhaust gas is rich or lean and the other part of the hydrocarbons absorbs the hydrocarbons having an alcohol group using nitrogen dioxide generated in the nitrogen oxide layer 424. [ . The hydrocarbon having the alcohol group thus formed is adsorbed on the alcohol generation layer 426 when the exhaust gas is lean. The hydrocarbon having the alcohol group adsorbed on the alcohol generation layer 426 is desorbed when the exhaust gas is rich and is supplied to the nitrogen oxide storage catalyst 40. The alcohol generating layer 426 may be composed of palladium (Pd) -doped zeolite catalyst. The reaction progressed in the alcohol generation layer 426 is as follows.

C _x H _y + NO ₂ *? C _x H _y-1 -OH + NO

The nitrogen oxide storage catalyst 40 is coated with a nitrogen oxide storage layer 406 and a nitrogen reduction layer 404 on a support 402.

The nitrogen oxide storage node 406 adsorbs nitrogen oxide in the exhaust gas in the nitrate form when the exhaust gas is liquefied, and desorbs the adsorbed nitrogen oxide when the exhaust gas is rich, and supplies the desorbed nitrogen oxide to the nitrogen reduction layer 404. The nitrogen oxide storage node layer 406 may be formed by coating an alumina (Al ₂ O ₃ ) carrier with barium (Ba).

The nitrogen reduction layer 404 reduces the nitrogen oxides in the exhaust gas by using hydrocarbons and carbon monoxide in the exhaust gas and hydrocarbons having the alcohol groups generated in the alcohol generation layer 426. Particularly, when the exhaust gas is rich, the hydrocarbon having the alcohol group generated in the alcohol generation layer 426 and the nitrogen oxide desorbed from the nitrogen oxide storage layer 406 are supplied in a large amount, thereby improving the purification efficiency of the exhaust gas. The nitrogen reduction layer 404 may be formed by coating at least one of platinum (Pt), palladium (Pd), and rhodium (Rh) on an alumina support. The reaction progressed in the nitrogen reduction layer 404 is roughly as follows.

C _x H _y -OH + NO _x ? CO ₂ + N ₂

A nitrogen storage amount sensor 65 is installed in front of or behind the nitrogen oxide storage catalyst 40 to detect the amount of nitrogen oxide adsorbed on the nitrogen oxide storage catalyst 40, . On the other hand, instead of using the nitrogen storage amount sensor 65, the storage amount of nitrogen oxide can be predicted from the map determined by the experimental value.

The control unit 50 regenerates the nitrogen oxide storage catalyst 40 by controlling the secondary fuel injection amount and the fuel injection timing that are injected from the second injector 70 based on the signals detected by the sensors 60 and 65 .

Hereinafter, the operation principle of the present invention will be described in detail.

When the exhaust gas turns on

When the oxygen concentration in the exhaust gas is high, the nitrogen oxide layer 424 stores a portion of the oxidized nitrogen dioxide and supplies the remaining nitrogen dioxide to the alcohol oxidizing layer 426.

In the alcohol generation layer 426, the nitrogen dioxide supplied from the nitrogen oxide layer 424 is reduced to nitrogen monoxide while the hydrocarbons in the exhaust gas are oxidized to hydrocarbons including alcohol groups. The hydrocarbon containing the alcohol group thus produced is stored in the alcohol generation layer 426 and the nitrogen monoxide is supplied to the nitrogen oxide storage catalyst 40 and adsorbed to the nitrogen oxide storage structure 406 in the nitrate form.

When the exhaust gas is rich

When the oxygen concentration in the exhaust gas is lowered, the nitrogen oxide layer 424 supplies nitrogen dioxide stored in the nitrogen oxide layer 424 together with the oxidized nitrogen dioxide to the alcohol generation layer 426.

As the amount of nitrogen dioxide supplied from the nitrogen oxide layer 424 increases, the alcohol generation layer 426 generates more hydrocarbons including alcohol groups and supplies the hydrocarbons together with the nitrogen monoxide to the nitrogen oxide storage catalyst 40. Also, the alcohol containing an alcohol group stored in the alcohol generation layer 426 is also supplied to the nitrogen oxide storage catalyst 40.

In addition, the nitrogen oxide storage node 406 desorbs the adsorbed nitrogen oxide and supplies it to the nitrogen reduction layer 404.

The nitrogen reduction layer 404 oxidizes hydrocarbons containing alcohol groups to carbon dioxide and reduces nitrogen oxides to nitrogen gas. In this case, since there are many hydrocarbons and nitrogen oxides containing an alcohol group to be supplied to the nitrogen reduction layer 404, an oxidation-reduction reaction takes place actively.

Further, since the reaction of generating an alcohol containing an alcohol group takes place at a relatively low temperature, there is no need to increase the temperature of the exhaust gas through post-injection or the like, which leads to an improvement in fuel economy.

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.

1 is a schematic view showing an example of an internal combustion engine in which a nitrogen oxide storage catalyst having a diesel fuel decomposition catalyst according to an embodiment of the present invention is mounted.

2 is a schematic view showing a configuration of a diesel fuel decomposition catalyst according to an embodiment of the present invention.

3 is a schematic view showing a configuration of a nitrogen oxide storage catalyst according to an embodiment of the present invention.

Claims (15)

 A diesel fuel cracking catalyst mounted on an exhaust pipe for exhausting exhaust gas generated from an engine to break a chain ring of a carbon element constituting fuel, A nitrogen oxide layer which oxidizes nitrogen monoxide contained in the exhaust gas to nitrogen dioxide and adsorbs a part of the oxidized nitrogen dioxide when the exhaust gas leans; And And the other part of the hydrocarbons is converted into hydrocarbons having an alcohol group by using nitrogen dioxide produced in the nitrogen oxide layer. When the exhaust gas is lean, the alcohol which adsorbs the hydrocarbon having the alcohol group Pyrogenic layer; Wherein the catalyst is a diesel fuel. The method according to claim 1, Wherein the nitrogen oxide layer always oxidizes nitrogen monoxide to nitrogen dioxide, and the alcohol generating layer always produces hydrocarbons having the alcohol group, regardless of whether the exhaust gas is rich or lean. 3. The method of claim 2, Wherein the diesel fuel decomposition catalyst desorbs and supplies a hydrocarbon having an alcohol group adsorbed on the alcohol generating layer when the exhaust gas is rich. 3. The method of claim 2, Wherein the nitrogen oxide layer desorbs the adsorbed nitrogen dioxide when the exhaust gas is rich, and supplies the adsorbed nitrogen dioxide to the alcohol gas generating layer to promote generation of hydrocarbons having an alcohol group. The method according to claim 1, Wherein the nitrogen oxide layer is a platinum (Pt) supported alumina-ceria (Al ₂ O ₃ -CeO ₂ ) complex catalyst. The method according to claim 1, Wherein the alcohol generating layer is a zeolite catalyst carrying palladium (Pd). A nitrogen oxide storage catalyst mounted on an exhaust pipe for discharging exhaust gas generated from an engine to reduce nitrogen oxide contained in exhaust gas, Wherein the nitrogen oxide storage catalyst includes a diesel fuel decomposition catalyst, a nitrogen oxide storage node layer, and a nitrogen reduction layer, The diesel fuel decomposition catalyst converts the hydrocarbon contained in the exhaust gas into a hydrocarbon having an alcohol group. When the exhaust gas is lean, the hydrocarbon having the alcohol group is adsorbed. When the exhaust gas is rich, the hydrocarbon having the alcohol group is desorbed , When the exhaust gas is lean, the nitrogen oxide absorption storage layer adsorbs the nitrogen oxide contained in the exhaust gas, desorbs the adsorbed nitrogen oxide when the exhaust gas is rich, and Wherein the nitrogen reduction layer reduces nitrogen oxides in the exhaust gas using hydrocarbons and carbon monoxide in the exhaust gas and hydrocarbons having alcohol groups generated in the diesel fuel decomposition catalyst. 8. The method of claim 7, Wherein the nitrogen oxide storage function layer promotes the reduction of nitrogen oxides by supplying desorbed nitrogen oxides to the nitrogen reduction layer when the exhaust gas is rich. 8. The method of claim 7, The diesel fuel cracking catalyst may be a catalyst, A nitrogen oxide layer for oxidizing nitrogen monoxide contained in the exhaust gas with nitrogen dioxide and adsorbing a part of oxidized nitrogen monoxide when the exhaust gas is lean; And And the other part of the hydrocarbons is converted into hydrocarbons having an alcohol group by using nitrogen dioxide produced in the nitrogen oxide layer. When the exhaust gas is lean, the alcohol which adsorbs the hydrocarbon having the alcohol group Pyrogenic layer; And a nitrogen oxide storage catalyst. 10. The method of claim 9, Wherein the diesel fuel decomposition catalyst desorbs the hydrocarbon having an alcohol group adsorbed on the alcohol generation layer when the exhaust gas is rich and supplies the hydrocarbon to the nitrogen reduction layer. 10. The method of claim 9, Wherein the nitrogen oxide layer desorbs the adsorbed nitrogen dioxide when the exhaust gas is rich and feeds the adsorbed nitrogen dioxide to the alcoholic gas generating layer to promote the generation of hydrocarbons having an alcohol group. 10. The method of claim 9, Wherein the nitrogen oxide layer is a platinum (Pt) supported alumina-ceria (Al ₂ O ₃ -CeO ₂ ) complex catalyst. 10. The method of claim 9, Wherein the alcohol generating layer is a zeolite catalyst carrying palladium (Pd). 8. The method of claim 7, Wherein the nitrogen oxide absorption storage layer is formed by coating barium (Ba) on an alumina support. 8. The method of claim 7, Wherein the nitrogen reduction layer is coated with at least one of platinum (Pt), palladium (Pd), and rhodium (Rh) on an alumina support.

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