KR100569482B1 - Device for purifying exhaust gas of diesel vehicle - Google Patents

Abstract

The present invention relates to an exhaust gas purification system of a diesel vehicle, and more particularly, a separate bypass pipe is installed in an upstream exhaust pipe of a catalytic converter in which a nitrogen oxide storage catalyst and a ceramic particulate filter are arranged in series. In this bypass tube, paraffin and olefins decomposed by installing a fuel decomposition catalyst employing a hydrocarbon decomposition catalyst that decomposes a paraffinic diesel oil having 12 or more carbon atoms having poor reduction characteristics of nitrogen oxides into lower paraffins and olefins having excellent reduction characteristics. The present invention relates to an exhaust gas purification system for a diesel vehicle, which flows through a catalytic converter and is provided with an injector for fuel injection upstream of the hydrocarbon decomposition catalyst.

In the exhaust gas purification system of the present invention, the low carbon number paraffin and olefin having excellent reducing ability of nitrogen oxide act as a reducing agent of nitrogen oxide in the nitrogen oxide storage catalyst of the catalytic converter, so that the removal efficiency of nitrogen oxide can be improved. In addition, according to the improvement of nitrogen oxide reduction efficiency in the nitrogen oxide storage catalyst, the amount of fuel injected through the injector may be reduced.

Vehicle, Exhaust gas, Purification system, Catalytic converter, Nitrogen oxide storage catalyst, Bypass pipe, Hydrocarbon decomposition catalyst, Nitrogen oxide, Selective reduction reaction, Engine

Description

Device for purifying exhaust gas of diesel vehicle             

1 is a schematic view showing an exhaust gas purification system of a diesel vehicle according to the present invention;

2 is a schematic view showing a conventional exhaust gas purification system for a diesel vehicle.

<Explanation of symbols for the main parts of the drawings>

1: exhaust pipe 3: bypass pipe

10 catalytic converter 12 nitrogen oxide storage catalyst

14 particulate matter filter 22 injector

30: fuel decomposition catalyst 32: hydrocarbon decomposition catalyst

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification system for a diesel vehicle, wherein a separate bypass pipe is provided in an upstream exhaust pipe of a catalytic converter in which a nitrogen oxide storage catalyst and a ceramic particulate filter are disposed in series. Paraffin and olefin decomposed into a catalytic converter by installing a fuel cracking catalyst employing a hydrocarbon cracking catalyst that decomposes a paraffinic diesel oil having 12 or more carbon atoms having poor reducing properties into lower paraffins and olefins having excellent reducing properties. The present invention relates to an exhaust gas purification system for a diesel vehicle, which improves the removal efficiency of nitrogen oxide, which is formed by flowing an injector for fuel injection upstream of the hydrocarbon decomposition catalyst.

In general, the exhaust gas of a vehicle refers to a gas in which a mixer combusted from an engine is released into the atmosphere through an exhaust pipe, and the exhaust gas mainly includes harmful substances such as carbon monoxide, nitrogen oxides (NOx), and unburned hydrocarbons.

On the other hand, although diesel engine vehicles are excellent in fuel economy and power output, unlike gasoline engines, the exhaust gas contains a considerable amount of nitrogen oxides and particulate matter (PM).

In other words, in a diesel vehicle, carbon monoxide and hydrocarbons are emitted much less than gasoline vehicles because air is sufficiently burned under most driving conditions, but nitrogen oxides and particulate matter (soot) are emitted much.

The nitrogen oxides (NOx) and particulate matter (PM) tend to have an inverse relationship with each other, that is, decreasing nitrogen oxides increases particulate matters, and conversely, nitrogen oxides tend to increase to reduce particulate matters.

Recently, particulate matter has been identified as the main cause of air pollution, and it has been found to cause many harms to the human body.

Accordingly, the exhaust gas reduction technology of diesel vehicles has been studied with a focus on the reduction of particulate matter including nitrogen oxides and soot, and the treatment of such nitrogen oxides and particulate matters is the most difficult and important.

To this end, as a post-treatment technology for coping with emission standards of diesel vehicles, a catalyst in which a nitrogen oxide storage catalyst 12 and a particulate matter filter 14 of ceramic material are arranged in series as shown in FIG. 2. Techniques using the converter 10 have been known.

Among them, the nitrogen oxide storage catalyst 12 contains a component of platinum and an alkali or alkaline metal oxide such as barium oxide.

In such an exhaust gas purification system, an injector 22 for fuel injection is installed in an exhaust pipe 1 upstream of the catalytic converter 10, and the ECU 20 has a nitrogen oxide sensor 16 installed at the rear of the catalytic converter 10. The amount of nitrogen oxide is input in the form of an electrical signal, and under the injection control of the ECU 20, the injector 22 injects fuel to the catalytic converter 10 upstream to form a reducing atmosphere.

In the nitrogen oxide absorbing catalyst 12, the nitrogen oxide is oxidized in an oxygen-excess atmosphere and occluded in the catalyst in the form of nitrate, and then the nitrate occluded in the reducing atmosphere by fuel injection is purged with nitrogen and oxygen. .

However, the nitrogen oxide removal process by this method is accompanied by the deterioration of fuel efficiency because the fuel is consumed in the reducing atmosphere composition step by the injection of fuel.

Therefore, there is an urgent need for an improvement method capable of reducing and removing nitrogen oxide more efficiently while having a small amount of fuel injection.

Accordingly, the present invention has been invented to solve the above problems, and a separate bypass pipe is provided in the upstream exhaust pipe of the catalytic converter in which the nitrogen oxide storage catalyst and the ceramic particulate filter are arranged in series. Paraffin and olefins decomposed by using a catalytic cracking catalyst employing a hydrocarbon cracking catalyst which decomposes a paraffinic diesel oil having 12 or more carbon atoms having poor reducing properties of nitrogen oxides into lower paraffins and olefins having excellent reducing properties. It is made to flow to the converter, and by installing an injector for fuel injection on the upstream side of the hydrocarbon decomposition catalyst, the removal efficiency of the nitrogen oxides can be improved, the injector in accordance with the increase of the nitrogen oxide reduction efficiency in the nitrogen oxide storage catalyst To reduce the amount of fuel injected through To provide a purifying system has its purpose.

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

The present invention relates to a catalytic converter having a nitrogen oxide storage catalyst, a nitrogen oxide sensor provided at a rear end of the catalytic converter, an injector for injecting fuel from an upstream side of the catalytic converter, and a control of injection of the injector by receiving a signal from the nitrogen oxide sensor. In the exhaust gas purification system of a diesel vehicle comprising an ECU for performing the,

A bypass pipe is installed in an upstream exhaust pipe of the catalytic converter, and a fuel cracking catalyst employing a hydrocarbon decomposition catalyst for decomposing paraffinic hydrocarbons having 12 or more carbon atoms into lower paraffins and olefins is installed in the bypass pipe. An injector subject to injection control of the gas is provided upstream of the hydrocarbon decomposition catalyst so that diesel oil and exhaust gas containing paraffins and olefins decomposed by the fuel decomposition catalyst flow in the catalytic converter.

Particularly, the hydrocarbon decomposition catalyst is mixed with colloidal silica, a binder selected from Fauzasite (FAU), beta (BEA) and mordenite (MOR), and wet milled to prepare a slurry, which is ceramic in a honeycomb structure. It is characterized by a zeolite catalyst coated on a carrier.

In addition, the hydrocarbon decomposition catalyst is made of a slurry of ruthenium (Ru), tungsten (W) and molybdenum (Mo) as an nitrate-type metal precursor in an activated alumina and then wet milling to prepare a slurry. And a metal oxide catalyst coated on a honeycomb ceramic carrier.

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

The present invention is to decompose a paraffinic hydrocarbon having 12 or more carbon atoms having poor reducing properties to lower paraffins and olefins having excellent reducing properties by using a hydrocarbon decomposition catalyst to further purify the efficiency of removing nitrogen oxides in the exhaust gas. System.

The purification rate at which the nitrogen oxide is removed through the reduction reaction in the catalyst is affected by the number and type of carbons of the individual hydrocarbons used as the reducing agent. In particular, the difference in the reactivity of the reducing agent is greater in the lean exhaust gas.

The higher paraffinic hydrocarbon having 12 or more carbon atoms contained in the exhaust gas introduced from the diesel engine has a poor reducing property, which is a factor in reducing the reduction ability and removal efficiency of nitrogen oxide in a conventional nitrogen oxide storage catalyst.

Therefore, in the present invention, these higher paraffinic hydrocarbons having 12 or more carbon atoms are first decomposed into lower hydrocarbons and olefins having relatively low carbon atoms using a hydrocarbon decomposition catalyst, and then reduced by a conventional catalyst for removing nitrogen oxides. By purifying the nitrogen oxide removal efficiency is to be further improved.

When described in more detail with reference to Figure 1 attached to the configuration of the present invention as follows.

1 is a schematic view showing an exhaust gas purification system of a diesel vehicle according to the present invention.

Reference numeral 16 denotes a conventional nitrogen oxide sensor installed at the rear end of the catalytic converter, and reference numeral 20 denotes an ECU in charge of injection control of the injector 22.

As shown in the drawing, a catalytic converter in which a nitrogen oxide sorbent catalyst 12 and a particulate matter filter 14 made of ceramic are arranged in series in the exhaust pipe 1 through which exhaust gas is discharged from an engine (not shown). 10 is installed.

Of course, the action of the nitrogen oxide storage catalyst 12 and the particulate matter filter 14 in this catalytic converter 10 is the same as in the prior art.

That is, in the case of the nitrogen oxide storing catalyst 12, the nitrogen oxide is occluded in the form of nitrate in an oxygen oxidizing atmosphere, and the nitrate occluded in the reducing atmosphere by fuel injection is purged with nitrogen and oxygen.

Next, in the purification system of the present invention, a bypass pipe 3 is provided in an upstream exhaust pipe 1 of the catalytic converter 10 that is already installed, and the hydrocarbon decomposition catalyst 32 is provided in the bypass pipe 3. ), A separate catalyst unit 30 is employed.
At this time, the bypass pipe 3 is always open as shown in the drawing, so the relative flow rate between the exhaust pipe 1 and the bypass pipe 3 is controlled by the diameters of the two pipes and the back pressure of the hydrocarbon decomposition catalyst. Can be.

Hereinafter, for the sake of clarity, the catalyst device 30 employing the hydrocarbon decomposition catalyst 32 will be referred to as a fuel decomposition catalyst device.

In addition, an injector 22 for fuel injection is provided upstream of the hydrocarbon decomposition catalyst 32 embedded in the fuel decomposition catalyst 30, and the injector 22 is controlled by the ECU 20 as in the prior art. It is intended to be sprayed under.

As a result, the fuel injected by the injector 22, ie, the diesel fuel, passes along with the exhaust gas through the hydrocarbon cracking catalyst 32 of the fuel cracking catalyst 30 further installed in the present invention through the upstream bypass pipe 3. do.

Thereafter, the fuel component subjected to the first reaction in the hydrocarbon decomposition catalyst 32 is introduced into the existing nitrogen oxide storage catalyst 12 through the downstream bypass pipe 3 together with the exhaust gas.

As described above, the hydrocarbon decomposition catalyst 32 decomposes a fuel component having poor reducing properties, and when passed through the fuel decomposition catalyst 30, a paraffinic diesel oil having a carbon number of 12 or more having poor reducing properties of nitrogen oxide has a reducing property. It is decomposed into excellent low-quality paraffins and olefins, so that the reduction reaction of nitrogen oxides easily occurs in the catalyst for removing nitrogen oxides 12 at the rear.

As described above, the purification system of the present invention installs a hydrocarbon decomposition catalyst 32 in the bypass pipe 3 to decompose light oil having a large molecular weight through the hydrocarbon decomposition catalyst 32, and the decomposed hydrocarbon removes nitrogen oxides. By acting as a reducing agent of nitrogen oxide in the catalyst 12, it is to improve the nitrogen oxide removal efficiency of the overall system.

In the purification system of the present invention, the catalyst 32 of the fuel cracking catalyst 30 is applied in consideration of the function of the acid catalyst reaction, which is a characteristic of the fuel cracking reaction of diesel fuel.

As a zeolite catalyst having excellent acid properties, a catalyst of Fauzasite (FAU), beta (BEA), or mordenite (MOR) is suitable in consideration of the size of the gas oil molecules.

In addition, the catalyst having a ruthenium (Ru), tungsten (W), or molybdenum (Mo) oxide catalyst on alumina has a weak acid point than that of zeolite but is suitable because of its excellent endothelial toxicity against sulfur.

Hereinafter, a process for preparing a catalyst applicable as a hydrocarbon decomposition catalyst in the purification system of the present invention will be described in detail.

First, as a first step, a slurry for hydrocarbon decomposition catalyst is prepared.

In the case of zeolite-based catalysts, one selected from Fauzasite (FAU), beta (BEA) and mordenite (MOR) is mixed with colloidal silica as a binder and wet milled to prepare a slurry.

In the case of the metal oxide catalyst, one of the oxide catalyst materials of ruthenium (Ru), tungsten (W) and molybdenum (Mo) is supported on the activated alumina as a metal precursor in the form of nitrate, and then wet milled to prepare a slurry. At this time, there is no additional binder.

Next, as a second step, the catalyst slurry prepared in the first step is coated on a carrier.

At this time, the ceramic carrier of the honeycomb structure is brought into contact with the liquid level of the catalyst slurry, and the slurry liquid is sucked up by applying negative pressure in the opposite direction.

Thereafter, as a third process, the carrier coated with the slurry is dried and calcined to complete the catalyst.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

Examples 1-6

As Example 1, according to the above-described manufacturing process was prepared a catalyst carrying the Faujasite (FAU), the coating amount of the slurry was 30% based on the total dry weight.

As Example 2, a mordenite (MOR) supported catalyst was prepared in the same manner as in Example 1.

As Example 3, a beta (BEA) supported catalyst was prepared in the same manner as in Example 1.

As Example 4, a ruthenium (Ru) / alumina catalyst was prepared according to the above-described manufacturing process, wherein the coating amount of the slurry was 20% based on the dry weight, and the loading amount of ruthenium was 3% by weight.

As Example 5, a tungsten (W) / alumina catalyst was prepared in the same manner as in Example 4.

Example 6 prepared a molybdenum (Mo) / alumina catalyst in the same manner as in Example 4.

Comparative Examples 1 to 7

As Comparative Examples 1 to 3, catalysts carrying Linda A (LTA), GS 5 (MFI), and GS 11 (MEL) were prepared in the same manner as in Example 1.

As Comparative Examples 3 to 7, iron (Fe), cobalt (Co), copper (Cu), and zinc (Zn) catalysts were prepared in the same manner as in Example 4.

Test Examples 1 to 3

On the other hand, as Test Example 1, it was examined whether the hydrocarbon decomposition reaction proceeded while injecting light oil and air as reactants to the catalysts equipped with the catalysts of Examples and Comparative Examples.

As the reactant composition, the ratio of diesel oil and air was 1: 5 by weight, the temperature of the inlet was maintained at 300 ° C, and the catalyst was operated under adiabatic conditions.

In addition, the space velocity (inverse time of contact time) was 50000 hr ^-1 .

Under these conditions, the produced gas from the catalyst was analyzed by mass spectrometry and the average carbon number was calculated to observe the progress of decomposition reaction.

As Test Example 2, the catalyst was exposed to a diesel engine exhaust gas containing 100 ppm SO ₂ for 100 hours, and then the same evaluation as in Test Example 1 was performed.

As Test Example 3, vehicle evaluation was performed in comparison with the non-attachment with the hydrocarbon decomposition catalysts of Examples 1, 4, and 6, where the European mode was applied.

Each result of the reaction test for each catalyst made as described above is shown in Table 1 below.

Looking at the measurement results, as can be seen in Table 1, the activity of the decomposition reaction in the catalyst of the Example was superior to the catalyst of the comparative example, when carrying out a comprehensive review of the durability against sulfur carried out carrying ruthenium (Ru) It was confirmed that the catalyst of Example 4 was the best.

As described above, in the exhaust gas purification system of the diesel vehicle according to the present invention, a separate bypass pipe is provided in the upstream exhaust pipe of the catalytic converter in which the nitrogen oxide storage catalyst and the ceramic particulate filter are arranged in series. In this bypass pipe, a paraffin and olefin decomposed by installing a fuel decomposition catalyst employing a hydrocarbon decomposition catalyst that decomposes a paraffinic diesel oil having 12 or more carbon atoms having poor reduction characteristics of nitrogen oxides into lower paraffins and olefins having excellent reduction characteristics. This catalytic converter flows, and an injector for fuel injection is provided upstream of the hydrocarbon decomposition catalyst.

In the exhaust gas purification system of the present invention, the low carbon number paraffin and olefin having excellent reducing ability of nitrogen oxide act as a reducing agent of nitrogen oxide in the nitrogen oxide storage catalyst of the catalytic converter, so that the removal efficiency of nitrogen oxide can be improved. As the nitrogen oxide reduction efficiency increases in the nitrogen oxide storage catalyst, the amount of fuel injected through the injector may be reduced.

Claims (3)

delete A catalytic converter having a nitrogen oxide storage catalyst, a nitrogen oxide sensor installed at a rear end of the catalytic converter, an injector for injecting fuel from an upstream side of the catalytic converter, and an ECU for controlling injection of the injector by receiving a signal from the nitrogen oxide sensor. It includes, but the bypass pipe is installed in the upstream exhaust pipe of the catalytic converter, the bypass pipe is installed a fuel cracking catalyst employing a hydrocarbon decomposition catalyst for decomposing paraffinic hydrocarbons having 12 or more carbon atoms into lower paraffins and olefins And an injector under injection control of the ECU upstream of the hydrocarbon cracking catalyst so that diesel oil and exhaust gas containing paraffins and olefins decomposed by the fuel cracking catalyst flow into the catalytic converter. In the gas purification system, The hydrocarbon decomposition catalyst is wet milled by mixing colloidal silica, a binder selected from Fauzasite (FAU), beta (BEA) and mordenite (MOR), and then prepared as a slurry and coated on a honeycomb ceramic carrier. An exhaust gas purification system for a diesel vehicle, characterized in that the zeolite catalyst. A catalytic converter having a nitrogen oxide storage catalyst, a nitrogen oxide sensor installed at a rear end of the catalytic converter, an injector for injecting fuel from an upstream side of the catalytic converter, and an ECU for controlling injection of the injector by receiving a signal from the nitrogen oxide sensor. It includes, but the bypass pipe is installed in the upstream exhaust pipe of the catalytic converter, the bypass pipe is installed a fuel cracking catalyst employing a hydrocarbon decomposition catalyst for decomposing paraffinic hydrocarbons having 12 or more carbon atoms into lower paraffins and olefins And an injector under injection control of the ECU upstream of the hydrocarbon cracking catalyst so that diesel oil and exhaust gas containing paraffins and olefins decomposed by the fuel cracking catalyst flow into the catalytic converter. In the gas purification system, The hydrocarbon decomposition catalyst is a slurry of ruthenium (Ru), tungsten (W) and molybdenum (Mo) as a metal precursor in the form of nitrate, supported on activated alumina and then wet milled to prepare a slurry. An exhaust gas purification system for a diesel vehicle, characterized by a metal oxide catalyst coated on a honeycomb ceramic carrier.

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