KR100300179B1 - catalyst system reducing NOx for gasoline GDI/lean burn engine - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an apparatus for reducing exhaust gas, and particularly for gasoline lean burn engines and direct injection engines, regenerative catalysts and NOx removal can be effectively removed. Regeneration of catalysts is characterized by the combination of thin-wall carriers, including conventional carriers, such as electrically heated catalysts (EHCs) and close coupled catalysts (CCCs). Alternatively, the present invention provides a catalyst system that can effectively reduce NOx and improve durability by using an electrically heated catalyst or optimization of a cloth coupled catalyst for desulfurization.

Description

Catayst system reducing NOx for gasoline GDI / lean burn engine

The present invention relates to an exhaust gas reduction device for a gasoline direct injection engine and a lean burn engine, and in particular, the present invention relates to an electrically heated catalyst and a nitrogen oxide in order to reduce NOx in exhaust gases harmful to a human body. It relates to a structure device provided with a storage type catalyst and a three-way catalyst.

At present, the environmental pollution caused by exhaust gas of automobiles, which is rapidly increasing in demand, is getting serious. The major harmful components in automobile exhaust gases are hydrocarbons, carbon monoxide and nitrogen oxides, most of which are generated in automobiles. In particular, a large amount of nitrogen oxides (NOx) are generated in diesel cars, and in recent years, as gas engines and lean burn gasoline cars are introduced, the reduction of nitrogen oxides generated is becoming more difficult. Is emerging.

Reducing nitrogen oxides in automobile exhaust gas is largely classified into fuel improvement, engine improvement, and exhaust gas treatment. In the case of the dual exhaust gas treatment method, it is most effective to use a catalyst, the present invention relates to this.

Currently, a ternary catalyst is most typically used as a catalyst mounted on a gasoline vehicle to purify automobile exhaust gas, in which γ-aluvina coated on honeycomb is loaded with platinum, palladium, rhodium and the like.

These three-way catalysts exhibit high purification rates for hydrocarbons, carbon monoxide, and nitrogen oxides, which are hazardous three-element gases, in an ideal state with an air-fuel ratio (air / fuel ratio) of 14.7. However, such a catalyst has a problem that it cannot be used in the region where the air-fuel ratio is over 14.7, that is, in the lean combustion region using relatively excess air, since the purification ability for nitrogen oxide is lost. In particular, in recent years, the lean burn operation range has been expanded, and the need for a catalyst capable of purifying nitrogen oxides has increased as a lean burn engine having a large displacement of 1800 cc or more appears.

The nitrogen oxide (NOx) reduction catalyst system used in the conventional gasoline direct injection engine or lean burn engine vehicle shown in FIG. 1 can be classified into two types: a selective cyclic catalyst system and a nitrogen oxide storage catalyst system.

In general, as the vehicle exhaust gas, which is one of the sources of air pollution, has become a social problem causing people's health problems such as headache and dizziness, recent researches have been actively conducted.

There are various methods of purifying vehicle exhaust gas, such as recombustion of a part of the exhaust gas, and a method of reacting with a catalyst. The exhaust system of a vehicle uses a chemical reaction through a catalyst to oxidize exhaust gas and The method of inducing a reduction action is mainly applied.

Catalytic converters in automobiles play a role in purifying harmful components such as CO ₂ , H ₂ O, N ₂ and O _{2 from} CO, HC, and NOx contained in exhaust gas.

The nitrogen oxide (NOx) storage type catalyst system uses a catalyst having a characteristic of occluding nitrogen oxides (NOx). The catalytic activity is rapidly reduced by sulfur (S) by easily adsorbing sulfur oxides together with nitrogen oxides. Therefore, there is a problem in that a desulfurization condition for removing nitrogen oxide regeneration and sulfur (S) in a nitrogen oxide storage catalyst system has to be applied to an engine management system.

Accordingly, the present invention has been made to solve the problems of the conventional nitrogen oxide (NOx) storage catalyst structure in the vehicle, the object of the exhaust gas of the high-performance gasoline direct injection engine and lean combustion engine In addition, the present invention provides a vehicle exhaust gas purification device for removing NOx.

1 is a block diagram of a conventional nitrogen oxide (NOx) reduction catalyst system

2 is a block diagram of a nitrogen oxide (NOx) reduction catalyst system according to the present invention

3 is a block diagram of a nitrogen oxide (NOx) reduction catalyst system according to a first embodiment of the present invention

4 is a block diagram of a nitrogen oxide (NOx) reduction catalyst system according to a second embodiment of the present invention

5 is a block diagram of an electric heated catalyst of the present invention.

6 is a control flow diagram of the electrical heated catalyst of the present invention.

Explanation of symbols on the main parts of the drawings

1, 10, 10 ', 10': nitrogen oxide sorbent catalyst 2, 20, 20 ', 20': three-way catalyst

30: electric heating catalyst 4, 40: engine

50: electronic control device 6, 60: surge tank

70: temperature sensor

Accordingly, the present invention provides a closed coupled catalyst composed of an electrically heated catalyst system and a nitrogen oxide (NOx) sorbent catalyst for facilitating desulfurization of a catalyst in a combustion operation of an automobile engine in a gasoline lean burn engine. Existing carriers or thin wall carriers are used. The underfloor catalystic converter system is a high loading of precious metals including rhodium (Rh) using conventional carriers or thin wall carriers. In the closed-coupled catalyst structure without an electric heating catalyst, nitrogen oxides (NOx) are formed to form conditions such as rapid idling so that the gas temperature rises above 650 ° C. in a rich air-fuel ratio section after a certain time. ) We propose a reduction device and method.

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

2 is a view illustrating an exhaust gas purifying apparatus according to the present invention, wherein an electrically heated catalyst which is operated in comparison with a predetermined reference value in an electronic controller in order to increase the exhaust gas temperature in a state where the air-fuel ratio is rich is a predetermined time during operation. Works every time. The nitrogen oxide sorbent catalyst is configured as a support carrier or a thin wall carrier. The three-way catalyst, an underflow catalyst system, is highly loaded with precious metals including rhodium (Rh) using a thin-walled carrier, and oxidizes carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust with air to form carbon dioxide (CO ₂ ). It is made of water (H ₂ O) and nitrogen oxide (NOx) is a device that serves to purify the exhaust gas emitted from the engine room by inducing a reaction to reduce the nitrogen (N ₂ ) and oxygen (O ₂ ). Therefore, according to the nitrogen oxide reduction method of the present invention, it is determined in step S10 whether the air-fuel ratio (air / fuel ratio) of the engine is rich and whether the exhaust gas temperature is 650 ° C. or less, and in step S20 The nitrogen oxides (NOx) are reduced by allowing the electrically heated catalyst to be operated at regular intervals under heavy rain and exhaust gas temperature of 650 ° C. or lower.

3 shows an exhaust purification apparatus according to another embodiment, in which a thin-walled carrier does not use an electrically heated catalyst. The cloth coupled catalyst has two catalysts having a volume ratio of about 8: 2. Rh at Pt / Rh, Pd / Rh, Pt / Pd / Rh for fast light-off of more than 50% of NOx absorbing catalyst in the first brick and 2nd brick It is a high-loaded three-way catalyst with a high ratio. Therefore, it is for efficient nitrogen oxide (NOx) reforming and desulfurization.

The underflow catalyst system is a structure in which a three-way catalyst having a high loading of Pt / Rh, Pd / Rh, and Pt / Pd / Rh system using an existing carrier or a thin-walled carrier is located close to the cloth coupled catalyst. to be.

FIG. 4 illustrates an exhaust purification apparatus according to another embodiment, in which a cloth-coupled catalyst has two catalysts, and a conventional carrier or thin wall of the first brick and the second brick. It is composed of nitrogen oxide (NOx) absorbing catalyst using a carrier, and the regeneration requires a temperature higher than 650 ℃ in the rich state. Therefore, it is difficult to make this temperature condition in general gasoline direct injection engine or lean burn engine. Constitutes a nitrogen oxide (NOx) absorbing catalyst at the close coupled catalyst position where It naturally consists of two bricks to maximize regeneration or efficiency.

The underflow catalyst system is placed close to the close coupled catalyst by high loading with Pt / Rh, Pd / Rh, Pt / Pd / Rh based catalysts containing Rh using existing carriers or thin-wall carriers.

Therefore, in order to efficiently reform nitrogen oxide and desulfurization, it is not necessary to develop an advanced engine management system and maximize the efficiency of nitrogen oxide removal.

The present invention operated as described above is composed of a nitrogen oxide containing a conventional electrically heated catalyst consisting of a high loading three-way catalyst using an occlusion type catalyst and an existing carrier or a thin film carrier, and the natural desulfurization effect excluding the electrically heated carrier. Maximized catalyst system has the advantage of effectively reducing nitrogen oxides.

While the invention has been shown and described with respect to particular embodiments, those skilled in the art will recognize that various modifications and changes can be made without departing from the spirit and scope of the invention as indicated by the appended claims. Anyone can easily know.

Claims (4)

In a gasoline direct injection or lean burn engine, an nitrogen oxide using an electric carrier or an existing carrier or a thin-wall carrier and an electric heating catalyst 30 equipped with a temperature sensor 70 for operating in an automobile engine 40 in a rich air-fuel ratio Nitrogen oxide, characterized in that it consists of an underflow catalyst system consisting of a three-way catalyst 20 loaded with a noble metal containing rhodium (Rh) using a clogged catalyst composed of the occluded catalyst 10 and an existing carrier or a thin-wall carrier. (NOx) reduction catalyst device. In the gasoline direct injection engine, a three-way catalyst 20 ', which is a conventional carrier or a thin-wall carrier loaded with a nitrogen oxide occlusion catalyst 10' and a high Rh in a second brick in an automobile engine 40, is used. A nitrogen oxide reduction catalyst device comprising an underflow catalyst system using a cloth-coupled catalyst used and a Pt / Rh, Pd / Rh, Pt / Pd / Rh-based high loaded three-way catalyst (20 '). In the gasoline direct injection engine, a closed-coupled catalyst, which is a nitrogen oxide-occluded catalyst 10 'of the first brick and the second brick, and Pt / Rh, Pd / Rh, and Pt / Pd / Rh systems in the automotive engine 40 Nitrogen oxide reduction catalyst device characterized in that consisting of an underflow catalyst system using a high-loaded three-way catalyst (20 '). Determining whether the exhaust gas temperature is less than 650 ℃ in a rich air-fuel ratio (S10), and if the air-fuel ratio is rich and the exhaust gas temperature is less than 650 ℃ characterized in that it comprises a step (S20) to operate the electric heating catalyst. Nitrogen oxide (NOx) reduction method.