KR20060014706A - A 3way catalyst converter and its using exhaust gas remove method - Google Patents

Abstract

The present invention relates to a three-way catalytic converter for reducing the exhaust gas through the primary reduction process and the secondary oxidation process through the three-way catalytic converter for automobile exhaust gas and the exhaust gas removal method using the same.

The present invention provides a reduction treatment catalyst which passes through a metal network electroplated with rhodium on a ferrochrome (Fe-Cr) network, and then passes through a carrier having a honeycomb structure as a catalyst for reducing natural zeolite, and palladium in a ferrochrome network. After passing through the electroplated metal network through the oxidation treatment catalyst passes through the carrier of the honeycomb structure with the zeolite for oxidation it can significantly reduce the exhaust gas of the vehicle.

Automobile, Exhaust Gas, Three-way Catalyst, Reduction, Oxidation, Hazardous Substances, Electroplating

Description

Three-way catalytic converter and its using exhaust gas remove method

1 is a view schematically showing the configuration of an exhaust system of a vehicle

Figure 2 is a cross-sectional view showing the configuration of the present invention three-way catalytic converter

<Explanation of symbols for main parts of drawing>

30: Three-way catalyst converter 31: Rhodium plating network

32: reduction catalyst 33, 36: zeolite catalyst carrier

34: palladium plating network 35: oxidation catalyst

The present invention relates to a three-way catalytic converter for reducing the exhaust gas through the primary reduction process and the secondary oxidation process through the three-way catalytic converter for automobile exhaust gas and the exhaust gas removal method using the same.

Generally in automobiles, more than 95% is a gaseous substance that is burned as a gas discharged through the exhaust pipe, and most of the fossil fuels we use today are a mixture of several types of HC. Must combine with oxygen to produce only water vapor and carbon dioxide.

However, at the present technical level, even if the engine is operating at optimum combustion, the exhaust gas cannot be completely burned, so the exhaust gas has no choice but to contain harmful substances.

When the gasoline engine is operated at a heavy load among these harmful substances, most of the exhaust gases are nitrogen (71%), carbon dioxide (18.1%), water vapor (9.2%), and the harmful substances are about 1% of the total exhaust gas. The harmful substances included here are mainly carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx).

In order to reduce the exhaust gas of vehicles, an oxidation catalyst that reduces CO and HC by an oxidation reaction was initially used, but a three-way catalyst that reduces 80% or more simultaneously to NOx is used.

The three-way catalyst is an exhaust gas treatment device for purifying harmful gas components in the combustion gas emitted from an engine of a car. In the case of a gasoline engine, a three-way catalyst uses a three-way catalyst that simultaneously purifies hydrocarbons, carbon monoxide and nitrogen oxides. The oxidation catalyst is mainly used to purify particulate matter.

Hereinafter, the three-way catalyst device will be described.

First, the catalyst is composed of a substrate in a metal can, a wash-coat on the carrier, and a thin layer of catalyst material applied on the intermediate layer.

Examples of the carrier include a pellet type, a ceramic honeycomb type, a metal wire, and the like.

First, in the bead-shaped carrier, thousands of small beads made of ceramic are taken into a metal can and placed in a metal can to allow the exhaust gas to pass through them, and the exhaust gas pressure is much higher than that of the honeycomb type and is rarely used. .

Secondly, in the ceramic honeycomb type, the main material of the ceramic carrier is magnesium-aluminum silicate (2MgO 2Al ₂ O ₃ 5SIO ₂ ), which has high heat resistance, and this type allows exhaust gas to pass through thousands of honeycomb passages. .

Because ceramic carriers are susceptible to vibration and shock, pads are wrapped between elastic cans such as metal wool between cans and carriers, which compensate for expansion coefficient differences between carriers and cans while driving. It is the most used form today.

Third, in the metallic wire substrate, the metallic carrier is made by winding a strip of cylindrical or woven mesh with a thin heat-resistant, corrosion-resistant iron wire of about 0.5 mm to 1 mm, and a catalytic material on the surface thereof. Since the exhaust gas passes through it by applying a, the time to reach the operating temperature is significantly shortened compared to the ceramic carrier, as well as the risk of melting because of the high thermal conductivity.

Metallic carriers have advantages such as reduced back pressure, increased surface area per unit volume, higher thermal conductivity, and lower specific heat, but they are expensive, risk of high temperature corrosion (from about 1100 ° C), and low when repeating stop start. There are disadvantages such as the easy cooling of the catalyst due to the specific heat.

On the other hand, bead and metal carriers apply the catalyst material directly to the surface, but in the ceramic integrated type, a porous intermediate layer is formed in thousands of small passages through the carrier to obtain a table that increases the effective surface area of the catalyst by about 7000 times. A thin layer of platinum (Pt) and rhodium (Rh), or paradium (Pd) and rhodium (Rh) is used as the actual catalyst layer on the surface of the intermediate layer.

The air-fuel ratio control method using a catalytic converter is known so far as the most effective method for purifying exhaust gas of a gasoline engine.

In other words, there are no post-treatment systems with better current purification than this method. Hazardous substances in the exhaust gas, in particular nitrogen oxides (NOx), hydrocarbons (HC), carbon monoxide (CO), etc. can be further reduced by using a catalyst, and such catalytic devices include an oxidation catalyst device and a reduction catalyst. Reduction catalyitic converters or three-way catalytic converters are effective.

The three-way catalytic system purges 90% or more of harmful substances such as carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) when operating in a narrow area (<1%) near the theoretical air excess (λ = 1). can do.

However, it is difficult to maintain the air-fuel ratio in a narrow area around λ = 1 under all the engine operating conditions, so the air-fuel ratio is controlled with a control width. This narrow control area is called an air-fuel ratio window or a Lambda window.

In order to maintain the air-fuel ratio near λ = 1, the oxygen concentration in the exhaust gas must be measured and the fuel injection amount must be corrected each time based on this measured value.

An air-fuel ratio sensor (λ-sensor) is used to measure the oxygen concentration in the exhaust gas, and the air-fuel ratio sensor is also called an oxygen sensor (O ₂ -sensor), which has an air-fuel ratio based on the air-fuel ratio λ = 1. The output voltage signal changes rapidly when it is high or low.

Control of the air-fuel ratio is also important, but the operating temperature of the catalyst plays an important role.

The operating temperature that can extend the catalyst life while maintaining the high catalytic action rate is in the range of about 400 ~ 800 ℃, in which the thermal life of the catalyst is longer due to less thermal aging due to temperature changes 800 In the range of ˜1000 ° C., thermal aging is increased to melt the catalyst layer and the aluminum oxide layer of the support, thereby greatly reducing the effective surface area capable of catalysis.

In particular, the longer the period of operation in this temperature range, the greater the impact, and at 1000 ° C. or more, the thermal aging phenomenon is severe and the function of the catalyst is lost, so the attachment position of the catalyst is important.

The location of the catalyst should be such that the catalyst is not heated above the critical temperature (about 950 ° C) under any engine operating conditions. Under ideal operating conditions, the catalyst varies depending on the warranty period. Can be.

When a fire occurs in the engine, the catalyst temperature can be raised to about 1400 ° C. or more instantaneously. At this temperature, the carrier layer of the catalyst melts and the catalyst is completely destroyed.

And even if the engine is accelerated under no load, it can cause the same phenomenon as misfire, so you should refrain from accelerating the engine with no load.

The vehicle must be operated for a certain period of time with no load at medium speed to allow the unburned HC contained in the catalyst to react slowly and to exit the catalyst.

In addition, even when engine lubricating oil flows into the combustion chamber, sediment by lubricating oil blocks the pores of the catalyst's porous layer, thereby degrading the function of the catalyst. When the temperature of the exhaust gas rises, combustion occurs in the catalyst, causing melting.

Conventionally, three-way catalysts are used to treat pollutants (CO, NOx, CxHy) emitted from vehicles using gasoline engines, but diesel or lean burn engines have high oxygen concentrations in the exhaust gas. There is a limit in oxidizing CO and CxHy, and there is a difficulty in reducing nitrogen oxides.

Selective Catalytic Reduction (SCR) or Urea (urea) using ammonia may be used to treat emissions from vehicles using diesel engines. Temperature is required.

In addition, there is a problem that the exhaust gas residence time inside the exhaust system is too short to effectively convert NO to NO2.

The present invention is to solve the problems of the three-way catalyst of the conventional vehicle as described above, an object of the present invention, through the three-way catalytic converter to reduce the exhaust gas while undergoing a primary reduction process and a secondary oxidation process. It is to provide a three-way catalytic converter and a method for removing exhaust gas using the same.

In order to achieve the above object, the three-way catalytic converter of the present invention includes a rhodium network made of ferrochrome, a reduction catalyst, and a zeolite catalyst carrier, which are sequentially formed at the front end, and at the rear end, a palladium plating is carried out at a predetermined distance from the zeolite catalyst carrier. And an oxidation catalyst consisting of a platinum, a sponge-plated sponge which burns an ammonium chloroplatinate solution, and a zeolite catalyst carrier are formed in this order.

In addition, the exhaust gas removal method using the three-way catalytic converter of the present invention, the reduction treatment catalyst passing through the carrier of the honeycomb structure with a natural zeolite for reduction after passing through a metal network electroplated with rhodium to the ferrochrome network And an oxidation treatment catalyst which passes through a metal network electroplated with palladium to ferrochrome network and then through a carrier of a honeycomb structure with zeolite for oxidation.

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

1 is a schematic diagram of the present invention, in which a three-way catalytic converter 30, a sub muffler 40, and a main muffler 50 are sequentially installed between a connector 10 connected to an exhaust manifold and a final discharge port 20. It is configured.

FIG. 2 is a detailed view of the three-way catalytic converter 30, in which a rhodium plating network 31 made of ferrochrome, a reducing catalyst 32, and a zeolite catalyst carrier 33 are sequentially installed at the front end, and the zeolite at the rear end thereof. A palladium plating network 34, a platinum sponge surface oxidation catalyst 35 in which an ammonium platinum chloride solution is combusted at a predetermined distance from the catalyst carrier 33, and a zeolite catalyst carrier 36 are provided in this order.

1m/m ×1m/m이다.The rhodium network 31 is made of electroplating, the net material is using Fe + Cr, the specification is 0.35

1 m / m x 1 m / m.

The reduction catalyst 32 is made of platinum black, it is possible to use semi-permanent by producing platinum black after burning 5% metallic platinum in activated carbon as a powder.

Since the zeolite catalyst carrier 33 has a surface area 2-3 times larger than a conventional product made of alumina, the zeolite catalyst carrier 33 may increase the intake and flow time of the exhaust gas.

1m/m ×1m/m이다.The palladium plating network 34 is made of Fe + Cr, the specification is 0.35

1 m / m x 1 m / m.

The oxidation catalyst 35 is composed of platinum sponges to combust ammonium chloroplatinate solution, and has a large porosity and a semipermanent oxidation catalyst.

Referring to the operation of the present invention configured as described above is as follows.

In the present invention, the harmful substances discharged from the gasoline engine are introduced into the three-way catalytic converter 30 through the connector 10. First, the rhodium-plated rhodium plating network 31 is passed through the ferrochrome (Fe-Cr) network. Done.

Hazardous substances passed through the rhodium plating network 31 passes through a reduction treatment catalyst while passing through a zeolite catalyst carrier 33 having a honeycomb structure as a zeolite catalyst through a reduction catalyst 32.

Next, the harmful substances that have undergone the reduction treatment catalyst pass through the palladium plating network 34 electroplated with palladium on the ferrochrome network.

Then, the oxidation catalyst 35 and the zeolite catalyst carrier 36 having a honeycomb structure as a zeolite are passed through the oxidation treatment catalyst.

Therefore, the present invention is to reduce the carbonization component of the exhaust gas and to extend the function and life of the metal catalyst by subjecting the harmful substances discharged from the gasoline engine first through the reduction treatment process, and then subjected to the oxidation treatment process.

Here, the metal network of ferrochrome is applied to this manufacturing method because the thermal conductivity is good and the white metal material used as a catalyst is useful as a catalyst at low temperature and low pressure and is an optimal material as an active catalyst.

In addition, the platinum sponge (platinum sponge surface) treated with ammonium chloroplatinum has an optimum condition and utility as an oxidation catalyst 35, and its porosity is large, the flow of exhaust gas is free, and the amount of gas intake is large.

It is a material that burns platinum or activated carbon and platinum. It is a reduction catalyst material, which can increase its utility and efficiency.

In addition, the zeolite is used as the catalyst carriers 33 and 36 because the surface area and the porosity of the alumina have 2-3 times the surface area and pores compared to the existing alumina, which can increase the flow time of the exhaust gas and its suction amount.

The present invention as described in detail above has an effect that can significantly reduce the vehicle exhaust gas through the primary reduction process and the secondary oxidation process through the three-way catalytic converter.

Claims (2)

In the vehicle three-way catalytic converter, In front of the catalytic converter, a rhodium plating network 31 in which a network material is made of ferrochrome and plated with rhodium, a platinum black reduction catalyst 32, and a zeolite catalyst carrier 33 are sequentially formed, At the rear end of the catalytic converter, a palladium plating network 34 made of ferrochrome at a predetermined distance from the zeolite catalyst carrier 33, an oxidation catalyst 35 made of platinum sponge surface obtained by burning an ammonium platinum chloride solution, and a zeolite catalyst Three-way catalytic converter, characterized in that the carrier 36 is formed in turn. A reduction treatment catalyst process of passing through a metal network electroplated with rhodium through a ferrochrome network and then through a carrier of a honeycomb structure with a natural zeolite for reduction; A method of removing exhaust gas using a three-way catalytic converter, characterized in that it consists of an oxidation treatment catalyst which passes through a metal network electroplated with palladium on a ferrochrome network, and then passes through a carrier having a honeycomb structure as a catalyst for oxidation zeolite.

Images