KR100980925B1 - Catalyst and method of it for purifying exhaust gases considering flow pattern - Google Patents

Abstract

The present invention is formed by partitioning the high concentration coating area and the low concentration coating area at the front end of the catalyst by using the coating liquid suction amount adjusting device, the coating amount of the catalyst front end portion increases toward the center direction, the flow rate of the reaction gas flowing into the catalyst and the catalyst It is an object of the present invention to provide a catalyst for purifying exhaust gas and a method for preparing the same, which can improve catalyst activation and catalyst performance at an early stage by optimizing the effect of mass transfer in each channel.

To this end, the present invention comprises a first coating region coated with a high concentration such that the catalyst is activated at the initial start-up to the noble metal at the front end of the catalyst; And

A second coating region formed in a rearward direction of the first coating region and coated at a relatively lower concentration than the first coating region, wherein the first and second coating regions each have a different concentration of coating liquid inside the catalyst. The channel is sucked through the inhaler, and the coating length of the first coating region provides a catalyst for purifying exhaust gas, characterized in that the structure is made longer toward the center of the catalyst.

Exhaust gases, catalysts, mass transfer, coatings, precious metals

Description

Catalyst and method for preparing the exhaust gas purification in consideration of the flow pattern {pattern and method of it for purifying exhaust gases considering flow pattern}

The present invention relates to a catalyst for purifying exhaust gases and a method for preparing the same, which minimizes the use of precious metals of the catalyst and maximizes the catalyst's purification efficiency by applying a coating method considering mass transfer and flow of the reaction gas. .

Recently, as the use of automobiles increases and the traffic volume increases, the problem of air pollution due to exhaust gas has emerged as a serious social problem.

Therefore, governments in each country have set emission standards for pollutants in exhaust gases such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx). It is becoming a trend.

In particular, in recent years, there is an increasing demand for strict regulations on exhaust gas emitted at the start of startup. It is known that 60% of the exhaust gas is emitted at the start of the engine.

Conventionally, catalysts coated with precious metals such as platinum (Pt), palladium (Pd) and rhodium (Rh) have been used to remove harmful substances from the exhaust of automobiles. These catalysts are mounted in an exhaust system to decompose hydrocarbons, promote oxidation of carbon monoxide and reduction of nitrogen oxides, thereby removing harmful components from the exhaust gases and purifying the exhaust gases.

For this purpose, as a known exhaust gas purification catalyst, a homogeneous coating catalyst in which a noble metal is uniformly coated on a carrier is known.

However, in the case of the known homogeneous coating catalyst, since the engine is not warmed up sufficiently and the temperature of the exhaust gas is low, it takes a relatively long time to reach the LOT (Light Off Temperature), so that the exhaust gas at the beginning of engine start-up There is a problem that is not efficient for purification.

Therefore, there is a need for a catalyst that can be warmed up and activated quickly at the start of startup.

On the other hand, Figure 14 is a view showing a form in which the exhaust manifold and the catalytic converter is connected in the vehicle, the exhaust manifold 100 serves as a passage of the exhaust gas discharged from each cylinder of the engine, generally four cylinders Gathered together and passed through a catalytic converter.

15 (a) to 15 (d) show the flow amount of the exhaust gas passing through parts a to d of FIG. 14, respectively, and the flow amount of the exhaust gas passing through the catalytic converter differs depending on the shape of the exhaust manifold. In general, the further away from the center, the lower the amount of exhaust gas flow.

However, since the noble metal is uniformly coated without considering the exhaust gas flow amount, the known homogeneous coating catalyst may result in the noble metal being used more than necessary in the portion where the flow amount of the exhaust gas is small.

In addition, since the precious metal is an expensive material having a very small output, the known homogeneous coating catalyst has a problem in that the use of the precious metal is high and the cost is increased.

Accordingly, there is a need for a method of reducing the cost of the exhaust purification catalyst while reducing the use of precious metals so that valuable resources can be utilized effectively.

On the other hand, the method of coating a high concentration of precious metals in the front end of the catalyst is referred to as 'zone coating method'. 6 is a process chart showing a manufacturing process of the zone coating method.

First, a coating liquid container containing a low concentration of coating solution is provided so that the lower end of the uncoated catalyst (carrier 1) can be contacted. Subsequently, the suction pressure is provided by using an inhaler, whereby a coating solution of low concentration moves up through the channel inside the catalyst 14.

At this time, the catalyst 14 is coated with a low concentration coating solution by a predetermined length to form a low concentration coating region.

Then, the catalyst 14 is rotated in the vertical direction to provide a coating liquid container containing a high concentration of the coating solution, so that the lower end of the catalyst 14 can be contacted. Subsequently, if the suction pressure is provided by using the inhaler, the coating solution is concentrated while the coating solution of high concentration moves upward through the channel inside the catalyst 14, thereby completing the catalyst for purification of exhaust gas 14.

When a large amount of precious metal is coated on the front end portion of the catalyst 14 produced by the zone coating method, it is possible to reduce the warm-up or heat-up time of the initial catalyst 14. When the exhaust gas flows toward the catalyst 14, heat is transferred to the front end where the exhaust gas flow meets the catalyst 14 for the first time, and the catalyst 14 is relatively coated because the precious metal is coated at a high concentration. Oxidation reaction of exhaust gas by (14) occurs quickly.

Since an exothermic reaction occurs when an oxidation reaction occurs, this exothermic reaction causes the catalyst 14 to warm up relatively quickly. Since the warmed-up catalyst 14 and exhaust gas are also quickly warmed up to the low concentration coating region 11 located rearward, the exhaust gas purification catalyst 14 quickly reaches the harmful component removal temperature LOT.

Since heat transfer in the catalyst 14 is more rapid in heat transfer by convection than heat transfer by conduction, heat transfer by convection is easily caused by setting the front end portion of the catalyst 14 as a high concentration coating area (coating liquid).

Here, increasing the coating amount of the noble metal at the front end of the catalyst 14, that is, coating a high concentration of the noble metal has other important meanings besides improving the purification performance through early warm-up.

It is to increase the mass transfer of the exhaust gas (reaction gas). In the conventional zone coating method, the entire diameter cross section is the same at the front end of the catalyst 14, and the coating length of the high concentration coating liquid is constant.

However, when the exhaust gas passes through the catalyst having the same diameter cross-section and coating length at a high concentration, the mass transfer is faster at the center of the catalyst, while the farther it is from the center, the slower the flow becomes due to the resistance of the outermost part. The amount of reactant gas also decreases toward the outermost portion.

Therefore, in order to increase the purification efficiency of the catalyst, it is necessary to increase the coating amount at the center of the catalyst and to increase the coating length.

The present invention has been made in view of the above, by using a coating liquid suction amount control device formed by partitioning the high-concentration coating area and low-concentration coating area in the front end of the catalyst, by increasing the coating amount of the catalyst front end toward the center direction It is an object of the present invention to provide a catalyst for purifying exhaust gas and a method for producing the same, which can improve catalyst activation and catalyst performance early by optimizing the flow rate of reactant gas flowing into the catalyst and the effect of mass transfer in each channel of the catalyst. .

In the present invention for achieving the above object, in the catalyst for purifying exhaust gas,

A first coating region coated at a high concentration such that a noble metal is rapidly activated at initial start-up at the front end of the catalyst; And

A second coating region formed in a rearward direction of the first coating region and coated at a relatively lower concentration than the first coating region, wherein the first and second coating regions each have a different concentration of coating liquid inside the catalyst. It is made to be sucked through each channel of the inhaler, the coating length of the first coating region is characterized in that it is made of a structure that becomes longer toward the center of the catalyst.

In a preferred embodiment, the first and second coating areas are coated with a different concentration of coating liquid through the intake volume control device having a different cell size and coated on each channel inside the catalyst, and the intake control device is used for high concentration coating. The first coating liquid suction amount adjusting device having a structure in which the size of the cell increases toward the center, and the second coating liquid suction amount adjusting device having the structure in which the size of the cell decreases in the center for the low concentration coating.

In a more preferred embodiment, the first coating region is characterized in that 10 to 50% of the total volume of the catalyst.

Another aspect of the present invention is a method for producing a catalyst for purifying exhaust gas,

Forming a first coating area by coating a high concentration coating liquid with each channel of the carrier through a first coating liquid suction amount adjusting device by an inhaler;

Rotating the carrier coated with the high concentration coating solution in a vertical direction; And

Coating the low concentration coating liquid with each channel of the carrier through the second coating liquid suction amount adjusting device by the inhaler to form a second coating region in a rearward direction of the first coating region, wherein the first coating region is a reaction gas. In consideration of the flow and mass transfer coefficients of the coating length is characterized in that the shape made larger toward the center.

As a preferred embodiment, the first coating liquid suction amount control device is made of a structure in which the size of the air suction cell is larger toward the center, the second coating liquid suction amount control device is smaller in size toward the center of the air suction cell Characterized in that consisting of.

In a more preferred embodiment, the first and second coating liquid suction amount control device is characterized in that the outer surface is a rubber material that can be completely sealed.

As described above, according to the catalyst for purification of exhaust gas and the method for manufacturing the same according to the present invention, by applying the zone coating method considering the flow of the reaction gas and the mass transfer coefficient, the catalytic converter is warmed up early to improve the purification efficiency of the catalyst. Can be maximized.

In addition, by converting a portion of the high concentration coating area having a low flow rate and mass transfer of the reaction gas at the front end portion of the catalyst into a low concentration coating area having a high flow rate and mass transfer, the amount of precious metal used in the catalyst can be minimized.

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

2 is a schematic view showing a catalyst for purification of exhaust gas produced by the flow-considered zone coating method of the present invention.

The present invention can minimize the amount of precious metal used in the catalyst 15, and maximize the purification efficiency of the catalyst 15 by considering the coating method considering the material movement and flow at the same time.

For this purpose, the pattern of the zone coating method for coating the high concentration of precious metal on the front end of the catalyst 14 should be changed as shown in FIG.

3 is a view for comparing the noble metal content shown in FIGS. 1 and 2.

That is, the amount of precious metal coated on the shear high concentration coating region 10 in FIG. 1 and the shear high concentration coating region 10 improved in the present invention (FIG. 2) is the same, but more toward the center in consideration of the flow pattern of the reaction gas. When viewed from the longitudinal cross section to have a large amount of coating, the smaller area becomes the front end high concentration coating area 12 and the larger area becomes the rear end low concentration coating area 13 bordering the parabola from front to back. .

At this time, if the high concentration coating area is less than 10% of the total volume of the catalyst 15, there is no effect of improving the purification by high concentration, and if it exceeds 50%, the effect of reducing precious metal is inferior. It is preferable that it is -50%.

Therefore, the catalyst coating method proposed in the present invention may be referred to as 'flow consideration zone coating method' in which the coating area becomes larger as it goes to the center in consideration of the flow pattern of the reaction gas.

This is not to increase the amount of precious metals compared to the zone coating, but to move the precious metal amount from the portion of the reaction gas flow to the portion of the flow volume in the zone coating method. There is a difference in shape.

In addition, a portion (D) of the high concentration coating region 10 in the 'zone coating method' is changed to a part (E) of the low concentration coating region 13 in the 'flow consideration zone coating method', and a low concentration coating in the 'zone coating method'. Part of the area (coating solution) is to be changed to a portion of the high concentration coating area (coating solution) in the 'flow consideration zone coating method'. In this way, the coating amount is the same as the region D and the region E, so there is no increase or decrease of the amount of precious metal.

On the other hand, exhaust gas reduction by the catalyst 15 is achieved by three mechanisms depending on the temperature. When the temperature is more than 400 ℃ material movement is a major factor that determines the purification performance, in the case of the actual vehicle is purged by the catalyst (15) at a temperature over 500 ℃ except for the initial 20 seconds.

In consideration of this, it is very important to manufacture the catalyst 15. The mass transfer coefficient is very large as the local turbulence occurs at the front of the catalyst 15, but decreases rapidly as the flow proceeds to the channel.

Therefore, in the present invention, by improving the exhaust gas flow rate nonuniformity of the inlet portion of the catalyst (15) inevitably from 'Zone Coating' to 'flow consideration zone coating'. It is intended to optimize the performance of the catalyst 15.

In addition, in the catalyst 15 purification mechanism approach, the mass transfer coefficient (K) and the flow rate (Q) are expressed as a function expression for each catalyst 15 region. We propose a method of making a flow coating without increasing the additional production cost.

Hereinafter, the method of optimizing the functional formula and the parabolic zone coating concept and manufacturing method will be described in detail.

In the present invention, in addition to the zone coating method of coating a high concentration of precious metal on the front of the catalyst (15) for early warm-up, we propose a flow consideration zone coating method that can maximize the catalyst purification performance by optimizing the flow rate and mass transfer coefficient. .

4 is a graph showing catalytic purification performance according to temperature in an actual vehicle. In this case, chemical kinetics, pore diffusion, and bulk mass transfer in the graph are factors that affect the conversion efficiency (%) depending on the temperature range.

In actual vehicles, most of the catalyst reaction occurs at temperatures above 500 ° C except for about 20 seconds at the start. Therefore, as shown in the graph of Figure 4 it can be seen that the mass transfer is an important factor in determining the purification performance.

5 is a conceptual diagram and a graph showing a flow rate Q and a mass transfer coefficient K according to an area of a catalyst cross section.

As the reaction gas passes through the catalyst 15, a parabolic laminar flow is formed, and a zone-coated catalyst 15 considering the flow is required to obtain such mass transfer effect only at the catalyst 15 front end.

Also, even at the initial inlet, the flow rate (Q1) and mass transfer (m / s) values at the center are high, and even after the reaction gas passes a certain length of the catalyst 15, the mass transfer (coefficient) value (K1) is still at the center. Since it can be seen that it is high, in order to improve the catalyst 15 purification performance at the point where the mass transfer value is high, it is desirable to coat a high concentration (above a certain value) precious metal.

The purifying capacity of the catalyst 15 is determined by the volume velocity and mass movement in each channel. For example, it is assumed in FIG. 5 that the flow rate flowing into the catalyst 15 is Q1, Q2 (<Q1), Q3 (<Q2) according to the cross section of the catalyst 15. In addition, let the mass transfer coefficients of the channels through which each flow rate pass be K1, K2, K3. In this case, the purification performance according to the section of the catalyst 15 may be expressed as a function (Fn) of the flow rate (Q) and the mass transfer coefficient (K).

Therefore, if the zone coating method of coating a high concentration of precious metal in the section having the largest function value by optimizing the flow rate and mass transfer coefficient in each section can maximize the purification performance of the catalyst (15).

The zone coating of the catalyst 15 thus determined differs slightly depending on the shape of the exhaust system (exhaust manifold, front muffler), but is roughly as shown in FIG.

As described above, the flow consideration zone coating method optimizing the flow rate flowing into the catalyst 15 and the effect of mass transfer occurring in each channel of the catalyst 15 will be described as follows.

7 is a process chart showing a manufacturing process of the flow consideration zone coating method of the present invention, Figure 8 is a plan view showing a high concentration coating liquid suction amount control apparatus according to an embodiment of the present invention, Figure 9 is a high concentration coating liquid suction amount control in Figure 7 Figure 10 is an exploded view of the device and the catalyst, Figure 10 is a plan view showing a low concentration coating liquid suction amount control apparatus according to an embodiment of the present invention, Figure 11 is an exploded view showing a low concentration coating liquid suction amount control apparatus according to an embodiment in FIG.

As shown in FIG. 8, the coating liquid suction amount adjusting device 17 for the catalyst shear part has a larger cell size toward the center portion, and an outer portion of the tube is made of a rubber material that can be completely sealed so that suction air from the inhaler does not leak to the outside. Is done.

In addition, as shown in FIG. 10, the coating liquid suction amount adjusting device 18 for the rear end of the catalyst has a smaller cell size toward the center portion, and the outer portion of the tube can be completely sealed so that the suction air is not leaked to the outside by the inhaler. It is made of rubber material.

When the coating liquid suction amount adjusting devices (17, 18) for the catalyst front end and the catalyst rear end having the same structure as described above are prepared, the catalyst 15 by the flow consideration zone coating method can be manufactured as shown in FIG. have.

First, a coating liquid container containing a high concentration of coating solution is provided so that the lower end of the catalyst (carrier 1) can be contacted. Subsequently, when the suction pressure is provided using the inhaler 16 and the coating liquid suction amount adjusting device 17 (first control tube) for coating the catalyst shear, the coating solution having a high concentration moves upward through the channel inside the catalyst 15. This is done.

In this case, since the first control tube has a larger cell size toward the center, the suction pressure of each channel increases as the coating pressure is increased toward the center during suction of the coating liquid through the inhaler 16, while the coating length of each channel becomes longer, whereas the outer portion of the cell The small size makes the coating length short.

Therefore, as shown in FIG. 7, the coating length of each channel is coated in a parabolic form from the bottom of the catalyst 15 to form a high concentration coating region 12.

Then, the catalyst 15 is rotated in the vertical direction to provide a coating liquid container containing a low concentration of the coating solution, so that the lower end of the catalyst 15 can be contacted. Subsequently, when the suction pressure is provided using the inhaler 16 and the coating liquid suction amount adjusting device 18 (second control tube) for coating the rear end of the catalyst, the coating solution of low concentration moves upward through the channel inside the catalyst 15, and the coating is performed. This is done.

In this case, since the cell size decreases toward the center of the second control tube, the suction pressure of each channel decreases toward the center when the coating liquid is inhaled through the inhaler 16, thereby shortening the coating length of each channel. The large cell size increases the coating length.

Thus, as shown in FIG. 7, the coating length end of each channel from the bottom of the catalyst 15 is coated in a parabolic form (facing upward) to form a low concentration coating region 13.

The zone coated catalyst 15 is completed by the above-described flow consideration zone coating method.

Here, in order to control the length of the front and rear ends of the flow-considered zone coating, the cell size of the coating liquid suction amount adjusting devices 17 and 18 is adjusted, or the suction pressure is adjusted while the coating liquid suction amount adjusting device is mounted, so that the flow-considering zone coating Catalyst 15 may be prepared.

Test Example

In order to evaluate the performance of the flow consideration zone coating, simulation activity evaluation was performed after aging 1000 degrees and 100 hours by electric furnace aging. As shown in FIGS. 12 and 13, the LOT performance was 20 degrees and the purification rate was 5%. It was found that the improvement.

This could improve the performance of the catalyst 15 without additional use of precious metals and by adding a simple suction control device without a significant increase in manufacturing cost.

While the invention has been shown and described with respect to certain preferred embodiments thereof, the invention is not limited to these embodiments, and has been claimed by those of ordinary skill in the art to which the invention pertains. It includes all the various forms of embodiments that can be carried out without departing from the spirit.

1 is a schematic view showing an exhaust gas purification catalyst prepared by the zone coating method.

2 is a schematic view showing a catalyst for purification of exhaust gas produced by the flow consideration zone coating method of the present invention.

3 is a conceptual diagram for comparing the coating area of the zone coating method and the flow consideration zone coating method.

Figure 4 is a graph showing the factors affecting the catalytic performance with temperature.

5 is a view for explaining the flow and mass transfer effects of the reaction gas.

6 is a process chart showing a manufacturing process of the zone coating method.

7 is a process chart showing the manufacturing process of the flow consideration zone coating method of the present invention.

8 is a plan view showing a high concentration coating liquid suction amount control device according to an embodiment of the present invention.

FIG. 9 is an exploded view of a high concentration coating liquid inhalation control device and catalyst in FIG. 7.

10 is a plan view showing a low concentration coating solution suction amount control device according to an embodiment of the present invention.

FIG. 11 is a plan view illustrating a low concentration coating liquid suction amount adjusting apparatus according to an embodiment in FIG. 7.

12 is a graph showing the low temperature activity evaluation of the present invention.

Figure 13 is a graph showing the high temperature activity evaluation of the present invention.

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

10,12: high concentration coating area 11,13: low concentration coating area

14,15 catalyst 16: inhaler

17: high concentration coating liquid suction amount control device

18: low concentration coating liquid suction amount control device

Claims (6)

In the catalyst for exhaust gas purification, The catalyst front end is composed of a first coating region coated with a high concentration of precious metals, and the catalyst rear end is composed of a second coating region coated with a low concentration of precious metals. It can warm up early and improve the purification performance. The catalyst coating for exhaust gas purification, characterized in that the coating length of the first coating area of the catalyst front end portion coated with the high concentration of noble metal is made longer from the outer portion to the center portion. The method according to claim 1, The first and second coating areas are coated with respective concentrations of the coating liquid through a suction amount control device having a different cell size and coated on each channel inside the catalyst, and the suction amount control device has a center of the cell size for high concentration coating. A catalyst for purifying exhaust gas, comprising a first coating liquid suction amount adjusting device having an increasingly larger structure, and a second coating liquid suction amount controlling device having a smaller size as a cell toward a central portion for low concentration coating. The method according to claim 2, The first coating region is an exhaust gas purification catalyst, characterized in that 10 to 50% of the total volume of the catalyst. delete In the manufacturing method of the catalyst for exhaust gas purification, Forming a first coating area by coating a high concentration coating liquid with each channel of the carrier through a first coating liquid suction amount adjusting device by an inhaler; Rotating the carrier coated with the high concentration coating solution in a vertical direction; And Coating the low concentration coating liquid with each channel of the carrier through the second coating liquid suction amount adjusting device by the inhaler to form a second coating region in a rearward direction of the first coating region, wherein the first coating region is a reaction gas. In consideration of the flow and mass transfer coefficient of the coating length is made to grow toward the center, The first coating liquid suction amount adjusting device is made of a structure that the size of the air suction cell is larger toward the center, the second coating liquid suction amount adjusting device is characterized in that the size of the air suction cell is made smaller toward the center Method for producing a catalyst for purification of exhaust gas. The method according to claim 5, The first and second coating liquid suction amount control device is a method for producing a catalyst for purification of exhaust gas, characterized in that the outer surface is a rubber material that can be completely sealed.

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