JP2020133597A - Exhaust emission control device - Google Patents

Abstract

To provide an exhaust emission control device capable of early increasing a temperature of a second catalyst from start of an engine and enhancing purification efficiency of exhaust gas earlier compared to conventional cases even when a first catalyst and the second catalyst through which exhaust gas from the first catalyst passes are provided.SOLUTION: An exhaust emission control device 3 includes an exhaust emission control catalyst 32 that purifies exhaust gas from an exhaust manifold 29. The exhaust emission control catalyst 32 includes a first catalyst 34 purifying the exhaust gas from the exhaust manifold 29, and a second catalyst 35 purifying the exhaust gas that has passed through the first catalyst 34. The heat capacity of the first catalyst 34 is smaller than that of the second catalyst 35. In the first catalyst 34, a metallic catalyst purifying exhaust gas is supported on wall surfaces of a plurality of cells formed in a carrier 34' comprising a metallic material. The exhaust emission control device 3 includes a heating device 31 heating the first catalyst 34 by microwaves, and in the first catalyst 34, powder having higher magnetic permeability than that of the metallic material of the carrier 34' is disposed in the plurality of cells.SELECTED DRAWING: Figure 3

Description

The present invention relates to an exhaust gas purification device provided with an exhaust gas purification catalyst that purifies the exhaust gas from the exhaust manifold.

Conventionally, an exhaust gas purifying device has been connected to an exhaust manifold in order to purify the exhaust gas discharged from the engine. The exhaust gas purification device includes a catalyst that purifies the exhaust gas from the exhaust manifold, and the catalyst is composed of a metal catalyst that purifies the exhaust gas and a carrier (catalyst carrier) that supports the metal catalyst.

For example, in Patent Document 1, as such an exhaust gas purification device, an exhaust gas purification device including a first catalyst that purifies the exhaust gas from the exhaust manifold and a second catalyst that purifies the exhaust gas that has passed through the first catalyst. Is disclosed. In this exhaust gas purification device, the first catalyst has a smaller heat capacity than the second catalyst. As a result, the temperature of the first catalyst can be raised at an early stage, and the exhaust performance at the time of starting the engine can be improved.

Japanese Unexamined Patent Publication No. 2015-165895

However, even with the configuration as described in Patent Document 1, the heat generated during the reaction of the exhaust gas in the first catalyst enters the exhaust gas passing through the first catalyst at the stage where the first catalyst is activated at the time of starting the engine. However, a larger amount of heat than the amount of heat input may be absorbed by the first catalyst itself. That is, when a large amount of heat of the exhaust gas is taken away by the first catalyst, the temperature of the exhaust gas passing through the first catalyst and heading toward the second catalyst may be lower than that in the case where the first catalyst is not provided. As a result, the time from the start of the engine to the activation of the second catalyst is delayed, and the time from the start of the engine to the achievement of a predetermined purification efficiency may be longer than when the first catalyst is not provided. ..

The present invention has been made in view of these points, and even when the first catalyst and the second catalyst through which the exhaust gas from the first catalyst passes are provided, the second catalyst is provided from the time of starting the engine. It is an object of the present invention to provide an exhaust gas purification device capable of raising the temperature of the exhaust gas at an early stage and increasing the purification efficiency of the exhaust gas earlier than before.

In view of the above problems, as a result of diligent studies by the inventor, if the heat capacity of the first catalyst is made extremely smaller than the heat capacity of the second catalyst, when the exhaust gas from the exhaust manifold passes through the first catalyst. In addition, it was thought that the heat of the exhaust gas could be suppressed from being taken away by the first catalyst. Here, until now, it has been considered that when the heat capacity of the catalyst is extremely reduced, the size of the catalyst is extremely reduced, so that the exhaust gas purification performance is almost nonexistent. However, as is clear from the experiments described later by the inventor, even if the first catalyst is extremely small compared to the second catalyst, the first catalyst sufficiently contributes to the purification of exhaust gas, and the first catalyst is microwaved. We have obtained a new finding that the efficiency of exhaust gas purification can be further improved by heating with a catalyst.

The present invention is based on the new knowledge of the present inventor, and the exhaust gas purification device according to the present invention is an exhaust gas purification device provided with an exhaust gas purification catalyst for purifying the exhaust gas from the exhaust manifold, and is the exhaust gas purification catalyst. Includes a first catalyst that purifies the exhaust gas from the exhaust manifold and a second catalyst that purifies the exhaust gas that has passed through the first catalyst, and the heat capacity of the first catalyst is that of the second catalyst. The first catalyst, which is smaller than the heat capacity, has a metal catalyst for purifying exhaust gas supported on the wall surface of a plurality of cells formed on a carrier made of a metal material, and the exhaust gas purifying device is the first. A heating device for heating the catalyst with a microwave is provided, and the first catalyst is characterized in that powders having higher magnetic permeability than the metal material of the carrier are arranged in the plurality of cells.

According to the present invention, even if a relatively low temperature exhaust gas passes through the first catalyst from the exhaust manifold when the engine is started, the heat capacity of the first catalyst is small as described above, so that the temperature of the first catalyst rises early. Will be done. Further, since the heat of the exhaust gas passing through the first catalyst is not easily taken away by the first catalyst, the heat of the exhaust gas passing through the first catalyst is used to raise the temperature of the second catalyst at an early stage following the first catalyst. Can be done. As a result, the first catalyst is activated earlier than before when the engine is started, and the second catalyst is also activated earlier than before, so that the exhaust gas purification efficiency is improved earlier than when the engine is started. be able to.

Here, the first catalyst is a catalyst in which a metal catalyst for purifying exhaust gas is supported on the wall surfaces of a plurality of cells formed on a carrier made of a metal material. Therefore, the carrier of the first catalyst can be heated by the microwave by the heating device.

In addition to this, in the present invention, powders having higher magnetic permeability than the metal material of the carrier are arranged in the plurality of cells of the first catalyst. A powder (material) having a higher magnetic permeability than a metal material of a carrier has a higher absorption rate of microwaves than a metal material of a carrier. By arranging such powder in a plurality of cells, the inside of the first catalyst can be efficiently heated by microwaves, so that the temperature of the first catalyst can be raised in a shorter time. As a result, the temperature of the second catalyst can be raised earlier than before when the engine is started, and the purification efficiency of the exhaust gas can be improved earlier than before.

It is a schematic conceptual diagram for demonstrating the exhaust gas purification apparatus which concerns on embodiment of this invention. It is a schematic perspective sectional view of the 1st catalyst converter of the exhaust gas purification apparatus shown in FIG. It is a schematic plan view of the 1st catalyst converter shown in FIG. It is a photograph of the first catalyst which concerns on Example 3. It is a graph which showed the temperature rise time of the 1st catalyst of Examples 1 to 4 and Comparative Examples 1 to 3.

The exhaust gas purification device according to the embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a schematic conceptual diagram for explaining the exhaust gas purification device 3 according to the embodiment of the present invention, and FIG. 2 is a schematic perspective cross section of the first catalytic converter 30 of the exhaust gas purification device 3 shown in FIG. It is a figure. In FIG. 2, the housing 33 is shown in a half-split state in order to show the inside of the first catalytic converter 30.

As shown in FIG. 1, the exhaust gas purification device 3 according to the present embodiment is a device attached downstream of the engine 2 and purifying the exhaust gas after combustion by the engine 2. The engine 2 may be either a gasoline engine or a diesel engine, and in the present embodiment, a gasoline direct injection engine is illustrated as an example thereof in FIG.

In the engine 2, the air sucked through the intake valve 25 flows into the combustion chamber formed by the cylinder block 21 and the piston 22, and is mixed with the fuel (gasoline) injected by the fuel injection valve 28. The mixed air-fuel mixture is ignited by the spark plug 27 and burned in the combustion chamber, and the exhaust gas after combustion is discharged from the exhaust manifold 29 via the exhaust valve 26.

The exhaust gas exhausted by the exhaust manifold 29 is purified by the exhaust gas purification device 3. Specifically, the exhaust gas purification device 3 is connected to the first catalyst converter 30 connected to the exhaust manifold 29 and to the first catalyst converter 30 via the exhaust pipe 36 downstream of the first catalyst converter 30. It includes a second catalytic converter 37. The first catalytic converter 30 is arranged, for example, in the engine room of the vehicle (not shown), and the second catalytic converter 37 is arranged, for example, under the floor of the vehicle (not shown).

The first catalyst converter 30 includes an exhaust gas purification catalyst 32 that purifies the exhaust gas from the exhaust manifold 29, and a housing 33 that houses the exhaust gas purification catalyst 32. Similarly, the second catalyst converter 37 also includes an exhaust gas purification catalyst 38 that further purifies the exhaust gas that could not be purified by the first catalyst converter 30, and a housing 39 that houses the exhaust gas purification catalyst 38. The housings 33, 39 are made of a metal material such as stainless steel, carbon steel, or aluminum.

As shown in FIG. 2, the housing 33 of the first catalytic converter 30 is composed of an inlet cone portion 33a, a body portion 33b, and an outlet side cone portion 33c. The inlet cone portion 33a has a cone shape in which the exhaust gas from the exhaust manifold 29 flows in and the cross section of the exhaust gas flow path expands from the upstream to the downstream of the exhaust gas. The body portion 33b is formed continuously on the inlet side cone portion 33a on the upstream side where the exhaust gas flows, and has a tubular shape with a constant flow path cross section of the exhaust gas. The outlet side cone portion 33c is formed continuously on the body portion 33b on the upstream side where the exhaust gas flows, and has a cone shape in which the flow path cross section of the exhaust gas is reduced from the upstream side to the downstream side of the exhaust gas.

In the present embodiment, the exhaust gas purification catalyst 32 of the first catalyst converter 30 includes a first catalyst 34 that purifies the exhaust gas from the exhaust manifold 29 and a second catalyst 35 that purifies the exhaust gas that has passed through the first catalyst 34. ing. The first catalyst 34 is arranged in the inlet cone portion 33a, and the second catalyst 35 is arranged in the body portion 33b.

In the present embodiment, since the engine 2 is a gasoline engine, the first catalyst 34 and the second catalyst 35 are hydrocarbons (HC), carbon monoxide (CO), and oxide oxides (NOx) of the exhaust gas of the gasoline engine. ) Is a three-way catalyst that purifies. On the other hand, when the internal combustion engine is a diesel engine, the first catalyst 34 and the second catalyst 35 are oxidation catalysts for removing carbon monoxide (CO), hydrocarbons (HC) and the like. As for the exhaust gas purification catalyst 38 housed in the second catalyst converter 37, the same catalysts as those of the first and second catalysts 34 and 35 are set according to the type of the internal combustion engine.

In the first catalyst 34 and the second catalyst 35, a metal catalyst for purifying exhaust gas is supported on carriers (catalyst carriers) 34'and 35'. These carriers are made of metallic materials. The metal material is preferably a material having heat resistance and corrosion resistance, and examples thereof include stainless steel and aluminum.

Here, the specific heat of a metal material such as stainless steel, which is a material of a carrier, is smaller than the specific heat of a ceramic material such as Kojilite, which is a material of a carrier. By using the carrier 34'of the first catalyst 34 as a carrier made of a metal material, it is possible to easily produce a catalyst that satisfies the conditions of the heat capacity of the first catalyst 34 as described later. In addition to this, since the first catalyst 34 satisfies the condition of a heat capacity extremely smaller than that of the second catalyst 35 as described later, the carrier made of ceramic material is easily cracked by thermal shock or the like, but the carrier made of metal material. If set to, such cracks can be avoided.

As shown in FIGS. 2 and 3, the carrier 34'of the first catalyst 34 has a disk shape, and a honeycomb structure in which a plurality of cells through which exhaust gas passes are formed inside a ring-shaped metal frame 34a. The body. Specifically, the carrier 34'forms a plurality of cells by superimposing and winding a wavy metal strip 34b and a plate-shaped metal strip 34c inside the metal frame 34a. are doing. An opening 34d through which the exhaust gas passes is formed in the center of the first catalyst 34. The opening 34d has a substantially circular shape and has a larger flow path cross section than each cell.

As shown in FIG. 2, the length t of the first catalyst 34 along the direction in which the exhaust gas passes is 2 to 7 mm. Further, the thickness of the wall portion (specifically, the metal strip 34c) forming the cell is preferably 20 to 50 μm. By satisfying such a thickness, the carrier 34'of the first catalyst 34 is easily heated. The inner diameter of the metal frame 34a is preferably 60 to 90 mm, and the number of cells formed by superimposing and winding the metal strips 34c is 47 to 140 cells / cm ² (300 to 900 cells). It is preferably in the range of / inch).

On the other hand, in the present embodiment, the carrier of the second catalyst 35 is a columnar carrier made of a metal material or a ceramic material and having a honeycomb structure in which a plurality of cells through which exhaust gas passes are formed. When it is a metallic material, it is made of the same material as the carrier 34'of the first catalyst 34. In the case of a ceramic material, for example, a porous ceramic material containing any one of alumina, zirconia, cordylite, titania, silicon carbide, silicon nitride and the like as a main component can be mentioned. be able to. The same applies to the carrier of the exhaust gas purification catalyst 38.

Further, in the first catalyst 34, powders having higher magnetic permeability (high magnetic permeability powder) than the metal material of the carrier 34'are arranged in a plurality of cells. Specifically, the high magnetic permeability powder is added to the circumferential cell group 34f arranged on the outer peripheral side of the carrier 34'and the four radial cell groups 34g arranged continuously from the outer circumference to the inner circumference of the carrier 34'. Is filled. In the present embodiment, the four radial cell groups 34g are arranged at 90 ° intervals about the opening 34d of the carrier 34'in a plan view, but the number and arrangement state are not particularly limited. Further, each radial cell group 34g is continuous with the circumferential cell group 34f.

In the present embodiment, the circumferential cell group 34f and the radial cell group 34g are filled with the high magnetic permeability powder. The material of the high magnetic permeability powder may be a powder having a higher magnetic permeability than the metal material of the first catalyst 34. For example, the material thereof is nickel-iron oxide (for example, nickel ferrite such as NiFeO ₂ ). Examples include iron-nickel alloys (eg, permalloy), iron-silicon-aluminum alloys (eg, sendust), and the like.

The magnetic permeability of the material of such a high magnetic permeability powder is preferably 1 × 10 ^-4 H / m or more, and preferably 2.5 × 10 ^-1 H / m or less. Further, the bulk density of the high magnetic permeability powder is preferably 3.7 g / cm ³ or more. This makes it possible to fill one cell with more high magnetic permeability powder. In the following examples, this high magnetic permeability powder is referred to as a microwave absorber.

Further, the metal catalysts of the first catalyst 34 and the second catalyst 35 are granular and are supported on the inner wall surface forming these cells via a ceramic material. As the metal serving as the metal catalyst, a noble metal containing at least one of platinum, rhodium, and palladium is selected. Examples of the ceramic material supporting the metal catalyst on the carrier include a mixed material of zirconia and alumina, ceria and alumina, or ceria-zirconia and alumina. When the metal catalyst is supported on the carrier, it can be obtained by coating the carrier with a slurry containing the above-mentioned ceramic material and the metal catalyst and firing the slurry. In addition to these metal catalysts, the above-mentioned high magnetic permeability powder may be further supported. In general, the metal catalyst has a lower magnetic permeability than the materials of the commonly used carriers 34'and 35'such as stainless steel.

In the present embodiment, the heat capacity of the first catalyst 34 is smaller than the heat capacity of the second catalyst 35. Specifically, the heat capacity of the first catalyst 34 is 20 J / K or less in a temperature environment of 25 ° C., and the heat capacity of the second catalyst 35 is 184 to 322 J / K in a temperature environment of 25 ° C.

The range of the heat capacity of the second catalyst 35 is the heat capacity of the catalyst applied according to the displacement of the engine of a vehicle that is generally on the market, and this heat capacity can be obtained by appropriately selecting the above-mentioned material or the like. Can be contained in the range of. When the heat capacity of the second catalyst 35 is less than 184 J / K, the size (heat capacity) of the second catalyst 35 is too small, and the exhaust gas purification performance is not sufficient. On the other hand, when the heat capacity of the second catalyst 35 exceeds 322 J / K, the size (heat capacity) of the second catalyst 35 is too large, so that the temperature rise of the second catalyst 35 due to the exhaust gas is slow when the engine is started. Become.

According to this embodiment, the heat capacity of the first catalyst 34 is 20 J / K or less, which is extremely small with respect to the heat capacity of the second catalyst 35. Therefore, even if the relatively low temperature exhaust gas from the exhaust manifold 29 passes through the first catalyst 34 when the engine 2 is started, the first catalyst 34 has a small heat capacity as described above, so that the first catalyst 34 has a smaller heat capacity than the conventional catalysts. The temperature of the first catalyst 34 is raised at an early stage.

Further, the heat of the exhaust gas passing through the first catalyst 34 is not easily taken away by the first catalyst 34 because the heat capacity of the first catalyst 34 is small, and the heat of reaction with the metal catalyst is added to the heat of the exhaust gas. Therefore, the heat of the exhaust gas that has passed through the first catalyst 34 can raise the temperature of the second catalyst 35 at an early stage following the first catalyst 34 from the start of the engine 2. As a result, the first catalyst 34 is activated earlier than before from the start of the engine 2, and the second catalyst 35 is also activated earlier than before, so that the purification efficiency of the exhaust gas is improved earlier. be able to.

When the heat capacity of the first catalyst 34 exceeds 20 J / K, the time from the start of the engine 2 to the activation of the second catalyst 35 becomes longer than when the first catalyst 34 is not provided. From the viewpoint of manufacturing, the heat capacity of the first catalyst 34 is preferably 3 J / K or more.

Further, since the heat capacity of the first catalyst 34 is 20 J / K or less in a temperature environment of 25 ° C., the size of the first catalyst 34 is considerably smaller than that of a conventional general catalyst. Therefore, the first catalyst 34 can be easily arranged without newly providing a space for arranging the first catalyst 34.

In particular, in the present embodiment, the second catalyst 35 is arranged in the body portion 33b of the housing 33 of the first catalyst converter 30, and the first catalyst 34 is arranged in the inlet side cone portion 33a, as in the case of the conventional catalysts. Has been done. As a result, the first catalyst 34 having a larger diameter and a shorter length t along the flow path of the exhaust gas can be arranged as compared with the case where the first catalyst 34 is arranged in the exhaust pipe. As a result, the pressure loss of the exhaust gas passing through the first catalyst 34 can be reduced.

In addition to this, by passing through the first catalyst 34, the exhaust gas is rectified on the upstream side of the second catalyst 35, so that the velocity gradient of the exhaust gas toward the second catalyst 35 can be made gentle. The velocity distribution of exhaust gas can be smoothed. As a result, the speed of the exhaust gas passing through the central portion 35a and the outer peripheral portion 35b of the second catalyst 35 shown in FIG. 2 approaches more uniformly, so that the purification efficiency of the second catalyst 35 can be improved.

As described above, the carrier 34'of the first catalyst 34 is made of a metal material. As a result, when arranging the first catalyst 34 on the inlet cone portion 33a of the metal housing 33, the inlet cone portion 33a and the carrier 34'of the first catalyst 34 can be easily joined by welding. Can be done.

In the present embodiment, the first catalyst converter 30 of the exhaust gas purification device 3 oscillates (irradiates) the first catalyst 34 with microwaves from the upstream side of the exhaust gas to the first catalyst 34, thereby causing the first catalyst 34. A heating device (microwave oscillator) 31 for microwave heating is further provided. In this embodiment, the first catalyst 34 may be irradiated with microwaves from the downstream side of the exhaust gas. Further, in the present embodiment, as shown in the drawing, the irradiation direction of the microwave of the heating device 31 is inclined with respect to the disk-shaped axis of the first catalyst 34, but the first catalyst 34 has a heat capacity. Since it is a small (ie) small carrier, there is almost no effect of heating due to this inclination. The conditions of the microwave to be irradiated are preferably in the range of an output of 500 to 5000 W and a frequency of 900 MHz to 5.8 GHz.

According to the present embodiment, the heating device 31 can irradiate the first catalyst 34 with microwaves from the upstream side of the exhaust gas to heat the carrier 34'of the first catalyst 34 with microwaves. In addition to this, powders having a higher magnetic permeability than the metal material of the carrier 34'are arranged in the plurality of cells of the first catalyst 34. A powder (material) having a higher magnetic permeability than the metal material of the carrier 34'has a higher microwave absorption rate than the metal material of the carrier.

By arranging such powder in a plurality of cells, the inside of the first catalyst 34 can be efficiently heated by microwaves, so that the temperature of the first catalyst 34 can be raised in a shorter time. .. As a result, the temperature of the second catalyst 35 can be raised earlier than before when the engine is started, and the purification efficiency of the exhaust gas can be improved earlier than before.

In this way, when the first catalyst 34 and the second catalyst 35 through which the exhaust gas from the first catalyst 34 passes are provided, the metal catalyst can be activated at an early stage by the first catalyst 34 having a small heat capacity. it can. In addition to this, since the carrier 34'of the first catalyst 34 is heated by microwaves, the temperature of the second catalyst 35 can be raised earlier than before from the start of the engine, and the purification efficiency of the exhaust gas can be improved earlier than before. it can.

Further, since the metal catalyst of the first catalyst 34 reacts first with CO and HC of the exhaust gas on the upstream side of the second catalyst 35, deterioration of the metal catalyst of the second catalyst 35 on the downstream side thereof can be suppressed. it can.

Examples of the present invention will be described below.

<Example 1>
The first catalytic converter shown in FIG. 2 was produced as shown below. First, NiFe ₂ O ₄ powder was used as a high magnetic permeability powder (hereinafter referred to as “microwave absorber”) to be applied to the carrier of the first catalyst. NiFe ₂ O ₄ powder and 3% by mass Al ₂ O ₃ sol powder were mixed and kneaded in a mortar while dropping water to prepare a clay-like filler. The bulk density of the NiFe ₂ O ₄ powder was 5.1 g / cm ³ . The Al ₂ O ₃ sol powder is a powder added to adhere the NiFe ₂ O ₄ powder to the wall surface of the cell of the carrier of the first catalyst.

Next, as a carrier (metal base material), a carrier having the shape shown in FIG. 3 was prepared. Specifically, the carrier of the first catalyst is a carrier (metal carrier) made of disc-shaped stainless steel having an outer diameter of 75 mm, an inner diameter of 24 mm, and a thickness of 25 mm, and the thickness of the ring-shaped metal frame is It was 1.0 mm, the thickness of the wavy metal strip and the plate-shaped metal strip was 50 μm, and the number of cells was 400.

Next, the viscous filler is pushed into each cell of the circumferential cell group having a thickness of 3 cells on the outermost circumference and the radial cell group having a width of about 3 mm so that the filler is filled, and at 120 ° C. After drying, it was heat-treated in the air at 500 ° C. for 2 hours. As a result, the carrier of the first catalyst was filled with 5.8 g of NiFe ₂ O ₄ powder.

Before and after filling the filler, prepare a slurry in which the dispersion medium is mixed with the mixture (35% by mass) of the above-mentioned microwave absorber and the metal catalyst so as to have the ratio shown in Table 1 below. The carrier was coated, dried at 120 ° C., and then heat-treated in the air under heat treatment conditions of 500 ° C. for 2 hours. As a result, the carrier of the first catalyst was filled with 6.4 g of NiFe ₂ O ₄ powder, and the cell filled with the filler of NiFe ₂ O ₄ powder was 20% of the cross section of the carrier. ..

<Example 2>
A first catalyst was prepared in the same manner as in Example 1. The difference from Example 1 is that permalloy powder is used as the microwave absorber applied to the carrier of the first catalyst. The bulk density of the permalloy powder was 8.7 g / cm ³ . The amount of permalloy powder filled in the cell as a filler was 15.8 g, and the total amount of permalloy powder adhering to the carrier by the coating material together with the metal catalyst was 16.4 g.

<Example 3>
A first catalyst was prepared in the same manner as in Example 1 (see FIG. 4). The difference from Example 1 is that sendust powder is used as the microwave absorber applied to the carrier of the first catalyst. The bulk density of the sendust powder was 6.9 g / cm ³ . The amount of sendust powder filled in the cell as a filler was 12.8 g, and the total amount of sendust powder was adjusted to 13.4 g by combining the metal catalyst and the sendust powder adhering to the carrier with the coating material.

<Example 4>
A first catalyst was prepared in the same manner as in Example 1. The difference from Example 1 is that the amount of NiFe ₂ O ₄ powder filled in the cell as a filler is 4.4 g, and the NiFe ₂ O ₄ powder adhered to the carrier by the coating material is further combined with the metal catalyst to add NiFe ₂ the total amount of O ₄ powder lies in that the 5.0 g.

<Comparative example 1>
A first catalyst was prepared in the same manner as in Example 1. The difference from Example 1 is that the filler was not used, the coating material shown in Table 2 below was used, and the microwave absorber was not added to the coating material.

<Comparative example 2>
A first catalyst was prepared in the same manner as in Example 1. The difference from Example 1 is that SiC powder is used instead of the microwave absorber applied to the carrier of the first catalyst. The bulk density of the SiC powder was 3.2 g / cm ³ . The amount of SiC powder filled in the cell as a filler was 0.8 g, and the total amount of SiC powder adhering to the carrier by the coating material together with the metal catalyst was 1.4 g.

<Comparative example 3>
A first catalyst was prepared in the same manner as in Example 1. The difference from Example 1 is that SiC powder is used instead of the microwave absorber applied to the carrier of the first catalyst. The bulk density of the SiC powder was 3.2 g / cm ³ . The amount of SiC powder filled in the cell as a filler was 0.8 g, and the total amount of SiC powder adhering to the carrier by the coating material together with the metal catalyst was adjusted to 3.5 g.

The first catalysts of Examples 1 to 4 and Comparative Examples 1 to 3 were irradiated with microwaves under the conditions of 500 W, 2.45 GHz, and 10 seconds, and the temperature before and after the irradiation was measured with a non-contact thermometer. It was measured. In addition, these heat capacities were also measured. The results are shown in Table 3 and FIG.

From the results of Table 3 and FIG. 5, the temperature rise of the first catalysts of Examples 1 to 4 filled with the microwave absorber was larger than those of Comparative Examples 1 to 3 due to the irradiation of microwaves. In particular, when Sendust and Permalloy are used as in Examples 2 and 3, the bulk density is higher than that of NiFe ₂ O ₄ and SiC due to the nature of the materials, so that more powder can be added to the cell. It will be possible to fill. In particular, in the case of sendust, since the absorption rate of microwaves is high, it can be said that the temperature rise temperature of the first catalyst of Example 3 was high. From this result, iron-silicon-aluminum alloy powder (iron-based alloy with silicon and aluminum added) powder, such as Sendust, is a material with high microwave absorption (material with high magnetic permeability). Is considered preferable.

Next, as a second catalyst, a ceramic carrier made of cordylite having a diameter of 103 mm was prepared, coated with 100 g of a slurry having the composition shown in Table 4, dried at 120 ° C., and then 500 in the air. The heat treatment was performed under the heat treatment conditions of ℃ for 2 hours.

Next, the first catalyst according to the first embodiment is welded to the inlet cone portion of the housing, and then the body portion is welded to the inlet cone portion, and then the second catalyst is attached to the body portion of Aron Ceramics (registered trademark). Fixed with. Finally, the protruding cone part was welded to the body part. As a result, the first catalytic converter according to Example 1 was obtained.

The second catalyst was heated by irradiating the second catalyst from between the first catalyst and the second catalyst with conditioned microwaves of 500 W, 2.45 GHz, and 10 seconds. When the temperature difference before and after the microwave irradiation of the first catalyst was measured, the temperature was raised by 15 ° C. It was confirmed that the microwaves that could not be absorbed by the second catalyst were absorbed by the first catalyst and the first catalyst was heated.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various types are described within the scope of the claims without departing from the spirit of the present invention. It is possible to make design changes.

In the present embodiment, the microwave is irradiated toward the first catalyst. For example, a heating device for heating with the microwave is arranged between the first catalyst and the second catalyst, and the microwave is directed at the second catalyst. The first catalyst may be heated by microwaves dissipated from the second catalyst.

2: Engine, 29: Exhaust gas manifold, 3: Exhaust gas purification device, 30: First catalyst converter (catalyst converter), 31: Heating device, 32: Exhaust gas purification catalyst, 33: Housing, 33a: Input side cone, 33b: Body part, 33c: Exhaust side cone part, 34,34A, 34B: First catalyst, 34f: Circumferential cell group, 34g: Radial cell group, 35: Second catalyst

Claims (1)

An exhaust gas purification device equipped with an exhaust gas purification catalyst that purifies the exhaust gas from the exhaust manifold.
The exhaust gas purification catalyst includes a first catalyst that purifies the exhaust gas from the exhaust manifold and a second catalyst that purifies the exhaust gas that has passed through the first catalyst.
The heat capacity of the first catalyst is smaller than the heat capacity of the second catalyst.
The first catalyst is a catalyst in which a metal catalyst for purifying exhaust gas is supported on the wall surfaces of a plurality of cells formed on a carrier made of a metal material.
The exhaust gas purification device includes a heating device that heats the first catalyst with microwaves.
An exhaust gas purification device characterized in that powder having a higher magnetic permeability than the metal material of the carrier is arranged in the plurality of cells of the first catalyst.