JPH07148429A - Catalyst for cleaning exhaust gas from engine and manufacture of the same - Google Patents

Abstract

PURPOSE:To improve an HC (hydrocarbon) cleaning rate by making a structure in which hydrocarbons released from an HC adsorbent can contact easily with a catalyst metal. CONSTITUTION:In a catalyst for cleaning exhaust gas from engines in which HC adsorbent powder 13 is dispersed on the surface of a carrier 12, a catalyst metal 14 for cleaning untreated exhaust gas is dispersed at least on the outside of the powder 13.

Description

Detailed Description of the Invention

[0001]

This invention relates to a three-way catalyst (TWC)
Is loaded with an HC adsorbent, and HC (hydrocarbon), CO (carbon monoxide), N discharged from the exhaust port of the engine
The present invention relates to an engine exhaust gas purifying catalyst for purifying Ox (nitrogen oxide) harmful gas and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as an exhaust gas purifying catalyst for an engine of the above-mentioned example, for example, there is a catalyst described in JP-A-3-202154. That is, as shown in FIG. 11, cordierite (chemical symbol Mg ₂ Al) is used.
₄ Si ₅ O ₁₈ ) etc. honeycomb-shaped carrier 1 for supporting catalyst components
Alumina layer containing Pt—Rh catalyst component (platinum / rhodium catalyst component) on the surface of 01 (specifically, γ-Al ₂ O
_A first coating layer 102 composed of _three layers), and a second coating layer 103 containing CeO ₂ (cerium oxide) and an HC adsorbent that adsorbs unburned gas components of the engine on the first coating layer 102. The exhaust gas purifying catalyst 104 is provided.

According to this conventional exhaust gas purifying catalyst 104, when the exhaust gas is flowing through the large number of pores 105 of the honeycomb carrier, the HC in the exhaust gas is low at a low temperature.
(Hydrocarbon) is the second coat layer 1
When it is adsorbed by the HC adsorbent in 03 and the exhaust gas temperature rises, HC is desorbed from the HC adsorbent and the first coat layer 1
While it has the advantage that it can be diffused and purified in 02 and the purification rate can be increased, the first coat layer 102 of Pt-Ph-based catalyst metal is formed inside the second coat layer 103 containing the HC adsorbent. However, there is a problem that sufficient contact between the desorbed HC and the catalyst metal cannot be obtained, and a good improvement of the HC purification rate cannot be achieved.

[0004]

The invention according to claim 1 of the present invention has a structure in which HC released from an HC adsorbent that adsorbs HC is easily contacted with a catalytic metal, thereby purifying HC. It is an object of the present invention to provide a catalyst for purifying exhaust gas of an engine, which can sufficiently improve the efficiency.

According to the second aspect of the present invention, the surface of the carrier for supporting the catalyst component is coated with the first coat layer containing the HC adsorbent, and then the second coat layer containing the catalyst metal is coated. When the HC adsorbed by the HC adsorbent in the first coat layer desorbs and goes out, the engine always passes through the second coat layer containing the catalytic metal to sufficiently purify the released HC. It is an object of the present invention to provide a method for producing the exhaust gas purifying catalyst.

According to a third aspect of the present invention, by coating a catalyst component-supporting carrier with a catalyst metal-supporting HC adsorbent powder in which a thin catalytic metal is disposed on the surface of the HC adsorbent powder, When the catalyst is desorbed and released, the catalyst metal on the surface of the HC adsorbent powder burns and removes the released HC to provide a method for producing a catalyst for purifying exhaust gas of an engine, which can sufficiently improve the HC purification rate. To aim.

According to a fourth aspect of the present invention, the catalyst component-supporting carrier is coated with a slurry in which the catalyst metal-supporting cerium oxide and the HC adsorbent powder are mixed, so that the catalyst metal site at the time of HC release. An object of the present invention is to provide a method for producing an exhaust gas purifying catalyst for an engine, in which oxygen is supplied from CeO ₂ (cerium oxide), HC is burned and removed by an oxidation reaction, and the HC purification rate can be sufficiently improved.

According to the fifth aspect of the present invention, by using the catalyst metal-supporting binder in which the catalyst metal is disposed on the binder, it becomes easy to adjust the mixing with the HC adsorbent powder and improve the productivity. An object of the present invention is to provide a method for producing a catalyst for purifying exhaust gas of an engine, which can be achieved.

According to the sixth aspect of the present invention, the surface of the catalyst component supporting carrier is coated with the HC adsorbent powder, and then the surface of the adsorption supporting catalyst carrier is coated with the catalytic metal supporting cerium oxide powder. , When the HC adsorbed by the HC adsorbent is desorbed and goes out, it always passes through the layer having the catalyst metal and CeO ₂ (cerium oxide), and the catalyst metal burns and removes the released HC. _The purpose of the present invention is to provide a method for producing an exhaust gas purifying catalyst for an engine, which can accelerate the oxidation reaction by supplying oxygen from ₂ to burn and remove HC more satisfactorily and to sufficiently improve the HC purification rate. And

The invention according to claim 7 has the object of the invention according to claim 2, 3, 4, 5 or 6 above.
It is an object of the present invention to provide a method for producing a catalyst for purifying exhaust gas of an engine, which can achieve a desired object by setting the above coating to a wash coat.

[0011]

The invention according to claim 1 of the present invention is a catalyst for purifying exhaust gas of an engine, in which HC adsorbent powder for adsorbing HC is dispersed and arranged on the surface of a carrier for supporting a catalyst component. The catalyst is a catalyst for purifying exhaust gas of an engine in which a catalyst metal for purifying unpurified exhaust gas components is dispersedly arranged at least outside the HC adsorbent powder.

According to a second aspect of the present invention, after the surface of the carrier for supporting the catalyst component is coated with the first coat layer containing the HC adsorbent powder, the surface of the first coat layer is unpurified. A method for producing an exhaust gas purifying catalyst for an engine, which is coated with a second coating layer containing a catalytic metal for purifying exhaust gas components.

According to a third aspect of the present invention, an HC adsorbent powder that adsorbs HC and a solution containing a catalytic metal that purifies an unpurified exhaust gas component are mixed to form an HC carrying a catalytic metal. The method for producing an exhaust gas purifying catalyst for an engine is characterized in that after the adsorbent powder is formed, the catalyst metal-supported HC adsorbent powder is coated on the surface of a catalyst component-supporting carrier.

According to a fourth aspect of the present invention, a catalyst metal for purifying an unpurified exhaust gas component and cerium oxide are mixed to form cerium oxide carrying the catalyst metal, and then the catalyst metal is supported. A method for producing an exhaust gas purifying catalyst for an engine, comprising mixing cerium oxide with an HC adsorbent powder for adsorbing HC to form a slurry, and coating the slurry on the surface of a carrier for supporting a catalyst component. .

According to a fifth aspect of the present invention, a catalyst metal for purifying an unpurified exhaust gas component is mixed with a binder to form a catalyst metal-supported binder, and the catalyst metal-supported binder and the HC adsorbent powder. Is mixed to form a slurry, and then the slurry is coated on the surface of a catalyst component-supporting carrier to produce a catalyst for purifying exhaust gas of an engine.

According to a sixth aspect of the present invention, the surface of a carrier for supporting a catalyst component is coated with an HC adsorbent powder for adsorbing HC to form an HC adsorbent-supporting catalyst carrier, and then unpurified exhaust gas. A method for producing an exhaust gas purifying catalyst for an engine, in which a solution containing a catalytic metal for purifying a gas component and a cerium oxide powder are mixed to form a slurry, and the slurry is coated on the surface of an adsorption supporting catalyst carrier. Characterize.

According to a seventh aspect of the present invention, in addition to the structure of the second, third, fourth, fifth or sixth aspect of the present invention, an exhaust gas purifying catalyst for an engine, wherein the coating is a wash coat, is used. Is a manufacturing method of.

[0018]

According to the invention described in claim 1 of the present invention, since the structure is such that the catalyst metal is dispersedly arranged at least outside the HC adsorbent powder, the HC released from the HC adsorbent is released. Since it is always in contact with the catalyst metal, there is an effect that the HC purification rate can be sufficiently improved.

According to the second aspect of the present invention,
In this method, the surface of the carrier for supporting the catalyst component is coated with the first coat layer containing the HC adsorbent powder, and then the surface of the above-mentioned first coat layer is coated with the second coat layer containing the catalyst metal. Therefore, when the HC adsorbed by the HC adsorbent in the first coat layer is desorbed and goes out, it always passes through the second coat layer containing the catalytic metal. Therefore, there is an effect that the released HC can be sufficiently purified.

According to the invention of claim 3 of the present invention,
This is a method of coating a catalyst metal-supporting HC adsorbent powder in which a catalytic metal is thinly supported on the surface of the HC adsorbent powder on a catalyst component-supporting carrier. Therefore, when HC is desorbed and released, the HC adsorbent powder There is an effect that the released HC is burned and removed by the catalytic metal on the surface, and the HC purification rate can be sufficiently improved.

According to the invention of claim 4 of the present invention,
This is a method of coating a carrier for supporting a catalyst component with a slurry (slurry) in which cerium oxide carrying catalyst metal and HC adsorbent powder are mixed. Therefore, when HC is released, CeO ₂ (cerium oxide) is converted to O ₂ at the catalyst metal site. (oxygen)
Is supplied, and HC is burned and removed by an oxidation reaction, and there is an effect that the HC purification rate can be sufficiently improved.

According to the invention of claim 5 of the present invention,
A catalyst metal-supported binder having a catalyst metal disposed on a binder is formed, and the catalyst metal-supported binder and H
This is a method of coating the surface of the contact medium with the slurry after forming a slurry by mixing with the C adsorbent powder, so that it becomes easy to adjust the mixing of the HC adsorbent powder with the above-mentioned binder and improve the productivity. There is an effect that can be achieved.

According to the invention of claim 6 of the present invention,
The surface of the catalyst component supporting carrier is coated with HC adsorbent powder to form an adsorbent supporting catalyst carrier, and then a solution containing a catalytic metal and cerium oxide powder are mixed to form a slurry. This is a method of coating the surface of the above-mentioned adsorbent-supported catalyst carrier to form an inner layer containing the HC adsorbent powder and an outer layer containing the catalyst metal and cerium oxide. When the adsorbed HC desorbs and goes out, it always passes through the outer layer containing the catalytic metal and CeO ₂ (cerium oxide). As a result, the released HC can be burned and removed by the catalyst metal, and the oxidation reaction can be promoted by the oxygen supply from CeO ₂ described above, so that the HC can be burned and removed more satisfactorily. There is an effect that a sufficient improvement can be achieved.

According to the invention of claim 7 of the present invention,
Since the above coating was set to wash coat,
With this washcoat, the objects of claims 2 to 6 can be achieved.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. (First Embodiment) The drawings show an engine exhaust gas purifying catalyst and a method for manufacturing the same. In FIG. 1, an exhaust gas purifying apparatus 1 provided in an engine exhaust system is disposed at an underfloor position of a vehicle. At the same time, the exhaust gas purification device 1 is provided with joint flange portions 2 and 3 at both front and rear ends, and the front end side of the catalyst case 6 is connected to the exhaust gas inlet 4 via the cone portion 5, and the catalyst case 6 The rear end side is connected to the exhaust gas outlet 8 via the cone portion 7. Here, the above-mentioned exhaust gas inlet 4 is connected to the exhaust port of the engine via the exhaust passage, and the above-mentioned exhaust gas outlet 8 is connected to the muffler via the exhaust passage.

A three-way catalyst 9 for purifying unpurified exhaust gas components is disposed in the upstream side of the catalyst case 6 on the upstream side of the exhaust gas, and an HC that adsorbs HC is disposed on the downstream side of the exhaust gas downstream side. A composite catalyst 10 in which an adsorbent, a three-way catalyst for purifying unpurified exhaust gas components, and CeO ₂ (cerium oxide) are combined is arranged.

As shown in FIG. 2, the composite catalyst 10 on the latter-stage side has a cylindrical outer diameter and a honeycomb shape in the axial direction, and has a large number of pores 11. Moreover, the cross-sectional structure thereof is, as shown in FIG. 3, an MFI for adsorbing HC on the surface of the cordierite (Mg ₂ Al ₄ Si ₅ O ₁₈ ) honeycomb carrier 12 (catalyst component supporting carrier).
The first coat layer 13 containing the HC adsorbent powder composed of (Zeoray) powder is formed, and the second coat layer 14 containing the catalytic metal such as Pd (palladium) is formed on the outer surface of the first coat layer 13. In addition, the above-mentioned first coat layer 13 and the second coat layer 14 are mixed with Ce for the two-layer coat honeycomb.
O ₂ (cerium oxide) is supported by the impregnating means.

In this way, the catalyst metal (see the second coat layer 14) for purifying the unpurified exhaust gas component is dispersed and arranged outside the HC adsorbent powder (see the first coat layer 13). The HC in the exhaust gas is desorbed from the HC adsorbent after being trapped by the HC adsorbent, but the released HC always contacts the catalyst metal layer (see the second coat layer 14), so that the HC purification is performed. There is an effect that the rate can be sufficiently improved.

The manufacturing method of the composite catalyst 10 shown in FIG. 3 (the manufacturing method corresponding to claim 2) will be described in detail with reference to the process charts shown in FIGS. 4 and 5. First, the first step S1 of FIG.
Then, the surface of the cordierite honeycomb carrier 12 is wash-coated with the HC adsorbent powder to form the first coat layer 13.

The washcoat method described above is as shown in FIG. That is, as an HC adsorbent, a hydrogen ion exchange MFI powder (Cayvan ratio 10
0) (however, only hydrogen ions are shown in the following [Chemical formula 1]), hydrated alumina is used as a binder, and these are added to water at a weight ratio of 5: 1 and stirred, A slurry is formed (see first step S11). Here, the “Cayban ratio” means SiO ₂ / Al
_It means ₂ O ₃ .

[Chemical Formula 1] H ⁺ Next, the above-mentioned cordierite honeycomb carrier 12 (capacity: 1.3 liters) is dipped in the above slurry (second step S).
12), the cordierite honeycomb carrier 12 is pulled up from the slurry (third step S13).
Next, the slurry clogged in the pores 11 of the honeycomb carrier 12 is removed by air blowing (air blasting) (see the fourth step S14), and then dried to obtain the honeycomb carrier 1
2 is loaded with MFI powder (fifth step S1).
(See the first half of 5). By repeating this process from immersion to drying, the amount of MFI powder as the HC adsorbent carried is 150 g /
After the liter or more (here, the liter indicates the volume of the honeycomb), it is fired at about 500 ° C. for 2 hours to form the HC adsorbent-supporting honeycomb (see the latter half of the fifth step S15).

Next, in the second step S2 of FIG. 4, the second coat layer 1 containing the catalytic metal on the surface of the above-mentioned first coat layer 13 is formed.
Wash coat 4. That is, γ-Al ₂ O ₃ powder (gamma-alumina powder) (Pd: Al ₂ O ₃ = 1: weight ratio) in which Pd (palladium) was used as a catalyst metal and impregnated and supported with Pd (palladium) in advance. 5) and hydrated alumina as a binder are mixed with water in a weight ratio of 5: 1 to form a slurry, and the HC adsorbent-supporting honeycomb is dipped, pulled up, air blasted and dried in the slurry. After the treatment, the carried amount of Pd (palladium) becomes 6 g / liter, and then the firing is performed.

Next, in a third step S3 of FIG. 4, CeO ₂ (cerium oxide) is impregnated into the above-mentioned two-layer-coated honeycomb. That is, Ce (NO ₃ ) ₃ (cerium nitrate)
164 g was dissolved in 1 liter of water, and this cerium nitrate aqueous solution was used to impregnate the above-mentioned two-layer coated honeycomb with
Next, in the fourth step S4 of FIG. 4, the honeycomb impregnated with the cerium nitrate aqueous solution is fired to remove CeO ₂ (cerium oxide) by 5%.
A composite catalyst 10 supporting 0 g / liter was produced.

As described above, according to the manufacturing method shown in FIG.
A first coat layer 13 containing an HC adsorbent powder is wash-coated on the surface of the catalyst component-supporting carrier 12 (hereinafter, the catalyst component-supporting carrier is abbreviated as a catalyst carrier), and then the above-mentioned first coat layer 13 is formed. Since the second coat layer 14 containing the catalytic metal is wash-coated on the surface of
When the HC adsorbed by the HC adsorbent in the first coat layer 13 desorbs and goes out, it always passes through the second coat layer 14 containing the catalytic metal. Therefore, there is an effect that HC can be sufficiently purified for release. Further, since CeO ₂ (cerium oxide) is impregnated and supported on the above-mentioned two-layer coated honeycomb, the supply of O ₂ (oxygen) from CeO ₂ (cerium oxide) enables combustion and removal of HC by an oxidation reaction. Therefore, there is an effect that the HC purification rate can be sufficiently improved.

(Second Embodiment) Next, the manufacturing method of the second embodiment corresponding to claim 3 will be described in detail with reference to the process chart of FIG. First, in the first step S21 of FIG. 6, the HC adsorbent powder and the catalytic metal-containing aqueous solution (in this embodiment, an aqueous solution is used, but an organic solution may be used instead of the aqueous solution).

That is, hydrogen ion exchange MOR (mordenite) powder (Cayvan ratio 20) was used as the HC adsorbent.
00 g, and 120 g of a palladium nitrate aqueous solution (Pd, 4.4 wt%) as a catalyst metal-containing aqueous solution, and both are mixed and stirred in 100 g of H ₂ O (water).

Next, in the second step S22 of FIG. 6, while continuing stirring while heating the above aqueous solution using, for example, a hot plate as a heating means, the Pd (palladium) is dried on the HC adsorbent powder. A powder can be obtained. This method is generally called evaporation to dryness.

Next, in the third step S23 of FIG. 6, the above-mentioned catalyst metal-supported HC adsorbent powder is wash-coated on the honeycomb carrier. That is, the catalyst metal-supported HC adsorbent powder obtained by the above evaporation and drying means and hydrated alumina as a binder are mixed with water at a weight ratio of 5: 1 to form a slurry, The honeycomb carrier is wash-coated with the Pd-supporting MOR by repeating the dipping, pulling, air blasting and drying of the honeycomb carrier with respect to this slurry, and then firing. In addition, the total supported amount was 200 g / liter.

Next, in a fourth step S24 in FIG. 6, CeO ₂ (cerium oxide) is impregnated into the washcoated honeycomb carrier. That is, Ce (NO ₃ )
Dissolve 164 g of ₃ (cerium nitrate) in 1 liter of water,
The above honeycomb carrier was impregnated with this cerium nitrate aqueous solution, and then, in the fifth step S25 of FIG.
The honeycomb carrier after impregnating with an aqueous solution of O ₃ ) ₃ (cerium nitrate) was fired to produce a composite catalyst carrying 50 g of CeO ₂ (cerium oxide) per liter.

In this way, the catalyst metal-carrying HC adsorbent powder in which the catalytic metal (Pd in this case) is thinly supported on the surface of the HC adsorbent powder by the evaporation-drying means is wash-coated on the catalyst carrier. When HC is desorbed and released, there is an effect that the released HC is burned and removed by the catalyst metal on the surface of the HC adsorbent powder, and the HC purification rate can be sufficiently improved. Moreover, since CeO ₂ (cerium oxide) was impregnated and supported on the above wash-coated honeycomb carrier, HC was burned and removed by an oxidation reaction by supplying O ₂ (oxygen) from CeO ₂ (cerium oxide). Therefore, there is an effect that the HC purification rate can be more sufficiently improved.

Incidentally, instead of the evaporating and drying means, a spray drying method and an impregnation supporting method may be used.

(Third Embodiment) Next, a manufacturing method of a third embodiment corresponding to claim 4 will be described in detail with reference to the process chart of FIG. First, in the first step S31 of FIG. 7, the catalytic metal and Ce
Mix with O ₂ (cerium oxide). That is, cerium oxide powder is impregnated with an aqueous palladium nitrate solution, and then dried and calcined in the second step S32 of FIG. 7 to oxidize palladium on Pd: CeO ₂ = 1: 10 by weight. Form cerium.

Next, in the third step S33 in FIG. 7, the above-mentioned palladium-supported cerium oxide, hydrogen ion exchanged MFI (zeolite) powder as an HC adsorbent, and hydrated alumina as a binder are mixed at a weight ratio of 1: 5. Pour into water at a ratio of 1 and stir to form a slurry.

Next, in a fourth step S34 of FIG. 7, the honeycomb carrier is repeatedly immersed, pulled, air blasted and dried in the above-mentioned slurry, whereby Pd (palladium) and CeO ₂ (cerium oxide) are added to the honeycomb carrier. And MFI (zeolite) are wash-coated and then fired. In addition,
The total supported amount was 200 g / liter.

Thus, the catalytic metal-supported cerium oxide and H
Since this is a method of wash-coating the slurry in which the C adsorbent powder is mixed on the catalyst support, CeO ₂ (cerium oxide) is converted to O ₂ at the catalyst metal site when HC is released.
Since (oxygen) is supplied and HC is burned and removed by the oxidation reaction, there is an effect that the HC purification rate can be sufficiently improved.

(Fourth Embodiment) Next, the manufacturing method of the fourth embodiment corresponding to claim 5 will be described in detail with reference to the process chart of FIG. First, in a first step S41 of FIG. 8, a catalytic metal is mixed with a binder to form a catalytic metal-supporting binder. That is, hydrated alumina as a binder is impregnated with an aqueous palladium nitrate solution, and dried at 200 ° C. to form a palladium-supported binder powder.

Next, in the second step S42 of FIG. 8, the above-mentioned catalytic metal supporting binder and the HC adsorbent powder are mixed to form a slurry. That is, the above palladium-supported binder powder and H-type FAU (Y-type zeolite) as an HC adsorbent (Cayban ratio 6) are added to water at a weight ratio of 1: 5, and a slurry is formed by stirring treatment. .

Next, in the third step S43 in FIG. 8, the honeycomb carrier is repeatedly immersed, pulled, air blasted and dried in the above-mentioned slurry to form Pd and H type F on the honeycomb carrier.
After carrying 200 g / liter of AU and AU, it is fired.

Next, in a fourth step S44 of FIG. 8, CeO ₂ (cerium oxide) is impregnated into the washcoated honeycomb carrier. That is, Ce (NO ₃ )
Dissolve 164 g of ₃ (cerium nitrate) in 1 liter of water,
The above honeycomb carrier is impregnated with this cerium nitrate aqueous solution, and then the honeycomb carrier after impregnating the cerium nitrate aqueous solution is fired in a fifth step S45 of FIG. 8 to carry CeO ₂ (cerium oxide) at 50 g / liter. Composite catalysts were produced.

As described above, the catalyst metal-supporting binder in which the catalyst metal is supported on the binder is formed, and the catalyst metal-supporting binder and the HC adsorbent powder are mixed to form a slurry, and then the slurry is used as a catalyst carrier. Since it is a method of wash-coating the surface of the above, it is easy to adjust the mixture of the HC adsorbent powder with the above-mentioned binder, and there is an effect that the productivity can be improved.

(Fifth Embodiment) Next, the manufacturing method of the fifth embodiment corresponding to claim 6 will be described in detail with reference to the process chart of FIG. First, in the first step (S51) of FIG. 9, hydrogen ion exchanged FAU (Y-type zeolite) powder (Cayban ratio 30) was used as the HC adsorbent, and hydrated alumina was used as the binder, and both of them were FAU powder: hydrated alumina. = 5: 1
Is added to water in a weight ratio of and stirred to form a slurry.

Next, in a second step S52 of FIG. 9, after the cordierite honeycomb carrier (capacity: 1.3 liters) is immersed in the above slurry, the cordierite honeycomb carrier is pulled up from the slurry (third step). (See S53),
Next, the slurry clogged in the pores of the honeycomb carrier is removed by air blowing (air blasting) (see the fourth step S54), and then the drying (see the fifth step S55) treatment is performed, and F
After supporting the AU powder and repeating the above-mentioned treatment from dipping to drying until the amount of the FAU powder carried reaches 150 g / liter or more, it is fired at about 500 ° C. for 2 hours to form an HC adsorption supporting honeycomb carrier. (See the sixth step S56).

Next, in the seventh step S57 of FIG. 9, CeO
100 g of ₂ (cerium oxide) powder and a palladium nitrate aqueous solution (Pd 4.4 wt%) as an aqueous solution containing a catalytic metal.
320 g and 100 g of water are mixed and stirred in, for example, a beaker. Next, in the eighth step S58 of FIG. 9, when the aqueous solution is heated and stirring is continued using, for example, a hot plate as the heating means, the Pd-supporting Ce is evaporated by evaporation of water.
A dry powder of O ₂ can be obtained. This method is generally called evaporation to dryness.

Next, in a ninth step S59 in FIG. 9, the above-mentioned Pd
The supported CeO ₂ powder, Pd-supported CeO ₂ powder at a ratio of the hydrated alumina as a binder: hydrated alumina = 5:
Mix and agitate with water at a ratio of 1 to form a slurry.

Next, after dipping the above-mentioned HC adsorption supporting honeycomb carrier in this slurry (see the tenth step S60),
The above honeycomb carrier is pulled up from the above slurry (11th
(See step S61), then, after removing the slurry clogging the pores of the honeycomb carrier by air blowing (see twelfth step S62), a drying process is performed to carry the Pd-supporting CeO ₂ powder (thirteenth step S63). reference).

Next, after the above-mentioned treatment from dipping to drying was repeated until the amount of Pd-supported CeO ₂ powder carried reached 80 g / liter, calcination treatment (see the fourteenth step S64) was carried out to obtain HC adsorption powder. An inner layer containing FAU powder (see first coat layer 13 in FIG. 3) and an outer layer containing Pd palladium and CeO ₂ (cerium oxide) as catalyst metals (see second coat layer 14 in FIG. 3). ) And a composite catalyst 10 (see FIG. 3) were produced.

Thus, according to the manufacturing method shown in FIG.
The surface of the catalyst carrier was wash-coated with HC adsorbent powder to form an adsorbent-supported catalyst carrier, and then an aqueous solution containing a catalyst metal (in this case, palladium) was mixed with CeO ₂ (cerium oxide) powder. This is a method of forming a slurry and wash-coating the slurry on the surface of the catalyst carrier carrying the adsorbent to form the inner layer and the outer layer. Therefore, the HC adsorbed by the HC adsorbent in the inner layer is desorbed and removed. Be sure to use the catalyst metal and CeO ₂ (cerium oxide)
Since it passes through the outer layer having C, the released HC can be burned and removed by the catalyst metal, and the O ₂ supply from CeO ₂ described above accelerates the oxidation reaction to burn and remove HC even better. Therefore, there is an effect that the HC purification rate can be sufficiently improved.

(Sixth Embodiment) Next, the manufacturing method of the sixth embodiment corresponding to claim 6 will be described in detail with reference to the process chart of FIG. First, in the first step (S71) of FIG. 10, hydrogen ion exchanged FAU (Y-type zeolite) powder (Cayban ratio 80) was used as the HC adsorbent, and hydrated alumina was used as the binder. Both of them were FAU powder: hydrated alumina. =
Pour into water at a 5: 1 weight ratio and stir to form a slurry.

Next, in a second step S72 of FIG. 10, after the cordierite honeycomb carrier (capacity: 1.3 liters) is immersed in the above-mentioned slurry, the cordierite honeycomb carrier is pulled up from the slurry (third step). S73), and then the slurry clogging the pores of the honeycomb carrier is removed by air blowing (air blasting) (see the fourth step S74), followed by a drying (see the fifth step S75) treatment to obtain the FAU powder. Is carried out and the above-mentioned treatment from dipping to drying is repeated until the amount of FAU powder carried reaches 120 g / liter or more, followed by firing at about 500 ° C. for 2 hours to obtain HC.
An adsorption-supporting honeycomb carrier is formed (see the sixth step S76).

Next, in the seventh step S77 of FIG. 10, CeO ₂
CeO oxide powder, hydrated alumina as a binder, and a palladium sulfate aqueous solution (Pd 4.4 wt%) as a catalytic metal-containing aqueous solution were mixed in CeO in a weight ratio.
₂ (Cerium oxide) powder: hydrated alumina: palladium sulfate aqueous solution = 5: 1: 16 is added to water and stirred for about 1 hour to form a slurry.

Next, after the above-mentioned HC adsorption supporting honeycomb carrier is immersed in this slurry (see the eighth step S78), the above-mentioned honeycomb carrier is pulled up from the above-mentioned slurry (see the ninth step S79) and then blown with air. After removing the slurry clogged in the pores of the honeycomb carrier (see the tenth step S80), a drying process is performed to support the Pd-supporting CeO ₂ powder (see the eleventh step S81).

Next, after the above-mentioned treatments from dipping to drying are repeated until the amount of Pd-supported CeO ₂ powder carried reaches 70 g / liter, a firing treatment at about 500 ° C. for 2 hours (see twelfth step S82) is performed. And an inner layer containing FAU powder as HC adsorbing powder (see first coat layer 13 in FIG. 3)
And Pd palladium and CeO as catalytic metals
Composite catalyst 10 (see FIG. 3) having an outer layer containing ₂ (cerium oxide) (see second coat layer 14 in FIG. 3)
Was manufactured.

As described above, according to the manufacturing method shown in FIG. 10, the surface of the catalyst carrier is wash-coated with the HC adsorbent powder in the same manner as the manufacturing method shown in FIG. After formation, an aqueous solution containing a catalytic metal (palladium in this case) and CeO ₂ (cerium oxide)
This is a method in which the powder is mixed to form a slurry, and the slurry is wash-coated on the surface of the catalyst carrier carrying the adsorbent to form the inner layer and the outer layer.
When the HC adsorbed on the C adsorbent desorbs and goes out, it always passes through the outer layer containing the catalyst metal and CeO ₂ (cerium oxide), so that the released HC can be burned and removed by the catalyst metal, and the O ₂ supply from CeO _2, and by promoting the oxidation reaction, it can be more satisfactorily burn and remove HC, there is an effect that it is possible to sufficiently improve the HC purification rate.

The honeycombs manufactured by the above-mentioned respective examples have an HC adsorbing ability by the HC adsorbent and an oxygen adsorbing ability by CeO ₂ (cerium oxide), and the adsorbed HC
The catalyst metal can be smoothly reacted with oxygen for purification.

The above-described first embodiment shown in FIG. 4, second embodiment shown in FIG. 6, third embodiment shown in FIG. 7, fourth embodiment shown in FIG. 8, fifth embodiment shown in FIG. The composite catalyst (honeycomb) manufactured by the respective manufacturing methods of the sixth embodiment shown in FIG. 10 is mounted on the underfloor position of a V-type 6-cylinder 2500 cc engine, and is in agreement with the CVS4 mode (the FTP mode of the US standard running mode). ) In the actual vehicle running in Y1 mode, measure the amount of HC before and after the catalytic converter, then
The results of calculating the purification rate are shown in the following [Table 1] as Example 1, Example 2, Example 3, Example 4, Example 5, and Example 6, respectively. The actual vehicle running test is the data when only the composite catalyst is placed in the catalyst case 6 shown in FIG. 1 and the converter capacity is set to 1.3 liters. Further, Comparative Examples 1 and 2 show the results of the same vehicle running test as described above performed on a catalytic converter equipped with a normal three-way catalyst.

[0066]

[Table 1]

As is clear from the above [Table 1], each of Examples 1 to 6 has an excellent HC purification rate as compared with Comparative Examples 1 and 2. That is, in the composite catalysts of Examples 1 to 6, the HC in the exhaust gas in the cold state is once adsorbed by the HC adsorbent, and the HC released from the HC adsorbent after warming is contacted with the catalytic metal. By adopting a structure that is easy to perform, HC can be purified by combustion, so that an excellent HC purification rate as shown in Table 1 above can be achieved.

Particularly, as shown in the fifth and sixth embodiments,
When the layer of the HC adsorbent and the layer of the noble metal (palladium in this embodiment) as the catalyst metal are separately formed into the inner layer and the outer layer, the HC adsorbent and the noble metal react with each other under high temperature conditions to cause thermal deterioration. Since it can be prevented, there is an effect that the durability of the above-mentioned HC adsorbent and noble metal can be improved.

In the correspondence between the structure of the present invention and the above-described embodiment, the exhaust gas purifying catalyst of the present invention corresponds to the composite catalyst 10 of the embodiment, and hereinafter, similarly, the catalyst carrier is the honeycomb carrier 12. Correspondingly, the layer in which the HC adsorbent powder is dispersed and arranged corresponds to the first coat layer 13, the layer in which the catalyst metal is dispersed and arranged corresponds to the second coat layer 14, and the HC adsorbent is MFI ( Zeolite), MOR (mordenite),
Corresponding to H type FAU (Y type zeolite), the catalyst metal is
Although it corresponds to Pd (palladium), the present invention is not limited to the structures of the above-described embodiments.

For example, FER (ferrierite) or CHA (chabazite) may be used as the HC adsorbent in addition to the above elements, and Pt-Rh (platinum) is used as the catalyst metal in addition to Pd (palladium).・ Rhodium) and Pd-Rh
(Palladium / Rhodium) may be used, and the coating method may be a method using a spray in addition to the above washcoat.

[Brief description of drawings]

FIG. 1 is a sectional view of an exhaust gas purifying apparatus equipped with an engine exhaust gas purifying catalyst of the present invention.

FIG. 2 is a perspective view showing the composite catalyst of FIG. 1 in an extracted manner.

FIG. 3 is an enlarged cross-sectional view of a main part of FIG.

FIG. 4 is a process diagram showing a first embodiment of a method for producing an engine exhaust gas purifying catalyst according to the present invention.

FIG. 5 is a process drawing showing a washcoat treatment.

FIG. 6 is a process diagram showing a second embodiment of the method for producing the engine exhaust gas purifying catalyst of the present invention.

FIG. 7 is a process drawing showing a third embodiment of the method for producing an engine exhaust gas purifying catalyst of the present invention.

FIG. 8 is a process diagram showing a fourth embodiment of the method for producing an exhaust gas purifying catalyst for an engine of the present invention.

FIG. 9 is a process drawing showing a fifth embodiment of a method for producing an engine exhaust gas purification catalyst of the present invention.

FIG. 10 is a process drawing showing a sixth embodiment of the method for producing an engine exhaust gas purifying catalyst of the present invention.

FIG. 11 is an enlarged sectional view of a main part of a conventional exhaust gas purifying catalyst.

[Explanation of symbols]

 10 ... Composite catalyst 12 ... Honeycomb carrier (carrier for supporting catalyst component) 13 ... First coat layer 14 ... Second coat layer

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B01D 53/94 B01J 37/02 ZAB 7508-4G 301 C 7508-4G L 7508-4G B01D 53/36 103 Z 9342 -4G B01J 23/56 ZAB (72) Inventor Satoshi Ichikawa 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (7)

[Claims] 1. An exhaust gas purifying catalyst for an engine, wherein an HC adsorbent powder for adsorbing HC is dispersed and arranged on the surface of a carrier for supporting a catalyst component, the catalyst being unpurified at least outside the HC adsorbent powder. An exhaust gas purifying catalyst for an engine, in which a catalytic metal for purifying the exhaust gas component of is dispersedly arranged. 2. The surface of the carrier for supporting a catalyst component is coated with a first coat layer containing HC adsorbent powder that adsorbs HC, and then the surface of the first coat layer is purified of unpurified exhaust gas components. A method for producing an exhaust gas purifying catalyst for an engine, which is coated with a second coating layer containing a catalytic metal. 3. An HC adsorbent powder for adsorbing HC and a solution containing a catalytic metal for purifying an unpurified exhaust gas component are mixed to form an HC adsorbent powder carrying a catalytic metal, and then said. A method for producing a catalyst for purifying exhaust gas of an engine, wherein a surface of a carrier for supporting a catalyst component is coated with a powder of HC adsorbent carrying a catalyst metal. 4. Adsorption of HC by adsorbing HC on the cerium oxide supported on the catalyst metal after forming a cerium oxide supporting the catalyst metal by mixing a catalyst metal for cleaning the unpurified exhaust gas component and cerium oxide. A method for producing a catalyst for purifying exhaust gas of an engine, which comprises mixing agent powders to form a slurry and coating the slurry on the surface of a carrier for supporting a catalyst component. 5. A catalyst metal for purifying unpurified exhaust gas components is mixed with a binder to form a catalyst metal-supported binder, and the catalyst metal-supported binder is mixed with HC adsorbent powder for adsorbing HC. A method for producing an exhaust gas purifying catalyst for an engine, comprising forming a slurry and then coating the surface of a carrier for supporting a catalyst component with the slurry. 6. A solution containing a catalyst metal for purifying an unpurified exhaust gas component after forming an adsorbent-carrying catalyst carrier by coating the surface of a carrier for supporting a catalyst component with HC adsorbent powder for adsorbing HC. And a cerium oxide powder are mixed to form a slurry, and the slurry is coated on the surface of an adsorbent-supported catalyst carrier to produce an engine exhaust gas purifying catalyst. 7. The method for producing an exhaust gas purifying catalyst for an engine according to claim 2, 3, 4, 5 or 6, wherein the coating is a wash coat.