阅读说明：本技术 排气净化催化剂装置 (Exhaust gas purifying catalyst device ) 是由 岩田佳奈 伊藤实 大石隼辅 吉田健 垣花大 神谷谕 铃木宏昌 于 2020-05-11 设计创作，主要内容包括：一种排气净化催化剂装置100,具有基材10、担载于基材10的1种或2种以上的催化剂贵金属PGM和基材10的表面的涂层15,基材10具有由多孔质壁11区划出的多个孔室12,基材10及涂层15分别包含氧化铈-氧化锆复合氧化物粒子CZ。(An exhaust gas purification catalyst device 100 comprises a substrate 10, 1 or 2 or more kinds of catalytic noble metals PGM supported on the substrate 10, and a coating layer 15 on the surface of the substrate 10, wherein the substrate 10 has a plurality of cells 12 partitioned by porous walls 11, and each of the substrate 10 and the coating layer 15 contains ceria-zirconia composite oxide particles CZ.)

1. An exhaust gas purification catalyst device having:

a substrate;

1 or 2 or more kinds of catalytic noble metals supported on the base material; and

a coating on the surface of the substrate,

the substrate has a plurality of cells delimited by porous walls,

the substrate and the coating layer each contain ceria-zirconia composite oxide particles.

2. The exhaust gas purification catalyst device according to claim 1,

the plurality of cells of the substrate pass through from an upstream end to a downstream end of an exhaust stream.

3. The exhaust gas purification catalyst device according to claim 2,

the coating is present at a length of 80% or less of the length of the substrate from the downstream end of the exhaust stream of the substrate.

4. The exhaust gas purification catalyst device according to claim 1,

the plurality of cells of the substrate comprises:

an inlet-side orifice chamber in which an upstream end of the exhaust flow is open and a downstream end thereof is closed off; and

an outlet-side orifice chamber having an upstream end blocked and a downstream end opened,

the exhaust gas flowing into the inlet-side cell is thereby configured to pass through the porous wall and be discharged from the outlet-side cell.

5. The exhaust gas purification catalyst device according to claim 4,

the coating is present on the surface of the inlet-side cell within the substrate.

6. The exhaust gas purification catalyst device according to any one of claims 1 to 5,

the coating weight of the coating is 400g/L or less relative to the capacity 1L of the part corresponding to the area with the coating in the substrate.

7. The exhaust gas purification catalyst device according to any one of claims 1 to 6,

the coating comprises a catalytic noble metal.

8. The exhaust gas purification catalyst device according to claim 7,

the catalytic noble metal contained in the coating layer and the catalytic noble metal supported on the substrate are different kinds of catalytic noble metals.

9. The exhaust gas purification catalyst device according to claim 8,

the catalytic noble metal contained in the coating layer is rhodium, and the catalytic noble metal supported on the substrate is 1 or more selected from platinum and palladium.

10. The exhaust gas purification catalyst device according to any one of claims 1 to 9,

the noble metal 50 mass% supporting depth of 1 specific noble metal among the catalytic noble metals supported on the substrate is less than 50% of the distance from the surface of the porous wall to the center of the inside of the porous wall,

the noble metal 50 mass% loading depth is a depth at which 50 mass% of the specific noble metal is loaded based on the amount of the specific noble metal loaded from the surface of the porous wall to the center of the inside of the porous wall.

Technical Field

The present invention relates to an exhaust gas purifying catalyst device.

Background

Generally, in an exhaust gas purification catalyst device, a catalyst coating layer is formed on a honeycomb substrate made of cordierite or the like. The catalyst coating layer includes a carrier particle, a noble metal catalyst particle supported on the carrier particle, and a promoter particle. It is known that: as 1 type of the promoter particles, ceria-zirconia composite oxides having an oxygen storage capacity (OSC capacity) were used. The ceria-zirconia composite oxide has the following functions: in response to the environment (oxygen concentration) in the inflowing exhaust gas, oxygen is absorbed and released, changes in the exhaust gas environment are mitigated, and exhaust gas purification by the exhaust gas purification catalyst device is promoted.

In recent years, studies have been made to: the ceria-zirconia composite oxide particles as the promoter particles were used as 1 type of constituent material of the honeycomb substrate instead of being disposed in the catalyst coat layer. For example, patent document 1 discloses an exhaust gas purification catalyst device in which a honeycomb substrate contains ceria-zirconia composite oxide particles. In this exhaust gas purification catalyst device, the catalyst coating layer is not present, and the noble metal catalyst particles are directly supported on the honeycomb substrate by immersing the honeycomb substrate in a solution containing the noble metal.

Patent document 2 also discloses such a honeycomb substrate and an exhaust gas purification catalyst device using the same.

Further, as a coating method for forming a catalyst coating layer on a honeycomb substrate made of general cordierite or the like, methods described in patent documents 3 and 4 are known.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2015-85241

Patent document 2: japanese patent laid-open publication No. 2015-77543

Patent document 3: japanese laid-open patent publication No. 2008-302304

Patent document 4: international publication No. 2010/114132

Disclosure of Invention

The exhaust gas purifying catalyst devices disclosed in patent documents 1 and 2 have a small heat capacity because they do not have a catalyst coating layer, and are easy to raise the temperature of the honeycomb substrate, and therefore, high warm-up performance (warm-up performance) can be obtained. In addition, since the substrate contains the ceria-zirconia composite oxide particles, it is expected that the substrate itself exhibits OSC capability.

However, according to the studies of the present inventors, it was clarified that: in some cases, the desired OSC performance cannot be exhibited in these exhaust gas purification catalyst devices.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an exhaust gas purification catalyst device capable of exhibiting a high OSC, and preferably also having a high preheating performance.

The present invention is as follows.

Mode 1

An exhaust gas purification catalyst device having:

a substrate;

1 or 2 or more kinds of catalytic noble metals supported on the base material; and

a coating layer on the surface of the above-mentioned base material,

the substrate has a plurality of cells defined by porous walls,

the substrate and the coating layer each contain ceria-zirconia composite oxide particles.

Mode 2

The exhaust gas purification catalyst device according to mode 1, wherein the plurality of cells of the base material penetrate from an upstream end to a downstream end of an exhaust gas flow.

Mode 3

The exhaust gas purification catalyst device according to mode 2, wherein the coating layer is present in a length of 80% or less of the length of the substrate from the downstream end of the substrate in the exhaust gas flow.

Mode 4

According to the exhaust gas purification catalyst device described in the mode 1,

the plurality of cells of the substrate comprise:

an inlet-side orifice chamber in which an upstream end of the exhaust flow is open and a downstream end thereof is closed off; and

an outlet-side orifice chamber having an upstream end blocked and a downstream end opened,

the exhaust gas flowing into the inlet-side cell is thereby discharged from the outlet-side cell through the porous wall.

Mode 5

The exhaust gas purification catalyst device according to mode 4, wherein the coating layer is present on a surface of the inlet-side cell in the base material.

Mode 6

The exhaust gas purification catalyst device according to any one of aspects 1 to 5, wherein an amount of the coating layer applied is 400g/L or less with respect to a capacity 1L of a portion of the base material corresponding to a region having the coating layer.

Mode 7

The exhaust gas purification catalyst device according to any one of aspects 1 to 6, wherein the coating layer contains a catalytic noble metal.

Mode 8

The exhaust gas purification catalyst device according to mode 7, wherein the catalytic noble metal contained in the coating layer and the catalytic noble metal carried on the substrate are different kinds of catalytic noble metals.

Mode 9

The exhaust gas purification catalyst device according to mode 8, wherein the catalytic precious metal contained in the coating layer is rhodium, and the catalytic precious metal supported on the substrate is 1 or more selected from platinum and palladium.

Mode 10

The exhaust gas purification catalyst device according to any one of aspects 1 to 9,

the noble metal 50 mass% loading depth of the specific noble metal of 1 kind of the catalytic noble metals loaded on the substrate is less than 50% of the distance from the surface of the porous wall to the center of the inside of the porous wall,

the noble metal loading depth of 50 mass% is a depth at which 50 mass% of the specific noble metal is loaded based on the amount of the specific noble metal loaded from the surface of the porous wall to the center of the inside of the porous wall.

The exhaust gas purification catalyst device of the present invention can reliably exhibit a desired OSC performance. In a preferred embodiment of the present invention, the desired OSC capacity is exhibited, and also a high degree of preheating performance is provided.

Drawings

Fig. 1 is a schematic sectional view for explaining a structure of an example of an exhaust gas purification catalyst device according to the present invention.

Fig. 2 is a schematic sectional view for explaining the structure of another example of the exhaust gas purification catalyst device of the present invention.

Fig. 3 is an enlarged view of a portion surrounded by a broken line in fig. 2.

Fig. 4(a), 4(b), and 4(c) are schematic sectional views showing the configurations of the exhaust gas purification catalyst devices obtained in comparative example 1, and example 2, respectively.

FIG. 5 shows an exhaust gas purifying catalyst according to an embodimentEvaluation of OSC capability of the device showed CO at a test temperature of 400 ℃₂Graph of the temporal change of the discharge amount. FIG. 5(a) shows CO in the entire exhaust gas purifying catalyst device₂A map of discharge amounts; FIG. 5(b) shows CO in the exhaust gas purifying catalyst device₂The discharge amount is separated into a base material contribution amount and a coating layer contribution amount.

FIG. 6 is a graph showing CO at a test temperature of 500 ℃ in the evaluation of the OSC capability of the exhaust gas purification catalyst device of the example₂Graph of the temporal change of the discharge amount. FIG. 6(a) shows CO in the entire exhaust gas purification catalyst device₂A map of discharge amounts; FIG. 6(b) shows CO in the exhaust gas purifying catalyst device₂The discharge amount is separated into a base material contribution amount and a coating layer contribution amount.

Detailed Description

An exhaust gas purification catalyst device according to the present invention includes:

a substrate;

a catalytic noble metal supported on a substrate; and

a coating layer on the surface of the base material,

the substrate has a plurality of cells defined by porous walls,

the substrate and the coating layer each contain ceria-zirconia composite oxide particles.

The present inventors have studied the reason why, when ceria-zirconia composite oxide particles are used as 1 type of constituent material of a substrate in an exhaust gas purification catalyst device, the desired OSC ability of the substrate may not be exhibited. As a result, it is thought that: in such an exhaust gas purification catalyst device, the OSC which the ceria-zirconia composite oxide particles originally have is not decreased, but the response (response) of oxygen absorption and release when the environment (oxygen concentration) of the exhaust gas flowing into the device changes is slow. According to this idea, although the rate of absorption and release of oxygen is slowed, the amount of oxygen occlusion and release is not impaired, and the potential OSC is maintained.

It is presumed that the slow response of oxygen absorption and release is caused by, for example: since the constituent material of the base material is sintered at a high temperature in the process of manufacturing the base material, 1 or more items such as a reduction in specific surface area, a change in crystal structure, and a solid solution with other constituent materials may occur.

In view of the above, in the exhaust gas purification catalyst device of the present invention, ceria-zirconia composite oxide particles are used as 1 type of constituent material of the base material, and a coating layer containing ceria-zirconia composite oxide particles is provided on the surface of the base material to assist the OSC ability of the base material itself.

According to this configuration, when the environment of the exhaust gas flowing into the exhaust gas purification catalyst device changes, the ceria-zirconia composite oxide particles in the coating layer conform to and absorb or release oxygen. If this environment continues, the potential OSC of the ceria-zirconia composite oxide particles in the base material functions, and an excessive amount of oxygen is absorbed during exhaust gas purification, or an amount of oxygen necessary for exhaust gas purification is released, and exhaust gas purification by the exhaust gas purification catalyst device is promoted.

Hereinafter, each element of the exhaust gas purification catalyst device of the present invention will be described in order.

< substrate >

The substrate in the exhaust gas purification catalyst device of the present invention has a plurality of cells partitioned by porous walls, and contains ceria-zirconia composite oxide particles.

The substrate in the exhaust gas purification catalyst device of the present invention has a plurality of cells partitioned by porous walls. The substrate may be a straight flow type honeycomb substrate in which the plurality of cells penetrate in the longitudinal direction of the substrate from the upstream end to the downstream end of the exhaust gas flow, or may be: the plurality of cells include an inlet-side cell in which an upstream end of the exhaust gas flow is open and a downstream end thereof is closed, and an outlet-side cell in which an upstream end of the exhaust gas flow is closed and a downstream end thereof is open.

The substrate contains ceria-zirconia composite oxide particles. The ceria-zirconia composite oxide particles may be particles of a solid solution of ceria and zirconia, and the solid solution may contain a rare earth element (for example, lanthanum (La), yttrium (Y), or the like) in addition to ceria and zirconia.

The base material may be composed of only the ceria-zirconia composite oxide particles, or may contain other components in addition to the ceria-zirconia composite oxide particles. The other component may be, for example, inorganic oxide particles other than the ceria-zirconia composite oxide particles, a binder, or the like.

The inorganic oxide particles other than the ceria-zirconia composite oxide particles may be, for example, oxide particles containing 1 or 2 or more elements selected from aluminum, silicon, zirconium, titanium, tungsten, and the like, and particularly may be alumina particles.

The binder may be an inorganic binder, and may be, for example, alumina sol, titania sol, or the like.

The proportion of the ceria-zirconia composite oxide particles contained in the substrate may be, for example, 20 mass% or more, 30 mass% or more, 40 mass% or more, 50 mass% or more, 60 mass% or more, or 70 mass% or more, or 95 mass% or less, 90 mass% or less, 80 mass% or less, 70 mass% or less, 60 mass% or less, 50 mass% or less, or 40 mass% or less, as the proportion of the mass of the ceria-zirconia composite oxide particles with respect to the total mass of the substrate.

The capacity of the base material may be appropriately set according to the exhaust gas amount of the internal combustion engine to be used, but may be, for example, 500mL or more, 600mL or more, 800mL or more, 1000mL or more, or 1500mL or more, and may be, for example, 3000mL or less, 2500mL or less, 2000mL or less, 1500mL or less, or 1200mL or less.

< catalyst noble Metal >

The exhaust gas purifying catalyst device of the present invention has 1 or 2 or more kinds of catalytic noble metals supported on a substrate.

The catalytic noble metal may be, for example, a platinum group noble metal, and particularly may be 1, 2 or 3 selected from platinum, palladium and rhodium.

In the exhaust gas purification catalyst device of the present invention, when the catalytic noble metal contains platinum, the amount of platinum may be, for example, 0.01g/L or more, 0.02g/L or more, 0.05g/L or more, 0.07g/L or more, or 0.08g/L or more, as the metal platinum equivalent mass per 1L of the substrate capacity, or may be, for example, 1.0g/L or less, 0.8g/L or less, 0.6g/L or less, 0.4g/L or less, or 0.2g/L or less.

When the catalytic noble metal contains palladium, the amount of palladium may be, for example, 0.5g/L or more, 1.0g/L or more, 1.5g/L or more, 2.0g/L or more, 2.5g/L or more, or 3.0g/L or more, as the metal palladium equivalent mass per 1L of the substrate capacity, or may be, for example, 10.0g/L or less, 8.0g/L or less, 6.0g/L or less, 5.0g/L or less, or 4.0g/L or less.

When the catalytic noble metal contains rhodium, the amount of rhodium may be, for example, 0.01g/L or more, 0.05g/L or more, 0.10g/L or more, or 0.15g/L or more, as the mass in terms of metal rhodium per 1L of the substrate capacity, or may be, for example, 0.50g/L or less, 0.40g/L or less, 0.35g/L or less, or 0.30g/L or less.

In the exhaust gas purifying catalyst device of the present invention, as the catalytic noble metal, platinum or palladium may be contained, or: platinum or palladium; and rhodium.

In the exhaust gas purifying catalyst device of the present invention, the catalytic precious metal can be uniformly supported in the thickness direction of the porous wall of the substrate. However, the noble metal 50 mass% supporting depth of the specific noble metal which is 1 kind of the catalytic noble metal may be less than 50% of the distance from the surface of the porous wall to the center of the inside of the porous wall. Here, the noble metal loading depth of 50 mass% is a depth at which 50 mass% of the specific noble metal is loaded based on the amount of the specific noble metal loaded from the surface of the porous wall to the center of the inside of the porous wall. The noble metal loading depth of 50 mass% can be measured by Electron Probe Microanalyzer (EPMA) analysis.

This requirement represents: at least 1 kind of the catalytic noble metal is locally present in the vicinity of the surface of the porous wall of the substrate and supported. As a result, the exhaust gas flowing into the exhaust gas purification catalyst device of the present invention and the specific precious metal are likely to come into contact with each other, and the efficiency of exhaust gas purification by the specific precious metal can be expected to be improved.

From the viewpoint of locally causing more specific precious metal to be present in the vicinity of the surface of the porous wall and improving the efficiency of exhaust gas purification by the specific precious metal, it is considered that the smaller the precious metal 50 mass% loading depth, the better. On the other hand, from the viewpoint of allowing the specific noble metal to enjoy the OSC of the ceria-zirconia composite oxide particles present inside the porous wall, it is not preferable that the noble metal is supported at an excessively shallow depth of 50 mass%.

Therefore, the noble metal 50 mass% loading depth of the specific noble metal should be set within a range in which the above requirements are balanced. From this viewpoint, the noble metal 50 mass% loading depth of the specific noble metal is 12% or more of the distance from the surface of the porous wall to the center of the interior of the porous wall, or may be, for example, 14% or more, 16% or more, 17% or more, 18% or more, or 20% or more, or 40% or less, or may be, for example, 35% or less, 30% or less, 25% or less, or 20% or less.

The particular noble metal may be platinum, palladium or rhodium, and may further be platinum or palladium. In the exhaust gas purifying catalyst device of the present invention, particularly preferred are the following cases: the specific noble metal is platinum or palladium, and the noble metal contains rhodium as a catalyst other than the specific noble metal.

< coating layer >

The exhaust gas purifying catalyst device of the present invention has a coating layer on the surface of a base material. The coating layer is a coating layer containing ceria-zirconia composite oxide particles.

According to a preferred embodiment of the present invention, the coating layer in the exhaust gas purification catalyst device according to the present invention may be a coating layer formed without a sintering process by high-temperature firing. The coating layer may specifically be a coating layer formed without being subjected to heat treatment at a temperature of, for example, more than 900 ℃, more than 800 ℃, more than 700 ℃, or more than 600 ℃. Such a coating layer has a function of accelerating the response of oxygen absorption and release when the environment (oxygen concentration) of exhaust gas flowing into the device changes, and assisting the OSC ability of the substrate.

The coating layer contains ceria-zirconia composite oxide particles in order to assist the OSC ability of the substrate. As for the ceria-zirconia composite oxide particles, the description as described above with respect to the ceria-zirconia composite oxide particles contained in the base material can be applied as they are.

The coating layer may be composed of only ceria-zirconia composite oxide particles, or may contain other components. The other components may be, for example, inorganic oxide particles other than the ceria-zirconia composite oxide particles, a catalyst noble metal, a binder, and the like.

The inorganic oxide particles other than the ceria-zirconia composite oxide particles may be, for example, oxide particles containing 1 or 2 or more elements selected from aluminum, silicon, zirconium, titanium, tungsten, and the like, and particularly may be alumina particles.

The coating may also comprise a catalytic noble metal. The catalytic noble metal may be, for example, a platinum group noble metal, and may be, in particular, 1, 2, or 3 selected from platinum, palladium, and rhodium.

When the coating layer contains platinum, the amount of platinum may be, for example, 0.01g/L or more, 0.02g/L or more, 0.05g/L or more, 0.07g/L or more, or 0.08g/L or more, as a metal platinum equivalent mass of 1L in capacity relative to the portion of the base material corresponding to the region having the coating layer, or may be, for example, 1.0g/L or less, 0.8g/L or less, 0.6g/L or less, 0.4g/L or less, or 0.2g/L or less.

When the coating layer contains palladium, the amount of palladium may be, for example, 0.5g/L or more, 1.0g/L or more, 1.5g/L or more, 2.0g/L or more, 2.5g/L or more, or 3.0g/L or more, as a mass in terms of metallic palladium, relative to a capacity of 1L of a portion of the substrate corresponding to the region having the coating layer, and may be, for example, 10.0g/L or less, 8.0g/L or less, 6.0g/L or less, 5.0g/L or less, or 4.0g/L or less.

When the coating layer contains rhodium, the amount of rhodium may be, for example, 0.01g/L or more, 0.05g/L or more, 0.10g/L or more, or 0.15g/L or more, as a mass in terms of metal rhodium in a volume of 1L of a portion of the substrate corresponding to the region having the coating layer, or may be, for example, 0.50g/L or less, 0.40g/L or less, 0.35g/L or less, or 0.30g/L or less.

The catalytic noble metal contained in the coating layer may be the same type of catalytic noble metal as the catalytic noble metal supported on the substrate, or may be a different type of catalytic noble metal. For example, it is possible to exemplify: the catalytic noble metal contained in the coating layer is rhodium, and the catalytic noble metal supported on the substrate may be 1 or more selected from platinum and palladium.

The catalytic noble metal contained in the coating layer may be supported by 1 or more selected from the group consisting of ceria-zirconia composite oxide particles and inorganic oxide particles other than ceria-zirconia composite oxide particles.

The binder contained in the coating layer may be an inorganic binder, and may be, for example, alumina sol, titania sol, or the like.

The proportion of the ceria-zirconia composite oxide particles contained in the substrate may be, for example, 20 mass% or more, 30 mass% or more, 40 mass% or more, 50 mass% or more, 60 mass% or more, or 70 mass% or more, and may be 100 mass% or less, 95 mass% or less, 90 mass% or less, 80 mass% or less, 70 mass% or less, 60 mass% or less, 50 mass% or less, or 40 mass% or less, as the proportion of the mass of the ceria-zirconia composite oxide particles with respect to the total mass of the substrate.

The composition of the coating may be the same as or different from the composition of the substrate.

The term "coating layer on the surface of the substrate" is a concept including both the case where the coating layer is present on the surface of the substrate and the case where the coating layer is present in the substrate. That is, the coating layer may be present on the surface of the substrate without penetrating into the porous walls of the substrate, may be present in the substrate while penetrating into the porous walls of the substrate, or may be present on the surface of the substrate or in the substrate. The coating layer may be present in plural, and these plural coating layers may be present in the same position on the substrate or may be present in different positions on the substrate in a layered manner.

In order not to impair the high preheating performance of the substrate as much as possible, it is preferable that: the coating is stopped at the necessary minimum amount and length, and at least a portion of the substrate is free of coating.

From this viewpoint, in the case of a straight flow type base material, it is preferable that: the exhaust gas purification catalyst device is ensured in preheating performance without providing a coating layer on the upstream side of the exhaust gas flow which is first in contact with high-temperature exhaust gas among substrates, and in addition, the coating layer is provided on the downstream side, and efficient exhaust gas purification is achieved by using the OSC ability assisted by the coating layer.

In this case, the coating may be present at a length of, for example, 80% or less, 70% or less, 60% or less, 50% or less, or 40% or less of the length of the substrate from the downstream end of the exhaust stream of the substrate. On the other hand, in order to effectively exhibit the effect of the coating layer, the coating layer may be present at a length of, for example, 10% or more, 20% or more, 30% or more, 40% or more, or 50% or more of the length of the substrate from the downstream end of the exhaust flow of the substrate.

The coating layer on the downstream side of the flow-through type substrate may be present on the substrate or may be present in the substrate.

On the other hand, in the case of a wall-flow type substrate, it is effective to make a coating layer exist on the surface of the inlet-side cells having a high probability of contact with the inflowing exhaust gas among the substrates. In this case, the coating layer may be present at a length of, for example, 90% or less, 80% or less, 70% or less, 60% or less, or 50% or less of the length of the substrate from the upstream end of the exhaust flow of the substrate, and may be present at a length of, for example, 40% or more, 45% or more, 50% or more, 55% or more, or 60% or more.

The coating of the inlet-side cells of the wall-flow type substrate may be present on the substrate or may be present within the substrate.

The coating amount of the coating layer may be 400g/L or less, 350g/L or less, 300g/L or less, 250g/L or less, or 200g/L or less with respect to 1L of the capacity of the portion of the substrate corresponding to the region having the coating layer, from the viewpoint of not impairing the preheating property of the substrate as much as possible. On the other hand, from the viewpoint of effectively enjoying the effect of the coating layer, the coating amount of the coating layer may be 50g/L or more, 75g/L or more, 100g/L or more, 125g/L or more, 150g/L or more, or 175g/L or more with respect to the capacity 1L of the portion of the substrate corresponding to the region having the coating layer.

< embodiment of exhaust gas purifying catalyst device >

Hereinafter, an embodiment of an exhaust gas purification catalyst device according to the present invention will be described with reference to the drawings. However, the exhaust gas purification catalyst device of the present invention is not limited to the embodiments described below.

Fig. 1 is a schematic sectional view for explaining a structure of an example of an exhaust gas purification catalyst device according to the present invention.

The exhaust gas purification catalyst device (100) of fig. 1 has a substrate (10) and a coating layer (15) on the surface of the substrate (10). The base material (10) has cells (12) defined by porous walls (11), and contains cerium oxide-zirconium oxide composite oxide particles (CZ).

The substrate (10) is a straight flow type honeycomb substrate in which cells (12) penetrate in the longitudinal direction of the substrate (10) from the upstream end to the downstream end of the exhaust gas flow. The catalyst noble metal (PGM) is uniformly supported on the porous walls (11) of the substrate (10) in the thickness direction.

The coating layer (15) of the exhaust gas purification catalyst device (100) is formed on the surface of the porous wall (11) of the substrate (10) and has the same length as the substrate (10) from the upstream end of the substrate (10) in the exhaust gas flow. The coating layer (15) contains ceria-zirconia composite oxide particles (CZ), and may further contain a catalytic noble metal (PGM).

Fig. 2 is a schematic sectional view for explaining the structure of another example of the exhaust gas purification catalyst device of the present invention. Fig. 3 is an enlarged view of a portion surrounded by a broken line in fig. 2.

The exhaust gas purification catalyst device (200) of fig. 2 has a substrate (20) and a coating layer (25) on the surface of the substrate (20). The substrate (20) in the exhaust gas purification catalyst device (200) of fig. 2 is a straight flow type honeycomb substrate having cells (22) partitioned by porous walls (21), containing ceria-zirconia composite oxide particles (CZ), and having cells (12) penetrating in the longitudinal direction of the substrate (20) from the upstream end to the downstream end of the exhaust gas flow, as in the case of the exhaust gas purification catalyst device (100) of fig. 1.

However, as shown in fig. 3, in the exhaust gas purification catalyst device (200), the catalytic precious metal (PGM) is locally present in the vicinity of the surface of the porous wall (21) of the substrate (20) and supported thereon.

The coating layer (25) of the exhaust gas purification catalyst device (200) is formed on the surface of the porous wall (21) of the substrate (20), and has a length of about half of the substrate (20) from the exhaust gas flow downstream end of the substrate (20). The coating layer (25) contains ceria-zirconia composite oxide particles (CZ), and may further contain a catalytic noble metal (PGM).

Method for manufacturing exhaust gas purification catalyst device

The exhaust gas purifying catalyst device of the present invention can be produced, for example, by a method (production method 1) for producing an exhaust gas purifying catalyst device having a substrate, 1 or 2 or more kinds of catalytic noble metals supported on the substrate, and a coating layer on the surface of the substrate,

as the substrate, a substrate having a plurality of cells defined by porous walls and containing ceria-zirconia composite oxide particles is used,

the following steps (1) and (2) were performed in this order.

(1) Loading a catalyst noble metal on a base material; and

(2) a coating layer is formed on the surface of the base material on which the catalytic noble metal is supported.

The substrate may be appropriately selected and used according to the desired substrate in the exhaust gas purification catalyst device. Therefore, it may be a direct flow type or wall flow type substrate having a plurality of cells partitioned by porous walls and containing ceria-zirconia composite oxide particles.

In the step (1), the catalytic noble metal is supported on the substrate. Here, a method of relatively uniformly supporting the catalytic noble metal in the thickness direction of the porous wall of the substrate and a method of supporting the catalytic noble metal locally in the vicinity of the surface of the substrate will be described in order.

The relatively uniform loading of the catalytic noble metal in the thickness direction of the porous wall of the substrate can be carried out, for example, by the following method: the base material is immersed in a coating liquid for supporting a catalyst noble metal containing a precursor of the catalyst noble metal, and then baked. According to this method, the precursor of the catalytic noble metal permeates into the inside of the porous wall of the base material, and is burned at the permeated position to be converted into the catalytic noble metal, so that the catalytic noble metal is supported over a wide depth range up to the inside of the porous wall of the base material.

The coating liquid for supporting a catalyst noble metal used herein may be, for example, an aqueous solution containing at least a precursor of the catalyst noble metal. The coating liquid for supporting a catalyst precious metal may further contain a thickener or the like as necessary. However, the coating liquid for supporting a catalyst noble metal may not contain inorganic oxide support particles.

The precursor of the catalyst noble metal may be, for example, a strong acid salt of the catalyst noble metal, and particularly may be a nitrate, a sulfate, or the like of the catalyst noble metal.

As the thickener, the same thickener as that contained in the coating liquid for forming a catalyst noble metal surface into a localized state, which will be described later, may be used after the content thereof is appropriately adjusted.

By appropriately changing the impregnation conditions, the degree of permeation of the precursor of the catalytic noble metal into the porous walls of the base material can be adjusted. Examples of the dipping conditions include the viscosity and temperature of the coating liquid, dipping time, dipping pressure, and the like.

The substrate is immersed in the coating liquid for supporting a catalytic noble metal and then fired, whereby a precursor of the catalytic noble metal is converted into the catalytic noble metal and supported.

After the dipping and before the firing, in order to remove the excess coating liquid from the base material, blowing with a compressed gas (compressed air), vacuum suction, centrifugal removal, and the like may be performed. Further, the substrate can be dried. These operations may be performed according to conventional methods. The firing may be performed under appropriate conditions, and examples thereof include conditions of 400 ℃ to 1000 ℃, 30 minutes to 12 hours.

The supporting of the catalytic noble metal locally in the vicinity of the surface of the substrate can be carried out, for example, by the following method: a coating liquid for localized formation of a surface of a catalyst noble metal, which contains a thickener and a precursor of 1 specific noble metal among the catalyst noble metals, is applied to a substrate, followed by firing. According to this method, the precursor of the catalytic noble metal is not permeated into the porous wall of the substrate in the vicinity of the surface of the porous wall, and is burned at the permeation position to be converted into the catalytic noble metal, so that the catalytic noble metal is supported in the vicinity of the surface of the porous wall of the substrate.

The coating liquid for localized formation of the catalyst noble metal surface may be, for example, an aqueous solution containing at least a precursor of the catalyst noble metal and a thickener. The coating liquid for localized formation of the surface of the catalytic noble metal may not contain the inorganic oxide support particles.

The precursor of the catalyst noble metal contained in the coating liquid for localized formation of the surface of the catalyst noble metal can be appropriately selected from the precursors described above as the precursors contained in the coating liquid for supporting the catalyst noble metal, and used.

The thickener may be, for example, a water-soluble polymer, a cellulose derivative, a polysaccharide, or the like. The water-soluble polymer may be, for example, polyvinyl alcohol, ethylene glycol, propylene glycol, or the like. The cellulose derivative may be, for example, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, or the like. Examples of the polysaccharide include pectin (pectin), xanthan gum (xanthan gum), guar gum (guar gum), and the like.

The coating liquid for localized formation of the catalytic noble metal surface has a viscosity increased by the blending of the thickener, and the degree of penetration into the porous wall when applied to the substrate can be adjusted, whereby the desired noble metal loading depth of 50 mass% can be achieved for the catalytic noble metal.

Shear rate 380s of coating liquid for localized formation of catalytic noble metal surface^-1The lower viscosity may be, for example, 10mPa or more, 50mPa or more, or 100mPa or more, and may be, for example, 400mPa or less, 300mPa or less, or 200mPa or less. About 380s at shear rate^-1The viscosity of the coating liquid below can be measured at 25 ℃ with a cone-plate type viscometer (e.g., a model name "TV-33 type viscometer" manufactured by eastern industries, ltd.) using a cone-plate type cone of 1 ° 34' × R24, with the rotation speed being changed in the range of 1 to 100 rpm.

The coating liquid for localized formation of the catalytic noble metal surface on the substrate can be applied by, for example, any of the following methods:

the coating liquid for localized presence of a catalyst noble metal surface is supplied from the opening side of one end of the substrate, and then the supplied coating liquid for localized presence of a catalyst noble metal surface is sucked from the substrate opening side opposite to the side from which the coating liquid is supplied (coating method 1),

alternatively, a coating liquid for localized surface presence of a catalytic noble metal is supplied from the opening side of one end of the substrate, and then the supplied coating liquid for localized surface presence of a catalytic noble metal is pumped from the opening side of the substrate on the supply side of the coating liquid (coating method 2).

The precursor of the catalytic noble metal is converted into the catalytic noble metal and supported by the catalytic noble metal by applying a coating liquid for localized surface formation of the catalytic noble metal on the substrate and then firing the coating liquid. After coating and before firing, the coating liquid may be removed, and the substrate may be dried. These operations can be performed in the same manner as in the case where the catalytic noble metal is uniformly supported in the thickness direction of the porous wall of the substrate.

In the step (2), the coating layer is formed on the surface of the base material on which the catalytic noble metal is supported as described above.

The formation of the coating layer in the step (2) can be performed, for example, by the following method: the coating liquid for forming a coating layer is applied to a substrate, followed by firing.

The coating liquid for forming a coating layer may contain, for example, at least ceria-zirconia composite oxide particles, and may further contain inorganic oxide particles other than ceria-zirconia composite oxide particles, a thickener, a binder, a precursor of a catalyst noble metal, and the like, depending on the process of the target exhaust gas purification catalyst device.

As for the ceria-zirconia composite oxide particles and the inorganic oxide particles other than the ceria-zirconia composite oxide particles contained in the coating liquid for forming a coating layer, the description described above with respect to the ceria-zirconia composite oxide particles and the inorganic oxide particles other than the ceria-zirconia composite oxide particles contained in the base material can be applied as they are.

The thickener, the binder, and the precursor of the catalytic noble metal may be used by appropriately adjusting the content of each component in the same kind as the component in the coating liquid for supporting the catalytic noble metal or the coating liquid for locally forming the surface of the catalytic noble metal.

The kind and content of the ceria-zirconia composite oxide particles, the inorganic oxide particles other than the ceria-zirconia composite oxide particles, and the precursor of the catalytic noble metal can be selected and adjusted according to the composition of the coating layer of the target exhaust gas purification catalyst device.

The coating liquid for forming a coating layer can be applied to the substrate by, for example, the 1 st coating method or the 2 nd coating method similar to the coating of the coating liquid for forming a catalyst noble metal surface into a localized state.

Next, the coating film is dried as necessary and then baked, thereby forming a coating layer on the substrate. The drying and firing may be carried out by a conventional method. However, in order to avoid that the ceria-zirconia composite oxide particles in the coating layer are sintered at a high temperature and deteriorate the rapidity of response of oxygen absorption and release, the firing may be performed at a temperature of, for example, 700 ℃ or lower, 650 ℃ or lower, 600 ℃ or lower, 550 ℃ or lower, or 500 ℃ or lower. In order to obtain the effect of firing effectively, the firing temperature may be, for example, 400 ℃ or higher, 450 ℃ or higher, 500 ℃ or higher, or 550 ℃ or higher. The firing time may be, for example, 30 minutes or more and 24 hours or less.

Here, whether the coating layer is formed on the surface of the base material or in the base material can be selected by appropriately adjusting the components of the coating liquid for forming the coating layer, the coating conditions, and the like.

For example, if the particle diameters of the ceria-zirconia composite oxide particles and inorganic oxide particles other than the ceria-zirconia composite oxide particles contained in the coating liquid for forming a coating layer are larger than the average pore diameter of the porous wall of the base material, the coating layer tends to be formed on the surface of the base material;

when the particle diameter of these particles is smaller than the average pore diameter of the porous wall of the base material, the coating layer tends to be formed in the base material.

In addition, if the viscosity of the coating liquid for coating layer formation is high, the coating layer tends to be formed on the surface of the substrate;

when the viscosity of the coating liquid for forming a coating layer is low, the coating layer tends to be formed in the substrate.

Further, if the waiting time after the coating liquid for forming a coating layer is applied to the substrate until the baking is long, the coating layer tends to be formed in the substrate.

Examples

The unit of the gas concentration in the following examples and the like is a volume-based value.

Base material

In the following examples and comparative examples, a direct current type substrate was used as the substrate. The base material was a ceria-zirconia (CZ-based) monolithic (monolith) type honeycomb base material containing a ceria-zirconia composite oxide in an amount of 21 wt% based on ceria and 25 wt% based on zirconia, and the size of the base material was as follows.

Diameter: 117mm

Length: 80mm

Capacity: 860mL

Cell number 400 cells/inch²

Cell shape: square shape

Thickness of porous wall: 120 μm

Comparative example 1

The substrate was immersed in an aqueous solution containing 0.602g (0.70 g/L per 1L of substrate capacity) of palladium nitrate in terms of metallic palladium and 0.258g (0.30 g/L per 1L of substrate capacity) of rhodium nitrate in terms of metallic rhodium for 1 hour. The impregnated substrate was dried and further fired at 500 ℃ for 1 hour in an electric furnace, thereby supporting palladium and rhodium on the porous walls of the substrate, thereby producing an exhaust gas purification catalyst device of comparative example 1.

Fig. 4(a) is a schematic sectional view showing the structure of the exhaust gas purification catalyst device obtained in comparative example 1.

Example 1

(1) Noble metal loading on porous walls of substrate

The substrate was immersed in an aqueous solution (coating liquid for supporting a noble metal catalyst) containing palladium nitrate in an amount of 0.602g (0.70 g/L per 1L of substrate capacity) in terms of metallic palladium for 1 hour. The impregnated substrate was dried and further fired at 500 ℃ for 1 hour in an electric furnace, thereby supporting palladium on the porous walls of the substrate.

(2) Manufacture of exhaust gas purification catalyst device

(i) Preparation of coating liquid for coating layer formation

86.0g (100 g/L of substrate capacity per 1L) of a material containing a ceria-zirconia composite oxide was mixed so as to have the same composition as that of the substrate. An aqueous solution containing 0.258g (0.30 g/L in volume per 1L of substrate) of rhodium nitrate in terms of metal rhodium and an alumina sol as a binder were added to the obtained mixture, and wet-pulverized to prepare a coating liquid for forming a coating layer.

(ii) Formation of the coating

The total amount of the coating liquid for forming a coating layer is applied to the entire length of the substrate on which palladium is supported on the porous wall. The coated substrate was dried and further baked in an electric furnace at 500 ℃ for 1 hour to form a coating layer on the surface of the substrate, thereby producing an exhaust gas purification catalyst device of example 1.

The amount of the coating layer applied to the exhaust gas purifying catalyst device and the amount of rhodium were 100.3g/L and 0.30g/L, respectively, based on the volume of 1L of the region having the coating layer in the substrate.

Fig. 4(b) is a schematic sectional view showing the structure of the exhaust gas purification catalyst device obtained in example 1.

Example 2

(1) Noble metal loading on porous walls of substrate

Palladium was supported on the porous walls of the substrate in the same manner as in example 1.

(2) Manufacture of exhaust gas purification catalyst device

The total amount of the coating liquid for forming a coating layer prepared in the same manner as in example 1 was applied to the substrate having palladium supported on the porous wall in a range of 50% of the length of the substrate from the exhaust gas flow downstream side of the substrate. The coated substrate was dried and further baked in an electric furnace at 500 ℃ for 1 hour to form a coating layer on the surface of the substrate, thereby producing an exhaust gas purification catalyst device of example 2.

The amount of the coating layer applied to the exhaust gas purifying catalyst device and the amount of rhodium were 200.6g/L and 0.60g/L, respectively, based on the volume of 1L of the region having the coating layer in the substrate.

Fig. 4(c) is a schematic sectional view showing the structure of the exhaust gas purification catalyst device obtained in example 2.

Evaluation of OSC Capacity

The exhaust gas purification catalyst devices obtained in comparative example 1, example 1 and example 2 were connected to a gas analyzer manufactured by horiba ltd, and a pretreatment gas (H) was introduced at a temperature of 400 ℃₂ 1％+N₂Equilibrium) was flowed at a flow rate of 35L/min for 5 minutes, and then model gases of stages 1 to 7 shown in table 1 were continuously and sequentially flowed at test temperatures of 2 levels of 400 ℃ and 500 ℃.

TABLE 1

The composition of the gas discharged from the exhaust gas purification catalyst device was evaluated over time, and the CO in stage 7(CO 2%) was investigated₂Discharge ofThis is used as an index of the OSC performance of each exhaust gas purification catalyst device.

The results at a test temperature of 400 ℃ are shown in Table 2, and the results at a test temperature of 500 ℃ are shown in Table 3. Here, the initial OSC amount is CO for 20 seconds from the start of stage 7₂The total amount of emission, i.e., total OSC amount, is CO for 600 seconds from the start of stage 7₂An accumulated value of the discharge amount.

TABLE 2 evaluation results (400 ℃ C.)

TABLE 3 evaluation results (500 ℃ C.)

Fig. 5 and 6 show CO for 40 seconds from the start of phase 7₂The discharge amount varies with time. FIGS. 5(a) and (b) are graphs at a test temperature of 400 ℃ and FIGS. 6(a) and (b) are graphs at a test temperature of 500 ℃. Here, FIG. 5(a) and FIG. 6(a) each show CO for 40 seconds directly from the start of stage 7₂Fig. 5(b) and 6(b) are graphs showing the OSC of each catalyst device separated into the contribution amount of the substrate and the contribution amount of the coating layer.

From the above results, it can be seen that: although the substrate including the OSC material exhibits a certain OSC capacity, there is a certain limit to the initial amount of OSC. In contrast, in the exhaust gas purification catalyst devices of examples 1 and 2 in which the coating layer containing the OSC material was provided on the substrate, both the initial amount of OSC and the total amount of OSC, particularly the initial amount of OSC, were increased. Referring to fig. 5(b) and 6(b), in particular: the coating comprising the OSC material contributes to an increase in the initial amount of OSC.

This can expect that: the exhaust gas purification catalyst device according to the present invention can quickly and effectively alleviate a variation in the exhaust gas environment and perform effective exhaust gas purification when purifying the exhaust gas of an automobile or the like in an actual running environment where a variation in the air-fuel ratio, the space velocity, or the like is expected, for example.

Description of the reference numerals

10. 20 base material

11. 21 porous wall

12. 22-hole chamber

15. 25 coating layer

100. 200 exhaust gas purifying catalyst device

CZ cerium oxide-zirconium oxide composite oxide particle

PGM catalyst noble metal