WO2022131244A1

WO2022131244A1 - Exhaust gas purification catalyst for saddle riding-type vehicle

Info

Publication number: WO2022131244A1
Application number: PCT/JP2021/045998
Authority: WO
Inventors: 健長島
Original assignee: エヌ・イーケムキャット株式会社
Priority date: 2020-12-15
Filing date: 2021-12-14
Publication date: 2022-06-23
Also published as: JPWO2022131244A1; CN116322946A

Abstract

The present invention provides an exhaust gas purification catalyst which is for a saddle riding-type vehicle, has a simple and low-cost structure in which only a singled layered catalyst layer is provided, and has excellent purification performance for CO, HC, and NOx and excellent low-temperature purification performance for the same. The exhaust gas purification catalyst, which is for a saddle riding-type vehicle and is provided in an exhaust gas passage of an internal combustion engine, comprises a metal substrate and a single-layered catalyst layer provided on the metal substrate, wherein the catalyst layer contains: first composite catalyst particles having at least zirconia-based host particles and Rh and CeO2 particles co-supported on the surface of the zirconia-based host particles; second composite catalyst particles having alumina host particles and Pd supported on the surface of the alumina host particles; and/or third composite catalyst particles having ceria alumina host particles and Pd supported on the surface of the ceria alumina host particles.

Description

Exhaust gas purification catalyst for saddle-type vehicles

The present invention relates to an exhaust gas purification catalyst for a saddle-type vehicle such as a two-wheeled vehicle and a method for manufacturing the same, and more particularly to an exhaust gas purification catalyst for a saddle-type vehicle having only one catalyst layer.

Exhaust gas from gasoline-fueled automobiles and motorcycles contains harmful components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). To purify these, hydrocarbons (HC) are oxidized and converted to water and carbon dioxide, carbon monoxide (CO) is oxidized and converted to carbon dioxide, and nitrogen oxides (NOx) are reduced. It is necessary to purify each harmful component with a catalyst, such as converting it to nitrogen. As a catalyst for treating such exhaust gas (hereinafter referred to as "exhaust gas purification catalyst"), a three-way catalyst (TWC) capable of redoxing CO, HC and NOx is used. There is. As such a ternary catalyst, for example, platinum group elements (PGM: Platinum Group Metal) such as ruthenium, rhodium, palladium, osmium, iridium, and platinum are catalytically active components on alumina base material particles having a high specific surface area. It is widely known that the material is supported as a base material, for example, a fire-resistant ceramic or a metal honeycomb-structured Monolithic base material.

In the above-mentioned internal combustion engine such as an automobile, the ratio of fuel to air (air-fuel ratio, A / F) changes greatly according to the operating conditions of the engine such as acceleration, deceleration, low-speed running, and high-speed running, and the theoretical air-fuel ratio in exhaust gas. At 14.7, an oxygen excess atmosphere (fuel lean atmosphere) in which the oxidation reaction is advantageous and a fuel excess condition (fuel rich atmosphere) in which the reduction reaction is advantageous appear alternately and repeatedly according to the driving conditions. .. Therefore, the exhaust gas catalyst needs to exhibit a certain level of catalytic performance under both a fuel lean atmosphere and a fuel rich atmosphere. In particular, in the case of a two-wheeled vehicle, there is a tendency to increase the engine speed in a fuel-rich atmosphere in order to increase the output, so that it is required to exhibit excellent catalytic performance in a fuel-rich atmosphere. Therefore, the air-fuel ratio (A / F) has been controlled conventionally, but the catalyst cannot sufficiently exhibit the purification catalyst performance only by controlling the air-fuel ratio (A / F), so that the catalyst layer itself Is also required to have an action of controlling the air-fuel ratio (A / F).

Therefore, for the purpose of preventing the deterioration of the purification performance of the catalyst caused by the change in the air-fuel ratio by the chemical action of the catalyst itself, a catalyst in which a platinum group element, which is a catalytically active component, is used in combination with an auxiliary catalyst is used. ing. As such an co-catalyst, it may be referred to as an co-catalyst having an oxygen storage capacity (OSC: Oxygen Storage capacity) that releases oxygen in a reducing atmosphere and absorbs oxygen in an oxidizing atmosphere (hereinafter, referred to as "OSC material". )It has been known. Specifically, ceria (cerium oxide, CeO ₂ ), ceria-zirconia composite oxide, and the like are known as OSC materials having an oxygen storage ability. These OSC materials function as a buffer for reducing changes in the oxidizing and reducing properties of the exhaust gas, and have a function of maintaining the purification performance of the catalyst. Further, the ceria-zirconia composite oxide in which zirconia is dissolved in ceria is added to many catalysts as an OSC material because it has a further excellent oxygen storage capacity (OSC).

By the way, the exhaust gas purification catalyst for motorcycles has a special problem different from the exhaust gas purification catalyst for four-wheeled vehicles. For example, an exhaust gas purification catalyst for a two-wheeled vehicle has a limited space for mounting the catalyst as compared with a catalyst for a four-wheeled vehicle, so that it is required to exhibit a high degree of purification ability while having a small capacity. In addition, motorcycles have a relatively short exhaust gas flow path and tend to use a large amount of fuel with an emphasis on output, so that the catalyst is easily exposed to high temperatures. Moreover, since the oxygen concentration in the exhaust gas decreases accordingly, the air-fuel ratio (A / F) in the exhaust gas tends to be less than the theoretical air-fuel ratio of 14.7 in many cases. Therefore, it is required to have excellent heat resistance and excellent exhaust gas purification efficiency even in a fuel-rich atmosphere having an air-fuel ratio (A / F) of less than 14.7.

For example, in Patent Document 1, the amount of CeO ₂ is 45 to 70% by mass, the amount of ZrO ₂ is 20 to 45% by mass, the amount of Nd ₂ O ₃ is 2 to 20% by mass, and La ₂ O. An internal combustion engine exhaust gas characterized by having a carrier made of a cerium-zirconium composite oxide in which the amount of ₃ is 1 to 10% by mass, and a catalyst component made of a metal Pd or Pd oxide supported on the carrier. Purification catalyst materials are disclosed.

Further, Patent Document 2 has a first catalyst layer formed on the surface of a carrier made of ceramics or a metal material and a second catalyst layer formed on the first catalyst layer, and the first catalyst is provided. The layer has a amount of CeO ₂ of 45 to 70% by mass, an amount of ZrO ₂ of 20 to 45% by mass, an amount of Nd ₂ O ₃ of 2 to 20% by mass, and an amount of La ₂ O ₃ in an amount of La 2 O 3. It has a carrier made of a cerium-zirconium composite oxide of 1 to 10% by mass and a catalyst component made of a metal Pd or Pd oxide supported on the carrier, and the second catalyst layer has an amount of ZrO ₂ . Is 50 to 95% by mass, the amount of CeO ₂ is 0 to 40% by mass, the amount of Nd ₂ O ₃ is 2 to 20% by mass, and the amount of La ₂ O ₃ is 1 to 10% by mass. A carrier composed of a zirconium-based composite oxide and a catalyst component composed of a metal Rh or Rh oxide supported on the carrier, or a catalyst component composed of a metal Rh or Rh oxide supported on the carrier and a catalyst component. A catalyst for purifying exhaust gas for a saddle-type vehicle is disclosed, which comprises a catalyst component composed of a metal Pt or a Pt oxide.

On the other hand, as a catalyst for reducing the cost without using Pt and Rh, which are relatively expensive among precious metals, Patent Document 3 describes an exhaust gas purification catalyst for a saddle-mounted vehicle provided in an exhaust passage of an internal combustion engine. A single layer containing a base material, palladium as a catalytically active component, an inorganic porous body such as porous γ-alumina as a catalyst carrier, ceria (CeO ₂ ) particles as a co-catalytic component, and barium. A palladium catalyst for a saddle-type vehicle exhaust gas is disclosed.

Japanese Unexamined Patent Publication No. 2010-227739 WO2010 / 109734 Japanese Unexamined Patent Publication No. 2013-208578

In Patent Document 1, a catalyst material (Pd-supported cerium-zirconium-based composite oxide) in which Pd is supported on the surface of a cerium-zirconium-based composite oxide having a specific composition is used as the base material particles. However, this catalyst material alone still has insufficient purification performance (see Examples 1 and 2).

In addition, the exhaust gas emitted from an internal combustion engine such as an automobile emits a large amount of carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) when the catalyst temperature is low such as at the time of starting. In order to improve the purification performance, it is important to raise the temperature of the catalyst at an early stage and improve the low temperature purification performance of the catalyst. However, the catalyst material described in Patent Document 1 is still insufficient in low temperature catalytic activity by itself (see Examples 1 and 2).

On the other hand, Ce, which is an important rare earth used for phosphors and glass substrate abrasives other than as a catalyst material, has fallen into a supply crisis due to the recent overseas situation, supply is extremely limited, and international prices are high. Has a history of soaring. Therefore, there is a demand for a new catalyst material in which the amount of Ce used is small, but the catalyst material described in Patent Document 1 still has a relatively large amount of Ce used, and from this viewpoint, it meets the recent demands. Not.

Further, the exhaust gas purification catalyst described in Patent Document 2 is provided with a first catalyst layer containing the Pd-supported cerium-zyroxide-based composite oxide described in Patent Document 1 as a catalyst component on the surface of the base material, and the first catalyst layer is provided. It has a laminated structure further provided with a second catalyst layer containing Rh or Pt-supported cerium-zyrosine-based composite oxide as a catalyst component. In order to provide two or more catalyst layers in this way, a series of processes of coating the catalyst slurry, firing, supporting PGM, drying and firing is required for each catalyst layer, resulting in an increase in manufacturing cost. , The obtained exhaust gas purification catalyst becomes expensive. Further, the exhaust gas purification catalyst described in Patent Document 2 has a poor gas diffusivity due to the laminated structure of the catalyst layer, and has insufficient purification performance and low temperature catalytic activity (see Tables 3 and 5).

On the other hand, although Patent Document 3 describes an exhaust gas purification catalyst provided with a single-layer catalyst in which the amount of Ce used is relatively small, the purification performance is extremely low (see Tables 2 and 3). ..

The present invention has been made in view of the above problems. That is, an object of the present invention is for a saddle-type vehicle, which has a simple and low-cost configuration in which only one catalyst layer is provided, but is excellent in CO, HC, NOx purification performance and low-temperature purification performance thereof. The purpose is to provide an exhaust gas purification catalyst and the like.

The present inventors have diligently studied to solve the above problems. As a result, they have found a single-layer catalyst using a combination of predetermined Rh-supported composite catalyst particles and predetermined Pd-supported composite catalyst particles, and have found that the above problems can be solved by using such a single-layer catalyst. It was completed.

That is, the present invention provides various specific embodiments shown below.
[1] An exhaust gas purification catalyst for a saddle-mounted vehicle provided in an exhaust gas passage of an internal combustion engine, comprising a metal base material and a single-layer catalyst layer provided on the metal base material, and the catalyst layer is provided. , A first composite catalyst particle having at least Rh and CeO ₂ particles co-supported on the surface of the zirconia-based base material particles and the zirconia-based base material particles, and on the surface of the alumina base material particles and the alumina base material particles. The saddle-loaded second composite catalyst particles containing the carried Pd and / or the third composite catalyst particles having at least the ceria alumina base material particles and the Pd carried on the surface of the ceria alumina base material particles. Exhaust gas purification catalyst for type vehicles.

[2] The zirconia-based base material particles are rare earth solid-dissolved zirconia base material particles in which at least one or more rare earth elements selected from the group consisting of Ce, Nd, and La are solid-dissolved. Exhaust gas purification catalyst for saddle-mounted vehicles.

[3] The saddle according to [1] or [2], wherein the zirconia-based base material particles contain 65 to 85% by mass of ZrO ₂ and 15 to 35% by mass of an oxide of a rare earth element in terms of oxide. Exhaust gas purification catalyst for riding vehicles.

[4] The saddle according to any one of [1] to [3], wherein the second composite catalyst particle contains the alumina base material particles and Pd and Ba supported on the surface of the alumina base material particles. Exhaust gas purification catalyst for riding vehicles.

[5] The ceria alumina base material particles of the third composite catalyst particles contain 70 to 90% by mass of Al ₂ O ₃ and 10 to 30% by mass of CeO ₂ in terms of oxide, [1] to [ 4] The exhaust gas purification catalyst for a saddle-type vehicle according to any one of the items.

[6] The catalyst layer is any one of [1] to [5], further containing the ceria alumina base material particles and the fourth composite catalyst particles containing Rh supported on the surface of the ceria alumina base material particles. Exhaust gas purification catalyst for saddle-mounted vehicles as described in the section.

[7] The exhaust gas purification catalyst for a saddle-type vehicle according to any one of [1] to [6], wherein the coating amount of the catalyst layer is 1 to 200 g / L per 1 L of the metal base material.

According to the present invention, although it is a simple and low-cost configuration in which only one catalyst layer is provided, it is excellent in CO, HC, NOx purification performance and low temperature purification performance thereof, and is highly productive and economical. It is possible to realize a high-performance exhaust gas purification catalyst for a saddle-mounted vehicle. The exhaust gas purification catalyst for a saddle-type vehicle of the present invention is particularly suitable as a three-way catalyst (TWC: Three Way Catalyst) for reducing NOx, CO, HC, etc. in exhaust gas based on its composition and structure. Can be used. In particular, the exhaust gas purification catalyst for saddle-mounted vehicles of the present invention is preferably used in the field of motorcycles and the like, which are required to have a small capacity and high heat resistance, and also to have high exhaust gas purification efficiency even in a fuel-rich atmosphere. Can be done.

It is a schematic sectional drawing which shows the exhaust gas purification catalyst 100 for a saddle type vehicle of an embodiment. It is a schematic cross-sectional view which shows the schematic structure of the 1st composite catalyst particle 31. It is a schematic cross-sectional view which shows the schematic structure of the 2nd composite catalyst particle 41. It is a schematic cross-sectional view which shows the schematic structure of the 3rd composite catalyst particle 51. It is a schematic cross-sectional view which shows the schematic structure of the 4th composite catalyst particle 61. It is a figure which shows the purification performance (C450 purification rate) of an Example and a comparative example. It is a figure which shows the low temperature purification performance (T50) of an Example and a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the following embodiments are examples for explaining the present invention, and the present invention is not limited thereto. That is, the present invention can be arbitrarily modified and implemented without departing from the gist thereof. In the present specification, for example, the notation of the numerical range of "1 to 100" includes both the lower limit value "1" and the upper limit value "100". The same applies to the notation of other numerical ranges. Further, in the present specification, the positional relationship such as up, down, left, and right shall be based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the ratios shown.

FIG. 1 is a schematic cross-sectional view showing an exhaust gas purification catalyst 100 for a saddle-mounted vehicle according to the present embodiment. 2 to 5 are schematic cross-sectional views showing a schematic configuration of the first composite catalyst particles 31, the second composite catalyst particles 41, the third composite catalyst particles 51, and the fourth composite catalyst particles 61.

The exhaust gas purification catalyst 100 for a saddle-type vehicle of the present embodiment includes a metal base material 11 and a single-layer catalyst layer 21 provided on the metal base material 11, and the catalyst layer 21 is a first composite. It is characterized by containing the catalyst particles 31, the second composite catalyst particles 41 and / or the third composite catalyst particles 51. The exhaust gas purification catalyst 100 for a saddle-type vehicle of the present embodiment is provided in the exhaust gas passage of an internal combustion engine and contains carbon monoxide (CO), hydrocarbon (HC), nitrogen oxides (NOx) and the like passing through the system. Purify.

The metal base material 11 is a support that supports the above-mentioned single-layer catalyst layer 21. As the metal base material 11, those known in the art can be appropriately selected, and the type thereof is not particularly limited. Examples of the metal base material 11 include, but are not limited to, a metal honeycomb carrier made of stainless steel, a wire mesh carrier made of stainless steel, a steel wool-like knit wire carrier, and the like. Further, the shape thereof is not particularly limited, and any shape such as a prismatic shape, a cylindrical shape, a spherical shape, a honeycomb shape, a sheet shape, and a pellet shape can be selected. These can be used individually by 1 type or in combination of 2 or more types as appropriate.

The catalyst layer 21 is a single catalyst layer provided on the metal base material 11. The catalyst layer 21 contains a first composite catalyst particle 31, a second composite catalyst particle 41 and / or a third composite catalyst particle 51, and, if necessary, a fourth composite catalyst particle 61.

The first composite catalyst particle 31 is a composite particle having at least the zirconia-based base particle 32 and the Rh and CeO ₂ particles 33 co-supported on the surface 32a of the zirconia-based base particle 32. In the first composite catalyst particles 31, Rh and CeO ₂ particles 33 are co-supported on the surface 32a of the zirconia-based base material particles 32 to suppress a decrease in catalytic activity due to grain growth of Rh and carbon monoxide. By supporting CeO ₂ particles 33, high purification performance is exhibited in a wide range of A / F windows for the exhaust gas of a saddle-type vehicle in which the concentrations of (CO), hydrocarbons (HC), and nitrogen oxides (NOx) change drastically. , The low temperature purification performance is also improved. The first composite catalyst particles 31 may be used alone or in combination of two or more.

The zirconia-based base material particles 32 are zirconia (ZrO ₂ ), a composite oxide obtained by doping zirconia (ZrO ₂ ) with another element, or a solid solution thereof. Specific examples of the zirconia-based base material particles 32 include zirconium oxide (IV), zirconium-rare earth element composite oxide, zirconium-transition element composite oxide, zirconium-rare earth element-transition element composite oxide and the like. Here, examples of the rare earth element include, but are not limited to, cerium, neodymium, praseodymium, lanthanum, yttrium, and the like. As the rare earth element, one kind may be used alone, or two or more kinds may be used in combination as appropriate. When the rare earth element is contained, the content ratio thereof is not particularly limited, but is the total amount of the rare earth element in terms of oxide (for example, La ₂ O ₃ , Nd ₂ O ₃ , Pr) with respect to the total amount of the zirconia-based base material particles 32. _In total of _5O11 and the like), 0.1% by mass or more is preferable, 5% by mass or more is more preferable, 10% by mass or more is further preferable, 50% by mass or less is preferable, 45% by mass or less is more preferable, and 40. More preferably, it is by mass or less. The transition element is not particularly limited, and examples thereof include chromium, cobalt, iron, nickel, titanium, manganese, and copper. As the transition element, one kind may be used alone, or two or more kinds may be used in combination as appropriate. When the transition element is contained, the content ratio thereof is not particularly limited, but the total amount of the above-mentioned transition element in terms of oxide (for example, Fe ₂ O ₃ , TiO ₂ etc.) with respect to the total amount of the zirconia-based base material particles 32 is not particularly limited. Total), 0.01% by mass or more is preferable, 0.1% by mass or more is more preferable, 0.5% by mass or more is further preferable, 10% by mass or less is preferable, 5% by mass or less is more preferable, and 3% by mass is used. % Or less is more preferable. As the zirconia-based base material particles 32, one type can be used alone, or two or more types can be used in combination as appropriate.

As the zirconia-based base material particles 32, a zirconia-based composite oxide containing 65 to 85% by mass of ZrO ₂ in terms of oxide and 15 to 35% by mass of an oxide of a rare earth element is preferable, and ZrO ₂ is used in terms of oxide. A zirconia-based composite oxide containing 70 to 80% by mass and an oxide of a rare earth element in an amount of 20 to 30% by mass is more preferable.

In the zirconia-based base material particles 32, a part of zirconium is replaced with alkali metal elements such as lithium, sodium and potassium, and alkaline earth metal elements such as beryllium, magnesium, calcium, strontium and barium. May be good. Further, as the alkali metal element and the alkaline earth metal element, one kind may be used alone, or two or more kinds may be used in any combination and ratio. Further, the zirconia-based base material particles 32 may contain hafnium (Hf), which is usually contained in the zirconia ore in an amount of about 1 to 2% by mass, as an unavoidable impurity.

The average particle diameter D ₅₀ of the zirconia-based base material particles 32 can be appropriately set according to the desired performance, and is not particularly limited. The average particle size _D50 of the zirconia-based base particle 32 is preferably 1 μm or more, more preferably 5 μm or more, from the viewpoint of maintaining a large specific surface area and increasing heat resistance to increase the number of its own catalytically active sites. It is preferably 10 μm or more, more preferably 30 μm or less, more preferably 20 μm or less, still more preferably 15 μm or less. In the present specification, the average particle size D ₅₀ of the particles is a median diameter measured by a laser diffraction type particle size distribution measuring device (for example, a laser folding type particle size distribution measuring device SALD-3100 manufactured by Shimadzu Corporation). Means.

Rh and CeO ₂ particles 33 are co-supported in a highly dispersed manner on the surface 32a of the zirconia-based base material particles 32. Here, Rh functions as a catalytically active component, and the CeO ₂ particles 33 function as a catalytically active component or a co-catalyst having oxygen storage capacity (OSC: Oxygen Storage Capacity). By co-supporting Rh and CeO ₂ particles 33 on the surface 32a of the zirconia-based base particle 32, heat resistance can be enhanced and deterioration of catalytic performance when exposed to high temperature can be suppressed, thereby purifying performance and low temperature. Purification performance is enhanced. Further, since the CeO ₂ particles 33 are supported on the surface 32a of the zirconia-based base particle 32, the interaction between Rh and Ce is promoted, which also enhances the purification performance and the low temperature purification performance.

The content ratio of Rh may be appropriately set according to the desired performance in consideration of the material and pore diameter of the zirconia-based base material particles 32, and is not particularly limited, but from the viewpoint of catalytic activity and the like, the first composite catalyst particles. The total amount of Rh in terms of metal is preferably 0.001 to 5% by mass, more preferably 0.01 to 3% by mass, and further preferably 0.1 to 1% by mass with respect to the total amount of 31.

The content ratio of the CeO ₂ particles 33 may be appropriately set according to the desired performance in consideration of the material and pore diameter of the zirconia-based base particle 32, and is not particularly limited, but is first from the viewpoint of catalytic activity and the like. With respect to the total amount of the composite catalyst particles 31 (excluding the amount of noble metal), 5 to 20% by mass is preferable, more preferably 7 to 18% by mass, and further preferably 10 to 15% by mass in terms of oxide. be.

The second composite catalyst particle 41 is a composite particle having at least an alumina base material particle 42 and Pd supported on the surface 42a of the alumina base material particle 42. As the second composite catalyst particle 41, one kind may be used alone, or two or more kinds may be used in combination as appropriate.

The alumina base material particles 42 are base material particles containing alumina (Al ₂ O ₃ ) as a main component. Here, "containing alumina as a main component" means that alumina is contained in an amount of more than 90% by mass to 100% by mass or less with respect to the total amount of the alumina base material particles 42. Specific examples of the alumina base material particles 42 include alumina, silica-alumina, aluminosilicates, alumina-zirconia, alumina-chromia, alumina-ceria, alumina-magnesium oxide, alumina-barium oxide, alumina-lanthanum oxide and the like. However, the present invention is not particularly limited to these. As the alumina base material particles 42, one type may be used alone, or two or more types may be used in combination as appropriate.

The average particle diameter D ₅₀ of the alumina base material particles 42 can be appropriately set according to the desired performance, and is not particularly limited. From the viewpoint of maintaining a large specific surface area and increasing the number of catalytically active sites, the average particle diameter D ₅₀ of the alumina base particle 42 is preferably 0.1 μm or more, more preferably 1 μm or more, and further preferably 3 μm or more. It is preferably 50 μm or less, more preferably 45 μm or less, still more preferably 40 μm or less.

Pd is co-supported with high dispersion on the surface 42a of the alumina base material particles 42. Here, Pd functions as a catalytically active ingredient. By supporting Pd on the surface 42a of the alumina base material particles 42, the purification performance and the low temperature purification performance are enhanced.

The content ratio of Pd may be appropriately set according to the desired performance in consideration of the material and pore diameter of the alumina base particle 42, and is not particularly limited, but from the viewpoint of catalytic activity and the like, the second composite catalyst particle 41 The total amount of Pd in terms of metal is preferably 0.001 to 5% by mass, more preferably 0.01 to 3% by mass, and further preferably 0.1 to 1% by mass with respect to the total amount of Pd.

The second composite catalyst particle 41 may further support the Ba component, which is an alkaline earth metal, on the surface 42a of the alumina base material particles 42. These components are known as NOx storage components. The Ba component can be supported on the surface 42a of the alumina base material particles 42 as barium carbonate, barium sulfate, or the like, and occludes NOx in a lean environment with a large amount of oxygen, and occludes NOx in a Rich environment with a small amount of oxygen. Is released. The content ratio of the Ba component may be appropriately set according to the desired performance in consideration of the material and pore diameter of the alumina base material particles 42, and is not particularly limited, but from the viewpoint of catalytic activity and the like, the second composite catalyst particles. With respect to the total amount of 41 (excluding the amount of noble metal), 0.1 to 10% by mass is preferable, more preferably 0.5 to 8% by mass, and further preferably 1 to 5% by mass in terms of oxide. Is.

The third composite catalyst particle 51 is a composite particle having at least ceria alumina base material particles 52 and Pd supported on the surface 52a of the ceria alumina base material particles 52. As the third composite catalyst particle 51, one kind may be used alone, or two or more kinds may be used in combination as appropriate.

The ceria alumina base material particles 52 are composite oxides of ceria (CeO ₂ ) and alumina (Al ₂ O ₃ ). The content ratios of ceria and alumina can be appropriately set according to the desired performance and are not particularly limited, but the content ratio of ceria: alumina is 10 to 30% by mass: 70 to 90% by mass in terms of oxide. It is preferable, and more preferably 15 to 25% by mass: 75 to 85% by mass. In addition to ceria and alumina, the ceria alumina base material particles 52 may contain the above-mentioned rare earth element, transition element, alkali metal element, alkaline earth metal element and the like. Further, the ceria alumina base material particles 52 may be used alone or in combination of two or more.

The average particle diameter D ₅₀ of the ceria alumina base material particles 52 can be appropriately set according to the desired performance, and is not particularly limited. From the viewpoint of maintaining a large specific surface area and increasing the number of catalytically active sites, the average particle diameter _D50 of the ceria alumina base particle 52 is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more. , 30 μm or less is preferable, 20 μm or less is more preferable, and 15 μm or less is further preferable.

Pd is co-supported with high dispersion on the surface 52a of the ceria alumina base material particles 52. Here, Pd functions as a catalytically active ingredient. By supporting Pd on the surface 52a of the ceria alumina base material particles 52, high heat resistance and OSC performance can be maintained, thereby enhancing purification performance and low temperature purification performance.

The content ratio of Pd may be appropriately set according to the desired performance in consideration of the material and pore diameter of the ceria alumina base particle 52, and is not particularly limited, but from the viewpoint of catalytic activity and the like, the third composite catalyst particle. The total amount of Pd in terms of metal is preferably 0.001 to 15% by mass, more preferably 0.1 to 5% by mass, and further preferably 0.3 to 3% by mass with respect to the total amount of 51.

The fourth composite catalyst particle 61 is a composite particle having at least ceria alumina base material particles 62 and Rh supported on the surface 62a of the ceria alumina base material particles 62. As the fourth composite catalyst particle 61, one kind may be used alone, or two or more kinds may be used in combination as appropriate.

The ceria alumina base material particles 62 are composite oxides of ceria (CeO ₂ ) and alumina (Al ₂ O ₃ ). The content ratios of ceria and alumina can be appropriately set according to the desired performance and are not particularly limited, but the content ratio of ceria: alumina is 10 to 30% by mass: 70 to 90% by mass in terms of oxide. It is preferable, and more preferably 15 to 25% by mass: 75 to 85% by mass. In addition to ceria and alumina, the ceria alumina base material particles 62 may contain the above-mentioned rare earth element, transition element, alkali metal element, alkaline earth metal element and the like. Further, as the ceria alumina base material particles 62, one type may be used alone, or two or more types may be used in combination as appropriate.

The average particle diameter D ₅₀ of the ceria alumina base material particles 62 can be appropriately set according to the desired performance, and is not particularly limited. From the viewpoint of maintaining a large specific surface area and increasing the number of catalytically active sites, the average particle diameter _D50 of the ceria alumina base particle 62 is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more. , 30 μm or less is preferable, 20 μm or less is more preferable, and 15 μm or less is further preferable.

Rh is co-supported with high dispersion on the surface 62a of the ceria alumina base material particles 62. Here, Rh functions as a catalytically active ingredient. By supporting Rh on the surface 62a of the ceria alumina base material particles 62, high heat resistance and OSC performance can be maintained, and deterioration of catalytic performance when exposed to high temperature can be suppressed, thereby purifying performance and low temperature. Purification performance is enhanced.

The content ratio of Rh may be appropriately set according to the desired performance in consideration of the material and pore diameter of the ceria alumina base material particles 62, and is not particularly limited, but from the viewpoint of catalytic activity and the like, the fourth composite catalyst particles. The total amount of Rh in terms of metal is preferably 0.001 to 15% by mass, more preferably 0.1 to 5% by mass, and further preferably 0.3 to 3% by mass with respect to the total amount of 61.

In the catalyst layer 21 of the present embodiment, Rh and Pd supported on the

composite catalyst particles

31, 41, 51, 61 can be changed to a simple substance of a metal or a metal oxide depending on the external environment. Therefore, Rh and Pd supported on the

composite catalyst particles

31, 41, 51, 61 need only be confirmed at least in a reducing atmosphere, and the properties of Rh and Pd in an oxidizing atmosphere and a stoichiometric atmosphere are particularly good for a single metal. Not limited. Here, in the present specification, the reducing atmosphere means a state of being allowed to stand at 400 ° C. for 0.5 hours or more under a hydrogen gas atmosphere. The presence of Rh and Pd is observed by observation with a scanning transmission electron microscope (STEM), powder X-ray diffraction (XRD: X-ray Diffraction, electron probe microanalyzer (EPMA: Electron Probe Micro Analyzer), etc. It can be grasped by various measurement methods such as X-ray photoelectric spectroscopy (XPS: X-ray Photoelectron Spectroscopy or ESCA: Electron Spectroscopy for Chemical Analysis).

As described above, the methods for producing the

composite catalyst particles

31, 41, 51, 61 include Rh, Pd, CeO ₂ particles 33, and the

surface

32a, 42a, 52a of each

base particle

32, 42, 52, 62 having a barium component. It is not particularly limited as long as the one supported on 62a can be obtained. From the viewpoint of producing composite particles easily and at low cost, the evaporation dry solid method (impregnation method) or the like is preferable.

As the

base material particles

32, 42, 52, 62 used as raw materials here, various grades of commercially available products can be used, and they can also be produced by a method known in the art. These production methods are not particularly limited, but for example, the zirconia-based base material particles 32 are preferably a coprecipitation method or an alkoxide method. As a coprecipitation method, for example, an alkaline substance is added to an aqueous solution in which a cerium salt and / or a zirconium salt is mixed with other rare earth metal elements or transition elements to be blended as necessary at a predetermined chemical quantitative ratio. The method of hydrolyzing or coprecipitating the precursor and firing the hydrolysis product or coprecipitate thereof is preferable. The types of various salts used here are not particularly limited. Generally, hydrochlorides, oxy hydrochlorides, nitrates, oxynitrates, carbonates, phosphates, acetates, oxalates, citrates and the like are preferred. Further, the type of alkaline substance is not particularly limited. Generally, an aqueous ammonia solution is preferable. As an alkoxide method, for example, a mixture of cerium alkoxide and / or zirconium alkoxide mixed with other rare earth metal elements, transition elements, etc. to be blended as necessary at a predetermined chemical quantitative ratio is hydrolyzed, and then hydrolyzed. A manufacturing method of firing is preferable. The type of alkoxide used here is not particularly limited. In general, methoxide, ethoxide, propoxide, isopropoxide, butoxide, and ethylene oxide adducts thereof are preferable. Further, the rare earth metal element may be blended as a metal alkoxide or as various salts described above. The firing conditions may be according to a conventional method and are not particularly limited. The firing atmosphere may be any of an oxidizing atmosphere, a reducing atmosphere, and an atmospheric atmosphere. The firing temperature and treatment time vary depending on the desired composition and its stoichiometric ratio, but from the viewpoint of productivity and the like, generally, 1 to 12 hours is preferable at 150 ° C. or higher and 1300 ° C. or lower, more preferably. Is 350 ° C. or higher and 800 ° C. or lower for 2 to 4 hours. Prior to high-temperature firing, it is preferable to perform vacuum drying using a vacuum dryer or the like, and to perform a drying treatment at 50 ° C. or higher and 200 ° C. or lower for about 1 to 48 hours.

As an evaporative drying method, the above-mentioned

base material particles

32, 42, 52, 62 are impregnated with an aqueous solution containing Rh or Pd ions, Ce ions, Ba ions, etc. to be supported, and then heat-treated. Alternatively, a manufacturing method for chemical treatment is preferable. By this impregnation treatment, Rh and Pd ions, Ce ions, Ba ions and the like are adsorbed (adhered) on the

surfaces

32a, 42a, 52a and 62a of the

base material particles

32, 42, 52 and 62 in a highly dispersed state. To. At this time, the ions of Rh and Pd can be added to the aqueous solution as various salts of Rh and Pd. The types of various salts used here are not particularly limited. In general, sulfates, hydrochlorides, oxysalts, nitrates, oxynitrates, carbonates, oxycarbonates, phosphates, acetates, oxalates, citrates, chlorides, oxides, complex oxidations. Goods, complex salts and the like are preferable. Further, the content ratio of the ions of Rh and Pd in the aqueous solution can be appropriately adjusted so that the content ratio of Rh and Pd in each of the obtained

composite catalyst particles

31, 41, 51, 61 or the catalyst layer 21 is a desired ratio. It can be done, and it is not particularly limited. Needless to say, the aqueous solution used here may contain the above-mentioned optional components such as other rare earth elements and transition elements, as well as unavoidable impurities.

After the impregnation treatment, if necessary, a solid-liquid separation treatment, a water washing treatment, for example, a drying treatment for removing water at a temperature of 50 ° C. or higher and 200 ° C. or lower in the air for about 1 to 48 hours is performed according to a conventional method. be able to. The drying treatment may be natural drying, or a drying device such as a drum type dryer, a vacuum dryer, or a spray dryer may be used. Further, the atmosphere during the drying treatment may be any of the atmosphere, the vacuum, and the atmosphere of an inert gas such as nitrogen gas. Before and after drying, pulverization treatment, classification treatment, etc. may be further performed as necessary. Further, chemical treatment may be performed. For example, after the impregnation treatment in the above evaporation to dryness method, the ions of Rh and Pd are hydrolyzed on the

base material particles

32, 42, 52 and 62 using a basic component. You may let me. The basic component used here is preferably amines such as ammonia and ethanolamine, alkali metal hydroxides such as caustic soda and strontium hydroxide, and alkaline earth metal hydroxides such as barium hydroxide. By these heat treatments and chemical treatments, Rh, Pd, etc., which are highly dispersed in nano-order size, and CeO ₂ particles 33 and barium components are generated on each

base particle

32, 42, 52, 62 as needed. To.

The firing conditions may be in accordance with a conventional method and are not particularly limited. The heating means is not particularly limited, and known equipment such as an electric furnace or a gas furnace can be used. The firing atmosphere may be any of an oxidizing atmosphere, an atmospheric atmosphere, and a reducing atmosphere, and the oxidizing atmosphere and the atmospheric atmosphere are preferable. The firing temperature and treatment time vary depending on the desired performance, but from the viewpoint of Rh and Pd production and productivity, it is generally preferable to use 0.1 to 12 hours at 300 ° C. or higher and 1100 ° C. or lower. It is preferably 400 ° C. or higher and 800 ° C. or lower for 0.5 to 6 hours.

The catalyst layer 21 can be used by mixing with a catalyst, a co-catalyst, base metal particles, etc. known in the art, in addition to the above-mentioned components. Known catalysts, co-catalysts, and base metal particles that can be used in combination include, for example, metal oxides or metal composite oxides such as silica, alumina, lanthanum oxide, neodymium oxide, and placeodium oxide; perovskite-type oxides; silica-alumina. , Silica-alumina-zirconia, a composite oxide containing alumina such as silica-alumina-boria; barium compounds, zeolites and the like, but are not particularly limited thereto. The ratio of the catalyst, co-catalyst, and base particle to be used in combination can be appropriately set according to the required performance and the like, and is not particularly limited, but is preferably 0.01% by mass or more and 20% by mass or less in total with respect to the total amount. A total of 0.05% by mass or more and 10% by mass or less is more preferable, and a total of 0.1% by mass or more and 8% by mass or less is further preferable.

Further, the catalyst layer 21 can be used by mixing with additives known in the art in addition to the above-mentioned components. Examples of the additive that can be used in combination include, but are not limited to, various binders, dispersion stabilizers such as nonionic surfactants and anionic surfactants, pH adjusters, viscosity regulators, and the like. Examples of the binder include, but are not limited to, various sol such as alumina sol, titania sol, silica sol, and zirconia sol. Further, soluble salts such as aluminum nitrate, aluminum acetate, titanium nitrate, titanium acetate, zirconium nitrate and zirconium acetate can also be used as a binder. In addition, acids such as acetic acid, nitric acid, hydrochloric acid, and sulfuric acid can also be used as the binder. The amount of the binder used is not particularly limited and may be an amount necessary for maintaining the molded product. The ratio of the above-mentioned additives to be used can be appropriately set according to the required performance and the like, and is not particularly limited, but is preferably 0.01 to 20% by mass in total and 0.05 to 10% by mass in total with respect to the total amount. % Is more preferable, and 0.1 to 8% by mass in total is further preferable.

In the exhaust gas purification catalyst 100 for a saddle-mounted vehicle of the present embodiment, the catalyst layer 21 described above is provided on at least one surface side of the metal base material 11. By adopting such a configuration, the applicability to various applications is increased, such as realizing a low-cost catalyst configuration with a small manufacturing load and facilitating incorporation into an apparatus at the time of manufacturing. For example, a metal honeycomb structure carrier or the like is used as the metal base material 11, and the exhaust gas purification catalyst 100 for a saddle-mounted vehicle is installed in the flow path through which the gas flow passes, and the gas flow is passed through the cell of the honeycomb structure carrier. Therefore, exhaust gas purification can be performed with high efficiency.

Here, in the present specification, the "single-layer catalyst" means a catalyst having only one catalyst layer. Further, "provided on at least one surface side of the metal substrate 11" means that an arbitrary other layer other than the catalyst layer is interposed between one surface of the metal substrate 11 and the catalyst layer. It is a meaning that includes.

Such an exhaust gas purification catalyst 100 for a saddle-mounted vehicle can be obtained, for example, by providing the catalyst layer 21 on the above-mentioned metal base material 11. The method for forming the catalyst layer 21 may be carried out according to a conventional method, and is not particularly limited. For example, a slurry-like mixture containing each component of the catalyst layer 21 described above is applied onto the metal substrate 11 by applying various known coating methods, wash coat methods, etc., and dried or fired as necessary. By doing so, the exhaust gas purification catalyst 100 for a slurry-type vehicle of the present embodiment can be obtained.

Specific examples include the above-mentioned

composite catalyst particles

31, 41, 51, 61, an aqueous medium, and optionally a binder known in the art, other catalysts, co-catalysts, OSC materials, various base material particles, and additives. Etc. are mixed at a desired blending ratio to prepare a slurry-like mixture, and the obtained slurry-like mixture is applied to the surface of the metal base material 11 and dried and fired to obtain a catalyst layer on the metal base material 11. It is possible to obtain an exhaust gas purification catalyst 100 for a slurry-type vehicle provided with 21.

The aqueous medium used when preparing the slurry-like mixture may be an amount that allows each main component to be uniformly dispersed in the slurry. At this time, if necessary, an acid or a base for adjusting the pH can be added, or a surfactant, a resin for dispersion, or the like for adjusting the viscosity or improving the dispersibility of the slurry can be added. From the viewpoint of firmly adhering or bonding the obtained catalyst layer 21 to the metal substrate 11, it is preferable to use the above-mentioned binder or the like. Further, as a method for mixing the slurry, a known pulverizing method or mixing method such as pulverizing and mixing with a ball mill or the like can be applied.

After the slurry-like mixture is applied onto the metal substrate 11, it can be dried or fired according to a conventional method. The drying temperature is not particularly limited, but is preferably 70 to 200 ° C, more preferably 80 to 150 ° C, for example. The firing temperature is not particularly limited, but is preferably 300 to 650 ° C, more preferably 400 to 600 ° C, for example. The heating means used at this time can be a known heating means such as an electric furnace or a gas furnace.

The total coating amount of the catalyst layer 21 described above is not particularly limited, but is 1 to 200 g / L (excluding the amount of precious metal) per 1 L of the capacity of the metal base material 11 from the viewpoint of catalyst performance, balance of pressure loss, and the like. It is preferably 50 to 180 g / L (excluding the amount of precious metal), and more preferably.

The total coating amount of Rh and Pd is not particularly limited, but is preferably 0.05 to 1.5 g / L in terms of metal, and 0.1 to 1.0 g, from the viewpoint of catalyst performance, balance of pressure loss, and the like. / L is more preferable. At this time, the total coating amount of Rh is not particularly limited, but is preferably 0.02 to 0.6 g / L in terms of metal, and 0.04 to 0.4 g / L from the viewpoint of catalyst performance, pressure loss balance, and the like. L is more preferable. On the other hand, the total coating amount of Pd is not particularly limited, but is preferably 0.03 to 0.9 g / L in terms of metal, and 0.06 to 0.6 g / L from the viewpoint of catalytic performance and balance of pressure loss. Is more preferable. The mass ratio (Pd / Rh) of the coating amount of Pd and Rh is preferably 10/1 to 10/9, more preferably 10/2 to 10/8 in terms of metal.

The exhaust gas purification catalyst 100 for a saddle-type vehicle of the present embodiment described above can be arranged in the exhaust system of various engines of the saddle-type vehicle, and the number and location of the installation thereof can be arbitrarily determined according to the exhaust gas regulation. Can be designed. The exhaust gas purification catalyst 100 for a saddle-mounted vehicle of the present embodiment has a simple and low-cost configuration in which only one catalyst layer is provided, but has CO, HC, and NOx purification performance and low-temperature purification performance. It can exert an excellent effect on.

The features of the present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. That is, the materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Further, the values of various manufacturing conditions and evaluation results in the following examples have meanings as a preferable upper limit value or a preferable lower limit value in the embodiment of the present invention, and the preferable numerical range is the above-mentioned upper limit value or the lower limit value. It may be in the range specified by the combination of the value and the value of the following examples or the values of the examples.

(Example 1)
Zirconia composite oxide base material particles containing 75.0% by mass of ZrO ₂ and 25.0% by mass of oxides of rare earth elements are charged into a Nauta mixer, and a predetermined amount of cerium nitrate and diluting material are used. After further adding pure water, the mixture was stirred for 15 minutes to prepare composite particles in which 12.5% by mass of CeO ₂ particles were carried on the surface of the zirconia composite oxide base material particles in terms of oxide.

Next, a predetermined amount of rhodium nitrate and pure water were added to the stirrer and stirred for 5 minutes, and then the above composite particles were added and further stirred for 15 minutes. As a result, a Rh catalyst slurry containing the first composite catalyst particles in which Rh and CeO ₂ particles were co-supported on the surface of the zirconia composite oxide base material particles was obtained.

Next, a predetermined amount of palladium nitrate and pure water were added to the stirrer and stirred for 5 minutes, and then Al ₂ O ₃ was 80.7% by mass and CeO ₂ was 19 in terms of oxide for the third composite catalyst particles. . Celia alumina base material particles containing 3% by mass were further added and stirred for 15 minutes. As a result, a Pd catalyst slurry containing the third composite catalyst particles in which Pd was supported on the surface of the ceria alumina base material particles was obtained.

The obtained Rh catalyst slurry and Pd catalyst slurry were weighed in predetermined amounts, put into a stirrer, and stirred for 15 minutes. Then, it was pulverized with a ball mill until the average particle diameter D90 became 11 μm. An alumina sol-based binder material and distilled water were added to the obtained mixture, and the mixture was further stirred for 10 minutes to obtain a catalyst slurry for wash coat.

Then, after immersing the stainless metal honeycomb carrier (300 cpsi / 50 μm, 40 × 90 mmL) in the catalyst slurry for wash coat, the excess wash coat liquid in the cell is removed by air blow, dried, and fired at 500 ° C. for 1 hour. Then, an exhaust gas purification catalyst for a slurry-type vehicle was obtained. The wash coat amount of this catalyst was 120 g / L (excluding the amount of precious metal) per 1 L of stainless metal honeycomb carrier, the Rh content was 0.2 g / L, and the Pd content was 0.3 g / L. ..

(Example 2)
A predetermined amount of rhodium nitrate and pure water were added to the stirrer and stirred for 5 minutes, and then the CeO2 particle _- supporting composite particles obtained in Example 1 were added and further stirred for 15 minutes. Celia alumina base material particles containing 80.7% by mass of Al ₂ O ₃ and 19.3% by mass of CeO ₂ in terms of oxide for the fourth composite catalyst particles were further added thereto, and the mixture was stirred for 15 minutes. As a result, Rh containing the first composite catalyst particles in which Rh and CeO2 particles are co _- supported on the surface of the zirconia composite oxide base material particles and the fourth composite catalyst particles in which Rh is supported on the surface of the ceria alumina base material particles. A catalyst slurry was obtained.

Next, a predetermined amount of palladium nitrate and pure water were added to the stirrer and stirred for ₅ minutes, and then _Al2O3 powder having Ba supported on the surface was added and further stirred for 15 minutes. Then, 1N nitric acid was added until the pH reached 4 to 5, and the mixture was stirred for 15 minutes. As a result, a Pd catalyst slurry containing the second composite catalyst particles in which Pd and Ba were supported on the surface of the alumina particles was obtained.

The obtained Rh catalyst slurry and Pd catalyst slurry are weighed in predetermined amounts and put into a stirrer, and after stirring for 15 minutes, Al ₂ O ₃ powder having Ba supported on the surface is further put into the stirrer for 15 minutes. Stirred. Then, it was pulverized with a ball mill until the average particle diameter D90 became 11 μm. An alumina sol-based binder material and distilled water were added to the obtained mixture, and the mixture was further stirred for 10 minutes to obtain a catalyst slurry for wash coat.

(Comparative Example 1)
A predetermined amount of rhodium nitrate and pure water were added to the stirrer and stirred for 5 minutes, then ceria alumina base material particles were added and stirred for 15 minutes. As a result, a mixed slurry containing composite catalyst particles in which Rh was supported on the surface of the ceria alumina base material particles was obtained. Then, this mixed slurry was pulverized with a ball mill until the average particle size D90 became 11 μm. An alumina sol-based binder material and distilled water are added to the obtained mixture, and then the mixture is further stirred for 10 minutes to obtain a Rh catalyst slurry containing composite catalyst particles in which Rh is supported on the surface of the ceria alumina base material particles. Obtained.

Next, a predetermined amount of palladium nitrate and pure water were added to the stirrer and stirred for 5 minutes, then ceria alumina base material particles were added and stirred for 15 minutes. As a result, a mixed slurry containing composite catalyst particles in which Pd was supported on the surface of the ceria alumina base material particles was obtained. Then, this mixed slurry was pulverized with a ball mill until the average particle size D90 became 11 μm. An alumina sol-based binder material and distilled water were added to the obtained mixture, and the mixture was further stirred for 10 minutes to obtain a Pd-catalyzed slurry.

Then, after immersing the stainless metal honeycomb carrier (300 cpsi / 50 μm, 40 × 90 mmL) in the Pd catalyst slurry, excess washcoat liquid in the cell was removed by air blowing, dried, and calcined at 500 ° C. for 1 hour. Then, after immersing the stainless metal honeycomb carrier coated with the Pd catalyst slurry in the Rh catalyst slurry, excess washcoat liquid in the cell is removed by air blowing, dried, and fired at 500 ° C. for 1 hour to saddle. An exhaust gas purification multilayer catalyst for riding vehicles was obtained. The wash coat amount of this catalyst was 120 g / L (excluding the amount of precious metal) per 1 L of stainless metal honeycomb carrier, the Rh content was 0.2 g / L, and the Pd content was 0.3 g / L. ..

(Comparative Example 2)
The Rh catalyst slurry obtained in Comparative Example 1 and the Pd catalyst slurry obtained in Comparative Example 1 are weighed in predetermined amounts and put into a stirrer, and after adding an alumina sol-based binder material and distilled water, the mixture is stirred for 10 minutes. As a result, a catalyst slurry for wash coat was obtained.

<Performance evaluation>
The purification characteristics of each catalyst were evaluated using a model gas evaluation device manufactured by HORIBA, Ltd. Here, HC, CO and NO (the rate at which nitrogen oxide is reduced at 450 ° C. (C450 purification rate) and the temperature at which the 50% purification rate is reached [T50 (° C.)] in the model gas are measured and each is measured. The ternary purification performance of the catalyst was evaluated. In this evaluation, a test piece (25.4 × 50 mmL) was used from the exhaust gas purification catalyst for a saddle-mounted vehicle obtained in Examples 1 and 2 and Comparative Examples 1 and 2. After punching, this test piece was subjected to a rich atmosphere of 2% CO + 10% H ₂ O + remaining N ₂ and a lean atmosphere of 5% O ₂ + 10% H ₂ O + remaining N ₂ at intervals of 5 minutes at 1050 ° C. The catalyst after the endurance treatment, which was held for 5 hours in the above, was used as an evaluation sample. The evaluation device used was a flow-type reaction device composed of stainless steel pipes, and a model having the following composition from the entry side. Gas is introduced, distributed to the exhaust gas purification reaction section, and discharged to the outlet side. By heating the model gas with an external heater and sending it to the exhaust gas purification reaction section, the purification reaction section is heated. The gas composition on the outflow side (after passing through the catalyst portion) is analyzed in the temperature range of 100 ° C to 450 ° C, and the rate of change in CO, HC, and NO concentrations is determined. The results are shown in FIGS. 6 and 7. ..

Model gas composition: CO: 0.3%, C ₃ H ₆ : 3000 ppm, NO: 3000 ppm, O ₂ : 0.15%, CO ₂ : 10%, H ₂ O: 10%, N ₂ : Residual A / F = 14.5
Space velocity (SV): 72,000 / h
Evaluation temperature: 100-500 ° C
Temperature rise rate: 10 ° C / min

The exhaust gas purification catalyst for a saddle-type vehicle of the present invention has a simple and low-cost configuration in which only one catalyst layer is provided, but is excellent in CO, HC, NOx purification performance and low-temperature purification performance thereof. Since it is excellent in productivity and economy, it can be widely and effectively used as a three-way catalyst (TWC: Three Way Catalyst) that reduces NOx, CO, HC, etc. in exhaust gas based on its composition and structure. In particular, the exhaust gas purification catalyst for a saddle-mounted vehicle of the present invention is particularly effectively used in the field of motorcycles and the like, which are required to have a small capacity and high heat resistance, and are also required to have high exhaust gas purification efficiency even in a fuel-rich atmosphere. It is possible.

100 ・・・ Exhaust gas purification catalyst for saddle-mounted vehicle 11 ・・・ Metal substrate 21 ・・・ Catalyst layer 31 ・・・ First composite catalyst particles 32 ・・・ Zirconia base material particles 32a ・・・ Surface 33 ・・・ CeO ₂ particles 41 ・・・ 2nd composite catalyst particles 42 ・・・ Alumina base material particles 42a ・・・ Surface 51 ・・・ Third composite catalyst particles 52 ・・・ Celia alumina base material particles 52a ・・・ Surface 61 ・・・ Fourth composite catalyst particles 62 ・・・ Celia alumina base metal particles 62a ・・・ Surface

Claims

An exhaust gas purification catalyst for saddle-type vehicles installed in the exhaust gas passage of an internal combustion engine.
A metal base material and a single-layer catalyst layer provided on the metal base material are provided.
The catalyst layer is
The first composite catalyst particles having at least the zirconia-based base material particles and the Rh and CeO2 particles co - supported on the surface of the zirconia-based base material particles, and
A second composite catalyst particle containing the alumina base material particles and Pd supported on the surface of the alumina base material particles, and / or the ceria alumina base material particles and Pd supported on the surface of the ceria alumina base material particles. Contains at least the third composite catalyst particles having
Exhaust gas purification catalyst for saddle-mounted vehicles.
The zirconia-based base material particles are rare earth solid-dissolved zirconia base material particles in which at least one or more rare earth elements selected from the group consisting of Ce, Nd, and La are solid-dissolved.
The exhaust gas purification catalyst for a saddle-mounted vehicle according to claim 1.
The zirconia-based base material particles contain 65 to 85% by mass of ZrO 2 and 15 to 35% by mass of an oxide of a rare earth element in terms of oxide.
The exhaust gas purification catalyst for a saddle-mounted vehicle according to claim 1 or 2.
The second composite catalyst particles include the alumina base material particles and Pd and Ba supported on the surface of the alumina base material particles.
The exhaust gas purification catalyst for a saddle-type vehicle according to any one of claims 1 to 3.
The ceria alumina base material particles of the third composite catalyst particles contain 70 to 90% by mass of Al 2 O 3 and 10 to 30% by mass of CeO 2 in terms of oxide.
The exhaust gas purification catalyst for a saddle-type vehicle according to any one of claims 1 to 4.
The catalyst layer further contains a ceria alumina base material particle and a fourth composite catalyst particle containing Rh supported on the surface of the ceria alumina base material particle.
The exhaust gas purification catalyst for a saddle-type vehicle according to any one of claims 1 to 5.
The coating amount of the catalyst layer is 1 to 200 g / L per 1 L of the metal substrate.
The exhaust gas purification catalyst for a saddle-type vehicle according to any one of claims 1 to 6.