JPH0771634B2 - Exhaust gas purifying catalyst and its manufacturing method - Google Patents

Description

The present invention relates to a catalyst for purifying diesel engine exhaust gas or industrial exhaust gas containing combustible carbon fine particles and a method for producing the same. In recent years, carbonaceous particulate matter (mainly consisting of solid carbon particulates, sulfur particulates such as sulfates, and liquid or solid high molecular weight hydrocarbon particulates) in diesel engine exhaust gas has become a problem for environmental hygiene. It is in. This is because these fine particles have a particle diameter of almost 1 micron or less and are easily suspended in the atmosphere and easily absorbed into the human body by absorption. Therefore, studies are underway in the direction of tightening regulations on the emission of these fine particles from diesel engines and the like.

[Conventional technology]

By the way, methods for removing these fine particles are roughly classified into the following two methods. One is a heat resistant gas filter (ceramic foam, wire mesh, metal foam, wall flow type ceramic honeycomb, etc.)
The exhaust gas is used to capture particulates, and if the pressure loss increases, the particulates accumulated by a burner are burned to regenerate the filter, and another carrier with this heat-resistant gas filter structure is used as a catalyst material. Is carried out and the combustion process is carried out together with the over-operation to reduce the frequency of the combustion regeneration, or the combustion activity of the catalyst is increased to the extent that regeneration is unnecessary.

In the case of the former, the higher the effect of removing fine particles, the faster the pressure loss rises, the more frequently the regeneration is performed, which is troublesome, and the economy will be significantly disadvantageous. On the other hand, the latter method is considered to be far superior if a catalytic substance capable of effectively maintaining the catalytic activity is adopted under the emission conditions (gas composition and temperature) of the diesel engine exhaust gas.

However, the exhaust gas temperature of the diesel engine is much lower than that of the gasoline engine, and the exhaust gas purifying catalyst having the ability to satisfactorily ignite and burn the particulates accumulated within the temperature obtained under normal engine running conditions. In spite of the requirement, the present situation is that no catalyst which meets this condition has been proposed so far.

Conventionally, the following various proposals have been made for the purpose of enhancing the capturing effect of carbon-based fine particles.

A structure comprising a mixture of a porous ceramic body having a three-dimensional network structure and a fiber having heat resistance, wherein the fiber is entangled in the skeleton of the porous ceramic body and its voids (JP-A-57). -84747), an exhaust gas purifying structure characterized in that a large number of protrusions in an irregular array are provided on the skeleton surface of various three-dimensional structures (Japanese Patent Laid-Open No. 57-99314). JP-A-57-99315,
JP-A-57-162650, JP-A-58-14921, etc.), a structure having a through hole has an acicular ratio of 5 to 1000 on the inner wall of the through hole, and the product of the diameter and the BET specific surface area is 2 [ μm · m ² / g] or more, a structure formed by adhering heat-resistant inorganic fibers (Japanese Patent Application Laid-Open No. 59-142820), in a ceramic filter, a fiber diameter of 0.1 to 1 μm and a fiber on the carrier surface of the ceramic filter. Length 10-200 μm
A ceramic filter for collecting fine particles, which comprises forming a ceramic coating layer containing 0.5 to 70% by weight of the fibrous inorganic substance (JP-A-60-106514).

Examples of using platinum group metal as a catalyst for burning carbon-based fine particles include rhodium 7.5% / platinum alloy, Pt /
A mixture of Pd = 50/50, palladium supported on tantalum oxide or cerium oxide, or an alloy composed of palladium and 75% by weight or less of platinum, etc.
ic fraction) has been proposed to be effective (JP-A-55-24597).

In addition, at least one supported material selected from the group consisting of noble metals, chromium and catalytically active compounds of these, and elements of the first transition series, silver, hafnium and catalytically active compounds of these. A composition comprising a catalytically effective amount of a mixture of at least one bulk material selected from the group consisting of compounds, the supported material being supported on a porous refractory inorganic oxide. (JP-A-57-24640), a catalyst for purifying carbon-based fine particles in which vanadium or a vanadium compound is combined with antimony, alkali metal, molybdenum, platinum, lanthanum (JP-A-58-174236), copper or A catalyst for purifying carbon-based fine particles, which is formed by combining molybdenum or vanadium with a copper compound, and also by combining platinum, rhodium, etc. (JP-A-59-82944). Platinum supported to 700 to 1000 ° C. in heat treated by suppressing the generation capacity of Sarufueto carbon-based particles purifying catalyst (JP 59
-36543), a catalyst for purifying carbon-based fine particles, which is a combination of palladium and at least one of rhodium, ruthenium, nickel, zinc, and titanium (Japanese Patent Laid-Open No. 59-80330), and the like have been proposed. .

However, when the platinum group element is used as a catalyst for burning carbon-based fine particles, the inventors of the present invention can sufficiently bring out the low-temperature ignitability of the carbon-based fine particles of the platinum-group element with the catalysts disclosed therein. Found difficult.

That is, in order to bring out the low-temperature ignitability of the carbon-based fine particles having the platinum group element, the contact-supporting layer is formed so as to increase the contact efficiency with respect to the carbon-based fine particles accumulated in layers on the gas contact surface or contact portion of the exhaust gas. It has been found that a practical catalyst having low-temperature ignitability can be proposed by supporting the particles in the form of protrusions and further imparting mechanical strength to the shape.

[Problems to be solved by the invention]

The inventors of the present invention propose a catalyst capable of burning carbon-based fine particles contained in exhaust gas from a diesel engine from a lower temperature, and a method for preparing the same.

The catalyst according to the present invention is highly evaluated in the following points. As described above, the exhaust gas temperature from the diesel engine is much lower than that of a gasoline vehicle, and the exhaust gas temperature during city driving does not reach 450 ° C even at the manifold outlet. Good catalysts are required.

However, conventionally proposed catalysts containing a platinum group, the catalyst component is supported in a layer in fine particles in the gas contact portion of the three-dimensional structure, or is supported on the inner pore inner wall surface of the aggregate, The present situation is that the efficiency of contact with the captured carbon-based fine particles is poor, and sufficient combustion performance cannot be derived from the catalytically active substance containing the platinum group.

Therefore, the present inventors have noticed that the carbon-based fine particles are accumulated in the gas contact portion wall surface or the gas contact portion in a layered manner, and the coarse particles of the catalytically active component are supported in a protrusion shape in the accumulation layer,
The inventors have found that the catalytic performance is remarkably enhanced by increasing the contact efficiency between the catalyst and the carbon-based fine particles, and the present invention has been completed.

[Means for solving problems]

 The present invention is specified as follows.

(1) On the gas contact surface or the gas contact portion of the refractory three-dimensional structure, a refractory inorganic powder having a particle diameter of 5 to 300 μm and a range of 1/300 to 1/5 of the average particle diameter of the inorganic powder A refractory inorganic fiber having an average diameter and an average length in the range of 1/10 to 20, the weight ratio of the inorganic powder and the inorganic fiber in the range of 1: 0.7 to 1: 0.07, the inorganic powder and The inorganic fiber is formed in a protrusion shape, and the refractory inorganic powder formed in the protrusion shape carries a catalytically active substance containing at least one platinum group element consisting of platinum, rhodium and palladium. An exhaust gas-purifying catalyst characterized by being used at most.

(2) The catalyst according to (1) above, wherein the refractory three-dimensional structure is a ceramic foam, a ceramic honeycomb, a wall flow type honeycomb monolith, a metal honeycomb, or a metal foam.

(3) The refractory inorganic powder is selected from the group consisting of activated alumina, silica, titania, zirconia, silica-alumina, alumina-zirconia, alumina-titania, silica-titania, silica-zirconia, titania-zirconia and zeolite. The catalyst according to (1) above, wherein the catalyst is at least one kind and has a particle size substantially distributed in a range of 5 to 300 μm.

(4) The refractory inorganic powder having a particle diameter of 5 to 300 μm and the range of 1/300 to 1/5 of the average particle diameter of the inorganic powder on the gas contact surface or the gas contact portion of the refractory three-dimensional structure. A refractory inorganic fiber having an average diameter and an average length in the range of 1/10 to 20, the weight ratio of the inorganic powder and the inorganic fiber in the range of 1: 0.7 to 1: 0.07, the inorganic powder and The inorganic fibers are formed in a protrusion shape, and the refractory inorganic powder formed in the protrusion shape includes at least one platinum group element consisting of platinum, rhodium and palladium, and iron, cobalt, nickel and molybdenum, Alkaline earth metal consisting of tungsten, niobium, phosphorus, lead, zinc, tin, copper, manganese, cerium, lanthanum, silver, barium, magnesium, calcium and strontium, alkali consisting of potassium, sodium, cesium and rubidium Exhaust gas purifying catalyst, characterized by comprising brought carrying a catalyst active substance comprising a least one member selected from the group consisting of the genus.

(5) The catalyst according to (4) above, wherein the refractory three-dimensional structure is a ceramic foam, a ceramic honeycomb, a wall flow type honeycomb monolith, a metal honeycomb or a metal foam.

(6) The refractory inorganic powder is selected from the group consisting of activated alumina, silica, titania, zirconia, silica-alumina, alumina-zirconia, alumina-titania, silica-titania, silica-zirconia, titania-zirconia and zeolite. The catalyst according to (4) above, which is at least one kind and has a particle diameter substantially distributed in a range of 5 to 300 μm.

(7) Particle size supporting catalytically active substance is 5-300μ
m of the refractory inorganic powder, and an average diameter in the range of 1/300 to 1/5 and 1/10 to 20 of the average particle diameter of the refractory inorganic powder.
A refractory inorganic fibrous substance having an average length in the range of, the weight ratio of the inorganic powder and the inorganic fiber is 1: 0.7 ~
Mixing in the range of 1: 0.07, and alumina sol, titania sol, zirconia sol, silica sol, soluble boehmite,
The inorganic powder is made into an aqueous slurry together with at least one dispersant selected from the group consisting of soluble organic polymer compounds, and the obtained slurry is used on the gas contact surface or the gas contact portion of the refractory three-dimensional structure. A method for producing an exhaust gas-purifying catalyst, characterized in that and the inorganic fibers are supported in a protrusion shape.

(8) The method according to (7) above, wherein the fire-resistant three-dimensional structure is a ceramic foam, a ceramic honeycomb, a wall-flow type honeycomb monolith, a metal honeycomb, or a metal foam.

The carbon-based fine particles are accumulated in a layer form in the gas contact portion of the three-dimensional structure, for example, a wall flow type honeycomb (in the gas flow direction, the plurality of flow pipes are alternately formed, the flow pipes are alternately opened, and the inlet portion is opened, A ceramic monolith composed of a flow pipe closed at the outlet and a flow pipe closed at the inlet and opened at the outlet, the flow pipe wall being formed of a porous partition wall having a gas filter mechanism. Honeycomb)
There are many pores in the partition walls, and when the gas passes through these pores, the carbon-based fine particles are passed through, but the average diameter of the pores is much larger than the diameter of the carbon-based fine particles. The fine particles form a bridging on the side wall surface of the pore inlet and accumulate in layers on the side wall surface of the gas inlet side. If the platinum group element-containing catalyst is present on the partition wall surface or on the aggregate in the partition wall pores,
When it is supported in layers without forming protrusions,
The contact efficiency of the catalytically active component with the accumulation of the carbon-based fine particles is poor and no preferable catalytic action is observed.

Therefore, in the present invention, the gas contact portion of the three-dimensional structure is characterized by supporting the platinum group element-containing catalyst composition in the form of protrusions to improve the contact efficiency and significantly improve the combustion efficiency of the carbon-based fine particles. There is.

As the three-dimensional structure, ceramic foam, ceramic honeycomb, for flow type honeycomb monolith, metal honeycomb, metal foam or the like is preferably used.

Examples of the refractory inorganic powder carrying a catalyst component such as a platinum group element include activated alumina, silica, titania, zirconia, silica-alumina, alumina-zirconia, alumina-titania, silica-titania, silica-zirconia, titania-zirconia. , Zeolite and the like are preferable.

Inorganic fibers include glass fibers, alumina fibers, silica fibers, silicon nitride (Si ₃ N ₄ ), silicon carbide (Si
C), potassium titanate, rock wool, zirconia,
Inorganic fibers such as titanium carbide, iron, nickel, tungsten, calcium innate or whiskers are preferably used. In addition, the refractory inorganic powder is preferably distributed in a particle size of 5 to 300 μm, and the inorganic fiber is 1/300 of the average particle size of the refractory inorganic powder.
~ 1/5, preferably 1 / 200-1 / 7 diameter and 1 / 10-20,
The fiber length of 1/5 to 15 is preferable, and the ratio is 1: 0.7 to 1: 0.07 with respect to the weight ratio of the refractory inorganic powder.

The wire diameter and length of the inorganic fiber have a strong correlation with the average particle diameter of the refractory inorganic powder used, and the wire diameter is 1 / of the average particle diameter.
300 to 1/5 is preferable, and those other than this range are preferable because if the wire diameter is too thin, the particles are simply entangled, or if they are too thick, they hinder the protrusion-like support. Absent.

The length of the fiber also correlates with the average particle diameter, preferably 1/10 to 20. Other than this range, if the length is too short, it simply fills the voids without particles, and is also too long. In this case, the dispersion with the particles becomes poor and lumps of only fibers are formed, which is not preferable.

The particle size of the inorganic powder or the inorganic powder containing the catalytically active component is preferably 5 to 300 μm, and when the particle size is 5 μm or less, the protrusions formed are small, and the effect of enhancing the contact efficiency with the carbon-based fine particles has not been found. . It has been found that when the thickness is larger than 300 μm, it is difficult to form the protrusions, and the contact area of the generated protrusions is reduced so that the combustion performance of the carbon-based fine particles is not so improved.

Further, the amount of the inorganic fiber used is preferably in the range of 1: 0.7 to 1: 0.07 with respect to the weight ratio of the inorganic powder, and when more than 1: 0.7 is used, it is necessary to form protrusions by particles. When it was less than 1: 0.07, the effect of addition was not observed, and the result was the same as when no inorganic fiber was used.

The catalyst preparation method according to the present invention is not specified, but the following method is mentioned as a preferable example.

An activated alumina pellet is impregnated and supported with an aqueous solution of a water-soluble salt of a catalytically active component, dried and calcined. Then, powder with a hammer mill (for example, PULVERIXER manufactured by Hosokawa Micron Co., Ltd.),
Classifying powder frame products (for example, MICRON SE manufactured by Hosokawa Micron Co., Ltd.
PARATOR, MS-O type) to obtain a catalytically active substance-supported powder in which a catalytic component such as platinum element is supported on refractory inorganic coarse particles having a particle size substantially in the range of 5 μm to 300 μm. .

Then, this powdery substance is used together with the inorganic fiber to be specified above, soluble boehmite (for example, DISPURAL manufactured by CONDEA).
Is added to an aqueous solution containing 1 to 20% by weight in terms of alumina (Al ₂ O ₃ ) and stirred. Due to the thickening effect of boehmite as a dispersant, a stable slurry can be obtained not only during stirring but also when the stirring is stopped, the granular active substance does not sediment.

By supporting the three-dimensional structure using the millary and removing the excess slurry, it is possible to form a protruding catalyst coating layer having large irregularities on the inner wall surface of the structure or the skeleton surface. Then dry and 200-800 ℃, especially 300-700 ℃
Bake at the temperature of.

When slurrying the coarse-particle catalytically active component in this preparation method, alumina having a thickening effect so that coarse particles do not settle, titania, zirconia, sol such as silica and soluble boehmite, from the group consisting of soluble organic polymer compounds It may be used in the form of an aqueous slurry together with at least one selected dispersant, and the soluble organic polymer compound may be sodium polyacrylate, ammonium polyacrylate, sodium salt of acrylic acid-maleic acid copolymer. Or ammonium salt, polyethylene oxide, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose,
Starch, gum arabic, guar gum, glue and the like are preferably used.

In order to make the catalyst coat layer more porous, a method of adding a soluble organic polymer compound such as polyethylene glycol to the slurry and removing it by firing may be used in combination.

In addition, as a preparation method suitable for the present invention, a granular material of a heat-resistant inorganic substance (having the same classified particle size as above) is previously loaded on a three-dimensional structure, and an aqueous solution of a catalytically active component or an organic solvent soluble A salt solution may be impregnated and supported for catalysis.

In the catalyst according to the present invention, the total supported amount including the catalytically active component is not particularly limited, but is in the range of 10 to 200 g, preferably 20 to 150 g per one-dimensional structure 1.

As a refractory inorganic powder, 5 per 3D structure 1
It is in the range of up to 150 g, preferably 10 to 120 g, and the inorganic fibers are used in a ratio of 1: 0.7 to 1: 0.07 with respect to the weight of the refractory inorganic powder.

The amount of the catalytically active component as an oxide or a metal is 0.01 to 70 g, preferably 0.05 to 50 g per one-dimensional structure 1.

[Operation] The combustion reaction of carbon-based fine particles is a solid-solid reaction,
The contact efficiency between the catalytically active substance and the carbon-based fine particles is a very important factor.

In view of this point, the present invention attaches a protrusion-shaped catalyst of a suitable size consisting of a catalytically active component, a refractory inorganic powder, and an inorganic fiber, and significantly increases the combustion efficiency by increasing the contact efficiency with the carbon-based fine particles. It is characterized by improving.

The action effect of the inorganic fibers in the protrusion-shaped catalyst is considered to prevent bridging of the carbon-based fine particles and further increase the contact efficiency with the catalytically active component, which is lower than that when no inorganic fibers are used. Then, they found that the carbon-based fine particles burned and completed the present invention.

Hereinafter, the present invention will be specifically described by showing Examples and Comparative Examples of the present invention.

Example 1 Commercially available activated alumina pellets (3-5 mmφ surface area 150 m ² /
g) Weigh out 2 kg, nitric acid solution of dinitrodiammine platinum containing 15 g as Pt, and 1.67 g as rhodium (Rh)
It was dipped and supported in a mixed solution 1.4 of the aqueous rhodium nitrate solution contained therein, dried at 150 ° C. for 3 hours, and calcined at 500 ° C. for 2 hours.

The fired pellets were framed with a hammer mill, and those having a particle size of 5 μm or less were cut by a classifier, and those having a particle size of 300 μm or more were removed using a decoration. By the above operation, a Pt: Rh-supported powder catalyst having an average particle diameter of 78 μm was obtained. 100g of soluble boehmite (75g of Al ₂ O ₃ equivalent)
1 kg of the classified powder catalyst was dispersed in an aqueous solution obtained by dissolving to obtain a stable slurry 2.

100 g of commercially available silicon carbide whiskers (wire diameter 1.7 μm, length 80 μm) were dispersed in the slurry while stirring.

The viscosity of this slurry was 91 cps (room temperature).

A commercially available open honeycomb monolith (material:
Cordierite) 5.66 inch diameter × 6.0 inch length, 300 cells / parallel inch, and wall thickness 6 mil were used.

The carrier was immersed in the slurry and pulled up to remove excess slurry by air blow. Then, it was dried at 150 ° C. for 3 hours and calcined in air at 500 ° C. for 2 hours to obtain a finished catalyst.

The loading amount of each component of the finished product is Al ₂ O ₃ 120 g / − carrier, Pt 0.
The carrier was 9 g / -carrier, Rh 0.1 g / -carrier, and silicon carbide whiskers 12 g / -carrier.

Example 2 Commercially available silica-alumina (13% alumina) pellets (3
～5Mmfai, an aqueous solution of diammine dinitro platinum nitric acid solution 20g contained in the surface area of 230m ² / g) 1kg of platinum (Pt) 750 meters
It was immersed in 1 l, dried at 150 ° C. for 3 hours, calcined at 500 ° C. for 2 hours, and then impregnated with 150 ml of an aqueous solution in which 371 g of lead nitrate [Pb (NO ₃ ) ₂ ] was dissolved. Dry at 150 ℃ for 3 hours, 500 ℃
It was baked for 2 hours. The fired pellets were powder-framed with a Panmer mill, and those having a particle size of 5 μm or less were cut by a classifier, and those having a particle size of 300 μm or more were removed using a decoration. By the above operation, a catalyst-containing powder catalyst having an average particle size of 82 μm was obtained. In advance, 150 g of the classified powder catalyst was dispersed in an aqueous solution containing 15 g of silica sol (Snowtex-O, manufactured by Nissan Kagaku) in terms of SiO ₂ , and then 10 g of commercially available glass fiber (diameter 13 μm, length 200 μm) was added. And dispersed with stirring to give 520 ml of a stable slurry. As the carrier, a commercially available wall-flow type honeycomb monolith (material: cordierite) 5.66 inch diameter × 6.0 inch length, 100 cells / square inch, wall thickness 17 mil, and partition walls having an average pore diameter of 28 μm were used. . 520 ml of the above slurry was poured from the gas inlet of the carrier, and excess slurry was removed by air blowing from the opposite side. Then at 150 ℃ 3
It was dried for an hour and calcined in air at 500 ° C. for 2 hours to obtain a finished catalyst. The amount of each finished component loaded is silica-alumina.
The carrier was 40 g / -carrier, PbO 10 g / -carrier, Pt 1.0 g / -carrier, and glass fiber 3.3 g / -carrier.

Example 3 In Example 1, instead of the open honeycomb monolith as the carrier, a commercially available ceramic foam (bulk density 0.35) was used.
A catalyst was prepared by the same method except using g / cm ³ , porosity 87.5%, and volume 1.7). The loading amount of each component of the finished product is Al ₂ O ₃ 120 g / − carrier, Pt 0.9 g / − carrier, Ph 0.1 g / −
The carrier was silicon carbide whiskers 12 g / -carrier.

Example 4 A catalyst having a catalyst composition shown in Table 1 below was obtained by the same method as in Examples 1 to 3.

Here, molybdenum was ammonium paramolybdate, phosphorus was ammonium dihydrogen phosphate, tungsten was ammonium paratungstate, niobium was pentachloride, and the others were nitrates.

Comparative Example 1 Commercially available activated alumina pellets (3-5 mmφ, surface area 150 m ²
1 g was weighed and immersed in 750 ml of an aqueous solution of nitric acid solution of dinitrodiammine platinum containing 20 g of platinum (Pt), dipped and supported, dried at 150 ° C. for 3 hours, and calcined at 500 ° C. for 2 hours.
The Pt-supported alumina pellets thus prepared were powder-framed, and then wet-milled to the extent that ordinary wash coating was performed with a wet mill to prepare a slurry having an average particle size of 0.9 μm, and 520 ml of slurry was obtained. 10 g of a commercially available alumina fiber (wire diameter 9 μm, length 900 μm) was added to the slurry while stirring and dispersed. A catalyst was prepared in the same manner except that Al ₂ O ₃ 50 g / -support, Pt 1.0 g / -support and alumina fiber 3.3 g / -support were completed.

Comparative Example 2 A catalyst was prepared in the same manner as in Example 1 except that silicon carbide whiskers were not used, and Al ₂ O ₃ 120
The finished catalyst of g / -support, Pt0.9g / -support and Rh0.1g / -support was obtained.

Comparative Example 3 A catalyst was prepared in the same manner as in Example 1 except that Pt and Rh were not used, and a finished catalyst of Al ₂ O ₃ 120 g / -support and silicon carbide whiskers 12 g / -support was obtained.

Lead nitrate Comparative Example 4 Example 2 [Pb (NO _{3) 2]} 371g of chromium nitrate instead of using _{[Cr (NO 3) 3 · 9H} 2 O ] except using 1316g is to prepare a catalyst in the same way the finished The amount of each component supported is silica-alumina 40 g / -carrier, Cr ₂ O ₃ 10 g /-
The carrier was Pt 1.0 g / -carrier, and glass fiber 3.3 g / -carrier.

Example 6 Regarding the catalysts obtained in Examples 1 to 4 and Comparative Examples 1 to 4,
A catalyst evaluation test was performed using a 2300cc 4-cylinder diesel engine. Engine speed 2500rpm,
Fine particles are captured for about 2 hours under the condition of a torque of 4.0 kg · m, and then the torque is increased at intervals of 0.5 kg · m every 5 minutes to continuously record the pressure loss change of the catalyst layer, and the fine particles are on the catalyst. The temperature at which the pressure rise due to the accumulation of fine particles and the pressure drop due to the combustion of fine particles become equal with the exhaust gas temperature rise (Te) and the temperature at which ignition loss occurs and the pressure loss drops sharply (Ti)
I asked. Further, the time-dependent change in pressure loss when trapping fine particles at 2500 rpm and a torque of 4.0 kg · m was calculated from the amount of pressure loss change per hour from the chart to obtain the value of ΔP (mmHg / Hr). Further, the amount of fine particles at the catalyst inlet and outlet of the fine particles was measured using a dilution tunnel under the fine particle capturing conditions of 2500 rpm and a torque of 4.0 kg · m to obtain the fine particle purification rate (%). The results are shown in Table 2.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location B01J 23/58 A 23/60 A 23/62 A 23/63 23/648 23/652 23/656 23/89 A 27/185 A B01J 23/64 102 A 103 A 104 A

Claims (8)

[Claims] 1. A refractory inorganic powder having a particle diameter of 5 to 300 μm and 1/300 to 1/5 of the average particle diameter of the inorganic powder on the gas contact surface or the gas contact portion of the refractory three-dimensional structure. A refractory inorganic fiber having an average diameter in the range and an average length in the range of 1/10 to 20, the weight ratio of the inorganic powder and the inorganic fiber in the range of 1: 0.7 to 1: 0.07, the inorganic A catalytically active substance comprising a powder and the inorganic fiber formed in a projection shape, and the refractory inorganic powder formed in the projection shape containing at least one platinum group element consisting of platinum, rhodium and palladium. An exhaust gas purifying catalyst, characterized in that 2. The catalyst according to claim 1, wherein the refractory three-dimensional structure is ceramic foam, ceramic honeycomb, wall flow type honeycomb monolith, metal honeycomb or metal foam. . 3. The refractory inorganic powder is selected from the group consisting of activated alumina, silica, titania, zirconia, silica-alumina, alumina-zirconia, alumina-titania, silica-titania, silica-zirconia, titania-zirconia and zeolite. The catalyst according to claim (1), characterized in that it is at least one kind and that its particle size is substantially distributed in the range of 5 to 300 μm. 4. A refractory inorganic powder having a particle diameter of 5 to 300 μm and 1/300 to 1/5 of the average particle diameter of the inorganic powder on the gas contact surface or the gas contact portion of the refractory three-dimensional structure. A refractory inorganic fiber having an average diameter in the range and an average length in the range of 1/10 to 20, the weight ratio of the inorganic powder and the inorganic fiber in the range of 1: 0.7 to 1: 0.07, the inorganic A powder and the inorganic fiber are formed in a projection shape, and the refractory inorganic powder formed in the projection shape includes at least one platinum group element consisting of platinum, rhodium and palladium, and iron, cobalt and nickel, Molybdenum, tungsten, niobium, phosphorus,
Lead, zinc, tin, copper, manganese, cerium, lanthanum,
Support a catalytically active substance containing at least one selected from the group consisting of alkaline earth metals consisting of silver, barium, magnesium, calcium and strontium, and alkali metals consisting of potassium, sodium, cesium and rubidium. An exhaust gas purifying catalyst characterized by: 5. The catalyst according to claim 4, wherein the refractory three-dimensional structure is ceramic foam, ceramic honeycomb, wall flow type honeycomb monolith, metal honeycomb or metal foam. . 6. The refractory inorganic powder is selected from the group consisting of activated alumina, silica, titania, zirconia, silica-alumina, alumina-zirconia, alumina-titania, silica-titania, silica-zirconia, titania-zirconia and zeolite. The catalyst according to claim (4), characterized in that it is at least one kind and that its particle size is substantially distributed in the range of 5 to 300 μm. 7. The particle size supporting the catalytically active substance is 5 to 5.
The refractory inorganic powder having a diameter of 300 μm, and the average diameter in the range of 1/300 to 1/5 of the average particle diameter of the refractory inorganic powder and 1 /
The refractory inorganic fibrous material having an average length in the range of 10 to 20, the weight ratio of the inorganic powder and the inorganic fiber is 1: 0.
Mixing in the range of 7 to 1: 0.07 and forming an aqueous slurry together with at least one dispersant selected from the group consisting of alumina sol, titania sol, zirconia sol, silica sol, soluble boehmite, and soluble organic polymer compound. A method for producing an exhaust gas-purifying catalyst, characterized in that the inorganic powder and the inorganic fibers are supported in the form of protrusions on the gas contact surface or the gas contact portion of the refractory three-dimensional structure using the slurry. 8. The method according to claim 7, wherein the refractory three-dimensional structure is a ceramic foam, a ceramic honeycomb, a wall flow type honeycomb monolith, a metal honeycomb or a metal foam. .