JPH05115790A - Material for cleaning exhaust gas and method for cleaning exhaust gas - Google Patents

Abstract

PURPOSE:To provide a material for cleaning exhaust gas, which acts effectively on an exhaust gas of high oxygen concentration containing particulates, hydrocarbon (hereafter called as HC), and NOx, and removes not only particulates and NOx but also HC and CO efficiently. CONSTITUTION:A material for cleaning exhaust gas comprises the first cleaning member composed mainly of porous ceramic installed at the inlet side of the exhaust gas and the second cleaning member composed of a heat resistant porous filter carrying a catalyst installed at the outlet side. The catalyst consists of (a) at least one kind of alkali metal, (b) at least one kind of element selected from a group of Cu, Co, Mn, Mo, and V, and (c) at least one kind of rare earth element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying material and an exhaust gas purifying method using the exhaust gas purifying material. More specifically, nitrogen oxide (hereinafter referred to as NOx) and particulate carbon in exhaust gas of a diesel engine or the like are used. The present invention relates to an exhaust gas purification material capable of simultaneously removing harmful components such as substances (hereinafter referred to as particulates), and an exhaust gas purification method using the exhaust gas purification material.

[0002]

2. Description of the Related Art In recent years,
Particulates, NO _X, etc. in the exhaust gas emitted from diesel engines are becoming a problem as environmentally harmful. In particular, particulates have an average particle size of 0.
Since it is easily suspended in the air at 1 to 1 μm, it is easily taken into the human body by respiration, and recent clinical test results confirm that it also contains a carcinogen.

As a method of removing particulates, the following two methods are roughly studied. One of them is a method to capture particulates by filtering the exhaust gas using a heat resistant filter, and burn the captured particulates with a burner, an electric heater, etc. to regenerate the filter if the pressure loss due to this is increased. Is. Examples of heat-resistant filters used include honeycomb-type ceramic filters, foam-type ceramic filters having a three-dimensional mesh structure, steel wool, and wire mesh. The other is a method in which the catalyst carried on the filter as described above acts to self-burn the particulates together with the filtering operation of the particulates.

In the former case, the higher the effect of removing particulates, the faster the pressure loss rises, the more frequently regeneration is required, the higher the reliability of regeneration required, and the more economically disadvantageous. On the other hand, the latter method is considered to be a far superior method if there is a catalyst that can retain the catalytic activity under the exhaust gas emission conditions (gas composition and temperature) of the diesel engine.

However, since the diesel engine uses light oil as a fuel, exhaust gas contains a large amount of SO ₂ .
Further, the oxygen concentration in the exhaust gas changes in a wide range of 5 to 15% depending on the operating condition of the diesel engine. A method of igniting particulates at low temperature using a filter with a precious metal or base metal oxidation catalyst has been proposed, but the particulates satisfactorily ignite and burn under exhaust gas conditions with high oxygen concentration, and secondary pollution A method of regenerating an exhaust gas purification filter that does not cause the above has not yet been established.

On the other hand, as a method for removing NOx in exhaust gas, a so-called three-way catalyst is used for exhaust gas of, for example, a gasoline engine, and NOx is harmless N ₂
The method of reducing to is adopted. However, in general, the NOx reduction reaction does not readily proceed in an atmosphere with a high oxygen concentration, so this three-way catalyst is used to reduce and remove NOx in exhaust gas with a high oxygen concentration discharged from diesel engines and the like. It can be said that the existing method is insufficient.

Under such circumstances, recently, a method proposed to remove NOx by adding gaseous or liquid hydrocarbons, light oil, alcohol, etc. has been proposed (SAE Pape
r 900496 (1990), JP-A-63-100919, etc.). However, a method that can efficiently remove particulates and NOx in exhaust gas at the same time has not been obtained.

For example, Japanese Patent Laid-Open No. 3-47589 discloses a heat-resistant porous filter having (a) an alkali metal and (b) an IB of the periodic table.
From one or more elements selected from the group consisting of Group VIII, IIB, VA, VIA, VIIA, VIII transition metals excluding platinum group elements and Sn and (c) rare earth elements The exhaust gas purifying material carrying the following catalyst is disclosed. In the method using this exhaust gas purification material, the particulates in the exhaust gas act as a reducing agent to reduce and remove NOx, and the particulates and NOx in the exhaust gas can be removed at the same time, but it is not always sufficiently efficient. It's hard to say.

Therefore, an object of the present invention is to have a high oxygen concentration,
Particulates, hydrocarbons (hereinafter referred to as HC), NOx
It effectively acts on the exhaust gas containing a mixture of particles, efficiently removes particulates and NOx, and reduces HC and CO.
It is an object of the present invention to provide an exhaust gas purifying material and an exhaust gas purifying method capable of satisfactorily removing carbon dioxide.

[0010]

Means for Solving the Problems As a result of earnest research on purification of exhaust gas having a composition in which particulates, HC, and NOx coexist, the inventors of the present invention reduce NOx using HC as a reducing agent on the inlet side. If a purifying material member for removal and a purifying material member for oxidizing particulates, HC and CO are used on the outlet side, that is, if two kinds of purifying material members having different functions are combined, good exhaust gas is obtained. The present invention has been completed by discovering that purification performance can be obtained.

That is, in the exhaust gas purifying material of the present invention, the first purifying material member mainly made of porous ceramics is installed on the inlet side, and the second purifying material member is formed by supporting the catalyst on the heat resistant porous filter. An exhaust gas purifying agent, which is installed on the outlet side, wherein the catalyst is selected from the group consisting of (a) one or more alkali metal elements and (b) Cu, Co, Mn, Mo and V. 1 or 2 or more of the selected elements and (c) 1 or 2 or more of the rare earth elements.

The exhaust gas purifying method of the present invention is a method for purifying exhaust gas using the exhaust gas purifying material, wherein hydrocarbon in exhaust gas mainly acts as a reducing agent in the first purifying material member. In addition to reducing nitrogen oxides, the catalyst in the second purification material member mainly oxidizes particulates, residual hydrocarbons and CO in the exhaust gas.

Further, in the exhaust gas purification method of the present invention, hydrocarbons are externally introduced into the exhaust gas on the upstream side of the first purification material member, and the introduced hydrocarbons act as a reducing agent to reduce nitrogen oxides. You may.

The present invention will be described in detail below. As the porous ceramics of the first purifying material member, one that effectively acts to reduce NOx by HC in an atmosphere with a high oxygen concentration is used. Examples of such porous ceramics include γ-alumina and its oxides (γ-alumina-titania, γ-alumina-silica, γ-alumina-zirconia, etc.), zirconia (66th Catalytic Discussion Group (A), 3L42
3 (1990)), and heat-resistant, large surface area, porous ceramics such as titania-zirconia. Further, since it is preferable that the first purifying material member has a small pressure loss and a small particulate collection performance, such a ceramic is used to form a honeycomb-shaped or foam-shaped molded body having a shape with a small pressure loss. It is preferable to put the pellets or pellets in the casing.

Further, in order to improve heat resistance, particularly heat shock resistance, it is practical to coat the above-mentioned porous ceramics on a heat resistant porous filter before use.

When a heat resistant porous filter (hereinafter referred to as a first filter) is used in the first purification material member, ceramics such as cordierite and mullite can be used as a material for forming such a filter. Further, since it is preferable that the first filter has a small pressure loss, it is preferable to use a honeycomb type or a foam type as its shape. Further, the shape and size of the first filter can be variously changed according to the purpose.

When a filter is used in the first purifying material member, the coating amount of the porous ceramics is preferably 8% by weight or more, particularly 10 to 15% by weight, based on the first filter.

As the filter (hereinafter referred to as the second filter) which is the base material of the second purifying material member, a filter having porosity and high heat resistance, particularly high thermal shock resistance, is used. Examples of such a filter-forming material include cordierite, mullite, alumina and oxides thereof (alumina-titania, alumina-silica, alumina-zirconia, etc.), ceramics such as zirconia, titania-zirconia, and the like.

As the second filter, it is preferable to use a honeycomb type or a foam type because the pressure loss is within an allowable range and the particulate collection performance is retained.

The catalyst supported on the second filter is (a) an alkali metal (Li, Na, K, Cs, etc.), and (b)
An element consisting of one or more elements selected from Cu, Co, Mn, Mo and V and (c) a rare earth element (Ce, La, Nd, Sm, etc.) is used. (a) As the alkali metal, at least one of sodium, potassium and cesium is used.
It is preferred to use seeds. Further, as the rare earth metal (c), it is preferable to use cerium, lanthanum, neodymium, or the like, and it is also possible to use misch metal which is a mixture of these rare earth metals.

In the present specification, the catalyst components (a) to
Although (c) and the catalyst component (d) described below are shown as metallic elements, the catalyst component (a) is not available under normal operating temperature conditions for purification materials.
~ (D) exists in an oxide state.

The above-mentioned catalyst components (a), (b) and (c) are blended in amounts of 10 to 50 parts by weight of (a) and 30 to 90 parts by weight of (b) in terms of their respective metal components. Parts, (c) is preferably 10 to 50 parts by weight. In particular, when V is selected as at least one of Cu, Co, Mn, and Mo as (b), the ratio of the metal element other than V to the V element is 5/1 to 1 / by weight. It should be around 15. If the amount of the alkali metal is less than 10 parts by weight or more than 50 parts by weight, the particulate removal property deteriorates. Further, if the amount of the component (b) is less than 30 parts by weight, the ignition characteristics of particulates are deteriorated, whereas if it exceeds 90 parts by weight, the combined effect is weakened and the characteristics of removing particulates and the simultaneous removal characteristics of particulates and NOx are reduced. .. Furthermore, when V is selected, the ratio of the metal element other than V and the V element is 5
If it exceeds / 1, the sulfur resistance will deteriorate, and if it is less than 1/15, the removal characteristics of particulates, particulates and NO
The simultaneous removal property of x is deteriorated. Further, if the amount of the component (c) is less than 10 parts by weight or more than 50 parts by weight, the particulate removal property deteriorates. A preferable composition range is 15 to 30 parts by weight of (a), 40 to 80 parts by weight of (b), and 15 to 30 parts by weight of (c).

Further, the amount of the catalyst (total amount of (a) + (b) + (c)) is 6% by weight or more based on the standard (100% by weight) when a carrier layer made of ceramics described later is used. It is particularly preferably 8 to 200% by weight. If the supported amount of the catalyst is less than 3% by weight with respect to the carrier layer, the effect of supporting the catalyst is not remarkable, and the oxidation characteristics of particulates, Co and residual hydrocarbons deteriorate. On the other hand, if the amount of catalyst supported exceeds 200% by weight, it becomes difficult to coat the filter, so the upper limit is set to 200% by weight.

In order to further enhance the oxidation characteristics of the catalyst, it is preferable to use a catalyst component (d) containing a platinum group element having high oxidizing ability in addition to the above catalyst components (a), (b) and (c). ..
The catalyst component (d) may be Pt, Pd or Rh, or a mixed catalyst of Pt and Pd, a mixed catalyst of Pt and Rh, a mixed catalyst of Pd and Rh, and further a mixed catalyst of Pt, Pd and Rh. It may be used as a catalyst. In addition to the above platinum group-based catalyst, Au and / or
Alternatively, it may contain Ag. Thus, the purification characteristics can be further improved by further adding Au and / or Ag to the catalyst containing the platinum group element.

The amount (total amount) of the catalyst component (d) is preferably 0.1 to 1% by weight based on this (100% by weight) when a carrier layer made of ceramics described below is used. When Au and / or Ag is contained, the platinum group element
50 parts by weight or less of Au and / or Ag per 100 parts by weight, especially 10
It is preferably about 20 parts by weight.

The components (a), (b) and
(c) and the catalyst component (d) as a method of supporting two systems of catalyst components on the second filter, using a single second filter, the catalyst component (a), ( Although the method of carrying catalyst components (d) in a stacked manner after carrying b) and (c) may be adopted, two catalyst components of two systems are used for the second filter (that It is also possible to use a method in which the second purification material member is formed by laminating these filters on the first filter and the second filter (second), respectively.

Further, in order to increase the supported area of the catalyst, the catalyst is indirectly supported on the second filter through a carrier layer made of ceramics which is more porous and has a larger surface area than the second filter. preferable.

To carry the above-mentioned catalyst on the second filter, after forming a carrier layer made of ceramics which is more porous and has a larger surface area than the second filter on the second filter, this carrier layer is supported. To do. As the material for forming the carrier layer, the same material as the above-mentioned porous ceramics of the first purification material member is used.

The amount of carrier layer carrying the catalyst is, in the case of a ceramic filter, 5 to 20% by weight of the second filter, in particular
It is preferably 10 to 15% by weight.

When the first filter is used for the first purifying material member, the volume ratio of the first filter to the second filter is 1: 4 to 4: 1, especially 1: 2 to 2 It is preferably: 1.

The formation of the layer made of porous ceramics in the case of using the first filter in the first purification member can be made common with the formation of the carrier layer made of porous ceramics in the second purification member. The formation of the carrier layer and the loading of the catalyst will be collectively described below.

The carrier layer made of ceramics can be formed by a wash coat method or a sol-gel method. The wash coating method is a method of forming a carrier layer on the filter by immersing the filter in the slurry of the above-mentioned porous ceramic and drying it.

When this method is used, the catalytically active species can be supported by an impregnation method or the like after the formation of the ceramic layer to be the carrier layer. However, the washcoat method is carried out using the ceramic powder pre-impregnated with the catalyst. For example,
The carrier layer supporting the catalyst can be formed by a single treatment.

The formation of the carrier layer by the sol-gel method is performed as follows. After hydrolyzing an organic salt of a metal (for example, an alkoxide) forming the ceramics for the carrier layer, the obtained sol is coated on a filter, and a film of colloidal particles is formed by contact with steam or the like, followed by drying and firing. To form a catalyst carrier layer on the filter. For example, when titania (TiO ₂ ) is used as the ceramics for the carrier layer, first, an alkoxide of Ti (for example, Ti (O-isoC ₃ H
₇ ) In the alcohol solution of ₄ ), add CH ₃ COOH, HNO ₃ and HCl.
To produce a coating solution to which an acid such as is added. The filter is dipped in this coating solution, pulled up, and then reacted with water vapor or water to cause gelation. Next, when the filter is dried and fired, a titania film is formed on the pore surface of the filter. In the sol-gel method, an acid is added as a catalyst for the hydrolysis reaction at the time of gelation, but the hydrolysis reaction can be promoted by adding an alkali instead of the acid.

Although titania has been described as an example of the carrier layer ceramics in the above, other ceramics can be similarly supported by the sol-gel method. For example, when forming a carrier layer of alumina, aluminum alkoxide is used, and the same method as in the case of titania described above is performed. The same applies when other porous carriers are used.

After the porous carrier layer made of ceramics such as titania is formed on the filter by the above-mentioned wash-coat method or sol-gel method, the catalytically active species carbonate, nitrate, acetate, and hydroxide are next prepared. The carrier layer is impregnated with an aqueous solution of a substance or the like, dried and baked again to support the catalyst.
As the salt of the catalytically active metal species, any kind of salt such as carbonate, nitrate, acetate, hydroxide, etc. can be used as long as it is soluble in water. For loading V, a solution of NH ₄ VO ₃ and oxalic acid can be used. In addition, alkali molybdate and / or vanadate is used, and alkali metal and Mo and / or V
It is also possible to simultaneously support and.

Further, regarding the catalyst component (d) of the platinum group element, chlorides of platinum group elements such as Pt, Pd, Rh, Au and / or
The carrier layer is impregnated with an aqueous solution of Ag chloride or the like, dried and calcined to support the catalyst.

Furthermore, when a filter immersed in an aqueous solution of chloride such as Pt, Pd, Rh, etc. is irradiated with light, the catalyst can be supported very effectively. A method is also possible in which a platinum group element-based catalyst is first supported on a titania-based carrier by light irradiation and the titania-based carrier is coated on a filter. By using this light irradiation, the catalyst fixed on the titania-based carrier with a high degree of dispersion can be thinly coated on the filter, and the pressure loss can be suppressed to be small.

The above-mentioned first purification material member is installed on the exhaust gas inlet side, and the second purification material member is installed on the outlet side to manufacture the exhaust gas purification material.

In the method of the present invention, NOx in the exhaust gas is reduced and removed by HC using the first purification member having the above-mentioned structure. However, since the HC in the exhaust gas mainly consists of methane, ethylene, acetylene, etc., NOx reduction temperature is 200
~ 500 ° C, preferably 250-450 ° C, NOx
The reduction of can occur efficiently. If the reaction temperature is too high, HC
Combustion of itself occurs and NOx reduction characteristics deteriorate. In addition,
In the method of the present invention, H that acts as a reducing agent in the exhaust gas
When the amount of C is small, it is possible to forcibly introduce HC such as ethylene, propane, and propylene, which is necessary and sufficient for reducing NOx, upstream of the first purification member.

By using the first purification member having the above structure, NOx in the exhaust gas can be removed efficiently. That is, when HC coexists with the above-mentioned porous ceramics and oxygen in the first purification member, HC acts as a reducing agent to reduce NOx, and NOx can be efficiently removed.

Further, by using the second purification material member having the above-mentioned catalyst, it is possible to ignite and burn the particulates in the exhaust gas at a relatively low temperature. That is, since the particulates in the exhaust gas coexist in the second filter with the above-mentioned catalyst element and oxygen, the ignition temperature is lowered, and the particulates are burned (oxidized) at about 400 ° C. or lower. In addition to the particulates, residual HC and CO are efficiently oxidized by the catalyst element, so that the particulates, HC and CO can be efficiently removed.

Thus, by combining two kinds of purification material members, that is, NOx is reduced by using HC as a reducing agent in the first purification material member on the inlet side, and then the second purification material on the outlet side. By burning the particulates at a low temperature in the material member and oxidizing HC and CO, it is possible to efficiently remove NOx and particulates at the same time, and it is possible to remove HC and CO satisfactorily.

[0044]

The present invention will be described in more detail by the following specific examples. In the following Examples and Comparative Examples, each catalyst component is simply represented as each metal element.

Example 1 A first filter (apparent volume 1 liter, density 0.35 g / ml) made of cordierite foam was first coated with γ-Al ₂ O ₃ (surface area 200 m ² / g) by a washcoat method. The first filter was coated with 15% (weight%, the same applies hereinafter), dried, and fired at 700 ° C. to obtain a first purification material member.

On the other hand, a second filter made of cordierite foam (apparent volume 1 liter, density 0.65 g /
ml) by washcoat method with TiO ₂ (surface area 40 m
² / g) was 10% coated on the second filter. TiO
Cs, Cu, La and V are respectively added to the second filter coated with ₂ by using an aqueous solution of CsNO ₃ , CuCl ₂ and La (NO ₃ ) ₃ and a mixed aqueous solution of NH ₄ VO ₃ and oxalic acid. Ti O ₂
Was impregnated with 3%, dried, and fired at 700 ° C. to obtain a second purifying material member.

The obtained first purification material member was installed on the inlet side of the exhaust gas, and the second purification material member was installed on the outlet side to obtain a purification material. _{(Al 2 O 3 - Cs,} Cu, V, La / TiO 2: Example 1)

With respect to this purifying material, a diesel engine with a displacement of 500 cc was used, and the temperature at which the particulates were ignited and burned to regenerate the filter (the temperature at which the pressure loss decreased, hereinafter simply referred to as "regeneration temperature") The NOx purification rate at the regeneration temperature and higher temperatures was calculated. The engine was operated at a rotation speed of 2500 rpm, a load of 80%, and propylene was introduced from the outside to the upstream side of the first purification material member. The HC (including HC introduced from outside) in the exhaust gas under these operating conditions is 800 pp in total of all hydrocarbons.
m, CO 300ppm, NOx 480ppm, O ₂ 10% and SO ₂
Was 100 ppm. The results are shown in Table 1.

Example 2 15% of TiO ₂ —ZrO ₂ was coated on the same first filter as in Example 1 by the sol-gel method, and after drying, 700
Firing was performed at 0 ° C. to obtain a first purification material member.

On the other hand, by the washcoat method, TiO ₂
Was coated 10% on the same second filter as in Example 1. The second filter coated with TiO ₂ has CsNO ₃ , Cu
Cs, Cu, V and Ce were respectively added using Cl ₂ and Ce (NO ₃ ) ₃ aqueous solutions and NH ₄ VO ₃ and oxalic acid mixed aqueous solutions.
3% each was impregnated into TiO ₂ , dried, and then baked at 700 ° C to obtain a second purification material member.

The first purification material member and the second purification material member thus obtained were installed in the same manner as in Example 1 to obtain a purification material. _{((TiO 2 -ZrO 2) -} Cs, Cu, V, Ce / TiO 2: Example 2) In this exhaust gas purification material was determined to regeneration temperature and the NOx purification rate in the same manner as in Example 1. The results are shown in Table 1.

Example 3 15% of γ-Al ₂ O ₃ was coated on the same first filter as in Example 1 by the wash coating method, and after drying, 700
Firing was performed at 0 ° C. to obtain a first purification material member.

On the other hand, by the washcoat method, TiO ₂
Was applied to the same second filter as in Example 1 by 10%, dried and then baked at 700 ° C. A second filter coated with TiO _2, using aqueous solutions of K ₂ CO _3, CuCl _2, ammonium molybdate and _{La (NO 3) 3, K} , C
u, Mo and La were each impregnated in TiO ₂ by 3%, dried, and fired at 700 ° C. to obtain a second purification material member.

The first purification material member and the second purification material member thus obtained were installed in the same manner as in Example 1 to obtain a purification material. _{(Al 2 O 3 - K,} Cu, Mo, La / TiO 2: Example 3) In this exhaust gas purification material was determined to regeneration temperature and the NOx purification rate in the same manner as in Example 1. The results are shown in Table 1.

Table 1 NOx purification rate ⁽¹⁾ Example No. Regeneration temperature (° C) (Regeneration temperature) (450 ° C) Example 1 400 30 40 Example 2 405 20 30 Example 3 410 25 35 Note (1): NOx purification rate (%) calculated from the amount of NOx in the exhaust gas before and after passing through the filter

Example 4 In the same manner as in Example 1, a first purifying material member was obtained.

On the other hand, a second filter (part 1) made of cordierite foam (apparent volume 1 liter,
The density was 0.65 g / ml), and 10% of the second filter (No. 1) was coated with TiO ₂ by the wash coating method. T
CsN was added to the second filter (1) coated with iO _2.
O ₃ , Cu (NO ₃ ) ₂ and La (NO ₃ ) ₃ aqueous solutions and N
Using a mixed aqueous solution of H ₄ VO ₃ and oxalic acid, Cs, Cu, V
And La each impregnated with 3% of TiO ₂ and dried,
It was fired at 700 ° C to obtain a second purification material member (No. 1).

Further, a second filter (part 2) made of cordierite foam (apparent volume 0.2 liter, density 0.65 g / ml) was applied to the γ-A by washcoat method.
l ₂ O ₃ was 10% coated on the second filter (Part 2). γ-Al ₂ O ₃ to a second filter coated with (Part 2), H ₂ and Pt using an aqueous solution of PtCl ₆ γ-Al ₂ O
₃ % was impregnated with 0.1%, dried, and then baked at 700 ° C. to obtain a second purification material member (No. 2).

The obtained first purifying material member, the second purifying material member (1) and the second purifying material member (2) were
The purification material was obtained by installing the exhaust gas flow in the order from the inlet side to the outlet side. _{(Al 2 O 3 - Cs,} Cu, V, La / TiO 2 - Pt / Al 2 O
₃ : Example 4) The regeneration temperature of this purification material was determined in the same manner as in Example 1. Also, the NOx purification rate, HC purification rate and CO purification rate at the regeneration temperature were obtained. The results are shown in Table 2.

Example 5 A first purification member was obtained in the same manner as in Example 2.

On the other hand, by the washcoat method, TiO ₂
Was coated 10% on the same second filter as in Example 1. The second filter coated with TiO ₂ has CsNO ₃ , Cu
(NO _{3) 2,} ammonium molybdate and Ce (NO ₃₎
Cs, Cu, Mo and Ce are added to Ti using the aqueous solutions of ₃ respectively.
Impregnated against O ₂ by 3%, further to the second filter, a Pt using an aqueous solution of H ₂ PtCl ₆ against Ti O ₂
It was impregnated with 0.1%, dried, and fired at 700 ° C. to obtain a second purifying material member.

The first purification material member and the second purification material member thus obtained were installed in the same manner as in Example 1 to obtain a purification material. ((TiO ₂ −ZrO ₂ ) − Cs, Cu, Mo, Ce / Pt / TiO
₂ : Example 5) With respect to this purification material, the regeneration temperature, the NOx purification rate, the HC purification rate and the CO purification rate were determined in the same manner as in Example 4. The results are shown in Table 2.

Example 6 15% of γ-Al ₂ O ₃ was coated on the same first filter as in Example 1 by the wash coating method, and after drying, 700
Firing was performed at 0 ° C. to obtain a first purification material member.

On the other hand, by the washcoat method, TiO ₂
Was coated 10% on the same second filter as in Example 1. On the second filter coated with TiO ₂ , KNO ₃ , Cu
Using each aqueous solution of (NO ₃ ) ₂ and La (NO ₃ ) ₃ and a mixed aqueous solution of NH ₄ VO ₃ and oxalic acid, K, Cu, V and La were impregnated with TiO ₂ by 3%, respectively. Further, this second filter is impregnated with 0.1% of Pt and 0.01% of Rh by using each aqueous solution of H ₂ PtCl ₆ and RhCl ₃ and dried at 700 ° C.
Then, the second purification material member was obtained.

The first purification material member and the second purification material member thus obtained were installed in the same manner as in Example 1 to obtain a purification material. _{(Al 2 O 3 -K, Cu} , V, La / Pt, Rh / TiO 2: Example 6) The purification material may, regeneration temperature and NOx purification rate in the same manner as in Example 4, HC purifying ratio and CO The purification rate was calculated. The results are shown in Table 2.

Table 2 Example No. Regeneration temperature NOx purification rate ⁽¹⁾ CO purification rate ⁽²⁾ HC purification rate ⁽³⁾ Example 4 350 30 55 60 Example 5 380 22 56 60 Example 6 395 25 70 75

Note (1): NOx purification rate (%) calculated from the NOx amount in the exhaust gas before and after passing through the filter (2): Calculated from the amount of CO in the exhaust gas before and after passing through the filter CO purification rate (%) (3): HC purification rate (%) calculated from the amount of HC in the exhaust gas before and after passing through the filter

As is clear from Tables 1 and 2, the exhaust gas purifying materials of Examples 1 to 6 have good exhaust gas purifying performance.

[0069]

As described above, when the exhaust gas purifying material of the present invention is used, particulates and NOx can be efficiently removed. It also has an excellent effect on the purification of CO and HC. Such an exhaust gas purifying material is suitable for purifying exhaust gas having a relatively high oxygen concentration, such as a diesel engine.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B01J 23/88 A 8017-4G 23/89 A 8017-4G F01N 3/02 301 B 7910-3G E 7910-3G 3/10 A 7910-3G (72) Inventor Satoshi Kakuya 4-14-1, Suehiro, Kumagaya, Saitama Prefecture Riken Kumagaya Works (72) Inventor Masashi Mochida 4-14, Suehiro, Kumagaya, Saitama Prefecture No. 1 stock company Riken Kumagaya Works

Claims (5)

[Claims] 1. A first purification material member mainly made of porous ceramics is installed on the inlet side, and a second purification material member having a catalyst supported on a heat resistant porous filter is installed on the outlet side. An exhaust gas purifying material comprising: (a) one or more alkali metal elements, and (b) Cu, Co, M
One or two elements selected from the group consisting of n, Mo and V
An exhaust gas purification material comprising one or more kinds and (c) one or more kinds of rare earth elements. 2. The exhaust gas purifying material according to claim 1, wherein the catalyst further contains (d) a platinum group element. 3. The exhaust gas purifying material according to claim 1, wherein the porous ceramic is Al ₂ O.
₃ , Al ₂ O ₃ based complex oxide, TiO ₂ , ZrO ₂ , or TiO
An exhaust gas purifying material characterized by comprising any one of _2- ZrO ₂ . 4. A method for purifying exhaust gas using the exhaust gas purifying material according to claim 1, wherein hydrocarbons in the exhaust gas are mainly reduced in the first purifying material member. An exhaust gas purification method characterized in that it acts as an agent to reduce nitrogen oxides, and at the same time mainly oxidizes particulates, residual hydrocarbons and CO in exhaust gas by a catalyst in the second purification material member. 5. The exhaust gas purification method according to claim 4, wherein hydrocarbons are introduced into the exhaust gas from the outside on the upstream side of the first purification material member.