JPH0824583A - Exhaust gas purifying material and method for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To provide an exhaust gas purifying material capable of efficiently reducing and removing nitrogen oxide and also oxidizing and removing carbon monoxide and a hydrocarbon from combustion exhaust gas containing oxygen much more than the quantity of theoretical reaction with nitrogen oxide or unburnt portion such as carbon monoxide. CONSTITUTION:Nitrogen oxide is reduced and removed by using the exhaust gas purifying material composed of a 1st catalyst, which is obtained by making (a) a silver component and (b) at least one kind of element selected from a group composed of Pt, Pd, Ru, Rh, Ir and Au supported with a porous inorganic oxide, and a 2nd catalyst, which is obtained by making (c) an oxide of at least one kind of an element selected from a group composed of W, V, Mn, Mo, Nb and Ta and (d) at least one kind of an element selected from a group composed of Pt, Pd, Ru, Rh, Ir and Au supported with the porous inorganic oxide, and adding a hydrocarbon and/or an oxygen containing organic compound as a reducing agent from the outside to the exhaust gas.

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 for effectively removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and excess oxygen, and a purification method using the same.

[0002]

2. Description of the Related Art Excessive combustion exhaust gas discharged from internal combustion engines such as automobile engines, combustion equipment installed in factories, household fan heaters, and the like is excessive. It contains nitrogen oxides such as nitric oxide and nitrogen dioxide together with oxygen. Here, "containing excess oxygen" means that the exhaust gas contains more oxygen than the theoretical amount of oxygen necessary to burn unburned components such as carbon monoxide, hydrogen, and hydrocarbons. I do. In the following, nitrogen oxide refers to nitric oxide and / or nitrogen dioxide.

[0003] This nitrogen oxide is one of the causes of acid rain and is a major environmental problem. Therefore, various methods for removing nitrogen oxides in exhaust gas discharged from various combustion equipments are being studied.

[0004] As a method for removing nitrogen oxides from a combustion exhaust gas containing excess oxygen, a selective catalytic reduction method using ammonia is used particularly for a large-scale fixed combustion device (a large-scale combustor in a factory or the like). Has been put to practical use.

However, in this method, ammonia used as a reducing agent for nitrogen oxides is expensive, and ammonia is toxic. Therefore, the nitrogen oxides in the exhaust gas must be removed so that unreacted ammonia is not discharged. There are problems that the amount of injected ammonia must be controlled while measuring the concentration, and that the apparatus generally becomes large.

As another method, there is a non-selective catalytic reduction method in which a nitrogen oxide is reduced by using a gas such as hydrogen, carbon monoxide, or a hydrocarbon as a reducing agent. In order to reduce and remove nitrogen oxides, it is necessary to add a reducing agent in an amount equal to or more than a theoretical reaction amount with oxygen in exhaust gas, and there is a disadvantage that a large amount of the reducing agent is consumed. For this reason, the non-selective catalytic reduction method is practically effective only for exhaust gas having a low residual oxygen concentration burned near the stoichiometric air-fuel ratio, and is not practical because of poor versatility.

In view of the above, a method has been proposed for removing nitrogen oxides by using a zeolite or a catalyst supporting a transition metal on the zeolite and adding a reducing agent having a theoretical reaction amount or less with oxygen in the exhaust gas (for example, Japanese Patent Application Laid-Open Publication No. H11-163873). No.63-100919, 63-28372
No. 7, JP-A No. 1-130735 and the 59th Annual Meeting of the Chemical Society of Japan
(1990) 2A526, 60th Autumn Meeting (1990) 3L420, 3L422
, 3L423, "Catalyst" vol.33 No.2, p.59, 1991, etc.).

However, it has been found that in these methods, the temperature range for removing nitrogen oxides is narrow, and in the case of exhaust gas containing water, the removal rate of nitrogen oxides is significantly reduced. Therefore, the present inventors have provided a silver-based catalyst on the inflow side of the exhaust gas and a platinum-based catalyst on the outflow side. A purifying material that can also remove hydrocarbons has been previously proposed (Japanese Patent Application No. 4-328895). However, the removal rate of nitrogen oxides and the like at a high space velocity is not yet sufficient.

Accordingly, it is an object of the present invention to provide a method for producing nitrogen oxides, carbon monoxide, hydrogen, hydrocarbons and the like, such as combustion exhaust gas from a fixed combustion device and a gasoline engine, a diesel engine or the like, which burns under oxygen excess conditions. From combustion exhaust gas containing more than the theoretical reaction amount for unburned components,
An object of the present invention is to provide an exhaust gas purifying material and an exhaust gas purifying method capable of efficiently removing nitrogen oxides and oxidizing and removing residual and unreacted carbon monoxide and hydrocarbons.

[0010]

Means for Solving the Problems In view of the above-mentioned problems, as a result of intensive studies, the present inventor has found that a porous inorganic oxide carries (a) a silver component and (b) a platinum component on a catalyst. It has been found that an organic compound such as ethanol reacts with an exhaust gas containing oxygen and nitrogen oxides to reduce nitrogen oxides to nitrogen gas and to generate a nitrogen-containing compound such as ammonia as a by-product. The silver-based catalyst is formed by combining a (c) W, V-based component capable of reducing nitrogen oxides with a nitrogen-containing compound such as ammonia as a reducing agent and a catalyst supporting (d) a platinum-based component. Using an exhaust gas purifying material, a hydrocarbon and an oxygen-containing organic compound having 2 or more carbon atoms or a fuel containing them are added to the exhaust gas, and the exhaust gas is brought into contact with the purifying material at a specific temperature and space velocity. For example, they have found that nitrogen oxides can be effectively removed over a wide temperature range even with exhaust gas containing 10% moisture, and the present invention has been completed.

That is, while reducing and removing nitrogen oxides from a flue gas containing nitrogen oxides and oxygen in excess of the theoretical reaction amount for coexisting unburned components, residual and unreacted carbon monoxide and hydrocarbons are also oxidized. The exhaust gas purifying material of the present invention to be removed comprises (1) a porous inorganic oxide, (a) 0.2 to 15% by weight (element conversion value) of silver and / or a silver compound of the inorganic oxide, or a mixture thereof. (B) 1% by weight or less (in terms of element) of Pt, Pd,
At least one selected from the group consisting of Ru, Rh, Ir, and Au
A first catalyst carrying a seed element, and (2) a porous inorganic oxide containing (c) 10% by weight or less (in terms of metal element) of W, V, Mn, Mo, Nb and T
an oxide of at least one element selected from the group consisting of P, Pd, Pd, Ru, Rh, Ir and Au in an amount of 5% by weight or less (element conversion value) of the inorganic oxide; And a second catalyst supporting at least one selected element.

In addition, nitrogen oxides are reduced and removed from a combustion exhaust gas containing nitrogen oxides and oxygen in excess of the theoretical reaction amount for coexisting unburned components, and residual and unreacted carbon monoxide and hydrocarbons are also oxidized. In the exhaust gas purifying method of the present invention, the exhaust gas purifying material is provided in the middle of an exhaust gas conduit, the exhaust gas purifying material is provided in the middle of the exhaust gas conduit, and the hydrocarbon and / or carbon number is upstream of the purifying material. 2
The exhaust gas to which the oxygen-containing organic compound or the fuel containing the above is added is brought into contact with the purification material at 150 to 650 ° C., thereby removing the nitrogen oxides by reaction with the oxygen-containing organic compound in the exhaust gas. In addition, residual and unreacted carbon monoxide and hydrocarbons are oxidized and removed.

Hereinafter, the present invention will be described in detail. In the present invention, (1) a porous inorganic oxide is mixed with (a) 0.2 to 15% by weight (in terms of element) of silver and / or a silver compound of the inorganic oxide or a mixture thereof; A) a first catalyst which supports at least one element selected from the group consisting of Pt, Pd, Ru, Rh, Ir and Au in an amount of 1% by weight or less (in terms of element) of the inorganic oxide; , (2) at least one member selected from the group consisting of W, V, Mn, Mo, Nb and Ta in which (c) 10% by weight or less (in terms of metal element) of the inorganic oxide is added to the porous inorganic oxide; (D) an oxide of the element
Pt, P of 5% by weight or less (element conversion value) of the inorganic oxide
d, an exhaust gas purifying material comprising a second catalyst carrying at least one element selected from the group consisting of Ru, Rh, Ir and Au, and installing the purifying material in an exhaust gas conduit; On the more upstream side, an exhaust gas to which a hydrocarbon and any of oxygen-containing organic compounds having 2 or more carbon atoms or a fuel containing the same is added is brought into contact with the purifying material to reduce and remove nitrogen oxides in the exhaust gas. In the present invention, the first catalyst and the second catalyst are used in combination, but it is preferable to arrange the first catalyst on the exhaust gas inflow side and the second catalyst on the outflow side. With this arrangement, nitrogen oxides can be effectively reduced and removed in a wide exhaust gas temperature range.

In a first preferred embodiment of the exhaust gas purifying material of the present invention, a purifying material substrate is coated with first and second catalysts each having a catalytically active species supported on a powdery porous inorganic oxide. Or a purification material obtained by coating a purification material substrate with a powdery porous inorganic oxide and then carrying a catalytically active species. Examples of the ceramic material forming the substrate of the purifying material include porous materials such as γ-alumina and its composite oxides (γ-alumina-titania, γ-alumina-silica, γ-alumina-zirconia, etc.), zirconia, titania-zirconia, etc. And a heat-resistant material having a large surface area. When high heat resistance is required, it is preferable to use cordierite, mullite, alumina, a composite thereof, and the like. In addition, a known metal material can be used for the base of the exhaust gas purifying material.

The shape and size of the substrate of the exhaust gas purifying material
Various changes can be made according to the purpose. In addition, the base body is the entrance part,
Two or more parts such as an outlet part can be used in combination. Examples of the structure of the substrate include a honeycomb structure type, a foam type, a three-dimensional network structure type formed of a fibrous refractory, a granular shape, a pellet shape, and the like. The first catalyst and the second catalyst may be coated on different positions on the same substrate, or may be used in combination after being coated on different substrates.

In a second preferred embodiment of the exhaust gas purifying material of the present invention, a catalyst having a catalytically active species supported on a pellet, granular or powdery porous inorganic oxide is filled in a casing having a desired shape. Purification material.

The following two catalysts are formed on the purifying material of the present invention. (1) First catalyst The first catalyst comprises (a) silver and / or a silver compound or a mixture thereof, and (b) Pt, Pd, Ru, Rh,
It supports at least one metal element selected from the group consisting of Ir and Au. The silver compound is at least one selected from the group consisting of silver oxide, silver halide, silver sulfate, silver phosphate, and the like, and is preferably one or more of silver oxide, silver chloride, and silver sulfate, More preferred are silver oxide and / or silver chloride. As the porous inorganic oxide, porous alumina, silica, titania, zirconia and composite oxides thereof and the like can be used, preferably γ-alumina alone, or a group consisting of silica, titania and zirconia An alumina-based composite oxide containing at least one selected from the following is used. When an alumina-based composite oxide is used as the porous inorganic oxide, the content of alumina is preferably 50% by weight or more. If the alumina content is less than 50% by weight, the initial removal characteristics of the purifying material are significantly reduced. By using γ-alumina or an alumina-based composite oxide, the reaction between the added oxygen-containing organic compound or the fuel containing the same and the nitrogen oxide in the exhaust gas occurs efficiently. In particular, by using an alumina-based composite oxide, the durability and heat resistance of the purifying material can be improved and the oxidation of SO ₂ can be suppressed even in the presence of SO ₂ gas.

The specific surface area of the porous inorganic oxide such as alumina used for the first catalyst is preferably 10 m ² / g or more. If the specific surface area is less than 10 m ² / g, the contact area between the exhaust gas and the inorganic oxide (and the silver component carried thereon) becomes small, and good nitrogen oxides cannot be removed. More preferably, the specific surface area of the porous inorganic oxide is 30 m.
² / g or more.

The amount of the silver component (a) supported as an active species on the above-mentioned inorganic oxide such as γ-alumina varies somewhat depending on the type of the organic compound and the fuel added to the exhaust gas, the contact time with the exhaust gas, and the like. However, the content is set to 0.2 to 15% by weight (in terms of silver element) based on 100% by weight of the inorganic oxide. If the amount is less than 0.2% by weight, the removal rate of nitrogen oxides decreases. In addition, when the silver content exceeds 15% by weight, the oxygen-containing organic compound itself tends to burn, and the nitrogen oxide removal rate is rather lowered. The preferred amount of the silver component is 0.1.
5 to 12% by weight.

Of Pt, Pd, Ru, Rh, Ir and Au, Pt, P
It is preferable to use at least one of d, Ru, Rh and Au, and particularly preferable to use at least one of Pt, Pd and Au. P
The loading amount (b) of at least one of t, Pd, Ru, Rh, Ir, and Au is set to 1% by weight or less (element conversion value) based on 100% by weight of the inorganic oxide. If the supported amount exceeds 1% by weight of the inorganic oxide, the removal effect of the silver component is greatly reduced.
It is preferable that the lower limit of the supported amount is 0.001% by weight. The preferred loading is 0.001 to 5% by weight, more preferably 0.001 to 0.1% by weight.

Silver and Pt, P are added to inorganic oxides such as γ-alumina.
As a method for supporting one or more of d, Ru, Rh, Ir, and Au, a known impregnation method, precipitation method, or the like can be used. At that time, the porous inorganic oxide is immersed in a mixed aqueous solution of sulfate, carbonate, nitrate or hydrochloride of each element, or the porous inorganic oxide is immersed in an aqueous solution of each element compound in order. After drying at 50-150 ° C, especially about 70 ° C, 1
It is preferable to raise the temperature in a stepwise manner at 00 to 600 ° C. for firing. The firing is preferably performed in an oxygen atmosphere, a nitrogen atmosphere, or a hydrogen gas flow. In the case of performing in a nitrogen atmosphere or a flow of hydrogen gas, it is preferable to perform the oxidation treatment at 300 to 650 ° C. at last.

In the first preferred form of the purifying material, the thickness of the first catalyst provided on the purifying material base is generally limited by a difference in thermal expansion characteristics between the base material and the catalyst. Often. The thickness of the catalyst provided on the purifying material base is preferably 300 μm or less. With such a thickness, it is possible to prevent the purifying material from being damaged by thermal shock or the like during use. A method for forming a catalyst on the surface of the purifying material base is performed by a known wash coat method, a powder method, or the like.

Further, the amount of the first catalyst provided on the surface of the purifying material base is preferably 20 to 300 g / liter of the purifying material base. If the amount of the catalyst is less than 20 g / liter, good NOx removal cannot be performed. On the other hand, when the amount of the catalyst is 300
When the amount exceeds g / liter, the removal characteristics do not increase so much.
Pressure loss increases. More preferably, the first catalyst provided on the surface of the purifying material base is 50 to 250
g / liter.

(2) Second Catalyst The second catalyst is at least one selected from the group consisting of (c) W, V, Mn, Mo, Nb and Ta which are catalytically active species of the porous inorganic oxide. Oxides of the elements of
It carries at least one metal element selected from the group consisting of t, Pd, Ru, Rh, Ir and Au. Examples of the porous inorganic oxide include heat-resistant ceramics having a large surface area such as titania, alumina, zirconia, and silica or a composite oxide thereof.
Preferably, titania or a composite oxide containing titania is used.

Of W, V, Mo, Mn, Nb and Ta, it is preferable to use W, V, Mo and / or Mn, and it is more preferable to use Mo, W and / or V.
The amount of the W-based oxide (c) supported on the inorganic oxide by the second catalyst is 10% by weight or less (in terms of a metal element) based on the above-mentioned porous inorganic oxide (100% by weight), Preferably 0.01 to 10% by weight, more preferably 0.2
To 8% by weight, more preferably 0.5 to 5% by weight (in terms of metal element). The effect does not change even if the loading amount of the W-based oxide exceeds 10% by weight based on the inorganic oxide. The use of a W-based oxide makes it possible to remove nitrogen oxides using a nitrogen-containing compound such as ammonia as a reducing agent. In the present invention, any catalyst that promotes the reduction reaction of nitrogen oxides by a nitrogen-containing compound such as ammonia can be used without being limited to W-based oxides.

Further, among Pt, Pd, Ru, Rh, Ir and Au,
It is preferable to use at least one of Pt, Pd, Ru, Rh and Au, and particularly preferable to use at least one of Pt, Pd, Rh and Au. The loading amount of at least one of Pt, Pd, Ru, Rh, Ir, and Au is 5% by weight or less (element conversion value) with respect to 100% by weight of the inorganic oxide. Loading amount is 5% by weight of inorganic oxide
If it exceeds 300, the removal effect of the silver component is greatly reduced. In addition, it is preferable to set the lower limit of the supported amount to 0.01% by weight. A more preferred loading is from 0.01 to 4% by weight.

The W-based oxide and Pt, Pd,
As a method of supporting one or more of Ru, Rh, Ir, and Au,
Known impregnation methods, precipitation methods, and the like can be used. At this time, the porous inorganic oxide is immersed in a mixed aqueous solution of ammonium salt, oxalate, sulfate, carbonate, nitrate or hydrochloride of each element, or the porous inorganic oxide is immersed in the aqueous solution of each element compound. Are sequentially immersed, dried at 50 to 150 ° C., particularly 70 ° C., and then gradually heated at 100 to 600 ° C. for firing. This firing is performed in air, under an oxygen atmosphere, under a nitrogen atmosphere, or under a hydrogen gas flow. When firing is performed under a nitrogen atmosphere or a hydrogen gas flow, it is effective to perform an oxidation treatment at 300 to 650 ° C. at last. .

In the first preferred embodiment of the purifying material, the thickness of the second catalyst provided on the purifying material base is 300 μm.
m or less. The amount of the second catalyst provided on the surface of the purifying material base is 20 to 300 g / p of the purifying material base.
It is preferably liter. Further, when the purifying material base is made of a porous inorganic oxide such as titania, a predetermined amount of W and / or V oxides can be carried thereon and used as a purifying agent. In addition, a porous inorganic oxide such as titania carrying a predetermined amount of an oxide of W and / or V can be formed into a formed body such as a honeycomb and used.

In the present invention, the weight ratio of the first catalyst to the second catalyst (the ratio of the total weight of the porous inorganic oxide to the catalytically active species) is from 10: 1 to 1: 2. Is preferred. The ratio is less than 1: 2 (first catalyst is less)
In a wide temperature range of 150 to 650 ° C., the purification rate of nitrogen oxides as a whole decreases. On the other hand, if the ratio exceeds 10: 1 and the amount of the second catalyst is small, the nitrogen-containing compound such as ammonia formed on the first catalyst does not react and is discharged as it is, and the concentration of ammonia and the like in the discharged gas is discharged. Increase. More preferred weight ratio of the first catalyst and the second catalyst is 9: 1 to 1:
It is one.

If the purifying material having the above structure is used, 150
In a wide temperature range of up to 650 ° C., good removal of nitrogen oxides can be performed even with an exhaust gas containing about 10% of water.

Next, the method of the present invention will be described. First, an exhaust gas purifying material having a first catalyst and a second catalyst is provided in the middle of an exhaust gas conduit. Preferably, the first catalyst is arranged to face the exhaust gas inlet and the second catalyst is arranged to face the exhaust gas outlet.

The exhaust gas contains ethylene, propylene and the like to some extent as residual hydrocarbons. However, in general, the amount is not sufficient to reduce NOx in the exhaust gas. The above oxygen-containing organic compound or a reducing agent comprising a mixed fuel containing them is introduced into exhaust gas. The position where the reducing agent is introduced is upstream of the position where the purifying material is installed.

As the hydrocarbons introduced from the outside, gaseous or liquid alkanes, alkenes and / or alkynes can be used under standard conditions. As the gaseous hydrocarbon in the standard state, an alkane, alkene or alkyne having 2 or more carbon atoms is preferable. Specific examples of the hydrocarbon in a liquid state in a standard state include hydrocarbons such as heptane, cetane, kerosene, light oil, gasoline, and heavy oil. Among them, hydrocarbons having a boiling point of 50 to 350 ° C are particularly preferable.

As the oxygen-containing organic compound introduced from the outside, alcohols such as ethanol and isopropyl alcohol having 2 or more carbon atoms, or a fuel containing them can be used. The amount of the reducing agent introduced from the outside is determined by the weight ratio (weight of the reducing agent to be added / nitrogen oxide (NO
(Calculated as) is preferably 0.1 to 5. If the weight ratio is less than 0.1, the removal rate of nitrogen oxides does not increase. On the other hand, when the weight ratio exceeds 5, fuel efficiency is deteriorated.

When a fuel containing a hydrocarbon or an oxygen-containing organic compound is added, it is preferable to use gasoline, light oil, kerosene or the like as the fuel. In this case, the amount of the reducing agent is set such that the weight ratio (the weight of the reducing agent to be added / the weight of the nitrogen oxide in the exhaust gas) is 0.1 to 5 in the same manner as described above.

In the present invention, the overall apparent space velocity of the purifying material is 5 in order to efficiently reduce and remove nitrogen oxides with an oxygen-containing organic compound, hydrocarbon or ammonia.
00,000h ^-1 or less. When the space velocity exceeds 500,000 h ^-1 , the reduction reaction of nitrogen oxides does not sufficiently occur, and the nitrogen oxide removal rate decreases. Preferred space velocity is 450,000
h ^-1 or less, more preferably space velocity and 300,000H ^-1 or less. Among them, the space velocity of the first catalyst (silver, platinum-based catalyst) is 200,000h ^-1 or less, preferably 150,000h
^-1 or less. When the space velocity of the first catalyst exceeds 200,000 h ^-1 , the reduction reaction of nitrogen oxides does not sufficiently occur, and the nitrogen oxide removal rate decreases. The space velocity of the second catalyst (platinum, V-based catalyst) is 250,000h ^-1 or less,
Preferably, it is 200,000 h ^-1 or less. When the space velocity of the second catalyst exceeds 250,000 h ^-1 , the oxidizing and removing properties of hydrocarbons, carbon monoxide, etc., deteriorate. Note that SO in the exhaust gas
_{If 2} is present, the space velocity in the second catalyst (platinum, V-based catalyst) should be between 10,000 and 250,000 h ^-1 . When the space velocity of the second catalyst is less than 10,000 h ⁻¹ , SO ₂ is easily oxidized, which is not preferable.

In the present invention, the temperature of the exhaust gas is maintained at 150 to 650 ° C. at the purifying material installation site where the oxygen-containing organic compound reacts with the nitrogen oxide. If the temperature of the exhaust gas is lower than 150 ° C., the reaction between the reducing agent and the nitrogen oxide does not proceed, and it is not possible to remove the nitrogen oxide satisfactorily. On the other hand, when the temperature exceeds 650 ° C., the combustion of the oxygen-containing organic compound itself takes precedence, and the reduction and removal rate of nitrogen oxides decreases. The preferred exhaust gas temperature is between 250 and 600C.

[0038]

The present invention will be described in more detail with reference to the following specific examples. Example 1 Commercially available pelletized γ-alumina (1.5 mm in diameter, about 2 in length)
To 3 g of 10 g of a specific surface area of 260 m ² / g), using silver nitrate aqueous solution and palladium chloride aqueous solution, silver was 4% by weight of alumina (element conversion value), and palladium was 0.1% of alumina.
01% by weight (in terms of element), dried, and dried in air.
It was calcined stepwise to 0 ° C. to prepare a silver-based catalyst (first catalyst).

Next, 2 g of the same pellet-like γ-alumina
The aqueous solution of chloroplatinic acid was used to convert platinum to γ-alumina.
After loading 2% by weight, 6.2 g of water was added to 1.8 g of ammonium tungstate parapentapentahydrate and 1.0 g of oxalic acid, and the mixture was poured into an aqueous solution dissolved by heating on a water bath.
Soak for minutes. Thereafter, alumina pellets were separated from the solution and dried in air at 80 ° C, 100 ° C, and 120 ° C for 2 hours each. Subsequently, under a nitrogen stream containing 20% oxygen, 1
The temperature is raised from 20 ° C to 500 ° C in 5 hours, and 500 ° C
For 4 hours to prepare a Pt, W-based catalyst (second catalyst) supporting 1% by weight (converted to a metal element) of tungsten with respect to the alumina pellets.

About 3 g of a silver-based catalyst and about 0.1 g of a Pt and W-based catalyst.
6 g of a purifying material, a silver catalyst on the inflow side of the exhaust gas,
The Pt and W-based catalysts were set in the reaction tube so as to be located on the outflow side. Next, a gas having the composition shown in Table 1 (nitrogen monoxide, carbon dioxide, oxygen, ethanol, nitrogen and moisture) was flowed at a flow rate of 4.4 liters per minute (standard state) (total apparent space velocity of about 30). 000 h ^-1 ), and the temperature of the exhaust gas in the reaction tube is raised from 300 ° C. to 550 ° C.
Each time, ethanol and nitrogen oxide were reacted at each temperature.

Table 1 Component concentration Nitric oxide 1000 ppm (dry basis) Carbon dioxide 10% by volume (dry basis) Oxygen 10% by volume (dry basis) Ethanol 1250 ppm (dry basis) Nitrogen Residual moisture 10% by volume (of the above components) (To the total volume)

The nitrogen oxides (NO +
The concentration of NO ₂ ) was measured with a chemiluminescent nitrogen oxide analyzer to determine the nitrogen oxide removal rate. Table 2 shows the results.

Example 2 In the same manner as in Example 1, 4% by weight of silver and 0.01% of palladium were added to powdery γ-alumina (specific surface area: 200 m ² / g) using an aqueous solution of silver nitrate and an aqueous solution of palladium chloride.
Approximately 1.0 g of a catalyst supported by weight (based on γ-alumina)
To a commercially available cordierite honeycomb formed body (diameter 30
mm, coated on approximately 10 mm, 400 cell / inch ²⁾ length,
After drying, it was baked stepwise to 600 ° C. to prepare a silver-based purifying material (a purifying material coated with a first catalyst).

Next, 0.2 wt% (based on γ-alumina) of platinum was carried on the same γ-alumina powder using an aqueous chloroplatinic acid solution, and ammonium vanadate and oxalic acid were added to 30 ml of water. It was poured into an aqueous solution that was heated and dissolved on a water bath and allowed to cool, and was immersed for 30 minutes to form a slurry. Honeycomb shaped body (diameter 30m) similar to the above silver-based catalyst
m, about 2.5 mm in length) was coated with 0.25 g of slurry (dry basis). The content of vanadium with respect to the alumina powder was 1% by weight (in terms of a metal element). Example 1
Drying and calcination were performed under the same conditions as those for the tungsten-Pt / alumina catalyst described above to prepare a Pt / V-based purification material (a purification material coated with a second catalyst).

A silver-based purifying material is provided on the inflow side of the exhaust gas in the reaction tube.
Pt and V-based purifying materials were set on the outflow side, respectively, and evaluated in the same manner as in Example 1 using gases having the compositions shown in Table 1 (overall apparent space velocity of about 30,000 h ^-1 ). Table 2 shows the experimental results.

Comparative Example 1 Only 3.6 g of a silver-based catalyst prepared in the same manner as in Example 1 was set in a reaction tube, and a gas having a composition shown in Table 1 was added at a rate of 4.0 g / min.
At a flow rate of 4 liters (standard state) (total apparent space velocity of about 30,000 h ^-1 ), the temperature of the exhaust gas in the reaction tube was kept in the range of 300 to 550 ° C., and ethanol and nitrogen oxide were reacted. . Table 2 shows the experimental results.

Table 2 Removal rate of nitrogen oxides (NOx) Reaction temperature Removal rate of nitrogen oxides (%) (° C.) Example 1 Example 2 Comparative Example 1 300 76.8 80.5 50.2 350 90. 2 96.7 65.8 400 90.7 97.0 75.1 450 87.7 94.5 70.5 500 72.3 85.4 60.1 550 60.4 64.0 50.4

As can be seen from the above, in Examples 1 and 2, good removal of nitrogen oxides was observed in a wide exhaust gas temperature range. On the other hand, in Comparative Example 1 using only the silver catalyst, the nitrogen oxide removal rate was lower than in Examples 1 and 2.

EXAMPLE 3 Using the purifying material of Example 1, simulated gases (nitrogen monoxide, carbon monoxide, oxygen, propylene, nitrogen and water) shown in Table 3 were added to propylene in addition to the composition equivalent to exhaust gas. Flow at a flow rate of 4.4 liters (standard state) (the overall apparent space velocity is 30,000 h ^-1 ), and change the exhaust gas temperature in the reaction tube from 300 ° C. to 600 ° C. every 50 ° C. Propylene and nitrogen oxides were reacted at a temperature of.

Table 3 Component concentrations Nitric oxide 800 ppm (dry basis) Carbon monoxide 100 ppm (dry basis) Oxygen 10% by volume (dry basis) Propylene 1714 ppm (dry basis, 3 times the mass of nitric oxide) Nitrogen Residual moisture 10% by volume (based on the total volume of the above components)

The nitrogen oxides (NO +
The concentration of NO ₂ ) was measured with a chemiluminescent nitrogen oxide analyzer to determine the nitrogen oxide removal rate. The concentrations of carbon monoxide and hydrocarbons were measured with a CO meter and a HC meter, respectively, to determine the removal rates of carbon monoxide and hydrocarbons. Table 4 shows the results.

Example 4 Using the purifying material of Example 2, a simulated gas (nitrogen monoxide, carbon monoxide, oxygen, propylene, nitrogen and moisture) shown in Table 3 in which propylene was added to the composition equivalent to exhaust gas, was used every minute. At a flow rate of 4.4 liters (standard state) (the total apparent space velocity was 30,000 h ^-1 ), evaluation was performed under the same conditions as in Example 3. Table 4 shows the experimental results.

Comparative Example 2 Only 3.6 g of a silver-based catalyst prepared in the same manner as in Example 1 was set in a reaction tube, and a gas having a composition shown in Table 3 was added at a rate of 4.0 g / min.
At a flow rate of 4 liters (standard state) (overall apparent space velocity of about 30,000 h ^-1 ), evaluation was performed under the same conditions as in Example 3. Table 4 shows the experimental results.

Table 4 Removal rate of nitrogen oxides (NOx), carbon monoxide (CO) and hydrocarbons (HC) Reaction temperature Removal component Removal rate (%) (° C.) Example 3 Example 4 Comparative Example 2 300 NOx 30 330 CO 52 52.3 40 HC 35 35 30 350 NOx 40 4500 CO 80 82 60 HC 71 76 35 400 NOx 60 65 20 CO 100 100 70 HC 96 95 95 450 450 NOx 80 88 60 60 CO 100 100 70 70 98 65 500 NOx 80 90 55 CO 100 100 80 HC 100 100 70 70 550 NOx 55 60 25 CO 100 100 90 HC 100 100 85 600 NOx 20 25 10 CO 100 100 98 HC 100 100 90

As can be seen from the above, in Examples 3 and 4, good removal of nitrogen oxides and hydrocarbons was observed in a wide exhaust gas temperature range. Further, the removal rate of carbon monoxide is as excellent as 90% or more. On the other hand, in Comparative Example 2 using only the silver catalyst, the temperature range for removing nitrogen oxides was narrow, and the removal rates of carbon monoxide and hydrocarbons were low.

Example 5 To 10 g of commercially available powdered silica-alumina (SiO ₂ content: 5% by weight, specific surface area: 350 m ² / g), 4% by weight of silver was added using an aqueous solution of silver nitrate and an aqueous solution of chloroplatinic acid. After drying, and after drying, calcined stepwise in the air to 600 ° C.
Pellets having a length of 2 to 3 mm were prepared to prepare a silver-based catalyst (first catalyst).

Next, pelletized titania (1.5 m in diameter)
m, length 2 to 3 mm, specific surface area 35 m ² / g) 2 g of platinum aqueous solution using 1% by weight of chloroplatinic acid aqueous solution (element conversion value)
After being supported, ammonium vanadate and oxalic acid were added to water, and the mixture was poured into an aqueous solution that was heated and dissolved in a water bath and allowed to cool, and was immersed for 30 minutes. Value) supported, dried and calcined in the same manner as above, dried at 80 ° C., 100 ° C., and 120 ° C. for 2 hours each, and then from 120 ° C. to 500 ° C. for 5 hours under a nitrogen stream containing 20% oxygen. To raise the temperature
A Pt, V-based purifying material (second catalyst) was prepared.

A purifying material consisting of about 3.6 g of the first catalyst (silver-based catalyst) and about 1.2 g of the second catalyst (Pt, V-based catalyst) was supplied to the exhaust gas inflow side, and the silver-based catalyst was discharged. Pt on the side,
The V-type catalysts were set in the reaction tubes so as to be respectively located. Next, a gas (nitrogen monoxide, carbon monoxide, oxygen, ethanol, propylene, sulfur dioxide, nitrogen and water) having a composition shown in Table 5 was flowed at a flow rate of 4.4 liters per minute (standard state) (No. The apparent space velocity of one catalyst is about 30,00.
0h ^-1 , the apparent space velocity of the second catalyst is about 100,00
0h ^-1 . ), The temperature of the exhaust gas in the reaction tube was changed from 250 ° C. to 600 ° C. every 50 ° C., and ethanol and nitrogen oxide were reacted at each temperature.

Table 5 Component Concentration Nitric Oxide 800 ppm (dry basis) Oxygen 10% by volume (dry basis) Carbon Monoxide 100 ppm (dry basis) Ethanol 3 times the mass of nitric oxide (dry basis) Propylene 100 ppm (dry basis) (Dry basis) Sulfur dioxide 80 ppm (dry basis) Nitrogen Residual moisture 10% by volume (based on the total volume of the above components)

The nitrogen oxide (NO +
The concentration of NO ₂ ) was measured with a chemiluminescent nitrogen oxide analyzer to determine the nitrogen oxide removal rate. The concentrations of carbon monoxide, sulfur dioxide and hydrocarbons (propylene) were measured with a CO meter, SOx meter and HC meter, respectively, and the removal rates of carbon monoxide and hydrocarbons and the oxidation rates of sulfur dioxide were determined. However, the removal rates of carbon monoxide and hydrocarbons were determined under the condition that ethanol was not added. Table 6 shows the results.

Example 6 In the same manner as in Example 5, a catalyst containing 4% by weight of silver and 0.01% by weight of platinum was supported on an aqueous solution of silver nitrate and an aqueous solution of chloroplatinic acid on powdered silica / alumina. 1.0g
Is a commercially available cordierite honeycomb-shaped molded product (diameter 3
0 mm, length of about 12.5 mm, 400 cells / inch ²⁾
And dried and fired stepwise to 600 ° C. to prepare a silver-based purifying material (a purifying material coated with a first catalyst).

Next, titania powder (specific surface area 50 m ² /
g) was loaded with 1% by weight (based on titania) of platinum using an aqueous solution of chloroplatinic acid, and then water was added to ammonium tungstate parapentahydrate and oxalic acid and dissolved by heating on a water bath. And immersed for 30 minutes, 3% by weight of tungsten with respect to titania (converted value of metal element)
Loaded and slurried. 0.4 g (dry base) of a slurry was coated on a honeycomb-shaped formed body (diameter 30 mm, length about 4.2 mm) similar to the silver-based purifying material. Drying and firing were performed under the same conditions as in Example 5 to prepare a Pt, W-based purifying material (a purifying material coated with a second catalyst).

A silver-based purifying material is provided on the exhaust gas inflow side in the reaction tube.
Pt and W-based purifying materials were set on the outflow side, respectively, and evaluated in the same manner as in Example 5 using gases having the compositions shown in Table 5 (the apparent space velocity of the silver-based purifying material was about 30,000 h ^-1 , Pt, W The apparent space velocity of the system purifying material is about 90,000 h ^-1 .) Table 6 shows the experimental results.

Example 7 A silver-based purifying material was prepared in the same manner as in Example 6. In the same manner, 1% by weight of platinum is added to powdered titania,
After supporting 2% by weight of tungsten and 3% by weight of vanadium (each in terms of a metal element), a honeycomb shaped body was coated to prepare a Pt, W, V-based purification material.

A silver-based purifying material is provided on the exhaust gas inflow side in the reaction tube.
Pt, W, and V-based purification materials were set on the outflow side, respectively, and evaluated in the same manner as in Example 5 using gases having the compositions shown in Table 5 (the apparent space velocity of the silver-based purification material was about 30,000 h ^-1 , Pt ,
The apparent space velocity of W and V cleaning materials is about 90,000h ^-1
It is. ). Table 6 shows the experimental results.

Comparative Example 3 Only 3.6 g of a silver-based catalyst prepared in the same manner as in Example 5 was set in a reaction tube, and a gas having a composition shown in Table 5 was added at a rate of 4.0 g / min.
It was flowed at a flow rate of 4 liters (standard state) (overall apparent space velocity of about 30,000 h ^-1 ), and evaluated under the same conditions as in Example 5. Table 6 shows the experimental results.

Table 6 Removal rates of nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC) and oxidation rates of sulfur dioxide (SO ₂ ) Reaction temperature Removal components Removal rates (NOx, CO, HC) And oxidation rate (SO ₂ ) (%) (° C.) Example 5 Example 6 Example 7 Comparative Example 3 250 NOx 20 18 24 12 CO 40 38 40 15 HC 30 28 31 10 SO ₂ ----300 NOx 55 50 58 30 CO 50 48 46 40 HC 40 38 40 32 SO 2 - - - - 350 NOx 75 70 78 50 CO 70 68 68 60 HC 45 45 42 32 SO 2 - - - - 400 NOx 84 85 80 60 CO 100 100 100 70 HC 95 96 95 40 SO ₂ 55 5-450 NOx 75 78 72 70 CO 100 100 100 70 HC 98 98 98 65 SO ₂ 777-500 NOx 70 72 71 60.2 CO 100 100 100 80 HC 100 100 100 70 70 SO ₂ 12 12 12-550 NOx 50 52 50 52 CO 100 100 100 90 90 HC 100 100 100 100 85 SO ₂ 15 15 15-600 NOx 10 20 15 20 CO 100 100 100 98 98 HC 100 100 100 90 SO ₂ 20 20 20-

As shown in Table 6, Examples 5 to 7 show more effective removal of nitrogen oxides in a wider temperature range than Comparative Example 3, and high removal of carbon monoxide and hydrocarbons even in a low temperature range. was gotten. Further, by using an alumina composite oxide as the porous inorganic oxide, the oxidation characteristics of sulfur dioxide were also low.

Example 8 To 10 g of commercially available pelletized γ-alumina (1.5 mm in diameter, about 2 to 3 mm in length, specific surface area: 260 m ² / g), silver was converted to alumina using an aqueous silver nitrate solution and an aqueous palladium chloride solution. 4% by weight (in terms of element), palladium carrying 0.01% by weight of alumina (in terms of element), and after drying, firing stepwise in air to 600 ° C. to form a silver-based catalyst (first catalyst) Prepared.

Next, a similar pelletized γ-alumina (diameter 1.5 mm, length 2-3 mm, specific surface area 260 m ² /
g) 1% by weight of platinum in 2 g of an aqueous solution of chloroplatinic acid
(Equivalent to element) After loading, ammonium vanadate and oxalic acid were added to water, the solution was heated and dissolved in a water bath, poured into a cooled aqueous solution, immersed for 30 minutes, and 3 wt. % (Converted value of metal element)
After drying, calcination was carried out in the same manner as described above.
At 120 ° C for 2 hours, then 20% oxygen
Was heated from 120 ° C. to 500 ° C. over 5 hours under a nitrogen stream containing Pt to prepare a Pt, V-based purifying material (second catalyst).

A purifying material composed of about 3.6 g of the first catalyst (silver-based catalyst) and about 1.2 g of the second catalyst (Pt, V-based catalyst) was supplied to the exhaust gas inflow side, and the silver-based catalyst was discharged. Pt on the side,
The V-type catalysts were set in the reaction tubes so as to be respectively located. Next, gases having the composition shown in Table 7 (nitrogen monoxide, carbon monoxide, oxygen, ethanol, propylene, nitrogen and moisture)
At a flow rate of 4.4 liters per minute (standard condition) (the apparent space velocity of the first catalyst is about 30,000 h ^-1 and the apparent space velocity of the second catalyst is about 100,000 h ^-1 ). ), The temperature of the exhaust gas in the reaction tube is increased from 250 ° C. to 550 ° C.
The temperature was changed every 50 ° C., and ethanol and nitrogen oxide were reacted at each temperature.

Table 7 Component Concentrations Nitric Oxide 800 ppm (dry basis) Oxygen 10% by volume (dry basis) Carbon Monoxide 100 ppm (dry basis) Ethanol 3 times the mass of nitric oxide (dry basis) Propylene 100 ppm (dry basis) Dry basis) Nitrogen Residual moisture 10% by volume (based on the total volume of the above components)

The nitrogen oxides (NO +
The concentration of NO ₂ ) was measured with a chemiluminescent nitrogen oxide analyzer to determine the nitrogen oxide removal rate. The concentrations of carbon monoxide and hydrocarbons (propylene) were measured using a CO meter,
The removal rate of carbon monoxide and hydrocarbon was determined by measuring with an HC meter. However, the removal rates of carbon monoxide and hydrocarbons were determined under the condition that ethanol was not added. Table 8 shows the results.

Example 9 In the same manner as in Example 8, powdered alumina (specific surface area 2
Using a silver nitrate aqueous solution and a chloroplatinic acid aqueous solution, about 1.0 g of a catalyst supporting 4% by weight of silver and 0.01% by weight of platinum was prepared using a commercially available cordierite honeycomb-shaped molded article (00 m ² / g). A coating was applied to a diameter of 30 mm, a length of about 12.5 mm, and 400 cells / inch ² ), dried and baked stepwise to 600 ° C. to prepare a silver-based purifying material (a purifying material coated with a first catalyst).

Next, titania powder (specific surface area 50 m ² /
g) was loaded with 1% by weight (based on titania) of platinum using an aqueous solution of chloroplatinic acid, and then water was added to ammonium tungstate parapentahydrate and oxalic acid and dissolved by heating on a water bath. And immersed for 30 minutes, 3% by weight of tungsten with respect to titania (converted value of metal element)
Loaded and slurried. 0.4 g (dry base) of a slurry was coated on a honeycomb-shaped formed body (diameter 30 mm, length about 4.2 mm) similar to the silver-based purifying material. Drying and firing were performed under the same conditions as in Example 8 to prepare a Pt, W-based purifying material (a purifying material coated with a second catalyst).

A silver-based purifying material is provided on the exhaust gas inflow side in the reaction tube.
Pt and W-based purifying materials were set on the outflow side, respectively, and were evaluated in the same manner as in Example 8 using gases having the compositions shown in Table 7 (the apparent space velocity of the silver-based purifying material was about 30,000 h ^-1 , Pt, W The apparent space velocity of the system purifying material is about 90,000 h ^-1 .) Table 8 shows the experimental results.

Example 10 In the same manner as in Example 9, a silver-based purifying material was prepared. In the same manner, 1% by weight of platinum is added to powdered titania,
After loading 1% by weight of tungsten and 2% by weight of vanadium (each in terms of a metal element), a honeycomb shaped body was coated to prepare a Pt, W, V-based purification material.

A silver-based purifying material is provided on the exhaust gas inflow side in the reaction tube.
Pt, W, and V-based purification materials were set on the outflow side, respectively, and evaluated in the same manner as in Example 8 using gases having the compositions shown in Table 7 (the apparent space velocity of the silver-based purification material was about 30,000 h ^-1 , Pt ,
The apparent space velocity of W and V cleaning materials is about 90,000h ^-1
It is. ). Table 8 shows the experimental results.

Comparative Example 4 In the same manner as in Example 8, only silver was added to alumina pellets.
2. a silver-based catalyst prepared by supporting by weight% (converted to silver element);
6 g was set in a reaction tube, and a gas having a composition shown in Table 7 was flowed at a flow rate of 4.4 liters per minute (standard state) (total apparent space velocity of about 30,000 h ^-1 ). The condition was evaluated. Table 8 shows the experimental results.

Table 8 Removal rates of nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC) Reaction temperature Removal components Removal rates (NOx, CO, HC) (%) (° C) Example 8 Example 9 Example 10 Comparative Example 4 250 NOx 50 55 58 30 CO 50 45 40 20 HC 40 36 32 15 300 NOx 77 80 82 50.2 CO 70 72 70 45 HC 60 60 58 37 350 NOx 82 96 98 65.8 CO 90 90 88 65 HC 80 80 75 38 400 NOx 90 98 95 75.2 CO 100 100 100 75 HC 100 100 100 46 46 450 NOx 88 95 93 70.3 CO 100 100 100 100 75 HC 100 100 100 70 70 500 NOx 7387 80 60.5 CO 100 100 100 85 HC 100 100 100 75 550 NOx 60.5 65 60 50.5 CO 100 100 100 95 95 HC 100 100 100 75

As shown in Table 8, in exhaust gas containing no sulfur oxides, Examples 8 to 10 showed higher removal of nitrogen oxides, carbon monoxide and hydrocarbons over a wider temperature range than Comparative Example 4. The characteristics were shown.

Example 11 Commercially available pelletized γ-alumina (1.5 mm in diameter, about 2 in length)
３3 mm, specific surface area 260 m ² / g) 10 g was immersed in an aqueous silver nitrate solution, and dried in air at 80 ° C. for 2 hours and then in a dry nitrogen stream at 180 ° C. for 2 hours. Next, after cooling to room temperature under a stream of dry nitrogen, the γ-alumina was immersed in an aqueous solution of ammonium chloride (a solution of 0.5 g of ammonium chloride in 30 ml of water) for 12 hours to convert silver nitrate on γ-alumina into chloride. Precipitated as silver, 4% by weight
An alumina pellet supporting (element conversion value) silver in the form of silver chloride was obtained. Then, using an aqueous palladium chloride solution for the alumina pellets,
1% by weight (element conversion value), dried, and dried in air
The mixture was calcined stepwise to ℃ to prepare a silver-based catalyst (first catalyst).

Next, 2 g of the same pellet-like γ-alumina
The aqueous solution of chloroplatinic acid was used to convert platinum to γ-alumina.
After loading 2% by weight, 6.2 g of water was added to 1.8 g of ammonium tungstate parapentapentahydrate and 1.0 g of oxalic acid, and the mixture was poured into an aqueous solution dissolved by heating on a water bath.
Soak for minutes. Thereafter, alumina pellets were separated from the solution and dried in air at 80 ° C, 100 ° C, and 120 ° C for 2 hours each. Subsequently, under a nitrogen stream containing 20% oxygen, 1
The temperature is raised from 20 ° C to 500 ° C in 5 hours, and 500 ° C
For 4 hours to prepare a Pt, W-based catalyst (second catalyst) supporting 1% by weight (converted to a metal element) of tungsten with respect to the alumina pellets.

About 3 g of a silver-based catalyst and about 0.1 g of a Pt and W-based catalyst.
6 g of a purifying material, a silver catalyst on the inflow side of the exhaust gas,
The Pt and W-based catalysts were set in the reaction tube so as to be located on the outflow side. Next, a gas having the composition shown in Table 1 (nitrogen monoxide, carbon dioxide, oxygen, ethanol, nitrogen and moisture) was flowed at a flow rate of 4.4 liters per minute (standard state) (total apparent space velocity of about 30). 000 h ^-1 ), and the temperature of the exhaust gas in the reaction tube is raised from 300 ° C. to 550 ° C.
Each time, ethanol and nitrogen oxide were reacted at each temperature.

The gaseous nitrogen oxide (NO +
The concentration of NO ₂ ) was measured with a chemiluminescent nitrogen oxide analyzer to determine the nitrogen oxide removal rate. Table 9 shows the results.

Example 12 In the same manner as in Example 11, powdery γ-alumina (specific surface area: 200 m ² / g) contained 4% by weight of silver chloride (in terms of a metal element) and 0.01% by weight of palladium (in terms of a metal element). About 1.0 g of the supported catalyst (based on γ-alumina) was coated with a commercially available cordierite honeycomb-shaped formed body (diameter 30 mm, length about 10 mm, 400 mm).
Cells / inch ² ), dried and baked stepwise to 600 ° C. to prepare a silver-based purifying material (a purifying material coated with a first catalyst).

Next, 0.2 wt% (based on γ-alumina) of platinum was carried on the same γ-alumina powder using an aqueous chloroplatinic acid solution, and ammonium vanadate and oxalic acid were added to 30 ml of water. It was poured into an aqueous solution that was heated and dissolved on a water bath and allowed to cool, and was immersed for 30 minutes to form a slurry. Honeycomb shaped body (diameter 30m) similar to the above silver-based catalyst
m, about 2.5 mm in length) was coated with 0.25 g of slurry (dry basis). The content of vanadium with respect to the alumina powder was 1% by weight (in terms of a metal element). Example 1
Drying and calcination were performed under the same conditions as those for the tungsten-Pt / alumina catalyst described above to prepare a Pt / V-based purification material (a purification material coated with a second catalyst).

A silver-based purifying material is provided on the exhaust gas inflow side in the reaction tube.
Pt and V-based purifying materials were set on the outflow side, respectively, and evaluated in the same manner as in Example 11 using gases having the compositions shown in Table 1 (overall apparent space velocity of about 30,000 h ^-1 ). Table 9 shows the experimental results.
Shown in

Comparative Example 5 Only 3.6 g of a silver-based catalyst prepared in the same manner as in Example 11 was set in a reaction tube, and a gas having a composition shown in Table 1 was flowed at a rate of 4.4 liters per minute (standard state). (Total apparent space velocity of about 30,000 h ^-1 ), the temperature of the exhaust gas in the reaction tube was kept in the range of 300 to 550 ° C., and ethanol and nitrogen oxides were reacted. Table 9 shows the experimental results.

Table 9 Removal rate of nitrogen oxides (NOx) Reaction temperature Removal rate of nitrogen oxides (%) (° C) Example 11 Example 12 Comparative Example 5 300 75.2 78.8 48.3 350 88. 4 94.8 63.2 400 88.9 96.2 74.8 450 89.3 96.4 75.3 500 75.4 88.4 65.6 550 64.3 68.3 55.7

As can be seen from the above, Examples 11 and 1
In No. 2, good removal of nitrogen oxides was observed in a wide exhaust gas temperature range. On the other hand, in Comparative Example 5 using only the silver-based catalyst, the nitrogen oxide removal rate was lower than Examples 11 and 12.

[0092]

As described above in detail, the use of the exhaust gas purifying material of the present invention makes it possible to efficiently remove nitrogen oxides in exhaust gas containing excess oxygen in a wide temperature range. INDUSTRIAL APPLICABILITY The exhaust gas purifying material and the purification method of the present invention can be widely used for purifying exhaust gas of various types of combustors, automobiles and the like.

Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B01J 23/64 103 A (72) Inventor Mika Saito 4-1-1, Suehiro, Kumagaya-shi, Saitama Riken Co., Ltd. Inside Kumagaya Office (72) Inventor Kiyohide Yoshida 4-1-1, Suehiro, Kumagaya City, Saitama Prefecture Inside Riken Kumagaya Office

Claims (7)

[Claims] 1. A method for reducing and removing nitrogen oxides from a flue gas containing nitrogen oxides and oxygen in excess of a theoretical reaction amount for coexisting unburned components, and also oxidizing residual and unreacted carbon monoxide and hydrocarbons. In the exhaust gas purifying material to be removed, (1) a porous inorganic oxide is mixed with (a) 0.2 to 15% by weight (in terms of element) of silver and / or a silver compound of the inorganic oxide, or a mixture thereof. , (B) Pt, Pd, Ru, Rh, Ir of 1% by weight or less (element conversion value) of the inorganic oxide
And a first catalyst supporting at least one element selected from the group consisting of Au and (2) a porous inorganic oxide, (c) 10% by weight or less of the inorganic oxide (metal An oxide of at least one element selected from the group consisting of W, V, Mn, Mo, Nb, and Ta
(D) 5% by weight or less (element conversion value) of the inorganic oxide
An exhaust gas purifying material comprising: a second catalyst supporting at least one element selected from the group consisting of Pt, Pd, Ru, Rh, Ir, and Au. 2. The exhaust gas purifying material according to claim 1, wherein said silver compound is at least one selected from the group consisting of silver oxide, silver halide, silver sulfate and silver phosphate. Exhaust gas purification material. 3. The exhaust gas purifying material according to claim 1, wherein the purifying material has the first catalyst on an exhaust gas inflow side and the second catalyst on an exhaust gas outflow side. Exhaust gas purifying material. 4. The exhaust gas purifying material according to claim 1, wherein the porous inorganic oxide is selected from alumina alone or a group consisting of silica, titania and zirconia in the first catalyst. An exhaust gas purifying material comprising an alumina-based composite oxide containing at least one kind, wherein the second catalyst is titania, alumina, zirconia, silica, or a composite oxide thereof. 5. The exhaust gas purifying material according to claim 1, wherein the purifying material is obtained by coating the first and second catalysts on the surface of a ceramic or metal substrate. Exhaust gas purifying material. 6. The exhaust gas purifying material according to claim 1, wherein the porous inorganic oxide of the first and second catalysts is in the form of pellets or granules, respectively. Purifying material. 7. A method for reducing and removing nitrogen oxides from a flue gas containing nitrogen oxides and oxygen in excess of the theoretical amount of reaction with unburned components, and also oxidizing residual and unreacted carbon monoxide and hydrocarbons. In the exhaust gas purifying method for removing, using the exhaust gas purifying material according to any one of claims 1 to 5, the exhaust gas purifying material is installed in the middle of an exhaust gas conduit, and hydrocarbons and / or carbon are disposed upstream of the purifying material. Number 2
The exhaust gas to which the oxygen-containing organic compound or the fuel containing the above is added is brought into contact with the purification material at 150 to 650 ° C., thereby removing the nitrogen oxides by reaction with the oxygen-containing organic compound in the exhaust gas. A method for purifying exhaust gas, comprising oxidizing and removing residual and unreacted carbon monoxide and hydrocarbons.