JPH0999241A - Waste gas purification material and method for purifying waste gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a purification material attaining effective reduction and removal of NOx from waste combustion gas contg. NOx and excess oxygen by carrying Co oxide on a porous inorg. oxide, a W compd. on a similar oxide and Pt on a similar oxide and mixing them. SOLUTION: A 1st catalyst is formed by carrying Co oxide on a porous inorg. oxide such as alumina or titania by 1-20wt.% (expressed in terms of Co). A 2nd catalyst is formed by carrying a compd. of W, V, etc., on a similar oxide by 0.2-10wt.% (expressed in terms of metallic element). A 3rd catalyst is formed by carrying an element such as Pt or Pd on a similar oxide by 0.05-5wt.%. These catalysts are mixed to obtain the objective waste gas purification material. When this purification material is used, NOx in waste gas contg. excess oxygen is efficiently removed over a wide temp. region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying material capable of effectively reducing and 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 emitted 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.

Therefore, many methods have been proposed for removing nitrogen oxides by using a catalyst in which a transition metal is supported on zeolite or alumina and adding a reducing agent having a theoretical reaction amount or less with oxygen in exhaust gas. However, these methods do not provide effective removal of nitrogen oxides in a low-temperature region, and contain exhaust gas from vehicles and the like, which contain water and whose exhaust gas temperature greatly changes depending on operating conditions. The removal rate is significantly reduced. On the other hand, although a platinum catalyst has been reported as a catalyst that operates in a low temperature region, the nitrogen oxide removal rate in a temperature range of 200 ° C. or less is not sufficient, and N ₂ O is a by-product of nitrogen oxide removal. There are issues that are generated.

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. An object of the present invention is to provide an exhaust gas purifying material and an exhaust gas purifying method which can efficiently reduce and remove nitrogen oxides from a combustion exhaust gas containing oxygen at a theoretical reaction amount or more with respect to an unburned portion and containing water.

[0008]

Means for Solving the Problems In view of the above problems, as a result of earnest studies, the present inventor has found that an exhaust gas purifying material combining a Co component, a W-based component and a platinum component is used, and that the hydrocarbon and hydrocarbon having 2 carbon atoms are contained in the exhaust gas. By adding any one of the above oxygenated organic compounds or a fuel containing them, and contacting the exhaust gas with the above-mentioned purifying material, it has been found that nitrogen oxides can be effectively removed in a wide temperature range, and the present invention completed.

That is, the first exhaust gas purifying material of the present invention for reducing and removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and oxygen in an amount larger than the theoretical reaction amount for coexisting unburned components is a porous inorganic material. A first catalyst comprising 1 to 20% by weight of a Co oxide (in terms of a metal element) supported on an oxide;
W, V, Mo, Mn, Nb, Ta
A compound of at least one element selected from the group consisting of
Pt, Pd, Ru, Rh, a second catalyst supporting 10 to 10% by weight (in terms of a metal element) and a porous inorganic oxide.
It is characterized by being mixed with a third catalyst supporting at least one element selected from the group consisting of Ir and Au in an amount of 0.05 to 5% by weight (in terms of a metal element).

[0010] The second exhaust gas purifying material of the present invention for reducing and removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and oxygen in an amount larger than the theoretical reaction amount for coexisting unburned components,
A first catalyst in which 1 to 20% by weight of a Co oxide is supported on a porous inorganic oxide (in terms of a metal element), W, V, M
a second catalyst composed of a compound of one or more elements selected from the group consisting of o, Mn, Nb, and Ta; and a porous inorganic oxide selected from the group consisting of Pt, Pd, Ru, Rh, Ir, and Au. 0.05-5% by weight of at least one element
(A metal element conversion value) is mixed with a third catalyst carrying the metal catalyst.

The third exhaust gas purifying material of the present invention for reducing and removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and oxygen in an amount larger than the theoretical reaction amount of coexisting unburned components,
A first catalyst in which a porous inorganic oxide supports 1 to 20% by weight of a Co oxide (in terms of a metal element); and a porous inorganic oxide containing W, V, Mo, Mn, Nb, and Ta. 0.2 to 10% by weight of a compound of one or more elements selected from the group consisting of
(Converted to metal element), Pt, Pd, Ru, Rh, Ir
And at least one element selected from the group consisting of Au and 0.05 to 5% by weight (in terms of metal element) of a second catalyst.

Further, the exhaust gas purifying method of the present invention for reducing and removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and oxygen in excess of the theoretical reaction amount for coexisting unburned components uses the above exhaust gas purifying material. The exhaust gas purifying material is installed in the middle of an exhaust gas conduit, and the exhaust gas to which hydrocarbons and / or oxygen-containing organic compounds are added upstream of the purifying material is
The nitrogen oxides are removed by contacting the purifying material at 50 to 600 ° C. and reacting with the hydrocarbons and / or oxygen-containing organic compounds in the exhaust gas.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. [1] First Exhaust Gas Purifying Material The first exhaust gas purifying material of the present invention comprises: a first catalyst in which a porous inorganic oxide carries a Co oxide; A second catalyst supporting a compound of one or more elements selected from the group consisting of V, Mo, Mn, Nb, and Ta; and Pt, Pd, Ru, R on a porous inorganic oxide.
at least one selected from the group consisting of h, Ir and Au
Mixed with a third catalyst carrying the seed element,
In addition to acting on the removal of nitrogen oxides in a low temperature range, it acts on the oxidative removal of carbon monoxide and hydrocarbons.

(1) First Catalyst The first catalyst comprises a porous inorganic oxide carrying a Co oxide. As the porous inorganic oxide, any of alumina, titania, zeolite, silica, zirconia, ZnO, tin oxide, and MgO, or a composite or mixed oxide containing them can be used. Various zeolites such as ferrierite, mortenite, and ZSM-5 can be used as the zeolite. In addition, the tin oxide referred to here includes tin oxide in various oxidation states, and as main tin oxide,
Stannous oxide, stannic oxide and the like can be mentioned.

The specific surface area of a porous inorganic oxide such as alumina is preferably at least 10 m ² / g. When the specific surface area is less than 10 m ² / g, the dispersion of the catalytically active species is reduced, and good removal of nitrogen oxides cannot be performed. More preferred specific surface area of the porous inorganic oxide is 30 m ² / g or more.

With the porous inorganic oxide as 100% by weight,
The loading amount of the Co component is 1 to 20% by weight (in terms of a metal element).
And preferably 1 to 15% by weight (in terms of metal element)
It is.

The loading of the active species of the first catalyst can be carried out by a known impregnation method, precipitation method or the like using an aqueous solution of Co nitrate, acetate or the like. After supporting Co on the porous inorganic oxide, the porous inorganic oxide is dried at 50 to 150 ° C, particularly 70 ° C,
This is carried out by raising the temperature stepwise at 600 ° C. and firing. This baking is performed in air, under an oxygen atmosphere, under a nitrogen atmosphere, or under a hydrogen stream. In the case of firing in a nitrogen atmosphere or a hydrogen stream, it is preferable to perform an oxidation treatment at a temperature of 300 ° C. or higher. When zeolite is used as the inorganic oxide, it is preferable to support the zeolite by an impregnation method or a known ion exchange method.

(2) Second catalyst The second catalyst comprises W, V, Mo, M
It supports a compound of at least one element selected from the group consisting of n, Nb, and Ta. As the porous inorganic oxide, any of alumina, titania, zeolite, silica, zirconia, ZnO, tin oxide, and MgO, or a composite or mixed oxide containing them can be used. As zeolite, ferrierite, mortenite, ZS
Various zeolites such as M-5 can be used. As in the case of the first catalyst, the specific surface area of the porous inorganic oxide is 1
It is preferably 0 m ² / g or more.

The compound of W, V, Mo, Mn, Nb and Ta is preferably an oxide, particularly preferably an oxide of W and / or V. Assuming that the porous inorganic oxide is 100% by weight, the loading amount of the W component is 0.2 to 10% by weight.
(In terms of metal element), preferably 0.5 to 8% by weight (in terms of metal element).

The loading of the active species on the second catalyst is W,
In the case of V, Mo, Mn, Nb and Ta, it can be carried out by a known impregnation method, precipitation method, or the like using a solution of a salt compound of each element, for example, a solution obtained by adding oxalic acid to an ammonium salt and dissolving it. . After supporting the active species on the porous inorganic oxide, the porous inorganic oxide is dried at 50 to 150 ° C., particularly 70 ° C.
It is carried out by raising the temperature stepwise at 00 ° C. and firing. This firing is performed in air, under an oxygen atmosphere, under a nitrogen atmosphere,
Alternatively, it is performed under a hydrogen stream. In the case of firing in a nitrogen atmosphere or a hydrogen stream, it is preferable to perform an oxidation treatment at a temperature of 300 ° C. or higher. In addition, instead of titania, metatitanic acid (hydrous titanium oxide) is used as a starting material, and V,
Carrying W and Mo is also an effective method. When zeolite is used as the inorganic oxide, it is preferable to support the zeolite by an impregnation method or a known ion exchange method.

(3) Third catalyst The third catalyst is a porous inorganic oxide which contains P as a catalytically active species.
It carries at least one element selected from the group consisting of t, Pd, Ru, Rh, Ir and Au, acts on the removal of nitrogen oxides in a low temperature range, and removes carbon monoxide and hydrocarbons. Acts on oxidation removal. As the porous inorganic oxide, it is preferable to use any one of alumina, titania, zeolite, silica, zirconia, ZnO, tin oxide, MgO, and the like, or a composite or mixed oxide containing them. Similar to the first catalyst, the specific surface area of the porous inorganic oxide is preferably 10 m ² / g or more.

Of Pt, Pd, Ru, Rh and Au,
In particular, it is preferable to use at least one of Pt, Pd, and Au. Assuming that the porous inorganic oxide is 100% by weight, the supported amount of the platinum-based component is 0.05 to 5% by weight (in terms of metal element), preferably 0.05 to 4% by weight (in terms of metal element). is there.

For supporting the active species on the third catalyst, a known impregnation method, precipitation method or the like can be used. When the impregnation method is used, the porous inorganic oxide is immersed in an aqueous solution of a carbonate, nitrate, acetate, sulfate, chloride, hexachlorometal acid, or dinitrodiamine metal compound of a catalytically active species element. After drying at 50 to 150 ° C, especially 70 ° C,
It is carried out by raising the temperature stepwise at 0 to 600 ° C. and firing. This baking is performed in air, under an oxygen atmosphere, under a nitrogen atmosphere, or under a hydrogen stream. In the case of firing in a nitrogen atmosphere or a hydrogen stream, it is preferable to perform an oxidation treatment at a temperature of 300 ° C. or higher. When zeolite is used as the inorganic oxide, it is preferable to support the zeolite by an impregnation method or a known ion exchange method.

In the first exhaust gas purifying material, a mixed catalyst obtained by mixing a first catalyst, a second catalyst and a third catalyst is used.
This mixing allows the actions of the catalysts to proceed simultaneously without affecting each other. 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 preferably 1:10 to 40: 1. A more preferred weight ratio of the first catalyst to the second catalyst is 1: 5 to 30: 1. The weight ratio of the first catalyst to the third catalyst (the ratio of the total weight of the porous inorganic oxide and the catalytically active species) is preferably 1:10 to 40: 1. More preferably, the weight ratio of the first catalyst to the third catalyst is 1: 5 to 3
0: 1. The mixing can be performed by a known method.

[2] Second Exhaust Gas Purifying Material The second exhaust gas purifying material comprises a first catalyst comprising a porous inorganic oxide carrying a Co oxide, W, V, Mo, Mn, N
b, a second catalyst comprising a compound of one or more elements selected from the group consisting of Ta, and Pt, P
d, Ru, Rh, Ir and Au mixed with a third catalyst supporting at least one element selected from the group consisting of Au.

(1) First catalyst As the first catalyst, those described in the section of the first catalyst of the first exhaust gas purifying material are used. For the loading of the active species on the first catalyst, the method described in the section of the first exhaust gas purifying material can be used.

(2) Second catalyst The second catalyst is a compound of at least one element selected from the group consisting of W, V, Mo, Mn, Nb, and Ta. The compound of W, V, Mo, Mn, Nb and Ta is preferably an oxide, particularly preferably an oxide of W and / or V.

(3) Third catalyst As the third catalyst, the one described in the section of the third catalyst of the first exhaust gas purifying material is used. For supporting the active species on the third catalyst, the method described in the section of the first exhaust gas purifying material can be used.

As the second exhaust gas purifying material, a mixed catalyst obtained by mixing the first catalyst, the second catalyst, and the third catalyst is used.
This mixing allows the actions of the catalysts to proceed simultaneously without affecting each other. 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 preferably 1:10 to 40: 1. A more preferred weight ratio of the first catalyst to the second catalyst is 1: 5 to 30: 1. The weight ratio of the first catalyst to the third catalyst (ratio of the total weight of the porous inorganic oxide and the catalytically active species) is preferably 1:10 to 10: 1. A more preferred weight ratio of the first catalyst to the third catalyst is 1: 5
5: 1. The mixing can be performed by a known method.

[3] Third Exhaust Gas Purifying Material The third exhaust gas purifying material comprises a first catalyst comprising a porous inorganic oxide carrying a Co oxide, and a porous inorganic oxide comprising W,
A compound of at least one element selected from the group consisting of V, Mo, Mn, Nb, and Ta, and Pt, Pd, Ru, Rh, I
It is obtained by mixing a second catalyst supporting at least one element selected from the group consisting of r and Au.

(1) First Catalyst As the first catalyst, the one described in the section of the first catalyst of the first exhaust gas purifying material is used. For the loading of the active species on the first catalyst, the method described in the section of the first exhaust gas purifying material can be used.

(2) Second Catalyst The second catalyst is a compound of at least one element selected from the group consisting of W, V, Mo, Mn, Nb and Ta as catalytically active species on a porous inorganic oxide. And Pt, Pd, R
a catalyst supporting at least one element selected from the group consisting of u, Rh, Ir and Au, acting on removal of nitrogen oxides in a low temperature range and oxidizing and removing carbon monoxide and hydrocarbons Act on. As the porous inorganic oxide, it is preferable to use any one of alumina, titania, zeolite, silica, zirconia, ZnO, tin oxide, MgO, and the like, or a composite or mixed oxide containing them. Various zeolites such as ferrierite, mortenite, and ZSM-5 can be used as the zeolite. Like the first catalyst is preferably a specific surface area of the porous inorganic oxide is 10 m ² / g or more, 30 m ²
/ G or more.

The compound of W, V, Mo, Mn, Nb and Ta is preferably an oxide, particularly preferably an oxide of W and / or V. Among Pt, Pd, Ru, Rh and Au, it is particularly preferable to use at least one of Pt, Pd and Au. Assuming that the porous inorganic oxide is 100% by weight, the supported amount of the W-based component is 0.2 to 10% by weight (in terms of the metal element), and the supported amount of the platinum-based component is 0.05.
-5% by weight (in terms of metal element). The preferred loading of the W-based component is 0.5 to 8% by weight (in terms of metal element), and the preferred loading of the platinum-based component is 0.05 to 4% by weight.
(Metal element conversion value). For supporting the active species on the second catalyst, the method described in the column of the second catalyst and the third catalyst of the first purifying material can be used.

In the third exhaust gas purifying material, a mixed catalyst obtained by mixing the first catalyst and the second catalyst is used. This mixing allows the catalysis of the first catalyst and the catalysis of the second catalyst to proceed simultaneously without affecting each other.
The weight ratio of the first catalyst to the second catalyst (ratio of the total weight of the porous inorganic oxide and the catalytically active species) is from 1:10 to 10:
It is preferably set to 1. More preferably, the weight ratio of the first catalyst to the second catalyst is 1: 5 to 5: 1. The mixing of the first catalyst and the second catalyst can be performed by a known method.

[4] Form of Exhaust Gas Purifying Material A first preferred embodiment of the exhaust gas purifying material of the present invention is a purifying material obtained by coating the above-mentioned catalyst on a purifying material base. As the ceramic material forming the base of the purifying material, cordierite, mullite, alumina and a composite thereof are preferably used. 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. Also, as its structure,
Examples include a honeycomb structure type, a foam type, a three-dimensional network structure type made of a fibrous refractory, a granular form, a pellet form, and the like. The catalyst may be coated on the substrate using a wash coat method, a powder method, or the like, or a wash coat method, a sol
After the porous inorganic oxide is coated on the substrate using a gel method or the like, the catalytically active species can be supported using a known impregnation method, an ion exchange method, or the like.

A second preferred embodiment of the exhaust gas purifying material of the present invention is a catalyst comprising a porous inorganic oxide in the form of pellets, granules, powders, honeycombs, foams or plates carrying a catalytically active species. Or a catalyst obtained by molding a catalyst into a honeycomb, foam, plate, pellet, or granule.

In the case where the form of the purifying material is the first preferred embodiment described above, the thickness of the catalyst provided on the purifying material base is generally limited due to the difference in thermal expansion characteristics between the base material and the catalyst. In many cases. 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 or the like.

The amount of the 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 g /
If it exceeds 1 liter, the removal characteristics are not so improved, and the pressure loss increases. More preferably, the amount of the catalyst provided on the surface of the purifying material base is 50 to 200 g / liter of the purifying material base.

If the purifying material having the above-described structure is used, 150
In a wide temperature range of up to 600 ° C., good removal of nitrogen oxides can be performed even with an exhaust gas containing about 10% of moisture and sulfur oxides.

[5] Exhaust Gas Purification Method Next, the method of the present invention will be described. First, the exhaust gas purifying material of the present invention is installed in the middle of an exhaust gas conduit.

Although the exhaust gas contains ethylene, propylene, etc. to a certain extent as residual hydrocarbons, the amount is generally not sufficient to reduce NOx in the exhaust gas. Preferably, an oxygen-containing organic compound or a reducing agent obtained by mixing the compound with a hydrocarbon fuel is introduced into the 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. In particular, alkanes preferably have 2 or more carbon atoms. Specific examples of the hydrocarbon in a liquid state in a standard state include hydrocarbons such as light oil, cetane, heptane, kerosene, and gasoline. Among them, boiling point 5
Hydrocarbons at 0-350 ° C are particularly preferred. 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 hydrocarbon and / or oxygen-containing organic compound introduced from the outside is determined by the weight ratio (weight of the reducing agent to be added / weight of the reducing agent).
(Weight of nitrogen oxides in the exhaust gas) 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, if it exceeds 5, fuel efficiency will be degraded.

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 space velocity is 200,000 h ^-1 or less, preferably 150,0 h or less, in order to efficiently promote the reduction and removal of nitrogen oxides by oxygen-containing organic compounds and hydrocarbons.
00h ^-1 or less.

Further, in the present invention, the temperature of the exhaust gas at the purification material installation site where the hydrocarbon and / or the oxygen-containing organic compound reacts with the nitrogen oxide is set to 150 to 600 ° C.
To keep. 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, if the temperature exceeds 600 ° C., the combustion of the hydrocarbon and / or the oxygen-containing organic compound itself starts, and the reduction and removal of nitrogen oxides cannot be performed. The preferred exhaust gas temperature is from 200 to 550C, more preferably from 250 to 500C.

[0048]

The present invention will be described in more detail with reference to the following specific examples. Example 1 A commercially available powdery γ-alumina (particle diameter: 0.1 mm or less, specific surface area: 245 m ² / g) was immersed in an aqueous solution of Co acetate, dried, and gradually heated to 100 ° C. to 600 ° C. in air. To 5% by weight of Co with respect to γ-alumina
A (supported by metal element) Co catalyst (first catalyst) was prepared.

Commercially available powdery γ-alumina (particle size: 0.1 m
m, a specific surface area of 245 m ² / g) is immersed in a chloroplatinic acid aqueous solution for 20 minutes, then dried in air at 80 ° C. for 2 hours, and at a temperature of 120 ° C. for 2 hours under a nitrogen stream at 200 to 400 ° C.
Each step was baked for 1 hour. And 4% hydrogen gas
The temperature was raised from 50 ° C. to 400 ° C. over 5 hours under a nitrogen stream containing, and calcined at 400 ° C. for 4 hours.
The temperature was raised from 50 ° C. to 500 ° C. over 5 hours in a nitrogen gas stream containing 5% by weight, and calcined at 500 ° C. for 5 hours to carry 1% by weight of platinum with respect to γ-alumina (in terms of a metal element). Ammonium acid was added to water, and γ-alumina supporting platinum was added to and impregnated with a solution obtained by adding and dissolving oxalic acid by heating, separated from the solution, and gradually heated to 600 ° C. in the air. Baking, molybdenum 5% by weight
(Converted to metal element) A supported platinum-Mo catalyst (second catalyst) was produced.

10 g of the first catalyst and 10 g of the second catalyst are mixed, a binder is added and kneaded, and after drying, the temperature is raised stepwise to 600 ° C. in air and calcined to prepare a mixed catalyst. And a granule having a diameter of 2 to 3 mm to prepare an exhaust gas purifying material.

About 1.5 g of the exhaust gas purifying material was set in the reaction tube. Next, a gas (nitrogen monoxide, oxygen, propylene, nitrogen and water) having a composition shown in Table 1 was flowed at a flow rate of 1.8 liters per minute (standard state) (the apparent space velocity of the purification material was about 30, 000 h ⁻¹ ), and the temperature of the exhaust gas in the reaction tube was kept in the range of 150 to 450 ° C. to react propylene with nitrogen oxides.

The concentration of nitrogen oxides in the gas after passing through the reaction tube was measured with a chemiluminescent nitrogen oxide analyzer to determine the nitrogen oxide removal rate. Table 2 shows the results.

[0053] Table 1 Component Concentration of nitric oxide 800 ppm oxygen 10 volume% propylene 1714 ppm nitrogen balance water 10 volume% (based on the total volume of the components)

Example 2 After slurrying 0.72 g of the mixed catalyst prepared in Example 1, a commercially available cordierite honeycomb-shaped molded product (diameter: 20 mm, length: 11.5 mm, 400 cells / inch ² )
And dried and fired stepwise to 600 ° C. to prepare an exhaust gas purifying material.

An exhaust gas purifying material was set in the reaction tube. Evaluation was performed using the gas having the composition shown in Table 1 under the same reaction conditions as in Example 1 (the apparent space velocity of the purifying material was about 30,000 h ^-1 ). Table 2 shows the results.

Example 3 In the same manner as in Example 1, commercially available powdered silica-alumina (particle size: 0.1 mm or less, specific surface area: 506 m ² / g, silica / alumina weight ratio = 3: 2) was added to an aqueous chloroplatinic acid solution. After loading 1% by weight (converted to a metal element) of platinum by using, a tungsten oxide is loaded by 5% by weight (converted to a metal element) by using ammonium tungstate. C., and platinum and a W-based catalyst (second catalyst) were prepared.

20 g of the first catalyst and 20 g of the second catalyst of Example 1 were mixed and pulverized into fine powder having an average particle size of 2 μm, and 0.72 g of the mixed catalyst slurried with a binder was added. A commercially available cordierite honeycomb molded body (20 mm in diameter, 11.5 mm in length, 400 cells / inch ² ) was coated, dried, and fired stepwise to 600 ° C. to prepare an exhaust gas purifying material.

An exhaust gas purifying material was set in the reaction tube. Evaluation was performed using the gas having the composition shown in Table 1 under the same reaction conditions as in Example 1 (the apparent space velocity of the purifying material was about 30,000 h ^-1 ). Table 2 shows the results.

Example 4 20 g of the first catalyst of Example 1 and the second catalyst 1 of Example 3
0 g, and pulverized to a fine powder having an average particle size of 2 μm, and then mixed with a binder to form a slurry.
2 g was coated on a commercially available cordierite honeycomb-shaped formed body (diameter 20 mm, length 11.5 mm, 400 cells / inch ² ), dried, and fired stepwise to 600 ° C. to prepare an exhaust gas purifying material.

An exhaust gas purifying material was set in the reaction tube. Evaluation was performed using the gas having the composition shown in Table 1 under the same reaction conditions as in Example 1 (the apparent space velocity of the purifying material was about 30,000 h ^-1 ). Table 2 shows the results.

Example 5 Manganese acetate was calcined in air at 600 ° C., dehydrated,
A manganese oxide (second catalyst) was prepared.

In the same manner as in Example 1, 1% by weight (in terms of metal) of platinum was supported on commercially available powdered silica (particle diameter: 0.1 mm, specific surface area: 200 m ² / g) using an aqueous chloroplatinic acid solution. After drying and firing, a platinum catalyst (third catalyst) was produced.

In the same manner as in Example 3, 0.72 g of the mixed catalyst obtained by mixing 20 g of the first catalyst, 1 g of the second catalyst, and 20 g of the third catalyst in Example 1 was used to form a honeycomb-shaped body. (Diameter: 20 mm, length: 11.5 mm, 400 cells / inch ² ), dried, and fired stepwise to 600 ° C. to prepare an exhaust gas purifying material.

An exhaust gas purifying material was set in the reaction tube. Evaluation was performed using the gas having the composition shown in Table 1 under the same reaction conditions as in Example 1 (the apparent space velocity of the purifying material was about 30,000 h ^-1 ). Table 2 shows the results.

Example 6 Commercially available powdery γ-alumina (particle size: 0.1 mm or less, specific surface area: 245 m ² / g) was added to a solution prepared by adding ammonium molybdate to water, adding oxalic acid, and heating and dissolving. Impregnated, separated from the solution and stepped in air in 600
The temperature was raised to 0 ° C. and the mixture was calcined to prepare a Mo-based catalyst (second catalyst) supporting 5% by weight of molybdenum (in terms of a metal element).

A commercially available powdery γ-alumina (particle size: 0.1 m
m, a specific surface area of 245 m ² / g) is immersed in a chloroplatinic acid aqueous solution for 20 minutes, then dried in air at 80 ° C. for 2 hours, and at a temperature of 120 ° C. for 2 hours under a nitrogen stream at 200 to 400 ° C.
Each step was baked for 1 hour. And 4% hydrogen gas
The temperature was raised from 50 ° C. to 400 ° C. over 5 hours under a nitrogen stream containing, and calcined at 400 ° C. for 4 hours.
The temperature is raised from 50 ° C. to 500 ° C. over 5 hours under a nitrogen stream containing 5% by weight, calcined at 500 ° C. for 5 hours, and 1% by weight of platinum with respect to γ-alumina (in terms of metal element). (Third catalyst) was prepared.

10 g of the first catalyst of Example 1, 5 g of the second catalyst and 1 g of the third catalyst were mixed, a binder was added and kneaded, dried, and gradually heated to 600 ° C. in air. Elevated temperature and calcined to make a mixed catalyst, and diameter 2 ~
It was formed into a 3 mm granular form to produce an exhaust gas purifying material.

1.5 g of the above exhaust gas purifying material was set in the reaction tube. Under the same reaction conditions as in Example 1 (the apparent space velocity of the purifying material is about 30,000 h ^-1 ), Table 1
The evaluation was performed using a gas having the composition shown in FIG. Table 2 shows the results.

Example 7 In the same manner as in Example 1, powdered stannic oxide (specific surface area 71
m ² / g) is immersed in an aqueous solution of Co acetate, then dried, heated to 100 ° C. to 600 ° C. in air in a stepwise manner, and calcined. % (Converted to metal element), to prepare a Co catalyst (first catalyst).

20 g of the first catalyst and 10 g of the second catalyst of Example 1 were mixed and pulverized to a fine powder having an average particle diameter of 2 μm, and a mixed catalyst 0.7
2 g was coated on a commercially available cordierite honeycomb-shaped formed body (diameter 20 mm, length 11.5 mm, 400 cells / inch ² ), dried, and fired stepwise to 600 ° C. to prepare an exhaust gas purifying material.

An exhaust gas purifying material was set in the reaction tube. Evaluation was performed using the gas having the composition shown in Table 1 under the same reaction conditions as in Example 1 (the apparent space velocity of the purifying material was about 30,000 h ^-1 ). Table 2 shows the results.

Comparative Example 1 The platinum catalyst (third catalyst) of Example 5 was formed into granules having a diameter of 2 to 3 mm to produce an exhaust gas purifying material. 1.5 g of exhaust gas purifying material was set in the reaction tube. The same reaction conditions as in Example 1 (the apparent space velocity of the purification material was about 30,000)
h- ¹ ), the evaluation was performed using a gas having a composition shown in Table 1. Table 2 shows the results.

Comparative Example 2 The Co catalyst (first catalyst) of Example 1 was formed into granules having a diameter of 2 to 3 mm to prepare an exhaust gas purifying material. 1.5 g of exhaust gas purifying material was set in the reaction tube. The same reaction conditions as in Example 1 (the apparent space velocity of the purification material was about 30,000)
h- ¹ ), the evaluation was performed using a gas having a composition shown in Table 1. Table 2 shows the results.

Table 2 Nitrogen oxide removal rate (%) Exhaust gas temperature (° C.) 150 200 250 300 350 400 450 Example 1 10 15 30 25 10 10 6 Example 2 14 18 38 33 22 20 16 Example 3 14 30 50 35 22 20 16 Example 4 8 25 64 40 40 30 25 18 Example 5 14 16 35 38 27 20 16 Example 6 8 14 30 26 20 18 10 Example 7 12 18 34 22 22 10 10 6 Comparative Example 10 10 30 20 18 15 8 Comparative Example 2 0 0 2 4 5 10 40

As can be seen from Table 2, Example 1 using the purifying material of the present invention was compared with Comparative Example 1 using a purifying material composed of a platinum catalyst and Comparative Example 2 using a purifying material composed of a Co catalyst. In Nos. To 7, favorable removal of nitrogen oxides was observed in a wide exhaust gas temperature range, particularly in a low temperature range.

[0076]

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.

Claims (7)

[Claims] 1. An exhaust gas purifying material for reducing and removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and oxygen in excess of a theoretical reaction amount with respect to co-existing unburned components. A first catalyst supporting 1 to 20% by weight (in terms of a metal element) and one or more kinds selected from the group consisting of W, V, Mo, Mn, Nb, and Ta on a porous inorganic oxide; A second catalyst supporting 0.2 to 10% by weight of an elemental compound (in terms of a metal element); and a porous inorganic oxide selected from the group consisting of Pt, Pd, Ru, Rh, Ir, and Au. At least one element of 0.05 to 5
An exhaust gas purifying material characterized by being mixed with a third catalyst which carries a weight% (converted to a metal element). 2. An exhaust gas purifying material for reducing and removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and oxygen which is larger than a theoretical reaction amount of coexisting unburned components, wherein a porous inorganic oxide is replaced with a Co oxide. A first catalyst supporting 1 to 20% by weight (in terms of a metal element), W, V, Mo, M
a second catalyst comprising a compound of one or more elements selected from the group consisting of n, Nb, and Ta;
mixing at least one element selected from the group consisting of t, Pd, Ru, Rh, Ir, and Au with a third catalyst supporting 0.05 to 5% by weight (in terms of a metal element); An exhaust gas purifying material comprising: 3. An exhaust gas purifying material for reducing and removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and oxygen which is larger than a theoretical reaction amount of coexisting unburned components, wherein a porous inorganic oxide is replaced by a Co oxide. A first catalyst supporting 1 to 20% by weight (in terms of a metal element), and one or more elements selected from the group consisting of W, V, Mo, Mn, Nb, and Ta on the porous inorganic oxide 0.2 to 10% by weight (in terms of a metal element) of Pt, Pd, Ru, Rh, Ir and A
at least one element selected from the group consisting of
An exhaust gas purifying material characterized by being mixed with a second catalyst supporting 5 to 5% by weight (in terms of a metal element). 4. The exhaust gas purifying material according to claim 1, wherein the porous inorganic oxide is alumina,
Titania, zeolite, silica, zirconia, ZnO,
An exhaust gas purifying material characterized by being one of tin oxide and MgO or a composite or mixed oxide containing them. 5. The exhaust gas purifying material according to claim 1, wherein the catalyst is coated on the surface of a ceramic or metal substrate. 6. The exhaust gas purifying material according to claim 1, wherein the catalyst is formed into a pellet, a granule, a honeycomb, or a plate. 7. A method for reducing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and oxygen which is larger than a theoretical reaction amount of unexisting unburned components using the exhaust gas purifying material according to claim 1. In the exhaust gas purifying method for removing, the exhaust gas purifying material is installed in the middle of an exhaust gas conduit, and the exhaust gas to which hydrocarbons and / or oxygen-containing organic compounds are added on the upstream side of the purifying material is subjected to the purifying material at 150 to 600 ° C. Exhaust gas purifying method, wherein the nitrogen oxides are removed by contact with a hydrocarbon and / or an oxygen-containing organic compound in the exhaust gas.