JPH08150336A - Waste gas purification material and method for purifying waste gas - Google Patents

Abstract

PURPOSE: To obtain a purification material by which NOx is effectively reduced and removed by arranging a 1st catalyst obtd. by carrying silver on a porous inorg. oxide, a 2nd catalyst having a higher silver content and a 3rd catalyst obtd. by carrying copper oxide from the inflow side of waste gas to the outflow side. CONSTITUTION: A 1st catalyst is obtd. by carrying 0.2-12wt.% silver and/or silver compd. or mixture of them as active seeds on a porous inorg. oxide. A 2nd catalyst is similarly obtd. by carrying 0.5-15wt.% silver, etc. A 3rd catalyst is obtd. by carrying 0.2-30wt.% copper oxide and/or copper sulfate as active seeds on a porous inorg. oxide. The 1st, 2nd and 3rd catalysts are arranged from the inflow side of waste gas to the outflow side to obtain the objective purification material. When this material is used, NOx in waste gas contg. excess oxygen is efficiently removed in a wide temp. region.

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 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 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).

However, in these methods, effective removal of nitrogen oxides can be obtained only in a narrow temperature range, and in an exhaust gas containing water, the removal rate of nitrogen oxides is significantly reduced. In other words, it contains about 10% water,
It is difficult to effectively remove nitrogen oxides from exhaust gas from a vehicle or the like whose temperature changes greatly depending on operating conditions.

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 reducing and removing nitrogen oxides.

[0010]

Means for Solving the Problems In view of the above problems, as a result of intensive studies, the present inventor has found that an organic compound such as ethanol is converted to oxygen and nitrogen on a catalyst comprising a porous inorganic oxide carrying a silver component. It has been found that it reacts with exhaust gas containing oxides to reduce nitrogen oxides to nitrogen gas and to generate nitrogen-containing compounds such as nitrites and ammonia and aldehydes as by-products. A second silver-based catalyst capable of effectively removing nitrogen oxides by using the generated aldehyde is further provided, and a copper-based or copper-based or W-based component capable of reducing a nitrogen-containing compound as a by-product to nitrogen is further provided. The catalyst supported on the catalyst and the catalyst supported on the platinum-based component are mixed, and an exhaust gas purifying material formed by combining the two silver-based catalysts and the mixed catalyst is used. Either two or more oxygen-containing organic compounds or a fuel containing them is added, and the exhaust gas is contacted with the above-mentioned purifying material at a specific temperature and space velocity to effectively remove nitrogen oxides in a wide temperature range. It was discovered that the present invention can be performed, and the present invention was 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 that is larger than the theoretical reaction amount of coexisting unburned components is a porous inorganic material. Silver and / or
Or 0.2 to 12% by weight of a silver compound or a mixture thereof
(A silver element conversion value), and a porous inorganic oxide containing silver and / or a silver compound as an active species or a mixture thereof in an amount of 0.5 to 15% by weight (silver element conversion value). )
And a second catalyst supporting a larger amount of the active species than the first catalyst, and a porous inorganic oxide containing copper oxide and / or sulfate as an active species in an amount of 0.2 to 30. weight%
(A copper element conversion value), comprising the first catalyst, the second catalyst and the third catalyst in order from the exhaust gas inflow side to the outflow side of the purifying material. It is characterized by.

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 silver and / or a silver compound or a mixture thereof as an active species is supported on a porous inorganic oxide by 0.2 to 12% by weight (in terms of silver element); Silver and / or a silver compound, or a mixture thereof, in an amount of 0.5 to 15% by weight (in terms of silver element) as an active species and larger than the active catalyst loading rate of the first catalyst. The catalyst is selected from the group consisting of W, V, and Mo, and an oxide of copper and / or sulfate as an active species in the porous inorganic oxide. And at least 30% by weight or less of an oxide or sulfate of at least one element (in terms of a metal element).
It is characterized by having the first catalyst, the second catalyst, and the third catalyst in order from the exhaust gas inflow side to the outflow side of the purification material.

[0013] A 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 for coexisting unburned components,
A first catalyst in which silver and / or a silver compound or a mixture thereof as an active species is supported on a porous inorganic oxide by 0.2 to 12% by weight (in terms of silver element); Silver and / or a silver compound, or a mixture thereof, in an amount of 0.5 to 15% by weight (in terms of silver element) as an active species and larger than the active catalyst loading rate of the first catalyst. A second catalyst, a third catalyst in which a porous inorganic oxide carries copper oxide and / or sulfate as an active species in an amount of 0.2 to 30% by weight (in terms of copper element), and a porous catalyst. At least one element selected from the group consisting of Pt, Pd, Ru, Rh, Ir and Au as active species in the inorganic oxide of 0.01 to 5% by weight
(A metal element conversion value), and the third catalyst and the fourth catalyst are mixed, and the fourth catalyst is sequentially mixed from the exhaust gas inflow side to the outflow side of the purification material. It has one catalyst, the second catalyst, and the mixed catalyst.

A fourth 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 silver and / or a silver compound or a mixture thereof as an active species is supported on a porous inorganic oxide by 0.2 to 12% by weight (in terms of silver element); Silver and / or a silver compound, or a mixture thereof, in an amount of 0.5 to 15% by weight (in terms of silver element) as an active species and larger than the active catalyst loading rate of the first catalyst. The catalyst is selected from the group consisting of W, V, and Mo, and an oxide of copper and / or sulfate as an active species in the porous inorganic oxide. A third catalyst carrying 30% by weight or less of an oxide or sulfate of at least one element (in terms of a metal element); and Pt, Pd, Ru, Rh as active species on a porous inorganic oxide. , At least one element selected from the group consisting of Ir and Au
A fourth catalyst supporting 5% by weight (in terms of a metal element), wherein the third catalyst and the fourth catalyst are mixed, and the purifying material flows from the exhaust gas inflow side to the outflow side; Characterized by having the first catalyst, the second catalyst, and the mixed catalyst in order.

Further, an 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 an amount larger than a 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.

Hereinafter, the present invention will be described in detail. The first exhaust gas purifying material of the present invention comprises a porous inorganic oxide containing silver and / or a silver compound as an active species, or a mixture thereof.
And a silver and / or silver compound as an active species on a porous inorganic oxide, or a mixture of 0.5 to 15% by weight of the first catalyst (to a value of silver element) supported on a porous inorganic oxide. A second catalyst supporting a larger amount than the active species of the first catalyst and an oxide of copper and / or sulfate as an active species on a porous inorganic oxide. And a third catalyst carrying the same.

In the second exhaust gas purifying material of the present invention, a porous inorganic oxide carries 0.2 to 12% by weight (in terms of silver element) of silver and / or a silver compound or a mixture thereof as active species. And a silver and / or silver compound as an active species in a porous inorganic oxide or a mixture thereof in an amount of 0.5 to 15% by weight (in terms of silver element) and A second catalyst supporting a larger amount of the active species than the supported amount, and 0.2 to 30% by weight of copper oxide and / or sulfate as active species on the porous inorganic oxide (in terms of copper element) )
And a third catalyst supporting 30% by weight or less (in terms of metal element) of an oxide or sulfate of at least one element selected from the group consisting of W, V, and Mo.

In the first exhaust gas purifying material and the second exhaust gas purifying material, an exhaust gas purifying material having the first catalyst, the second catalyst, and the third catalyst in order from the exhaust gas inflow side to the outflow side of the purification material. The material is installed in an exhaust gas conduit, and an exhaust gas to which a hydrocarbon and / or an oxygen-containing organic compound having 2 or more carbon atoms or a fuel containing the same has been added is brought into contact with the purification material on the upstream side of the installation position of the purification material. To reduce and remove nitrogen oxides in the exhaust gas. With such an arrangement, nitrogen oxides can be effectively reduced and removed in a wide exhaust gas temperature range.

In the third exhaust gas purifying material of the present invention, a porous inorganic oxide carries 0.2 to 12% by weight (in terms of silver element) of silver and / or a silver compound or a mixture thereof as active species. And a silver and / or silver compound as an active species in a porous inorganic oxide or a mixture thereof in an amount of 0.5 to 15% by weight (in terms of silver element) and A second catalyst supporting a larger amount of the active species than the supporting rate, a third catalyst supporting copper oxide and / or sulfate as the active species on the porous inorganic oxide, At least one element selected from the group consisting of Pt, Pd, Ru, Rh, Ir and Au as active species in the inorganic oxide of high quality 0.01 to
And a fourth catalyst supporting 5% by weight (in terms of metal element).

In the fourth exhaust gas purifying material of the present invention, silver and / or a silver compound or a mixture thereof is contained as an active species in a porous inorganic oxide in an amount of 0.2 to 12% by weight (in terms of silver element). And a silver and / or silver compound as an active species in a porous inorganic oxide or a mixture thereof in an amount of 0.5 to 15% by weight (in terms of silver element) and A second catalyst supporting a larger amount of the active species than the supported amount, and 0.2 to 30% by weight of copper oxide and / or sulfate as active species on the porous inorganic oxide (in terms of copper element) )
A third catalyst supporting 30% by weight or less (in terms of a metal element) of an oxide or sulfate of at least one element selected from the group consisting of W, V, and Mo; A fourth method in which at least one element selected from the group consisting of Pt, Pd, Ru, Rh, Ir, and Au as an active species is supported on the oxide in an amount of 0.01 to 5% by weight (in terms of a metal element). And a catalyst.

In the third exhaust gas purifying material and the fourth exhaust gas purifying material, the third catalyst and the fourth catalyst are mixed, and the first and the fourth catalysts are sequentially mixed from the exhaust gas inflow side to the outflow side of the purification material. The exhaust gas purifying material having the catalyst, the second catalyst, and the mixed catalyst is installed in an exhaust gas conduit, and either one of a hydrocarbon and an oxygen-containing organic compound having 2 or more carbon atoms upstream of the installation position of the purifying material or The exhaust gas to which the fuel containing it is added is brought into contact with the purifying material to reduce and remove nitrogen oxides in the exhaust gas.

The first preferred embodiment of the exhaust gas purifying material of the present invention is a purifying material obtained by coating a purifying material base with a catalyst comprising a powdery porous inorganic oxide carrying catalytically active species. Examples of the ceramic material forming the substrate of the purifying material include porous materials such as γ-alumina and its oxides (γ-alumina-titania, γ-alumina-silica, γ-alumina-zirconia, etc.), zirconia, titania-zirconia, and the like. A heat-resistant material having a large surface area can be used. When high heat resistance is required, it is preferable to use cordierite, mullite, alumina and a composite thereof. 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 are as follows:
Various changes can be made according to the purpose. Practically, at the entrance,
It is preferred that it comprises two or more parts, such as an intermediate part and an outlet part. In addition, as its structure, honeycomb structure type,
Foam type, three-dimensional network structure type made of fibrous refractory,
Alternatively, granules, pellets and the like can be mentioned.

The second preferred form of the exhaust gas purifying material of the present invention is a catalyst comprising a porous inorganic oxide in the form of a pellet or a granular powder carrying a catalytically active species, or a powder comprising a catalytically active species, respectively. It is a purifying material obtained by molding a porous inorganic oxide into pellets or granules into a casing having a desired shape.

The following catalyst is formed on the purifying material of the present invention. (1) First catalyst and second catalyst The first catalyst and the second catalyst are formed by supporting silver and / or a silver compound or a mixture thereof on a porous inorganic oxide, and on the inflow side of the exhaust gas. And acts to remove nitrogen oxides in a wide temperature range. 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, it is preferable to use either alumina or titania or a composite oxide containing them. By using alumina, titania or a composite oxide thereof, the reaction between the added hydrocarbons, oxygen-containing organic compounds and / or residual hydrocarbons in the exhaust gas and nitrogen oxides in the exhaust gas occurs efficiently.

The specific surface area of the porous inorganic oxide such as alumina used for the first catalyst and the second catalyst is 10 m ² / g.
It is preferable that this is the case. 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 preferred specific surface area of the porous inorganic oxide is 30 m ² / g or more.

In the first catalyst, the amount of the silver component supported as an active species on the inorganic oxide such as γ-alumina is 0.2 to 12% by weight (100% by weight of the inorganic oxide). (Element conversion value). If the amount is less than 0.2% by weight, the removal rate of nitrogen oxides decreases. If the silver component is carried in an amount exceeding 12% by weight, the combustion of the hydrocarbon and / or the oxygen-containing organic compound itself tends to occur, and the nitrogen oxide removal rate is rather lowered. A preferable silver component loading is 0.5 to 1
0% by weight.

In the second catalyst, the amount of the silver component supported as an active species on the inorganic oxide such as γ-alumina is 0.5 to 15% by weight (100% by weight of the inorganic oxide). (In terms of element) and more than the loading rate of the active species of the first catalyst. That is, the content of the silver component on the second catalyst is always higher than that on the first catalyst. 0.
If it is less than 5% by weight or less than the active catalyst loading of the first catalyst, the removal of nitrogen oxides using the aldehyde generated by the first catalyst is not performed. If the silver component is carried in an amount exceeding 15% by weight, the combustion of the hydrocarbon and / or the oxygen-containing organic compound itself tends to occur, and the nitrogen oxide removal rate is rather lowered. The loading amount of the silver component in the preferred second catalyst is 1 to 12% by weight.

As a method for supporting silver on an inorganic oxide such as alumina, a known impregnation method, precipitation method, or the like can be used. When using the impregnation method, the porous inorganic oxide is immersed in an aqueous solution of silver nitrate, chloride, sulfate, carbonate, or the like, or an aqueous ammonia solution. Alternatively, the porous inorganic oxide is immersed in an aqueous solution of silver nitrate, dried, and then immersed again in an aqueous solution of ammonium chloride or ammonium sulfate. In the precipitation method, silver nitrate is reacted with ammonium halide to precipitate silver halide on the porous inorganic oxide. This is 50
After drying at about 150 ° C, especially about 70 ° C, 100 to 600
It is preferred to raise the temperature stepwise at a temperature of ° C. and to perform firing. Firing
It is preferable to carry out in air, under a flow of nitrogen containing oxygen or under a flow of hydrogen gas. When the treatment is performed under a hydrogen gas stream, it is preferable to perform the oxidation treatment at 300 to 650 ° C. at last.

It has been observed that a silver component supported on a porous inorganic oxide using an aqueous solution of silver nitrate or the like forms a circular aggregate when fired in an oxidizing atmosphere. In the purification material of the present invention, the average diameter of the silver component aggregate is 10 to 10,000 n
m is preferable. In general, the smaller the diameter of the silver component aggregate, the higher the reaction characteristics, but the average diameter is 10n.
If it is less than m, only the oxidation reaction of the hydrocarbon and / or the oxygen-containing organic compound as the reducing agent proceeds, and the nitrogen oxide removal rate decreases. On the other hand, when the average diameter exceeds 10,000 nm, the reaction characteristics of the silver component are reduced, and the nitrogen oxide removal rate is reduced. The average diameter of the preferred silver component aggregate is 10 to 5
000 nm, more preferably 10 to 2000 nm. Here, the average means an arithmetic average.

When the form of the purifying material is the first preferred embodiment described above, the thicknesses of the first catalyst and the second catalyst provided on the purifying material base are generally the same as those of the base material and this catalyst. Are often limited due to differences in thermal expansion characteristics. 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 washcoat method or the like.

The amount of the first catalyst and the amount of the second catalyst provided on the surface of the purifying material base are respectively 20 to
Preferably it is 300 g / l. The amount of catalyst is 2
If it is less than 0 g / liter, good NOx removal cannot be performed.
On the other hand, when the amount of the catalyst exceeds 300 g / liter, the removal characteristics do not increase so much and the pressure loss increases. More preferably, the first catalyst and the second catalyst provided on the surface of the purifying material base are each 50 to 200 g / liter of the purifying material base.

(2) Third Catalyst The third catalyst comprises a porous inorganic oxide carrying a catalytically active species. As the porous inorganic oxide, it is preferable to use any of alumina, titania and zeolite, a composite oxide containing them, or a mixed oxide thereof. As in the first catalyst, the specific surface area of the porous inorganic oxide is 10
It is preferably at least m ² / g.

In the first and third exhaust gas purifying materials of the present invention, copper oxide and / or sulfate is used as the active species of the third catalyst. Assuming that the porous inorganic oxide is 100% by weight, the supported amount of copper oxide and / or copper sulfate is 0.1%.
It is 2 to 30% by weight (value in terms of metal element). The preferred loading is 0.5 to 25% by weight (in terms of metal element).

In the second and fourth exhaust gas purifying materials of the present invention, the active species of the third catalyst is selected from the group consisting of copper oxides and / or sulfates and W, V and Mo. And oxides or sulfates of at least one element.
Of W, V and Mo, it is preferable to use W and / or V. Assuming that the porous inorganic oxide is 100% by weight, the supported amount of copper oxide and / or copper sulfate is 0.2 to 30% by weight.
(Converted to metal element), and the amount of the W-based component carried is 30% by weight or less (converted to metal element). The total amount of the copper component and the W-based component is 0.2 to 60% by weight (converted to metal element) (converted to metal element). The preferred loading amount of the copper component is 0.5 to 25% by weight (in terms of a metal element),
The preferred loading of the W-based component is 25% by weight or less (in terms of a metal element), and the preferred total loading of the copper component and the W-based component is 0.5 to 50% by weight (in terms of a metal element).
By using the third catalyst, nitrogen oxides can be reduced by reducing nitrogen oxides and nitrogen-containing compounds generated by the first catalyst, such as nitrites and ammonia, to nitrogen.

For supporting the active species on the third catalyst, a known impregnation method, precipitation method or the like can be used. When using the impregnation method, the porous inorganic oxide is immersed in an aqueous solution of a carbonate, nitrate, acetate, sulfate or the like of the catalytically active species element. In the case of a copper component, an aqueous solution such as copper sulfate or copper nitrate is used. W,
In the case of V or Mo, a porous inorganic oxide is immersed in an aqueous solution of an ammonium salt, oxalate or the like of each element for use. 50
After drying at ~ 150 ° C, especially at 70 ° C, the temperature is raised stepwise at 100-600 ° C and firing is performed. This calcination is performed in air under a nitrogen stream containing oxygen. It is also an effective method to use metatitanic acid (hydrous titanium oxide) as a starting material instead of titania and to carry V, W, and Mo.

When the form of the purifying material is the above-described first preferred embodiment, the thickness of the third catalyst provided on the purifying material base is preferably 300 μm or less. Further, the amount of the third catalyst provided on the surface of the purifying material base is preferably 20 to 300 g / liter of the purifying material base.

(3) Fourth Catalyst The fourth catalyst comprises a porous inorganic oxide carrying catalytically active species and is formed on the exhaust gas outflow side, and acts to remove nitrogen oxides in a low temperature region. And at the same time, oxidize and remove carbon monoxide and hydrocarbons. As the porous inorganic oxide, it is preferable to use one or more oxides or composite oxides selected from the group consisting of alumina, titania, zirconia, silica, and zeolite. Similar to the first catalyst, the specific surface area of the porous inorganic oxide is preferably 10 m ² / g or more.

The active species of the fourth catalyst include Pt, P
d, Ru, Rh, using at least one element selected from the group consisting of Ir and Au, it is preferable to use at least one of Pt, Pd, Ru, Rh and Au, particularly at least Pt, Pd and Au One is preferred. The sum of the active species supported on the inorganic oxide by the fourth catalyst is based on the above-mentioned porous inorganic oxide.
(100% by weight) is 0.01 to 5% by weight, preferably 0.01 to 4% by weight. Even when the amount of the catalytically active species exceeds 5% by weight of the porous inorganic oxide, the performance of removing nitrogen oxides is not improved.

The active species of the fourth catalyst may further include at least one selected from the group consisting of rare earth elements such as La and Ce, alkaline earth elements such as Ca and Mg, and alkali metal elements such as Na and K. It is preferable to carry one or more elements in an amount of 10% by weight or less. By supporting a rare earth, alkaline earth, or alkali metal element, the heat resistance of a platinum-based catalyst can be improved.

For supporting the active species on the fourth catalyst, a known impregnation method, precipitation method or the like can be used. When using the impregnation method, the porous inorganic oxide is immersed in an aqueous solution such as a chloride or hexachlorometallic acid of a catalytically active species element, dried at 70 ° C., and then gradually heated at 100 to 700 ° C. and fired. This is done by: The calcination is performed under a nitrogen stream or a hydrogen-containing or oxygen-containing nitrogen stream. Preferably, the calcination is performed under a nitrogen stream, and then the calcination is performed under a hydrogen-containing nitrogen stream or an oxygen-containing nitrogen stream. Although the Pt-based loading component is shown as a metal element, the loading component exists in a state of a metal and an oxide under a normal use temperature condition of the purification material.

When the form of the purifying material is the first preferred embodiment described above, the thickness of the fourth catalyst provided on the purifying material base is preferably 300 μm or less. The amount of the fourth catalyst provided on the surface of the purifying material base is preferably 20 to 300 g / liter based on the purifying material base.

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 1:
It is preferably 10 to 10: 1. When the ratio is less than 1:10 (the amount of the first catalyst is small), 150 to 600 ° C.
Over a wide temperature range, the purification rate of nitrogen oxides decreases overall. On the other hand, if the ratio exceeds 10: 1 and the amount of the second catalyst is small, the aldehyde formed on the first catalyst is not effectively used for reducing nitrogen oxides. A more preferred weight ratio of the first catalyst to the second catalyst is 1: 5 to 5: 1.

In the first and second exhaust gas purifying materials of the present invention, the ratio of the total weight of the first catalyst and the second catalyst to the weight of the third catalyst (porous inorganic oxide and catalytically active species) Is preferably 10: 1 to 1: 5. When the ratio is less than 1: 5 (the amount of the first catalyst and the amount of the second catalyst are small), the purification rate of nitrogen oxides is generally reduced in a wide temperature range of 150 to 600 ° C. On the other hand, if the ratio is 1
When the ratio exceeds 0: 1 and the amount of the third catalyst is small, nitrite and ammonia formed on the first catalyst are not effectively used for reducing nitrogen oxides. More preferably, the weight ratio of the total weight of the first catalyst and the second catalyst to the weight of the third catalyst is 5: 1 to 1: 1.
1: 4.

In the third and fourth exhaust gas purifying materials of the present invention, the third catalyst and the fourth catalyst are mixed and used. By this mixing, the reducing action of the third catalyst and the oxidizing action of the fourth catalyst can proceed simultaneously without affecting each other. When the purifying material is the first preferred embodiment, the thickness of the mixed catalyst of the third catalyst and the fourth catalyst provided on the purifying material base is preferably 300 μm or less. In addition, the amount of the mixed catalyst of the third catalyst and the fourth catalyst provided on the surface of the purifying material base is preferably 20 to 300 g / liter with respect to the purifying material base.

The weight ratio of the third catalyst to the fourth catalyst (ratio of the total weight of the porous inorganic oxide and the catalytically active species) is 10
The ratio is preferably set to 0: 1 to 100: 50. If the amount of the fourth catalyst is less than 1 part by weight based on 100 parts by weight of the third catalyst, the removal rate of hydrocarbons and carbon monoxide decreases. On the other hand, 50 parts of the fourth catalyst is added to 100 parts by weight of the third catalyst.
If the amount is more than 100 parts by weight, the purification rate of nitrogen oxides is lowered as a whole in a wide temperature range of 150 to 600 ° C. More preferably, the weight ratio of the third catalyst to the fourth catalyst is 100: 1 to 10
0:30.

The total weight of the first and second catalysts,
The ratio of the weight of the mixed catalyst of the third catalyst and the fourth catalyst (the ratio of the total weight of the porous inorganic oxide to the catalytically active species) is 1
It is preferable that the ratio be 0: 1 to 1: 5. When the ratio is less than 1: 5 (the amount of the first catalyst and the second catalyst is small), 15
In a wide temperature range of 0 to 600 ° C., the purification rate of nitrogen oxides is reduced as a whole. On the other hand, if the ratio exceeds 10: 1 and the amount of the mixed catalyst is small, nitrite and ammonia formed on the first catalyst are not effectively used for reduction of nitrogen oxides.
Further, the removal rates of carbon monoxide and hydrocarbons are reduced. More preferably, the weight ratio of the total weight of the first catalyst and the second catalyst to the weight of the mixed catalyst is 5: 1 to 1: 4.

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.

Next, the method of the present invention will be described. First, when the first and second exhaust gas purifying materials of the present invention are used, the first catalyst, the second catalyst, and the third catalyst are installed in the exhaust gas conduit in order from the exhaust gas inflow side to the outflow side of the purifying material. I do.

When the third and fourth exhaust gas purifying materials of the present invention are used, the first catalyst, the second catalyst, the third catalyst and the fourth catalyst are sequentially arranged from the exhaust gas inflow side to the outflow side of the purifying material. The mixed catalyst is installed in the middle of the exhaust gas conduit.

Although the exhaust gas contains ethylene, propylene and the like to some extent as residual hydrocarbons, it is generally not enough to reduce NOx in the exhaust gas. A compound, 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 introduction position of the reducing agent
It is upstream from 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, in the case of an alkane or alkene, it preferably has 2 or more carbon atoms. Specific examples of hydrocarbons that are liquid in the standard state include gas oil, cetane,
Examples include hydrocarbons such as heptane, kerosene, gasoline and the like.
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 hydrocarbon and / or oxygen-containing organic compound introduced from the outside is determined by the weight ratio (weight of added reducing agent / weight).
(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 in the first catalyst and the second catalyst is set so that the reduction and removal of nitrogen oxides by an oxygen-containing organic compound, hydrocarbon, nitrite, ammonia or the like proceed efficiently. 150,000h ^-1 each
Or less, preferably 100,000 h ^-1 or less. When the space velocity of the first catalyst and the second catalyst exceeds 150,000 h ^-1 ,
The reduction reaction of nitrogen oxides does not sufficiently occur, and the nitrogen oxide removal rate decreases. Space velocity of the mixed catalyst of the third catalyst or third catalyst and a fourth catalyst 200,000 ^-1 or less, preferably 150,000H ^-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 300 to 500C.

[0057]

The present invention will be described in more detail with reference to the following specific examples. Example 1 A commercially available γ-alumina powder (specific surface area: 200 m ² / g) was immersed in an aqueous silver nitrate solution, taken out, and dried at 70 ° C. for 2 hours. Then, the temperature is raised stepwise to 600 ° C. in the air, and calcined for 5 hours.
A first catalyst supporting silver by weight (in terms of a metal element) was prepared. 0.26 g of the first catalyst was charged with a commercially available cordierite honeycomb formed body (diameter 20 mm, length 8.3 m).
m, 400 cells / inch ² ) and after drying 600
The mixture was baked stepwise to ℃ to prepare a silver-based purifying material (a purifying material coated with a first catalyst).

In the same manner as in the above-mentioned silver-based catalyst, a second catalyst in which 5.0% by weight (in terms of a metal element) of silver was supported on powdered alumina was prepared. 0.26 g of the second catalyst was coated, and a second silver-based purifying material (a purifying material coated with the second catalyst) was prepared in the same manner.

Next, powdery titania (specific surface area: 50 m ² / g) is immersed in an aqueous solution of copper sulfate (copper concentration: 7.7% by weight), and is immersed in air at 80 ° C., 100 ° C. and 120 ° C. for 2 hours each. Dried. Subsequently, under a nitrogen stream containing 20% of oxygen, 12
The temperature was raised stepwise from 0 ° C. to 500 ° C. and calcined at 500 ° C. for 5 hours to prepare a third catalyst supporting 4.4% by weight of copper sulfate (converted to copper element) with respect to titania. A honeycomb formed body similar to the above-mentioned silver-based purifying material was coated with 0.26 g of a third catalyst slurried, dried and calcined under the same conditions as the silver-based purifying material to obtain a copper-based purifying material (third catalyst). Was prepared.

A silver-based purifying material, a second silver-based purifying material, and a copper-based purifying material were set in order from the inflow side to the outflow side of the exhaust gas in the reaction tube. Next, a gas (nitrogen monoxide, oxygen, ethanol, sulfur dioxide, nitrogen and moisture) having a composition shown in Table 1 was flowed at a flow rate of 3.48 liters per minute (standard state) (apparent space velocity of each purification material). Were about 80,000 h ^-1 ), and the temperature of the exhaust gas in the reaction tube was kept in the range of 350 to 550 ° C., and ethanol and nitrogen oxides were reacted.

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.

Table 1 Component concentration Nitric oxide 800 ppm Oxygen 10% by volume Ethanol 1560 ppm Sulfur dioxide 30 ppm Nitrogen Residual water 10% by volume (based on the total volume of the above components)

Example 2 Water was added to ammonium paratungstate parapentahydrate and oxalic acid, dissolved by heating on a water bath, and then added to a cooled aqueous solution (tungsten concentration: 15.5% by weight) to obtain a powdery titania. (Specific surface area: 50 m ² / g) and immersed for 20 minutes. Thereafter, the titania was separated from the solution, and dried in air at 80 ° C, 100 ° C, and 120 ° C for 2 hours each.
Subsequently, the temperature is changed from 120 ° C. to 5 ° C under a nitrogen stream containing 20% of oxygen.
The temperature was raised to 00 ° C. in 5 hours and calcined at 500 ° C. for 4 hours to prepare a W-based catalyst supporting 7.4% by weight (in terms of metal element) of an oxide of W with respect to titania. This catalyst was immersed in an aqueous solution of copper sulfate (copper concentration: 9.0% by weight) for 20 minutes, and dried and calcined in the same manner as the third catalyst of Example 1, to obtain 7.4 oxides of W against titania. A third catalyst supporting 3 wt% of copper sulfate and 3.7 wt% of copper sulfate (in terms of a metal element) was prepared. After slurrying 0.26 g of the third catalyst, it was coated on the honeycomb formed body in the same manner as in Example 1, dried and fired, and a copper and W-based purification material (a purification material coated with the third catalyst) was used. ) Was prepared.

The silver-based purifying material of Example 1, the second silver-based purifying material of Example 1, the copper, and the W-based purifying material were set in this order from the inflow side to the outflow side of the exhaust gas in the reaction tube. The same reaction conditions as in Example 1 (the apparent space velocities of the respective purifying materials were about 8
(At 0000 h ⁻¹ )), and the evaluation was performed using a gas having a composition shown in Table 1. Table 2 shows the results.

Example 3 Oxalic acid was added to vanadium pentoxide and dissolved by heating on a water bath, and then cooled and cooled (a vanadium concentration of 7.8).
% By weight), powdered titania (specific surface area: 50 m ² / g)
, And immersed for 20 minutes. Thereafter, the titania was separated from the solution, and dried in air at 80 ° C, 100 ° C, and 120 ° C for 2 hours each. Subsequently, the temperature was increased from 120 ° C. to 500 ° C. in 5 hours under a nitrogen stream containing 20% of oxygen, and 50 ° C.
By calcining at 0 ° C. for 4 hours, a V-based catalyst carrying 3.8% by weight (converted to metal element) of V oxide with respect to titania was prepared. 3.3 g of this V-based catalyst (3.1 m in apparent volume)
l) was immersed in an aqueous copper sulfate solution (copper concentration: 9.0% by weight) for 20 minutes, and dried and calcined in the same manner as the third catalyst of Example 1, to obtain an oxide of V against titania of 3.8. A third catalyst was prepared, which supported 4.0% by weight of copper sulfate and 4.0% by weight of copper sulfate (in terms of metal element). After slurrying 0.26 g of the third catalyst, it was coated on the honeycomb formed body in the same manner as in Example 1, dried and fired, and then a copper and V-based purification material (a purification material coated with the third catalyst). ) Was prepared.

The silver-based purifying material of Example 1, the second silver-based purifying material of Example 1, the copper and V-based purifying materials were set in this order from the inflow side of the exhaust gas in the reaction tube to the outflow side. The same reaction conditions as in Example 1 (the apparent space velocities of the respective purifying materials were about 8
(At 0000 h ⁻¹ )), and the evaluation was performed using a gas having a composition shown in Table 1. Table 2 shows the results.

Example 4 3.3 g of V-based catalyst prepared in Example 3 (apparent volume: 3.
1 ml) in an aqueous solution of copper nitrate (copper concentration 9.5% by weight).
For 3 minutes, and then dried and calcined in the same manner as the third catalyst of Example 1. 3.8% by weight of oxide of V and 4.5% by weight of oxide of copper with respect to titania (value in terms of metal element) ) Was prepared. After slurrying 0.26 g of the third catalyst, it was coated on the honeycomb formed body in the same manner as in Example 1, dried and fired, and then a copper and V-based purification material (a purification material coated with the third catalyst). ) Was prepared.

The silver-based purifying material of Example 1, the second silver-based purifying material of Example 1, the above-mentioned copper and V-based purifying materials were set in order from the inflow side to the outflow side of the exhaust gas in the reaction tube. The same reaction conditions as in Example 1 (the apparent space velocities of the respective purifying materials were about 8
(At 0000 h ⁻¹ )), and the evaluation was performed using a gas having a composition shown in Table 1. Table 2 shows the results.

Example 5 Powdered titania was immersed in an aqueous copper nitrate solution (copper concentration: 9.5% by weight) for 20 minutes in the same manner as in Example 1, and dried in the same manner as in the third catalyst of Example 1. It was calcined to prepare a third catalyst which supported 4.5% by weight (in terms of metal element) of copper oxide with respect to titania.

The above second catalyst and the 0.1.
After slurrying 26 g of the third catalyst, the mixed catalyst was coated on the formed honeycomb body in the same manner as in Example 1, dried, and dried.
Firing was performed to prepare a copper-based purifying material (a purifying material coated with a third catalyst).

The silver-based purifying material of Example 1, the second silver-based purifying material of Example 1, and the copper-based purifying material were set in order from the inflow side to the outflow side of the exhaust gas in the reaction tube. The same reaction conditions as in Example 1 (the apparent space velocities of the respective purifying materials were about 80, respectively)
000 h ⁻¹ ), and evaluation was performed using a gas having a composition shown in Table 1. Table 2 shows the results.

Example 6 The same titania as the third catalyst of Example 1 was immersed in a chloroplatinic acid aqueous solution for 20 minutes, dried in air at 80 ° C. for 2 hours, and then at 120 ° C. for 2 hours in a nitrogen stream. , 200-400
Calcination was carried out stepwise for 1 hour up to ° C. And hydrogen gas 4
% Under a nitrogen stream containing 5% over a period of 5 hours from 50 ° C to 400 ° C, and calcined at 400 ° C for 4 hours.
The temperature was raised from 50 ° C. to 500 ° C. over 5 hours under a nitrogen stream containing 0%, and calcined at 500 ° C. for 5 hours.
A fourth catalyst carrying 0.21% by weight of Pt (in terms of a metal element) was prepared.

The second catalyst and the third catalyst were mixed and slurried so that the weight ratio of the third catalyst and the fourth catalyst in Example 1 was 40: 1. A honeycomb formed body similar to the silver-based purifying material was coated with 0.26 g of the mixed catalyst. Drying and baking were performed under the same conditions as those of the silver-based purifying material of Example 1 to prepare copper and platinum-based purifying materials (purifying materials coated with third and fourth catalysts).

The silver-based purifying material of Example 1, the second silver-based purifying material of Example 1, and the copper and platinum-based purifying materials were set in this order from the inflow side to the outflow side of the exhaust gas 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 each purification material was about 80,000 h ^-1 ). Table 2 shows the results.

Example 7 A slurry was prepared by mixing the third catalyst prepared in Example 2 and the fourth catalyst prepared in Example 6 in a weight ratio of 40: 1, and the mixture was mixed with Example 6 to obtain a slurry. In the same manner, a honeycomb formed body was coated with 0.26 g of the mixed catalyst, dried and fired,
Copper, W, and platinum-based purifying materials (purifying materials coated with third and fourth catalysts) were prepared.

The silver-based purifying material of Example 1, the second silver-based purifying material of Example 1, and the copper, W, and platinum-based purifying materials were set in this order from the inflow side to the outflow side of the exhaust gas in the reaction tube. Example 1
Evaluation was carried out under the same reaction conditions as described above (the apparent space velocity of each purifying material was about 80,000 h ^-1 ) using a gas having a composition shown in Table 1. Table 2 shows the results.

Example 8 The third catalyst prepared in Example 3 and the fourth catalyst prepared in Example 6 were mixed at a weight ratio of 20: 1 to form a slurry. In the same manner, a honeycomb formed body was coated with 0.26 g of the mixed catalyst, dried and fired,
Copper, V, and platinum-based purifying materials (purifying materials coated with third and fourth catalysts) were prepared.

The silver-based purifying material of Example 1, the second silver-based purifying material of Example 1, and the copper, V, and platinum-based purifying materials were set in this order from the inflow side to the outflow side of the exhaust gas in the reaction tube. Example 1
Evaluation was carried out under the same reaction conditions as described above (the apparent space velocity of each purifying material was about 80,000 h ^-1 ) using a gas having a composition shown in Table 1. Table 2 shows the results.

Example 9 The third catalyst prepared in Example 4 and the fourth catalyst prepared in Example 6 were mixed at a weight ratio of 20: 1 to form a slurry. In the same manner, a honeycomb formed body was coated with 0.26 g of the mixed catalyst, dried and fired,
Copper, V, and platinum-based purifying materials (purifying materials coated with third and fourth catalysts) were prepared.

The silver-based purifying material of Example 1, the second silver-based purifying material of Example 1, and the copper, V, and platinum-based purifying materials were set in this order from the inflow side to the outflow side of the exhaust gas in the reaction tube. Example 1
Evaluation was carried out under the same reaction conditions as described above (the apparent space velocity of each purifying material was about 80,000 h ^-1 ) using a gas having a composition shown in Table 1. Table 2 shows the results.

Example 10 The third catalyst prepared in Example 5 and the fourth catalyst prepared in Example 6 were mixed at a weight ratio of 20: 1 to form a slurry. In the same manner, a honeycomb formed body was coated with 0.26 g of the mixed catalyst, dried and fired,
Copper and platinum-based purifying materials (purifying materials coated with third and fourth catalysts) were prepared.

The silver-based purifying material of Example 1, the second silver-based purifying material of Example 1, and the copper and platinum-based purifying materials were set in this order from the inflow side to the outflow side of the exhaust gas 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 each purification material was about 80,000 h ^-1 ). Table 2 shows the results.

Comparative Example 1 The same honeycomb formed body was coated with 0.52 g of the first catalyst prepared in Example 1, dried and fired to prepare a silver-based purifying material. Set the silver purifying material in the exhaust gas conduit,
The same reaction conditions as in Example 1 (apparent space velocity was about 80,
000 h ⁻¹ ), and evaluation was performed using a gas having a composition shown in Table 1. Table 2 shows the results.

Table 2 Removal rate of nitrogen oxides (NOx) Removal rate of nitrogen oxides (%) Reaction temperature (° C.) 300 350 400 450 500 Example 1 55.8 82.5 97.7 96.5 93.6 Example 2 67.4 78.8 92.1 95.9 88.8 Example 3 68.1 76.5 88.7 93.6 83.2 Example 4 62.8 78.7 90.8 93.1 83.6 Example 5 23.4 56.5 67.4 80.3 80.3 Example 6 59.8 82.5 95.7 96.5 90.6 Example 7 68.4 78.8 92.1 94.9 83.8 Example 8 68.1 76.5 88.7 92.6 80.2 Example 9 66.8 78.7 90.8 92.1 80.6 Example 10 28.4 58.5 67.4 75.3 78.3 Comparative Example 1 20.5 30.5 35.7 42.6 40.5

As can be seen from Table 2, in Examples 1 to 10, good removal of nitrogen oxides was observed in a wide exhaust gas temperature range as compared with Comparative Example 1 using only a silver catalyst.

[0086]

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.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location B01J 23/40 A 23/42 23/48 A 23/648 23/652 23/72 A 27/053 A 27/055 A 27/08 A 27/18 A B01D 53/36 102 A 102 B B01J 23/64 102 A 103 A (72) Inventor Masataka Koyama 4-1-1, Suehiro, Kumagaya-shi, Saitama, Japan Co., Ltd. Inside the Riken Kumagaya Plant (72) Mika Saito 4-1-1, Suehiro, Kumagaya City, Saitama Prefecture Inside the Riken Kumagaya Plant (72) Kiyohide Yoshida 4-1-1, Suehiro Kumagaya City, Saitama Stock Company (72) Inventor Tatsuo Miyadera 16-3 Onogawa, Tsukuba City, Ibaraki Pref.

Claims (10)

[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 the theoretical reaction amount of coexisting unburned components, wherein the porous inorganic oxides are used as active species. 0.2 to 12% by weight of silver and / or a silver compound or a mixture thereof (in terms of silver element)
And a silver and / or silver compound as an active species in a porous inorganic oxide, or a mixture thereof in an amount of 0.5 to 15% by weight (in terms of silver element) and the first catalyst. A second catalyst supporting a larger amount of the active species than the active species of the catalyst, and 0.2 to 30% by weight of copper oxide and / or sulfate as active species on a porous inorganic oxide (copper element) (Converted value), the first catalyst, the second catalyst, and the third catalyst in order from the exhaust gas inflow side to the outflow side of the purification material. Exhaust gas purifying material. 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 the porous inorganic oxides are used as active species. 0.2 to 12% by weight of silver and / or a silver compound or a mixture thereof (in terms of silver element)
And a silver and / or silver compound as an active species in a porous inorganic oxide, or a mixture thereof in an amount of 0.5 to 15% by weight (in terms of silver element) and the first catalyst. A second catalyst supporting a larger amount of the active species than the active species of the catalyst, and 0.2 to 30% by weight of copper oxide and / or sulfate as active species on a porous inorganic oxide (copper element) Conversion value)
And a third catalyst carrying 30% by weight or less (in terms of a metal element) of an oxide or sulfate of at least one element selected from the group consisting of W, V, and Mo. An exhaust gas purifying material comprising the first catalyst, the second catalyst, and the third catalyst in order from the exhaust gas inflow side to the outflow side. 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 the porous inorganic oxides are used as active species. 0.2 to 12% by weight of silver and / or a silver compound or a mixture thereof (in terms of silver element)
And a silver and / or silver compound as an active species in a porous inorganic oxide, or a mixture thereof in an amount of 0.5 to 15% by weight (in terms of silver element) and the first catalyst. A second catalyst supporting a larger amount of the active species than the active species of the catalyst, and 0.2 to 30% by weight of copper oxide and / or sulfate as active species on a porous inorganic oxide (copper element) (Converted value) and at least one element selected from the group consisting of Pt, Pd, Ru, Rh, Ir and Au as active species in a porous inorganic oxide. -5% by weight (in terms of a metal element), the fourth catalyst being mixed with the third catalyst and the fourth catalyst. An exhaust gas purifying material comprising the first catalyst, the second catalyst, and the mixed catalyst in this order. 4. 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 for coexisting unburned components, wherein the porous inorganic oxides have an active species as active species. 0.2 to 12% by weight of silver and / or a silver compound or a mixture thereof (in terms of silver element)
And a silver and / or silver compound as an active species in a porous inorganic oxide, or a mixture thereof in an amount of 0.5 to 15% by weight (in terms of silver element) and the first catalyst. A second catalyst supporting a larger amount of the active species than the active species of the catalyst, and 0.2 to 30% by weight of copper oxide and / or sulfate as active species on the porous inorganic oxide (copper element) Conversion value)
A third catalyst supporting 30% by weight or less (in terms of a metal element) of an oxide or sulfate of at least one element selected from the group consisting of W, V, and Mo; A fourth method in which at least one element selected from the group consisting of Pt, Pd, Ru, Rh, Ir, and Au as an active species is supported on the oxide in an amount of 0.01 to 5% by weight (in terms of a metal element). And the third catalyst and the fourth catalyst are mixed, and the first catalyst, the second catalyst, and the mixed catalyst are arranged in order from the exhaust gas inflow side to the outflow side of the purification material. An exhaust gas purifying material characterized by having. 5. The exhaust gas purifying material according to claim 3, wherein the weight ratio of the third catalyst to the fourth catalyst is 10%.
An exhaust gas purifying material having a ratio of 0: 1 to 100: 50. 6. The exhaust gas purifying material according to claim 1, wherein at least one of the first, second, third, and fourth catalysts is a ceramic or metal substrate. An exhaust gas purifying material characterized by being coated on the surface. 7. The exhaust gas purifying material according to claim 1, wherein at least one of the first, second, third and fourth catalysts is in the form of pellets or granules. An exhaust gas purifying material characterized by the following. 8. The exhaust gas purifying material according to claim 1, wherein the silver compound is at least one selected from the group consisting of silver oxide, silver halide, silver sulfate and silver phosphate. An exhaust gas purifying material characterized by that: 9. The exhaust gas purifying material according to claim 1, wherein said porous inorganic oxide is alumina or titania or a composite oxide containing them for the first and second catalysts. , The third catalyst is alumina, titania and zeolite, or a composite oxide containing them or a mixed oxide thereof, and the fourth catalyst is alumina, titania, zirconia, silica, and one selected from the group consisting of zeolites. An exhaust gas purifying material comprising the above oxide. 10. A method for reducing nitrogen oxides from a combustion exhaust gas containing the nitrogen oxides and oxygen that is larger than the theoretical reaction amount of unexisting unburned components using the exhaust gas purifying material according to claim 1. Description: 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.