JPH11128736A - Adsorbent for nitrogen oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively adsorb and remove NOx without previously adding O2 to a gas to be treated when the NOx included in the gas to be treated is adsorbed and removed. SOLUTION: This adsorbent contains one or more selected from the group of Mn oxide, Mn-Cu combined oxides and Mn-Fe combined oxides and an alkali or alkaline earth metal salt of ruthenium acid. Alternatively, in addition to those, an alkali metal compound other than the above is added to form this adsorbent that has a high nitrogen oxide removing efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to nitric oxide (N
O) and nitrogen oxides (NO ₂ ) such as nitrogen dioxide (NO ₂ )
_x ), for adsorbents for removing, particularly, N contained in ventilation exhaust gas from automobile tunnels, underground parking lots, etc.
The O _x efficiently adsorbed and removed relates _the NO _x adsorption material that is used to prevent air pollution.

[0002]

2. Description of the Related Art Automobile tunnels and underground car parking lots,
Ventilation exhaust from the room or the like having a harmful gas generating device is a room temperature, low concentration of NO _x, instantaneous concentration fluctuation is large and the like and is much different from the properties of the flue gas in the incineration facilities. For this reason, in order to remove harmful gas from these ventilation gases, ammonia (NH ₃ ) is used on a denitration catalyst containing titania (TiO ₂ ) as a main component, which is conventionally used for flue exhaust gas from incinerators and the like. Catalytic reduction method (NH ₃ ) for selectively reducing to nitrogen (N ₂ )
Reduction denitration method) cannot be applied as it is. Therefore, for the NO _x in the ventilation gas, this was allowed to temporarily adsorbed through appropriate _the NO _x adsorbing agent, by thermal desorption to obtain a high concentration of NO _x, applying the NH ₃ reducing denitration method Was thought. Then, as the _the NO _x adsorbing agent used in such methods are known adsorbents such as described below.

[0003] It contains oxides such as Na, Ca, etc.
An activated alumina (Al ₂ O ₃ ) -based NO _x adsorbent having an enhanced adsorption activity by containing an oxide such as n, Fe or Cu (Japanese Patent Application Laid-Open No. Hei 4-367707).

An anatase-type TiO ₂ carrier has R
u low concentration _the NO _x adsorbing agent was supported (ruthenium) (JP-A-5-123568).

[0005] At least one noble metal selected from Pt, Au, Ru, Rh and Pd, or a compound thereof is supported on a carrier, or the noble metal component is combined with Mn, Fe, Co, Ni, Cu, Zn, etc. Adsorbent for NO _x , especially NO ₂ (Japanese Patent Application Laid-Open No. 7-88363), wherein the metal oxide is supported on a carrier as required.

Γ-M having a specific surface area of 100 m ² / g or more
NO whose main component is nO _2-x (where 0 ≦ x ≦ 0.1)
_x Oxidation adsorbent (JP-A-8-173796).

Mn—Cu composite oxide and / or M
_the NO _x adsorbing agent containing n-Fe composite oxide and a Ru compound, or Mn oxide, at least one member selected from the group consisting of Mn-Cu composite oxide and Mn-Fe complex oxide, a Ru compound , NO _x adsorbent containing an alkali metal compound and / or Sn compound (International Publication WO97 / 11779).

[0008] manganese oxide containing Mn oxide, or Cu or Fe,, NO _x, which was supported Ru compounds
Adsorbent (Japanese Patent Application Laid-Open No. 9-141088).

However, the above NO_x Adsorbents ~ each
There are the following problems. Adsorbent is NO_x Adsorbent
But practically NO_Two Only adsorption capacity for
I do not have. NO contained in the ventilation gas etc._x Most of
Is NO, NO _Two Is generally all NO_x Number of concentrations to 10
In many cases, it only accounts for about%. Therefore, of
When an adsorbent is used, ozone (O
_Three ) To convert NO to NO_Two Need to be oxidized. This
When O_Three Insufficient NO will leave unoxidized NO
Enough NO_x Removal performance cannot be obtained. On the contrary, O_Three 
Is added in excess, excess O_Three Released as harmful gas
Will be done. Also O_Three Regardless of the amount added
And O from the processing equipment_Three The danger of leakage cannot be denied. Only
NO adsorbed on this adsorbent_x 4 to remove
It must be processed at temperatures as high as 50 ° C.

[0010] While the there is a sorbent also _the NO _x adsorbing agent, the distinction between NO and NO ₂ not at all made, adsorption performance of NO is unknown. This adsorbent also requires a high temperature treatment of about 350 ° C. for desorption and regeneration.

It is described that the adsorbent also has an adsorbing ability for NO, but the NO adsorbing ability is much lower than the NO ₂ adsorbing ability (duration of performance is short). Therefore, as in the case of the adsorbent described above, O ₃
Pre-oxidation treatment by addition is required.

Further, by using the adsorbent which does not exhibit practical removal performance unless after oxidized to once NO ₂ to NO, is oxidized on the total amount of NO to the NO _2, NO that can not be adsorbed and removed ₂ will be discharged. N in gases to be treated, such as ventilation gases in car tunnels and underground parking
O ₂ concentration, since if lower than the NO concentration is almost, unless very high adsorption performance of NO _2, NO ₂
May hardly decrease or may increase.
Therefore, there is basically a problem as an adsorbent for removing NO ₂ , which is a harmful gas whose regulation value is set by environmental standards.

In addition, most of the gases to be treated, such as ventilation gases in car tunnels and underground parking lots, contain sulfur oxides (SO
_x ), that is, sulfur dioxide (SO ₂ ) and sulfur trioxide (SO ₃ ), and the concentration of SO _x is generally NO _x
, But produces many metals and accumulative sulfur compounds (sulfates, etc.). Since the above adsorbents are mainly composed of metals that easily generate sulfur compounds, such as heavy metal oxides, activated alumina, and Ru compounds, performance degradation (poisoning) due to SO _x is a problem. Become.

In the case of the oxidizing adsorbent, most of NO is N
Since it is oxidized and released to O ₂ and only a part of NO is adsorbed, a separate NO ₂ adsorbing section must be provided on the downstream side. Therefore also in this case, as with the above, the adsorbent, if significantly increased the NO ₂ adsorption performance can not be obtained NO _x removal effect satisfactory.

Although the adsorbent is much superior to the above adsorbents in that it has high NO and NO ₂ adsorption activity, it still has points to be improved. First, R
Even if u exists in a metal or oxide state, the intended effect is not exhibited, and chloride (RuCl ₃ ) or nitrate is considered to be desirable. Since these substances are acidic compounds, basic compounds such as Mn oxide and Mn-C
When kneaded or impregnated with the u composite oxide or the Mn-Fe composite oxide, the Ru compound tends to agglomerate on the Mn oxide surface and tends to be difficult to be uniformly dispersed. That is, it becomes difficult to obtain an active point having a high surface area. In addition, the loading of an alkali metal compound such as potassium carbonate has the effect of increasing the adsorption performance, but it causes a decrease in the strength of the molded body such as pellets, or when the moisture absorption of the molded body at high humidity advances, Dissolution occurs, which also causes pores to be closed. For this reason, the amount of the alkali metal compound to be carried is limited, and sufficient care must be taken in the carrying method.

Moreover, the above adsorbent adsorbs NO after oxidizing it. Therefore, when a gas containing only NO is treated,
Some NO ₂ that could not be adsorbed leaks to the outlet side.
Although this concentration is normally at a level that does not cause any problem, NO that is not directly regulated is converted to N that is a direct environmental control substance.
It is difficult to say that the removal in place of O ₂ is a preferable method. Also have substantially the same problems as the adsorbents described above.

[0017]

The present invention 0005] is, which has been made in view of the problems of such conventional techniques described above, and its object is adsorbent used for the removal of noxious gases of the NO _x mainly is the to eliminate such problems described above pointed out, for example, in removing adsorbing NO _x in the treated gas, without causing leakage even addition of NO ₂ without addition of O ₃ in advance in the gas to be treated , it is intended to provide _the NO _x adsorption material that can be a NO _x efficiently adsorbed and removed.

[0018]

_The NO _x adsorbing agent according to the present invention which could achieve the above object, according to an aspect of the, Mn oxide, M
At least one selected from the group consisting of an n-Cu composite oxide and a Mn-Fe composite oxide, and an alkali or alkaline earth metal salt of ruthenic acid, or a Mn oxide, a Mn-Cu composite oxide and Mn-Fe
At least one selected from the group consisting of composite oxides,
It is characterized by containing an alkali metal compound other than the above, together with an alkali or alkaline earth metal salt of ruthenic acid.

In the present invention, the Mn-Cu composite oxide having a mass ratio of [Mn / (Mn + Cu)] of 0.15 or more, more preferably 0.45 to 0.95, is used. As the Mn-Fe composite oxide, [M
n / (Mn + Fe)] mass ratio is 0.10 or more, more preferably by using one of 0.30 to 0.85, it is possible to secure the higher levels of performance as _the NO _x adsorbing agent.

The content of the ruthenate in the adsorbent is 0.05% by mass or more, preferably 0.10% by mass or more, more preferably 0.1% by mass or less in terms of ruthenium metal.
It is 30% by mass or more, and its upper limit is about 2% by mass. Among the above-mentioned ruthenates, potassium ruthenate and sodium ruthenate are particularly preferable, and these can be used alone, and it is also effective to use two kinds in combination as necessary.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The adsorbent of the present invention has an M
n-oxide, Mn-Cu composite oxide and Mn-Fe composite oxide, together with at least one selected from the group consisting of ruthenic acid and alkali or alkaline earth metal salts, characterized in that it contains This adsorbent is clearly evident in the following Examples, as compared with the harmful gas remover described in the above-mentioned WO 97/11779, that is, “NO _x adsorbent containing a Ru compound such as RuCl ₃ or ruthenium nitrate”. As a result, it has a remarkably excellent NO _x adsorption performance.

[0022] Here in _the NO _x adsorbing performance, high NO _x That total adsorption removal rate of "NO + NO _2", more preferably release rate of NO ₂ is low is and the immediate environment controlled substances, the average NO _X removal The rate and average NO ₂ release rate are calculated by the following equations. Average NO _x removal rate = (1 - outlet average concentration of NO _x / inlet average concentration of NO _x) × 100 [%] Average NO ₂ release rate = (outlet average NO ₂ concentration / inlet Average N
_Ox concentration) x 100 [%]

The infrared absorption spectrum in the state of adsorbing NO and NO ₂ and the NO absorption in heating the adsorbent after adsorption
And the desorption temperature characteristics of NO ₂ are the same, and the action and effect of the Ru compound are determined from the UV-visible absorption spectrum and the infrared absorption spectrum of the substance extracted from the adsorbent after the NO _x removal (adsorption) treatment. Is determined to be due to the formation of the nitrosyl complex. The ease with which Ru compounds form nitrosyl complexes is described, for example, in Cotton Wilkinson, "Inorganic Chemistry (2nd volume)", Baifukan, p. 894 (1
973), and when Ru coexists with nitric acid, a nitrosyl complex is formed. As a prerequisite for its generation, it is necessary that NO is oxidized to NO ₂ and further reacts with coexisting water to generate nitrate ions (NO ₃ ⁻ ). In fact, the effect of the Ru compound is that It is effective only when moisture is present in the gas. Also,
Assuming that the difference in the removal amount (adsorption amount) depending on the presence or absence of the Ru compound is simply due to the formation of a nitrosyl complex, R
This means that about 10 molecules of NO (or a substance derived from NO) are retained per atom of u at a maximum, which is not explained. That is, the nitrosyl complex of Ru is one of Ru
Only about 1 to 6 molecules of NO (or NO-derived product) should be coordinated per atom. Nevertheless, to improve significantly _the NO _x adsorption effect as will be described later, inevitably considered that NO oxidation ability or adsorption ability of the Mn oxide itself by the coexistence of a Ru compound is increased.

On the other hand, the reason why the adsorbent of the present invention exhibits much superior NO _x adsorption performance as compared with the adsorbent described in the above-mentioned WO 97/11779, for example, is Mn.
It is considered that the alkali or alkaline earth metal salt of ruthenic acid contained together with the oxide is a basic substance. That is, the above-mentioned Mn oxide is a basic substance, and if the substance to be kneaded or impregnated with these basic substances is an acidic substance such as RuCl ₃ or ruthenium nitrate, for example, these are added to the surface of the oxide. While easily agglomerated, alkali or alkaline earth metal salts of ruthenic acid are hardly aggregated on the surface of the oxide because they are basic substances, and are substantially uniformly dispersed throughout the oxide to substantially adsorb active sites. It is considered that the surface area is increased and a high adsorption performance is exhibited.

Ru in RuCl ₃ or ruthenium nitrate is +3, whereas Ru in alkali or alkaline earth metal salts of ruthenic acid is +3 in a highly oxidized state.
It is hexavalent and the oxidation activity itself is much stronger. Therefore NO
It is thought that oxidation to NO ⁺ easily occurs, and the formation of the Ru nitrosyl complex is accelerated, which contributes to the improvement of the adsorption performance. In fact, when comparing the case where RuCl ₃ is supported and the case where ruthenate is supported, the amount of NO adsorbed per 100 g of the adsorbent is at most 1. In the latter, it is confirmed that 1.9 to 2.3 g is adsorbed, while only 1 to 1.3 g.

Such an effect can be exhibited effectively when the Mn oxide and the alkali or alkaline earth metal salt of ruthenic acid are present (coexisting) in the same adsorbent. Is passed through an adsorbent composed of Mn oxide or the like, and then passed through the above ruthenate.
When n oxide and ruthenate do not coexist,
Such an effect cannot be obtained, and even more, when only one of the Mn oxide or the like and the ruthenate is present,
Such an effect cannot be obtained.

That is, the adsorbent of the present invention exhibits excellent removal performance due to the synergistic effect of the above Mn oxide and ruthenate. It also has the effect of being able to use repeatedly by regenerating hot air at a low temperature (for example, about 200 ° C.).

According to further studies by the present inventors, when a Mn-Cu composite oxide or a Mn-Fe composite oxide was used instead of the Mn oxide, an oxide of Mn alone was used. It was confirmed that more excellent removal activity was obtained than in the case. Here, the composite oxide is not a simple mixture of two types of metal oxides, but another type of oxide in which a bond between both metals is formed via an O atom.

The above composite oxide can be typically produced by the following coprecipitation method. That is, an alkali is added to an aqueous solution in which salts of two metals are dissolved, and a precipitate in which hydroxides of both metals are mixed on a molecular scale is formed, and the precipitate is oxidized to obtain a composite oxide. In this case, it is not sufficient to mechanically mix the powder or slurry of the hydroxides of both metals, and a large difference appears in the oxidation performance of NO.

The effect of the composite oxide is considered to be based on the following reasons. That is, by making a composite oxide, O atoms in the oxide are easily moved, and donation of O atoms in the oxide and replenishment of O atoms from O ₂ in the air become easy.
It is considered that the catalytic ability is improved.

Here, the content of Mn in the composite oxide of Cu and Mn should be 0.15 or more, more preferably 0.45 or more, in terms of Mn / (Cu + Mn) (mass ratio). If it is less than 15, the adsorption performance will be inferior to that of the oxide of Mn alone due to the shortage of Mn. However, if the mass ratio is too high, it becomes difficult to effectively exhibit the composite effect with Cu, and the adsorbing performance tends to decrease. Therefore, it is preferable to suppress the mass ratio to 0.95 or less.
Similarly, the content of Mn in the composite oxide of Fe and Mn is 0.10 or more in Mn / (Fe + Mn) (mass ratio),
More preferably 0.30 or more, and a preferable upper limit is 0.85.
It is.

In still another configuration of the present invention, in addition to the above-mentioned Mn oxide, Mn-Cu composite oxide or Mn-Fe composite oxide and an alkali or alkaline earth metal salt of ruthenic acid, an alkali other than the above is further added. by blending a metal compound, it is possible to further improve the performance as _the NO _x adsorption material.

That is, when an appropriate amount of an alkali metal compound, preferably an alkali metal hydroxide, carbonate, bicarbonate, or the like is used in addition to the above Mn oxide or composite oxide and ruthenate, the gas to be treated becomes Poisoning of the adsorbent by coexisting SO _x is suppressed, and an effect of increasing durability is exhibited, and an effect of enhancing SO _x removal performance is also obtained. That is, the activity of oxidizing SO ₂ to SO ₃ is remarkable in the Mn oxide and the composite oxide, and the SO ₃ generated by the oxidation is
Reacts with coexisting moisture to produce sulfuric acid. And
If you leave the presence of an alkali metal compound in the adsorbent of the present invention are easily suppressed sulfating the Mn oxides to produce sulfates, moreover, since the SO ₃ is removed as alkaline sulfate, SO _x Adsorption performance is also improved. On the other hand, when the alkali metal compound does not coexist, the above S
Since the Mn oxide and the composite oxide are gradually sulfated by O ₃ , the catalytic activity of the Mn oxide and the composite oxide is reduced. That is, an alkali metal compound, suppresses the deterioration of the NO _x adsorption performance by suppressing the poisoning of the adsorbent due to high SO _x be mixed into the gas to be treated, and also very effective in increasing the SO _x removal performance Become.

As the alkali metal compound, hydroxide, carbonate and bicarbonate are preferred.
Among the alkali metals constituting the alkali metal compound, particularly preferred are potassium and sodium.
The preferred content of the alkali metal compound in the adsorbent of the present invention is 0.1 to 6.0% by mass in terms of alkali metal.
If the content is less than 0.1% by mass, it is difficult to exert a significant effect of improving the performance, and if the content is more than 6.0% by mass, no further improvement effect can be obtained. This tends to adversely affect the adsorption performance.
From such a viewpoint, a more preferable content of the alkali metal compound is in a range of 0.5 to 4.0% by mass in terms of the alkali metal.

Examples of the alkali metal constituting the ruthenate include Na, K, Rb and the like, and examples of the alkaline earth metal include Ca, Ba, Sr and the like. ₂ RuO ₄ ) and K (K
₂ RuO ₄ ) is recommended as a particularly preferred ruthenate. Therefore, these ruthenates have high solubility in water, can be easily supported on Mn oxides and composite oxides by a kneading method, an impregnation method, and the like, and can be obtained at relatively low cost.

The preferable content of the above ruthenate in the adsorbent according to the present invention is 0.05% by mass or more in terms of ruthenium metal, and when it is less than 0.05% by mass, sufficient NO _x adsorption performance is obtained. Tends to be difficult to obtain. However, even if it is added in excess of about 2% by mass,
Further improvement in NO _x adsorption performance is not recognized, which is uneconomical. The lower limit of the content is more preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and the preferable upper limit is 1.5% by mass in consideration of both the adsorption performance and the economic efficiency.

There is no particular limitation on the shape of the adsorbent according to the present invention. The adsorbent may be formed into granules or tablets by extrusion molding or tableting, or into a honeycomb or sheet by extrusion molding or papermaking. The molding method and shape may be appropriately selected according to the purpose of use. The molding of the adsorbent
After forming Mn or a hydroxide or carbonate of Cu or Fe and an oxide or a composite oxide, Mn may be performed at any stage. However, since ruthenate is an expensive raw material, Mn oxide or composite oxide may be used. It is preferable that the oxide is supported near the surface of a molded body made of an oxide. For this purpose, it is preferable to perform a molding treatment before supporting the ruthenate. In any case, adopting the molding treatment such as not to high temperature firing after loading of ruthenium salt is preferable for enhancing _the NO _x adsorbing performance.
Also, when an alkali metal compound is carried, it is desirable to carry the alkali metal compound after forming the molded body in order to make them exist on the surface layer side of the molded body and effectively exhibit the combined effect.

As described above, the NO _x adsorbent according to the present invention is filled into a processing vessel in an arbitrary shape and structure, and the gas to be processed is caused to flow through the packed bed at an appropriate space velocity.
It adsorbs and removes O _x , and the performance of the adsorbent affects the effective contact area with the gas to be treated. From such a viewpoint, the NO _x adsorbent of the present invention has a specific surface area of 70%.
m ² / g or more, more preferably 1
00m ² / g or more, further preferably 120 m ² / g or more.

[0039]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and the present invention is not limited thereto. Of course, the present invention can be embodied with modifications, all of which are included in the technical scope of the present invention.

Example 1 670 g of manganese nitrate [Mn (NO ₃ ) ₂ .6H ₂ O]
Was weighed into a 5 liter beaker, 2 liters of pure water was added thereto, and the mixture was stirred and dissolved to obtain a precipitated mother liquor (solution A). On the other hand, 137 g of potassium hydroxide (KOH) was weighed and added to a 2 liter beaker containing 1 liter of pure water with stirring to dissolve, thereby preparing a precipitant solution (solution B). The solution A and the solution B were simultaneously added to a 5 liter beaker containing 1 liter of pure water with stirring to prepare a precipitate of manganese hydroxide at a constant pH.

At the same time, 74 g of potassium permanganate (KMnO ₄ ) was weighed into a 2 liter beaker, and 2 liters of pure water was added thereto and dissolved by stirring to obtain an aqueous solution of potassium permanganate. Next, after this aqueous solution was added to the manganese hydroxide precipitate with stirring, stirring was continued for 60 minutes to oxidize the manganese hydroxide in the liquid phase.
Next, the obtained precipitate of manganese oxide was repeatedly filtered and washed with water to remove impurities. After washing with water, the precipitate was transferred to a drier and dried at 110 ° C. for 20 hours. Thereafter, the manganese oxide was crushed into granules, a small amount of graphite was added as a lubricant and mixed, and then tablets having a diameter of 1/8 inch were produced by a tableting machine.

A 40 cc aqueous solution containing 1.63 g of potassium ruthenate (K ₂ RuO ₄ ) was prepared, and the manganese oxide tablet was supported on the manganese oxide tablet by a spray method. The adsorbent of Example 1 was obtained by drying under conditions. The composition of this adsorbent is
Mn: 66.1% by mass, Ru: 0.30% by mass,
The specific surface area is 110 m ² / g and the pore volume is 0.46 cc /
g.

Example 2 In Example 1, potassium ruthenate (K ₂ R) was used.
uO ₄ ) instead of a 40 cc aqueous solution containing 1.63 g,
1.40% sodium ruthenate (Na ₂ RuO ₄ )
The adsorbent of Example 2 was obtained in exactly the same manner as in Example 1 except that a 40 cc aqueous solution containing g was used. The composition of this adsorbent was Mn: 66.2% by mass, Ru: 0.29% by mass, the specific surface area was 103 m ² / g, and the pore volume was 0.44 cc / g.

Comparative Example 1 In Example 1, potassium ruthenate (K ₂ R) was used.
uO ₄ ) instead of a 40 cc aqueous solution containing 1.63 g,
Example 1 except that a ruthenium chloride aqueous solution in which 1.39 g of ruthenium chloride was dissolved in 30 cc of pure water was used.
And the adsorbent of Comparative Example 1 was obtained. The composition of the adsorbent was Mn: 65.8% by mass, Ru: 0.30% by mass, the specific surface area was 105 m ² / g, and the pore volume was 0.1%.
It was 44 cc / g.

Example 3 Manganese sulfate [MnSO_Four ・ 5H_Two O] 380g and sulfuric acid
Copper (CuSO_Four ・ 5H _Two O) 125 g to 5 liter
Weigh it into a car and add 2 liters of pure water to it.
Then, the mixture was stirred and dissolved to give a precipitated mother liquor (solution A). On the other hand, hydroxyl
Weigh 230 g of sodium chloride (NaOH) and add 1 l of pure water.
In a 2 liter beaker containing
The NaOH was completely dissolved and the precipitant solution (B
Liquid). Next, while stirring the solution A, add the solution B
Manganese hydroxide and copper hydroxide
And the addition of solution B was completed in about 60 minutes.
Was.

Next, in order to oxidize this coprecipitate in the liquid phase, ammonium persulfate [(NH ₄ ) ₂ S ₂ O ₈ ] was used.
An aqueous solution was prepared by dissolving 210 g in pure water to make 2 liters.
The coprecipitate was gradually added to the slurry and kept under stirring for 60 minutes to perform a liquid phase oxidation treatment of the coprecipitate. Then
The oxidized product was filtered and washed repeatedly to remove impurities. After washing, the product was transferred to a drier and dried. The dried product is uniformly mixed with alumina sol (# 200, manufactured by Nissan Chemical Industries, Ltd.) while adjusting the water content as necessary to obtain a water condition suitable for wet molding, and this is 1/8 inch in diameter by a screw extruder. Into an extruded product. After completion of the molding process, the product was dried at 110 ° C. for 20 hours in a drier to obtain Mn.
-An extruded product of a Cu composite oxide was obtained.

A 40 cc aqueous solution containing 1.63 g of potassium ruthenate (K ₂ RuO ₄ ) was prepared and supported on the extruded composite oxide by a spray method. The adsorbent of Example 3 was obtained by drying under the condition of time. The composition of this adsorbent is as follows: Mn: 52.8% by mass, Cu: 13.2% by mass, R
u: 0.30% by mass, and the specific surface area is 160 m ² /
g and the pore volume were 0.45 cc / g.

Comparative Example 2 In Example 3, potassium ruthenate (K ₂ R) was used.
uO ₄ ) instead of a 40 cc aqueous solution containing 1.63 g,
Example 3 except that a ruthenium chloride aqueous solution in which 1.39 g of ruthenium chloride was dissolved in 30 cc of pure water was used.
And the adsorbent of Comparative Example 2 was obtained. The composition of this adsorbent was Mn: 53.9% by mass, Cu: 13.6% by mass, Ru: 0.29% by mass, and the specific surface area was 154 m.
² / g and the pore volume was 0.43 cc / g.

Example 4 In the wet kneading before extrusion molding of the liquid phase oxidized composite oxide in Example 3, potassium carbonate 3.0 was used.
g was added, and otherwise the procedure of Example 3 was repeated to obtain an adsorbent of Example 4. The composition of this adsorbent is Mn: 5
3.0% by mass, Cu: 12.9% by mass, Ru: 0.30
% By mass, K: 0.69% by mass, and the specific surface area was 141.
m ² / g, and the pore volume was 0.40 cc / g.

COMPARATIVE EXAMPLE 3 In the wet kneading before extrusion molding the liquid phase oxidized composite oxide in Comparative Example 2, potassium carbonate was added to 3.0.
g was added and the other conditions were the same as in Comparative Example 2 to obtain an adsorbent of Comparative Example 3. The composition of this adsorbent is Mn: 5
3.2% by mass, Cu: 13.1% by mass, Ru: 0.29
% By mass, K: 0.73% by mass, and the specific surface area was 135.
m ² / g, and the pore volume was 0.38 cc / g.

[0051] Example 5 manganese sulfate 143g of ferrous sulfate (FeSO ₄ · 7H
₂ O) Weigh 487 g into a 5 liter beaker,
After adding 2 liters of pure water thereto, the mixture was stirred and dissolved to obtain a precipitated mother liquor (solution A). On the other hand, 303 g of sodium carbonate was weighed, added to a 2 liter beaker containing 1 liter of pure water with stirring to dissolve, and a precipitant solution (solution B) was prepared. Next, while stirring the solution A, the solution B obtained above was added thereto to form a coprecipitate comprising a basic carbonate of manganese and iron, and the addition of the solution B was completed in about 60 minutes. Then, while stirring the coprecipitate slurry, 2 liters of an aqueous solution obtained by diluting 210 g of ammonium persulfate with pure water was added thereto,
The mixture was kept under stirring for 60 minutes to complete the liquid phase oxidation treatment of the coprecipitate to obtain a Mn-Fe composite oxide slurry. The slurry was filtered, washed with water, dried, and then crushed to obtain granules. A small amount of graphite was added to the granules and mixed.

Next, this tablet was treated in the same manner as in Example 1 above.
And potassium ruthenate (K _Two RuO_Four ) To 1.
Carrying 40cc aqueous solution containing 63g by spray method
After drying, dry at 110 ° C for 4 hours using a dryer.
Thereby, the adsorbent of Example 5 was obtained. This set of adsorbents
The composition was as follows: Mn: 20.7% by mass, Fe: 44.9% by mass,
Ru: 0.30% by mass, specific surface area: 125 m^Two /
g and the pore volume were 0.41 cc / g.

Comparative Example 4 In Example 5, potassium ruthenate (K ₂ R) was used.
uO ₄ ) instead of a 40 cc aqueous solution containing 1.63 g,
Example 5 except that a ruthenium chloride aqueous solution in which 1.39 g of ruthenium chloride was dissolved in 30 cc of pure water was used.
The adsorbent of Comparative Example 4 was obtained in exactly the same manner as in Example 1. The composition of the adsorbent was Mn: 21.1% by mass, Fe: 44.6% by mass, Ru: 0.31% by mass, and the specific surface area was 122 m2.
² / g and the pore volume was 0.38 cc / g.

Performance Evaluation Experiment 1 Each of the adsorbents of Examples 1 to 5 and Comparative Examples 1 to 4 was prepared by attaching a water-cooled jacket and a heater so that adsorption removal at a constant temperature and regeneration at a constant temperature could be performed. Stainless steel adsorption tube "and fill it with NO _x
The adsorption performance was measured. That is, "Adsorbent filling amount: 16.0 c
m ³ (filling height: 6.0 cm), supply gas composition: NO _x
5.0 ppm in total (internal division: NO: 4.5 ppm, NO
₂ : 0.5 ppm; air balance), supply gas flow rate: 1
0.4 Nl / min (space velocity: 40000 h ^-1 ), adsorption temperature: 35 ° C., humidity: 60% (relative humidity), time: 6
Gas under the condition of “time”, and the NO concentration and N
The O _x concentration (ie, NO + NO ₂ concentration) was continuously measured with a chemiluminescence analyzer. Then, the average NO _x adsorption rate for 6 hours and the average NO ₂ release rate for 6 hours for each adsorbent were determined by the following equations. Average NO _x adsorption rate = (1−average NO _x concentration at outlet / N at inlet)
O _x concentration) × 100 (%) Mean NO ₂ release rate = (outlet average NO ₂ concentration / inlet NO _x
Concentration) x 100 (%)

The results are as shown in Table 1._Three 
K instead of_Two RuO_Four Or Na_TwoRuO_Four Use
NO_x As the adsorption rate is further increased,
NO _Two It can be seen that the release rate is further reduced. Also,
When combined with an alkali metal compound in an amount, NO_x Of adsorption rate
Further improvement and NO_Two A reduced emission rate is realized.

[0056]

[Table 1]

Performance Evaluation Experiment 2 The adsorbents of Example 3 and Comparative Example 2 were used, and their NO and NO ₂ removal performance was evaluated by adjusting the supply gas flow rate to 15.6.
Nl / min (space velocity: 60000 h ^-1 ), 18.2
Nl / min (same as: 70000 h ^-1 ) or 20.8
Nl / min (same as above: 80000h ^-1 )
The measurement was performed in the same manner as in the performance evaluation experiment 1, and the results shown in Table 2 were obtained.

[0058]

[Table 2]

As is evident from Table 2, the adsorbent of Example 3 has a higher NO _x removal rate and a lower NO ₂ emission rate even at twice the space velocity of the adsorbent of Comparative Example 2. Have been. As is clear from this table, RuCl ₃
When K ₂ RuO ₄ is used instead of NOx, the same level of NO _x
It can be seen that the amount of adsorbent used to obtain the removal rate and the NO ₂ release rate can be reduced to about half or less.

[0060] in Example 6-11 Example 3, in place of the "aqueous solution of 40cc containing 1.63g of K ₂ RuO _4", the "K ₂ RuO ₄ 0.
27g, 0.54g, 2.72g, 5.43g, 8.1
The adsorbents of Examples 6 to 11 were obtained in the same manner except that "40 cc aqueous solution containing 5 g or 10.9 g" was used.

Comparative Example 5 An adsorbent (extruded product) of Comparative Example 5 was obtained in the same manner as in Example 3 except that the extruded product in Example 3 was not sprayed with K ₂ RuO ₄ . . The composition of the adsorbent was Mn: 52.8% by mass, Cu: 13.4% by mass, Al: 2.8% by mass, and the specific surface area was 150 m ^2.
/ G, pore volume was 0.44 cc / g.

[0062] For each adsorbent performance evaluation tests 3 above Examples 6 to 11 and Comparative Example 5, in the same manner as in the above performance evaluation test 1 to measure _the NO _x adsorption performance and NO ₂ release rate, the results shown in Table 3 I got

[0063]

[Table 3]

[0064] As is clear from Table 3, the adsorbent of the embodiment, it can be seen that excellent _the NO _x adsorption performance and much lower NO ₂ release rate compared to the adsorbent of the comparative example.

Examples 12 to 17 and Comparative Example 6 The amount of manganese sulfate-copper sulfate-sodium hydroxide used in Example 3 was 460 g-0 g-220 g, 42
0g-60g-220g, 340g-180g-220
g, 238g-315g-233g, 95g-504g
-217g, 40g-550g-220g and 0g-
Changed from 600 g to 220 g, and otherwise changed to Example 3
In the same manner as in Example 1, adsorbents of Examples 12 to 17 and Comparative Example 6 were obtained.

[Performance Evaluation Experiment 4] The above Examples 12 to 1
NO of adsorbent of Comparative Example 7 and Comparative Example_x Adsorption performance and NO
_Two The release rate was measured in the same manner as in the performance evaluation experiment 1,
The results shown in Table 4 were obtained.

[0067]

[Table 4]

As is evident from Table 4, the adsorbents of the respective examples show an excellent NO _x adsorption rate and a low NO ₂ emission rate, but the comparative examples containing no manganese oxide. It can be seen that the adsorbent No. 6 has an extremely low NO _x removal rate. Further, Mn-Cu composite mass ratio of Mn in the oxide 0.15 or more, more preferably those in 0.45 to 0.95, it is seen that the more excellent _the NO _x adsorption rate.

Examples 18 to 22 and Comparative Example 7 The amount of manganese sulfate-ferrous sulfate-sodium hydroxide used in Example 5 was 505 g-0 g-300 g,
425g-110g-300g, 333g-210g-
317 g, 48 g-626 g-287 g, 25 g-65
Example 1 was changed to 0 g-300 g and 0 g-680 g-300 g in the same manner as in Example 5 except for the above.
8 to 22 and Comparative Example 7 were obtained.

[Performance Evaluation Experiment 5] The above Examples 18 to 2
NO of adsorbent of Comparative Example 2 and Comparative Example 7_x Adsorption performance and NO
_Two The release rate was measured in the same manner as in the performance evaluation experiment 1,
The results shown in Table 5 were obtained.

[0071]

[Table 5]

[0072] As is clear from Table 5, Comparative Example adsorbent each embodiment shows _the NO _x adsorption rate and a low NO ₂ release rate excellent none but does not contain manganese oxide It can be seen that the adsorbent No. 7 has an extremely low NO _x removal rate. Further, Mn-Fe composite mass ratio of Mn in the oxide 0.05 or more, more preferably those in 0.30 to 0.85, it is seen that the more excellent _the NO _x adsorption rate.

[0073]

According to _the NO _x adsorbing agent of the present invention as described above, according to the present invention, the adsorption removal of the NO _x in the treated gas can be performed in a large space velocity as compared to the conventional adsorbents, also NO _Two
Since the release rate is suppressed as much as possible, it is possible to significantly reduce the size of the adsorption device and to improve the economic efficiency by reducing the amount of the adsorbent used.

Continued on the front page (72) Inventor Takefumi Yamashita 1-5-5 Takatsukadai, Nishi-ku, Kobe City Inside Kobe Research Institute, Kobe Steel Ltd. (72) Inventor Yoshiyuki Toyama 3-9 Kudanminami, Chiyoda-ku, Tokyo No. 14 Nissan Gardler Catalyst Co., Ltd. (72) Inventor Hidetaka Shibano 635 Sasakura, Funaka-machi, Nigane-gun, Toyama Pref. 635 Nissan Gadler Catalyst Co., Ltd.

Claims (5)

[Claims] 1. A composition comprising at least one selected from the group consisting of Mn oxides, Mn-Cu composite oxides and Mn-Fe composite oxides, and an alkali or alkaline earth metal salt of ruthenic acid. Adsorbent for nitrogen oxides. 2. An alkali or alkaline earth metal salt of ruthenic acid, at least one selected from the group consisting of a Mn oxide, a Mn—Cu composite oxide and a Mn—Fe composite oxide, and an alkali metal other than the above. A nitrogen oxide adsorbent characterized by containing a compound. 3. [M] in the Mn—Cu composite oxide
n / (Mn + Cu)] is 0.15 or more,
[Mn / (Mn + Fe)] in n-Fe composite oxide
3. The adsorbent for nitrogen oxides according to claim 1, wherein the mass ratio is 0.10 or more. 4. 4. The adsorbent for nitrogen oxides according to claim 1, wherein the content of the ruthenate in the adsorbent is 0.05% by mass or more in terms of ruthenium metal. 5. The nitrogen oxide adsorbent according to claim 1, wherein the ruthenate is potassium ruthenate and / or sodium ruthenate.