JP3148155B2 - Adsorbent for nitrogen oxides and / or sulfur oxides and method of using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to adsorption and removal of nitrogen oxides and / or sulfur oxides (hereinafter sometimes abbreviated as "nitrogen oxides"). Specifically, the present invention
The present invention relates to adsorption and removal of low-concentration nitrogen oxides and / or sulfur oxides contained in exhaust gas.

[0002]

2. Description of the Related Art With respect to a method of removing nitrogen oxides from a fixed nitrogen oxide source such as a boiler, conventionally, ammonia has been selectively reduced by using ammonia as a reducing agent to remove harmless nitrogen. The catalytic reduction method of converting to water is widely used as the most economical method.

Meanwhile, the concentration of nitrogen oxides and the like contained in ventilation gas or air in road tunnels, sheltered roads, deep underground spaces, road intersections, etc., and gas exhausted from combustion equipment used in homes. Is
The concentration is about 5 ppm, which is significantly lower than the concentration of nitrogen oxides and the like in the boiler exhaust gas, the gas temperature is room temperature, and the amount of gas is enormous. For this reason, for example, in order to efficiently remove nitrogen oxides and the like by applying the above-described catalytic reduction method to the ventilation gas of a road tunnel, it is necessary to set the temperature of the ventilation gas to 300 ° C. or more, and as a result, Since a large amount of energy is required, it is economically problematic to apply the above catalytic reduction method as it is. Under such circumstances, it is desired to efficiently remove nitrogen oxides and the like from exhaust gas having a low concentration of the nitrogen oxides and the like, for example, about 5 ppm or less, such as the ventilation gas of the road tunnel as described above.

Accordingly, the present inventors have previously proposed an adsorbent suitable for adsorbing and removing nitrogen oxides from the exhaust gas containing low concentrations of nitrogen oxides as described above (Japanese Patent Laid-Open No. 7-883).
No. 63).

[0005]

When a gas after ventilation of a tunnel is treated using a nitrogen oxide adsorbent, it is necessary to treat the gas in the tunnel, so that the installation space is limited and the apparatus itself is made compact. There is a need. For this reason,
It is desirable that the adsorbent used has excellent nitrogen oxide adsorbing ability.

Further, since the exhaust gas contains water vapor in addition to the nitrogen oxides, the adsorbents such as nitrogen oxides to be used are those which are hardly affected by these coexisting gases. desirable.

It is already known that an adsorbent containing an alkali is excellent in adsorbing nitrogen oxides, particularly nitrogen dioxide. However, an adsorbent containing an alkali cannot be heated and regenerated. Required complicated treatment such as removing the adsorbed substance by washing with water and then re-adding the alkali.

Thus, the present invention provides an adsorbent, such as nitrogen oxide, which is excellent in the ability to adsorb nitrogen oxides and the like, is not easily affected by coexisting gas, and can maintain high performance for a long time, especially 5 ppm or less in exhaust gas. An object of the present invention is to provide an adsorbent such as a nitrogen oxide suitable for adsorbing and removing a nitrogen oxide or the like having a low concentration.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that at least one element selected from the group consisting of titanium, zirconium, silicon, and aluminum and an alkali metal element A nitrogen oxide and / or sulfur oxide adsorbent containing at least one element and at least one element selected from the group consisting of manganese, copper, nickel, cobalt, iron, chromium, and lead; The adsorbent has specific pores, and has found a method for adsorbing nitrogen oxides and the like using the adsorbent, thereby completing the invention. More specifically, it is specified as follows.

(1) At least one element selected from the group consisting of titanium, zirconium, silicon, and aluminum, at least one element of an alkali metal element, and manganese, copper, nickel, cobalt, iron, chromium, and lead at least containing the one element, deer selected
Also has a specific surface area of at least 10 m ² / g and a total pore volume of 0.15
cc / g or more and having a pore size in the range of 0.05 to 4 μm
A nitrogen oxide and / or sulfur oxide adsorbent, characterized in that the pore volume is 10% or more of the total pore volume .

(2) The adsorbent according to the above (1), which further contains an alkaline earth metal element.

[0012]

(3) Contacting the adsorbent according to (1) or (2) with a gas containing nitrogen oxides and / or sulfur oxides to remove nitrogen oxides and / or sulfur oxides. The use of an adsorbent characterized by the following.

(4) a step of contacting the adsorbent according to the above (1) with a gas containing nitrogen oxides and / or sulfur oxides to adsorb the nitrogen oxides and / or sulfur oxides, and the adsorption A method for using an adsorbent, comprising repeating the step of heating the adsorbent to remove the adsorbed nitrogen oxides and detoxifying the adsorbent.

[0015]

DETAILED DESCRIPTION OF THE INVENTION Titanium, zirconium, silicon,
The at least one element selected from the group consisting of aluminum (hereinafter sometimes referred to as “component (A)”) may be any element as long as it generally contains the above element, but is preferably Is an oxide of each element, a composite oxide, for example, titania, zirconia, silica, alumina, titania-zirconia, titania-silica, silica-zirconia, titania-silica-zirconia, alumina-silica, various zeolites, and more preferably Is titania-silica. Note that a composite oxide of the alkali metal element or the alkaline earth metal element and the component (A) and an alkali salt or an alkaline earth salt of the component (A) may be formed.

As the titanium source, one or more compounds selected from inorganic titanium compounds such as titanium chloride and titanium sulfate, and organic titanium compounds such as titanium oxalate and tetraisopropyl titanate, etc., and as the zirconium source, Zirconium nitrate, zirconia sol and the like can be used. As the silicon source, one or more compounds selected from colloidal silica, fine-particle silicic acid, water glass, inorganic silicon compounds such as silicon tetrachloride, and organic silicon compounds such as tetraethylsilicate can be used. Further, as the aluminum source, aluminum nitrate, aluminum sulfate, alumina sol and the like can be used.

Alkali metal element (hereinafter referred to as “component (B)”
) Is preferably lithium, sodium, potassium, rubidium, or cesium.
As the alkali metal element source, hydroxide, carbonate, bicarbonate and the like can be appropriately selected and used, for example,
Sodium is sodium hydroxide, sodium carbonate, sodium bicarbonate and the like, and potassium is potassium hydroxide, potassium carbonate and potassium bicarbonate.

At least one element selected from the group consisting of manganese, copper, nickel, iron, chromium, and lead (hereinafter, referred to as
The “component (C)” may be any of those containing the above-mentioned elements, but is preferably an oxide or a composite oxide of each element, and is preferably an alkali metal. A complex oxide or a double salt of the element or the alkaline earth metal element and the component C may be formed, and the raw material of the component “C” may be a hydroxide, a carbonate, a nitrate,
Sulfates, chlorides, oxides, organic metal salts, and the like can be used as appropriate.

The alkaline earth metal element (hereinafter sometimes referred to as “component (D)”) is preferably beryllium, magnesium, calcium, strontium, or barium. Sources of alkaline earth metal elements are hydroxides, carbonates, sulfates, chlorides, oxides, organic metal salts, and the like.

The components in the adsorbent, the composition ratios of the components (A), (B), (C), and (D) are not particularly limited, but all of them are calculated as oxides in the total amount of adsorbent. Component (A) is 10 to 98.5% by weight, component (B) is 1 to 40
% By weight, component (C) 0.5 to 50% by weight, component (D)
Is preferably 0 to 50% by weight.

The method for preparing the adsorbent of the present invention is not particularly limited, and can be prepared by various methods. Hereinafter, a typical method for preparing the adsorbent composed of the components (A), (B) and (C) will be described, but the present invention is not limited thereto.

The compound of the titanium source and the silicon source is
An atomic percentage of titanium and silicon of 40 to 95 respectively
% And 5 to 60%, and titanium and silicon are converted to oxides in an acidic aqueous solution state or sol state to a concentration of 1 to 100 g / L (liter, the same applies hereinafter) and kept at 10 to 100 ° C. Ammonia water was added dropwise thereto as a neutralizing agent under stirring to produce a coprecipitated compound containing titanium and silicon.
And dried at 450-700 ° C for 1-10 hours.
By baking for 10 to 10 hours, TiO ₂ —SiO ₂ is obtained.

TiO ₂ —ZrO ₂ can be obtained by using zirconium instead of silicon.

An aqueous solution of the starting materials of components (B) and (C),
Or adding the powder to the component (A) together with a molding aid,
Mixing, kneading, and molding with an extrusion molding machine. The obtained molded product was dried at 50 to 120 ° C., and then dried at 200 to 600 ° C.
C., preferably at 250 to 500.degree. C., for 1 to 10 hours, preferably 2 to 6 hours, to obtain the adsorbent of the present invention. In addition, a molded body containing the components (A) and (C) is prepared in advance, and the molded body contains the component (B).
After impregnated and dried at 50 to 120 ° C.,
By calcining at 600 ° C., the adsorbent of the present invention is obtained.

Preferred physical properties of the adsorbent of the present invention include:
A specific surface area (BET surface area) of 10 m ² / g or more;
The total pore volume is 0.15 cc / g or more, preferably 0.3
cc / g or more. Further, of the pores, 0.05 to 4
The pore volume having a pore size in the range of μm is 1% of the total pore volume.
0% or more, preferably 15% or more. More preferably, the adsorbent preferably has a group of pores having a pore size in the range of 0.01 to 0.03 μm and a group of pores having a pore size in the range of 0.05 to 4 μm. ~ 0.0
The pore volume occupied by the pore group having a pore size in the range of 3 μm is 50 to 80% of the total pore volume, and the pore volume having the pore size in the range of 0.05 to 4 μm is 10% of the total pore volume. %, Preferably 15% or more. The pore size, pore size distribution and pore volume in the present invention were measured using a mercury intrusion porosimeter. The mechanism by which the adsorbent having such properties is excellent in the adsorption performance of nitrogen oxides and the like is not clear, but the gas easily diffuses into the pores, and as a result, the adsorption performance of the nitrogen oxides and the like is reduced. It is thought to improve.

In particular, in order to obtain an adsorbent having the above-mentioned physical properties, it is necessary to prepare (1) a resin which volatilizes and decomposes in a firing step during molding, an organic polymer such as cellulose, and an ammonium nitrate or the like when preparing the adsorbent. A method of adding and mixing inorganic salts, (2) a method of adding and mixing powders such as silica sand, α-alumina, cordierite, zircon, and the like, and (3) a method of appropriately adjusting the particle diameter of the raw material powder. Can be manufactured.

Representative examples of the organic polymer which can be used in the above method (1) include polyethylene resin, acrylic resin, acetal resin, crystalline cellulose and the like. Typical examples of the inorganic salts include ammonium nitrate, ammonium oxalate, and ammonium carbonate. The amount of these additives is preferably in the range of 5 to 30% by weight. In the method (2), the average particle diameter and the amount of the powder added are 1 to 20 respectively.
μm and a range of 5-30% are preferred. In the case of the method (3), the average particle diameter of the raw material powder is usually 2 to 30 μm. If the particle diameter is too small, it is not possible to prepare an adsorbent having a target pore distribution.

The shape of the adsorbent of the present invention is not particularly limited, but may be appropriately selected from a column, a cylinder, a sphere, a plate, a honeycomb, and other integrally formed ones. For forming the adsorbent, a general molding method can be used, for example, a tableting method, an extrusion method, or the like can be used. In the case of a sphere, the average particle size is usually 1 to
10 mm. In the case of a honeycomb-shaped adsorbent, it is the same as a so-called monolithic carrier, and is manufactured by an extrusion method, a method of winding a sheet-shaped element, or the like. The shape of the gas passage (cell shape) may be any of a hexagon, a quadrangle, a triangle, and a corrugation. The cell density (number of cells / unit cross-sectional area) is usually 25 to 800 cells /
Square inches, preferably 25-500 cells / square inch.

According to the method for removing nitrogen oxides of the present invention,
Exhaust gas is brought into contact with the adsorbent to adsorb and remove nitrogen oxides and the like in the exhaust gas. The exhaust gas referred to here is nitrogen oxide (nitrogen monoxide and / or nitrogen dioxide) and / or sulfur oxide (sulfur dioxide and / or sulfur trioxide).
Means a ventilation gas or an atmospheric gas from the above-mentioned road tunnel or the like, and the method of the present invention is particularly applicable to nitrogen oxides, particularly nitrogen dioxide, from exhaust gas having a low concentration of 5 ppm or less. It is suitably used for the adsorption removal of.

The method of contacting the adsorbent of the present invention with the exhaust gas is not particularly limited, and is usually carried out by introducing the exhaust gas into a layer comprising the adsorbent. Since the treatment conditions vary depending on the properties of the exhaust gas and the like, they cannot be specified unconditionally. However, the temperature of the supplied exhaust gas is usually 0 to 100 ° C., and particularly preferably in the range of 0 to 50 ° C. Also,
The space velocity (SV) of the supplied exhaust gas is usually 500 to
50,000 hr ^-1 (STP), 2000 to 300
A range of 00 hr ^-1 (STP) is preferred.

Further, the adsorbent of the present invention is brought into contact with a gas containing nitrogen oxides and / or sulfur oxides to adsorb the nitrogen oxides and / or sulfur oxides, and by heating the adsorbent. By repeating the process of desorbing the adsorbed nitrogen oxides and detoxifying it,
It can be used for a long time. The usable period varies depending on the amount of the adsorbent, the use conditions, the composition of the processing gas and its concentration, and the like.

The method of heating and regenerating the adsorbent having adsorbed nitrogen oxides and the like is not particularly limited.
６００600 ° C., more preferably 300-40 ° C.
0 ° C.

It is preferable to flow a gas at the time of heating. Examples of the gas used include an inert gas such as air, nitrogen, carbon dioxide, and helium, and may contain water vapor. Preferably it is air. The gas amount used at that time may be equal to or less than the gas amount at the time of adsorption,
Preferably, it is 1/5 to 1/100 of the gas amount at the time of adsorption. The smaller the gas amount, the smaller the amount of heat required for heating and the more economical.

The heating time may be 10 minutes to 5 hours, preferably 30 minutes to 1 hour.

When the adsorbent is heated, the gas containing nitrogen oxides desorbed is converted into nitrogen by a conventional denitration method, that is, by adding NH ₃ as a reducing agent and using a denitration catalyst to convert nitrogen oxides into nitrogen. It can be reduced to water and made harmless.

[0036]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 Preparation of Component A As a titanium source, an aqueous sulfuric acid solution of titanyl sulfate having the following composition was used.

TiOSO ₄ : 250 g / L (as TiO ₂ ) Total H ₂ SO ₄ : 1,100 g / L Separately, ammonia water (NH ₃ , 25%) 2 was added to 400 L of water.
86L was added, and Snowtex NCS-30 was added thereto.
24 kg (silica sol, Nissan Chemical Co., Ltd., containing about 30% by weight of SiO ₂ ) was added. To the obtained solution, 153 L of a sulfuric acid aqueous solution of titanyl sulfate was added to 300 L of water and diluted, and a titanium-containing sulfuric acid aqueous solution was gradually added dropwise with stirring,
A co-precipitated gel was produced. Leave it for 15 hours and
It was obtained iO ₂ -SiO ₂ gel. The gel was filtered, washed with water, and dried at 200 ° C. for 10 hours. Then 600 ° C
For 6 hours in an air atmosphere, further pulverized using a hammer mill, and classified using a classifier to obtain a powder having an average particle diameter of 10 μm. The composition of the obtained powder (hereinafter referred to as “TS-1”) is Ti: Si = 4: 1 (atomic ratio), and the BET
The surface area was 160 m ² / g.

[Preparation of adsorbent] Sodium hydroxide 129
g of manganese carbonate was dissolved in 100 g of water.
In addition to 8.2 g and the above-mentioned TS-1 750 g, a suitable amount of water was added thereto with a kneader, mixed well and kneaded, and then extruded into a pellet having a diameter of 5 mmφ and a length of 5 mmL. Next, after drying at 100 ° C. for 10 hours, 5
Calcination was performed in air at 00 ° C. for 3 hours. The composition of the adsorbent thus obtained was TS-1: Na ₂ O: MnO ₂ = 7.
5: 10: 15% by weight.

The specific surface area is 100 m ² / g,
The total pore volume was 0.40 cc / g. The pore size distribution of the obtained adsorbent was measured by a mercury intrusion porosimeter (manufactured by Shimadzu Corporation).

Examples 2 to 7 Adsorbents were prepared in the same manner as in Example 1 except that manganese carbonate was changed to copper carbonate, nickel carbonate, cobalt carbonate, iron hydroxide, chromium hydroxide, and lead carbonate. Table 1 shows the composition, specific surface area, and total pore volume. .

Examples 8 to 13 In Example 1, titanium oxide (b) was used in place of TS-1.
Anatase Type Titanium Oxide DT-5 manufactured by Nupoulin
0), zirconium oxide (Zirconium oxide EP manufactured by Daiichi Kagaku Kagaku Co., Ltd.), aluminum oxide (γ-alumina A-11 manufactured by Sumitomo Chemical Co., Ltd.), silicon oxide (manufactured by Mizusawa Chemical
AMT-silica), alumina-silica (Catalyst Chemical Co., Ltd.)
Example 1 except that alumina-silica LA) and zeolite (mordenite TSZ-600 manufactured by Tosoh Corporation) were used.
Similarly, an adsorbent was prepared. Each composition, specific surface area,
The total pore volume is shown in Table 1.

Example 14 129 g of sodium hydroxide was dissolved in 100 g of water. 198.2 g of manganese carbonate used in
And 650 g of TS-1 and further 100 g of barium carbonate, and after mixing and kneading well while adding an appropriate amount of water with a kneader, using an extruder, a diameter of 5 mmφ and a length of 5 mm.
L was pelletized. Next, after drying at 100 ° C. for 10 hours, it was baked at 500 ° C. for 3 hours in air. The composition of the adsorbent thus obtained is TS-1: Na
₂ O: MnO ₂ : BaCO ₃ = 65: 10: 15: 10
% By weight. The specific surface area was 68 m ² / g, and the total pore volume was 0.35 cc / g.

Example 15 A solution prepared by dissolving 119 g of potassium hydroxide in 100 g of water was mixed with 198.2 g of manganese carbonate used in Example 1 and TS.
-1 In addition to 750 g, well mixed and kneaded while adding an appropriate amount of water with a kneader, and then, with an extruder, a diameter of 5 mm
It was formed into a pellet having a diameter of 5 mmL. Then 1
After drying at 00 ° C. for 10 hours, it was calcined at 500 ° C. for 3 hours in air. The composition of the adsorbent thus obtained is:
_{TS-1: K 2 O:} MnO 2 = 75: 10: 15 wt%
Met.

The specific surface area is 100 m ² / g,
The total pore volume was 0.41 cc / g. In addition, the pore volume of the obtained adsorbent was measured by a mercury intrusion porosimeter (manufactured by Shimadzu Corporation).

Comparative Example 1 A solution prepared by dissolving 129 g of sodium hydroxide in 100 g of water was added to 850 g of titanium oxide used in Example 8, and the mixture was kneaded well while adding an appropriate amount of water using a kneader.
It was formed into a pellet having a diameter of 5 mmφ and a length of 5 mmL by an extruder. Next, after drying at 100 ° C. for 10 hours, it was baked at 350 ° C. for 3 hours in air. The composition of the adsorbent thus obtained was TiO ₂ : Na ₂ O = 90:
It was 10% by weight. The specific surface area was 81 m ² / g, and the total pore volume was 0.38 cc / g.

Example 16 The adsorbents obtained in Examples 1 to 15 and Comparative Example 1 were
The nitrogen oxide adsorption capacity was evaluated by the following method.

(Evaluation Method) Performance Evaluation Conditions 46 ml of the adsorbent was filled in a glass reaction tube having an inner diameter of 30 mm. A synthesis gas having the following composition was introduced into this adsorbent layer under the following conditions.

Synthesis gas composition : Nitric oxide (NO): 1 ppm, nitrogen dioxide (N
O ₂ ): 0.1 ppm, sulfur dioxide (SO ₂ ): 0.05
ppm, H ₂ O: 2.5% by volume, remaining: air measurement conditions Gas amount: 15.2 NL / min, processing temperature: 25 ° C., space velocity (SV): 20000 hr ⁻¹ (STP), gas humidity: 85% RH The concentration of nitrogen oxides (NO and NO ₂ ) in the synthesis gas at the inlet and outlet of the adsorbent layer was determined by chemiluminescence NOx.
And the sulfur oxide concentration was measured with an ultraviolet fluorescent SO ₂ meter, and the NO, NO ₂ and SO ₂ removal rates were calculated according to the following equation.

NO removal rate (%) = [(inlet NO concentration-outlet NO concentration) / (inlet NO concentration)] × 100 NO ₂ removal rate (%) = [(inlet NO ₂ concentration−outlet NO ₂ concentration) / (Inlet NO ₂ concentration)] × 100 SOx removal rate (%) = [(inlet SOx concentration−outlet SOx
Concentration) / (Inlet SOx concentration)] × 100 The results of the evaluation test are shown in Table 1.

Accelerated Endurance Test An accelerated endurance test was performed by changing the synthesis gas composition under the performance evaluation conditions described below.

Accelerated endurance synthesis gas composition Nitric oxide (NO): 10 ppm, nitrogen dioxide (N
O ₂ ): 1 ppm, sulfur dioxide (SO ₂ ): 0.5 pp
m, H ₂ O: 2.5% by volume, remaining: air After the accelerated durability test was performed for 300 hours, the gas composition was changed to the above-described performance evaluation conditions, and nitrogen oxides and sulfur oxides after the accelerated durability test were changed. Adsorption performance (NO removal rate, NO ₂
(Removal rate and SOx removal rate) were evaluated. Table 1 shows the evaluation test results.

Regeneration Test A regeneration test was performed on the adsorbent subjected to the accelerated endurance test while changing the synthesis gas composition and measurement conditions in the performance evaluation test to the following conditions.

Regeneration test conditions H ₂ O: 5% by volume, remaining: air treatment conditions Gas volume: 1.0 NL / min, heating rate: 350 ° C./H
r, treatment temperature: 350 ° C., treatment time 30 minutes After performing the above regeneration test and sufficiently cooling to room temperature, the synthesis gas under the performance evaluation conditions was again introduced into the adsorbent,
After the regeneration test, the adsorption performance of the adsorbent for nitrogen oxides and sulfur oxides (NO removal rate, NO ₂ removal rate, and SOx removal rate) was evaluated. Table 1 shows the evaluation test results.

From the results shown in Table 1, it is understood that the adsorbent of the present invention has excellent adsorption activity.

[0056]

According to the adsorbent of the present invention, the adsorbing ability of the adsorbent for nitrogen oxides and / or sulfur oxides exhibits a high adsorbing performance by having a specific composition, and has good durability. The adsorbent having the composition of the present invention can be heated and regenerated, and does not require complicated reprocessing such as water washing. Therefore,
The adsorbent of the present invention can efficiently and inexpensively remove low-concentration nitrogen oxides and the like in exhaust gas.

[0057]

[Table 1]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B01D 53/60 B01D 53/34 123A 53/74 129A 53/81 132Z B01J 20/08 20/10 Examiner Shigehiro Toyonaga (56) Reference Patent Document JP-A-4-367707 (JP, A) JP-A-5-123571 (JP, A) JP-A-6-121925 (JP, A) JP-A-7-204468 (JP, A) JP-A-51-1 35686 (JP, A) JP-A-64-11637 (JP, A) JP-A-8-224439 (JP, A) JP-A-5-192535 (JP, A) JP-A-5-200283 (JP, A) JP-B-48-20102 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01J 20/00-20/34 B01D 53/34

Claims (4)

(57) [Claims] At least one element selected from the group consisting of titanium, zirconium, silicon and aluminum, at least one alkali metal element, manganese,
Copper, contains nickel, cobalt, iron, chromium, and at least one element selected from the group consisting of lead, moreover ratio
Surface area is 10m ² / g or more, total pore volume is 0.15cc
/ G or more and having a pore size in the range of 0.05 to 4 μm
An adsorbent for nitrogen oxides and / or sulfur oxides, wherein the pore volume is 10% or more of the total pore volume . 2. The adsorbent according to claim 1, further comprising an alkaline earth metal element. 3., characterized in that the removal of claim 1 or a nitrogen oxide adsorbent according to 2 and / or sulfur oxides by contacting the gas containing nitrogen oxides and / or sulfur oxides How to use the adsorbent. 4. A step of bringing the adsorbent according to claim 1 into contact with a gas containing nitrogen oxides and / or sulfur oxides to adsorb the nitrogen oxides and / or sulfur oxides, and heating the adsorbent. A method of using an adsorbent, comprising repeating a step of desorbing and adsorbing nitrogen oxides that have been adsorbed and detoxifying.