JP2002320847A - Adsorbent for nitrogen oxide and/or sulfur oxide and method for removing nitrogen oxide and/or sulfur oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adsorbent for nitrogen oxides and/or sulfur oxides and to provide a method for removing nitrogen oxides and/or sulfur oxides by using the adsorbent. SOLUTION: The adsorbent for nitrogen oxides and/or sulfur oxides is prepared by using an adsorbent precursor containing double oxides of iron and copper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an adsorbent for nitrogen oxides and / or sulfur oxides and a method for removing nitrogen oxides and / or sulfur oxides using the adsorbent.

[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.

On the other hand, it is included in ventilation gas or air in road tunnels, roads with shelters, deep underground spaces, road intersections, underground parking lots, etc., and gas discharged from combustion equipment used in homes. The concentration of nitrogen oxides is about 5 ppm, which is significantly lower than the concentration of nitrogen oxides in boiler exhaust gas, and the gas temperature is room temperature, and the amount of gas is enormous. For this reason, in order to efficiently remove nitrogen oxides by applying the above-described catalytic reduction method to the ventilation gas of a road tunnel, for example, the temperature of the ventilation gas needs to be 300 ° C. or higher, 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.

[0004] Under such circumstances, it is desired to efficiently remove nitrogen oxides from exhaust gas having a low nitrogen oxide concentration, for example, 5 ppm or less, such as ventilation gas for road tunnels as described above. Therefore, a method of adsorbing and removing a low concentration of nitrogen oxides by an adsorbent and an adsorbent suitable for the method have been proposed.

[0005] The present applicant has proposed an adsorbent suitable for adsorbing and removing nitrogen oxides from such a low-concentration nitrogen oxide-containing gas (JP-A-10-128105, JP-A-10-192696). JP-A-10-309435, JP-A-11-28351, JP-A-11-28352, JP-A-2000-51655, JP-A-2000-325780,
JP-A-2000-225318, Japanese Patent Application No. 2000-0606
51 and Japanese Patent Application No. 2001-071638). In addition, as a method for efficiently removing nitrogen oxides from a gas containing sulfur oxides in addition to nitrogen oxides, the present applicant removes sulfur oxides in advance and then contacts the nitrogen oxide adsorbent. A method of adsorbing and removing nitrogen oxides has been proposed (JP-A-10-76136). Furthermore, the present applicant has developed a method of heating and regenerating an adsorbent whose performance has been reduced by use in the presence of a reducing agent, and performing a heat treatment in the presence of the reducing agent, washing with water, and then impregnating with an alkali metal element. Also, a method of playing back the video data has been proposed (JP-A-2000-2253).
17 and Japanese Patent Application No. 2000-029195).

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a low concentration nitrogen oxide and / or sulfur oxide suitable for adsorbing and removing nitrogen oxides and / or sulfur oxides, in particular, having a low concentration of about 5 ppm or less. An object of the present invention is to provide an adsorbent suitable for adsorption removal and a method for removing nitrogen oxides and / or sulfur oxides using the adsorbent.

[0007]

As a technique effective in solving the above-mentioned problems, the present applicant has proposed an adsorbent containing zero-valent or monovalent copper and an alkali metal element, and an adsorbent containing divalent iron. And methods for removing nitrogen oxides and the like using these adsorbents (Japanese Patent Application Nos. 2000-060651 and 200)
1-071638), but as a result of further intensive studies, the present inventors have found that the following adsorbents are more effective in solving the above-mentioned problems, and based on this finding, have carried out this study. It was completed.

That is, the present invention is a nitrogen oxide and / or sulfur oxide adsorbent characterized by using an adsorbent precursor containing a composite oxide of iron and copper.

In the present invention, the adsorbent may further comprise an alkali metal element, titanium, silicon, aluminum, zirconium, an alkaline earth metal element, platinum, gold, ruthenium,
A nitrogen oxide and / or sulfur oxide adsorbent characterized by containing at least one element selected from rhodium, palladium, manganese, nickel, cobalt, zinc, vanadium, niobium, chromium, molybdenum and tungsten. is there.

[0010] Further, the present invention provides a nitrogen oxide and / or sulfur oxide which is characterized by contacting a gas containing nitrogen oxide and / or sulfur oxide with the adsorbent to remove nitrogen oxide and / or sulfur oxide. And / or a method for removing sulfur oxides.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The adsorbent of the present invention is for adsorbing a low concentration of nitrogen oxides and / or sulfur oxides of 5 ppm or less. The nitrogen oxides are those indicated as NOx, in particular it can be mentioned NO and NO _2. Also, the sulfur oxides are those represented by SOx, can be specifically exemplified SO _2. The adsorbent of the present invention can treat nitrogen oxides and sulfur oxides simultaneously or individually, but is particularly excellent in adsorbing and removing NO ₂ .

[0012] The adsorbent of the present invention is a nitrogen oxide and / or sulfur oxide adsorbent characterized by using an adsorbent precursor containing a composite oxide of iron and copper.

[0013] Here, the Fe-Cu composite oxide is not a simple mixture of iron and copper oxides, but another type of oxide in which a bond between both metals is formed via an oxygen atom. Fe
The method for preparing the -Cu composite oxide is not particularly limited, but typically can be prepared by the following coprecipitation method. That is, an alkaline solution is added to an aqueous solution in which iron and copper salts are dissolved, an aqueous solution in which iron and copper salts are dissolved in an alkaline solution, or an aqueous solution in which iron and copper salts are dissolved in water is mixed with an alkaline solution. Add the solution at the same time,
A precipitate in which hydroxides and / or carbonates of iron and copper are mixed on a molecular scale is formed, and calcined at 200 ° C. or higher, preferably 300 ° C. or higher, such as in air or an inert gas such as nitrogen. Alternatively, by adding an oxidizing agent in the liquid phase and subjecting it to a liquid phase oxidation treatment, Fe-C
The u composite oxide is obtained. At this time, the iron and copper salts used in the aqueous solution may be in any form as long as they are water-soluble. For example, sulfates, nitrates, halides, acetates and the like can be used.

The Fe—C contained in the adsorbent precursor of the present invention
The u composite oxide may have any structure as long as iron and copper are mixed on a molecular scale and a bond between both metals is formed via an oxygen atom. That is, as long as it is prepared by the above-mentioned coprecipitation method, its structure may be amorphous (amorphous) or may have a specific crystal structure. As an adsorbent precursor.

As the Fe-Cu composite oxide, those having a structure of CuFe ₂ O ₄ are particularly preferably used.
The fact that the adsorbent precursor of the present invention contains CuFe ₂ O ₄ can be confirmed by measuring the lattice spacing (d value) by X-ray diffraction. The d values of CuFe ₂ O ₄ are 2.50 ± 0.01, 2.58 ± 0.01 and 1.4.
9 ± 0.01 and 2.99 ± 0.01.

The adsorbent of the present invention can be prepared by various methods, and the preparation method is not particularly limited. Preferably, an adsorbent precursor containing an Fe—Cu composite oxide is prepared in advance, The adsorbent precursor is heat-treated in a reducing atmosphere to convert all or a part of the Fe—Cu composite oxide with FeO and / or Fe ₃ O ₄ and Cu and / or Cu.
Alternatively, it is used after being converted to Cu ₂ O.

The adsorbent of the present invention, as compared to the adsorbent obtained from a precursor containing a simple mixture of the oxides of iron and copper, in particular exhibit excellent adsorption performance for NO _2.
This is considered to be based on the following reasons. That is,
In the Fe—Cu composite oxide, since iron and copper are in a state of being mixed on a molecular scale via an oxygen atom, FeO produced using this Fe—Cu composite oxide as a starting material
And / or Fe ₃ O ₄ and Cu and / or Cu ₂
O and has a very high dispersion state, therefore a simple mixture of the oxides of iron and copper as compared with the case where the starting material, more the number of particularly effective adsorption active sites for the adsorption of NO ₂ It is considered that the amount increases and excellent adsorption performance is exhibited. The present invention is not limited by such theoretical considerations.

In the adsorbent of the present invention, the total amount of the iron component (hereinafter also referred to as (A)) is FeO and / or F
It does not need to be e ₃ O ₄ , and it is not necessary that the total amount of the copper component (hereinafter also referred to as (B)) be Cu and / or Cu ₂ O. That is, it is sufficient that contains FeO and / or _Fe 3 _{O 4} and Cu and / or Cu ₂ O in an amount effective to the extent that the effect of the present invention is obtained.

[0019] The adsorbent of the present invention comprises FeO and / or F
The presence of e ₃ O ₄ can be confirmed by measuring the lattice spacing (d value) by X-ray diffraction. The d values of FeO are 2.15 ± 0.01 and 2.49 ±
The d values of Fe ₃ O ₄ are 2.53 ± 0.01, 1.48 ± 0.01 and 2.
97 ± 0.01. Similarly, the fact that the adsorbent of the present invention contains Cu and / or Cu ₂ O indicates that X
It can be confirmed by measuring the lattice spacing (d value) of the line diffraction. The d value of Cu is 2.09 ± 0.01
And 1.81 ± 0.01 and 1.28 ± 0.01,
The d values of Cu ₂ O are 2.47 ± 0.01 and 2.14 ± 0.
01 and 1.51 ± 0.01.

The method for preparing the adsorbent of the present invention is not particularly limited, and it can be prepared by various methods. Above all, as described below, an adsorbent precursor containing an Fe—Cu composite oxide is prepared in advance, and this precursor is heat-treated in a reducing atmosphere to convert at least a part of the iron component to FeO and / or An adsorbent in which Fe ₃ O ₄ is used and at least a part of the copper component is Cu and / or Cu ₂ O is preferable. The starting materials for component (A) and component (B) are both Fe-Cu composite oxides.

When the adsorbent further contains an alkali metal element (hereinafter also referred to as (C)), the performance of removing nitrogen oxides and / or sulfur oxides over time is small, and the adsorbent has excellent durability. It has properties and is particularly preferably used. The alkali metal element may be mixed with the starting material of the adsorbent precursor, or may be included in the adsorbent precursor after preparing the adsorbent precursor, or the adsorbent precursor may be subjected to a heat treatment in a reducing atmosphere. It can also be included after doing so. Preferably, the adsorbent precursor is prepared and then used after being included in the adsorbent precursor.

The form of the alkali metal element of the component (C) is not particularly limited, and may be any form as long as it can adsorb nitrogen oxides and / or sulfur oxides as an adsorbent. For example, it is contained in the form of a hydroxide, carbonate or bicarbonate. Starting materials for component (C) include hydroxides, carbonates, bicarbonates,
In addition to nitrates and nitrites, organic acid salts such as acetate, oxalate, citrate and sorbate can be used.

The adsorbent may further contain at least one element selected from the group consisting of titanium, silicon, aluminum, zirconium and alkaline earth metal elements (hereinafter also referred to as component (D)). At least one element selected from the group consisting of titanium, silicon, aluminum, zirconium and an alkaline earth metal element is mixed with the starting material of the adsorbent precursor, or prepared after preparing the adsorbent precursor. The adsorbent precursor may be included in the body, or may be included after the adsorbent precursor is subjected to a heat treatment in a reducing atmosphere. Preferably, it is used by mixing with the starting material of the adsorbent precursor.

The form of the component (D) is not particularly limited, and may be in any form as long as the function of adsorbing nitrogen oxides and / or sulfur oxides is obtained. For example, oxides, composite oxides, hydroxides, carbonates, phosphates,
It is contained as sulfates. Among the components (D),
Zirconium and alkaline earth metals are preferably used in that an adsorbent having excellent durability can be obtained. As the starting materials, oxides, hydroxides, carbonates, sulfates, halides, phosphates and the like of each element can be used.

The adsorbent further comprises at least one selected from the group consisting of platinum, gold, ruthenium, rhodium, palladium, manganese, nickel, cobalt, zinc, vanadium, niobium, chromium, molybdenum and tungsten as component (E). It can contain an element, preferably at least one element selected from platinum, gold, ruthenium, rhodium, palladium and cobalt.

Hereinafter, the adsorbent according to the present invention will be described in detail. However, it is not limited to the specific adsorbent as long as it is a component according to the present invention. can do. The adsorbent of the present invention is not particularly limited as long as the adsorbent precursor contains an Fe—Cu composite oxide, but the following can be mentioned as typical examples. In addition, about a ratio, components (A), (B),
(C) and (D) are oxide equivalents, and specifically,
For example, iron is converted to Fe ₂ O ₃ , potassium is converted to K ₂ O, and calcium is converted to CaO.

<Adsorbent 1> An adsorbent containing (A) iron and (B) copper.

Regarding the ratio of each component, component (A) is 1
The content of the component (B) is 1 to 99% by mass, preferably 5 to 95% by mass (total 100% by mass, the same applies hereinafter).

<Adsorbent 2> (A) iron, (B) copper, and (C) an alkali metal element (Li, Na, K, Rb, C
adsorbent containing s).

Regarding the ratio of each component, component (A) is 1
The component (B) is 1 to 98% by mass, preferably 1 to 94% by mass, and the component (C) is 1 to 30% by mass, preferably 1 to 98% by mass. ~ 2
0% by mass.

<Adsorbent 3> (A) iron, (B) copper, and (D) titanium, silicon, aluminum, zirconium and alkaline earth metal elements (Be, Mg, Ca, Sr,
An adsorbent containing at least one element selected from Ba).

Regarding the ratio of each component, component (A) is 1
The component (B) is 1 to 89% by mass, preferably 1 to 81% by mass, and the component (D) is 10 to 98% by mass, preferably 14 to 89% by mass.
９４94% by mass.

<Adsorbent 4> (A) iron, (B) copper, (C)
An adsorbent containing an alkali metal element and (D) at least one element selected from titanium, silicon, aluminum, zirconium and alkaline earth metal elements.

Regarding the ratio of each component, component (A) is 1
The component (B) is 1 to 89% by mass, preferably 1 to 81% by mass, and the component (C) is 1 to 30% by mass, preferably 1 to 89% by mass. ~ 2
0% by mass, and component (D) is 9 to 97% by mass, preferably 13 to 93% by mass.

Of the above adsorbents, adsorbent 4 is preferred. Specifically, component (A), component (B), component (C)
And an adsorbent containing component (D).

The adsorbent further contains the component (E)
As platinum, gold, ruthenium, rhodium, palladium,
Contains at least one element selected from manganese, nickel, cobalt, zinc, vanadium, niobium, chromium, molybdenum and tungsten, preferably at least one element selected from platinum, gold, ruthenium, rhodium, palladium and cobalt be able to. Platinum, gold, ruthenium, rhodium, palladium, manganese, nickel, cobalt, zinc, vanadium, niobium,
At least one element selected from chromium, molybdenum, and tungsten is mixed with the starting material of the adsorbent precursor, or is included in the adsorbent precursor after preparing the adsorbent precursor, or The adsorbent precursor may be included after heat treatment in a reducing atmosphere. Preferably, it is used by being mixed with the starting material of the adsorbent precursor, or after preparing the adsorbent precursor and including it in the adsorbent precursor.

The ratio of the component (E) is 0.01 to 10% by mass in terms of a metal in the case of platinum, gold, ruthenium, rhodium and palladium in the adsorbents 1 to 4 with respect to the total amount of each component. Preferably 0.05 to 5% by mass
Can be added. In the case of manganese, nickel, cobalt, zinc, vanadium, niobium, chromium, molybdenum and tungsten, 0.5 to 3 as oxides
0 mass%, preferably 1 to 20 mass% can be added. The form of the component (E) is contained, for example, as a metal, an oxide, a composite oxide, or the like. Among the components (E), preferably, platinum, gold, ruthenium, rhodium, palladium and cobalt are more preferably
Ruthenium and cobalt are used. As starting materials for the component (E), oxides, hydroxides, nitrates, sulfates, halides, organic metal salts, organic acid salts such as acetates and oxalates, ammonium complexes and the like of each element are used. Can be.

As described above, the adsorbent of the present invention can be prepared by various methods, and may be any one using an adsorbent precursor containing an Fe—Cu composite oxide. Alternatively, this adsorbent precursor is heat-treated in a reducing atmosphere to convert all or a part of the Fe—Cu composite oxide to FeO and / or Fe ₃ O ₄ and Cu and / or Cu.
Alternatively, an adsorbent converted to Cu ₂ O is preferable.

The “adsorbent precursor” includes an Fe—Cu composite oxide and has, for example, the composition of the adsorbents 1 to 4,
Any treatment can be used as long as it can be used as the adsorbent according to the present invention, but it is preferable that the Fe—Cu composite oxide be contained in the form of CuFe ₂ O ₄ .

The adsorbent precursor can be prepared by a method generally used for preparing this kind of adsorbent. A typical preparation method of the adsorbent precursor containing the components (A), (B), (C) and (D) will be described below, but the present invention is not limited thereto. Not something.

Component (A), component (B) and component (D)
The powder or aqueous solution of the starting material is added to the component (D) together with a commonly used molding aid, and mixed and stirred.
It is molded by an extruder (the starting materials for components (A) and (B) are both Fe-Cu composite oxides). After drying the obtained molded body at 50 to 120 ° C, 200 to 600 ° C,
The calcination is carried out preferably at 250 to 500 ° C. for 1 to 10 hours, preferably 2 to 6 hours, in air, in an inert gas such as nitrogen, or the like. Note that the last baking step is not essential and can be omitted as appropriate.

In addition, a molded article containing at least one of the components (A) to (C) and the component (D) may be prepared in advance, and the molded article may be impregnated with the remaining components. For example, after a molded body composed of the components (A), (B) and (D) is prepared as described above, the component (C) is impregnated and supported.

The preferred adsorbent of the present invention can be obtained by subjecting the above adsorbent precursor to heat treatment in a reducing atmosphere.
Heat treatment in a reducing atmosphere refers to a method in which a reducing agent is added to the atmosphere gas of the heat treatment and a heating treatment is performed in the presence of the reducing agent, and a substance having a reducing action is previously carried in an adsorbent precursor. Then, heat treatment is performed in an inert gas. In the present invention, when the alkali metal element is contained in the form of an organic acid salt in the adsorbent precursor containing an alkali metal element, the adsorbent precursor is heat-treated in an inert gas. Thus, a suitable adsorbent of the present invention can be obtained. Even when the alkali metal element is contained in the form of its organic acid salt, the preferred adsorbent of the present invention can be obtained by a method of adding a reducing agent to the atmosphere gas of the heat treatment.

Therefore, first, a method of adding a reducing agent to the atmosphere gas of the heat treatment and performing the heat treatment in the presence of the reducing agent will be described. The reducing agent means hydrogen and a combustible organic compound. Examples of the combustible organic compound include hydrocarbons, preferably saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms. In the present invention, hydrogen or hydrocarbons, particularly hydrogen, is suitably used as the reducing agent. Representative examples of the hydrocarbons include saturated or unsaturated hydrocarbons such as methane, ethane, propane, butane, ethylene, propylene, and butadiene.

The reducing agent is usually diluted with another gas and used as a mixed gas with an inert gas such as nitrogen. Specifically, when hydrogen is used as the reducing agent, it is used as a mixed gas of hydrogen and an inert gas such as nitrogen or helium. The concentration of hydrogen in the mixed gas is usually 0.1 to 20% by volume, preferably 0.5 to 1% by volume.
0% by volume. In general, it is preferable to use as a mixed gas with the above-mentioned inert gas in consideration of handling convenience. Even in the case of a combustible organic compound, it is used as a mixed gas with an inert gas such as nitrogen. The concentration of the combustible organic compound in the mixed gas is usually 0.001 to 1
%, Preferably 0.01 to 0.5% by volume.

Examples of the gas that can be used for diluting the reducing agent include the above-mentioned inert gas such as nitrogen and helium and air, as well as water vapor (H ₂ O) and carbon dioxide gas. Thus, typical examples of the mixed gas include a combination of hydrogen and an inert gas, and a combination of a combustible organic compound and an inert gas.

The heating temperature is usually from 200 to 600 ° C., preferably from 300 to 500 ° C., and more preferably from 30 to 500 ° C.
0-400 ° C. The adsorbent precursor is usually at room temperature, but the rate of temperature increase up to the heating temperature is not particularly limited and can be determined as appropriate. The heating time cannot be specified unconditionally, but can be appropriately selected usually in the range of 30 minutes to 10 hours, preferably 30 minutes to 5 hours.

The heat treatment of the present invention is preferably performed under ventilation of a reducing agent. In the case where the heat treatment is performed under ventilation of the reducing agent, the degree of ventilation is not particularly limited, and the condition may be such that a new reducing agent is supplied.

Next, a method of heating an adsorbent precursor containing an alkali metal element in the form of an organic acid salt in an inert gas in the case of containing an alkali metal element will be described. In addition, this adsorbent precursor is prepared by, for example, preparing a molded body composed of the component (A), the component (B) and the component (D) as described above, and then adding an alkali metal organic acid salt as the component (C). It is obtained by being impregnated and supported. Representative examples of the alkali metal organic acid salt include potassium acetate, tripotassium citrate, potassium sorbate and the like. Among them, potassium acetate is preferably used. Usually, nitrogen is used as the inert gas. The heating conditions are the same as in the case of the heat treatment in the presence of the reducing agent.

It is not clear why the heat treatment in the above-mentioned inert gas promotes the reduction.
_In the case of ₂ O _4, the alkali metal organic acid salt is thermally decomposed by the heat treatment, and the oxygen held by CuFe ₂ O ₄ is consumed during the thermal decomposition, and CuFe ₂ O ₄ (copper is divalent, iron is Trivalent) is Cu (zero-valent) and / or Cu ₂ O (1
Value) and FeO (2 valence) and / or _Fe 3 _O 4 (2 + III) is thought to be reduced to a. In addition,
The present invention is not limited by such theoretical considerations.

The shape of the adsorbent of the present invention is not particularly limited, and can be appropriately selected from a column, a cylinder, a sphere, a plate, a honeycomb, and other integrally molded products. For this molding, a general molding method, for example, tablet molding, extrusion molding or the like can be used. In the case of a spherical shape, 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 monolith carrier, and can be manufactured by an extrusion molding method, a method of winding a sheet-shaped element, or the like. The shape of the gas passage port (cell shape) may be any of a hexagon, a quadrangle, a triangle, or a corrugation. Cell density (number of cells /
The unit sectional area is usually 25 to 800 cells / square inch (× 2.54 cm), and preferably 25 to 500 cells / square inch (× 2.54 cm).

According to the method of the present invention, a gas containing nitrogen oxides and / or sulfur oxides is brought into contact with the adsorbent to adsorb the nitrogen oxides and / or sulfur oxides and purify the gas. A typical example of the above-mentioned gas is a ventilation gas or an atmospheric gas from the above-mentioned road tunnel or the like.
It is suitably used for removing nitrogen oxides and sulfur oxides from gases having a low concentration of pm or less.

The method for contacting the gas with the adsorbent is not particularly limited, and is usually carried out by introducing a gas into a layer made of the adsorbent. Since the treatment conditions differ depending on the properties of the gas to be treated and the like, they cannot be specified unconditionally, but for example, the temperature of the gas supplied to the adsorbent layer is usually
The temperature is 0 to 100 ° C, and particularly preferably 0 to 50 ° C. The space velocity (SV) of the gas supplied to the adsorbent layer
Is usually 1,000 to 100,000 hr ^-1 (ST
P) and 4,000-60,000 hr ^{- 1} (ST
The range of P) is preferred.

In purifying a gas by efficiently removing nitrogen oxides from a gas containing sulfur oxides in addition to nitrogen oxides, the sulfur oxides are removed in advance, and then contacted with the adsorbent of the present invention. By adsorbing and removing nitrogen oxides, the durability of the adsorbent is improved, and nitrogen oxides can be effectively removed over a long period of time.

The method for removing the sulfur oxide is not particularly limited, and a method of removing the gas by washing it with water, a method of bringing the gas into contact with an adsorbent for adsorbing the sulfur oxide, and the like can be used. Above all, a method using an adsorbent for sulfur oxides is preferably used from the viewpoint of a compact apparatus and low energy consumption.

As the sulfur oxide adsorbent, SOx
Any adsorbent may be used as long as it can adsorb, and among them, an adsorbent containing at least one selected from activated carbon, transition metals, alkali metals and alkaline earth metals is suitably used. Representative examples of transition metals include Ni, Co,
Examples include Fe, Mn, Cr, Mo, W, V, Nb, Zn, and Cu. Representative examples of alkali metals and alkaline earth metals include Li, Na, and K, respectively.
And Mg, Ca, Ba. There is no particular limitation on the form of these elements in the adsorbent.
Any form may be used as long as it can adsorb x. Specific examples include oxides, carbonates, sulfates, chlorides and hydroxides.

The adsorbent for sulfur oxide is used as a carrier
Alkaline earth metal, alumina, silica, titania, zirconia, silica-alumina, alumina-zirconia, silica-titania, silica-zirconia and titania-
At least one of zirconia may be included.

Thus, in a preferred embodiment of the present invention, a gas containing nitrogen oxides and sulfur oxides is first contacted with an adsorbent for sulfur oxides to adsorb and remove sulfur oxides, and then the adsorbent of the present invention To purify the gas by adsorbing and removing nitrogen oxides. Thereby, the durability of the adsorbent of the present invention is improved.

[0059]

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

Example 1 Ferric nitrate [Fe (NO ₃ )
₃ · _9H 2 O] _2,182g and copper nitrate [Cu _(NO 3)
_[2 / 3H ₂ O] 652 g was weighed and placed in a 30-liter polyethylene container, pure water was added thereto, and the mixture was stirred and dissolved to give a total of 15 liter of a precipitated mother liquor (solution A). On the other hand, 1,145 g of sodium carbonate (Na ₂ CO ₃ )
It was weighed and placed in a 0-liter polyethylene container, pure water was added thereto, and the mixture was stirred and dissolved to give a total amount of 7.5 liter of a precipitant solution (solution B). Next, while stirring the solution A, the solution B was gradually added thereto to obtain a coprecipitation of iron and copper. This coprecipitate was filtered, washed with water, dried at 100 ° C. for 15 hours, and then pulverized. Next, the mixture is fired at 400 ° C. for 5 hours in an air atmosphere, and the BET specific surface area is 112 m ² / g.
An e-Cu composite oxide powder was obtained. The composition of the obtained powder was Fe: Cu = 2: 1 (atomic ratio), and the structure was amorphous (amorphous) by X-ray diffraction. Hereinafter, the amorphous (amorphous) Fe-C obtained by this preparation method will be described.
The u composite oxide powder is described as Fe-Cu-A.

After adding an appropriate amount of water to 200 g of Fe-Cu-A and 400 g of calcium carbonate and mixing well with a kneader, the mixture was formed into a pellet having a diameter of 5 mm and a length of 5 mm by an extruder. The pellet was dried at 100 ° C. for 10 hours, and then calcined at 350 ° C. for 5 hours in an air atmosphere to obtain a pellet-shaped adsorbent precursor (1). The composition of the adsorbent precursor (1) is Fe: Cu: Ca (Fe ₂ O ₃ : Cu
O: CaO) = 31.4: 15.7: 52.9
(% By mass).

Next, the pellets were subjected to a heat treatment (reduction treatment with a reducing agent) at 400 ° C. for 3 hours in an atmosphere of hydrogen / nitrogen (5/95% by volume) to obtain an adsorbent (1).

Example 2 Sodium carbonate (Na ₂ CO 3)
₃ ) 1,145 g was weighed into a 30-liter polyethylene container, and pure water was added thereto, followed by stirring and dissolution to obtain a total of 15 liter of a precipitated mother liquor (solution A). On the other hand, the ferric nitrate _{[Fe (NO 3) 3 ·} 9H 2 O] 2,182g and copper nitrate _{[Cu (NO 3) 2 ·} 3H 2 O] 652g 10
It was weighed and placed in a 1-liter polyethylene container, and pure water was added thereto, followed by stirring and dissolution to obtain a total amount of 6-liter precipitant solution (solution B). Next, while stirring the solution A, the solution B was gradually added thereto to obtain a coprecipitation of iron and copper. This coprecipitate was filtered, washed with water, dried at 100 ° C. for 15 hours, and then pulverized. Then calcined for 5 hours under air atmosphere at 450 ° C., the BET specific surface area of ^33m 2 / g Fe-
A Cu composite oxide powder was obtained. The composition of the obtained powder is F
e: Cu = 2: 1 (atomic ratio), and the structure was CuFe ₂ O ₄ by X-ray diffraction. Hereinafter, Fe- having a structure of CuFe ₂ O ₄ obtained by this preparation method will be described.
The powder of the Cu composite oxide is referred to as Fe-Cu-B.

After adding an appropriate amount of water to 200 g of Fe-Cu-B and 400 g of calcium carbonate and mixing well with a kneader, the mixture was formed into a pellet having a diameter of 5 mm and a length of 5 mm by an extruder. The pellet was dried at 100 ° C. for 10 hours, and then calcined at 350 ° C. for 5 hours in an air atmosphere to obtain a pellet-shaped adsorbent precursor (2). The composition of the adsorbent precursor (2) is Fe: Cu: Ca (Fe ₂ O ₃ : Cu
O: CaO) = 31.4: 15.7: 52.9
(% By mass).

Next, the pellet was heated at 400 ° C. for 3 hours in an atmosphere of hydrogen / nitrogen (5/95% by volume) to obtain an adsorbent (2).

Example 3 0.7 g of ruthenium oxide (manufactured by Tanaka Kikinzoku Co., Ltd., containing 65% by mass of ruthenium), F
200 g of e-Cu-B and 399.3 g of calcium carbonate were mixed well with a kneader while adding an appropriate amount of water, and then formed into a pellet having a diameter of 5 mm and a length of 5 mm by an extruder. After drying the pellets at 100 ° C. for 10 hours, 3
The mixture was calcined at 50 ° C. for 5 hours in an air atmosphere to obtain a pellet-shaped adsorbent precursor (3). The composition of the adsorbent precursor (3) is Ru: Fe: Cu: Ca (Ru: Fe ₂ O ₃ : C
uO: CaO) = 0.1: 31.4: 15.7:
52.8 (% by mass). Next, the pellet was heat-treated at 400 ° C. for 3 hours in an atmosphere of hydrogen / nitrogen (5/95% by volume) to obtain an adsorbent (3).

Example 4 An appropriate amount of water was added to 600 g of Fe-Cu-B, mixed well with a kneader, and formed into a pellet having a diameter of 5 mm and a length of 5 mm by an extruder. After drying the pellets at 100 ° C. for 10 hours, 3
Calcination was performed at 50 ° C. for 5 hours in an air atmosphere. Furthermore, the pellet was impregnated with a 6N-potassium acetate aqueous solution for 2 minutes, and then dried at 120 ° C. for 5 hours to obtain a pellet-shaped adsorbent precursor (4). Fig. 1 shows the X-ray diffraction of adsorbent precursor (4).
Shown in From FIG. 1, the adsorbent precursor (4) is CuFe ₂ O ₄
It can be seen that they contain. The composition of the adsorbent precursor (4) is Fe: Cu: K (Fe ₂ O ₃ : Cu
O: As _{K 2 O) = 59.6: 29.7} : 10.7
(% By mass).

Next, the pellets were placed at 400 ° C. for 3 hours.
Heat treatment (reduction treatment with an organic acid salt) was performed in a nitrogen atmosphere to obtain an adsorbent (4). Figure 2 shows the X-ray diffraction of adsorbent (4)
Shown in From FIG. 2, the adsorbent (4) is composed of Fe ₃ O ₄ and Cu.
It can be seen that they contain.

Example 5 200 g of Fe-Cu-B and 400 g of calcium carbonate were mixed well with a kneader while adding an appropriate amount of water, and then extruded with a diameter of 5 mm and a length of 5 m using an extruder.
m in the form of a pellet. The pellets were dried at 100 ° C. for 10 hours and then fired at 350 ° C. for 5 hours in an air atmosphere. Further, the pellet was impregnated with a 6N-potassium carbonate aqueous solution for 2 minutes, and dried at 120 ° C. for 5 hours to obtain a pellet-shaped adsorbent precursor (5). The composition of the adsorbent precursor (5) is Fe: Cu: Ca: K (Fe ₂ O
₃ : CuO: CaO: K ₂ O) = 28.1: 1
4.0: 47.2: 10.7 (% by mass). The pellets were then placed at 400 ° C. for 3 hours in hydrogen / nitrogen (5
/ 95% by volume) and heat treated in an atmosphere of adsorbent (5)
I got FIG. 3 shows the X-ray diffraction of the adsorbent (5). FIG. 3 shows that the adsorbent (5) contains Fe ₃ O ₄ and Cu.

Example 6 A pellet-shaped adsorbent precursor was obtained in the same manner as in Example 5 except that an aqueous 6N-potassium acetate solution was used instead of the aqueous 6N-potassium carbonate solution. The composition of this adsorbent precursor is Fe: C
u: Ca: K (as Fe ₂ O ₃ : CuO: CaO: K ₂ O) = 28.1: 14.0: 47.2: 10.7 (% by mass). Then, the pellets were heated at 400 ° C for 3 hours.
Heat treatment was performed in a nitrogen atmosphere for an hour to obtain an adsorbent (6). FIG. 4 shows the X-ray diffraction of the adsorbent (6). From FIG.
It can be seen that the adsorbent (6) contains Fe ₃ O ₄ and Cu.

<Example 7> 286 liters of ammonia water (NH ₃ , 25%) was added to 400 liters of water, and Snowtex NCS-30 (silica sol manufactured by Nissan Chemical Co., Ltd., about 30% by mass of SiO ₂ ) was added thereto. 24 kg). In the obtained solution, an aqueous solution of titanyl sulfate in sulfuric acid (Ti
Contains 250 g / l as O ₂ . Total sulfuric acid concentration 1,1
Aqueous titanium-containing sulfuric acid solution diluted by adding 153 liters (00 g / liter) to 300 liters of water was gradually added with stirring to obtain a coprecipitated 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) was Ti: Si = 4: 1 (atomic ratio).

An adsorbent precursor was prepared in the same manner as in Example 6 except that the above-mentioned TS-1 was used instead of calcium carbonate in Example 6, and a heat treatment was carried out in the same manner as in Example 6. A pellet of the adsorbent (7) having the composition shown in 1 was obtained.

<Examples 8 to 10> Instead of calcium carbonate in Example 6, titanium oxide, aluminum oxide,
Except that zirconium oxide was used, an adsorbent precursor was prepared in the same manner as in Example 6, and further heat-treated in the same manner as in Example 6 to obtain adsorbents (8) to (10) having compositions shown in Table 1.
Was obtained.

Example 11 0.7 g of ruthenium oxide (manufactured by Tanaka Kikinzoku Co., Ltd., containing 65% by mass of ruthenium)
Fe-Cu-B 200 g, calcium carbonate 399.3 g
After mixing well with a kneader while adding an appropriate amount of water, the mixture was formed into a pellet having a diameter of 5 mm and a length of 5 mm by an extruder. After drying the pellets at 100 ° C. for 10 hours,
Baking was performed at 350 ° C. for 5 hours in an air atmosphere. Furthermore, the pellet was impregnated with a 6N-potassium acetate aqueous solution for 2 minutes, and then dried at 120 ° C. for 5 hours to obtain a pellet-shaped adsorbent precursor. The composition of this adsorbent precursor is Ru: Fe:
Cu: Ca: K (Ru: Fe ₂ O ₃ : CuO: CaO:
K ₂ as O) = 0.1: 28.1: 14.0 : 47.
It was 1: 10.7 (% by mass). Next, the pellets were heat-treated at 400 ° C. for 2 hours in a nitrogen atmosphere to obtain an adsorbent (11).

<Examples 12 to 15> Table 1 is shown in the same manner as in Example 11 except that an aqueous solution of platinum nitrate, an aqueous solution of gold hydrochloride, an aqueous solution of rhodium nitrate and an aqueous solution of palladium nitrate were used in place of ruthenium oxide in Example 11. The pellets of the adsorbents (12) to (15) having the composition were obtained.

Example 16 200 g of Fe—Cu—B
After adding an appropriate amount of water to 46 g of basic cobalt carbonate and 370 g of calcium carbonate and mixing well with a kneader, the mixture was formed into a pellet having a diameter of 5 mm and a length of 5 mm by an extruder. After drying the pellets at 100 ° C. for 10 hours, 3
Calcination was performed at 50 ° C. for 5 hours in an air atmosphere. Furthermore, the pellet was impregnated with a 6N-potassium acetate aqueous solution for 2 minutes, and then dried at 120 ° C. for 5 hours to obtain a pellet-shaped adsorbent precursor. The composition of this adsorbent precursor is Fe: Cu: C
o: Ca: K (Fe ₂ O ₃ : CuO: Co ₃ O ₄ : Ca
O: as _{K 2 O) = 27.2: 13.6} : 6.1: 4
2.3: 10.8 (% by mass).

Next, the pellet was heated at 400 ° C. for 2 hours under a nitrogen atmosphere to obtain an adsorbent (16).

Comparative Example 1 α-Fe ₂ O ₃ 133.5
g, 66.5 g of CuO, and 400 g of calcium carbonate, and after adequately mixing with a kneader while adding an appropriate amount of water, the mixture was formed into a pellet having a diameter of 5 mm and a length of 5 mm by an extruder.
After drying the pellets at 100 ° C. for 10 hours,
The pellet was calcined in an air atmosphere at 5 ° C. for 5 hours to obtain a pellet-shaped adsorbent precursor. The composition of this adsorbent precursor is Fe: C
u: Ca (as Fe ₂ O ₃ : CuO: CaO) = 3
1.4: 15.7: 52.9 (% by mass). The pellets were then placed at 400 ° C. for 3 hours in hydrogen / nitrogen (5
/ 95% by volume) to obtain an adsorbent (Comparative 1).

<Comparative Example 2> In Example 5, Fe-C
Pellets of an adsorbent (comparative 2) having the composition shown in Table 1 were obtained in the same manner as in Example 5 except that a mixture of α-Fe ₂ O ₃ and CuO was used instead of uB.

<Comparative Examples 3 and 4> Examples 6 and 11
In the same manner as in Examples 6 and 11, except that a mixture of α-Fe ₂ O ₃ and CuO was used instead of Fe—Cu—B, the adsorbents having the compositions shown in Table 1 (Comparative 3) and (Comparative) 4) A pellet was obtained.

The adsorbents (1) to (10) obtained as described above
Table 1 summarizes the compositions of (16) and the comparative adsorbents (Comparative 1) to (Comparative 4). In Table 1, components A, B, C, D and E are shown as oxides and metals.

[0082]

[Table 1]

<Example 17> The adsorbents (1) to (4) and the comparative adsorbent (Comparative 1) were evaluated for nitrogen oxide adsorbing ability and sulfur oxide adsorbing ability by the following methods.

<Evaluation method (1)> 17.3 ml of adsorbent was
A glass reaction tube having an inner diameter of 30 mm was filled. This adsorbent
The synthesis gas (A) having the following composition is introduced into the layer under the following conditions.
Was.Synthesis gas (A) composition Nitric oxide (NO): 0.9 ppm, nitrogen dioxide (NO
₂): 0.1 ppm, sulfur dioxide (SO₂): 0.05
ppm, H₂O: 1.9% by volume, remaining: airProcessing conditions Gas amount: 17.3 NL / min, processing temperature: 25 ° C., empty
Speed (SV): 60,000 hr^-1(STP)
Humidity: 60% RH One hour after the introduction of the synthesis gas, the adsorbent layer
Nitrogen oxides in the synthesis gas at the inlet and outlet (NO
₂) The concentration was measured by a chemiluminescent NOx meter,
Object (SO₂) The concentration is ultraviolet absorption type SO₂And then
NO according to the formula ₂And SO₂The removal rate was calculated. NO₂Removal rate (%) = ｛(entrance NO₂Concentration-outlet NO₂
Concentration) / (Inlet NO₂Concentration) x 100 SO₂Removal rate (%) = ｛(inlet SO₂Concentration-outlet SO₂
Concentration) / (Inlet SO₂1 hour after the introduction of the synthesis gas (A), the adsorbent layer
Oxide (N 2) in the synthesis gas at the inlet and outlet of
O₂) Concentration and sulfur oxides (SO₂) Measure the concentration,
NO₂And SO₂The removal rate was calculated. Evaluation test results
Are shown in Table 2.

[0085]

[Table 2]

<Example 18> The adsorbents (5) to (16) and the comparative adsorbents (Comparative 2) to (Comparative 4) were evaluated for nitrogen oxide adsorbing ability and sulfur oxide adsorbing ability by the following methods.

<Evaluation Method (2)> After the nitrogen oxide adsorbing ability and sulfur oxide adsorbing ability of each adsorbent were measured by the same method as the evaluation method (1), the gas composition was changed and the following accelerated durability was measured. The test was performed.

<Accelerated Durability Test> A synthesis gas (B) having the following composition was introduced into the adsorbent layer under the following conditions. Synthesis gas (B) composition nitric oxide (NO): 2.7 ppm, nitrogen dioxide (NO
₂ ): 0.3 ppm, sulfur dioxide (SO ₂ ): 0.15
ppm, H ₂ O: 1.9% by volume, remaining: air treatment condition Gas amount: 17.3 NL / min, treatment temperature: 25 ° C., space velocity (SV): 60,000 hr ⁻¹ (STP), gas humidity: 60% RH After performing the accelerated durability test for 200 hours, one hour after introducing the synthesis gas (A), the nitrogen oxide (NO ₂ ) concentration in the synthesis gas at the inlet and the outlet of the adsorbent layer and The sulfur oxide (SO ₂ ) concentration was measured in the same manner as in the evaluation method (1), and the NO ₂ and SO ₂ removal rates were calculated. Table 3 shows the results of the evaluation test.

[0089]

[Table 3]

<Example 19> (Preparation of adsorbent for sulfur oxide) TS obtained in Example 7
-1 After kneading well with a kneader while adding an appropriate amount of water to 1,000 g of powder, 5 mm in diameter and 5 mm in length by an extruder.
Into a pellet. This pellet is heated at 100 ° C for 1 hour.
After drying for 0 hour, it was baked at 350 ° C. for 3 hours in an air atmosphere. Further, the pellet was impregnated with a 6N-sodium carbonate aqueous solution for 2 minutes, and then dried at 120 ° C. for 5 hours. The composition of the sulfur oxide adsorbent thus obtained was TS-1: Na (as TS-1: Na ₂ O) = 7.
6.1: 23.9 (% by mass). (Evaluation method) In the evaluation method (2) of Example 18, the adsorbent for sulfur oxide was added in a stage preceding the gas flow.
ml, and 17.3 m of the adsorbent (6) obtained in Example 6 in the subsequent stage.
Except for l filling, the nitrogen oxide adsorbing ability and the sulfur oxide adsorbing ability were evaluated in the same manner as in the evaluation method (2). Table 4 shows the results.

From the results in Tables 3 and 4, it can be seen that the durability performance of the adsorbent (6) is improved by installing the sulfur oxide adsorbent in the preceding stage.

<Example 20> In the evaluation method of Example 19, the adsorbent obtained in Example 11 (1
The nitrogen oxide adsorbing ability and the sulfur oxide adsorbing ability were evaluated in the same manner as in Example 18 except that 1) was used. Table 4 shows the results.

From the results shown in Tables 3 and 4, it can be seen that the durability performance of the adsorbent (11) is improved by installing the adsorbent for sulfur oxide in the former stage.

[0094]

[Table 4]

[0095]

The adsorbent of the present invention comprises nitrogen oxides and / or
Or, it has high adsorption performance to sulfur oxides, particularly low concentration nitrogen oxides and / or sulfur oxides, and shows excellent durability.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of an adsorbent precursor (4).

FIG. 2 is an X-ray diffraction diagram of an adsorbent (4).

FIG. 3 is an X-ray diffraction diagram of an adsorbent (5).

FIG. 4 is an X-ray diffraction diagram of the adsorbent (6).

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B01D 53/74 B01D 53/34 132Z 53/81 B01J 20/04 F term (Reference) 4D002 AA02 AA12 AC10 BA04 DA01 DA04 DA08 DA11 DA21 DA22 DA23 DA70 HA01 4G066 AA02B AA15B AA18B AA24B AA25B AA26B AA27B AA31A AA43A AA47A AA53A BA20 BA26 BA31 BA36 CA23 CA28 DA03 FA03 FA05 FA22 FA27

Claims (4)

[Claims] 1. An adsorbent for nitrogen oxides and / or sulfur oxides, comprising an adsorbent precursor containing a composite oxide of iron and copper. 2. The adsorbent further comprises an alkali metal element, titanium, silicon, aluminum, zirconium, an alkaline earth metal element, platinum, gold, ruthenium, rhodium, palladium, manganese, nickel, cobalt, zinc, vanadium, niobium, The nitrogen oxide and / or sulfur oxide adsorbent according to claim 1, wherein the adsorbent contains at least one element selected from chromium, molybdenum, and tungsten. 3. The Fe—C contained in the adsorbent precursor.
The adsorbent according to claim 1, wherein the u composite oxide is CuFe ₂ O ₄ . 4. A gas containing nitrogen oxides and / or sulfur oxides is brought into contact with the adsorbent according to claim 1 to remove nitrogen oxides and / or sulfur oxides. A method for removing nitrogen oxides and / or sulfur oxides.