JPH07112121A - Method for removing nox - Google Patents

Abstract

PURPOSE:To efficiently purify exhaust gas discharged from the internal-combustion engine of an automobile, etc., especially exhaust gas contg. excess oxygen without using a reducing agent such as ammonia and to remove NOx with a catalyst for purification of exhaust gas excellent in durability at high temp. in the presence of steam. CONSTITUTION:An apatite compd. is incorporated into zeolite and one or more kinds of active metals or an alkaline earth metal and one or more kinds of active metals are incorporated into the resulting zeolite having a molar ratio of 1: >=15 between SiO2 and Al2O3 to obtain a catalyst. Exhaust gas contg. excess oxygen as well as NOx and hydrocarbon is brought into contact with the catalyst to remove the NOx.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating an oxygen-excess exhaust gas containing nitrogen oxides discharged from a boiler, an automobile engine or the like with a catalyst, and more specifically to a method for treating the activity and durability. The present invention relates to a method for removing nitrogen oxides using a very excellent catalyst.

[0002]

2. Description of the Related Art As a method for removing nitrogen oxides in exhaust gas discharged from a boiler, an automobile engine, etc., a selective catalytic reduction method using ammonia in the presence of a catalyst, and an unburned gas by passing the exhaust gas through the catalyst The non-selective catalytic reduction method of reducing carbon monoxide and hydrocarbons has been put to practical use.

JP-A-60-125250 proposes a copper ion-exchanged zeolite as a catalyst capable of directly catalytically decomposing nitrogen oxides in the absence of a reducing agent.

Further, for purifying exhaust gas of a diesel engine and a lean-burn engine for the purpose of reducing fuel consumption, nitrogen oxides are selectively removed by reducing components such as unburned carbon monoxide and hydrocarbons even in the presence of excess oxygen. As a catalyst that can be reduced, a catalyst in which a base metal is contained in zeolite or the like has been proposed (for example, Japanese Patent Laid-Open No. 63-100919).

However, these proposed catalysts have problems in durability, especially at high temperatures, and have not been put into practical use.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to efficiently purify exhaust gas discharged from an internal combustion engine such as an automobile, particularly in excess of oxygen, without using a reducing agent such as ammonia, and It is intended to provide a method for purifying exhaust gas by using an exhaust gas purifying catalyst having excellent durability at high temperature in the presence of water vapor.

[0007]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that a zeolite containing an apatite compound, a catalyst containing one or more kinds of active metals or a similar zeolite, and an alkaline earth metal By using a catalyst in which a metal and one or more kinds of active metals are introduced,
The inventors have found that exhaust gas can be efficiently purified even after being used at high temperatures, and have completed the present invention.

That is, according to the present invention, a nitrogen oxide is used by using a catalyst containing an apatite compound and having a SiO ₂ / Al ₂ O ₃ molar ratio of at least 15 or more and one or more active metal species. And a method for removing nitrogen oxides from an oxygen-excess exhaust gas containing a hydrocarbon, and an apatite compound-containing zeolite having a SiO ₂ / Al ₂ O ₃ molar ratio of at least 15 or more, an alkaline earth metal and one kind It is intended to provide a method for removing nitrogen oxides from an oxygen-excess exhaust gas containing nitrogen oxides and hydrocarbons by using the catalyst containing the above active metal species.

The present invention will be described in more detail below.

The catalyst used in the present invention is a catalyst containing an apatite compound and having a SiO ₂ / Al ₂ O ₃ molar ratio of at least 15 or more and one or more active metal species, or a similar catalyst. The catalyst is a zeolite containing an alkaline earth metal and one or more active metal species.

It is essential that the raw material zeolite used in the present invention has a SiO ₂ / Al ₂ O ₃ molar ratio of 15 or more. The upper limit of the SiO ₂ / Al ₂ O ₃ molar ratio is not limited. If the SiO ₂ / Al ₂ O ₃ molar ratio is less than 15, sufficient durability cannot be obtained. It is preferably 15 to 200.

The type of zeolite is not particularly limited, and examples thereof include mordenite, ferrierite, zeolite β, ZSM-5, ZSM-8, ZSM-11 and ZS.
Zeolites such as M-12, ZSM-20 and ZSM-35 can be used. Among them, ZSM-5 is preferably used. Further, the method for producing these zeolites is not limited. It may also be a dealuminated zeolite such as zeolite Y or zeolite L.

As the raw material zeolite, a synthetic product or a calcined product thereof is used, but it is also possible to treat the ions such as Na in the raw material zeolite with an ammonium salt or a mineral acid and use it as an H type or an ammonium type. Furthermore, it can also be used after being ion-exchanged with K, Cs or the like.

The apatite compound used in the present invention has the general formula M having a crystal structure peculiar to apatite.
x (ZO ₄ ) ₆ A ₂ (M is a cation having a valence of 1 to 3, such as Ca, Pb, Cd, Sr, Ni, Eu, Al, Y, L.
a, Ce, Na, K are mentioned. Z is a cation having a valence of 3 to 7, such as P, As, V, Cr, Si, C, Al,
S and Re are mentioned. A is a 0 to 3 valent anion, and examples thereof include OH, F, Cl, Br, I, O, N, CO ₃ and H ₂ O. A stoichiometric apatite compound and a non-stoichiometric apatite compound represented by x ≦ 10). The stoichiometric apatite compound refers to one having a composition of x = 10, and the non-stoichiometric apatite compound is prepared by a precipitation method or the like and shows an apatite structure in terms of crystal structure.
It means that the composition is <10.

Further, as M of the apatite compound in the present invention, two or more kinds of ions may be contained, in which case Mg, Mn and Zn may be contained in addition to the above ions.

The method of introducing the apatite compound into the zeolite is not particularly limited, but an M-containing aqueous solution (M is the same as above) and a ZO ₄ -containing aqueous solution (Z is the same as above) are mixed in the presence of zeolite to prepare the apatite compound. It can be introduced by a coprecipitation method of precipitating, a physical mixing method of physically mixing the apatite compound in a solid phase or a liquid phase, and the like. Also, α
_{-Ca 3 (PO 4) 2,} β-Ca 3 (PO 4) 2, amorphous calcium phosphate _{(Ca 3 (PO 4) 2} ), CaHPO 4 · 2
It can also be introduced by introducing an apatite precursor such as H ₂ O or CaHPO ₄ into the zeolite and then hydrolyzing it under basic conditions to convert it into an apatite compound. The content of the apatite compound is not particularly limited,
0.1% by weight of apatite contained in zeolite
80 wt% is preferable, and 1 to 50 wt% is more preferable. In addition, the catalyst containing the apatite compound is 100 to 900 in order to stabilize the apatite compound.
The heat treatment may be carried out at ℃, preferably 300 to 600 ℃. The atmosphere for the heat treatment is not particularly limited, and examples thereof include an atmosphere such as vacuum, air and water vapor.

The zeolite of the present invention contains at least one active metal species. The active metal species may be any metal that is usually used for exhaust gas purification, such as C
Ib group such as u, Ag, Au, Fe, Co, Ni, Ru,
Group VIII such as Rh, Pd and Pt, VI such as Cr and Mo
Group a or Group VIIa such as Mn is used. Particularly preferred is Cu or Co.

The method for introducing the active metal is not particularly limited, and an impregnation-supporting method, an evaporation-drying method, an ion exchange method and the like can be used. When the active metal is present at the ion exchange site of zeolite, it becomes more active, so it is preferable to introduce the active metal by the ion exchange method. The ion exchange may be performed by mixing zeolite having an apatite compound introduced therein with an aqueous solution containing a salt of an active metal, stirring and washing.

As the active metal salt, active metal salts such as chlorides, nitrates, sulfates and acetates are preferably used. Further, an ammine complex salt of an active metal or the like can also be preferably used.

The addition amount, concentration, exchange temperature, time, etc. of the active metal at the time of ion exchange are not particularly limited, and a generally used method may be used. The amount of the active metal added is 0.5 in terms of the number of moles of the active metal atom with respect to the number of moles of the Al atom in the zeolite in order to have sufficient activity and durability.
-20 times is preferable. Further, the ion exchange slurry concentration is preferably 5 to 50% which is usually performed. Further, the ion exchange temperature and time are preferably room temperature to 100 ° C. and time of 5 minutes to 3 days in order to provide sufficient activity and durability. Further, the ion exchange operation can be repeated if necessary.

It is also possible to introduce one or more active metals into the raw material zeolite and then introduce the apatite compound by the above method to use as an exhaust gas purifying catalyst.

In the present invention, the above-mentioned catalyst may further contain an alkaline earth metal. The alkaline earth metal to be introduced is usually a metal that can be introduced into the zeolite by ion exchange, for example, Ca, Mg, Sr,
Ba or the like is used. Particularly preferred are Ba and Mg.

The method of introducing the alkaline earth metal is not particularly limited, but it is preferable to introduce it by a usual ion exchange method.
The ion exchange may be carried out by mixing the starting zeolite or the apatite compound or the zeolite into which the apatite compound is introduced into an aqueous solution containing a salt of an alkaline earth metal, stirring and washing.

As the alkaline earth metal salt, salts of alkaline earth metal chlorides, nitrates, sulfates, acetates and the like are preferably used. The amount of alkaline earth metal added, the concentration, the exchange temperature, the time, and the like at the time of ion exchange are not particularly limited, and a commonly used method may be used. The amount of the alkaline earth metal added is preferably 0.5 to 20 times the amount of Al in the zeolite contained in the catalyst in order to provide sufficient activity and durability. Further, the ion exchange slurry concentration is preferably 5 to 50% which is usually performed. Further, the ion exchange temperature and time are preferably room temperature to 100 ° C. and 5 minutes to 3 days in order to have sufficient activity and durability. Further, the ion exchange operation can be repeated if necessary.

The procedure for introducing the alkaline earth metal and the active metal is not particularly limited. For example, a method of introducing the apatite compound by exchanging the raw material zeolite with the alkaline earth metal and then introducing the active metal, the raw material zeolite with the alkaline earth metal Method of introducing apatite compound after metal exchange by introducing active metal, method of introducing apatite compound into raw material zeolite and exchanging active metal after alkaline earth metal exchange, activity of introducing apatite compound into raw material zeolite After introducing the metal, the method of exchanging the alkaline earth metal, introducing the active metal into the raw material zeolite and then introducing the alkaline earth-exchanged apatite, after introducing the active metal into the raw material zeolite and after introducing the apatite compound Method for exchanging alkaline earth metals, adding active metal to raw zeolite Examples thereof include a method of introducing the apatite compound after the introduction of the alkaline earth metal after the introduction.

However, finally, it suffices that the catalyst contains zeolite, an apatite compound, an alkaline earth metal and at least one active metal.
The introduction operation of the alkaline earth metal, the introduction operation of one or more active metal species, and the like can be performed in any combination and in any order.

As described above, the exhaust gas purifying catalyst used in the present invention can be prepared.

The exhaust gas-purifying catalyst used in the present invention is
It can also be used by mixing with a binder such as clay mineral and molding. As a preparation method at that time, for example, a raw material zeolite is preliminarily molded, apatite compound, a method of introducing an alkaline earth metal and an active metal into the molded body, or a zeolite having an apatite compound introduced therein is molded into the molded body. A method of introducing an alkaline earth metal and an active metal can be exemplified.

Binders used for forming zeolite are clay minerals such as kaolin, attapulgite, montmorillonite, bentonite, allophane and sepiolite. Alternatively, it may be a binderless zeolite molded product obtained by directly synthesizing a molded product without using a binder. Further, the exhaust gas-purifying catalyst used in the present invention can be wash-coated on a honeycomb-shaped substrate made of cordierite or metal.

The exhaust gas-purifying catalyst thus prepared is contacted with an oxygen-excess exhaust gas containing nitrogen oxides and hydrocarbons to remove nitrogen oxides. It is essential that the exhaust gas used in the present invention contains nitrogen oxides and hydrocarbons and is in excess of oxygen, but it is also effective when it contains carbon monoxide, hydrogen and the like. Exhaust gas in excess of oxygen means that excess oxygen is contained in excess of the amount of oxygen required to completely oxidize carbon monoxide, hydrocarbons and hydrogen contained in the exhaust gas. For example, in the case of exhaust gas discharged from an internal combustion engine of an automobile or the like, the air-fuel ratio is large (lean region). The space velocity, temperature, etc. at the time of removing the nitrogen oxides are not particularly limited, but the space velocity is 100 to 5000.
It is preferable that the temperature is 00 hr ⁻¹ and the temperature is 200 to 800 ° C.

[0031]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.

Example 1 A sodium silicate aqueous solution (SiO ₂ ; 250 g) was placed in an overflow type reaction tank having an actual volume of 2 liters in a stirring state.
/ L, Na ₂ O; 82 g / L, Al ₂ O ₃ ;
2.8 g / liter) and an aluminum sulfate aqueous solution (A
L ₂ O ₃ ; 8.8 g / liter, H ₂ SO ₄ ; 370 g / liter) and 3 liter / hr, 1 liter / hr, respectively.
It was continuously fed at a rate of hr. Reaction temperature is 30-32
C., the pH of the discharged slurry was 6.7 to 7.0.

After solid-liquid separation of the discharged slurry and sufficient washing with water, Na ₂ O; 0.75 wt%, Al ₂ O ₃ ; 0.77 w
t%, SiO ₂ ; 36.1 wt%, H ₂ O; 62.5 wt
% Of granular amorphous aluminosilicate homogeneous compound was obtained. The homogenous compound (2,860 g) and 3.2 wt% NaOH aqueous solution (6,150 g) were charged into an autoclave, and crystallized at 160 ° C. for 72 hours with stirring. The product was subjected to solid-liquid separation, washed with water and dried to obtain ZSM-5 type zeolite. As a result of chemical analysis, the composition had the following composition expressed as a molar ratio of oxides on an anhydrous basis.

1.3Na ₂ O, Al ₂ O ₃ , 41SiO ₂ 10 g of this zeolite was added to 100 cm ³ of an aqueous solution containing 2 g of NH ₄ Cl, stirred at 60 ° C. for 20 hours, washed and dried. NH ₄ ion exchange was carried out to obtain an ammonium-type zeolite.

10 g of this ammonium-type zeolite was added to a 0.07 mol / liter calcium acetate aqueous solution; 1
It was added to 43 cm ³ and stirred. 0.09 mol there
/ Liter ammonium dihydrogen phosphate aqueous solution; 71c
An aqueous solution of m ³ adjusted to pH = 8.5 with aqueous ammonia was added dropwise to coprecipitate a calcium phosphate salt, and the mixture was heated at 60 ° C. for 2 hours.
After stirring for an hour, it was washed and dried. Then, the mixture was calcined under air flow at 500 ° C. for 5 hours to obtain an apatite compound-containing zeolite.

This apatite compound-containing zeolite; 1
0 g of 0.07 mol / liter copper acetate aqueous solution; 10
Add to 0 cm ³ and pH = 10.5 with ammonia water
After adjusting the temperature to 20 ° C., stirring at room temperature for 20 hours, washing, and performing a Cu ion exchange operation. This operation was repeated twice and then dried to prepare catalyst 1. As a result of the X-ray diffraction measurement of the catalyst 1, peaks showing an apatite structure were observed in addition to zeolite. As a result of chemical analysis, the composition of catalyst 1 had the following composition represented by the molar ratio of oxides in the anhydrous base, and the apatite content was 7.1 wt%.

1.09CuO, 2.16CaO, 0.7
1P ₂ O ₅ , Al ₂ O ₃ , 41SiO ₂ Example 2 Instead of 0.07 mol / liter calcium acetate aqueous solution, 0.41 mol / liter calcium acetate aqueous solution and 0.09 mol / liter dihydrogen phosphate were used. A catalyst 2 was prepared in the same manner as in Example 1 except that a 0.55 mol / liter ammonium dihydrogen phosphate aqueous solution was used instead of the ammonium aqueous solution. Catalyst 2
As a result of X-ray diffraction measurement, a peak showing the structure of apatite was observed in addition to zeolite. Further, as a result of chemical analysis, the composition of the catalyst 2 has the following composition represented by the molar ratio of the oxide in the anhydrous base, and the apatite content is 3
It was 3 wt%.

1.88 CuO, 14.0 CaO, 4.8
9P ₂ O ₅ , Al ₂ O ₃ , 41SiO ₂ Example 3 10 g of a sodium type zeolite immediately after synthesis prepared by the same method as in Example 1; 10 g was added to 100 cm ³ of an aqueous solution containing 2.8 g of KCl, and 60 The mixture was stirred at 0 ° C. for 20 hours, washed, and this operation was repeated twice, and then dried to obtain a potassium-type zeolite. As a result of chemical analysis, the composition had the following composition expressed as a molar ratio of oxides on an anhydrous basis.

K ₂ O, Al ₂ O ₃ , 41SiO ₂ This potassium type zeolite; 10 g 0.21 mol /
1 liter of calcium acetate aqueous solution; 143 cm ³ was added and stirred. A 0.28 mol / liter ammonium dihydrogen phosphate aqueous solution; an aqueous solution of 71 cm ³ adjusted to pH = 8.5 with ammonia water was added dropwise to coprecipitate a calcium phosphate salt, and the mixture was stirred at 60 ° C. for 2 hours. ,
Washed and dried. Then, under air circulation, 500 ° C, 5
The potassium type zeolite containing an apatite compound was obtained by firing for a time.

10 g of this potassium-type zeolite containing apatite compound was added to 100 cm ³ of 0.07 mol / liter copper acetate aqueous solution, stirred at 40 ° C. for 20 hours, washed and subjected to Cu ion exchange operation. This operation was repeated 4 times and then dried to prepare catalyst 3. Catalyst 3
As a result of X-ray diffraction measurement, a peak showing the structure of apatite was observed in addition to zeolite. Further, as a result of chemical analysis, the composition of the catalyst 3 has the following composition expressed by the molar ratio of oxides in the anhydrous base, and the apatite content is 1
It was 8 wt%.

2.16CuO, 6.19CaO, 2.3
9P ₂ O ₅ , 0.03K ₂ O, Al ₂ O ₃ , 41SiO ₂ Example 4 In Example 1, 0.21 mol / liter calcium acetate aqueous solution was used instead of 0.07 mol / liter calcium acetate aqueous solution. Instead of 0.09 mol / liter ammonium dihydrogen phosphate aqueous solution, 0.28
A catalyst 4 was prepared in the same manner except that a mol / liter ammonium dihydrogen phosphate aqueous solution was used and Co ion exchange was performed instead of Cu ion exchange. Co ion exchange was performed as follows.

Apatite compound-containing zeolite; 10 g
Was added to a 0.22 mol / liter Co (II) acetate aqueous solution; 90 cm ³ , and the mixture was stirred at 60 ° C. for 20 hours, washed, and Co ion exchange was performed. This operation was repeated twice and then dried to prepare catalyst 4. X of catalyst 4
As a result of the line diffraction measurement, peaks showing an apatite structure were observed in addition to zeolite. Further, as a result of chemical analysis, the composition of the catalyst 4 has the following composition represented by the molar ratio of oxides in the anhydrous base, and the apatite content is 25 w.
It was t%.

1.40 CoO, 7.18 CaO, 2.4
0P ₂ O ₅ , Al ₂ O ₃ , 41SiO ₂ Example 5 Ammonium-type zeolite prepared in the same manner as in Example 1;
10 g of the commercially available hydroxyapatite (manufactured by Kishida Chemical Co., Ltd.); 2.55 g was stirred and mixed in a 100 cm ³ aqueous solution, and then washed and dried. Then, the mixture was calcined under air flow at 500 ° C. for 5 hours to obtain an apatite compound-containing zeolite.

This apatite compound-containing zeolite; 1
0 g of 0.07 mol / liter copper acetate aqueous solution 100
cm ³ was added, pH was adjusted to 10.5 with aqueous ammonia, and the mixture was stirred at room temperature for 20 hours, washed, and subjected to Cu ion exchange operation. This operation was repeated twice and then dried to prepare catalyst 5. As a result of X-ray diffraction measurement of the catalyst 5,
In addition to zeolite, peaks showing the structure of apatite were observed. As a result of chemical analysis, the composition of the catalyst 5 had the following composition represented by the molar ratio of oxides in the anhydrous base, and the apatite content was 18 wt%.

1.40 CuO, 6.03 CaO, 2.0
0P ₂ O ₅ , Al ₂ O ₃ , 41SiO ₂ Example 6 Ammonium-type zeolite prepared in the same manner as in Example 1;
10 g of 0.1 mol / liter copper acetate aqueous solution 41c
m ³ was added, pH was adjusted to 10.5 with aqueous ammonia, and the mixture was stirred at room temperature for 20 hours, washed, and subjected to Cu ion exchange operation. After repeating this operation twice, it was dried to obtain a Cu-exchanged zeolite.

2.5 g of commercially available hydroxyapatite (manufactured by Kishida Chemical Co., Ltd.);
After stirring and mixing in 100 cm ³ of water with
Washed and dried. Then, under air circulation, 500 ° C, 5
Bake for hours. Catalyst 6 was prepared. As a result of the X-ray diffraction measurement of the catalyst 6, peaks showing the structure of apatite were observed in addition to zeolite. As a result of chemical analysis, the composition of catalyst 6 had the following composition expressed by the molar ratio of oxides in the anhydrous base, and the apatite content was 20 wt%.

1.05CuO, 7.17CaO, 2.1
5P ₂ O ₅ , Al ₂ O ₃ , 41SiO ₂ Example 7 Ammonium-type zeolite prepared in the same manner as in Example 1;
10 g was added to a 0.20 mol / liter ammonium nitrate aqueous solution; 286 cm ³ , and the mixture was stirred. Then, the pH was adjusted to 9.0 with ammonium water. there,
A 0.21 mol / liter strontium nitrate aqueous solution; 143 cm ³ and a 0.14 mol / liter diammonium hydrogen phosphate aqueous solution; 143 cm ³ were simultaneously and slowly added dropwise to coprecipitate the phosphorus strontium salt. The pH was adjusted to 9.0 with aqueous ammonia. Then, the mixture was stirred at 30 ° C. for 17 hours, washed, and dried. Then, the mixture was calcined under air flow at 500 ° C. for 5 hours to obtain an apatite compound-containing zeolite.

This apatite compound-containing zeolite; 1
0 g of 0.07 mol / liter copper acetate aqueous solution 100
cm ³ was added, pH was adjusted to 10.5 with aqueous ammonia, and the mixture was stirred at room temperature for 20 hours, washed, and subjected to Cu ion exchange operation. This operation was repeated twice and then dried to prepare catalyst 7. As a result of X-ray diffraction measurement of the catalyst 7,
In addition to zeolite, peaks showing the structure of apatite were observed. As a result of chemical analysis, the composition of the catalyst 7 had the following composition represented by the molar ratio of oxides in the anhydrous base, and the apatite content was 25 wt%.

1.29CuO, 6.91SrO, 2.3
6P ₂ O ₅ , Al ₂ O ₃ , 41SiO ₂ Durability was evaluated using the catalysts 1 to 7 obtained in Examples 1 to 7.

Each catalyst is press-molded and then pulverized to 12 to
The size was adjusted to 20 mesh. 2 cm ³ of the gas was charged into a fixed pressure fixed bed flow type reaction tube, and a gas simulating the exhaust gas of a lean burn engine (Table 1) was supplied at a space velocity of 120,000 / hr.
Durability treatment was carried out at 800 ° C for 5 hours while flowing in the water. afterwards,
After pretreatment with the same gas at 550 ° C. for 30 minutes,
The steady purification activity at each temperature was measured. The steady purification activity is
The conversion rate after holding for 1 hour at each temperature was taken. The obtained results are shown in Table 2.

[0051]

[Table 1]

[0052]

[Table 2]

Comparative Example 1 A Cu-type ZSM-was prepared in the same manner as in Example 1 except that the apatite compound was not loaded.
5 (comparative catalyst 1) was obtained. As a result of chemical analysis, the composition had the following composition represented by the molar ratio of oxides in the anhydrous base.

1.03 CuO, Al ₂ O ₃ , 41 SiO ₂ Comparative Example 2 Co-type ZSM- was prepared in the same manner as in Example 4 except that the apatite compound was not loaded.
5 (comparative catalyst 2) was obtained. As a result of chemical analysis, the composition had the following composition represented by the molar ratio of oxides in the anhydrous base.

1.40 CoO, Al ₂ O ₃ , 41 SiO ₂ Comparative Example 3 In Example 1, 0.14 mol / liter was used instead of 0.09 mol / liter ammonium dihydrogen phosphate aqueous solution.
Calcium pyrophosphate-containing Cu type ZSM-5 (comparative catalyst 3) was performed in the same manner except that 1 liter of an aqueous solution of ammonium dihydrogen phosphate was used and that the pH of the aqueous solution of ammonium dihydrogen phosphate was not adjusted. Was prepared. As a result of the X-ray diffraction measurement of the comparative catalyst 3, peaks showing the structure of calcium pyrophosphate were observed in addition to zeolite. As a result of chemical analysis, the composition of the comparative catalyst 3 has the following composition expressed by the molar ratio of oxides in the anhydrous base, and the content of calcium pyrophosphate is 6.2 wt.
%Met.

1.02CuO, 1.46CaO, 0.7
2P ₂ O ₅ , Al ₂ O ₃ , 41SiO ₂ Using the comparative catalysts 1 to 3 obtained in Comparative Examples 1 to 3, the catalyst durability was evaluated in the same manner as the method for the catalysts 1 to 7. It was The results obtained are shown in Table 3.

[0057]

[Table 3]

Example 8 Na-type zeolite 10 prepared by the same method as in Example 1
g was added to 100 cm ³ of an aqueous solution containing 8.3 g of BaCl ₂ ; the mixture was stirred at 60 ° C. for 20 hours, washed, dried and subjected to Ba ion exchange operation. After repeating this operation twice, it was dried to obtain barium-type zeolite.

10 g of this barium-type zeolite;
21 mol / liter calcium acetate aqueous solution 143c
m ³ and stirred. An aqueous solution of 0.28 mol / liter ammonium dihydrogen phosphate aqueous solution 71 cm ³ adjusted to pH = 8.5 with aqueous ammonia was added dropwise thereto to coprecipitate a calcium phosphate salt, and the mixture was stirred at 60 ° C. for 2 hours. Washed and dried. Then 50 under air circulation
The barium-type zeolite containing an apatite compound was obtained by firing at 0 ° C. for 5 hours.

10 g of this barium-type zeolite containing an apatite compound was added to 100 cm ³ of 0.07 mol / liter copper acetate aqueous solution, and pH = 1 was added with ammonia water.
Adjust to 0.5, stir at room temperature for 20 hours, then wash,
Cu ion exchange operation was performed. This operation was repeated twice and then dried to prepare catalyst 8. As a result of X-ray diffraction measurement of the catalyst 8, a peak showing a structure of apatite other than zeolite
Ku was observed. As a result of chemical analysis, the composition of catalyst 8 had the following composition represented by the molar ratio of oxides in the anhydrous base, and the apatite content was 17 wt%.

1.82 CuO, 5.96 CaO, 2.4
2P ₂ O ₅ , 0.55BaO, Al ₂ O ₃ , 41SiO ₂ Example 9 10 g of Na-type zeolite immediately after synthesis prepared in the same manner as in Example 8 was added to NH ₄ Cl;
cm ³ and stirred at 60 ° C. for 20 hours, washed, dried and subjected to NH ₄ ion exchange to obtain an ammonium-type zeolite.

10 g of this ammonium-type zeolite was loaded with the apatite compound by the same procedure as in Example 1 and calcined to obtain an apatite-containing ammonium-type zeolite.

10 g of this apatite compound-containing ammonium-type zeolite; was added to 200 cm ³ of an aqueous solution containing 9.2 g of Ba (NO ₃ ) _{2 and the} mixture was stirred at 60 ° C. for 20 hours, washed and dried, and then Ba ion-exchanged. The operation was performed.
This operation was repeated twice and then dried to obtain a barium-type apatite compound-containing zeolite.

10 g of this barium-type apatite compound-containing zeolite; was added to 100 cm ³ of a 0.07 mol / liter copper acetate aqueous solution, and the pH was adjusted to
It was adjusted to 10.5, stirred at room temperature for 20 hours, washed, and subjected to Cu ion exchange operation. This operation was repeated twice and then dried to prepare catalyst 9. As a result of the X-ray diffraction measurement of the catalyst 9, peaks showing the structure of apatite were observed in addition to zeolite. As a result of chemical analysis, the composition of catalyst 9 had the following composition expressed by the molar ratio of oxides in the anhydrous base, and the apatite content was 15 wt%.

0.91CuO, 4.90CaO, 1.8
5P ₂ O ₅ , 0.71BaO, Al ₂ O ₃ , 41SiO ₂ Example 10 A catalyst 10 was prepared in the same manner as in Example 9 except that Mg exchange was performed instead of Ba exchange in Example 9. did. Mg ion exchange was performed as follows. Mg containing 10 g of ammonium-type zeolite containing apatite compound
The mixture was added to 200 cm ³ of an aqueous solution containing (NO ₃ ) ₂ ; 9.1 g, stirred at 60 ° C. for 20 hours, washed and dried, and this operation was repeated twice to carry out a Mg ion exchange operation. As a result of the X-ray diffraction measurement of the catalyst 10, peaks showing the structure of apatite were observed in addition to zeolite. Further, as a result of chemical analysis, the composition of the catalyst 10 had the following composition represented by the molar ratio of oxides in the anhydrous base, and the apatite content was 17 wt%.

1.40 CuO, 5.71 CaO, 2.1
0P ₂ O ₅ , 0.25MgO, Al ₂ O ₃ , 41SiO ₂ Example 11 0.21 mol / liter calcium acetate aqueous solution 14
3 cm ³ was stirred. An aqueous solution prepared by adjusting 71 cm ³ of 0.28 mol / liter ammonium dihydrogen phosphate aqueous solution to pH = 8.5 with ammonia water was added dropwise thereto,
A calcium phosphate salt was coprecipitated, stirred at 60 ° C. for 2 hours and then washed to obtain an apatite gel. The obtained apatite gel was used as an aqueous solution 200 containing Ba (NO ₃ ) ₂ ; 9.2 g.
cm ³ and stirred at 60 ° C. for 20 hours, washed and subjected to Ba ion exchange operation. This operation was repeated twice to obtain a Ba-exchanged apatite gel.

10 g of ammonium-type zeolite prepared in the same manner as in Example 9 was added to 41 cm ³ of a 0.1 mol / liter copper acetate aqueous solution, and the pH was adjusted to 1 with ammonia water.
Adjust to 0.5, stir at room temperature for 20 hours, then wash,
Cu ion exchange operation was performed. After repeating this operation twice, it was dried to obtain a Cu-exchanged zeolite.

The Ba-exchanged apatite gel thus obtained and Cu-exchanged zeolite were stirred and mixed in a 100 cm ³ aqueous solution at room temperature for 0.5 hours, washed, dried, and then air-circulated at 500 ° C. Catalyst 11 after firing for 5 hours
Was prepared. As a result of the X-ray diffraction measurement of the catalyst 11, peaks showing the structure of apatite other than zeolite were observed.
Further, as a result of chemical analysis, the composition of the catalyst 11 has the following composition represented by the molar ratio of oxides in the anhydrous base:
The content of this apatite was 18 wt%.

1.02CuO, 6.11CaO, 2.3
9P ₂ O ₅ , 0.51BaO, Al ₂ O ₃ , 41SiO ₂ Example 12 A catalyst 12 was prepared in the same manner as in Example 9 except that Co exchange was performed instead of Cu exchange in Example 9. did. Co ion exchange was performed as follows. 0.22 m of 10 g of barium-type apatite compound-containing zeolite
It was added to 90 cm ³ of an aqueous solution of Co (II) acetate of ol / liter, stirred at 60 ° C. for 20 hours, washed, and Co ion-exchanged. This operation was repeated twice and then dried to prepare catalyst 5. As a result of X-ray diffraction measurement of the catalyst 5,
In addition to zeolite, peaks showing the structure of apatite were observed. As a result of chemical analysis, the composition of the catalyst 12 was represented by the molar ratio of oxides in the anhydrous base and had the following composition, and the apatite content was 25 wt%.

1.42CoO, 7.15CaO, 2.3
8P ₂ O _5, 0.70BaO, using Al ₂ O _3, 41SiO catalysts 8-12 obtained in Example ₂ 8-12, Similarly durability evaluation methods as those employed on the catalyst 1-7 I went. The results obtained are shown in Table 4.

[0071]

[Table 4]

Example 13 Calcium acetate aqueous solution of 0.21 mol / l 143 cm 3
³ and 0.29 mol / l magnesium acetate aqueous solution 50
cm ³ was mixed, 10 g of ammonium-type zeolite prepared by the same method as in Example 1 was added, and the mixture was stirred.
71 cm ³ of 0.29 mol / l ammonium dihydrogen phosphate aqueous solution was added dropwise to the solution, the pH of which was adjusted to 8.5 by ammonia water, and phosphomagnesium calcium salt was coprecipitated and stirred at 60 ° C. for 2 hours. Washed, dried. Then, the mixture was calcined under air flow at 500 ° C. for 5 hours to obtain an apatite compound-containing zeolite in which M was composed of two or more cations.

10 g of the apatite compound-containing zeolite in which M is composed of two or more kinds of cations was added to 0.07 mol.
/ L was added to the copper acetate solution 100 cm ^3, and adjusted to pH = 10.5 by aqueous ammonia, stirred for 20 hours at room temperature, washed and subjected to Cu ion exchange operation. This operation was repeated twice and then dried to prepare the catalyst 13. As a result of X-ray diffraction measurement of the catalyst 13, peaks showing an apatite structure were observed in addition to zeolite. As a result of chemical analysis, the composition of the catalyst 13 had the following composition represented by the molar ratio of oxides in the anhydrous base.

1.39 CuO, 6.29 CaO, 0.0
_{6MgO, 2.20P 2 O 5, Al} 2 O 3, 41SiO 2 apatite content this M is composed of two or more cations was 18 wt%.

Example 14 A catalyst 14 was prepared in the same manner as in Example 13 except that 0.028 mol / l manganese acetate aqueous solution was used in place of 0.028 mol / l magnesium acetate aqueous solution. As a result of the X-ray diffraction measurement of the catalyst 14, peaks showing the structure of apatite were observed in addition to zeolite. As a result of chemical analysis, the composition of the catalyst 14 had the following composition represented by the molar ratio of oxides in the anhydrous base.

1.69 CuO, 6.19 CaO, 0.3
_{6MgO, 2.31P 2 O 5, Al} 2 O 3, 41SiO 2 apatite content this M is composed of two or more cations was 18 wt%.

Example 15 A catalyst 15 was prepared in the same manner as in Example 13, except that a 0.028 mol / l aqueous solution of zinc acetate was used instead of the 0.028 mol / l aqueous solution of magnesium acetate. As a result of the X-ray diffraction measurement of the catalyst 15, peaks showing the structure of apatite were observed in addition to zeolite. Also,
As a result of chemical analysis, the composition of the catalyst 15 had the following composition represented by the molar ratio of oxides in the anhydrous base.

1.34 CuO, 6.11 CaO, 0.3
_{6ZnO, 2.41P 2 O 5, Al} 2 O 3, 41SiO 2 apatite content this M is composed of two or more cations was 18 wt%.

Example 16 A catalyst 16 was prepared in the same manner as in Example 13 except that 0.028 mol / l cerium acetate aqueous solution was used instead of 0.028 mol / l magnesium acetate aqueous solution. As a result of the X-ray diffraction measurement of the catalyst 16, peaks showing the structure of apatite were observed in addition to zeolite. As a result of chemical analysis, the composition of the catalyst 16 had the following composition expressed by the molar ratio of oxides in the anhydrous base.

1.46CuO, 6.33CaO, 0.1
7Ce ₂ O ₃ , 2.46P ₂ O ₅ , Al ₂ O ₃ , 41SiO ₂ The content of apatite in which M was composed of two or more cations was 18 wt%.

Example 17 A 0.12 mol / l cerium acetate aqueous solution was used in place of the 0.028 mol / l magnesium acetate aqueous solution, and 0.34 mol was used in place of the 0.29 mol / l ammonium dihydrogen phosphate aqueous solution. A catalyst 17 was prepared in the same manner as in Example 13 except that an aqueous solution of ammonium dihydrogen phosphate of 1 / l was used. As a result of the X-ray diffraction measurement of the catalyst 17, peaks showing an apatite structure were observed in addition to zeolite. Further, as a result of chemical analysis, the composition of the catalyst 17 had the following composition represented by the molar ratio of oxides in the anhydrous base.

1.42CuO, 5.35CaO, 0.6
5Ce ₂ O ₃ , 2.79P ₂ O ₅ , Al ₂ O ₃ , 41SiO ₂ The apatite content in which M was composed of two or more cations was 18 wt%.

Example 18 The same procedure as in Example 13 was carried out except that Co ion exchange was performed instead of Cu ion exchange, and the catalyst 18 was used.
Was prepared. Co ion exchange was performed as follows.

0.22 mol / l of 10 g of zeolite containing an apatite compound in which M is composed of two or more cations
Was added to 90 cm ³ of Co (II) acetate aqueous solution at 60 ° C.
After stirring at 20 ° C. for 20 hours, it was washed and Co ion exchange was performed. This operation was repeated twice and then dried to prepare the catalyst 18. As a result of X-ray diffraction measurement of the catalyst 18, peaks showing the structure of apatite were observed in addition to zeolite. As a result of chemical analysis, the composition of the catalyst 18 had the following composition represented by the molar ratio of oxides in the anhydrous base.

1.10 CoO, 6.30 CaO, 0.0
7MgO, 2.22P ₂ O ₅ , Al ₂ O ₃ , 41SiO ₂ The content of apatite in which M was composed of two or more kinds of cations was 18 wt%.

Catalysts 13-1 obtained in Examples 13-18
Durability was evaluated using No. 8.

Each catalyst was press-molded and then pulverized to 12 to
The size was adjusted to 20 mesh. 2 cm ³ of the gas was charged into a fixed pressure fixed bed flow type reaction tube, and a gas simulating the exhaust gas of a lean burn engine (Table 1) was supplied at a space velocity of 120,000 / hr.
Durability treatment was carried out at 700 ° C. for 5 hours while flowing. afterwards,
After pretreatment at 550 ° C. for 30 minutes, the steady-state purification activity at each temperature was measured. The steady-state purification activity was defined as the conversion rate after holding at each temperature for 1 hour. The results obtained are shown in Table 5.

[0088]

[Table 5]

Using the comparative catalysts 1 and 2 obtained in comparative examples 1 and 2, the catalyst durability was evaluated in the same manner as the method for the catalysts 13 to 18. The obtained results are shown in Table 6.

[0090]

[Table 6]

[0091]

As is clear from Tables 2 to 6, according to the method of the present invention, nitrogen oxides can be efficiently removed even after the catalyst is used at a high temperature.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C01B 33/36 7202-4G B01D 53/36 102 D

Claims (2)

[Claims] 1. A SiO containing an apatite compound.
Nitrogen characterized by contacting a catalyst in which one or more active metals are contained in zeolite having a ₂ / Al ₂ O ₃ molar ratio of at least 15 or more with an exhaust gas in excess of oxygen containing nitrogen oxides and hydrocarbons. Oxide removal method. 2. A SiO containing an apatite compound.
Contacting a catalyst in which an alkaline earth metal and one or more active metals are contained in a zeolite having a ₂ / Al ₂ O ₃ molar ratio of at least 15 or more with an oxygen-excess exhaust gas containing nitrogen oxides and hydrocarbons And a method for removing nitrogen oxides.