JP2000197822A - Catalyst for decomposing and removing nitrogen oxide and method for decomposing and removing nitrogen oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly active and practical decomposition catalyst for directly decomposing and removing NOX, especially NO, in a waste gas of all types of combustion apparatus without using a reducing agent and to provide a practical nitrogen oxide removal method using the catalyst for a waste gas containing oxygen and steam. SOLUTION: This nitrogen oxide decomposition catalyst to be used comprises catalytically active components containing at least one type of metal compounded oxide having a composition defined as the formula: AB1-XMXO3±Z (wherein A is an alkaline earth metal; B is a metal selected from titanium group metals; and M is a metal selected from iron group metals, copper group metals, and platinum group metals): and having a perovskite type crystal structure and a basic metal oxide such as rare earth metal oxides on which the catalytically active components are deposited. The active components are provided with especially excellent capability in the case they are produced from alkoxides. The catalyst has high durability to poisoning by oxygen and steam and a waste gas containing steam is brought into contact with the catalyst in the presence of or in the absence of oxygen at 200-900 deg.C without dehumidifying or drying the waste gas and without adding a reducing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the plant or nitrogen oxides are discharged from stationary sources or mobile sources such as automobiles such as a home NO _X, in particular nitrogen monoxide NO, it is decomposed directly without reducing agent The present invention relates to a catalyst to be removed by removal, a method for preparing the catalyst, and a method for decomposing and removing nitrogen oxides using the catalyst.

[0002]

2. Description of the Related Art Nitrogen oxide removal techniques include a method of reducing and removing NO using ammonia, hydrocarbons and the like as a reducing agent, and a method of directly removing NO into N ₂ and O in the absence of a reducing agent.
There is a direct decomposition method of decomposing into _two . Ammonia selective catalytic reduction method as a representative example of the former may (SCR), has been commercialized in NO _x removal in stationary sources such as flue gas plant boilers, utility as denitration method in a mobile sources Not a target.

Further, a three-way catalytic method for simultaneously removing three components of NO _X , CO, and unburned hydrocarbons in exhaust gas by stoichiometric combustion in which the air-fuel ratio (weight ratio between air and fuel) is maintained at an optimum level. (TWC) is also considered to be a reduction removal method using CO or a hydrocarbon as a reducing agent. in this way,
A high denitration rate is obtained by using the Rh-Pt-based catalyst, and it is applied to a wide range including a moving source. However, the stoichiometric combustion method is disadvantageous in terms of high efficiency and energy saving. On the other hand, the lean combustion method having a large air-fuel ratio has higher combustion efficiency than stoichiometric combustion, and is advantageous as a combustion technique in terms of energy saving. However, since a large amount of O ₂ exists in the exhaust gas of lean burn, Rh-P
The t-based catalyst does not show denitration performance.

[0004] For a method of oxygen reduction remove NO _X in the exhaust gas present, there was no other than the conventional method using ammonia as a reducing agent, in recent years denitration method for a hydrocarbon as a reducing agent, while low denitration ratio Has also begun to be put into practical use. However, these reducing denitration method, exhaust gas composition (NO _X concentration, O _X concentration, reducing agent amount, etc.) since denitration performance greatly varies, in order to ensure a practical denitration rate, the reducing agent Equipment for controlling the addition rate and combustion state is required.

[0005] In the absence of a reducing agent, NO _X is directly converted to N ₂
O ₂ and direct decomposition method decomposes in, because the denitration performance does not depend on the exhaust gas composition, it is possible to construct a simple denitration system. Therefore, the type of the combustor that is the exhaust gas generation source is not limited to a specific type but has a wide application range. But,
It is extremely difficult to directly decompose NO _{X in} the presence of oxygen, such as when purifying exhaust gas of a lean burn gasoline engine or exhaust gas of a diesel engine in which about 10% by volume of oxygen remains. At the laboratory level, a metal-supported zeolite catalyst obtained by adding copper, Ga, Ce, etc. to ZSM-5 zeolite (for example, Japanese Patent Publication No. 60-12909) has been proposed, but this catalyst has a high activity in the absence of oxygen. Even in the presence of oxygen, the activity is significantly reduced.

[0006] Perovskite type as another direct cracking catalyst
Metal oxides have been proposed (Yasutake Teraoka, Shuichi Kagawa, etc.
catalyst33(2) 73-76 (1991)), which is 60
Excellent activity and durability even at high temperatures of 0 ° C or higher, and
It is known that the activity per unit weight of the catalyst is high.
Among them, the composition is La_0.8Sr_0.2CoO₃Indicated by
Perovskite-type metal oxides have the highest unit weight
It is known that it has a high activity. Also, K₂Ni
F₄La having type crystal structure_1.6Sr_0.4 CuO₄
Is known to have the highest activity per unit surface area
(Hiroyuki Yasuda, Makoto Misono et al., Catalyst33(2) 69-
72 (1991)).

However, the catalytic activity of conventionally known perovskite oxides has not yet reached a practical level. In particular, regarding the direct decomposition of NO in the presence of oxygen, which has a high technical demand, even the above-mentioned La _0.8 Sr _0.2 CoO _{3 has a} conversion rate of at most 10% at a reaction temperature of 800 ° C. under an oxygen content of 5% by volume. It only shows the degree.

The present inventors have conducted research and development on the improvement of the practical catalytic activity of perovskite-type metal oxides in the direct decomposition of NO, and have previously applied for patents on some metal oxides (Japanese Patent Application No. Hei 10-1998). 004094, Japanese Patent Application No. 10
-15720 and Japanese Patent Application No. 10-151841)
However, there is a need for a catalyst having high durability against poisoning by exhaust gas components.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a practical and highly active catalyst capable of directly decomposing and removing NO _X , in particular, NO, in exhaust gas from all combustion equipment without a reducing agent. . Another object of the present invention is to provide a catalyst preparation method which exhibits higher poisoning durability of the catalyst, and a practical exhaust gas denitration method using the catalyst.

[0010]

According to the present invention, the Ti site of a perovskite oxide is changed to Fe, Cu or P
The above problem is solved by using a ternary perovskite-type composite oxide partially substituted with t supported on a rare earth oxide or the like.

[0011] The present invention, at least one composition of the metal composite oxide, the active ingredient in a nitrogen oxide decomposing catalyst has the general formula _{AB 1-X M X O 3} + -Z ( where A is an alkaline earth One metal selected from elements, B is one metal selected from titanium group elements, M is one metal selected from iron group, copper group or platinum group elements, 0 <x <1, Z
Is the number of oxygen vacancies or excess oxygen in the metal oxide at normal temperature and atmospheric pressure), at least one of the metal composite oxides has a perovskite crystal structure, and the catalytically active component is a basic metal. An invention of a decomposition catalyst characterized by being supported on an oxide.

The carrier may be a commonly used one as long as it is a basic metal oxide, but magnesia or a rare earth oxide is particularly preferred.

A second aspect of the present invention is an invention of a preparation method relating to the catalyst, characterized in that a catalytically active component is prepared using an alkoxide of a metal constituting the metal composite oxide as the catalytically active component. It is.

According to a third aspect of the present invention, a nitrogen oxide is reacted with the decomposition catalyst in a temperature range of 200 ° C. to 900 ° C. in the absence of a reducing agent.
The present invention relates to a method for removing nitrogen oxides by direct decomposition, wherein the contact is carried out in the presence or absence of oxygen.

In the third aspect of the present invention, in the absence of a reducing agent, nitrogen oxides are reacted with the decomposition catalyst in a temperature range of 200
Nitrogen oxides can also be directly decomposed and removed by contacting at -900C in the presence of oxygen and water vapor.

In the present invention, A in the general formula is one kind of metal selected from alkaline earth elements, ie, Ca, Sr
Or Ra, which belongs to this class, but is not practically preferable in that it has radioactivity. A metal belonging to the alkaline earth element has an ionic radius that easily causes a perovskite crystal structure.

In the present invention, B in the general formula is one kind of metal selected from titanium group elements, that is, one of Ti, Zr and Hf, and their chemical properties are similar to each other.

In the present invention, M in the general formula is an iron group,
A metal selected from the group consisting of copper and platinum group metals, that is, Fe, Co or Ni, or Cu, Ag or Au, or Ru, Rh, Pd, Os, Ir or Pt; Chemical properties are similar to each other.

In the present invention, M represents B in the crystal lattice.
Are substituted, and the replacement fraction is indicated by x. Therefore, 0 <x <1, and if x = 0 or x = 1, sufficient denitration performance cannot be obtained.

The perovskite structure of the present invention is as follows:
The basic crystal structure is perovskite (perovskite,
It means a type of crystal structure belonging to the cubic system possessed by the compound of the formula ABX ₃ represented by CaTiO ₃ ).
However, in the present invention, a crystal structure in which the crystal lattice has some distortion due to the atomic radius of the metal that partially or totally replaces Ca or Ti, a constituent metal or oxygen is present in a slightly excessive or defective state. The above names are used as generic names of perovskite-type structures, including those of the perovskite type.

[0021] In general, NO is decomposed into N ₂ and O ₂ directly, there is a tendency that the catalyst surface is covered by O ₂ in the O ₂ or in the exhaust gas generated by the decomposition, the perovskite type oxide Such coating is relatively unlikely to occur because the adsorbed oxygen is easily released.

In the case of the perovskite-type composite oxide, the oxidation-reduction reaction (r
The edox reaction) easily occurs, and the perovskite-type oxide acts so that the oxidation-reduction reaction proceeds rapidly and constantly.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The supported catalyst of the present invention has a catalytic activity
Metal oxides as active ingredients, regardless of the preparation method
Has at least one composition represented by general formula AB_1-XM
_XO_{3 + -Z} An active ingredient comprising a transition metal composite oxide represented by
A is Sr, B is Ti, M
Is particularly preferably Fe.

The transition metal composite oxide prepared so that the composition of the active ingredient is represented by the above general formula is often obtained as a mixture of oxides having various crystal structures in practice, but at least one type of oxide is generally used. Is preferably an oxide having a perovskite structure in the above general meaning. X-ray diffraction (hereinafter abbreviated as XRD) peak has at least a perovskite peak, and a peak in which a peak derived from an oxide other than the perovskite is mixed also has an activity. Single-phase perovskites are particularly active. However, even if only the crystal structure has a perovskite structure, the object of the present invention cannot be achieved unless the composition is a composite oxide corresponding to the general formula.

According to the study of the present inventors, A is Sr, B is Ti, and SrTiO 2 corresponding to x = 0 in the above general formula.
_It has been found that _{3 + -Z and} SrFeO _{3 + -Z} , in which A is Sr, M is Fe, and x = 1, have a perovskite structure. The composite oxide of the present invention represented by the general formula has a structure in which a part of the Ti site of the perovskite oxide is substituted with Fe, and has a perovskite structure by controlling firing and other preparation conditions. be able to.

Generally, the catalytically active component of the present invention is obtained by adding an additive such as malic acid to a heated solution of a water-soluble metal salt such as a nitrate or an alcohol-soluble metal salt such as a halide. (Rotary atomizer) or mist state using a spray drier, for example, thermal decomposition by passing through a heating space such as in an electric furnace, and firing the obtained powder at a high temperature of 600 ° C to 1000 ° C Can be prepared.

The thus prepared catalytically active component is
It may be used as it is or in the form of a pellet or extrusion with a suitable molding aid such as a binder, or may be extruded into a honeycomb or the like. improves.

As the carrier, a basic metal oxide is particularly preferred. In particular, magnesia (MgO) or light rare earth (cesium group) oxide or heavy rare earth (yttrium group) oxide, such as scandium oxide, yttrium oxide, lanthanum oxide, Cerium oxide, praseodymium oxide, neodymium oxide,
Samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, ytterbium oxide, and the like are preferable. These oxides are used as fine powder having a large specific surface area as a carrier.

There are several methods for supporting the catalytically active component on a carrier. Generally, the carrier powder is added to a solution of a salt containing a metal constituting the composite metal oxide,
An impregnation-supporting method in which a solution is evaporated to dryness and then calcined is well known.

If an alcohol solution of a metal alkoxide constituting the catalytically active component is used instead of the above-mentioned metal salt solution, the catalytic performance is further improved. Generally, a metal alkoxide is a stronger base than a metal hydroxide, and a catalyst having excellent catalytic activity and poisoning properties can be obtained by being supported on the basic oxide fine powder by a supporting method such as the impregnation supporting method. .

The firing temperature is preferably at least 600 ° C. so that the oxide has a perovskite structure. The firing temperature is preferably higher than the operating temperature in order to maintain stability and durability during use of the catalyst.
However, since the use temperature of the catalyst is wide depending on the discharge source and discharge state of the exhaust gas to be denitrated, the firing temperature of the catalyst cannot be limited unconditionally.

If baking is performed at a temperature higher than a predetermined temperature at which a perovskite structure is generated, the perovskite structure hardly changes. However, the transition metal present in the crystal defect inside the crystal moves to the surface during the sintering due to solid phase diffusion or the like, so that the composition of the catalyst surface slightly changes. Therefore, the activity may vary depending on the firing temperature, and if it exceeds 1000 ° C., it is generally difficult to obtain a material having high activity. In practice, it is necessary to experimentally select the optimum firing temperature according to the state of the exhaust gas.

The catalyst of the present invention directly decomposes nitrogen oxides in exhaust gas without adding a reducing agent such as ammonia or hydrocarbon to the exhaust gas. In the absence of oxygen, of course,
Even when the exhaust gas contains about 10% by volume of oxygen, nitrogen oxides in the exhaust gas can be efficiently removed by directly contacting the exhaust gas with the catalyst of the present invention. Also, when the exhaust gas contains not only oxygen but also water vapor, nitrogen oxides can be efficiently removed.

The contact between the cracking catalyst and the exhaust gas is carried out by utilizing a fixed bed flow type reactor such as a packed bed type or a tray type well known in the art, or an advantage that the catalyst of the present invention has high activity per unit weight. And a fluidized bed reactor. In addition, various practical forms can be adopted according to the type and scale of the discharge source, and the present invention is not limited to the type of the denitration reactor as an embodiment of the contact.

The contact temperature between the catalyst of the present invention and the exhaust gas is wide, preferably from 200 ° C. to 900 ° C. For example, the processing temperature of factory exhaust gas with a vanadium-titanium catalyst is 300 ° C.
-400 ° C, exhaust gas processing temperature of gasoline engine etc. is 4
While it is a relatively narrow range of 00 ° C to 450 ° C,
It is characterized in that the operating temperature of the catalyst of the present invention in the denitration treatment of nitrogen oxides is wide from a low temperature to a high temperature.

The present invention will be described in more detail with reference to Examples, but it should not be construed that the present invention is limited thereto. Here, all the percentages indicating the gas composition are% by volume.
And the percentages indicating the compositions of the catalyst, the raw materials, and the intermediates are all percentages by weight. The cracking activity of the catalyst, expressed as conversion to N ₂ NO, the calculated by Equation 1.

[0037]

Decomposition rate = 2 [N ₂ ] out / [NO] in where [N ₂ ] out is the N ₂ concentration of the gas at the outlet of the reactor [NO] in is the NO concentration of the gas at the inlet of the reactor

[Example 1]Preparation example 1 of catalyst  Titanium butoxide Ti (OC₄H₉)₄, Iron Isopro
Poxide Fe (OC₃ H₅)₃, And strontium
Sopropoxide Sr (OC₃H₅O)₂With solvent 1-
Dissolved in methoxy-2-propanol at a concentration of 0.5M
Prepared at a ratio of 0.8: 0.2: 1 in equivalent ratio,
Additives were added and mixed at room temperature. Theoretical amount of catalytically active component
SrTi_0.8Fe_0.2O₃(Hereinafter abbreviated as STFO)
Of the above solution containing 10 parts by weight of magnesia M
gO fine powder (Ube Materials Co., Ltd.
Powder grade 100, average particle size 1.0-1.4 μm, B
ET method specific surface area 120-168m²/ G) 90 parts by weight
Stir and mix, 500 from room temperature at a rate of 100 ° C / hr.
Evaporate the alcohol while raising the temperature to
Was. The obtained powder is calcined at 500 ° C. for 1 hour,
It was baked at 50 ° C. for 5 hours. By XRD, this powder is
It was confirmed that it had a lobskite-type crystal structure. Next
500 kgf / cm³Isotropic compression with compression force
The resulting pellets are pulverized and classified to a particle size of 0.31
mm-0.71mm granules, the theoretical value of MgO
Bearing 10 wt% alkoxide method STFO
The light catalyst was obtained. The specific surface area of this granule is determined by the BET method.
N at liquid nitrogen temperature₂Measured from the amount of adsorption, 120-16
0m₂/ G.

[0039]Preparation example 2 of catalyst  Using the same alcohol solution as in Preparation Example 1 above, the type of carrier
To Sm₂O₃, Gd₂ O₃, Dy₂O₃, Y₂O₃, Y
b₂O₃, Tb₄O₇, Er₂O₃, Ho₂ O₃(what
Remo, Shin-Etsu Chemical Co., Ltd., Shin-Etsu Rare Earth BB Thailand
, Large specific surface area particles)
Impregnated and supported by the catalyst of the present invention shown in lines 2-9 of Table 1.
A rare earth oxide-supported alkoxide method STFO was prepared.
Was.

[0040]Preparation example 3 of catalyst  Strontium nitrate dihydrate SrCl₂・ 2H₂O, nitric acid
Iron hexahydrate FeCl₃・ 6H₂O, titanium trichloride TiCl
₃Of each 0.4 M ethanol solution in an equivalent ratio of 1: 0.2:
Prepare at a ratio of 0.8, add the additives and mix at room temperature
Was. The amount of the above solution containing 10 parts by weight of the theoretical amount of STFO
, 90 parts by weight of the same MgO as in Preparation Example 1 was added and stirred.
The mixture was mixed, and impregnated and supported in the same manner as in Preparation Example 1.
MgO supported nitrate method STF which is the catalyst of the present invention shown in the row
O was prepared.

[0041]Evaluation of decomposition activity 1  Preparation Example 1 in a cylindrical packed-bed reactor having an inner diameter of 10 mm,
5.0 g of the catalyst obtained in 2 or 3 was charged, and the outer wall of the reactor was filled.
While heating with electric heat to keep the temperature of the catalyst layer at 800 ° C,
He gas containing 1% NO (ie, no oxygen present)
Lower) is the contact time W / F = 3.0 g · sec / cm³, W
/F=1.5, W / F = 0.6, and W / F = 0.3
The flow rate was N for the outlet gas for each catalyst
₂The concentration is measured with a gas chromatograph analyzer and
NO to N by 1₂Calculated as the conversion rate to
It is shown in column 1-10, column A. W / F is the catalytically active component
Represents the catalytic activity per unit weight of
And is calculated by Equation 2.

[0042]

W / F = weight of catalytically active component (g) / flow rate of gas flowing into the reactor (cm ³ / sec) = [g] [sec] / [c
m ³ ]

[0043]Evaluation of decomposition activity 2  Using the catalyst obtained in Catalyst Preparation Example 1, 2 or 3,
The gas to be added is composed of NO and O in the content shown in Table 2 in He.₂Or some
Ih H₂Mixed gas containing O (that is, evaluation in the presence of oxygen)
And the same as Evaluation 1 above, except that W / F was 1.5.
The decomposition activity was examined in the same manner as described above, and the results were shown in columns B, C, and E of Table 1.
Indicated.

[Embodiment 2]Preparation Example 4 of Catalyst  The same mixed solution as that obtained in the above catalyst preparation example 3 was heated at 350 ° C.
To the rotary sprayer while heating, and spray amount of 100cm
³/ Min at 120 ° C from the nozzle adjusted to
Spray into a nitrogen stream with a prevalence below the explosion limit to form a mist
In an electric furnace maintained at 350 ° C.
Powder collected by a cyclone provided at the bottom of the furnace
I got the end. This raw material powder is heated at 650 ° C. in air for 1 hour.
Calcined for an hour, then calcined at 850 ° C for 5 hours to remove nitrate
Obtain powder of catalytically active component corresponding to STFO as raw material
Was. 90 parts by weight of Mg as a carrier is added to 10 parts by weight of this powder.
O fine powder in an appropriate amount of 1-methoxy-2-propanol
After stirring and mixing, the alcohol is evaporated to dryness and solidified.
500 kgf / cm³Isotropic compression with compression force
The resulting pellets are pulverized and classified to a particle size of 0.3
As 1mm-0.71mm granules, MgO 10w
The catalyst of the present invention carrying t% of sprayed STFO was obtained.
Was.

[0045]Evaluation of decomposition activity 3  In the same manner as in Example 1 except that the catalyst obtained in Catalyst Preparation Example 4 was used.
Then, the decomposition activity was examined, and the results are shown in Table 1, line 11.

[Comparative Example 1] Except for using alumina Al ₂ O ₃ (a specific surface area of 285 m ² / g by BET method), which is a kind of solid acid, as a carrier, exactly the same as Catalyst Preparation Example 1 To prepare a catalyst having a particle size of 0.31 mm-0.
As a 71 mm granule, a catalyst for comparison was prepared by impregnating and supporting 10 wt% of an alkoxide STFO in Al ₂ O ₃ . This was used to evaluate the decomposition activity in the same manner as in Example 1, and the results are shown in Table 1, line 12. There is a clear difference in NO decomposition activity as compared with the catalyst of the present invention using a basic metal oxide as a carrier.

Comparative Example 2 A specific surface area of 4.9 m ² / g was obtained in the same manner as in Example 2 except that 0.4 M aqueous solutions of La nitrate, Sr nitrate, and Co nitrate were used. Known perovskite-type metal oxide La _0.8 S
r _0.2 CoO ₃ with those (hereinafter LSCO abbreviated) supported on MgO in the same manner as in Example 2, performed activity evaluated in the same manner as in Example 1. The results are also shown in line 13 in Table 1 Was. Compared to the catalyst of the present invention, there is a marked difference in activity even in the absence of mild contact conditions of oxygen.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

The catalyst of the present invention can directly decompose nitrogen oxides in exhaust gas without adding a reducing agent such as ammonia or hydrocarbon to the exhaust gas. Therefore,
Eliminating the running cost of using a reducing agent and equipment such as a reducing agent addition control device is economical.

In particular, even when the exhaust gas contains about 10% by volume of oxygen, the poisoning of the catalyst by oxygen is remarkably light as compared with the conventionally known direct cracking catalyst, and nitrogen oxides Has a high decomposition rate. Therefore, NO in the exhaust gas is removed without previously removing oxygen from the exhaust gas or by directly contacting the exhaust gas having a high oxygen content discharged from an engine or the like having a high air-fuel ratio with the catalyst of the present invention. can do.

In addition, even when the exhaust gas contains not only oxygen but also water vapor, nitrogen oxide in the exhaust gas can be efficiently removed by directly contacting the catalyst of the present invention. Cu-zeolite catalyst, which is a conventionally known direct cracking catalyst, is poisoned by steam and deteriorates,
Unless the exhaust gas has been dried by dehumidification in advance, it cannot be brought into contact with this catalyst. In addition, conventionally known L
The SCO catalyst also showed only a slight denitration performance in the presence of water vapor. However, since the catalyst of the present invention is not poisoned by steam, it is suitable for directly denitration treatment of exhaust gas containing steam without previously dehumidifying.

In the method for decomposing and removing nitrogen oxides according to the present invention, a catalyst which can be brought into contact at a high temperature without adding a reducing agent to exhaust gas in which oxygen and water vapor coexist is used, and this catalyst is deteriorated by water vapor. Absent. Therefore, the exhaust gas treatment apparatus to which the method for decomposing and removing nitrogen oxides of the present invention is applied can be configured to be extremely compact, has high practical value, and is likely to be applied to a wide range of applications.

 ──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 000196680 Seibu Gas Co., Ltd. 1-17-1 Chiyo, Hakata-ku, Fukuoka, Fukuoka (72) Inventor Hiroshi Uchida 3-2-15 Azamino Aoba-ku, Yokohama-shi, Kanagawa- 106 (72) Inventor Isamu Yasuda 1-12-4-311 Kita, Kuki City, Saitama Prefecture (72) Inventor Taiji Yokoi 4-13-6, Midoridai, Kashiwa City, Chiba Prefecture (72) Inventor Osamu Okada Onodai, Osaka Sayama, Osaka 4-17-7 (72) Inventor Terumitsu Tsunomoto 1260-3 Kido, Shiga-cho, Shiga-gun, Shiga Prefecture (72) Inventor Toshiro Nakayama 3-2-10-404 Itami, Itami-shi, Hyogo (72) Inventor Tomoe Kurusu Kyoto (32) Inventor Hirofumi Otsuka 4-23 Takezono-cho, Ashiya-shi, Hyogo (72) Inventor Yasuhisa Nakamura 2-86 Gunmizu-cho, Mizuho-ku, Nagoya-shi, Aichi Prefecture Xin Rui East -4 (72) Inventor Hideyuki Ishikawa 356, Niimura-cho Tsuji, Nishio-shi, Aichi (72) Inventor Hideki Kimura 3-2-41-1006, Arato, Chuo-ku, Fukuoka, Fukuoka F-term (reference) 4G069 AA03 BA06A BA06B BA06C BA27C BB06A BC08A BC12A BC12B BC12C BC38A BC40C BC41C BC50A BC50B BC50C BC65A BC66A BC66B BC66C BC69A BD02A BD12C BE06C CA10 CA13 EC23 FB77

Claims (7)

[Claims] 1. A least one composition formula of the metal composite oxide is a catalytically active component AB _1-X M _X O
_{3 + -X} (where A is one kind of metal selected from alkaline earth elements, B is one kind of metal selected from titanium group elements, M is one kind selected from iron group, copper group or platinum group element)
0 <x <1, z is the number of oxygen defects or excess oxygen in the metal oxide at normal temperature and atmospheric pressure), and at least one of the metal composite oxides has a perovskite crystal structure. And a nitrogen oxide decomposition catalyst supported on a basic metal oxide. 2. The decomposition catalyst according to claim 1, wherein the basic metal oxide is magnesia or a rare earth oxide. 3. The composition of at least one of the metal composite oxides as the catalytically active component is SrTi _1-X Fe
The cracking catalyst according to claim 1, wherein the catalyst is represented by _X O ₃ (where 0 <x <1). 4. The method according to claim 1, wherein the preparation of the catalytically active component is carried out using an alkoxide of a metal constituting the metal composite oxide. 5. The method of claim 1, 2, 3 or 4 wherein the nitrogen oxide is produced at a temperature of 200 ° C. to 900 ° C. in the absence of a reducing agent.
A method for removing nitrogen oxides by direct decomposition, comprising contacting the decomposition catalyst with the decomposition catalyst in the absence of oxygen. 6. The method of claim 1, 2, 3 or 4 wherein the nitrogen oxide is heated at a temperature of 200 ° C. to 900 ° C. in the absence of a reducing agent.
A method for removing nitrogen oxides by direct decomposition, wherein the method is brought into contact with the decomposition catalyst described in the presence of oxygen. 7. The method of claim 1, 2, 3 or 4 wherein the nitrogen oxide is heated at a temperature of 200 ° C. to 900 ° C. in the absence of a reducing agent.
A method for removing nitrogen oxides by direct decomposition, comprising bringing the decomposition catalyst into contact with the decomposition catalyst in the presence of oxygen and water vapor.