JPH09192491A - Catalyst for reduction and removal of nitrogen oxide in waste combustion gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a catalyst capable of reducing and removing NOx from waste gas after dusulfurization of stack gas at a stable rate of denitration over a long time in the presence of ammonia by carrying a vanadium compd., a bromine compd., a copper compd., a compd. of lanthanum, etc., and a compd. of molybdenum, etc., on a carbonaceous material. SOLUTION: A vanadium compd., a bromine compd., a copper compd., a molybdenum or tungsten compd. and a lanthanum or cerium compd. are carried on a carbonaceus material to obtain the objective catalyst having high catalyst activity of densitration at a low temp. of about 100 deg.C, producing little nitrous oxide as a by-product and capable of stably maintaining reduction denitrating performance over a long time even at a high space velocity. When this catalyst is used for treating waste combustion gas at a low temp. freed of SOx from an apparatus for wet-desulfurizing stack gas, residual NOx can be continuously removed with a compact apparatus in an easy and smooth manner.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a catalyst for reducing and removing nitrogen oxides in combustion exhaust gas, and more particularly, to reducing nitrogen oxides from combustion exhaust gas at a relatively low temperature after wet desulfurization in the presence of ammonia. The present invention relates to a catalyst for removing and reducing nitrogen oxides in combustion exhaust gas that can be removed.

[0002]

2. Description of the Related Art In recent years, environmental pollution has become a problem on a global scale, and various measures for preventing pollution have been proposed.
Emission standards for wastewater and exhaust gas have also been reviewed and studied. Combustion exhaust gas, which is a source of air pollution, will be more strictly regulated. Sulfur oxides (SOx) and nitrogen oxides (NO
x) is included, and the technology related to flue gas treatment is how to remove these SOx and NOx. Various practical desulfurization technologies have been established for SOx, and many excellent actual equipments have already been operating and are producing results.

On the other hand, regarding NO _x , various denitration techniques have also been proposed and implemented, and the denitration technique most widely used at present is a catalyst in which vanadium oxide such as vanadium pentoxide is supported on a ceramic carrier such as titania. It is used to reduce NO _{X in} the presence of ammonia to make it harmless as nitrogen. Since this catalyst exhibits activity at a high temperature of 250 to 400 ° C., it was necessary to install a denitration device using the above catalyst after it came out of the boiler upstream of the air heater for preheating the burner combustion air. But,
In this case, acidic ammonium sulfate (NH ₄ HSO ₄ ) generated by the reaction between sulfur trioxide (SO ₃ ) generated by SO ₂ oxidation in the denitration device and ammonia added during denitration
There were many problems with the air heater, which is thought to be due to the above. Therefore, for the purpose of changing the installation of the denitration device from the upstream side of the air heater to the downstream side, the NO _x from the low temperature combustion exhaust gas at a relatively low temperature of about 130 to 150 ° C. downstream is detoxified and removed. As a catalyst for this, a method using a carbonaceous material such as activated carbon or activated coke as a catalyst has been proposed. Even in this case, when SO _X is present in the combustion exhaust gas, similarly, ammonium sulfate ((NH ₄ ) ₂ SO
₄ ) and NH ₄ HSO ₄ are generated, and there is a problem such that the catalytic activity of activated carbon is reduced.

Therefore, in recent years, a method of removing nitrogen oxides after removing sulfur oxides in exhaust gas has been tried, but exhaust gas discharged from a wet flue gas desulfurization device usually used for removing sulfur oxides has been tried. The temperature is as low as about 50 ℃,
Even if it is heated using a heater, the temperature is about 100 ° C., and even with the above-mentioned activated carbon catalyst, the reaction rate is slow and it is not practical.
Therefore, further development of a catalyst having denitration activity even at a low temperature of about 100 ° C. has been promoted, and the inventors of the present invention have filed Japanese Patent Application No. 6-1918.
In No. 27, vanadium compound, bromine compound,
We have proposed a denitration catalyst that supports copper compounds and molybdenum or tungsten compounds. This catalyst has a relatively high catalytic activity for denitration at a low temperature of about 100 ° C., has little nitrous oxide by-product which is said to significantly promote global warming, and maintains stable reduction denitration performance for a long time. It is an excellent catalyst that can.

[0005]

However, as a result of further investigations by the inventors regarding the use of the above-mentioned catalyst, etc., when the reduction treatment of nitrogen oxides at a high space velocity (SV) is performed using this catalyst, the operating time is reduced. It was found that the catalyst activity gradually decreased with the lapse of time, and the denitration rate gradually decreased compared to the initial stage of the operation. The present invention is based on the above findings and shows stable denitration for a long time from low-temperature exhaust gas containing nitrogen oxides, for example, exhaust gas after flue gas desulfurization, without lowering catalytic activity even in long-term exhaust gas treatment at high SV. It is intended to provide a catalyst capable of reducing and removing nitrogen oxides in the presence of ammonia at a high rate, and further to provide a catalyst capable of further suppressing nitrous oxide by-product. In order to achieve the above object, the inventors have further studied supported metals and the like based on the knowledge obtained in the development of the proposed denitration catalyst, and have completed the present invention.

[0006]

According to the present invention, a combustion characterized in that a carbonaceous material is loaded with a vanadium compound, a bromine compound, a copper compound, a molybdenum or tungsten compound, and a lanthanum or cerium compound. A catalyst for reducing and removing nitrogen oxides in exhaust gas is provided.

The present invention is constituted as described above, and by supporting five components of a vanadium compound, a bromine compound, a copper compound and a molybdenum or tungsten compound, and further a lanthanum or cerium compound on a carbonaceous material,
The catalyst activity of denitration at a low temperature of about 100 ° C. is high, the nitrous oxide by-product is small, and the reduction denitration performance can be stably maintained for a long time even at a high SV. By using the catalyst for reducing nitrogen oxides in combustion exhaust gas of the present invention, even in low-temperature exhaust gas of about 100 ° C. after desulfurization of combustion exhaust gas, contact treatment is performed at high SV in the presence of ammonia for a long time. Nitrogen oxides can be stably reduced and removed with a high denitration rate.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. Examples of the carbonaceous material which is the catalyst carrier used in the present invention include wood, activated carbon such as coconut shell, coal activated carbon such as coal tar pitch, activated carbon such as petroleum activated carbon such as petroleum pitch, activated coke, activated carbon fiber and the like. The above carbonaceous material may be used as long as it has a specific surface area of 10 m ² / g or more, and any one of them can be appropriately selected and used according to various usage conditions. Preferably, a specific surface area of 100m ² / g~2000m ² / g,
More preferably using activated carbon-based carbonaceous 500m ² / g~1500m ² / g. Specific surface area of carbonaceous material is 10m
If it is less than ² / g, the desired catalytic activity cannot be obtained.

In the present invention, the vanadium compound as the catalytically active component is supported on the carbonaceous material by using an oxide, inorganic acid salt or organic acid salt of any of trivalent, tetravalent and pentavalent vanadium. be able to. Usually, a product obtained by reducing ammonium metavanadate with oxalic acid or vanadyl sulfate can be suitably used. As a supporting method, any known method such as a dipping impregnation method, a spray method, a kneading method or the like can be used. Usually, an immersion impregnation method or a spray method is used. For example, the vanadium compound is dissolved in a soluble solvent such as water, the carbonaceous material is immersed in the solution, dried at room temperature to 200 ° C, and then in an inert gas stream such as nitrogen at 200 to 600 ° C. Can be calcined to obtain a vanadium-supporting carbonaceous carrier. The vanadium compound supported as described above is generally, finally, on a carrier,
It is presumed to take the form of an oxide. In the catalyst of the present invention, the supported amount of vanadium (V) is 0.5 to 15% by weight, preferably 1 to 10% by weight based on vanadium element. If it is less than 0.5% by weight, sufficient denitration performance cannot be obtained, and if it exceeds 15% by weight, the specific surface area of the carbonaceous material decreases, which is an adverse effect and is not preferable.

The bromine compound as another catalytically active component of the present invention is prepared by using an alkali metal salt such as hydrobromic acid, ammonium bromide, sodium bromide, etc., an alkaline earth metal salt such as magnesium bromide, etc. It can be supported on a carbonaceous material. Usually, hydrobromic acid or ammonium bromide is used. The carbonaceous material may be supported by any known method similar to the above vanadium compound. For example, the carbonaceous material is immersed in an aqueous solution of bromide or the like, and after impregnation, room temperature to 100 ° C.
And dried to support. After drying, if necessary, baking may be performed at 150 to 600 ° C. in an inert gas stream such as nitrogen. In the catalyst of the present invention, the amount of bromine (Br) supported is 0.1 to 20% by weight, preferably 2 to 15% by weight based on the elemental bromine.
% By weight. If it is less than 0.1% by weight, sufficient denitration performance cannot be obtained, and if it exceeds 20% by weight, no further effect can be obtained.

As the copper compound as another catalytically active component of the present invention, an oxide of monovalent or divalent copper, an inorganic acid salt or an organic acid salt is used and supported on the carbonaceous material. You can Usually, copper nitrate, copper sulfate and the like are preferably used. The carbonaceous material may be supported by any known method as in the case of the vanadium compound. In the catalyst of the present invention, the supported amount of copper (Cu) is 0.1 to 2.0, preferably 0.2 to 1.
0. If this molar ratio is less than 0.1, sufficient denitration performance cannot be obtained, while if it exceeds 2.0, no further effect can be obtained.

As a compound of lanthanum or cerium which is another catalytically active component of the present invention, a trivalent oxide, an inorganic acid salt or an organic acid salt can be used and supported on the carbonaceous material. Usually, lanthanum nitrate or cerium nitrate is preferably used. The carbonaceous material may be supported by any known method as in the case of the vanadium compound. In the catalyst of the present invention, the loading amount of lanthanum (La) or cerium (Ce) is based on the above V loading amount on an element basis.
The molar ratio is 0.1 to 2.0, preferably 0.2 to 1.0. If this molar ratio is less than 0.1, sufficient denitrification performance cannot be obtained, while if it exceeds 2.0, no further effect can be obtained.

The compound of molybdenum (Mo) and tungsten (W) which are other catalytically active components of the present invention is 2
An oxide, an inorganic acid salt, or an organic acid salt of any one of trivalent, trivalent, tetravalent, pentavalent, and hexavalent can be used to support the carbonaceous material. Usually, ammonium molybdate, ammonium metatungstate, and ammonium paratungstate are preferably used. Supporting carbonaceous materials
Any known method may be used as in the case of the vanadium compound. For example, the carbonaceous material is immersed in an aqueous solution of the compound of Mo or W, dried at room temperature to 200 ° C., and then 200 to 600 in an inert gas stream such as nitrogen. Bake at ° C. It is presumed that the Mo or W compound supported as described above generally takes the form of an oxide on the support. In the catalyst of the present invention, the supported amount of the compound of Mo or W is 0.5 or more, preferably 1 to 2 in molar ratio with respect to the supported amount of Cu. This molar ratio is 0.
If it is less than 5, the effect of suppressing the generation of nitrous oxide is low, and if it is supported in excess of 2, no further effect can be obtained.

As described above, the catalyst for reducing nitrogen oxides in combustion exhaust gas according to the present invention is preferably a vanadium compound, a bromine compound, a copper compound, a lanthanum or cerium compound, and further molybdenum or It can be formed by supporting five components of tungsten as a catalyst component. Each of the above catalyst components may be supported separately, or depending on the compound of each catalyst component used, for example, a dipping impregnation method, a mixed solution may be simultaneously supported. Further, in the case of the spray method, it is possible to carry out the loading of the respective components in sequence and to carry out the drying and firing in common to further improve the process. When loaded separately, preferably
It is preferable that the metal component such as the vanadium component, the copper component, the lanthanum or cerium component, the molybdenum or the tungsten component is loaded first, and then the bromine component is loaded.
In addition, in the spray method or the impregnation method, it is preferable to carry out the loading under a reduced pressure because the loading component can be loaded uniformly on the carbonaceous material carrier.

Further, vanadium, as a bromine compound,
It can also be supported as a salt of copper, lanthanum, cerium, molybdenum, or tungsten. In this case, the deficient amount may be separately supported in consideration of the supported amount. In this case, the method for supporting the metal bromide may be the same as the method for supporting the bromide, and the supporting order is preferably the last. The shape of the catalyst of the present invention is not particularly limited. For example, a powdery, granular, granular, spherical, cylindrical, or the like shaped body, or a honeycomb shape or the like can be appropriately selected according to the processing conditions. INDUSTRIAL APPLICABILITY The catalyst for reducing and removing nitrogen oxides in flue gas of the present invention is suitably used for flue gas in a temperature range from a low temperature of about 100 ° C. or less to about 150 ° C. after flue gas wet desulfurization, etc. Below, SV 2000
By performing contact treatment at a high space velocity of not less than 1 hour / hour, nitrogen oxides can be reduced and removed stably with a high denitration rate for a long period of time.

[0016]

EXAMPLES The present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples. Example 1 200 m of vanadium ion-containing 0.5 mol / 1 aqueous solution prepared by reducing ammonium metavanadate with oxalic acid
100 g of commercially available granular activated carbon (manufactured by Takeda Pharmaceutical Co., Ltd., trade name: Gx, diameter 4 mmφ, length 6 mm, specific surface area of about 1,200 m ² / g) was added to 1 and immersed under reduced pressure to obtain V. Was impregnated and separated by filtration. Then, the obtained V
The supported activated carbon was dried in a dryer at 100 ° C. for 12 hours, then calcined in a nitrogen stream at 450 ° C. for 5 hours and cooled to room temperature to obtain V-supported activated carbon. The V-supporting activated carbon obtained as described above was immersed in 200 ml of an ammonium molybdate aqueous solution containing 0.5 mol / 1 of molybdenum under reduced pressure, and after impregnating with Mo, in the same manner as the V-supporting above, V-Mo carrying activated carbon was obtained. The obtained V-Mo-supported activated carbon was added to a 0.25 mol / 1 lanthanum nitrate aqueous solution 20.
After dipping in 0 ml under reduced pressure to impregnate La, V-Mo-La-supported activated carbon was obtained in the same manner as in the above V and Mo support.

Next, the obtained V-Mo-La-supported activated carbon was immersed in 200 ml of a 0.25 mol / 1 copper sulfate aqueous solution under reduced pressure and separated by filtration. Obtained Cu-impregnated V-Mo
The -La-supported activated carbon was dried in a drier at 100 ° C for 12 hours, then fired at 200 ° C for 5 hours in a nitrogen stream and cooled to room temperature to obtain V-Mo-La-Cu-supported activated carbon. The obtained V-Mo-La-Cu-supported activated carbon was added in an amount of 1 mol / 1.
Immersion impregnation was carried out in 200 ml of a hydrobromic acid aqueous solution under reduced pressure, followed by separation by filtration. The hydrogen bromide-impregnated activated carbon separated by filtration was dried in a drier at 110 ° C. for 12 hours to obtain V-Mo-L.
An a-Cu-Br-supported activated carbon catalyst was obtained. Obtained VM
The o-La-Cu-Br supported activated carbon catalyst has a V loading of 2.0% by weight, a Mo loading of 3.7% by weight, a La loading of 2.8% by weight, and a Cu loading of 1.4% by weight. %, And the Br loading amount was 6.2% by weight.

V-Mo-La-Cu-B prepared above
r-supported activated carbon catalyst with inner diameter of 30 mmφ and height of 500 mm
The glass denitration reaction tube of No. 33 was filled with 33 ml to form a catalyst fixed bed. In this reaction tube, a temperature of 100 ° C.
Nitrogen oxide (NO) 500ppm, oxygen (O ₂ ) at 0 / hr
5% by volume, carbon dioxide (CO ₂ ) 12% by volume, water (H
₂ O) containing 9.5% by volume, the balance being nitrogen gas, and 500 ppm of ammonia (NH ₃ ) was added to the simulated combustion exhaust gas, and the mixture was continuously flow-treated. The treatment gas composition at each treatment time shown in Table 1 was measured by a chemiluminescence type NOx meter manufactured by Shimadzu Corporation to calculate the denitration rate. The amount of nitrous oxide (N ₂ O) produced was measured by filling a column for gas chromatography with UniBeads C (manufactured by GL Sciences). Note that the denitration rate [%] is (NOx inlet concentration-
It was calculated by (NOx outlet concentration) / NOx inlet concentration × 100. The results are shown in Table 1. In addition, the generated N _{2 in the} table
The O concentration (ppm) is an average value over the treatment time (the same applies hereinafter).

Example 2 The La loading amount of the catalyst component was adjusted to the values shown in Table 1,
The concentration of the aqueous solution was adjusted and V-Mo was prepared in the same manner as in Example 1.
A -La-Cu-Br-supported activated carbon catalyst was obtained. Using the obtained catalyst, the pseudo combustion exhaust gas was treated in the same manner as in Example 1. The results are shown in Table 1.

Example 3 V-Mo-supported activated carbon 1 prepared in the same manner as in Example 1
00 g of 0.25 mol / 1 cerium nitrate aqueous solution 20
It was immersed in 0 ml under reduced pressure to impregnate Ce, and separated by filtration. Then, the obtained Ce-impregnated V-Mo-supported activated carbon was added to 1
After drying for 12 hours in a dryer at 00 ° C, 4 in a nitrogen stream
Baking at 50 ° C for 5 hours, cooling to room temperature and then V-Mo-C
e-supported activated carbon was obtained. The obtained V-Mo-Ce-supported activated carbon was loaded with Cu and Br in the same manner as in Example 1, and V
A -Mo-Ce-Cu-Br-supported activated carbon catalyst was obtained. Using the obtained catalyst, the pseudo combustion exhaust gas was treated in the same manner as in Example 1. The results are shown in Table 1.

Example 4 100 g of V-supported activated carbon prepared in the same manner as in Example 1
Was immersed in 400 ml of an ammonium paratungstate aqueous solution containing 0.05 mol / 1 of W and then dried under reduced pressure by an evaporator, and the obtained W-impregnated V-supported activated carbon was dried in a dryer at 100 ° C. for 12 hours. After repeating this W supporting operation again, firing was performed at 450 ° C. for 5 hours in a nitrogen stream. La, Cu and Br were loaded on the obtained V-W-supported activated carbon in the same manner as in Example 1 to carry out V-W-La-.
A Cu-Br supported activated carbon catalyst was obtained. Using the obtained catalyst, the pseudo combustion exhaust gas was treated in the same manner as in Example 1. The results are shown in Table 1.

Example 5 The La loading amount of the catalyst component was adjusted to the value shown in Table 1,
The concentration of the aqueous solution was adjusted and V-W-
An La-Cu-Br supported activated carbon catalyst was obtained. Using the obtained catalyst, the pseudo combustion exhaust gas was treated in the same manner as in Example 1.
The results are shown in Table 1.

Example 6 V-W supported activated carbon 10 prepared in the same manner as in Example 4
0 g of 0.25 mol / 1 cerium nitrate aqueous solution 200
It was immersed in ml under reduced pressure to impregnate Ce, and separated by filtration. Then, the obtained Ce-impregnated VW-supported activated carbon was mixed with 10
After drying in a 0 ° C dryer for 12 hours, 45 in a nitrogen stream
The mixture was calcined at 0 ° C for 5 hours and cooled to room temperature to obtain VW-Ce-supported activated carbon. The obtained V-W-Ce-supported activated carbon was loaded with Cu and Br in the same manner as in Example 1, and V-W-
A Ce-Cu-Br supported activated carbon catalyst was obtained. Using the obtained catalyst, the pseudo combustion exhaust gas was treated in the same manner as in Example 1.
The results are shown in Table 1.

Example 7 V-Mo-supporting activated carbon 1 prepared in the same manner as in Example 1
00g, 0.17m with 0.25mol / 1 cupric bromide
It was immersed and impregnated in 200 ml of a mixed aqueous solution of ol / 1 lanthanum bromide under reduced pressure, and separated by filtration. L separated by filtration
The a-Cu-Br-impregnated V-Mo-supported activated carbon was dried in a drier at 100 ° C for 12 hours, and then at 5 ° C in a nitrogen stream at 200 ° C.
After firing for an hour, the amount of each component shown in Table 1 is V-Mo-
An La-Cu-Br supported activated carbon catalyst was obtained. Using the obtained catalyst, the pseudo combustion exhaust gas was treated in the same manner as in Example 1.
The results are shown in Table 1.

Example 8 V-W supported activated carbon 10 prepared in the same manner as in Example 4
La, Cu and Br were supported on 0 g in the same manner as in Example 7 to obtain a VW-La-Cu-Br supported activated carbon catalyst. Using the obtained catalyst, the pseudo combustion exhaust gas was treated in the same manner as in Example 1. The results are shown in Table 1.

Examples 9 to 11 Using the catalysts prepared by the methods of Examples 1, 4, and 7 in the same glass denitration reaction tube as used in Example 1, 16.
5 ml was filled, and a pseudo combustion exhaust gas having the same composition was treated at 140 ° C. and SV 10,000 / hour. The results are shown in Table 1.

[0027]

[Table 1]

Comparative Example 1 V-Mo-supporting activated carbon 1 prepared in the same manner as in Example 1
00 g, 200 ml of 0.25 mol / 1 copper sulfate aqueous solution
Was immersed in a vacuum under reduced pressure, and separated by filtration. Obtained Cu impregnation V
The —Mo-supported activated carbon was dried in a dryer at 100 ° C. for 12 hours, then fired in a nitrogen stream at 200 ° C. for 5 hours and cooled to room temperature to obtain V-Mo-Cu-supported activated carbon. The obtained V-Mo-Cu-supported activated carbon was treated with B in the same manner as in Example 1.
r-supporting was performed to obtain a V-Mo-Cu-Br-supporting activated carbon catalyst. Using the obtained catalyst, the pseudo combustion exhaust gas was treated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 2 V-W supported activated carbon prepared in the same manner as in Example 4 was added with
Cu and Br were loaded in the same manner as in Comparative Example 1, and V-
A W-Cu-Br-supported activated carbon catalyst was obtained. Using the obtained catalyst, the pseudo combustion exhaust gas was treated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 3 V-Mo-Cu-Br prepared in the same manner as in Comparative Example 1.
The simulated combustion exhaust gas was treated in the same manner as in Example 9 using the supported activated carbon catalyst. The results are shown in Table 2.

[0031]

[Table 2]

As is clear from the above Examples and Comparative Examples, V-Mo (or W) -La (or C of the present invention is used.
e) The Cu-Br supported activated carbon catalyst has a space velocity of 5000.
Even when used for denitrification treatment of combustion exhaust gas under the condition of high treatment capacity of 1 / hr / 10,000 / hr, the present inventors previously proposed V in Japanese Patent Application No. 6-191827. -Compared to the Mo-Cu-Br supported activated carbon catalyst,
It can be seen that a high denitration rate is exhibited over a long period of time, and the catalytic activity is maintained. Also, the amount of nitrous oxide by-product is 6p
It is pm or less, and further reduction is achieved as compared with the case where a V-Mo-Cu-Br-supported activated carbon catalyst is used. Conventionally, for example, the same applicant has disclosed in Japanese Patent Laid-Open No. 7-16468.
The V-Cu-Br-supported activated carbon catalyst proposed in Japanese Patent Laid-open Publication can be used even if the time during which it can be treated while maintaining the catalyst activity in the same denitration test exceeds 720 hours, and can be used for a long period of time and has durability. However, it is clear that the catalyst of the present invention has a useful life of 960 hours, which is much higher than that of the catalyst of the present invention.

[0033]

INDUSTRIAL APPLICABILITY The catalyst for reducing nitrogen oxides in flue gas according to the present invention has little nitrous oxide by-product and can stably denitrate flue gas at a relatively low temperature over a long period of time. Therefore, by using the catalyst for nitrogen oxide reduction removal of the present invention, relatively low temperature combustion exhaust gas after wet flue gas desulfurization,
With a very high space velocity, i.e. a small reactor,
Nitrogen oxide can be reduced and removed stably for a long time,
It has extremely high utility value in terms of preventing environmental pollution. Further, the present invention is applied to the treatment of low-temperature flue gas from which SOx has been removed from a wet flue gas desulfurization device that has already been implemented to remove SOx from flue gas containing SOx and NOx, which are air pollution sources. By using the catalyst for reducing and removing nitrogen oxides, it is possible to remove residual nitrogen oxides easily and smoothly in a compact device, which is industrially useful.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Naoki Sonehara 2-12-1, Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa Chiyoda Kako Construction Co., Ltd. (72) Ryuichi Kanai Chuo, Tsurumi-ku, Tsurumi-ku, Yokohama-shi, Kanagawa Chome 12-1 Chiyoda Kakoh Construction Co., Ltd. (72) Inventor Togari Shun 2-12-1 Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa Chiyoda Kakoh Construction Co., Ltd.

Claims (1)

[Claims] 1. A method for reducing nitrogen oxides in combustion exhaust gas, which comprises supporting a vanadium compound, a bromine compound, a copper compound, a lanthanum or cerium compound, and a molybdenum or tungsten compound on a carbonaceous material. catalyst.