JPH08257409A - Catalyst for removing nitrogen oxide and removing method of nitrogen oxide using the same - Google Patents

Abstract

PURPOSE: To provide a NOx removing catalyst catalytically reducing NOx in an exhaust gas by using a reducing agent such as ammonia. CONSTITUTION: The catalyst is produced by burning a precipitate obtained by precipitating an aq. soln. containing an aqueous medium-soluble titanium compd. tungsten compd. and an acid type zeolite having SiO2 /Al2 O3 molar ratio of at least 8 and/or a Ce ion exchange type zeolite.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention removes nitrogen oxides from exhaust gas containing nitrogen oxides (hereinafter abbreviated as "denitration").
For details, the nitrogen oxide (hereinafter referred to as “NOx”) contained in high temperature exhaust gas discharged from various industrial processes other than gas engines, gas turbines, boilers, diesel engines, etc. Further, the present invention relates to a denitration catalyst suitable for catalytic reduction using a solid reducing agent such as urea, melamine, cyanuric acid, ammonium carbonate, and ammonium hydrogencarbonate, a method for producing a denitration catalyst, and a denitration method using the catalyst.

The "denitration catalyst" of the present invention means N in exhaust gas.
It means a catalyst for catalytically reducing Ox using the above reducing agent to convert it into harmless nitrogen and water.

[0003]

2. Description of the Related Art At present, as a method for removing NOx in exhaust gas, NOx can be selectively removed even in exhaust gas containing a high concentration of oxygen, and a small amount of reducing agent is used, which is economical. The catalytic reduction method using ammonia as a reducing agent has become the mainstream.

As catalysts used in this catalytic reduction method, many catalysts in which alumina, silica, zeolite, titanium oxide and the like are combined with oxides of vanadium, copper, tungsten, molybdenum, iron and the like have been proposed so far. There is. Among them, the catalyst containing titanium oxide as the main component is not widely influenced by sulfur oxides (SOx) in the exhaust gas and has a low ability to oxidize SO ₂ to SO ₃ in the exhaust gas, so that it is widely used today. It has been put to practical use. The reaction temperature is usually about 250 to 400 ° C.

As a method for preparing the above-mentioned catalyst containing titanium oxide as a main component, for example, an aqueous solution of a soluble tungsten compound is added to a titanium hydroxide precipitate gel obtained by adding aqueous ammonia to an aqueous solution of a soluble titanium compound, After mixing, molding, drying and calcination, or in the case of molding, a part or all of the catalyst mixture is preliminarily decomposed by heating to form a mixture of oxides, which is then molded and dried and calcined (Japanese Patent Publication No. 52-35342). Gazette).

Ammonia water is added to the hydrated titanium oxide slurry to adjust the pH, and then a tungsten compound is added, mixed, dried and fired to obtain a titanium-tungsten binary oxide. There is also known a method of adding an acid type zeolite or a Ce ion exchange type zeolite to a system oxide and molding and drying (JP-A-5-123577).

On the other hand, some gas turbine exhaust gases and diesel engine exhaust gases have an exhaust gas temperature of over 400 ° C., and in order to remove NOx in such high-temperature exhaust gas, they have excellent activity in a relatively wide temperature range. A denitration catalyst showing

However, the catalyst containing titanium oxide and tungsten oxide as main components, which is obtained by the method described in Japanese Patent Publication No. 52-35342, has a temperature of 400 ° C., as shown in Example 1 of the publication. Shows the highest catalytic activity, and at 500 ° C., it is already in the temperature range where the denitration rate decreases. In order to increase the denitration rate, it is conceivable to increase the molar ratio of ammonia to NOx, but under the condition where ammonia is excessively present, not only the consumption amount of ammonia increases and economic efficiency decreases, but also There is a risk that a large amount of ammonia will leak into the exhaust gas when the load changes.

The catalyst obtained by the method described in JP-A-5-123577 shows higher initial activity than the catalyst obtained by the conventional method when used at low temperature, but when used at high temperature. Remained a problem with durability.

That is, the conventionally known denitration catalyst is 400 ° C.
In the case of catalytic reduction of NOx in high temperature exhaust gas that exceeds the limit, the oxidation (or decomposition) reaction of ammonia as a reducing agent is NO.
Since it occurs at the same time as the reduction of x, the denitrification rate is low, and in order to obtain a high denitrification rate, it is necessary to increase the molar ratio of ammonia to NOx, which increases the consumption of ammonia and reduces the economic efficiency. However, there was a problem with durability at high temperatures, and it was never satisfactory as a practical catalyst.

[0011]

The object of the present invention is to exhibit a high denitration activity in a wide temperature range, particularly in a high temperature range of more than 400 ° C., and even under the condition of a low ammonia / NOx molar ratio, and to have excellent durability. Denitrification catalyst,
It is intended to provide a method for producing the catalyst and a denitration method using the catalyst.

[0012]

DISCLOSURE OF THE INVENTION The inventors of the present invention have proposed a catalyst containing titanium, tungsten and zeolite by using a catalyst containing a catalyst component obtained by a predetermined preparation method of titanium, tungsten and zeolite. They have found that a high denitration rate occurs even at high temperatures, and have completed the present invention. That is, the present invention is specified as described below.

(1) Titanium compound and soluble tungsten compound soluble in aqueous medium, and SiO ₂ / Al ₂ O
Nitrogen oxide containing a catalyst component obtained by precipitating an aqueous liquid containing an acid type zeolite and / or a Ce ion exchange type zeolite having a ₃ (molar ratio) of 8 or more and calcining the resulting precipitate. Removal catalyst.

(2) Titanium compound and soluble tungsten compound soluble in aqueous medium, and SiO ₂ / Al ₂ O
₃ An aqueous solution containing an acid type zeolite and / or Ce ion-exchanged zeolite is (molar ratio) is 8 or more, containing a catalyst component obtained by calcining the precipitate is obtained not neutralize and precipitate with a basic substance A method for producing a nitrogen oxide removing catalyst, comprising:

(3) A method for removing nitrogen oxides, which comprises removing the nitrogen oxides from the exhaust gas containing the nitrogen oxides in the presence of ammonia by using the catalyst as described in 1 above. The present invention will be described in detail below.

The type of the soluble titanium compound used in the present invention is not particularly limited as long as it is soluble in an aqueous medium, and inorganic titanium compounds such as titanium tetrachloride and titanium sulfate, and titanium oxalate and tetraisopropyl. Organic titanium compounds such as titanates can be used. The type of the soluble tungsten compound is not particularly limited, and ammonium metatungstate, ammonium paratungstate, etc. can be used. Regarding the ratio of the soluble titanium compound and the soluble tungsten compound, the weight ratio of titanium oxide / tungsten oxide (TiO ₂ / WO ₃ , hereinafter the same) is 20/1 to 1/1 when dried and calcined. In particular, it is preferable to set it in the range of 20/1 to 1.5 / 1 since the activity of the denitration catalyst obtained will be high.

The acid-type zeolite according to the present invention (hereinafter also referred to as H-type zeolite) is one in which the counterion of the zeolite is replaced with hydrogen, and among the acid-type zeolites, SiO ₂ / Al ₂ O is used. Zeolites having a ₃ (molar ratio) of 8 or more, preferably 10 or more. SiO ₂
This is because when / Al ₂ O ₃ (molar ratio) is less than 8, denitration efficiency is low, heat resistance is poor, and structural stability is low when ion-exchanged with acid-type zeolite. The acid type zeolite having a SiO ₂ / Al ₂ O ₃ (molar ratio) of 8 or more is specifically mordenite, ZSM-
5, Y type zeolite or acid type zeolite such as ferrierite.

The Ce ion-exchange type zeolite according to the present invention is a zeolite having a SiO ₂ / Al ₂ O ₃ (molar ratio) of 8 or more, and this zeolite is appropriately stirred with an aqueous Ce solution. , Can be obtained by heating. Specifically, zeolite SiO such as mordenite, ZSM-5, Y-type zeolite or ferrierite.
₂ / Al ₂ O ₃ (molar ratio) to the zeolite of 8 or more,
Water-soluble compounds of Ce, for example, ceric nitrate, ceric nitrate, ceric sulfate, ceric sulfate,
It is obtained by adding an aqueous liquid of an inorganic compound such as cerium carbonate or an organic compound such as ceric acetate and heating. The Ce content in the Ce ion-exchanged zeolite is preferably 0.5 to 30% by weight in terms of cerium oxide with respect to the H-type zeolite before exchange. If it is out of this range, the denitration efficiency is lowered, which is not preferable.

The content of the catalytic zeolite according to the present invention is
The acid type zeolite and C in a weight ratio to titanium oxide.
e Total of 10-1 to 1/10 of ion-exchange type zeolite
The range is preferable. If the amount of zeolite component is less than 10/1, the denitration efficiency at high temperature is low and not preferable, and if the amount of zeolite component is more than 1/10, the moldability of the catalyst is lowered, and 450 ° C.
This is because the denitration efficiency in the temperature range below becomes low, which is not preferable.

It is preferable that the acid type zeolite and the Ce ion exchange type zeolite do not contain alkali metal or alkaline earth metal as much as possible. This is because the structural stability of zeolite decreases when an alkali metal or the like is contained.

Water is usually used as the aqueous medium.

As a precipitation method in the preparation of the catalyst according to the present invention, an aqueous solution containing the acid type zeolite and / or Ce ion exchange type zeolite, a water-soluble titanium compound and a water-soluble tungsten compound is subjected to a thermal hydrolysis method and a heating method. Although a conventionally known method such as a decomposition method or a neutralization method using a basic compound can be used, a method in which a basic compound is added to cause precipitation is preferably used, and titanium and tungsten are more preferred. preferable. The type of the basic compound is not particularly limited, and for example, ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate or the like can be used. Of these, ammonia or an aqueous solution thereof (ammonia water) is preferably used from the viewpoint of the washability and handleability of the precipitate slurry.

The present invention will be described in detail below by taking a method of precipitation using water as an aqueous medium and acid-type zeolite or aqueous ammonia as a basic compound.

First, a soluble titanium compound such as titanium tetrachloride and a soluble tungsten compound such as ammonium metatungstate are dissolved in water to obtain an acidic titanium-tungsten-containing aqueous solution. The H-type zeolite powder is added to this solution and the temperature of this solution is maintained at 60 ° C. or lower, preferably in the range of 50 to 0 ° C., while stirring.
Then, aqueous ammonia is added so that the final pH is in the range of 5 to 8, preferably 5 or more and less than 7, for precipitation. When the aqueous solution of the tungsten compound is basic, the aqueous solution containing tungsten is added to the aqueous solution containing titanium at the same time as the aqueous ammonia to cause precipitation. In addition, "final p
"H" means the pH of the precipitate slurry or gel at the time when the precipitation operation is completed.

If the temperature in the precipitation operation exceeds 60 ° C., the activity of the denitration catalyst obtained becomes low, which is not preferable. If the final pH is lower than 5, the activity of the denitration catalyst obtained will be low, and if it is higher than 8, the activity will be low, and in addition, redissolution of tungsten will occur, which is not preferable.

The titanium-tungsten-zeolite precipitate obtained by the above precipitation operation can be separated from the precipitate slurry, washed well, dried and then calcined to obtain the catalyst component of the present invention. The above separation, washing, drying and calcination can be carried out under the conditions generally used for the preparation of this type of catalyst, but the weight ratio of titanium oxide / tungsten oxide is 20/1 to 1/1, especially 20. / 1 to 1.5 / 1 and a titanium oxide / zeolite weight ratio of 10/1 to 1/10 is 400 to 750 ° C,
In particular, heating and firing in the range of 450 to 700 ° C. is preferable because the catalyst component has excellent durability. Also, regarding the calcination treatment, (a) a method in which the titanium-tungsten-zeolite precipitate is dried and then calcined and then molded, (b) a method in which the titanium-tungsten-zeolite precipitate is molded and then calcined, or (c) Any of the above methods (a) and (b) may be used. In the case of the method (b), the heat treatment in the latter stage may cause shrinkage of the molded body, change of the physical properties of the catalyst, and the like. Therefore, the method (a) or the method (c) is preferable, and also in the case of the method (c). It is preferable to carry out the firing of the latter stage at the same temperature as the firing of the former stage or at a temperature lower than that.

Although the reason why the denitration catalyst according to the present invention exhibits excellent denitration activity and excellent durability is not clear, it is possible to obtain the denitration activity by itself by performing precipitation under the above specific conditions. It is presumed that it is caused by highly dispersed titanium oxide and tungsten oxide on the zeolite.

The denitration catalyst according to the present invention can also be used in combination with a composite oxide such as alumina, silica, zirconia, titania or titania-silica.

The denitration catalyst according to the present invention can be used as it is by integrally molding it or by supporting it on a carrier. As the carrier, alumina, silica, composite oxides such as silica-alumina, titania-silica, bentonite, diatomaceous earth, silicon carbide, titania, zirconia, magnesia, cordierite, mullite, pumice, inorganic fibers, or stainless steel or the like. A metal plate or net can be used. The supporting method is not particularly limited, and for example, a method of impregnating granular silicon carbide with the slurry of the denitration catalyst and supporting it, a method of coating the stainless corrugated plate with the slurry of the denitration catalyst and supporting it can be used.

The shape of the denitration catalyst (including carrier-supported catalyst) according to the present invention is not particularly limited, and it may be honeycomb, plate, cylinder, ribbon, pipe, donut, lattice, column, or wave. It may be plate-shaped or granular.

When the surface area of the catalyst according to the present invention is too low, the denitration activity is low, and when it is too high, ammonia decomposition is promoted. Therefore, the catalyst has a surface area of 10 to 120 m ² / g, preferably 15 to 100 m ² .
m ² / g is selected, and if the pore volume is too low, the activity will be low, and if it is too high, the catalyst strength will decrease, so 0.1 to 0.6.
cc / g, preferably 0.2 to 0.5 cc / g is selected.

There is no particular limitation on the composition of the exhaust gas treated with the NOx removal catalyst of the present invention, and the NOx removal catalyst of the present invention can be used for the treatment of various exhaust gases containing NOx. For example, SOx 0 to 3000 ppm, oxygen 1 to 20
Used for the treatment of exhaust gas containing about 10% by volume of carbon dioxide, 1 to 15% by volume of carbon dioxide, 5 to 15% by volume of water vapor, 0.001 to ³⁰ g / Nm ³ of soot and NOx (mainly NO) of 20 to 10000 ppm. Furthermore, the denitration catalyst of the present invention can also be used for treatment of special exhaust gas such as NOx-containing exhaust gas containing no SOx and NOx-containing exhaust gas containing halogen compounds.

The treatment conditions of the exhaust gas using the denitration catalyst of the present invention cannot be unconditionally specified because it depends on the type and properties of the exhaust gas, the required denitration rate, etc., but in the case of implementation, it should be appropriately determined in consideration of these conditions. Good.

As the reducing agent, ammonia or urea, which decomposes to produce ammonia, melamine, cyanuric acid, ammonium carbonate, ammonium hydrogencarbonate or the like is used. Ammonia and urea are preferably used from the viewpoint of safety in terms of handling and cost. The form of injection of the reducing agent into the exhaust gas is not particularly limited, but from the viewpoint of dispersibility and handleability of the reducing agent in the exhaust gas, ammonia gas, liquid ammonia, aqueous ammonia, urea aqueous solution, ammonium carbonate aqueous solution, ammonium hydrogencarbonate aqueous solution or the like gas or It is preferably injected as a liquid. When a reducing agent that decomposes to produce ammonia is used, the amount of the reducing agent added is determined by the amount of ammonia produced from the reducing agent. For example, urea is 1/2 mol of ammonia and melamine is 1/3 mol of injection. It becomes the amount.

The amount of ammonia used as a reducing agent is determined by considering the denitration rate, the amount of leaked ammonia, etc.
The NOx (NO conversion) molar ratio can be appropriately selected within a range of 0.3 / 1 to 3/1, preferably 0.3 / 1 to 1.5 / 1. In particular, in the case of the denitration catalyst of the present invention, a high denitration rate can be obtained even when the ammonia / NOx (NO conversion) molar ratio is in the range of 1.5 / 1 or less, and NOx can be efficiently decomposed and removed. For example, in the case of treating exhaust gas from a boiler, since most of NOx contained in this exhaust gas is NO, it is particularly preferable that the ammonia / NOx (NO conversion) molar ratio is around 1, but the required denitrification rate and leak Considering the amount of ammonia and the like, it is appropriately selected within the range of about 2/1 or less.

The reaction temperature is 400 to 700 ° C., preferably 450 to 650 ° C. The space velocity is usually 1000 to 100,000 Hr ~ ¹ , especially 3000
It is preferably in the range of -80,000 Hr- ¹ . The pressure is not particularly limited, but usually 0.01 to 10 kg / cm ²
Is preferred.

The type of reactor used for treating the exhaust gas is not particularly limited, and ordinary fixed bed, moving bed, fluidized bed, etc. reactors can be used.

[0038]

EXAMPLES The present invention will be described in more detail below with reference to examples.

(Example 1) 11.4 kg of titanium tetrachloride (TiCl4) in 80 liters of water (hereinafter referred to as L)
Is gradually added dropwise under ice cooling and stirring to dissolve, and an aqueous solution of ammonium metatungstate manufactured by Japan Inorganic Chemical Industry Co., Ltd. (containing 50% by weight as tungsten oxide) is added to this aqueous solution.
2.4 kg was added. While maintaining this aqueous solution at a temperature of about 30 ° C., a commercially available synthetic H-type zeolite (mordenite, S
The molar ratio of iO ₂ / Al ₂ O ₃ is 15.4 / 1) 4.8 Kg
Was added, and ammonia water was adjusted to pH 6 while stirring well.
Was added and the mixture was allowed to stand for aging for 2 hours.

The titanium-tungsten-zeolite precipitate slurry thus obtained was filtered, and the titanium-tungsten-zeolite precipitate obtained was washed with water to obtain 1
Titanium oxide / tungsten oxide = 4/1 (weight) and titanium oxide / zeolite = 1/1 (weight) titanium-after being dried at 50 ° C. for 10 hours and calcined at 600 ° C. for 5 hours.
A tungsten oxide-zeolite was obtained.

Using a kneader, 1 kg of the above-mentioned titanium-tungsten oxide powder was kneaded well while adding an appropriate amount of water, and then molded into pellets having a diameter of 4 mm and a length of 5 mm by an extruder. Next, the pellets were dried at 60 ° C. and then calcined at 600 ° C. for 5 hours under air flow to obtain a titanium oxide / tungsten oxide = 4/1 (weight) catalyst (A).
Was prepared.

(Example 2) As a titanium source, an aqueous sulfuric acid solution of titanyl sulfate (250 g / L in terms of TiO2) was used.
2 L was taken, and 80 L of water was added thereto. While keeping this aqueous solution at a temperature of about 30 ° C, a commercially available synthetic H-type zeolite (Z
The molar ratio of SM-5, SiO ₂ / Al ₂ O ₃ is 54.5 /
1) 4.8 Kg was added, 0.54 kg of monoethanolamine and 2.7 L of water were mixed with good stirring, and 1.35 kg of ammonium paratungstate was added, and an aqueous solution and ammonia water were gradually added dropwise. Then, aqueous ammonia was added until the pH reached 6, and the mixture was allowed to stand for aging for 2 hours. Thereafter, a catalyst (B) having the same composition was prepared in the same manner as in Example 1.

(Examples 3 to 6) Catalysts (C) to (F) were prepared in the same manner as in Example 1 except that the weight ratios of titanium oxide / tungsten oxide and titanium oxide / zeolite were changed. Prepared. The catalyst composition is shown in Table 1.

[0044]

[Table 1]

(Example 7) In Example 1, instead of mordenite, the following Ce ion-exchange type zeolite, that is, 3 kg of cerium nitrate cerium was dissolved in 30 liters of water, and 5 kg of the zeolite used in Example 2 was added. Add 9
After performing ion exchange with heating at 0 to 100 ° C. for 3 hours with stirring, filtration, washing, drying at 150 ° C. for 1 hour, and then 60
A catalyst (G) was obtained in the same manner as in Example 1 except that the zeolite was calcined at 0 ° C. for 5 hours and 3% by weight of CeO ₂ was used as the zeolite.

(Comparative Example 1) In Example 1, titanium-
Instead of tungsten oxide, commercially available anatase-type titanium oxide powder as a titanium source (DT-manufactured by Lone Poulin)
50) Using 4.8 kg, 0.54 kg of monoethanolamine and 2.7 L of water were mixed, an aqueous solution prepared by adding 1.35 kg of ammonium paratungstate was added, and an appropriate amount of water was added with a kneader. While mixing well,
Kneaded Thereafter, a comparative catalyst (a) was prepared in the same manner as in Example 1.

Comparative Example 2 Metatitanic acid (water-insoluble compound) slurry as a titanium source was used as TiO ₂ .
8kg used, 0.54kg monoethanolamine
And 2.7 L of water are mixed, an aqueous solution obtained by adding 1.35 kg of ammonium paratungstate is added, and the mixture is kneaded while heating in a kneader.
After drying at 50 ° C. for 10 hours, it was baked at 600 ° C. for 5 hours to obtain a powder of a mixture of titanium oxide and tungsten oxide. Using a kneader, 600 g of the powder of the mixture of titanium oxide and tungsten oxide and 480 g of the same zeolite as used in Example 1 are mixed, dried at 150 ° C. for 10 hours, and calcined at 600 ° C. for 5 hours for comparison. A catalyst (b) was obtained.

(Evaluation Example 1) Examples 1 to 7 and Comparative Example 1
The denitration rate of each of the catalysts (A) to (G) and comparative catalysts (a) to (b) obtained in Examples 1 to 2 was determined by the following method.

20 ml of the catalyst was filled in a quartz reaction tube installed in an electric furnace, and a synthesis gas having the following composition was introduced into the catalyst layer under the following conditions. NOx concentration in the gas at the inlet of the reaction tube (NOx concentration at the inlet) and NO in the gas at the outlet of the reaction tube
x concentration (outlet NOx concentration) is defined by Yanagimoto Seisakusho N
It was measured with an Ox meter (ECL-77A type), and the denitration rate was calculated according to the following formula.

Denitration rate (%) = (NOx concentration at inlet−N at outlet)
Ox concentration) / (inlet NOx concentration) (× 100) Synthesis gas composition NOx: 100 ppm, O ₂ : 15%, SO ₂ : ₂₀₀ p
pm, H ₂ O: 10%, N ₂ : residual reaction conditions Gas amount: 3.33 NL / min, space velocity (SV): 1
000Hr-1, NH ₃ / NOx (NO conversion) molar ratio:
1.0, temperature: described in Table 2 The obtained results are shown in Table 2.

[0051]

[Table 2]

(Example 8) A catalyst (H) having the same composition was prepared in the same manner as in Example 1 except that the temperature at the time of precipitation was changed from about 30 ° C to 55 ° C.

Example 9 A catalyst (I) having the same composition was prepared in the same manner as in Example 1 except that the final pH at the time of precipitation was changed from 6 to 5.

(Example 10) A catalyst (J) having the same composition was prepared in the same manner as in Example 1 except that the final pH at the time of precipitation was changed from 6 to 8.

Comparative Example 3 A comparative catalyst (c) having the same composition was prepared in the same manner as in Example 1 except that the temperature during precipitation was changed from about 30 ° C. to 80 ° C.

Comparative Example 4 A comparative catalyst (d) having the same composition was prepared in the same manner as in Example 1 except that the final pH at the time of precipitation was changed from 6 to 4.

Comparative Example 5 A comparative catalyst (e) having the same composition was prepared in the same manner as in Example 1 except that the final pH at the time of precipitation was changed from 6 to 9.0.

(Evaluation Example 2) The completed catalysts (H) to (J) and the comparative catalysts (c) to (e) obtained in Examples 8 to 10 and Comparative Examples 3 to 5 were evaluated in the same manner as in Evaluation Example 1. The denitration rate was calculated. Table 3 shows the obtained results.

[0059]

[Table 3]

(Examples 11 to 14) In Example 1,
Catalysts (K) to (N) having the same composition were prepared in the same manner as in Example 1 except that the calcination temperature of the titanium-tungsten-zeolite precipitate was changed as shown in Table 4.

(Evaluation Example 3) With respect to the catalysts (K) to (N) obtained in Examples 11 to 14, the denitration rate was obtained in the same manner as in Evaluation Example 1. The results obtained are shown in Table 4.

[0062]

[Table 4]

(Evaluation Example 4) Catalysts (A), (E) obtained in Examples 1, 5, 9, 13 and Comparative Examples 2, 3
The durability of (I), (M) and comparative catalysts (b), (c) was evaluated by the following method.

Each catalyst was placed in an electric furnace adjusted to 550 ° C. under air flow and taken out after a lapse of a predetermined time. Less than,
In the same manner as in Evaluation Example 1, the denitration rate at a reaction temperature of 500 ° C. was measured. The results obtained are shown in Table 5.

[0065]

[Table 5]

[0066]

The denitration catalyst of the present invention has a wide temperature range,
In particular, it exhibits high denitration activity in a high temperature range of 400 ° C. or higher and has excellent durability. Therefore, by using the denitration catalyst of the present invention, NOx in high-temperature exhaust gas discharged from various industrial processes other than gas turbines, boilers, gas engines, diesel engines, etc. can be efficiently decomposed and removed.

The denitration catalyst of the present invention exhibits excellent denitration activity and durability even in a low ammonia / NOx molar ratio in a wide temperature range, particularly in a high temperature range of 400 ° C. or higher. Therefore, by using the denitration catalyst of the present invention, while minimizing the consumption of ammonia, that is, economically,
Moreover, NOx in the high temperature exhaust gas can be efficiently decomposed and removed without causing a problem such as a leak of ammonia.

Claims (3)

[Claims] 1. A titanium compound and a soluble tungsten compound which are soluble in an aqueous medium, and SiO ₂ / Al ₂ O.
Nitrogen oxide containing a catalyst component obtained by precipitating an aqueous liquid containing an acid type zeolite and / or a Ce ion exchange type zeolite having a ₃ (molar ratio) of 8 or more and calcining the resulting precipitate. Removal catalyst. 2. A titanium compound and a soluble tungsten compound which are soluble in an aqueous medium, and SiO ₂ / Al ₂ O.
₃ An aqueous solution containing an acid type zeolite and / or Ce ion-exchanged zeolite is (molar ratio) is 8 or more, containing a catalyst component obtained by calcining the precipitate is obtained not neutralize and precipitate with a basic substance A method for producing a nitrogen oxide removing catalyst, comprising: 3. A method for removing nitrogen oxides, wherein the exhaust gas containing nitrogen oxides is removed from the exhaust gas by using the catalyst according to claim 1 in the presence of ammonia.