JPH10235206A - Denitration catalyst, preparation thereof and denitration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a denitration catalyst superior in removal efficiency of NOx , its preparing method and a denitration method using the denitration catalyst. SOLUTION: This denitration catalyst comprises titanium oxide as a first component, and vanadium oxide and/or tungsten oxide as a second component, and has fine pores consisting of at least two fine pore groups of the fine pores having the vertex of the peak of the pore size distribution in a range of 0.01 to 0.05μm and the fine pores having the vertex of the peak of the pore size distribution in a range of >=0.1 and <=0.8μm, and when peak intensity of the pore size distribution of the fine pore group having the vertex of the peak of the pore size distribution in a range of 0.01 to 0.05μm is defined as 1, the peak intensity in the pore size distribution of the fine pore group having the vertex of the peak of the pore size distribution in a range of >=0.1 and <=0.8μm is >=0.4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a denitration catalyst, that is, a catalyst for removing nitrogen oxides (NOx), a method for preparing a denitration catalyst suitable for preparing this catalyst, and nitrogen oxides contained in exhaust gas using the denitration catalyst. And a method for reducing and removing the same.

[0002]

2. Description of the Related Art As a method of removing nitrogen oxides from exhaust gas which has been put into practical use at present, nitrogen oxides in the exhaust gas are catalytically reduced on a denitration catalyst using a solid reducing agent such as ammonia or urea, and harmless. The selective catalytic reduction (SCR) method, which decomposes into nitrogen and water, is common. In recent years, as the environmental pollution caused by nitrogen oxides, as typified by acid rain, has become more serious worldwide, it has been required to improve the efficiency of the denitration technology.

[0003] However, nitrogen oxides in exhaust gas and ammonia used as a reducing agent are generally lean, and it is difficult to obtain high nitrogen oxide removal performance with a conventional denitration catalyst due to problems such as gas diffusion on the catalyst. It was difficult.

[0004] For example, Japanese Patent Publication Nos. 4-42327 and 1-14088 disclose that a metal oxide such as vanadium or molybdenum is added to solated metatitanic acid, mixed, and then fired to obtain a fired titanium oxide product. Although production methods are disclosed, the denitration catalysts obtained by these methods never have sufficient nitrogen oxide removal performance.

JP-A-63-185448 discloses a denitration catalyst containing titanium and a base metal such as vanadium, tungsten and molybdenum and having a pore size distribution having two peaks. This denitration catalyst also has insufficient nitrogen oxide removal performance, and there is a strong demand for the development of a denitration catalyst having higher nitrogen oxide removal performance.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide excellent nitrogen oxide removal performance (hereinafter referred to as "denitration performance").
A denitration catalyst suitable for reducing and removing nitrogen oxides in exhaust gas, a method for preparing a denitration catalyst suitable for preparing this denitration catalyst,
It is another object of the present invention to provide a method for reducing and removing nitrogen oxides in exhaust gas by using the denitration catalyst in the presence of a reducing substance such as ammonia.

[0007]

The present inventors have found that among the denitration catalysts containing titanium oxide and vanadium oxide and / or tungsten oxide, those having a specific pore size distribution are extremely high. Having denitration performance,
Also, knowing that this denitration catalyst can be efficiently prepared by using a specific easily decomposable substance during its preparation,
Based on this finding, the present invention has been completed.

That is, the present invention relates to a denitration catalyst containing titanium oxide as a first component and vanadium oxide and / or tungsten oxide as a second component,
(1) At least a group of pores having peaks of pore size distribution in the range of 0.01 to 0.05 μm and a group of pores having peaks of pore size distribution in the range of 0.1 μm to less than 0.8 μm. When the peak intensity of the pore size distribution of the pore group having pores composed of two pore groups and (2) having the peak of the peak of the pore size distribution in the range of 0.01 to 0.05 μm is defined as 1, A denitration catalyst characterized in that the peak intensity of the pore size distribution of a group of pores having a peak of the pore size distribution in the range of 0.1 μm or more and less than 0.8 μm is 0.4 or more.

In the present invention, the average particle diameter is 5 to 100.
A denitration catalyst characterized in that an easily decomposable substance having a thermal decomposition temperature of 0 μm, a thermal decomposition temperature of 100 to 700 ° C., and a calorific value at the time of decomposition of 50 kcal / g or less is present in a catalyst precursor, which is calcined and removed. Preparation method of

[0010] The present invention is also a denitration method for reducing and removing nitrogen oxides by bringing a nitrogen oxide-containing exhaust gas into contact with the denitration catalyst.

The “peak intensity of the pore size distribution” of the present invention means:
As shown in FIG. 1, in the differential pore volume distribution diagram by the mercury intrusion method, it means the peak height of the differential pore volume distribution. Further, as shown in FIG. 1, the “peak half width of the pore size distribution” means the peak width of the differential pore volume distribution at half the peak intensity. Therefore, the higher the peak intensity and the smaller the peak half width, the sharper the differential pore volume distribution is.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The denitration catalyst of the present invention contains titanium oxide as a first component and vanadium oxide and / or tungsten oxide as a second component.
The ratio of the second component to the first component (second component / first component) is generally 0.1 to 25% by weight, preferably 1 to 15% by weight. In particular, the second component is a denitration catalyst B
4.8 × 10 ^{-7 to} 2.2 × per unit surface area by ET method
Those containing at a rate of 10 ⁻⁵ mol / m ² are preferred.

The characteristics of the denitration catalyst of the present invention are (1) 0.0
A group of pores having a peak of the peak of the pore size distribution in the range of 1 to 0.05 μm (hereinafter sometimes referred to as “first pore group”).
And a pore group having at least two pore groups of a pore group having a peak of a pore diameter distribution peak in a range of 0.1 μm or more and less than 0.8 μm (hereinafter, also referred to as “second pore group”). And (2) when the peak intensity of the pore size distribution of the pore group having the peak of the pore size distribution in the range of 0.01 to 0.05 μm is set to 1, the value is 0.1 μm or more and less than 0.8 μm. The peak intensity of the pore size distribution of the pore group having the peak of the peak of the pore size distribution in the range (hereinafter, also referred to as “peak intensity ratio”) is 0.4 or more.

That is, the denitration catalyst of the present invention is shown in FIGS.
As shown in the figure, at least 0.01 to 0.05 μm and at least 0.1 μm to less than 0.8 μm each have two substantially independent pore size distribution peaks, and the first pore group The peak intensity of the second group of pores with respect to the peak intensity of No. is 0.4 or more. The denitration catalyst of the present invention may be one in which the pore size distribution peak has a shoulder as long as the above requirements (1) and (2) are satisfied, but the pore size distribution of each pore group is narrow and the pore size is substantially It is preferable that the particles are uniformly uniform.

The peaks of the pore size distribution peaks of the first and second pore groups are 0.01 to 0.05 μm and 0.1, respectively.
If it is not in the range of not less than μm and less than 0.8 μm, sufficient denitration activity cannot be obtained. Further, the peaks of the peaks of the pore size distribution of the first and second pore groups are each 0.01 to
If the peak intensity ratio defined in the above requirement (2) is smaller than 0.4 even in the range of 0.05 μm and 0.1 μm or more and less than 0.8 μm, the desired denitration catalyst having sufficiently high denitration performance can be obtained. I can't get it. The higher the peak intensity ratio, the more effective. However, if the peak intensity ratio is too high, the catalyst intensity may decrease. In this case, the peak intensity ratio is preferably set to 2 or less.

In the denitration catalyst of the present invention, it is preferable that the pore size distribution of the second pore group is narrow and sharp. Specifically, the half-width of the pore size distribution peak of the second pore group is 0.3 μm or less. Is preferred. By setting the half width to 0.3 μm or less, usually 0.01 to 0.3 μm, the denitration performance is improved and the catalyst strength is also increased.

The total pore volume of the denitration catalyst of the present invention measured by a mercury intrusion method is preferably in the range of 0.2 to 0.6 cc / g. The pore volume occupied by the first pore group is in the range of 10 to 60% of the total pore volume, and the pore volume occupied by the second pore group is in the range of 10 to 60% of the total pore volume. Good.
The pore volume occupied by the first and second pore groups means the total amount of the volume occupied by pores in each pore diameter range.

The average particle diameter of the denitration catalyst of the present invention is 0.00
It is good to be in the range of 1 to 100 μm, preferably 0.01 to 100 μm. The specific surface area of the denitration catalyst of the present invention measured by the BET method is 30 to 250 m ² / g, preferably 4 to 250 m ² / g.
It is preferably in the range of 0 to 200 m ² / g.

Among the denitration catalysts of the present invention, a denitration catalyst containing titanium oxide as a first component and vanadium oxide and / or tungsten oxide as a second component, wherein (1) 0.01 to 0 A pore group having a peak of the peak of the pore size distribution in the range of 0.05 μm and 0.1 μm to 0.1 μm;
A pore group having at least two pore groups with a pore group having a peak of a pore diameter distribution peak in a range of less than 8 μm,
And (2) when the peak intensity of the pore size distribution of the pore group having a peak of the pore size distribution in the range of 0.01 to 0.05 μm is set to 1, the pore size distribution is in the range of 0.1 μm or more and less than 0.8 μm. The peak intensity of the pore size distribution of the pore group having the peak apex is 0.4 or more, and the pore size distribution of the pore group having the peak apex of the pore size distribution in the range of 0.1 μm or more and less than 0.8 μm. Peak half width is 0.3 μm or less,
The total pore volume by the mercury intrusion method is 0.2 to 0.6 cc /
g, the pore volume occupied by the first and second pore groups is 10 to 60% and 10 to 60%, respectively, of the total pore volume, and the first component of vanadium oxide and / or tungsten oxide as the second component is Preferably, the ratio (second component / first component) to titanium oxide as a component is 0.1 to 25% by weight.

In particular, in the above preferred denitration catalyst, the number of moles of vanadium oxide and / or tungsten oxide per unit surface area of the catalyst determined by the BET method is 4.8 × 1.
Those having a ratio of 0 ^{−7 to} 2.2 × 10 ⁻⁵ mol / m ² are preferable.

The shape of the denitration catalyst of the present invention is not particularly limited, and may be a plate, a corrugated plate, a net, a honeycomb, a column, or the like.
It may be used in a desired shape such as a cylindrical shape, or a desired shape such as a plate, a corrugated plate, a net, a honeycomb, a column, or a cylinder made of alumina, silica, cordierite, titania, stainless steel, or the like. May be supported on a carrier.

The method for preparing the denitration catalyst of the present invention is not limited. In addition to a molding aid generally used for preparing this type of catalyst, it has an average particle size of 5 to 1000 μm and a thermal decomposition temperature of 100 to 700. ℃ and the calorific value during decomposition is 50k
It can be suitably prepared by a method in which a readily decomposable substance having a cal / g or less is present in the catalyst precursor, and this is calcined and removed.

Representative examples of the easily decomposable substances include acetal resins, acrylic resins, methacrylic resins, phenolic resins, benzoguanamine resins, and unsaturated polyester resins. The amount added is preferably 0.1 to 30% by weight of the catalyst precursor. If the amount is too large, the mechanical strength of the denitration catalyst decreases. When the calorific value of the easily decomposable substance exceeds 50 kcal / g, the calorific value at the time of calcination increases, the specific surface area of the denitration catalyst decreases, and sintering of the active component is caused. If the thermal decomposition temperature exceeds 700 ° C., unburned easily decomposable substances may remain after the catalyst is calcined.

As the supply material of the titanium oxide, any of inorganic and organic compounds can be used in addition to titanium oxide, as long as it produces a titanium oxide by firing. For example, inorganic titanium compounds such as titanium tetrachloride and titanium sulfate, and organic titanium compounds such as titanium oxalate and tetraisopropyl titanate can be used. In addition to the respective oxides, any of inorganic and organic compounds can be used as a raw material of the vanadium oxide and the tungsten oxide as long as the oxides are generated by firing. For example, a hydroxide, an ammonium salt, an oxalate, a halide, a sulfate, a nitrate, or the like containing each metal can be used.

Hereinafter, as typical preparation methods, methods A to
C will be described, but the easily decomposable substance may be added at an appropriate time so that a necessary amount of the catalyst precursor before calcination is present.

Method A is a so-called coprecipitation method in which a soluble titanium compound, for example, titanium tetrachloride and a soluble tungsten compound, for example, ammonium metatungstate are dissolved in water to form an acidic aqueous solution containing titanium and tungsten. I do. Next, the temperature of the aqueous solution was set to 60 ° C.
Hereinafter, while maintaining the temperature preferably in the range of 0 to 50 ° C., the final pH of the aqueous ammonia is 5 to 8, preferably 5 to 7,
And coprecipitate so as to be less than the range. 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 precipitate. The final pH means the pH of the precipitate slurry or gel at the time when the precipitation operation is completed.

When the temperature in the above-mentioned precipitation operation exceeds 60 ° C., the activity of the denitration catalyst obtained decreases. Also, the final p
When H is lower than 5, the activity of the obtained denitration catalyst is reduced, and when it is more than 8, the activity of the denitration catalyst is reduced, and re-dissolution of tungsten also occurs. The titanium-tungsten precipitate obtained by the above-mentioned precipitation operation is separated from the precipitate slurry, washed well, dried, and then calcined to obtain a titanium-tungsten oxide. The above-mentioned separation, washing, drying and calcination can be performed under the conditions generally used for the preparation of this kind of oxide, and the weight ratio of titanium oxide / tungsten oxide is 10/1 to 3/1. ,
Preferably 20/1 to 4/1 is 300 to 700
When heated and baked at a temperature of 350C to 600C, a titanium-tungsten oxide having excellent durability can be obtained.

Method B is a method in which vanadium oxide and / or tungsten oxide is supported on titanium oxide. For example, a powder or slurry of vanadium and / or tungsten or a solution of salts of vanadium and / or tungsten is applied to a powder or slurry of titanium oxide. Or a titanium-vanadium and / or tungsten oxide can be obtained by impregnating a titanium oxide compact with a solution of vanadium and / or tungsten salts and supporting it.
The firing conditions and the like are the same as those in the method A.

Method C is a method in which vanadium oxide and / or tungsten oxide is supported on titanium oxide which has previously supported tungsten oxide, or on a dense mixture of titanium oxide and tungsten oxide. Specifically, a method of adding a salt powder of vanadium oxide and / or tungsten oxide or a solution of the salt thereof to a coprecipitated titanium-tungsten oxide powder or slurry prepared in the same manner as the above method A, A solution of a salt of tungsten is added to a titanium oxide sol obtained by thermally hydrolyzing a solution of titanium, titanium tetrachloride, or the like, and then titanium water obtained by precipitation by adding aqueous ammonia.
A method of adding vanadium oxide and / or a salt powder of a tungsten oxide or a solution of a salt thereof to a tungsten oxide powder or a slurry, or vanadium and / or a vanadium and / or a titanium-tungsten oxide formed body obtained by these methods. A method of impregnating with a solution of a salt of tungsten is exemplified. The firing conditions and the like are the same as those in the method A.

The denitration catalyst obtained by the above method C has excellent denitration performance. Although the reason is not clear, it is considered that the tungsten oxide dispersed on the titanium oxide contributes to the decomposition of the nitrogen oxide and further improves the activity of other active species. From this viewpoint, it is preferable that the titanium oxide supporting the tungsten oxide is an intimate mixture of the titanium oxide and the tungsten oxide in which the tungsten oxide is highly dispersed because the catalytic activity is high. The dense mixture of titanium oxide and tungsten oxide as used herein means that the titanium oxide and tungsten oxide are highly mixed, and the titanium oxide and tungsten oxide are tungsten oxide in the X-ray diffraction. Is characterized in that a peak derived from is substantially not observed.

Of the above methods A to C, method C is preferably used. That is, after supporting tungsten oxide on titanium oxide, a method for supporting vanadium oxide and / or tungsten oxide, and after preparing an intimate mixture of titanium oxide and tungsten oxide,
A method of supporting vanadium oxide and / or tungsten oxide on this mixture is preferably used.

The denitration catalyst of the present invention has excellent activity for decomposing nitrogen oxides discharged from boilers, heating furnaces, gas turbines, diesel engines and various industrial processes, and is suitably used for treating exhaust gases containing these nitrogen oxides. Can be

The denitration method of the present invention comprises contacting the denitration catalyst of the present invention with exhaust gas in the presence of a reducing agent such as ammonia.
It consists of reducing and removing nitrogen oxides in the exhaust gas. The conditions at this time are not particularly limited, and the reaction can be carried out under conditions generally used for this type of reaction. Specifically, it may be appropriately determined in consideration of the type and properties of the exhaust gas, the required nitrogen oxide decomposition rate, and the like.

The space velocity of the exhaust gas is usually 100
１００100,000 Hr ⁻¹ , preferably 200 to 50
000 Hr ^-1 (STP). If it is less than 100 Hr ⁻¹ , the processing equipment becomes too large and inefficient, while
If it exceeds 0000Hr ⁻¹ , the decomposition efficiency is reduced.

[0035]

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

Example 1 1.4 kg of ammonium metavanadate, 1.7 kg of oxalic acid and 0.4 kg of monoethanolamine were added to 20 kg of commercially available titanium oxide powder (DT-51 (trade name), manufactured by Rhone Poulin) in water. A solution dissolved in 5 L (liter) was added, and 1 kg of a phenolic resin (Bellpearl (trade name), manufactured by Kanebo Co., Ltd.) and 0.5 kg of starch as a molding aid were added, mixed, and kneaded with a kneader. After that, the outer shape is 80 mm square and the aperture is 4.0 m with an extrusion molding machine.
m, a thickness of 1.0 mm, and a length of 500 mm. Next, after drying at 80 ° C., it was calcined at 450 ° C. for 5 hours in an air atmosphere to obtain a catalyst A.

The phenol resin has an average particle size of 20 μm.
m, thermal decomposition temperature 450 ° C, calorific value during decomposition 8 kcal /
g.

The composition of the catalyst A is V ₂ O ₅ : TiO ₂ = 5:
95 (weight ratio). When the pore size distribution of the catalyst A was measured by a mercury intrusion porosimeter, the peak intensity ratio was 0.77, and the peak half width of the pore size distribution of the second pore group was 0.13 μm. The total pore volume is 0.35c
c / g, and the pore volumes of the first and second pore groups were 44% and 48% of the total pore volume, respectively. Also,
The BET surface area was 68 m ² / g, and the content of vanadium oxide (V ₂ O ₅ ) per unit surface area of the catalyst was 3.8.
× 10 ⁻⁶ mol / m ² . The pore size distribution of catalyst A is shown in FIG.

Example 2 180 L of a titanium sulfate solution (100 g / L as titanium dioxide) obtained from a process for producing titanium oxide by a sulfuric acid method
Was heated to 100 ° C., and 5 L of a 10% aqueous solution of ammonium paratungstate in methylamine (400 g / L as tungsten trioxide) was added to the obtained titanium oxide sol. While stirring, ammonia water was added until the pH became 8, and the mixture was left to stand and aged for 2 hours. The titanium-tungsten precipitate slurry thus obtained was filtered, and the obtained titanium-tungsten precipitate was washed with water, dried at 100 ° C. for 12 hours, and calcined at a temperature of 500 ° C. for 3 hours to obtain a titanium-tungsten precipitate. -Tungsten oxide powder (titanium oxide / tungsten oxide = 90/1)
0 (weight ratio)). According to X-ray diffraction of this oxide, no peak derived from tungsten oxide was observed.

This titanium-tungsten oxide powder 20
A solution prepared by dissolving 1.4 kg of ammonium metavanadate, 1.7 kg of oxalic acid and 0.4 kg of monoethanolamine in 5 L of water was added to the resulting solution, and 1 kg of a phenol resin (Bellpearl (trade name), manufactured by Kanebo Co., Ltd.) was added. 0.5 kg of starch as a molding aid was added, mixed and kneaded with a kneader, and then extruded with an extruder to an outer shape of 80 mm square.
It was formed into a honeycomb shape having an aperture of 4.0 mm, a wall thickness of 1.0 mm, and a length of 500 mm. Next, after drying at 80 ° C., 4
It was calcined at 50 ° C. for 5 hours in an air atmosphere to obtain a catalyst B.

The composition of the catalyst B is V ₂ O ₅ : WO ₃ : TiO ₂
= 5: 10: 85 (weight ratio). When the pore size distribution of the catalyst B was measured by a mercury intrusion porosimeter, the peak intensity ratio was 1.05, and the peak half width of the pore size distribution of the second pore group was 0.20 μm. The total pore volume was 0.49 cc / g, and the pore volumes of the first and second pore groups were 43% and 51% of the total pore volume, respectively. The BET surface area of the catalyst B was 71 m ² / g, and vanadium oxide and tungsten oxide (W
The content of O ₃ ) per unit surface area of the catalyst was 3.7 × 10 ⁻⁶ mol / m ² and 5.7 × 10 ⁻⁶ mo, respectively.
1 / m ² . The pore size distribution of catalyst B is shown in FIG.

Example 3 12.8 kg of titanium tetrachloride (TiCl ₄ ) was gradually added to 80 L of water under ice-cooling and stirring to dissolve, and an aqueous solution of ammonium metatungstate (containing 50% by weight as tungsten oxide) was added to the aqueous solution. ) 1.2 kg. While keeping the obtained aqueous solution at a temperature of about 30 ° C., ammonia water was added thereto until the pH reached 6, with sufficient stirring, and the mixture was left to ripen for 2 hours. The titanium-tungsten precipitate slurry thus obtained was filtered, and the obtained titanium-tungsten precipitate was washed with water and heated at 150 ° C.
And then calcined at 600 ° C for 5 hours.
A titanium-tungsten oxide having a tungsten oxide content of 90/10 (weight ratio) was obtained. A solution prepared by dissolving 1.4 kg of ammonium metavanadate, 1.7 kg of oxalic acid and 0.4 kg of monoethanolamine in 5 L of water was added to 20 kg of the coprecipitated titanium-tungsten oxide powder thus obtained. 3. Add 1 kg of resin (Bellpearl (trade name), manufactured by Kanebo Co., Ltd.) and 0.5 kg of starch as a molding aid, mix and knead with a kneader, and then use an extruder to form an outer shape of 80 mm square and 4 openings. 0m
m, a thickness of 1.0 mm, and a length of 500 mm. Next, after drying at 80 ° C., it was calcined at 450 ° C. for 5 hours in an air atmosphere to obtain a catalyst C.

The composition of the catalyst C is V ₂ O ₅ : WO ₃ : TiO ₂
= 5: 10: 85 (weight ratio). When the pore size distribution of the catalyst C was measured by a mercury intrusion porosimeter, the peak intensity ratio was 0.59, and the peak half width of the pore size distribution of the second pore group was 0.29 μm. The total pore volume was 0.37 cc / g, and the pore volumes of the first and second pore groups were 57% and 37% of the total pore volume, respectively. The BET surface area was 78 m ² / g, and the content of vanadium oxide and tungsten oxide per unit surface area of the catalyst was 3.3 × 10 ⁻⁶ mol.
/ M ² and 5.2 × 10 ⁻⁶ mol / m ² . FIG. 4 shows the pore size distribution of the catalyst C.

Comparative Example 1 The titanium-tungsten oxide powder used in Example 2 was further pulverized by an air current pulverizer, a phenol resin was not added at the time of kneading, and a deaeration layer was provided in the former stage of the molding machine. Except that the air in the kneaded material was removed, the outer shape was 80 m according to Example 2.
m square, aperture 4.0 mm, wall thickness 1.0 mm, length 500
mm of a honeycomb catalyst D was prepared.

When the pore size distribution of the catalyst D was measured by a mercury intrusion porosimeter, it was 0.01 to 0.05 μm.
Only the first group of pores having a pore size in the range
There was no second pore group having a pore diameter in the range of 1 μm or more and less than 0.8 μm. The total pore volume of catalyst D is 0.25c
c / g. The BET surface area is 65 m ² / g, and the vanadium oxide and the tungsten oxide
The content per unit surface area of the catalyst was 4.0 × 10 4
^-6 mol / m ² and 6.3 × 10 ^-6 mol / m ² . The pore size distribution of catalyst D is shown in FIG.

Example 4 Using the catalysts A to D obtained in Examples 1 to 3 and Comparative Example 1, a denitration activity test was carried out under the following conditions.

Test conditions NOx: 70 ppm, NH ₃ : 70 ppm, O ₂ : 13
%, H ₂ O: 7%, N ₂ : balance Gas temperature: 190 to 330 ° C., space velocity (STP): 1
0000 to 20000 Hr ^-1 and the denitration rate were determined according to the following equation.

Denitration rate (%) = [(reactor inlet NOx concentration) − (reactor outlet NOx concentration)] ÷ (reactor inlet NO
x concentration) × 100 The relationship between gas temperature and denitration rate is shown in Table 1 (space velocity:
16000Hr- ¹ ).

[0049]

[Table 1]

Table 2 shows the relationship between the space velocity and the denitration rate (gas temperature: 230 ° C.).

[0051]

[Table 2]

Example 5 A denitration activity test was carried out using the catalyst B obtained in Example 2 under the following conditions.

Test conditions NOx: 200 ppm, NH ₃ : 200 ppm, SO ₂ :
800 ppm, O ₂ : 12%, H ₂ O: 10%, N ₂ : balance Gas temperature: 380 ° C., Space velocity: 5000 Hr ^{−1 The} denitration ratio was determined in the same manner as in Example 4, and it was 99%.

[0054]

The denitration catalyst of the present invention has excellent denitration performance, and is particularly preferably used for treating various exhaust gases having a low nitrogen oxide content to reduce and remove the nitrogen oxide.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a peak intensity and a peak half width of a pore size distribution.

FIG. 2 shows the pore size distribution of catalyst A obtained in Example 1.

FIG. 3 shows a pore size distribution of catalyst B obtained in Example 2.

FIG. 4 shows the pore size distribution of catalyst C obtained in Example 3.

FIG. 5 shows the pore size distribution of catalyst D obtained in Comparative Example 1.

Claims (5)

[Claims] 1. A denitration catalyst containing titanium oxide as a first component and vanadium oxide and / or tungsten oxide as a second component, wherein (1) 0.01 to
Consisting of at least two pore groups: a pore group having a peak of the pore size distribution in the range of 0.05 μm and a pore group having the peak of the pore size distribution in the range of 0.1 μm to less than 0.8 μm. (2) 0.01-0.
When the peak intensity of the pore size distribution of the pore group having the peak of the pore size distribution in the range of 05 μm is set to 1, 0.1 μm
A denitration catalyst, wherein the peak intensity of the pore size distribution of a group of pores having a peak of the pore size distribution in the range of not more than 0.8 μm is 0.4 or more. 2. The denitration catalyst according to claim 1, wherein the peak half width of the pore size distribution of the pore group having a peak of the pore size distribution in the range of 0.1 μm or more and less than 0.8 μm is 0.3 μm or less. 3. The catalyst according to claim 1, wherein the number of moles of vanadium oxide and / or tungsten oxide per unit surface area of the catalyst is 4.8.
× 10 ^-7 to 2.2 claim 1 wherein × 10 ^-5 mol / m ²
Or the denitration catalyst according to 2. 4. An average particle size of 5 to 1000 μm, a thermal decomposition temperature of 100 to 700 ° C., and a calorific value during decomposition of 50 k.
A method for preparing a denitration catalyst, characterized in that a readily decomposable substance having a cal / g or less is present in a catalyst precursor, and this is calcined and removed. 5. A denitration method for reducing and removing nitrogen oxides by contacting a nitrogen oxide-containing exhaust gas with the denitration catalyst according to claim 1.