JP2012206058A - Denitration catalyst and denitrification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove nitrogen oxide with high efficiency, and to solve a problem such as pipe corrosion by SOgeneration while removing the nitrogen oxide with high efficiency.SOLUTION: The denitration catalyst contains titanium oxide and vanadium oxide. When measuring the catalyst by X-ray photoelectron spectroscopy, a vanadium amount of the surface of the catalyst is 1.1-3.0 times the vanadium amount inside the catalyst. The denitrification method for exhaust gas uses the catalyst.

Description

  The present invention relates to a denitration catalyst and a denitration method. Particularly excellent in removal of NOx contained in exhaust gas discharged from heavy oil fired boilers and coal fired boilers, gas turbines, gas engines, diesel engines, thermal power plants, waste incinerators and various industrial processes The present invention relates to a denitration catalyst and a denitration method using the same.

  As a method for removing nitrogen oxides in exhaust gas that is currently in practical use, a selective catalyst that catalytically reduces nitrogen oxides in exhaust gas using a reducing agent such as ammonia or urea and decomposes it into nitrogen and water. The reduction method (SCR method) is common. In recent years, as environmental pollution caused by nitrogen oxides has become serious worldwide, as represented by acid rain, a high-performance catalyst has been demanded.

  As a conventional technique related to a denitration catalyst, for example, Japanese Patent Application Laid-Open No. 2004-943 discloses a honeycomb-shaped exhaust gas treatment catalyst made of titanium dioxide and / or a titanium composite oxide as a catalyst effective for removing nitrogen oxides. However, it could not be said to have sufficient processing performance.

Furthermore, SO ₂ is contained in the exhaust gas discharged from combustion furnaces, power plants, and waste incinerators that use heavy oil or coal as fuel, and when this is oxidized on the catalyst to become SO ₃ , it corrodes the piping after the catalyst. Or, SO ₃ reacts with water or ammonia in the exhaust gas to produce (NH ₄ ) HSO ₄ , which accumulates in the catalyst and lowers the catalyst performance. Therefore, in addition to being excellent in nitrogen oxide removal performance as a characteristic required for the catalyst, a low SO ₂ oxidation rate may be required at the same time, but the technique disclosed in the above publication also requires this point. It was not enough.

Japanese Patent Laid-Open No. 2004-943

An object of the present invention is to solve the above-mentioned problems of the prior art and provide a catalyst having excellent nitrogen oxide removal performance. Specifically, as a means for improving the denitration performance, it is possible to increase the content of vanadium oxide as an active component. However, this method has a limit in improving the denitration performance. Further, there is a problem that the oxidation rate of SO ₂ is increased at the same time by increasing the content of vanadium oxide.

  The present inventor has intensively studied to solve the above problems. As a result, the inventors have found that the denitration performance can be improved by making the vanadium oxide concentration on the catalyst surface higher than the vanadium oxide concentration inside the catalyst, and the invention has been completed. Furthermore, nitrogen oxides and sulfur oxides can be sufficiently treated even when sulfur oxides are contained in the exhaust gas.

  The present invention is included in exhaust gas discharged from heavy oil fired boilers, coal fired boilers, gas turbines, gas engines, diesel engines, thermal power plants, incineration facilities for treating industrial waste and municipal waste, and various industrial processes. The present invention relates to a denitration catalyst for catalytic reduction of nitrogen oxide (NOx) using a reducing agent such as ammonia or urea.

A first invention is a denitration catalyst containing titanium oxide and vanadium oxide, wherein vanadium (V2p3 / 2) measured by X-ray photoelectron spectroscopy satisfies the following condition: is there.
(1) Measuring the area of the vanadium (V2p3 / 2) peak on the catalyst surface.
(2) Measure the area of the titanium (Ti2p3 / 2) peak on the catalyst surface.
(3) the area of the resultant vanadium (V2p3 / 2) peak (1), and _{A 0} and the resulting titanium (Ti2p3 / 2) values obtained by dividing the area of the peak (2) thing.
(4) Obtaining the average value of the vanadium (V2p3 / 2) peak area at a depth of 40 nm to 100 nm from the surface of the catalyst.
(5) Obtain an average value of the area of the titanium (Ti2p3 / 2) peak at a depth of 40 nm to 100 nm from the surface of the catalyst.
(6) Let A be the value obtained by dividing the area of the vanadium (V2p3 / 2) peak obtained in (4) by the area of the titanium (Ti2p3 / 2) peak obtained in (5). .
(7) A ₀ is 1.1 to 3.0 times A.

  Preferably, the catalyst further contains at least one selected from the group consisting of tungsten oxide and molybdenum oxide. The titanium oxide is a composite oxide and / or mixed oxide of titanium and at least one element selected from the group consisting of silicon, aluminum, zirconium, tungsten, and molybdenum, and the titanium oxide includes at least two kinds. More preferably, it is a mixture of the above titanium oxides, and the titanium oxide is a mixture of a mixed oxide of titanium oxide and tungsten oxide and a composite oxide of titanium and silicon.

  The second invention is a denitration method characterized by treating exhaust gas containing nitrogen oxides using the catalyst.

  A third invention is a denitration method characterized by treating exhaust gas containing nitrogen oxides and sulfur oxides using the catalyst.

By using the catalyst of the present invention, nitrogen oxides can be removed with high efficiency. Further, while removing nitrogen oxides with high efficiency, problems such as pipe corrosion due to SO ₃ generation can be solved.

  Hereinafter, although the exhaust gas treatment catalyst according to the present invention will be described in detail, the present invention can be carried out as appropriate without departing from the spirit of the present invention.

A first invention is a denitration catalyst containing titanium oxide and vanadium oxide, wherein vanadium (V2p3 / 2) measured by X-ray photoelectron spectroscopy satisfies the following condition: is there.
A denitration catalyst comprising titanium oxide and vanadium oxide, wherein vanadium (V2p3 / 2) obtained by measuring the catalyst by X-ray photoelectron spectroscopy satisfies the following conditions.
(1) Measuring the area of the vanadium (V2p3 / 2) peak on the catalyst surface.
(2) Measure the area of the titanium (Ti2p3 / 2) peak on the catalyst surface.
(3) the area of the resultant vanadium (V2p3 / 2) peak (1), and _{A 0} and the resulting titanium (Ti2p3 / 2) values obtained by dividing the area of the peak (2) thing.
(4) Obtaining the average value of the vanadium (V2p3 / 2) peak area at a depth of 40 nm to 100 nm from the surface of the catalyst.
(5) Obtain an average value of the area of the titanium (Ti2p3 / 2) peak at a depth of 40 nm to 100 nm from the surface of the catalyst.
(6) Let A be the value obtained by dividing the area of the vanadium (V2p3 / 2) peak obtained in (4) by the area of the titanium (Ti2p3 / 2) peak obtained in (5). .
(7) A ₀ is 1.1 to 3.0 times A.
The above procedure will be specifically described in numerical order.

-Vanadium concentration measurement-
In the present invention, it is most important that the vanadium oxide concentration on the catalyst surface is higher than the vanadium oxide concentration inside the catalyst. Concentration distribution of the vanadium oxide from the catalyst surface to the inside of the catalyst can be measured by X-ray photoelectron spectroscopy (hereinafter referred to as XPS). In the analysis by XPS, information in a very fine range from the surface of the measurement sample to several nm is usually obtained, so that the vanadium oxide concentration on the catalyst surface can be quantified. In order to use XPS, which is mainly used for qualitative analysis, for quantitative analysis, a standard substance existing at a constant concentration in the data is required. In this measurement, titanium present uniformly in the catalyst was used as a standard substance, and the concentration of vanadium present between the materials was compared by comparing the amount of vanadium between the materials.

<Measurement of vanadium concentration on catalyst surface>
The amount of vanadium was determined from the peak area of V2p3 / 2 measured by XPS. By the procedure described above, the vanadium concentration in the depth direction from the catalyst surface can be measured. This will be specifically described below.

(1) It is necessary to measure the area of the vanadium (V2p3 / 2) peak on the catalyst surface. In this method, first, the catalyst material is measured by XPS, vanadium (V2p3 / 2) is measured, and the area of the peak shown in the chart is measured. However, the peak has a different value depending on the measurement conditions, and it is impossible to directly compare the concentrations between the materials. Therefore, (2) the area of the titanium (Ti2p3 / 2) peak that exists uniformly in the catalyst is measured, and the vanadium (V2p3 / 2) peak area is corrected based on the value, thereby vanadium between the materials. The (V2p3 / 2) peak areas are compared. (3) correcting method, the area of the vanadium (V2p3 / 2) peak in the catalyst surface, divided by the area of the titanium (Ti2p3 / 2) peak in the catalyst surface, the obtained value as _{A 0.}

<Vanadium concentration measurement at a depth of 40 nm to 100 nm from the surface of the catalyst>
The vanadium concentration at the depth is measured by the same procedure as above. That is, (4) measuring the area of the vanadium (V2p3 / 2) peak at a depth of 40 nm to 100 nm from the surface of the catalyst, (5) titanium (Ti2p3 / 2) peak at a depth of 40 nm to 100 nm from the surface of the catalyst. It is necessary to measure the area.

  Regarding the depth, after etching the catalyst sample to a predetermined depth with argon ions, the amount of vanadium existing at the predetermined depth can be measured by measuring vanadium (V2p3 / 2). (6) The correction method is as follows: the average value of the vanadium (V2p3 / 2) peak at a depth of 40 nm to 100 nm from the surface of the catalyst, and the area of the titanium (Ti2p3 / 2) peak at a depth of 40 nm to 100 nm from the surface of the catalyst. A value obtained by dividing by the average value of A.

  The etching depth is determined by predetermining conditions under which silica can be etched to a predetermined depth using silica as a reference material, and etching the catalyst sample according to the conditions. The etching depth at this time is measured as a silica reference value. The etching conditions under which silica can be dug down to a specific depth are confirmed in advance, and the depth is determined from the catalyst surface by etching the catalyst material under the same etching conditions (also referred to as “silica reference value”).

<Comparison of vanadium concentration in catalyst>
(7) the area of the vanadium (V2p3 / 2) peak in the catalyst surface, the value obtained by dividing the area of the titanium (Ti2p3 / 2) peak at the catalyst surface and _{A 0,} vanadium in depth 40nm~100nm from the surface of the catalyst ( V2p3 / 2) A value obtained by dividing the average value of the peak area by the average value of the area of the titanium (Ti2p3 / 2) peak at a depth of 40 nm to 100 nm from the surface of the catalyst is determined as A. A ₀ is 1.1 to 3.0 times that of A, that is, A is obtained by dividing A ₀ by 1.1. In the catalyst according to the present invention, the vanadium concentration on the surface is 1.1 to 3.0 times that in the catalyst. More preferably, it is 1.15 to 2.0, and further preferably 1.2 to 1.8. This is because if A ₀ / A is less than 1.1, sufficient catalyst performance cannot be obtained, and if it exceeds 3.0, vanadium oxide sintering may occur and the performance may deteriorate.

  The reason for improving the NOx removal performance by increasing the vanadium oxide concentration on the catalyst surface is that the NOx removal reaction takes place at the extreme surface layer of the catalyst, so the NOx removal reaction can be increased by increasing the vanadium oxide present on the catalyst surface. It can be promoted.

On the other hand, the SO ₂ oxidation rate is affected by the vanadium content of the catalyst as a whole, regardless of whether vanadium is unevenly distributed or uniformly distributed on the surface. Therefore, by increasing only the vanadium oxide concentration on the catalyst surface without increasing the vanadium content of the entire catalyst, it is possible to improve the denitration performance while maintaining a low SO ₂ oxidation rate. Further, by reducing the vanadium oxide content of the whole catalyst while increasing the vanadium oxide concentration on the catalyst surface, it is possible to suppress the SO ₂ oxidation rate while maintaining the denitration activity.

-Catalyst composition-
In the present invention, a denitration catalyst containing titanium oxide and vanadium oxide is a basic skeleton. Further, it may contain at least one selected from the group consisting of tungsten oxide and molybdenum oxide, and preferably the titanium oxide is at least one element selected from the group consisting of silicon, aluminum, zirconium, tungsten and molybdenum. And a composite oxide and / or mixed oxide of titanium and the titanium oxide is a mixture of at least two types of titanium oxides, preferably the titanium oxide is composed of titanium oxide and tungsten oxide. It is a mixture of a mixed oxide and a composite oxide of titanium and silicon.

Regarding the catalyst composition ratio, titanium oxide is 70 to 99.9% by mass as an oxide, more preferably 80 to 99.5% by mass, vanadium oxide is 0.1 to 30% by mass as a metal oxide, More preferably, it is in the range of 0.5 to 20% by mass. When the supported amount of vanadium oxide is less than 0.1% by mass, sufficient catalyst performance cannot be obtained, and even if it exceeds 30% by mass, the catalyst performance is not improved so much, but the SO ₂ oxidation rate becomes high. This is because of the above problems.

  The raw materials for titanium are titanium oxide, titanium tetrachloride, titanyl sulfate, and tetraisopropyl titanate, and the raw materials for vanadium are vanadium pentoxide, ammonium metavanadate, vanadyl sulfate, and vanadyl oxalate.

  Furthermore, at least one element selected from the group consisting of silicon, aluminum, zirconium, tungsten and molybdenum can be added. In this case, the total catalyst component is 100% by mass, and the silicon and the like are in each oxide state. The catalyst composition ratio is calculated in terms of conversion. The content thereof is preferably in the range of 0.1 to 20% by mass with respect to the catalyst composition.

  The raw materials for silicon are silica sol, water glass, and silicon tetrachloride. The raw materials for aluminum are alumina, boehmite, aluminum nitrate, aluminum oxalate, and aluminum sulfate. The raw materials for zirconium are zirconium oxide and zirconium nitrate. Zirconium sulfate, Zirconium oxychloride, Tungsten trioxide, tungstic acid, ammonium metatungstate, ammonium paratungstate as the raw materials for tungsten, Molybdenum trioxide, molybdic acid, paramolybdenum as the raw materials for molybdenum Ammonium acid.

-Catalyst preparation method-
There are various methods for increasing the vanadium oxide concentration on the catalyst surface. For example, it is possible to use means such as controlling the pH of the vanadium solution added during catalyst preparation or controlling the drying conditions. A preferable method found by the inventors is to use a mixed oxide of TiO ₂ and WO ₃ (hereinafter referred to as Ti—W mixed oxide) as a base material. The reason why the vanadium oxide concentration on the catalyst surface is high when using a Ti-W mixed oxide is not clear, but highly dispersed tungsten oxide affects the acid properties and the like of the base material, This is presumed to be involved in the movement of vanadium oxide to the surface layer. As the Ti—W mixed oxide, for example, DT-52 (trade name) manufactured by Cristal Global can be used. The Ti—W mixed oxide can also be prepared by a coprecipitation method as described in JP-A-7-88368. Ti-W mixed oxides prepared by a coprecipitation method have excellent characteristics such as a high specific surface area, and the catalyst performance is also high, so that they are more preferably used.

As a more preferable method for preparing the catalyst according to the present invention, the above-mentioned Ti—W mixed oxide and another titanium-based high specific surface area oxide may be mixed and used in the catalyst base. The specific surface area of the catalyst can be increased by mixing the high specific surface area oxide, so that even if the surface concentration of the vanadium oxide is increased, the high dispersion state is maintained, the catalytic activity is increased, and the sintering is performed. There is a merit that it can be suppressed, which is preferable. Further, as the high specific surface area oxide at this time, a composite oxide of Ti and Si (Ti-Si composite oxide) is particularly preferably used. In addition to the high specific surface area, the Ti—Si composite oxide also has unique acid properties and has an effect of suppressing the SO ₂ oxidation rate. A method for preparing a catalyst using a mixture of a Ti—W mixed oxide and a Ti—Si composite oxide as a base material will be described below.

  While stirring the mixed solution of silica sol and aqueous ammonia, a liquid or aqueous solution of a water-soluble titanium compound such as titanium tetrachloride, titanyl sulfate, tetraisopropyl titanate is gradually dropped to obtain a slurry. This is filtered, washed, dried, and then fired to obtain a Ti—Si composite oxide. The firing temperature at this time is 400 to 700 ° C., preferably 500 to 700 ° C. The Ti—Si composite oxide thus obtained is basically a composite oxide of titanium and silicon having an amorphous microstructure, and has a high specific surface area of about 150 to 200 m 2 / g. The obtained Ti—Si composite oxide powder and Ti—W mixed oxide (DT-52 (trade name) manufactured by Cristal Global) were mixed, and mixed with ammonium metavanadate, oxalic acid and monoethanolamine. A solution and an ammonium metatungstate aqueous solution are added, and further a molding aid and an appropriate amount of water are added. After kneading, the mixture is formed into a honeycomb shape by an extrusion molding machine. Then, after drying well at 50-120 degreeC, it baked at 300-750 degreeC, Preferably 350-650 degreeC for 1 to 10 hours, and obtains a molding.

Also, the specific surface area of the catalyst, often in the range of 50 to 200 m ² / g, more preferably 60~150m ² / g, further preferably, from the 65~130m ² / g. If the specific surface area of the catalyst is too low, sufficient catalyst performance cannot be obtained, and sintering of vanadium oxide is likely to occur, and if it is too high, the catalyst performance will not improve so much, but the accumulated amount of poisonous substances will increase. This is because durability may deteriorate.

  Furthermore, the pore volume of the catalyst should be such that the total pore volume is in the range of 0.2 to 0.7 mL / g, more preferably 0.3 to 0.6 mL / g, still more preferably 0.00. It should be in the range of 35-0.5 mL / g. If the pore volume of the catalyst is too small, sufficient catalyst performance will not be obtained, and if it is too large, the catalyst performance will not improve so much, but the mechanical strength of the catalyst will decrease, causing problems in handling and wear resistance. There is a risk of adverse effects such as lowering.

  The shape of the catalyst according to the present invention is not particularly limited, but can be used after being formed into a honeycomb shape, a plate shape, a corrugated plate shape, a columnar shape, a cylindrical shape, a spherical shape, or the like. Further, it may be used by being supported on a honeycomb, plate, corrugated, columnar, cylindrical or spherical carrier made of alumina, silica, cordierite, mullite, stainless steel or the like.

  The specific surface area of the catalyst referred to in the present invention is the specific surface area obtained excluding the support portion when the catalyst is supported on a support made of alumina, silica, cordierite, mullite, stainless steel or the like. Point to.

  The exhaust gas treatment catalyst of the present invention is used for treatment of various exhaust gases. There are no particular restrictions on the composition of the exhaust gas, but the catalyst of the present invention can be used for heavy oil fired boilers, coal fired boilers, gas turbines, gas engines, diesel engines, thermal power plants, incineration facilities that process industrial waste and municipal waste. Further, since it is excellent in the decomposition activity of nitrogen oxides discharged from various industrial processes, it is suitably used for the treatment of exhaust gas containing these nitrogen oxides.

In order to remove nitrogen oxides using the catalyst of the present invention, the catalyst of the present invention is contacted with exhaust gas in the presence of a reducing agent such as ammonia or urea to reduce and remove nitrogen oxides in the exhaust gas. it can. The amount of ammonia is 0.3 to 1.5 times, preferably 0.5 to 1.2 times the equivalent amount capable of decomposing nitrogen oxides into nitrogen and water. If the amount of ammonia is less than 0.3 times the equivalent of nitrogen oxides that can be decomposed into nitrogen and water, the nitrogen oxide treatment efficiency will be too low, and if it exceeds 1.5 times, the amount of unreacted ammonia will remain. This is because it increases and adversely affects the environment. Here, the equivalent amount capable of decomposing nitrogen oxides into nitrogen and water is as follows. That is, when the target substance is NO, ammonia is 1 mole with respect to 1 mole of NO, and when the target substance is NO ₂ , ammonia is 2 moles with respect to 1 mole of NO ₂ . When urea is also used, urea acts as a double mole of ammonia, so that the mole amount is half of the ammonia amount.

-Denitration method-
The conditions for removing nitrogen oxides using the catalyst of the present invention are not particularly limited, and can be carried out under conditions generally used for this type of reaction. Specifically, it may be determined as appropriate in consideration of the type and properties of the exhaust gas and the required removal rate.

The catalyst inlet gas temperature is preferably in the range of 100 to 500 ° C, more preferably 150 to 450 ° C, still more preferably 200 to 400 ° C. This is because if the inlet gas temperature is too low, sufficient removal performance cannot be obtained, and if it is 500 ° C. or higher, the catalyst life may be shortened. Also, the space velocity at that time 100~200000hr ^-1 (STP) are preferable, 1000~100000hr ^-1 (STP), more preferably, more preferably 2000~50000hr ^-1 (STP) is good. 100 hr ^-1 The following is inefficient because the greater the amount of catalyst, because the high removal rate can not be obtained by 200000Hr ^-1 or more.

  The concentration of nitrogen oxides in the exhaust gas is 5 to 5000 ppm, preferably 10 to 1000 ppm. When the concentration of nitrogen oxides in the exhaust gas is less than 5 ppm, the processing efficiency is lowered. When the concentration exceeds 5000 ppm, the amount of reducing agent required to reduce the nitrogen oxides to a predetermined concentration increases, and accordingly, there is no reaction. Since the amount of the reducing agent released into the environment as it is increases, it is not preferable.

Further, since the SO ₂ oxidation rate can be suppressed to a low level by using the technique of the present invention, it can be suitably used for the treatment of exhaust gas containing SO ₂ . The SO ₂ concentration in the exhaust gas at this time is preferably 2% by volume or less, more preferably 1% by volume or less, and still more preferably 0.5% by volume or less. This is because when the SO ₂ concentration in the exhaust gas exceeds 2% by volume, the deterioration of the catalyst may increase.

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

Example 1
<Preparation of Ti-Si composite oxide powder>
While mixing 5 kg of silica sol (containing 20 mass% as SiO ₂ ) and 140 kg of 10 mass% ammonia water, 60 L of sulfuric acid solution of titanyl sulfate (125 g / L as TiO ₂ , sulfuric acid concentration 550 g / L) is gradually added with good stirring. To form a precipitate. The slurry was aged, filtered, washed and dried at 150 ° C. for 10 hours. This was fired at 550 ° C. for 6 hours and further pulverized using a hammer mill to obtain a Ti—Si composite oxide powder.

<Addition of vanadium and tungsten>
To 7.1 kg of the Ti—Si composite oxide powder prepared by the above method, DT-52 (trade name, TiO ₂ : WO ₃ = 90: 10 (mass ratio) manufactured by Cristal Global as a Ti—W mixed oxide was used. )) 10 kg was added and mixed. Next, 1.3 kg of ammonium metavanadate, 1.6 kg of oxalic acid, and 0.5 kg of monoethanolamine were mixed and dissolved in 5 L of water to prepare a uniform solution. The vanadium-containing solution and 1.8 L of a 10% by weight methylamine aqueous solution of ammonium paratungstate (400 g / L as WO ₃ ) together with a molding aid and an appropriate amount of water were mixed with Ti-Si composite oxide and DT- In addition to the mixed powder of 52, the mixture was kneaded with a kneader and then extruded into a honeycomb shape having an outer shape of 80 mm square, a length of 500 mm, an aperture of 2.9 mm, and a wall thickness of 0.4 mm. Then, after drying at 80 degreeC, it baked at 450 degreeC for 3 hours, and the catalyst A was obtained.

The composition of the catalyst A is TiO ₂ : (Ti—Si composite oxide): V ₂ O ₅ : WO ₃ = 48: 38: 5: 9 (mass ratio), and the BET specific surface area is 97 m ² / g, all fine. The pore volume was 0.42 mL / g.

(Example 2)
To 7.1 kg of the Ti—Si composite oxide powder prepared in Example 1, DT-52 (trade name, TiO ₂ : WO ₃ = 90: 10 (mass ratio) manufactured by Cristal Global as a Ti—W mixed oxide was used. )) 10 kg was added and mixed. Next, 0.8 kg of ammonium metavanadate, 1.0 kg of oxalic acid, and 0.3 kg of monoethanolamine were mixed and dissolved in 4 L of water to prepare a uniform solution. This vanadium-containing solution is added to the mixed powder of Ti-Si composite oxide and DT-52 mixed together with a molding aid and an appropriate amount of water, and after kneading with a kneader, the outer diameter is 80 mm square, the length is 500 mm, It was extruded into a honeycomb shape with an opening of 2.9 mm and a wall thickness of 0.4 mm. Then, after drying at 80 degreeC, it baked at 450 degreeC for 3 hours, and the catalyst B was obtained.

The composition of the catalyst B is TiO ₂ : (Ti—Si composite oxide): V ₂ O ₅ : WO ₃ = 51: 40: 3: 6 (mass ratio), and the BET specific surface area is 100 m ² / g, all fine. The pore volume was 0.48 mL / g.

(Comparative Example 1)
To 7.1 kg of the Ti—Si composite oxide powder prepared in Example 1, 9 kg of DT-51 (trade name) manufactured by Cristal Global was added as TiO ₂ and mixed. Next, 1.3 kg of ammonium metavanadate, 1.6 kg of oxalic acid, and 0.5 kg of monoethanolamine were mixed and dissolved in 5 L of water to prepare a uniform solution. This vanadium-containing solution and 4.3 L of a 10% by weight aqueous solution of methyl paratungstate methylamine (400 g / L as WO ₃ ) together with a molding aid and an appropriate amount of water were mixed with Ti-Si composite oxide and DT- In addition to the mixed powder of 51, the mixture was kneaded with a kneader, and then extruded into a honeycomb shape having an outer shape of 80 mm square, a length of 500 mm, an aperture of 2.9 mm, and a wall thickness of 0.4 mm. Then, after drying at 80 degreeC, it baked at 450 degreeC for 3 hours, and the catalyst C was obtained.

The composition of the catalyst C is TiO ₂ : (Ti—Si composite oxide): V ₂ O ₅ : WO ₃ = 48: 38: 5: 9 (mass ratio), and the BET specific surface area is 102 m ² / g, all fine. The pore volume was 0.43 mL / g.

(Measurement of XPS)
Using the catalysts A to C obtained in Examples 1 and 2 and Comparative Example 1, XPS was measured under the following conditions.

<Measurement conditions>
Measuring equipment: Quanta SXM, ULVAC-PHI
X-ray source: Al Kα, beam diameter 100 μm, beam output 25 W-15 kV
Under the above conditions, V2p3 / 2 and Ti2p3 / 2 of the catalysts A to C were measured, and the obtained vanadium (V2p3 / 2) peak area was divided by the titanium (Ti2p3 / 2) peak area to obtain A ₀ did. Silica was etched 40 nm from the surface by an argon ion etching method, and after etching the catalysts A to C under the same conditions, V2p3 / 2 and Ti2p3 / 2 were measured. The etching depth of the catalysts A to C at this time was 40 nm (silica reference value). Similarly, silica was etched to 60 nm, 80 nm, and 100 nm, and after etching the catalysts A to C under the same conditions as above, V2p3 / 2 and Ti2p3 / 2 were measured. Next, the average value of the area of the vanadium (V2p3 / 2) peak and the average value of the area of the titanium (Ti2p3 / 2) peak obtained by each measurement were obtained, and the average value of the area of the vanadium (V2p3 / 2) peak was determined. Divided by the average value of the area of the titanium (Ti2p3 / 2) peak was designated as A. The values of A ₀ , A and A ₀ / A are shown in Table 1.

(Performance evaluation)
Using the catalysts A to C obtained in Examples 1 and 2 and Comparative Example 1, a denitration performance test and measurement of SO ₂ oxidation rate were performed under the following conditions.

(Reaction conditions)
Denitration performance and SO ₂ oxidation rate were measured under the following conditions.

<Denitration performance>
Gas temperature: 350 ° C
Space velocity (STP): 26,000 Hr ⁻¹
Gas composition NOx: 100 ppm, dry
NH ₃ : 100 ppm, dry
SO ₂ : 0 ppm, dry
O ₂ : 15%, dry
H ₂ O: 10%, wet
N ₂ : balance
<SO ₂ oxidation rate>
Gas temperature: 350 ° C
Space velocity (STP): 13,000 Hr ⁻¹
Gas composition NOx: 100 ppm, dry
NH ₃ : 0 ppm, dry
SO ₂ : 200 ppm, dry
O ₂ : 15%, dry
H ₂ O: 10%, wet
N ₂ : balance
Further, the denitration rate and the SO ₂ oxidation rate were determined according to the following formula.
Denitration rate (%) = [(reactor inlet NOx concentration) − (reactor outlet NOx concentration)] ÷ (reactor inlet NOx concentration) × 100
SO ₂ oxidation rate (%) = (reactor outlet SO ₃ concentration) ÷ (reactor inlet SOx concentration) × 100
The obtained denitration rate and SO ₂ oxidation rate are shown in Table 2.

  The catalyst of the present invention can be suitably used for removing nitrogen oxides contained in exhaust gas.

Claims (7)

A denitration catalyst comprising titanium oxide and vanadium oxide, wherein vanadium (V2p3 / 2) obtained by measuring the catalyst by X-ray photoelectron spectroscopy satisfies the following conditions.
(1) Measuring the area of the vanadium (V2p3 / 2) peak on the catalyst surface.
(2) Measure the area of the titanium (Ti2p3 / 2) peak on the catalyst surface.
(3) the area of the resultant vanadium (V2p3 / 2) peak (1), and _{A 0} and the resulting titanium (Ti2p3 / 2) values obtained by dividing the area of the peak (2) thing.
(4) Obtaining the average value of the vanadium (V2p3 / 2) peak area at a depth of 40 nm to 100 nm from the surface of the catalyst.
(5) Obtain an average value of the area of the titanium (Ti2p3 / 2) peak at a depth of 40 nm to 100 nm from the surface of the catalyst.
(6) Let A be the value obtained by dividing the area of the vanadium (V2p3 / 2) peak obtained in (4) by the area of the titanium (Ti2p3 / 2) peak obtained in (5). .
(7) A ₀ is 1.1 to 3.0 times A. The denitration catalyst according to claim 1, wherein the catalyst according to claim 1 further contains at least one selected from the group consisting of tungsten oxide and molybdenum oxide. The titanium oxide is a complex oxide and / or mixed oxide of titanium and at least one element selected from the group consisting of silicon, aluminum, zirconium, tungsten, and molybdenum. The denitration catalyst according to 1. The denitration catalyst according to claim 1, wherein the titanium oxide is a mixture of at least two kinds of titanium oxides. The denitration catalyst according to claim 4, wherein the titanium oxide is a mixture of a mixed oxide of titanium oxide and tungsten oxide and a composite oxide of titanium and silicon. A denitration method comprising treating exhaust gas containing nitrogen oxides using the catalyst according to claim 1. A denitration method comprising treating exhaust gas containing nitrogen oxides and sulfur oxides using the catalyst according to claim 1.