JP4098703B2 - Nitrogen oxide removing catalyst and nitrogen oxide removing method - Google Patents

Description

  The present invention relates to a nitrogen oxide removing catalyst and a nitrogen oxide removing method using the same.

As a method for removing nitrogen oxides in exhaust gas, nitrogen oxides (NO _X, etc.) in exhaust gas are contact-reduced on a denitration catalyst using a reducing agent such as ammonia or urea to produce harmless nitrogen and water. A selective catalytic reduction (SCR) process that decomposes is common.
As a nitrogen oxide removing catalyst (denitration catalyst) applied to this, a titanium-vanadium catalyst or the like is well known (for example, see Patent Document 1).
One of the uses of such a denitration catalyst is, for example, treatment of combustion exhaust gas generated from a thermal power plant. Especially when heavy oil or coal is used as the fuel, sulfur oxidation is contained in the exhaust gas. Many components (deteriorating components) that deteriorate the catalytic activity such as substances (SO _X ) and arsenic are contained.

The previously known denitration catalysts described above have excellent removal performance, but depending on the exhaust gas conditions such as containing a lot of deteriorating components, sufficient treatment performance may still not be exhibited. Development of a nitrogen oxide removal catalyst having high performance is desired.
Japanese Patent Laid-Open No. 10-235206

An object of the present invention is a nitrogen oxide such as NO _X in the exhaust gas efficiently removing nitrogen oxides catalyst which can be removed, and, to provide a nitrogen oxide removal method using the .

The present inventor has intensively studied to solve the above-mentioned problems, and repeated various estimations and experiments. As a result, in a catalyst for removing nitrogen oxides having a titanium-based oxide and a vanadium oxide as essential components, a specific compound group is used as the titanium-based oxide, and further , a sulfur compound, an alkali If a metal or a phosphorus compound is contained in a specific content ratio, the catalyst for removing nitrogen oxides has superior catalytic performance that has not been achieved in the past in terms of nitrogen oxide decomposition performance and durability of the catalyst itself. I found out that
Specifically, the present inventor, in a catalyst for removing nitrogen oxides comprising a specific titanium-based oxide and a vanadium oxide as essential components, contains a sulfur compound (sulfur content) (SO It has been found that sulfur oxides such as ₃ and SO ₄ affect the decomposition activity of nitrogen oxides in exhaust gas. In other words, a catalyst containing a titanium-based oxide usually exhibits its own solid acidity, but when a sulfur component is present, a strong solid acidity (solid superacidity) due to the sulfur component is also manifested. Is done. And, by optimizing the acid properties of the catalyst by the interaction between the solid acidity derived from the catalyst and the solid superacidity derived from the sulfur content, the decomposition of nitrogen oxides could be further promoted. I thought. Based on such findings, the results of repeated experiments and studied the sulfur content, if to contain sulfur specific amount was confirmed to be able to further improve the decomposition and removal activity of nitrogen oxides .

Similarly, the inventor of the present invention provides a catalyst for removing nitrogen oxides comprising a specific titanium-based oxide and an oxide of vanadium as essential main components, wherein the alkali metal compound contained in the catalyst is oxidized with nitrogen in exhaust gas. It was found to affect the degradation activity of the product. In other words, alkali metals are usually thought to be poisonous components that contaminate and deactivate various catalytic active components such as vanadium, tungsten, and molybdenum, but the content of alkali metal compounds is within a specific range. It has been found that, if controlled, it is particularly excellent in the durability of so-called degradation activity, which can maintain a high degradation activity over a long period of time. Thus, for example, the incinerator flue gas contains many acidic gases such as SO _x and HCl, particularly remarkable deterioration of the catalyst in the low-temperature region by the influence, on the basis of the findings described above, the specific amount of alkali If the metal compound is included, the alkali metal can moderately absorb the acidic gas and effectively prevent the deterioration of the catalyst over time, and consequently the durability of the decomposition activity can be dramatically improved. It was confirmed.

Similarly, the present inventor, in a nitrogen oxide removal catalyst having a specific titanium-based oxide and an oxide of vanadium as essential components, the phosphorus compound (phosphorus) contained in the catalyst is contained in the exhaust gas. It was found to affect the decomposition activity of nitrogen oxides. Usually, in the production of a catalyst, there are steps of calcination such as carrying an active ingredient on a carrier and calcining, forming a mixture of the component to be a carrier and the active ingredient into a desired shape and calcining. included. In this firing process, the raw material is changed to be active by decomposition or reaction, and when a molding aid such as an organic binder is used during molding, the molding aid is decomposed and removed. When the mechanical strength is required, it is a process necessary for baking the catalyst to improve the mechanical strength. However, problems such as a decrease in the specific surface area of the catalyst and agglomeration of the active component occur due to the firing. In particular, a catalyst using a titanium-based oxide as a main component together with an oxide of vanadium is preferably used since the anatase crystalline or amorphous form of titanium has a high activity and a high specific surface area. However, when heat is applied in the presence of vanadium, crystallization of titanium is likely to proceed, resulting in a decrease in specific surface area and agglomeration of active components, resulting in low activity of the finally obtained catalyst. It was. Therefore, based on such knowledge, if a specific amount of phosphorus compound is included in the catalyst, it is possible to effectively prevent a decrease in the specific surface area of the catalyst and agglomeration of the active component due to calcination, and thus to exhibit a high decomposition activity. and make sure that you can have.

Furthermore, if the exhaust gas containing nitrogen oxides is treated using these nitrogen oxide removing catalysts, it is confirmed that nitrogen oxides can be effectively removed by the excellent catalyst performance as described above. The present invention has been completed based on the knowledge regarding the control of the content of the metal compound .
That is, that written to the present invention nitrogen oxide removing catalyst (hereinafter sometimes referred to as the catalyst of the present invention.) Is a catalyst used for removing the nitrogen oxides in the exhaust gas, a titanium-based an oxide of oxide and vanadium as main components, the titanium-containing oxide is _{TiO 2 -WO 3, TiO 2 -MoO} 3, TiO 2 -SiO 2 -WO 3, TiO 2 -SiO 2 -MoO 3, TiO ₂ -WO ₃ -MoO ₃ and _{TiO 2} -SiO 2 -WO ₃ represented by -MoO ₃ consists of at least one selected from the group consisting of composite oxides, alkali metal-containing compound is a catalyst in an alkali metal atom in terms characterized in that for the entire amount contained 0.0 5-1% by weight.

Incidentally, the second catalyst for removing nitrogen oxides based on the above-mentioned knowledge concerning the sulfur compound content control is a catalyst used for removing nitrogen oxides in exhaust gas, and is an oxide of titanium-based oxide and vanadium. as a main component the door, the titanium-containing oxide is _{TiO 2 -WO 3, TiO 2 -MoO} 3, TiO 2 -SiO 2 -WO 3, TiO 2 -SiO 2 -MoO 3, TiO 2 -WO 3 -MoO 3 and represented by _{TiO 2} -SiO 2 -WO ₃ -MoO ₃ consists of at least one selected from the group consisting of compound oxide, 0.05 to 2 weight relative to the total weight of the catalyst sulfur compounds in a sulfur atom in terms % be included are those characterized by a third nitrogen oxide removing catalyst that is based on knowledge of the phosphorus compound content control, the removal of nitrogen oxides in the exhaust gas A catalyst for use in, mainly composed of an oxide of titanium-containing oxide and vanadium, the titanium-containing oxide is _{TiO 2 -WO 3, TiO 2 -MoO} 3, TiO 2 -SiO 2 -WO 3, TiO ₂ consists _{-SiO 2 -MoO 3, TiO 2 -WO} 3 -MoO 3 and _TiO 2 -SiO ₂ -WO ₃ at least one selected from the group consisting of a composite oxide represented by -MoO _3, phosphorus compound It is characterized by being contained in an amount of 0.005 to 0.2% by weight with respect to the total amount of the catalyst in terms of phosphorus atoms .

The method for removing nitrogen oxides according to the present invention is characterized in that nitrogen oxides in exhaust gas are removed using the catalyst for removing nitrogen oxides according to the present invention.

According to the present invention, the nitrogen oxide removing catalyst capable of efficiently removing nitrogen oxides such as NO _X in the exhaust gas, and can provide a nitrogen oxide removal method using the same.

Hereinafter, the nitrogen oxide removal catalyst and the nitrogen oxide removal method using the same according to the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and the examples other than the following examples are also included. The present invention can be modified as appropriate without departing from the spirit of the present invention.
Oite to catalyze a nitrogen oxide removal that written to the present invention, as a main component titanium-containing oxide and an oxide of vanadium and (vanadium oxide) (i.e., titanium-based oxide and an oxide of vanadium And as an essential catalyst component.)
In the catalyst of the present invention, one above titanium-containing oxide is a principal _{component, TiO 2 -WO 3, TiO 2} -MoO 3, TiO 2 -SiO 2 -WO 3, TiO 2 -SiO 2 -MoO 3 , TiO ₂ —WO ₃ —MoO ₃ and TiO ₂ —SiO ₂ —WO ₃ —MoO ₃ , at least one selected from the group consisting of complex oxides. In this specification, regarding the notation of the composite oxide, for example, if it is TiO ₂ —SiO ₂ —WO ₃ , a Ti—Si—W composite oxide (that is, ternary composite oxidation of Ti, Si and W). )), And the same applies to the notation of other composite oxides. Ti represents a titanium element, Si represents a silicon element, W represents a tungsten element, and Mo represents a molybdenum element.

It is preferable that the titanium-based oxide is a composite oxide listed above because the specific surface area is large, the dispersibility of the active ingredient is increased, the catalytic activity is improved, or the heat resistance is improved. Hereinafter, in the present invention, the titanium-containing oxide, since it's also comprise at least one composite oxide of titanium-based listed above, treated as a composite oxide.
In the titanium-based oxide that is one of the main components of the catalyst of the present invention, the content of Ti is 5 to 95% by weight in terms of oxide with respect to the total weight in the entire titanium-based oxide. It is preferable that it is 20 to 95% by weight. Similarly, the content of W and / or Mo (when only W or Mo is contained, it is the content thereof, and when both W and Mo are contained, the total content thereof) It is preferable that it is 0.1-25 weight% in conversion of an oxide with respect to the weight of the whole oxide, More preferably, it is 0.1-20 weight%, More preferably, it is 0.1-15 weight%. When a composite oxide containing Si is contained in the titanium-based oxide, the content of Si is 1 to 50 weights relative to the total weight of Ti and Si in the titanium-based oxide in terms of oxide. %, More preferably 1 to 40% by weight, still more preferably 1 to 30% by weight. If the content of Ti, W, Mo and Si is within the above range, the titanium-based oxide as a whole can be obtained with high activity, and as a result, the catalyst as a whole can have excellent activity. If it is out of the above range, only the catalyst having insufficient catalyst activity may be obtained.

  The preparation of the titanium-based oxide (titanium-based composite oxide) is not particularly limited, and conventionally known manufacturing techniques are applied. Specifically, preparation methods such as a precipitation method, a deposition method, and a kneading method can be applied. For example, an aqueous solution or slurry containing a titanium compound, a molybdenum compound and / or a tungsten compound, and, if necessary, a silicon compound are mixed. Then, it can be prepared by a method including a step of removing water. Specifically, before removing water from an aqueous solution or slurry containing a titanium compound, the titanium-based oxide can be easily obtained by adding a molybdenum compound and / or a tungsten compound and, if necessary, a silicon compound. it can. Specifically, the following preparation methods (1) to (3) can be preferably exemplified, but are not particularly limited thereto.

  (1) A molybdenum compound such as ammonium paramolybdate and molybdic acid and / or a tungsten compound such as ammonium paratungstate and ammonium metatungstate is dispersed in water, and ammonia water is added. While stirring the obtained aqueous solution of molybdenum and / or tungsten, a liquid or aqueous solution of a water-soluble titanium compound such as titanium tetrachloride, titanium sulfate, or tetraalkoxytitanium is gradually dropped to obtain a slurry. This is filtered, washed, dried, and then fired at a high temperature, preferably at 300 to 600 ° C., to obtain a Ti—Mo composite oxide, a Ti—W composite oxide, and a Ti—W—Mo composite oxide. It is done. In addition, when obtaining a Ti-Si-W composite oxide, Ti-Si-Mo composite oxide, or Ti-Si-W-Mo composite oxide, silica sol is previously added to an aqueous solution of molybdenum and / or tungsten and ammonia. That's fine.

  (2) Aqueous ammonia, water or the like is added to an aqueous solution of a water-soluble titanium compound and hydrolyzed to obtain a titanium hydroxide. An aqueous solution of molybdenum and / or tungsten is added to this, the moisture is evaporated while being kneaded, and then dried, and further fired at a high temperature, preferably at 300 to 600 ° C., to form a Ti—Mo composite oxide or Ti—W composite. An oxide and a Ti—W—Mo composite oxide are obtained. In addition, when obtaining a Ti—Si—W composite oxide, Ti—Si—Mo composite oxide, or Ti—Si—W—Mo composite oxide, an aqueous solution of molybdenum and / or tungsten in the titanium hydroxide is used. The silica sol may be added to the titanium hydroxide simultaneously or sequentially with the addition.

(3) Addition of molybdenum and / or tungsten compound to the metatitanic acid slurry, evaporate and dry the water while kneading, and further calcinate at a high temperature, preferably 300 to 600 ° C. Product, Ti-W composite oxide, Ti-W-Mo composite oxide are obtained. Further, when obtaining a Ti—Si—W composite oxide, Ti—Si—Mo composite oxide, or Ti—Si—W—Mo composite oxide, addition of molybdenum and / or tungsten compounds to the metatitanic acid slurry. At this time, silica sol may be added to the metatitanic acid slurry.
Among the preparation methods (1) to (3), the method (1) is more preferable.

  As a raw material for supplying a metal oxide (the above titanium oxide or vanadium oxide), a metal oxide prepared in advance can be used as well as a material capable of generating an oxide by firing. Specifically, any of inorganic and organic compounds may be used, such as titanium, other metal elements (tungsten, molybdenum or silicon) listed above or vanadium, hydroxides, ammonium salts, ammine complexes, oxalates. , Halides, sulfates, nitrates, carbonates, alkoxides, and the like can be used. Specifically, the titanium source is not particularly limited. 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. Examples of the silicon source include inorganic silicon compounds such as colloidal silica, water glass, fine particle silicon, silicon tetrachloride, silica gel, and silica sol, and organic silicon compounds such as tetraethyl silicate. As the molybdenum source, for example, molybdenum oxide, ammonium paramolybdate, molybdic acid, or the like can be used. As the tungsten source, for example, tungsten oxide, ammonium paratungstate, ammonium metatungstate, or the like can be used. As the vanadium source, for example, vanadium oxide, ammonium metavanadate, vanadyl sulfate, vanadium oxalate, or the like can be used.

  A method for preparing a catalyst comprising a titanium-based oxide and vanadium oxide as a main component of a catalyst component of the present invention, that is, a catalyst having a titanium-based oxide as a main component as a catalyst component, and other catalyst components The preparation method for containing a vanadium oxide is not particularly limited, and conventionally known catalyst preparation methods and conditions using a metal oxide as a catalyst component can be employed. For example, an aqueous solution containing a vanadium source is added to a titanium-based oxide powder as a catalyst component together with an organic or inorganic molding aid generally used for this type of molding, and the mixture is heated while mixing and kneading. There is a method in which moisture is evaporated to form an extrudable paste, which is formed into a predetermined shape such as a honeycomb with an extruder, and then dried and fired at high temperature in air. As another method, a titanium-based oxide is preliminarily formed into a predetermined shape such as a spherical or cylindrical pellet or a lattice-shaped honeycomb and fired, and then impregnated and supported with an aqueous solution containing a vanadium source. Can be mentioned. Further, a method of directly kneading, forming and firing a titanium-based oxide powder and a vanadium oxide powder as a catalyst component can also be mentioned.

As described above, the catalyst used in the present invention is preferably a molded catalyst obtained by using only the catalyst component as a constituent material of the catalyst and molding the catalyst component into a certain shape. However, the catalyst may be a supported catalyst in which a catalyst component is supported on an arbitrary inert carrier having a certain shape, or a combination of these molded catalyst and supported catalyst. It may be.
In the catalyst of the present invention, the total content of the titanium-based oxide and the vanadium oxide, which are the main components, is not particularly limited, but is preferably 50% by weight or more based on the entire catalyst component, More preferably, it is 70 weight% or more, More preferably, it is 80 weight% or more. When the total content ratio is less than 50 wt%, it may not be sufficiently removing nitrogen oxides of the NO _X or the like in the exhaust gas as a denitration catalyst. The content of vanadium oxide is preferably 0.1 to 25% by weight, more preferably 0.1 to 20% by weight, based on the total amount of titanium-based oxide and vanadium oxide. %, More preferably 0.1 to 15% by weight. If the content of the oxide of the vanadium is less than 0.1 wt%, nitrogen oxides of the NO _X like in the exhaust gas might not be sufficiently and effectively removed as the denitration catalyst, when it exceeds 25 wt% In addition, the cost is increased, and an effect corresponding to the content cannot be obtained, which may be uneconomical.

Hereinafter, Oite to catalyze a nitrogen oxide removal of the present invention will be described with the optionally luer alkali metal-containing compound to contain as an active ingredient.
The nitrogen oxide removing catalyst containing an alkali metal-containing compound, the content of alkali metal-containing compound, and for the entire amount of the catalyst with alkali metal atoms in terms of, preferably 0.01 to 0.5 wt%, more preferably is 0.01 to 0.20 wt%, Ri more preferably 0.02 to 0.20 wt% der, in the case of less than 0.01 wt%, since a small absorption capacity of acid gases in the exhaust gas, the catalyst There is a possibility that a desired effect such as prevention of deterioration or improvement in durability may not be obtained, and when it exceeds 1% by weight, there is a possibility that the effect of poisoning on the active ingredient is too great and the activity may decrease . In the catalyst of the present invention, the content of the alkali metal-containing compound is defined as 0.05 to 1% by weight.

Only one type of alkali metal-containing compound may be contained in the catalyst, or two or more types may be contained. Examples of the feedstock for the alkali metal-containing compound include alkali metal hydroxides, acetates, carbonates, and oxalates.
It does not specifically limit as an alkali metal in the said alkali metal containing compound, Although any alkali metal may be sufficient, Sodium and / or potassium are preferable.
As a method for preparing the catalyst for removing nitrogen oxides of the present invention , the above-mentioned specific titanium-based oxides can be contained so that the content of the alkali metal-containing compound in the catalyst is within the above range. Any method may be used, for example, in the step of forming a titanium-based oxide or vanadium oxide into an arbitrary shape, an appropriate amount of an alkali metal-containing compound may be added, or titanium may be formed. When preparing a base oxide or a vanadium oxide, a starting material such as an alkali metal salt is used so as to contain a desired amount of an alkali metal-containing compound, and a means used for normal catalyst production; Similarly, a titanium oxide or vanadium oxide is immersed in a liquid (preferably an aqueous solution) containing an alkali metal-containing compound so as to contain a desired amount of the alkali metal-containing compound. The method and the like. Specifically, a method in which an appropriate amount of an alkali metal-containing compound such as a sodium-containing compound or a potassium-containing compound is added to a titanium-based oxide or vanadium oxide in the state of an aqueous solution or the like is preferably used.

In addition to the titanium-based oxide and vanadium oxide that are the main components of the catalyst of the present invention, when further including other metal oxides such as molybdenum oxide and tungsten oxide described later, These other metal oxides are preferably added before adding the alkali metal-containing compound, added at the same time as adding the alkali metal-containing compound, and preferably added to the obtained titanium-based oxide. .
In the catalyst of the present invention, in addition to titanium-based oxide and vanadium oxide as main components, at least one other metal oxide such as molybdenum oxide or tungsten oxide is included as an active component. Can do. The method for preparing other metal oxides such as molybdenum oxide and tungsten oxide is not particularly limited, but specifically, the same method as the above-described vanadium oxide preparation method can be employed. Moreover, as a raw material which supplies this other metal oxide, the material which can produce | generate this other metal oxide by baking can be used besides using this other metal oxide prepared beforehand as it is.

When the oxide of tungsten, the oxide of molybdenum, or the like is included, the total content thereof is preferably 0.1 to 25% by weight in the whole catalyst of the present invention, more preferably 0.00. 1 to 20% by weight, more preferably 0.1 to 15% by weight. If the content is less than 0.1% by weight, the effect as an active ingredient may not be obtained. If it exceeds 25% by weight, the cost increases and the effect of adding only cannot be obtained. There is a fear.
Book nitrogen oxide removing catalyst of the present invention, as a method to include a metal oxide such as oxides of the oxide or tungsten of the molybdenum is not particularly limited, specifically, the above-described In the catalyst preparation method of the invention, a method similar to the method of containing a vanadium oxide can be employed.

In nitrogen oxide removal catalyst of the present invention, the sulfur compounds, so-called active ingredients such as alkali metal-containing compound and a phosphorus compound, it does not compromise the effect of the catalyst of the present invention (i.e., derived from the respective active ingredients In the range that does not impede the effect. The same applies hereinafter.) In addition, for example, a reaction compound of a sulfur compound and an alkali metal-containing compound can also be used for the effect of the catalyst of the present invention. Can be included as long as it does not interfere. In general, a trace amount of sulfur atom, phosphorus atom, alkali metal atom and their compounds, and reaction products of these compounds are originally slightly contained in the catalyst material components, or slightly in the catalyst preparation process. In general, it may be contained in a very small amount as an impurity of the catalyst itself.

  The shape of the catalyst of the present invention is not particularly limited, and can be used in various shapes such as a honeycomb shape, a plate shape, a net shape, a columnar shape, a cylindrical shape, a corrugated shape, a pipe shape, and a donut shape. The catalyst body having various shapes as described above may be, for example, an integrally molded body made only of a catalyst composition that has been fired to have a desired shape using an extrusion molding machine or the like. A titanium oxide may be applied on a heat resistant substrate having a desired shape, coated, and fired. Examples of the heat-resistant substrate include metals such as stainless steel, ceramics such as cordierite, mullite, SiC, and ceramic paper made from fibrous ceramics in a paper-like material, such as honeycombs, plates, nets, columns, Cylindrical, corrugated, pipe-shaped, donut-shaped, lattice-shaped, plate-shaped (shape in which a plurality of corrugated plates are stacked to provide a space between adjacent plates), corrugated, etc. What was processed can be illustrated.

The catalyst is usually used by being housed in a container-shaped catalyst reactor made of metal or the like. The catalyst reactor is preferably provided with a structure in which an exhaust gas inlet and an exhaust port are provided so that the exhaust gas can efficiently come into contact with the catalyst accommodated therein.
The catalyst of the present invention is suitably used for treating various exhaust gases containing nitrogen oxides. Specifically, the catalyst of the present invention is suitably used for treatment of combustion exhaust gas generated from a thermal power plant and treatment of exhaust gas generated from an incineration facility for treating industrial waste and municipal waste.
Nitrogen oxide removal method according to the present invention (hereinafter sometimes referred to as removing method of the present invention.) Is a method of treating an exhaust gas containing nitrogen oxides such as NO _X using catalysts of the present invention is there. May optionally be used in conjunction et sets look or in the second and third nitrogen oxide removing catalyst described above.

In order to perform removal treatment of nitrogen oxides using the catalyst of the present invention, the catalyst of the present invention is brought into contact with exhaust gas containing nitrogen oxides, and nitrogen oxides in the exhaust gas are decomposed and removed. The conditions at this time are not particularly limited, and 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 exhaust gas, the required nitrogen oxide decomposition and removal rate (denitration rate), and the like.
Incidentally, the space velocity of the exhaust gas when performing removal processing of nitrogen oxides using the catalyst of the present invention is usually a 100~100,000Hr ^-1 (STP), preferably 200~50,000Hr ^-1 ( STP). If it is less than 100 hr ^-1, the processing apparatus becomes inefficient because too large, on the other hand, the decomposition efficiency is lowered exceeds 100,000 ^-1. Moreover, it is preferable that the temperature in that case is 130-500 degreeC, More preferably, it is 150-400 degreeC.

Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples. In the following, “parts by weight” may be simply referred to as “parts” for convenience. Further, “wt%” may be written as “wt%” and “liter” as “L” .
"Nitrous oxide removal catalyst containing sulfur compounds"
[ Reference Example 1-1]
A titanium-tungsten composite oxide was prepared as follows. To a mixed solution of 100 kg of industrial aqueous ammonia (containing 25 wt% NH ₃ ) and 100 L of water, 2.25 kg of ammonium paratungstate powder was added, stirred well, and completely dissolved to prepare a uniform solution. To this solution, 257 L of titanyl sulfate solution (manufactured by Teika Co., containing 70 g / L as TiO _{2 and} 287 g / L as H ₂ SO ₄ ) was gradually added dropwise with stirring to form a precipitate. The co-precipitated slurry was allowed to stand for about 24 hours, washed with three times the amount of co-precipitated slurry, filtered, and dried at 100 ° C. for 1 hour. Further, it was calcined at 550 ° C. for 4 hours in an air atmosphere, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle diameter of 10 μm. The composition of the titanium-tungsten composite oxide thus prepared was TiO ₂ : WO ₃ : S = 89.4: 10: 0.6 (weight ratio).

Next, 1.29 kg of ammonium metavanadate and 1.67 kg of oxalic acid and 0.4 kg of monoethanolamine were mixed and dissolved in 8 L of water to prepare a uniform solution. After adding 19 kg of the previously prepared titanium-tungsten composite oxide powder to a kneader, a vanadium-containing solution was added together with a molding aid and stirred well. Further, after mixing well with a blender while adding an appropriate amount of water, the mixture was sufficiently kneaded with a continuous kneader and extruded into a honeycomb shape having an outer diameter of 80 mm, an opening of 3.5 mm, a thickness of 0.5 mm, and a length of 500 mm. The obtained molded product was dried at 60 ° C. and calcined at 450 ° C. for 5 hours in an air atmosphere to obtain catalyst 1-A. The composition of this catalyst was TiO ₂ : WO ₃ : S: V ₂ O ₅ = 84.9: 9.5: 0.6: 5 (weight ratio).

The oxide analysis and the catalyst composition analysis were performed by fluorescent X-ray analysis. Specifically, it was performed under the following conditions. The same analysis method was adopted in all the following Reference Examples, Examples and Comparative Examples.
Analysis device: RIX2000 manufactured by Rigaku Corporation
Sample atmosphere during analysis: vacuum Sample spin speed: 60 rpm
X-ray source: Rh tube [ Reference Example 1-2]
Oite Reference Example 1-1, the titanium using a molybdate 2.22kg instead of ammonium paratungstate - except the preparation of the molybdenum composite oxide, in the same manner as in Reference Example 1-1, the catalyst 1- B was obtained. The composition of this catalyst was TiO ₂ : MoO ₃ : S: V ₂ O ₅ = 85: 9.5: 0.5: 5 (weight ratio).

[ Reference Example 1-3]
A titanium-silica-tungsten composite oxide was prepared as follows. In a mixed solution of 6.67 kg of silica sol (Snowtex-30, manufactured by Nissan Chemical Co., containing 30 wt% in terms of SiO ₂ ), 89 kg of industrial ammonia water (containing 25 wt% NH ₃ ), and 100 L of water, ammonium paratungstate powder 2. 25 kg was added, stirred well and completely dissolved to prepare a homogeneous solution. To this solution, 229 L of titanyl sulfate solution (manufactured by Teika Co., containing 70 g / L as TiO _{2 and} 287 g / L as H ₂ SO ₄ ) was gradually added dropwise with stirring to form a precipitate. The co-precipitated slurry was allowed to stand for about 24 hours, washed with three times the amount of co-precipitated slurry, filtered, and dried at 100 ° C. for 1 hour. Further, it was calcined at 550 ° C. for 4 hours in an air atmosphere, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle diameter of 10 μm. The composition of the titanium-silica-tungsten composite oxide thus prepared was TiO ₂ : SiO ₂ : WO ₃ : S = 79.4: 10: 10: 0.6 (weight ratio).

Next, 1.29 kg of ammonium metavanadate and 1.67 kg of oxalic acid and 0.4 kg of monoethanolamine were mixed and dissolved in 8 L of water to prepare a uniform solution. After adding 19 kg of the previously prepared titanium-silica-tungsten composite oxide powder to the kneader, the vanadium-containing solution was added together with the molding aid and stirred well. Further, after mixing well with a blender while adding an appropriate amount of water, the mixture was sufficiently kneaded with a continuous kneader and extruded into a honeycomb shape having an outer diameter of 80 mm, an opening of 3.5 mm, a thickness of 0.5 mm, and a length of 500 mm. The obtained molded product was dried at 60 ° C. and calcined at 450 ° C. for 5 hours in an air atmosphere to obtain catalyst 1-C. The composition of this catalyst was TiO ₂ : SiO ₂ : WO ₃ : S: V ₂ O ₅ = 75.4: 9.5: 9.5: 0.6: 5 (weight ratio).

[ Reference Example 1-4]
Oite in Reference Example 1-3, the titanium using a molybdate 2.22kg instead of ammonium paratungstate - Silica - except the preparation of the molybdenum complex oxide, in the same manner as in Reference Example 1-3, the catalyst 1-D was obtained. The composition of this catalyst was TiO ₂ : SiO ₂ : MoO ₃ : S: V ₂ O ₅ = 75.5: 9.5: 9.5: 0.5: 5 (weight ratio).
[ Reference Example 1-5]
In Reference Example 1-4, Catalyst 1-E was obtained in the same manner as Reference Example 1-4, except that the amount of washing water was 5 times the amount of the coprecipitation slurry. The sulfur content of this catalyst was 0.05% by weight.

[ Reference Example 1-6]
In Reference Example 1-4, catalyst 1-F was obtained in the same manner as Reference Example 1-4, except that the amount of washing water was three times the amount of the coprecipitation slurry liquid. The sulfur content of this catalyst was 1.0% by weight.
[ Reference Example 1-7]
In Reference Example 1-4, Catalyst 1-G was obtained in the same manner as Reference Example 1-4, except that the amount of washing water was twice the amount of the coprecipitation slurry liquid. The sulfur content of this catalyst was 1.2% by weight.
[ Reference Example 1-8]
Oite Reference Example 1-1, ammonium paratungstate and 2.25kg was added Ru margin Warini, except the addition of ammonium paratungstate 1.12kg and 1.11kg molybdate, in the same manner as in Reference Example 1-1 Catalyst 1-H was obtained. The composition of this catalyst was TiO ₂ : WO ₃ : MoO ₃ : S: V ₂ O ₅ = 84.8: 4.8: 4.8: 0.6: 5 (weight ratio).

[ Reference Example 1-9]
Oite in Reference Example 1-3, ammonium paratungstate and 2.25kg was added Ru margin Warini, except the addition of ammonium paratungstate 1.12kg and 1.11kg molybdate, in the same manner as in Reference Example 1-3 Catalyst 1 was obtained. The composition of this catalyst was TiO ₂ : SiO ₂ : WO ₃ : MoO ₃ : S: V ₂ O ₅ = 75.3: 9.5: 4.8: 4.8: 0.6: 5 (weight ratio) Met.
[ Reference Example 1-10]
The catalyst prepared in Reference Example 1-1, the temperature of the washing water and 60 ° C., except that the wash water was 7 times the coprecipitated slurry liquid amount, in the same manner as in Reference Example 1-1, titanium - tungsten A composite oxide was obtained. The sulfur content in this composite oxide was 0.02% by weight.

Next, 1.29 kg of ammonium metavanadate and 1.67 kg of oxalic acid and 0.4 kg of monoethanolamine were mixed and dissolved in 8 L of water to prepare a uniform solution. 19 kg of the previously prepared titanium-tungsten composite oxide powder (sulfur content 0.02% by weight) was put into a kneader, and a vanadium-containing solution was added together with a molding aid, followed by thorough stirring. Furthermore, after mixing well with a blender while adding an appropriate amount of water and 0.65 kg of ammonium sulfate, the mixture was sufficiently kneaded with a continuous kneader and extruded into a honeycomb shape having an outer diameter of 80 mm, an opening of 4 mm, a wall thickness of 1 mm, and a length of 500 mm. . The obtained molded product was dried at 60 ° C. and calcined at 450 ° C. for 5 hours in an air atmosphere to obtain catalyst 1-J. The composition of this catalyst was TiO ₂ : WO ₃ : S: V ₂ O ₅ = 84.8: 9.5: 0.7: 5 (weight ratio).

[ Reference Examples 1-11 to 1-15]
In Reference Examples 1-2 to 1-5 and 1-7, after the coprecipitation slurry was washed (sulfur content washing) in the same manner as in Reference Example 1-10 for the various composite oxides prepared, catalyst preparation was performed. Catalyst 1-K to 1-O in the same manner as Reference Examples 1-2 to 1-5 and 1-7, except that the sulfur content in the catalyst was sometimes 0.7% by weight by adding ammonium sulfate. Got.
[ Reference Comparative Example 1-1]
In Reference Example 1-10, catalyst 1-P was obtained in the same manner as Reference Example 1-10, except that ammonium sulfate was not added. The composition of this catalyst was TiO ₂ : WO ₃ : S: V ₂ O ₅ = 85.48: 9.5: 0.02: 5 (weight ratio).

[ Reference Comparative Example 1-2]
In Reference Example 1-10, Catalyst 1-Q was obtained in the same manner as Reference Example 1-10, except that 2.2 kg of ammonium sulfate was added. The composition of this catalyst was TiO ₂ : WO ₃ : S: V ₂ O ₅ = 83.7: 9: 2.5: 4.8 (weight ratio).
<Nitrogen oxide decomposition treatment>
Catalyst 1-A to Catalyst 1-Q are accommodated in catalyst reactors, respectively, and a gas containing nitrogen oxide (NO _x ) is circulated from the inlet side to the outlet side of each reactor under the following processing conditions. performs decomposition and removal processes of NO _X, it was measured NOx removal efficiency. Four types of gas temperatures were set and measured in each case. The results are shown in Table 1.

Processing conditions:
Gas composition to be treated = NO _X : 200 ppm, NH ₃ : 200 ppm, O ₂ : 12%, H ₂ O: 20%, N ₂ : balance Gas temperature = 175 ° C, 200 ° C, 250 ° C, 300 ° C
Space velocity (STP) = 15,000 Hr ⁻¹
Denitration rate (NO _X removal rate) calculation formula:
Denitration rate (%) =
[{(NO _X concentration in the reactor inlet side) - (NO _X concentration in the reactor outlet)}
/ (NO _X concentration at reactor inlet side)] × 100

"Catalyst for removing nitrogen oxides containing alkali metal-containing compounds"
[ Example 1 ]
A titanium-tungsten composite oxide was prepared as follows. To a mixed solution of 100 kg of industrial aqueous ammonia (containing 25 wt% NH ₃ ) and 100 L of water, 2.25 kg of ammonium paratungstate powder was added, stirred well, and completely dissolved to prepare a uniform solution. To this solution, 257 L of titanyl sulfate solution (manufactured by Teika Co., containing 70 g / L as TiO _{2 and} 287 g / L as H ₂ SO ₄ ) was gradually added dropwise with stirring to form a precipitate. The coprecipitated slurry was allowed to stand for about 24 hours, washed thoroughly with water, filtered, and dried at 100 ° C. for 1 hour. Further, it was calcined at 550 ° C. for 4 hours in an air atmosphere, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle diameter of 10 μm. The composition of the titanium-tungsten composite oxide thus prepared was TiO ₂ : WO ₃ = 90: 10: (weight ratio).

Next, 1.29 kg of ammonium metavanadate and 1.67 kg of oxalic acid and 0.4 kg of monoethanolamine were mixed and dissolved in 8 L of water to prepare a uniform solution. After adding 19 kg of the previously prepared titanium-tungsten composite oxide powder to a kneader, a vanadium-containing solution was added together with a molding aid and stirred well. Further, 0.05 kg of sodium carbonate and an appropriate amount of water were added and mixed well with a blender, and then kneaded thoroughly with a continuous kneader. The outer diameter was 80 mm, the opening was 3.5 mm, the wall thickness was 0.5 mm, and the length was 500 mm. Extruded into a honeycomb shape. After drying the resulting molded product at 60 ° C., under an air atmosphere to obtain a medium A tactile and calcined 5 hours at 450 ° C.. The composition of this catalyst was TiO ₂ : WO ₃ : Na: V ₂ O ₅ = 85.4: 9.5: 0.1: 5 (weight ratio).

[ Example 2 ]
In Example 1, titanium using molybdate 2.22kg instead of ammonium paratungstate - except the preparation of the molybdenum composite oxide, in the same manner as in Example 1, to obtain a catalytic B. The composition of this catalyst was TiO ₂ : MoO ₃ : Na: V ₂ O ₅ = 85.4: 9.5: 0.1: 5 (weight ratio).
[ Example 3 ]
A titanium-silica-tungsten composite oxide was prepared as follows. In a mixed solution of 6.67 kg of silica sol (Snowtex-30, manufactured by Nissan Chemical Co., containing 30 wt% in terms of SiO ₂ ), 89 kg of industrial ammonia water (containing 25 wt% NH ₃ ), and 100 L of water, ammonium paratungstate powder 2. 25 kg was added, stirred well and completely dissolved to prepare a homogeneous solution. To this solution, 229 L of titanyl sulfate solution (manufactured by Teika Co., containing 70 g / L as TiO _{2 and} 287 g / L as H ₂ SO ₄ ) was gradually added dropwise with stirring to form a precipitate. The coprecipitated slurry was allowed to stand for about 24 hours, washed thoroughly with water, filtered, and dried at 100 ° C. for 1 hour. Further, it was calcined at 550 ° C. for 4 hours in an air atmosphere, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle diameter of 10 μm. The composition of the titanium-silica-tungsten composite oxide thus prepared was TiO ₂ : SiO ₂ : WO ₃ = 80: 10: 10 (weight ratio).

Next, 1.29 kg of ammonium metavanadate and 1.67 kg of oxalic acid and 0.4 kg of monoethanolamine were mixed and dissolved in 8 L of water to prepare a uniform solution. After adding 19 kg of the previously prepared titanium-silica-tungsten composite oxide powder to the kneader, the vanadium-containing solution was added together with the molding aid and stirred well. Further, 0.05 kg of sodium carbonate and an appropriate amount of water were added and mixed well with a blender, and then kneaded thoroughly with a continuous kneader. The outer diameter was 80 mm, the opening was 3.5 mm, the wall thickness was 0.5 mm, and the length was 500 mm. Extruded into a honeycomb shape. After drying the resulting molded product at 60 ° C., under an air atmosphere to obtain a medium C catalyst was calcined for 5 hours at 450 ° C.. The composition of this catalyst was TiO ₂ : SiO ₂ : WO ₃ : Na: V ₂ O ₅ = 75.9: 9.5: 9.5: 0.1: 5 (weight ratio).

[ Example 4 ]
Oite Example 3, a titanium using the molybdate 2.22kg instead of ammonium paratungstate - Silica - except the preparation of the molybdenum complex oxide, in the same manner as in Example 3, to obtain a catalytic D It was. The composition of this catalyst was TiO ₂ : SiO ₂ : MoO ₃ : Na: V ₂ O ₅ = 75.9: 9.5: 9.5: 0.1: 5 (weight ratio).
[ Examples 5 to 8 ]
In Example 4 , the amount of sodium carbonate added was adjusted so that the sodium content of the resulting catalyst was 0.05 wt%, 0.25 wt%, 0.29 wt% and 0.5 wt%. except that the, in the same manner as in example 4, was obtained catalysts E, F, and G and H.

[ Example 9 ]
Oite to Example 1, ammonium paratungstate and 2.25kg was added Ru margin Warini, except the addition of ammonium paratungstate 1.12kg and 1.11kg molybdate, in the same manner as in Example 1, catalysts I Got. The composition of this catalyst was TiO ₂ : WO ₃ : MoO ₃ : Na: V ₂ O ₅ = 85.3: 4.8: 4.8: 0.1: 5 (weight ratio).
[ Example 10 ]
Oite Example 3, ammonium paratungstate and 2.25kg was added Ru margin Warini, except the addition of ammonium paratungstate 1.12kg and 1.11kg molybdate, in the same manner as in Example 3, catalytic J Got. The composition of this catalyst was TiO ₂ : SiO ₂ : WO ₃ : MoO ₃ : Na: V ₂ O ₅ = 75.8: 9.5: 4.8: 4.8: 0.1: 5 (weight ratio) Met.

[ Examples 1 to 16]
In Example 1～4,9 and 1 0, during the preparation of the catalyst, using potassium carbonate instead of sodium carbonate, the content of K (potassium) in the catalyst was adjusted to be 0.1 wt% Otherwise, in the same manner as in example 1～4,9 and 1 0, give catalysts K, L, M, N, and O and P.
[Comparative Example 1 ]
The catalyst prepared in Example 1, except that no sodium carbonate was added during the preparation of the catalyst, in the same manner as in Example 1, to obtain a catalytic Q. The total of the sodium content and potassium content in this catalyst was 0.007% by weight.

[Comparative Example 2 ]
The catalyst prepared in Example 1, by adjusting the amount of sodium carbonate during the preparation of the catalyst, except that the sodium content in the resultant catalyst was set to be 2% by weight, in the same manner as in Example 1 Te was obtained catalysts R.
<Nitrogen oxide decomposition treatment>
The catalytic A ~ catalysts R accommodated in each catalytic reactor, these to each reactor the inlet side from the outlet, nitrogen oxides gas containing (NO _X) by distributed processing under the following conditions NO _X The denitration rate was measured at the start of the process, 2000 hours after the start of the process, and 5000 hours after the start of the process. The results are shown in Table 2.

Processing conditions:
Gas composition to be treated = NO _X : 200 ppm, NH ₃ : 200 ppm, SO ₂ : 50 ppm, O ₂ : 12%, H ₂ O: 18%, N ₂ : balance Gas temperature = 190 ° C.
Space velocity (STP) = 12,000Hr ⁻¹
Denitration rate (NO _X removal rate) calculation formula:
Denitration rate (%) =
[{(NO _X concentration in the reactor inlet side) - (NO _X concentration in the reactor outlet)}
/ (NO _X concentration at reactor inlet side)] × 100

"Nitrous oxide removal catalyst containing phosphorus compounds"
[Reference Example 2 -1]
A titanium-tungsten composite oxide was prepared as follows. To a mixed solution of 102 kg of industrial aqueous ammonia (containing 25 wt% NH ₃ ) and 100 L of water, 2.25 kg of ammonium paratungstate powder was added, stirred well, and completely dissolved to prepare a uniform solution. To this solution, 257 L of titanyl sulfate solution (manufactured by Teika Co., containing 70 g / L as TiO _{2 and} 287 g / L as H ₂ SO ₄ ) was gradually added dropwise with stirring to form a precipitate. The coprecipitated slurry was allowed to stand for about 24 hours, washed well with water, filtered, and dried at 120 ° C. for 1 hour. Furthermore, it was fired at 570 ° C. for 4 hours in an air atmosphere, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle diameter of 10 μm. The composition of the titanium-tungsten composite oxide thus prepared was TiO ₂ : WO ₃ = 90: 10: (weight ratio).

Next, 1.29 kg of ammonium metavanadate and 1.67 kg of oxalic acid and 0.4 kg of monoethanolamine were mixed and dissolved in 9 L of water to prepare a uniform solution. After adding 19 kg of the previously prepared titanium-tungsten composite oxide powder to a kneader, a vanadium-containing solution was added together with a molding aid and stirred well. Further, 0.026 kg of orthophosphoric acid (75% by weight as H ₃ PO ₄ ) and an appropriate amount of water were added and mixed well with a blender, and then kneaded thoroughly with a continuous kneader, and the outer diameter was 80 mm and the aperture was 3.5 mm. It was extruded into a honeycomb shape having a wall thickness of 0.5 mm and a length of 500 mm. The obtained molded product was dried at 60 ° C. and calcined at 450 ° C. for 5 hours in an air atmosphere to obtain Catalyst 2- A. The composition of this catalyst was TiO ₂ : WO ₃ : V ₂ O ₅ : P = 85.47: 9.5: 5: 0.03 (weight ratio).

Reference Example 2-2]
Reference Example 2 -1, titanium using molybdate 2.22kg instead of ammonium paratungstate - except the preparation of the molybdenum composite oxide, in the same manner as in Reference Example 2 -1, the catalyst 2 -B Obtained. The composition of this catalyst was TiO ₂ : MoO ₃ : V ₂ O ₅ : P = 85.47: 9.5: 5: 0.03 (weight ratio).
[ Reference Example 2-3 ]
A titanium-silica-tungsten composite oxide was prepared as follows. In a mixed solution of 6.67 kg of silica sol (Snowtex-30, manufactured by Nissan Chemical Co., 30 wt% converted to SiO ₂ ), 92 kg of industrial ammonia water (containing 25 wt% NH ₃ ) and 100 L of water, ammonium paratungstate powder 2. 25 kg was added, stirred well and completely dissolved to prepare a homogeneous solution. To this solution, 229 L of titanyl sulfate solution (manufactured by Teika Co., containing 70 g / L as TiO _{2 and} 287 g / L as H ₂ SO ₄ ) was gradually added dropwise with stirring to form a precipitate. The coprecipitated slurry was allowed to stand for about 24 hours, washed thoroughly with water, filtered, and dried at 100 ° C. for 1 hour. Furthermore, it was fired at 570 ° C. for 4 hours in an air atmosphere, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle diameter of 10 μm. The composition of the titanium-silica-tungsten composite oxide thus prepared was TiO ₂ : SiO ₂ : WO ₃ = 80: 10: 10 (weight ratio).

Next, 1.29 kg of ammonium metavanadate and 1.67 kg of oxalic acid and 0.4 kg of monoethanolamine were mixed and dissolved in 9 L of water to prepare a uniform solution. After adding 19 kg of the previously prepared titanium-silica-tungsten composite oxide powder to the kneader, the vanadium-containing solution was added together with the molding aid and stirred well. Further, 0.026 kg of orthophosphoric acid (75% by weight as H ₃ PO ₄ ) and an appropriate amount of water were added and mixed well with a blender, and then kneaded thoroughly with a continuous kneader, and the outer diameter was 80 mm and the aperture was 3.5 mm. It was extruded into a honeycomb shape having a wall thickness of 0.5 mm and a length of 500 mm. The obtained molded product was dried at 60 ° C. and then calcined at 450 ° C. for 5 hours in an air atmosphere to obtain Catalyst 2- C. The composition of this catalyst was TiO ₂ : SiO ₂ : WO ₃ : V ₂ O ₅ : P = 75.97: 9.5: 9.5: 5: 0.03 (weight ratio).

[ Reference Example 2-4 ]
Oite Reference Example 2 -3, titanium using molybdate 2.22kg instead of ammonium paratungstate - Silica - except the preparation of the molybdenum complex oxide, in the same manner as in Reference Example 2-3, the catalyst 2- D was obtained. The composition of this catalyst was TiO ₂ : SiO ₂ : MoO ₃ : V ₂ O ₅ : P = 75.97: 9.5: 9.5: 5: 0.03 (weight ratio).
[Reference Example 2 -5 to 2 -7]
In Reference Example 2-4 , except that the addition amount of orthophosphoric acid was adjusted so that the phosphorus content of the obtained catalyst was 0.07 wt%, 0.15 wt% and 0.18 wt%. In the same manner as in Reference Example 2-4 , catalysts 2- E, 2- F and 2- G were obtained.

[Reference Example 2 -8]
Oite Reference Example 2 -1, of ammonium paratungstate and 2.25kg was added Ru margin Warini, except the addition of ammonium paratungstate 1.12kg and 1.11kg molybdate, in the same manner as in Reference Example 2 -1 Catalyst 2- H was obtained. The composition of this catalyst was TiO ₂ : WO ₃ : MoO ₃ : V ₂ O ₅ : P = 85.37: 4.8: 4.8: 5: 0.03 (weight ratio).
[Reference Example 2 -9]
Oite Reference Example 2 -3, ammonium paratungstate instead of adding 2.25 kg, except the addition of ammonium paratungstate 1.12kg and 1.11kg molybdate, in the same manner as in Reference Example 2-3 Catalyst 2- I was obtained. The composition of this catalyst was TiO ₂ : SiO ₂ : WO ₃ : MoO ₃ : V ₂ O ₅ : P = 75.87: 9.5: 4.8: 4.8: 5: 0.03 (weight ratio) Met.

[Comparative Reference Example 2 -1]
The catalyst prepared in Reference Example 2 -1, except for not adding orthophosphoric acid in the preparation of the catalyst, in the same manner as in Reference Example 2-1, to obtain a catalyst 2 -J. The phosphorus content in the catalyst was 0.002% by weight.
[Comparative Reference Example 2-2]
The catalyst prepared in Reference Example 2 -1, by adjusting the amount of orthophosphoric acid in the preparation of the catalyst, except that the phosphorus content in the resultant catalyst was set to be 0.5% by weight, Reference Example In the same manner as in 2-1, catalyst 2- K was obtained.

<Nitrogen oxide decomposition treatment>
Catalyst 2- A to Catalyst 2- K are respectively accommodated in a catalyst reactor, and a gas containing nitrogen oxide (NO _x ) is circulated from the inlet side to the outlet side of each reactor under the following processing conditions. performs decomposition and removal processes of NO _X, it was measured NOx removal efficiency. Three types of gas temperatures were set and measured in each case. The results are shown in Table 3 .
Processing conditions:
Gas composition to be treated = NO _X : 200 ppm, NH ₃ : 200 ppm, O ₂ : 9%, H ₂ O: 18%, N ₂ : balance Gas temperature = 180 ° C, 210 ° C, 250 ° C
Space velocity (STP) = 15,000 Hr ⁻¹
Denitration rate (NO _X removal rate) calculation formula:
Denitration rate (%) =
[{(NO _X concentration in the reactor inlet side) - (NO _X concentration in the reactor outlet)}
/ (NO _X concentration at reactor inlet side)] × 100

The catalyst for removing nitrogen oxides and the method for removing nitrogen oxides of the present invention can be preferably applied to the removal of nitrogen oxides (NO _{X and the} like) in exhaust gas.

Claims (3)

A catalyst for use in removing the nitrogen oxides in the exhaust gas, as a main component an oxide of titanium-containing oxide and vanadium, the titanium-based oxide is _{TiO 2 -WO 3, TiO 2 -MoO} 3, selected from the group consisting of _{TiO 2 -SiO 2 -WO 3, TiO} 2 -SiO 2 -MoO 3, TiO 2 -WO 3 -MoO 3 and composite oxides represented by _{TiO 2} -SiO 2 -WO ₃ -MoO ₃ at least one consists, characterized in that the alkali metal-containing compound is contained 0.0 0 5 1 wt% relative to the total amount of the catalyst with alkali metal atoms in terms of nitrogen oxide removing catalysts. The catalyst for removing nitrogen oxides according to claim 1 , wherein the alkali metal is sodium and / or potassium. To remove nitrogen oxides in the exhaust gas by using the catalyst according to claim 1 or 2, nitrogen oxide removal method.