TWI406708B - Ammonia decomposition catalyst and the catalyst caused by ammonia exhaust treatment - Google Patents

Abstract

Disclosed are: a catalyst which can decompose ammonia into nitrogen that is non-toxic; and a method for treating an ammonia-containing exhaust gas. Specifically disclosed is an ammonia-decomposing catalyst, which is characterize by the following items (a) to (d): (a) the catalyst is one for treating an ammonia-containing exhaust gas; (b) the catalyst comprises copper oxide (component 1), zeolite (component 2), a noble metal (component 3), a phosphorus (component 4) and optionally an inorganic oxide (component 5); (c) the catalyst has a copper oxide content of 2 to 40 parts by weight relative to the total amount (100 parts by weight) of copper oxide and zeolite; and (d) the catalyst has a phosphorus content of 0.01 to 5 wt% relative to the total weight of copper oxide and zeolite in terms of P content.

Description

Ammonia decomposition catalyst and treatment method for ammonia-containing exhaust gas caused by the catalyst

The present invention relates to a process for decomposing ammonia into a harmless nitrogen catalyst and an ammonia-containing exhaust gas.

The ammonia-containing exhaust gas is produced by many industries such as the electronic material manufacturing industry, the fertilizer manufacturing industry, and the factory using the denitration equipment, and most of them have bad odors, and most of them are harmful to the human body, and the industry is seeking to treat them. The exhaust gas from the discharge sources usually has a composition in which the main component is air in addition to ammonia, and also contains 1 to 10% by volume of water vapor.

Examples of the exhaust gas which is a completely different discharge source include an ammonia-containing gas containing water vapor as a main component. That is, an ammonia gas extraction process is started in sewage treatment, etc., and a large amount of ammonia-containing water vapor is discharged in the process. For the catalyst for treating the exhaust gas, on the basis of a gas atmosphere having a very high water vapor concentration, high ammonia decomposition activity is required, and generation of nitrogen oxides is suppressed to convert ammonia into nitrogen and water, that is, nitrogen has high selectivity. Further, it is also necessary to withstand the durability of the catalyzed poisoning of sulphide hydrate.

Since a variety of previously described an ammonia decomposition catalyst, and the results are set forth the following: high ammonia decomposition rate, difficult to produce by-products nitrogen oxides NO _x and the like, are unlikely to cause deterioration of catalyst caused by the sulfur compounds and the like. However, when the evaluation results of the decomposition activities of the catalysts are observed, the ammonia decomposition activity is evaluated using a gas having a water vapor concentration of 2 to 10% by volume, and no treatment of ammonia in a higher concentration of water vapor is observed. example of. Specifically, there are the following reports.

Catalyst which converts N ₂ , CO ₂ and H ₂ O by contact oxidation with an exhaust gas containing an organic nitrogen compound other than ammonia discharged by the wastewater treatment, and reports on titanium dioxide and/or titanium dioxide ‧ cerium oxide A catalyst for carrying VO ₂ , WO ₃ , and palladium (see Patent Document 1).

As an exhaust gas treatment catalyst containing an organic nitrogen compound such as acrylonitrile, a metal oxide such as zeolite or Al ₂ O ₃ , SiO ₂ , TiO ₂ or ZrO ₂ is used as a carrier, and the carrier is selected from the group consisting of Fe and Cu. A catalyst obtained by one or two or more kinds of Ag and Co converts acrylonitrile into N ₂ at a high selectivity (see Patent Document 2).

As a catalyst that does not use a noble metal, a catalyst in which Mn is supported or mixed with a zeolite having SiO ₂ /Al ₂ O ₃ of 10 or more can suppress NO or NO ₂ even in the presence of excess oxygen. In the formation, ammonia is converted into N ₂ (see Patent Documents 3 and 4).

Further, regarding the catalyst limited to decomposition of ammonia, the following techniques are reported.

As the ammonia decomposition catalyst, there are introduced: bearing any V, W, Mo in the A on the TiO ₂ ‧SiO _2, or TiO _2, SiO _{2 ‧ZrO 2} of the composite oxide, and a noble metal catalyst, which The decomposition activity is high and the activity by the sulfur compound is reduced (see Patent Document 5). However, when exhaust gas having a moisture content of 2%, an NH ₃ concentration of 50 to 400 ppm, and a H ₂ S concentration of 30 ppm was used, the catalyst showed only a high initial activity result, and no evidence of durability was revealed.

There is a literature describing an ammonia decomposition catalyst which carries either V or W on TiO ₂ and Pt or Ir, and reveals that the concentration of water vapor is 10%, the concentration of NH ₃ is 10 ppm, and the concentration of SO ₂ is The ammonia decomposition rate after the treatment of the exhaust gas of 100 ppm for 3,000 hours is 88 to 93%, and has high durability (refer to Patent Document 6).

In the literature, an ammonia removal catalyst which is supported by a Group 8 metal (platinum or the like) on zeolite, γ-alumina, or titania is described (see Patent Document 7). The catalyst removes ammonia at a normal temperature of ~200 ° C in the presence of oxygen and hydrogen, but it is not known whether it is a catalyst for converting NH ₃ to N ₂ .

There are literatures on ammonia decomposing catalysts for sulfating copper, cobalt, iron, chromium, nickel, manganese metal or its oxides, and further platinum metals on alumina, titania or cerium oxide carriers. Sulfation can improve ammonia decomposition activity and N ₂ selectivity. However, this catalyst exhibits only the initial activity when the water concentration is 2% (refer to Patent Document 8).

The Applicant has found that copper oxide and zeolite are preferably contained, in addition to these, manganese oxide or noble metal, as a catalyst for the composition of a conventional catalyst containing organic nitrogen compounds or ammonia-containing exhaust gas. It has a high decomposition rate of nitrogen compounds and a high nitrogen selectivity, and a patent application is filed (refer to Patent Document 9). The catalyst is an excellent catalyst having an extremely high ammonia decomposition activity and a high N ₂ yield.

However, there is a problem to be solved in that, in the case of an ammonia-containing exhaust gas having a water vapor concentration of 2 to 10% by volume, for example, ammonia in an exhaust gas having a water vapor concentration of 20% by volume or more and further 30 to 70% by volume. At the time of decomposition, even if it is the same catalyst, the ammonia decomposition rate is lowered, and the activity is lowered when used for a long period of time.

On the other hand, it is known that phosphorus prevents the de-alumina phenomenon of zeolite in the contact decomposition reaction (see Non-Patent Document 1).

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-293480

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-58019

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2007-21482

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2007-216082

[Patent Document 5] Japanese Patent Laid-Open No. Hei 7-289897

[Patent Document 6] Japanese Patent Laid-Open No. Hei 8-131832

[Patent Document 7] Japanese Patent Laid-Open No. Hei 10-249165

[Patent Document 8] Japanese Patent Laid-Open No. Hei 8-173766

[Patent Document 9] International Publication No. 2006/006702

[Non-Patent Document 1] J. Catalysis, vol. 248, pp29~37 (2007)

Accordingly, it is an object of the present invention to provide:

(1) The ammonia decomposition, inhibiting the formation of nitrogen oxides NO _x and the like, ammonia is converted into N _2, and the catalyst made harmless;

(2) a catalyst for decomposing ammonia in a gas containing a high-concentration water vapor having a water vapor concentration of 10% by volume or more and further 20 to 70% by volume into a nitrogen gas with high efficiency;

(3) A catalyst having durability not only having an initial activity but also treating a sulfur-containing compound exhaust gas.

In the case of a catalyst which decomposes ammonia in a exhaust gas having a high water vapor concentration or a sulfur-containing compound as described above, it is undoubted that the exhaust gas having a lower concentration of the components will also be exerted. Effective role.

In order to achieve the above object, the inventors of the present invention have made an effort to study the present invention. The ammonia decomposition catalyst of the present invention and the treatment method of the ammonia-containing exhaust gas are as follows:

Invention 1:

Ammonia decomposition catalyst, its system

(a) a catalyst for treating ammonia-containing exhaust gas,

(b) containing copper oxide (component 1), zeolite (component 2), noble metal (component 3), and phosphorus (component 4),

(c) the copper oxide content is 2 to 40 parts by weight based on 100 parts by weight of the total of the copper oxide and the zeolite,

(d) The phosphorus content (P) is from 0.01% by weight to 5% by weight based on the weight of the copper oxide to the zeolite.

Invention 2:

Ammonia decomposition catalyst, its system

(a) a catalyst for treating ammonia-containing exhaust gas,

(b) a copper oxide (Component 1), zeolite (component 2), the noble metal (Component 3), phosphorus (Component 4), and is selected from _{TiO 2, ZrO 2, SiO 2} , and CeO ₂ ‧ZrO ₂ is at least 1 in Inorganic oxide (ingredient 5),

(c) the copper oxide content is 2 to 40 parts by weight with respect to 100 parts by weight of the total of the copper oxide and the above zeolite, and

(d) The phosphorus content (P) is from 0.01% by weight to 5% by weight based on the weight of the copper oxide to the zeolite.

Invention 3:

An exhaust gas treatment method comprising the steps of contacting an ammonia-containing exhaust gas with the above-mentioned catalyst to decompose ammonia into nitrogen.

Other inventions are explicitly described below.

As described above, the catalyst of the present invention contains copper oxide, zeolite, noble metal, and phosphorus. Further, as described in the above "Prior Art", it is known in Non-Patent Document 1 that phosphorus can prevent de-alumina of zeolite in contact decomposition reaction.

The catalyst of the present invention is a highly active and highly durable ammonia decomposition catalyst which can be used for treating an ammonia-containing exhaust gas which is extremely high in water vapor concentration of 10 to 70% by volume, for example. high long-term conversion of ₃ NH, few byproducts may nitrogen oxide such as NO _x converted to N _2. The catalyst further contains phosphorus present invention, as compared with the non-phosphorus catalyst, also reducing the visible effects of the formation of nitrogen oxides NO _x and other unexpected.

(definition of terms, etc.)

The meanings of the terms used in this specification are as follows unless otherwise specified:

Decomposition rate: indicates the ratio (%) of the ammonia concentration in the exhaust gas before and after contact with the catalyst.

NO _x and N ₂ O formation rate generation rate: indicates the catalyst after contacting the exhaust generated in _the NO _x concentration or concentration ratio of ammonia to N ₂ O concentration in the exhaust gas before the contact (%) with respect to.

Nitrogen oxides: means both NO _x and N ₂ O, NO _x and the like is sometimes expressed.

N ₂ Yield: represents a value obtained by subtracting the self-decomposition rate of NO _x generation rate of the exhaust gas, etc. into contact with the catalyst. That is, the ratio of conversion to N ₂ in ammonia before contact with the catalyst.

New catalyst: A catalyst that is used at the stage of exhaust gas treatment immediately after preparation or immediately. The activity of the new catalyst is referred to as the initial activity.

Use catalyst: Indicates the catalyst after long-term treatment of exhaust gas. At the time of evaluation, the durability of the catalyst, the activity of using the catalyst, and the like were measured.

The contents of the present invention are described in detail below.

The ammonia decomposition catalyst of the present invention contains copper oxide (component 1), zeolite (component 2), noble metal (component 3), and phosphorus (component 4), and further preferably contains TiO ₂ , ZrO ₂ , SiO ₂ , and CeO _{2 .} And a composition of one or two kinds of inorganic oxides (component 5) of CeO ₂ ‧ ZrO ₂ , which can be molded into various shapes suitable for exhaust gas treatment, and can be carried on carriers of various shapes ( The support is used up.

Copper oxide

The copper oxide (ingredient 1) used in the present invention means a copper-containing oxide, and includes a copper-containing composite oxide, and examples thereof include copper oxide represented by a composition formula of the general formula CuO _x (0.45≦x≦1.1), typically It is CuO and Cu ₂ O, and includes copper oxide in the form of a copper-containing composite oxide such as Hopcalite (copper manganese oxide).

The copper oxide in the catalyst of the present invention has a function of maintaining high decomposition activity and N ₂ yield, and the content thereof is 2 to 40 parts by weight, more preferably 5 to 30 parts by weight based on 100 parts by weight of total of copper oxide and zeolite. The parts by weight are particularly preferably 10 to 30 parts by weight. If the ratio of copper oxide is less than 2 parts by weight, the increased generation of NO _x and the like, resulting in the case of reduced yield of N _2, on the other hand, if the ratio of copper oxide exceeds 40 parts by weight, the relative proportion of zeolite Less, the decomposition rate is reduced.

The copper oxide is uniformly mixed with the zeolite and the inorganic oxide described below in a catalyst, and acts as a catalyst in coexistence with particles of other components. Therefore, in terms of uniform dispersion with other components, It is preferred to use particles having an average particle diameter of 0.1 μm or more and 100 μm or less.

As a method of including copper oxide in a catalyst, it is particularly preferable to use the solid particles of the above copper oxide as a starting material. As another method, an aqueous solution containing a copper compound such as copper sulfate or copper acetate may be mixed with other catalyst components, impregnated with a catalyst, and calcined at 300 to 600 ° C in an air atmosphere. Thereby, the copper salt is converted into copper oxide to contain copper oxide.

Zeolite

As the catalyst of the present invention, zeolite particles (component 2) are mixed with other components to form a catalyst. The zeolite usable in the present invention may be either a natural product or a synthetic product. For example, as a natural product zeolite, mordenite, erionite, ferrierite, and chabazite are mentioned. Examples of the synthetic product include X-type zeolite, Y-type zeolite, MFI-type zeolite, and β-type zeolite. In addition to the proton type (H type), the zeolite usable in the present invention may be an ammonium ion or an alkali metal such as Na or K, an alkaline earth metal such as Mg or Ca, a Group 8 metal such as Fe, a Group 9 metal such as Co, or Ni. Any one or more of the metal substitution type of the Group 10 metal may be used. The zeolite used in the present invention is preferably a particle having an average particle diameter of 0.1 μm or more and 100 μm or less in terms of uniform dispersion in order to exhibit a catalytic action in cooperation with other components.

Precious metal

The noble metal (component 3) used in the present invention may be one or more selected from the group consisting of Pt, Pd, Ru, Rh, Ir, and the like. Among these noble metals, Pt is particularly effective in enhancing the decomposition activity and the N ₂ yield.

The content of the noble metal element in the catalyst is preferably from 10 ppm by weight to 5,000 ppm by weight based on the weight of the copper oxide and the zeolite in terms of the decomposition reaction of ammonia. Capacity ammonia content of 10 ppm - 1% by volume, the water vapor concentration of 1% by volume to 10% of the exhaust gas treatment capacity, inhibiting the generation rate of ammonia decomposition ratio, NO _x and N ₂ O, the cost of catalyst In terms of inhibition, it is preferred that the precious metal content is in the range of 10 ppm by weight to 1000 ppm by weight. In the case of an exhaust gas treatment in which the ammonia content is 1 to 5 % by volume and the water vapor concentration is 10 to 70 % by volume, of which 20 to 70 % by volume, particularly 30 to 70 % by volume, the ammonia decomposition rate is improved. The noble metal content is preferably from 100 ppm by weight to 5,000 ppm by weight, more preferably from 500 ppm by weight to 5,000 ppm by weight. The reason for this is that if the content of the noble metal is not satisfied, the decomposition rate is insufficient, and the undecomposed ammonia is increased. On the other hand, if the content exceeds the above content, the increase in activity commensurate with the cost cannot be expected. Therefore, the precious metal content may be determined depending on the properties of the exhaust gas to be treated, the reaction conditions, and the time (durability) used.

(Method of containing precious metals)

As a method of containing a precious metal in a catalyst, examples are as follows:

(i) A method of impregnating an aqueous solution of a noble metal salt with a mixture of particles of copper oxide and zeolite.

(ii) A method of adding a precious metal salt to a slurry containing two components.

(iii) A method of preparing copper oxide or zeolite particles carrying a noble metal in advance and mixing it with other components.

(iv) A method of preparing inorganic oxide particles carrying a noble metal, for example, TiO ₂ particles carrying platinum (hereinafter referred to as Pt/TiO ₂ ), and mixing them with other components.

In the ammonia decomposition catalyst of the present invention, the catalyst obtained in the method (iv) is superior in activity and durability to the method of the above (i) to (iii), and therefore is particularly preferable. Therefore, the use of inorganic oxide particles carrying precious metals such as Pt/TiO ₂ , Pt/ZrO ₂ , Pd/TiO ₂ , Pd/ZrO ₂ , Pt/CeO ₂ ‧ZrO _{2 is} particularly effective for improving the durability of the catalyst. .

phosphorus

The ammonia decomposition catalyst of the present invention contains copper oxide, zeolite, a noble metal element, and contains phosphorus (component 4), and the amount of phosphorus (component 4) is selected from the group based on the weight of the copper oxide and the zeolite. The phosphorus (P) is 0.01% by weight or more, preferably 0.05% by weight or more, 10% by weight or less, and more preferably 5% by weight or less. The phosphorus content may be determined by considering the composition of the exhaust gas, that is, the ammonia concentration, the sulfur compound content, the water vapor concentration, and the treatment conditions, that is, the temperature to be treated or the use time of the catalyst, and if the content is too low, the durability is considered. In the case where the effect of the improvement is insufficient, on the other hand, if the phosphorus content is too high, there is a case where the initial activity is lowered.

The ammonia-containing exhaust gas varies depending on the discharge source, but in most cases, it contains a sulfur compound, and is a large amount of exhaust gas containing water vapor. If it is used for a long period of time under the ambient gas at the reaction temperature, it is easy to cause a cause. The activity due to deterioration is lowered, and the use of the phosphorus-containing catalyst of the present invention produces the following particularly remarkable effects: it is less likely to cause a decrease in activity, maintains long-term decomposition activity, and maintains a high N ₂ yield. The phosphorus is contained and the activity of the ammonia exhaust gas containing a sulfur compound such as hydrogen sulfide, thiophene or sulfide is preferably prevented from being lowered. The catalyst further contains phosphorus present invention the following effects can be seen: the higher the decomposition rate of the ammonia catalyst with the use of the new catalyst, and by-products can like reduction of NO _x.

(Method of phosphorus content)

In order to contain phosphorus in the catalyst, any of the following methods can be used:

(i) preliminarily preparing particles obtained by treating any one or two or more kinds of components of copper oxide, zeolite or an inorganic oxide described later with a phosphorus compound, and mixing them to prepare a catalyst composition. method;

(ii) a method of adding a phosphorus compound to a slurry obtained by mixing the respective catalyst components, applying the slurry to a support, and then performing heat treatment;

(iii) applying a catalyst composition containing no phosphorus to a support or the like to form a catalyst layer, and then impregnating the catalyst layer with a phosphorus-containing aqueous solution, followed by heat treatment;

Among these, especially the method of (iii) is effective for improving durability.

Examples of the phosphorus-containing compound used for containing phosphorus include phosphoric acid (H ₃ PO ₄ ), metaphosphoric acid, ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), and the like. A water-soluble phosphoric acid, an inorganic salt such as Na, K or an ammonium salt, or an organic acid ester.

The aqueous solution of the phosphorus compound is impregnated with a catalyst component or a catalyst such as zeolite or an inorganic oxide, and dried at a temperature of from ordinary temperature to 150 ° C, followed by calcination at 500 to 600 ° C, thereby preparing a phosphorus-containing compound. Catalyst.

Inorganic oxide

The catalyst of the present invention contains copper oxide (component 1), zeolite (component 2), noble metal (component 3), and phosphorus (component 4), and contains titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ). ), a composite oxide or solid solution of cerium oxide (SiO ₂ ), cerium oxide, zirconia (expressed as CeO ₂ ‧ZrO ₂ , and a molar ratio of CeO ₂ :ZrO ₂ of 1:3 to 3:1) At least one inorganic oxide (ingredient 5) in this case is particularly effective for the action of the noble metal, that is, the improvement of the decomposition activity, particularly the sustainability of the decomposition activity in long-term use. Among them, in particular, TiO ₂ and ZrO _{2 are} excellent in the sustained effect of the decomposition activity in long-term use. The content of the inorganic oxide in the catalyst is 1 to 50 parts by weight, preferably 5 to 40 parts by weight, more preferably 10 to 40 parts by weight, based on 100 parts by weight of the copper oxide and the zeolite. Share. When the content exceeds 50 parts by weight, the ratio of the content of the other components is relatively lowered, so that the decomposition activity is lowered, and if it is less than 1 part by weight, the effect cannot be exhibited.

It is particularly effective to contain the inorganic oxide in a state of carrying a noble metal in the catalyst as described above. For example, TiO ₂ particles (referred to as Pt/TiO ₂ ) having a Pt of 100 ppm by weight to 5% by weight based on TiO ₂ and previously supported on TiO ₂ particles are prepared in advance, and the particles are mixed with other particles. The components are mixed, whereby a catalyst composition containing a noble metal and an inorganic oxide can be prepared.

The size of the inorganic oxide particles used in the present invention is preferably a particle having an average particle diameter of 0.1 μm or more and 100 μm or less in order to effectively exhibit the function of the precious metal component in the catalyst composition.

The TiO ₂ used in the present invention can be used for preparing an exhaust gas treatment catalyst such as a denitrification catalyst. That is, it is preferred that the BET specific surface area is 5 to 200 m ² /g, more preferably 10 to 150 m ² /g.

ZrO ₂ , a monoclinic system, a tetragonal system, or a cubic crystal system used in the present invention may preferably be a commercially available ZrO ₂ powder, particularly a specific product of 10 m ² /g or more. Porous powder. Further, ZrO ₂ of a composite system, for example, ZrO ₂ ‧nCeO ₂ , ZrO ₂ ‧nSiO ₂ , ZrO ₂ ‧nTiO ₂ (here, n is about 0.25 to 0.75), or the like can be used. The SiO ₂ used in the present invention includes a cerium zeolite having a zeolite structure, such as mordenite.

(Preparation and formation of catalyst)

The catalyst composition of the present invention may be in the form of a powder or a slurry. Further, in practice, it is usually used as a shaped particle such as a granular material, or in the form of a known exhaust gas treatment catalyst which is supported by a support such as a honeycomb carrier.

Hereinafter, a preparation method will be described by taking a honeycomb catalyst as an example.

Copper oxide particles, zeolite particles, a noble metal compound, and a phosphorus compound are added to water, and a binder is added as needed to prepare a slurry. As another aspect, the carrier particles may be added to the slurry as described above in which the inorganic oxide particles carrying the noble metal are separately prepared. Further, as described above, the phosphorus compound may be used to carry a catalyst layer containing no phosphorus compound in a honeycomb, and then impregnated with an aqueous solution of a phosphorus compound. Specifically, the slurry containing the catalyst composition is applied to, for example, a honeycomb support by a known method including thin coating or dip coating, followed by drying at 100 to 150 ° C, and further 300 ° Calcination treatment is carried out at 700 ° C for 1 to 10 hours. The solution of the phosphorus-containing compound is impregnated with the forming catalyst obtained in the above manner, and can be dried and calcined again under the same conditions.

The shape of the support to be used is not particularly limited, and a shape in which a differential pressure generated during gas flow is small and a contact area with a gas is large is preferable. Preferred shapes include: honeycomb, sheet, grid, fiber, tube, and filter paper. The material of the support is not particularly limited, and examples thereof include known catalyst carriers such as cordierite and alumina, carbon fibers, metal fibers, glass fibers, ceramic fibers, and metals such as titanium, aluminum, and stainless steel.

In order to shape or load the catalyst of the present invention on a support, an inorganic binder or an organic binder may be appropriately mixed and used. Specific examples of the inorganic binder include colloidal cerium oxide, cerium oxide sol, alumina sol, citric acid sol, titania sol, bauxite, clay, kaolin, and sepiolite.

Method for treating ammonia-containing exhaust gas

Next, the method of treating the exhaust gas will be described below.

The ammonia-containing exhaust gas using the ammonia decomposition catalyst of the present invention is not particularly limited, and examples thereof include ammonia-containing exhaust gas from various workshops such as a semiconductor factory, coke oven exhaust, and leakage from a flue gas denitration process. The ammonia gas is exhausted by a stripping strip containing ammonia drainage to a sewage treatment plant, a sludge treatment facility, and the like.

The ammonia concentration of the ammonia-containing gas to which the present invention is applicable is, for example, 10 ppm by volume to 5% by volume. The ammonia-containing gas and air are brought into contact with the catalyst of the present invention to convert ammonia into harmless nitrogen and water for oxidative decomposition. The oxidative decomposition temperature is appropriately determined depending on the properties in the exhaust gas (water vapor concentration or ammonia concentration), reaction conditions (temperature, space velocity), degree of catalyst deterioration, etc., and is preferably selected from the range of usually 200 to 500 ° C. A temperature range of 250 to 450 ° C is preferred.

The space velocity (SV) of the exhaust gas to be treated with respect to the catalyst may be appropriately selected from the range of 100 to 100,000 hr ^-1 in consideration of the nature of the gas (ammonia concentration or water vapor concentration) or the target value of the ammonia decomposition rate.

It is preferred to adjust the ammonia concentration in the gas supplied to the catalyst reactor to 3 vol% or less, preferably 2 vol% or less. When the ammonia concentration exceeds 3% by volume, heat due to the reaction causes the temperature of the catalyst layer to rise excessively, which tends to cause deterioration of the catalyst.

Further, when the exhaust gas which does not contain the oxygen necessary for the decomposition reaction is treated, air or an oxygen-containing gas is mixed from the outside of the catalyst reactor to make the oxygen/theoretical oxygen ratio reach 1.03. ~10.0, preferably 1.1~5.0. Here, the theoretical oxygen content is the stoichiometric oxygen amount obtained according to the formula (1), and when the inlet ammonia concentration of the reactor is 1.0% by volume, the oxygen concentration is 0.77 to 7.5 vol%, preferably 0.83 to 3.8 vol. %.

4NH ₃ +3O ₂ →6H ₂ O+2N ₂ ‧‧‧(1)

The following is an example of the exhaust of a sewage treatment plant.

The sludge of the sewage treatment plant is dehydrated by a dehydrator, and the produced drainage is distilled by a distillation apparatus. If necessary, a separate device that blows steam or steam and nitrogen from the outside to promote evaporation of water and ammonia is provided. The water vapor containing ammonia separated by distillation is separated into water and ammonia by a separation tank, and after the heat is recovered, steam containing a high concentration of water and ammonia (ammonia-containing exhaust gas) is introduced into the catalyst reaction device. Further, a necessary amount of air is introduced from the outside, and ammonia is decomposed into nitrogen and water vapor by contact with the catalyst to perform detoxification treatment. An outline of the process is described in, for example, Japanese Patent Laid-Open Publication No. 2002-28637.

The catalyst of the present invention is preferably used to treat exhaust gas from activated sludge treatment. The exhaust system utilizes a catalyst and has an excessively harsh composition: a water vapor concentration of 20 to 70% by volume, a sulfur compound S component of 10 to 200 ppm by weight, ammonia of 100 ppm by volume to 3 % by volume, and the balance being nitrogen. . In other words, the exhaust gas which is particularly effective in the catalyst of the present invention is substantially a gas mainly composed of water vapor and nitrogen, in addition to ammonia. Further, it is particularly preferable to use the catalyst of the present invention for the treatment of ammonia in the exhaust gas containing the sulfur compound. The exhaust gas discharged by the activated sludge treatment is an example, but it is of course not limited thereto, and it is of course also applicable to a general ammonia-containing exhaust gas treatment mainly composed of air.

[Examples]

Hereinafter, the present invention will be described in detail based on examples. However, the invention is not limited to the embodiments.

Catalyst preparation

<Preparation of inorganic oxide particles carrying precious metals>

<Pt(0.7)/TiO ₂ particles and Pt(2.1)/TiO ₂ particles>

TiO ₂ powder (manufactured by Millennium, average particle diameter: 1 μm, BET specific surface area: 60 m ² /g) was added to an aqueous solution of dinitrodiamine platinum (Pt concentration: 4.5% by weight) in an evaporating dish, and fully impregnated. And evaporating water at a temperature of 80 to 90 ° C while stirring, drying, and then heating to 150 ° C in a dryer, and calcining the obtained powder in air at a temperature of 500 ° C for 1 hour. TiO ₂ particles carrying 0.7% by weight of Pt (metal component) (represented as Pt(0.7)/TiO ₂ .).

TiO ₂ particles (Pt(2.1)/TiO ₂ ) carrying 2.1% by weight of platinum were obtained by the same method.

<Pt(0.7)/ZrO ₂ >

ZrO ₂ particles (Pt(0.7)/) carrying 0.7% by weight of platinum were obtained by the same operation using ZrO ₂ particles (manufactured by Millennium, average particle diameter: 1 μm, BET specific surface area: 100 m ² /g). ZrO ₂ ).

<Pd(3.5)/TiO ₂ >

The above TiO ₂ powder was added to an aqueous solution of palladium nitrate (Pd concentration: 10% by weight), and TiO ₂ particles (Pd(3.5)/TiO ₂ ) carrying 3.5% by weight of Pd were obtained by the same operation.

<Pt(0.35)/SiO ₂ >

To the aqueous solution of dinitrodiamine platinum, cerium oxide powder (manufactured by Nissan Chemical Co., Ltd., CARIACT 10, average particle diameter: 10 μm) was added, and the same operation was carried out to obtain cerium oxide particles carrying 0.35 wt% of Pt. (Pt (0.35) / SiO ₂ ).

<Pd(5.0)/Al ₂ O ₃ >

In an aqueous solution of palladium nitrate (Pd concentration: 10 wt%) was added ₂ O ₃ powder Al, by the Pt (0.7) / TiO ₂ particles operation of the same, thereby obtaining 5.0 wt% of carrying Pd-Al ₂ O ₃ Particles (Pd(5.0)/Al ₂ O ₃ ).

<Pt(2.1)/CeO ₂ ‧ZrO ₂ >

A CeO ₂ ‧ZrO ₂ composite oxide (manufactured by Daisei Co., Ltd., Ce:Zr molar ratio of 4:6, average particle diameter: 1 μm, BET specific surface area: 77 m ² /g) and an aqueous solution of dinitrodiamine platinum, By the same operation, CeO ₂ ‧ZrO ₂ particles (Pt(2.1)/CeO ₂ ‧ZrO ₂ ) carrying 2.1% by weight of Pt were obtained.

<Pd(5)/Mor>

Using a H-type mordenite (manufactured by Tosoh: SiO ₂ /Al ₂ O ₃ molar ratio 18) and an aqueous solution of palladium nitrate, mordenite particles carrying 5 wt% of Pd were obtained by the same operation. (Pd(5)/Mor).

<Preparation of catalyst>

Hereinafter, a method of preparing the catalyst of the examples and the comparative examples will be described. Further, the composition of each of the obtained catalysts is shown in Table 1.

Preparation of Catalyst E-1 and Catalyst C-1

<Catalyst C-1>

H-type mordenite was added to 68 g of deionized water (manufactured by Tosoh: SiO ₂ /Al ₂ O ₃ molar ratio was 18, and 105 g of "(Mor.)" in Table 1 below), copper oxide powder (manufactured by Chemirite) 18 g and 18 g of the Pt(0.7)/TiO ₂ particles described above, and 187 g of a cerium oxide sol (manufactured by Nissan Chemical Co., Ltd., containing 20% by weight of SiO ₂ ) as a binder, and sufficiently stirred to prepare a catalyst slurry. On a honeycomb carrier made of cordierite (micropores: 200 micropores/square inch, length 50 mm × width 50 mm × height 50 mm, volume: 0.125 L), the catalyst slurry was coated by a thin coating method. It was dried at 150 ° C for 2 hours and calcined at 500 ° C for 1 hour to obtain a catalyst C-1 carrying 120 g of a catalyst layer per 1 L of the honeycomb.

<Catalyst E-1a>

The catalyst C-1 was immersed in an aqueous phosphoric acid solution (P concentration: 2.2% by weight), and the aqueous phosphoric acid solution was allowed to permeate into the catalyst layer, and then taken out, and the solution adhering to the outside of the catalyst layer was removed by blowing air, and then weighed. The amount is such that the water absorption amount of the phosphoric acid solution in the catalyst layer reaches 135 g per 1 L of the honeycomb, and the operation is repeated as needed to impregnate the phosphoric acid. Then, it was dried at 150 ° C for 2 hours, and then calcined at 500 ° C for 1 hour in an air atmosphere using a muffle furnace to obtain a catalyst E-1a having a phosphorus content of element (P) of 3.0% by weight (the present invention) catalyst).

<catalyst E-1b>

A honeycomb type catalyst was prepared under the same conditions as those for the preparation of the catalyst C-1 except that the above Pt(0.07)/TiO ₂ particles were used instead of the Pt(0.7)/TiO ₂ particles, and then the catalyst was immersed in phosphoric acid. Further, the aqueous solution (P concentration: 0.7% by weight) was treated in the same manner as the catalyst E-1a to obtain a catalyst E-1b (catalyst of the present invention) having a phosphorus content (P) of 1.0% by weight.

<Catalyst C-2>

Catalyst C-2 was prepared in the same manner as Catalyst C-1 except that ZSM-5 zeolite (SiO ₂ /Al ₂ O ₃ molar ratio of 38) was used instead of H-type mordenite.

<catalyst E-2>

The catalyst C-2 was subjected to phosphoric acid treatment in the same manner as the catalyst E-1b except that an aqueous phosphoric acid solution (P concentration: 0.7 wt%) was used to obtain a catalyst E-2 having a phosphorus (P) of 1.0%. (The catalyst of the present invention).

<Catalyst C-3>

Catalyst C-3 was obtained in the same manner as Catalyst C-1 except that the above Pd(3.5)/TiO ₂ particles were used instead of Pt(0.7)/TiO ₂ particles.

<catalyst E-3>

The catalyst C-3 was subjected to phosphoric acid treatment in the same manner as the catalyst E-1b to obtain a catalyst E-3 (catalyst of the present invention) containing 1.0% of phosphorus (P).

<Catalyst C-4>

Catalyst C-4 was prepared in the same manner as Catalyst C-1 except that the above Pt(0.7)/ZrO ₂ particles were used instead of Pt(0.7)/TiO ₂ particles.

<catalyst E-4>

The catalyst C-4 was subjected to phosphoric acid treatment in the same manner as the catalyst E-1b to prepare a catalyst E-4 (catalyst of the present invention) containing 1.0% of phosphorus (P).

<Catalyst C-5>

The catalyst slurry prepared by mixing 117 g of the above-mentioned H-type mordenite, 6 g of copper oxide powder, and 18 g of the above-mentioned Pt(0.7)/TiO ₂ particles and 187 g of the above-mentioned cerium oxide sol was used in 68 g of deionized water to mix with the catalyst C. Catalyst C-5 was obtained in the same manner as -1.

<catalyst E-5>

Using a catalyst C-5, phosphoric acid treatment was carried out in the same manner as the catalyst E-1b to prepare a catalyst E-5 (catalyst of the present invention) containing 1.0% by weight of phosphorus (P).

<catalyst E-6>

Phosphorus (P) was obtained by the same method as Catalyst C-1 and Catalyst E-1b except that 87 g of the above-mentioned H-type mordenite, 36 g of the above copper oxide powder, and 36 g of the above Pt(0.7)/TiO ₂ particles were used. 1.0% of the catalyst E-6 (the catalyst of the present invention).

<Catalyst E-7>

To 68.5 g of deionized water, 87 g of H-type mordenite, 36 g of copper oxide, 3 g of an aqueous solution of dinitrodiamine platinum (Pt concentration: 2.0%), and a cerium oxide sol (containing 20% of cerium oxide) as a binder were added. The slurry was prepared by thorough stirring. The slurry was carried in a honeycomb shape in the same manner as the catalyst C-1. Then, phosphoric acid treatment was carried out in the same manner as in the catalyst E-1b to prepare a catalyst E-7 (catalyst of the present invention) containing phosphorus (P) of 1.0% by weight. As shown in Table 1, the catalyst E-7 was prepared by containing no inorganic oxide and adding Pt to the slurry.

<Catalyst C-6>

To 68.7 g of deionized water, 123 g of H-type mordenite (manufactured by Tosoh: SiO ₂ /Al ₂ O ₃ = 18), 18 g of the above Pt (0.7) / TiO ₂ particles, and 187 g of the above cerium oxide sol were added and thoroughly stirred. And make the slurry. The slurry was used to obtain the catalyst C-6 in the same manner as the catalyst C-1. Further, a catalyst C-6 containing 1% of phosphorus (P) was obtained in the same manner as the catalyst E-1b. Catalyst C-6 is a catalyst that does not contain copper oxide.

<catalyst E-8>

A slurry prepared under the same conditions as the catalyst C-1 was placed in a honeycomb shape except that 18 g of Pt(0.35)/SiO ₂ particles was used instead of 18 g of Pt(0.7)/TiO ₂ particles. Catalyst E-8 (the catalyst of the present invention) was then prepared in the same manner as the catalyst E-1b.

<catalyst X>

A commercial denitration catalyst (manufactured by Catalyst Chemical Co., Ltd., NRU-5) was added to 233 g of deionized water (a powder was prepared by a mortar, and a 60 mesh sieve was taken). 131 g, and the above Pt was added. 18.5 g of 0.7)/TiO ₂ particles, and 117 g of a cerium oxide sol-bonding agent were added, and the slurry was sufficiently stirred to prepare a slurry, and the catalyst X was prepared by the same method as the catalyst C-1.

<Catalyst Y>

Adding dinitrodiamine platinum nitrate aqueous solution (manufactured by Tanaka Precious Metal) to γ-alumina powder (manufactured by Nikki-Universal Co., Ltd., particle size: 50-100 μm, specific surface area 150 m ² /g) to make Pd by weight ratio After reaching 5.0% and evaporating to dryness, it was calcined at 500 ° C for 2 hours to obtain Pt (5.0) / Al ₂ O ₃ particles.

200 g of Pt(5.0)/Al ₂ O ₃ particles and 50 g of alumina were mixed, and 25 g of 60% nitric acid and 725 g of ion-exchanged water were added thereto to prepare a slurry. It was thinly coated on a forming support, and the remaining slurry was blown off with compressed air, dried by a drier at 150 ° C for 3 hours, and then calcined at 500 ° C for 2 hours to obtain a Pd containing 2.0%. Catalyst Y.

[Table 1]

<activity evaluation test>

A honeycomb-type catalyst having a cylindrical shape (diameter: 21 mm, length: 50 mm) was collected from each of the above honeycomb-type catalysts, and filled into a flow-through reaction apparatus, and ammonia decomposition was carried out by evaluation condition 1 or evaluation condition 2 shown in Table 2. The activity was evaluated.

[Table 2]

<Gas Analysis Method>

Ammonia: Gas Chromatography (TCD Detector)

NO _x: Chemiluminescence (CL Formula) analyzer

N ₂ O: gas chromatography (TCD detector)

<calculation>

NH ₃ decomposition rate (%): 100-{(export NH ₃ concentration) / (inlet NH ₃ concentration) × 100}

NO _x generation rate (%) :( outlet of _the NO _x concentration) / (inlet of _the NO _x concentration) × 100

N ₂ O production rate (%): {(outlet N ₂ O concentration) × 2 / (inlet NH ₃ concentration)} × 100

N ₂ Yield (%): 100 - {( 100-NH 3 decomposition rate) + NO _x + N ₂ O formation rate generation rate}

<Endurance test>

The catalyst of the present invention is filled in a catalytic reactor of a treatment device for activated sludge drainage of a sewage treatment plant (a stripping device containing ammonia water), and the actual exhaust treatment is performed for about one year as described below. Thereby, an endurance test is carried out.

A total of 1648 commercially available ammonia decomposition catalysts (1 honeycomb size: 150 mm in length, 150 mm in width, 50 mm in height, and volume: 1.1 L) were charged in the above-mentioned catalyst reactor to form a catalyst layer having a total volume of 190 L. .

In the durability test of the present embodiment, one part of the catalyst was replaced by the catalyst of the invention and the catalyst of the comparative example (the honeycomb catalyst of the above size), and loaded into the catalyst reactor, by Table 3 The 5,000-hour endurance test was carried out for the composition of the sewage treatment plant and the operating conditions of the equipment. Further, in the endurance test, a 1.1 L cordierite honeycomb carrier was used instead of the 0.125 L cordierite honeycomb carrier, and the raw material components of each catalyst were used in an amount proportional to the volume of the honeycomb, and A 1.1 L honeycomb catalyst prepared according to the preparation conditions of the above respective catalysts.

[table 3]

In the durability evaluation, one of the two catalyst blocks to be filled was taken out at 1800 hours and 5,000 hours, and the activity evaluation was performed by the evaluation conditions shown in Table 2, and the durability was examined.

The measurement results

<Reference Example 1> Effect of Water Vapor in Exhaust Gas on Decomposition Activity An ammonia decomposition test was carried out by using the catalyst E-1b and the evaluation condition 1 and the evaluation condition 2 shown in Table 2. The results are shown in Table 4.

[Table 4]

Description

The catalyst E-1b was evaluated under the conditions of 1, and the NH ₃ decomposition rate at 350 ° C was 100%, and under the condition 2, 63% activity was exhibited. That is, it is considered that the exhaust gas treatment having a higher water vapor concentration requires a highly active catalyst as compared with the exhaust gas treatment having a low water vapor concentration.

<Reference Example 2>

Catalyst X and Catalyst Y are similar to the catalysts previously introduced as ammonia decomposition catalysts. Catalyst X and Catalyst Y were loaded into a sewage treatment plant exhaust gas treatment facility, and the activity (durability) of the catalyst after 1800 hours of treatment was measured by Condition 2 shown in Table 2. The results are shown in Table 5A and Table. 5B.

[Table 5A]

[Table 5B]

Description

The results using Catalyst X are shown as follows: the NH ₃ decomposition rate is higher at 93.4% (@350 ° C), but the N ₂ O formation rate is higher at 16.6%, so the N ₂ yield is lower at 75.1%. Further, after 1800 hours of treatment, the decomposition rate was drastically reduced to 23.1% (@350 ° C). (Refer to Table 5A, Figure 3 and Figure 4)

Y-based catalyst ammonia decomposition rate is 100%, in terms of activity of decomposed, the durability is excellent, but a higher rate of formation of NO _x and the like, a result of low catalyst yield of N _2, is not suitable for the present invention The purpose. (Refer to Table 5B, Figure 3 and Figure 4)

<Example 1>

The initial activity and durability evaluation results of the catalyst C-1 (comparative example) and the catalyst E-1 (catalyst of the present invention) and the results measured by the evaluation condition 2 shown in Table 2 are shown in the table. 6A (catalyst C-1 of Comparative Example) and Table 6B (catalyst E-1a of the example).

[Table 6A]

[Table 6B]

Description:

<Activity of Catalyst C-1>

Refer to Table 6A, Figure 1, Figure 3 and Figure 4:

(Initial activity) The NH ₃ decomposition rate exerts 100% activity at 300 to 400 °C.

(Durability) After 1800 hours of use by a practical device, the NH ₃ decomposition rate was lowered to 4.1% (@350 ° C) and 14.2% (@400 ° C).

<Activity of Catalyst E-1a>

Refer to Table 6B, Figure 2, Figure 3 and Figure 4 for reference:

(Initial activity) The NH ₃ decomposition rate is as high as 100% (@350 ° C and 400 ° C), and the production rate of NO or the like is small, and as a result, the N ₂ yield is as high as 94 to 95%, and exhibits excellent activity.

(Durability) After long-term treatment of an ammonia-containing exhaust gas having a water vapor concentration of 50% by volume by a practical device, the NH ₃ decomposition rate is maintained at a high level of 100% (after 1800 hours) at 350 ° C. . That is, compared with the catalyst C-1, the P-containing catalyst E-1a is used under severe conditions, and the activity is extremely reduced, and the durability is high.

(NO _x and N ₂ O formation rate of)

The phosphorus-containing catalyst E-1a as compared with the non-phosphorus containing catalyst C-1, the decomposition rate is as shown below, can be seen NO _x and N ₂ O formation rate of (in N ₂ O and NO _x represents the total ) reduce the effect.

<Example 2>

For the catalyst containing no phosphorus and the catalyst containing phosphorus, the initial activity and the activity after 1800 hours of treatment were evaluated by the evaluation condition 2 shown in Table 2, and the results are shown in Table 7.

[Table 7]

Description:

(1) Phosphorus-free catalyst (for example, catalyst C-3 and catalyst C-4) has a high initial activity, but the decomposition activity after 1800 hours is greatly reduced.

(2) In contrast, the phosphorus-containing catalyst of the present invention (e.g., catalyst E-3, catalyst E-4) has a high initial activity, and the degradation rate is extremely small after 1800 hours of treatment, and continues to be less. High activity.

(3) does not contain copper oxide catalyst C-6 although higher ammonia decomposition rate, but higher NO _x and the like (particularly N ₂ O) of the production rate, therefore the low yield of N _2, and this can not be achieved The purpose of the invention.

(4) Overall, the phosphorus-containing catalyst (e.g. Catalyst E-2) compared to the catalyst (e.g. Catalyst C-2) does not contain phosphorus, the low NO _x and N ₂ O formation rate, the As a result, the yield of N ₂ is higher.

<Example 3>

The catalyst E-7 and Pt/SiO ₂ particles prepared by directly adding a platinum compound to the slurry were mixed, and the catalyst E-8 prepared by mixing was used, and the activity was evaluated by the evaluation condition 1 of Table 2. The results are shown in Table 8.

[Table 8]

Description

Catalyst E-7 prepared by adding a Pt compound to the slurry has sufficiently high initial activity. However, when used for a long period of time, the activity is slightly reduced as compared with a catalyst (for example, catalyst E-1a) which is supported on inorganic oxide particles and contains Pt.

The catalyst using the Pt-loaded TiO ₂ particles (for example, the catalyst E-1a, the catalyst E-2) has less activity reduction than the catalyst E-8 prepared by using the Pt-loaded SiO ₂ particles.

By selecting the catalyst E-7 and the catalyst E-8, and simultaneously selecting the composition or processing conditions of the applicable exhaust gas, it has a sufficiently satisfactory activity.

<Example 4>

Preparation of Catalyst E-9

105 g of H-type mordenite, 18 g of the above-mentioned copper oxide powder, 18 g of the above Pt (2.1)/CeO ₂ ‧ ZrO ₂ particles, and a cerium oxide sol as a binder were dispersed in deionized water (preparation of catalyst C-1) The slurry was prepared in the same manner as in the case of using the slurry under the catalyst C-1, and thinly coated on a cordierite honeycomb carrier, followed by drying and calcination to prepare a honeycomb having 120 g of the catalyst layer per 1 L of the honeycomb. Catalyst C-9. Then, it was immersed in an aqueous phosphoric acid solution, and dried and calcined under the same conditions as the above-mentioned catalyst E-1 to obtain a honeycomb catalyst E-9 having a phosphorus content (P) of 2.0% by weight (the touch of the present invention) Media). The catalyst E-9 has the following composition:

CuO(15)-Pt/CeO ₂ (15)-Mor(85)-P(2)

Preparation of Catalyst E-10

15 g of the copper oxide powder, 85 g of the H-type mordenite powder, 20 g of the Pd (5)/Mor particles, and a cerium oxide sol as a binder were dispersed in deionized water to prepare a slurry and a catalyst C-1. The same procedure as in the case of using the slurry was carried out by thin coating on a cordierite honeycomb carrier, followed by drying and calcination, to prepare a honeycomb catalyst C-10 carrying 120 g of the catalyst layer per 1 L of the honeycomb. Then, it was immersed in an aqueous phosphoric acid solution, and dried and calcined under the same conditions as the above-mentioned catalyst E-1 to obtain a honeycomb catalyst E-10 having a phosphorus content (P) of 2.0% by weight (the touch of the present invention) Media). The catalyst E-10 has the following composition:

CuO(15)-Pd/Mor(15)-Mor(85)-P(2)

Note: This catalyst E-1 uses mordenite as an inorganic oxide, and contains a catalyst on which palladium particles are supported, and mordenite is used as a zeolite.

<Example 5>

The decomposition activity against ammonia was evaluated by the above evaluation condition 2 (refer to Table 2) using the catalysts E-9 and E-10. The evaluation results are shown in Table 9.

[Table 9]

As shown in Table 9, it can be clarified that the catalysts E-9 and E-10 of the present invention exert a decomposition rate of 100% to ammonia even under an excessively harsh condition of a water vapor concentration of 50% by volume, and N. ₂ Selective and extremely high performance.

Figure 1 shows the new catalyst of Catalyst C-1 (Comparative Example) and the decomposition activity after 1800 hours of treatment.

Fig. 2 shows the new catalyst of the catalyst E-1a (invention) and the decomposition activity after 1800 hours of treatment.

Figure 3 shows the activity of a new catalyst at 300 ° C, 350 ° C, and 400 ° C.

Figure 4 shows the activity after 1800 hours of use at 300 ° C, 350 ° C, and 400 ° C.

Claims (16)

An ammonia decomposition catalyst which is (a) a catalyst for treating an ammonia-containing exhaust gas, and (b) contains copper oxide (component 1), zeolite (component 2), noble metal (component 3), and phosphorus (component 4). And (c) the copper oxide content is 2 to 40 parts by weight based on 100 parts by weight of the total of the copper oxide and the above zeolite, and (d) is 0.01 weight by weight based on the weight of the copper oxide and the zeolite. %~5 wt%. The ammonia decomposition catalyst according to claim 1, wherein the phosphorus content is 0.05 to 5% by weight based on the weight of the copper oxide to the zeolite. The ammonia decomposition catalyst according to claim 1 or 2, wherein the precious metal content is from 10 ppm by weight to 5,000 ppm by weight based on the weight of the copper oxide to the zeolite. The ammonia decomposition catalyst according to claim 1 or 2, wherein the noble metal is selected from at least one of Pt and Pd. The ammonia decomposition catalyst according to claim 1 or 2, which further contains, in a ratio of from 1 to 50 parts by weight, based on 100 parts by weight of the total of the copper oxide and the zeolite, further selected from the group consisting of TiO ₂ , ZrO ₂ , SiO ₂ , and CeO ₂ . At least one inorganic oxide (component 5) of ZrO ₂ . The ammonia decomposition catalyst according to claim 1 or 2, which contains at least one selected from the group consisting of TiO ₂ , ZrO ₂ , SiO ₂ and CeO ₂ . At least one inorganic oxide particle of the group consisting of ZrO ₂ . An ammonia decomposition catalyst which is (a) a catalyst for treating an ammonia-containing exhaust gas, (b) contains copper oxide (component 1), zeolite (component 2), noble metal (component 3), phosphorus (component 4) And selected from the group consisting of TiO ₂ , ZrO ₂ , SiO ₂ and CeO ₂ . At least one inorganic oxide (component 5) of ZrO ₂ , (c) copper oxide content of 2 to 40 parts by weight relative to 100 parts by weight of copper oxide and the above zeolite, and (d) relative to copper oxide The weight of the zeolite and the phosphorus content are from 0.01% by weight to 5% by weight in terms of P. The ammonia decomposition catalyst according to claim 7 which contains an inorganic oxide in an amount of from 1 to 50 parts by weight based on 100 parts by weight of the total of the copper oxide and the zeolite. The ammonia decomposition catalyst according to claim 7 or 8, wherein the phosphorus content is 0.05% by weight to 5% by weight based on the weight of the copper oxide to the zeolite. The ammonia decomposition catalyst according to claim 7 or 8, wherein the precious metal content is from 10 ppm by weight to 5,000 ppm by weight based on the weight of the copper oxide to the zeolite. The ammonia decomposition catalyst according to claim 7 or 8, which is obtained by mixing at least one of Pt and Pd, which is selected from the group consisting of TiO ₂ , ZrO ₂ , SiO ₂ and CeO ₂ . At least one of the group consisting of ZrO ₂ is formed. The ammonia decomposition catalyst according to claim 7 or 8, which contains TiO ₂ particles pre-loaded with Pt, or ZrO ₂ particles pre-loaded with Pt, or mordenite particles pre-loaded with Pd, or pre-loaded with Pt's CeO ₂ . ZrO ₂ particles. The ammonia-decomposing catalyst according to claim 7 or 8, wherein the ammonia-containing exhaust gas to be treated is substantially composed of ammonia, water vapor, and nitrogen, and is supplied with oxygen or an oxygen-containing gas from the outside as needed. An exhaust gas treatment method comprising the steps of: contacting an ammonia decomposition catalyst according to any one of claims 1 to 13 with an ammonia-containing exhaust gas to decompose ammonia into nitrogen and water. The exhaust gas treatment method according to claim 14, wherein the ammonia-containing exhaust gas has a water vapor concentration of 10 to 70% by volume. The exhaust gas treatment method according to claim 15, wherein the ammonia-containing exhaust gas has a water vapor concentration of 20 to 70% by volume.