JP7479588B2 - Method for treating ammonia-containing gas, treating material, and method for producing treating material - Google Patents

Description

The present invention relates to the treatment of factory exhaust gas, and in particular to a method for treating ammonia-containing gas, a treatment material, and a method for producing the treatment material.

Generally, chemical treatment methods such as absorption with an acid solution, methods using adsorbents such as activated carbon or zeolite, and catalytic decomposition methods are used to treat ammonia present in exhaust gas. Of these, catalytic decomposition methods in particular can continuously decompose large amounts of exhaust gas into harmless nitrogen gas by contacting the exhaust gas with a catalyst under high-temperature conditions. Methods have also been proposed in which ammonia is brought into contact with oxygen to convert it into nitrogen gas and water vapor gas (oxidative decomposition) and conversion to hydrogen (see Patent Documents 1 to 3).

On the other hand, as a wastewater treatment technology, an ammonia-containing water treatment material containing alumina selected from γ-alumina or θ-alumina and aluminosilicates made from various clays as raw materials has been proposed, and it has also been proposed to support metals on the treatment material (Patent Documents 4 and 5).

JP 2006-289211 A JP 2006-167493 A JP 2013-237045 A JP 2017-164671 A JP 2019-171311 A

As described above, there are various methods for treating exhaust gas. However, when an ammonia-containing gas is oxidized and burned, harmful nitrogen oxides such as NOx and _N2O are usually generated as by-products. Therefore, NOx removal treatment using a NOx reduction catalyst tower or the like is required downstream of the ammonia oxidation catalyst. As a result, the treatment equipment tends to be complicated and expensive.

On the other hand, it is possible to repurpose existing ammonia-containing gas treatment materials for exhaust gas treatment, but the density and conditions surrounding the treatment target differ between liquids and gases, and the required standards are also different. Furthermore, wastewater treatment requires the addition of hydrogen peroxide solution and reactions under high pressure, so the treatment conditions are also significantly different.

The present invention has been made in consideration of the above circumstances, and aims to provide a method for treating an ammonia-containing gas, a treating material, and a manufacturing method for the treating material, which can decompose an ammonia-containing gas at a high decomposition rate at a mild reaction temperature without generating harmful NOx or N ₂ O.

(1) In order to achieve the above object, the method for treating an ammonia-containing gas of the present invention includes a step of heating a catalyst layer to 150°C or more and 300°C or less, and a step of passing an ammonia-containing gas through the heated catalyst layer to oxidatively decompose the ammonia into nitrogen gas and water, and is characterized in that the catalyst layer uses a treatment material comprising a complex containing γ-alumina or θ-alumina and an aluminosilicate, and a metal supported by the complex. In this way, the ammonia-containing gas can be decomposed at a high decomposition rate at a mild reaction temperature without generating harmful NOx or N ₂ O.

(2) Furthermore, the method for treating ammonia-containing gas of the present invention is characterized in that the composite contains 30 wt % or more and 70 wt % or less of the gamma alumina. This allows the composite to maintain a sufficient specific surface area and does not deteriorate even when exposed to a mist containing strongly alkaline water droplets and air.

(3) Furthermore, the method for treating ammonia-containing gas of the present invention is characterized in that the metal is one or a combination of metals selected from the group consisting of platinum, palladium, ruthenium, nickel, rhodium, and copper. This makes it possible to achieve ammonia decomposition at a high decomposition rate.

(4) Furthermore, the method for treating ammonia-containing gas of the present invention is characterized in that the metal is present in an amount of 0.001 wt% or more and 0.1 wt% or less relative to the composite. This makes it possible to achieve a high ammonia decomposition rate at low cost.

(5) The ammonia-containing gas treatment material of the present invention is characterized in that it comprises a composite containing gamma-alumina and aluminosilicate, and a metal supported by the composite, and the metal is present in an amount of 0.001 wt% or more and 0.1 wt% or less relative to the composite. This makes it possible to achieve a high ammonia decomposition rate at low cost.

(6) The method for producing a treatment material for ammonia-containing gas of the present invention is characterized by comprising the steps of: kneading γ-alumina and silicate hydrate so that the content of γ-alumina is 30 wt% or more and 70 wt% or less to obtain a kneaded product; molding the kneaded product; firing the molded product obtained by the molding at 900°C or more and 1200°C or less; and supporting 0.001 wt% or more and 0.1 wt% or less of metal on the fired product obtained by the firing. This makes it possible to produce a treatment material that can decompose ammonia-containing gas at a high decomposition rate at a mild reaction temperature without generating harmful NOx or N ₂ O.

According to the present invention, it is possible to decompose an ammonia-containing gas at a high decomposition rate at a mild reaction temperature without generating harmful NOx or N ₂ O.

(a) to (d) NH ₃ /He gas was adsorbed on a sample carrying 1 wt % Pt, and then O ₂ /He gas was passed through the sample to decompose ammonia gas. The graphs show the time-dependent changes in ionic strength of N ₂ , NO, N ₂ O, and NO ₂ gases generated at catalyst layer temperatures of 100, 200, and 300° C. Graphs showing the results of measuring the change in ion intensity of m/z=28 (N2) generated at catalyst layer temperatures of 100, 200, and 300°C when _NH3 /He and _O2 /He gases were alternately passed through samples carrying 1 wt% Pt, Pd, and _Rh , respectively, and a sample without metal support. FIG. 1 is a schematic diagram of an apparatus used in an ammonia decomposition test. 1 is a table showing the results of an ammonia decomposition gas test carried out using samples carrying 0.1 wt % of various metals at a catalyst layer temperature of 250° C. and an air supply rate of 100 ml/min. 1 is a table showing the effect of reaction temperature on the ammonia decomposition rate of Pt and Pd supported samples. (a) A table showing the change in ammonia decomposition rate after 24 hours when air is supplied to a 0.1 wt% Pt sample at 100, 300, and 500 ml/min. (b) A table showing the change in ammonia decomposition rate after 48 hours when air is supplied to a 0.1 wt% Pd sample at 100, 300, and 500 ml/min. 1 is a table showing the ammonia decomposition performance of samples with Pt loadings of 0, 0.001, 0.01, 0.05, and 0.1 wt %.

The following describes an embodiment of the present invention.

[Composition of treatment material]
The material for treating ammonia-containing gas includes γ-alumina or θ-alumina and aluminosilicate. γ-alumina has a spinel-type crystal structure, and the specific surface area of its particles is larger than that of α-alumina. If the specific surface area of the treating material is large, the ammonia decomposition performance can be improved.

If the alumina content in the ammonia-containing gas treatment material is too low, the specific surface area cannot be increased sufficiently. On the other hand, if the alumina content is too high, the alkali resistance decreases. For these reasons, the alumina content in the treatment material is 30 wt% to 70 wt%, preferably 35 wt% to 65 wt%, and more preferably 40 wt% to 60 wt%.

Aluminosilicate is a composite oxide (binary oxide) consisting of Al ₂ O ₃ (alumina) and SiO ₂ (silica). Examples of aluminosilicate include Al ₂ O _{3.2SiO 2} and Al ₂ O _{3.4SiO 2.} The aluminosilicate contained in the treatment material may be a single type or a mixture of two or more types. These are effective in promoting the sintering of γ-alumina and suppressing hydration by ammonia water.

The treatment material for ammonia-containing gas may further contain silica. Silica is silicon dioxide (SiO ₂ ), and examples thereof include quartz contained in the raw material silicate hydrate, cristobalite produced by firing, and glass-like silica resulting from a reaction between silica and an alkali component. One or more types of silica are contained in the treatment material. In the treatment material, γ-alumina, aluminosilicate, and silica form a complex, and the complex serves as a carrier for the metal.

The content of aluminosilicate in the composite can be adjusted appropriately depending on the amount of alumina. For example, if the content of alumina in the composite is 30 wt% to 70 wt%, the content of aluminosilicate (total amount with silica if silica is included) can be adjusted to 70 wt% to 30 wt%.

The composite supports a metal as an active component. Examples of supported metals include platinum, palladium, ruthenium, rhodium, indium, iridium, gold, silver, cobalt, copper, nickel, tungsten, and water-insoluble or poorly water-soluble compounds of these metals. Specific examples include oxides such as cobalt monoxide, nickel monoxide, ruthenium dioxide, dirhodium trioxide, palladium monoxide, iridium dioxide, cupric oxide, and tungsten dioxide, chlorides such as ruthenium dichloride and platinum dichloride, sulfides such as ruthenium sulfide and rhodium sulfide, nitrates such as rhodium nitrate, nickel nitrate, copper nitrate, and silver nitrate, and complexes such as hexachloroplatinic acid hexahydrate, hexaammineruthenium chloride, and diamminepalladium nitrite. The amount of metal supported is preferably 0.001 wt% to 0.1 wt% of the weight of the support, in terms of the balance between ammonia decomposition performance and cost.

The ammonia-containing gas treatment material can be in various shapes. Examples of the shape of the ammonia-containing gas treatment material include spheres, pellets, cylinders, rectangular parallelepipeds, tubes, crushed pieces, honeycombs, and powders.

[Method of manufacturing the treatment material]
The material for treating an ammonia-containing gas is produced by a production method including a step of kneading a compound capable of providing γ-alumina or θ-alumina with a silicate hydrate to obtain a kneaded mixture, a step of molding the kneaded mixture, and a step of firing the molded product at a temperature of 900° C. to 1200° C.

"A compound that gives γ-alumina" means γ-alumina or a compound that produces γ-alumina when fired. Examples of compounds that produce γ-alumina when fired include, but are not limited to, hydroxides such as gibbsite, diaspore, and boehmite, nitrates such as aluminum nitrate, and chlorides such as aluminum chloride. Compounds that produce γ-alumina can be used alone or in combination of two or more. In addition, "a compound that gives θ-alumina" means θ-alumina or a compound that produces θ-alumina when fired. Examples of compounds that produce θ-alumina when fired include, but are not limited to, aluminum hydroxide.

The silicate hydrates added as raw materials are fired to form aluminosilicates. Examples of silicate hydrates include, but are not limited to, kaolin (kaolinite), halloysite, pyrophyllite, imogolite, allophane, etc. In addition, pottery clays such as gage clay, kibushi clay, and Shigaraki clay, which contain these silicate hydrates, may also be used as raw materials. These may be used alone or in combination of two or more types. In addition, it is preferable to use gage clay because it has a high ammonia decomposition ability.

When the above-mentioned raw materials are mixed to obtain a mixture, a solvent such as water or 1,3-butanediol may be added to the mixture in order to ensure the mixing property and subsequent moldability. The mixing can be performed using a commonly used mixer or the like.

As for the mixing ratio of the raw materials, in order to set the content of gamma-alumina in the ammonia-containing gas treatment material to 30 wt% to 70 wt%, preferably 35 wt% to 65 wt%, and more preferably 40 wt% to 60 wt%, the content of the compound that gives gamma-alumina in the solid content of the kneaded product is set to 30 wt% to 70 wt%, preferably 35 wt% to 65 wt%, and more preferably 40 wt% to 60 wt%.

On the other hand, the content of silicate hydrate in the solid content of the kneaded product can be 30 wt% to 70 wt%, preferably 35 wt% to 65 wt%, and more preferably 40 wt% to 60 wt%, depending on the content of gamma-alumina. Note that even when using porcelain clay such as frog's eye clay as the silicate hydrate in the solid content of the kneaded product, the content is the same as above.

The method for forming the kneaded product can be selected appropriately depending on the shape of the treated material to be produced. For example, when the kneaded product is to be formed into a spherical body, a granulator or the like can be used. When the kneaded product is to be formed into a cylindrical, rectangular, tubular, honeycomb or other shape, an extrusion molding machine or the like can be used. After forming the kneaded product, the body may be fired immediately, but from the viewpoint of preventing the occurrence of cracks, etc., it may be dried before firing as necessary.

The molded product is fired at a temperature between 900°C and 1200°C. By firing within this temperature range, it is possible to obtain an ammonia-containing gas treatment material that maintains the specific surface area of gamma-alumina while increasing its strength.

If the firing temperature is less than 900°C, the strength of the ammonia-containing gas treatment material decreases and the shape is easily distorted. On the other hand, if the firing temperature exceeds 1200°C, the γ-alumina undergoes a phase transition to become α-alumina with a corundum structure, and the sintering of alumina progresses, resulting in a decrease in the specific surface area of the ammonia-containing gas treatment material. There are no particular limitations on the firing method, and the firing can be performed using a known firing device. Examples of firing devices that can be used include batch furnaces, tunnel kilns, and rotary kilns.

Next, a metal is supported on the composite thus obtained. First, the composite is impregnated with an aqueous solution containing metal ions. After impregnation, the water adhering to the composite is removed using an evaporator, a centrifugal separator (low speed rotation), etc., and then the composite is fired to support the metal. For example, to support platinum, the composite is impregnated with a hexachloroplatinic acid solution, the water is removed, and the composite is fired at about 500°C for 2 hours.

Moisture can also be removed using a vegetable drainer. It is also effective to remove excess moisture from the surface of the materials by air drying them before firing, such as by blowing hot air on them or placing them in a dryer. In particular, when firing a composite without gradually increasing the firing temperature, air drying beforehand allows for firing with high thermal efficiency.

The removed metal ion-containing aqueous solution can be recovered and reused. The calcined body may be hydrogen-reduced after calcination. Hydrogen reduction can be performed, for example, by passing 10% H ₂ /Ar at 500° C. through the calcined body at 100 mL/min for 2 hours. Hydrogen reduction can be performed, particularly on a catalyst with reduced catalytic activity, to improve the activity.

By passing an ammonia-containing gas through the treatment material obtained by the above manufacturing method, the ammonia in the ammonia-containing gas can be oxidized and decomposed.

[Processing method]
A method for treating an ammonia-containing gas using a treating material will be described. First, the treating material is held in the device as a catalyst layer. The treating material is then heated to a predetermined temperature of 150 to 300°C, and an ammonia-containing gas is passed through the catalyst layer. The amount of the treating material is preferably adjusted according to the decomposition rate determined by the supported metal. In this manner, an ammonia-containing gas is treated, and ammonia can be decomposed at a decomposition rate of 30% or more.

[Example 1]
1.1 Experimental method (1) Sample preparation (preparation of powdered sample)
A composite containing γ-alumina and aluminosilicate was crushed to 180 μm or less in a mortar. Approximately 0.3 g of this was precisely weighed and placed in a recovery flask, and 5.94 ml of distilled water was added. After heating to 90°C, 1.95 ml of 7.72×10 ^-3 mol/l hexachloroplatinic acid solution was added dropwise and stirred for 1 hour while maintaining the temperature at 90°C. After impregnation with the platinum solution, it was evaporated to dryness in an evaporator to prepare a powdered 1 wt% Pt sample.

In addition, 5.85×10 ⁻² mol/l rhodium (III) nitrate, 0.05 mol/l diammine palladium nitrite, and 1.26×10 ⁻² mol/l hexaneammine ruthenium chloride were impregnated into a powder sample in a similar manner. The amount of each was 1 wt % metal.

(2) Ammonia decomposition test (ammonia gas decomposition test using powdered sample)
The following gases were passed through the catalyst layer at temperatures of 100, 200, and 300°C using a catalyst evaluation device made by BELCAT (registered trademark) B made by BEL JAPAN, and the measurements were taken. The sample used was 50 mg. First, the temperature was raised to 100°C at 10°C/min under a flow of He at 50 ml/min, and He was passed through at 50 ml/min for 10 minutes while maintaining the temperature. Next, 5.09% _NH3 /He was passed through at 50 ml/min for 10 minutes to adsorb _NH3 on the sample surface. After that, 50 ml/min He was passed through for 5 minutes to discharge _NH3 gas in the analysis tube, and then 5.08% _O2 /He gas was passed through the catalyst layer at 50 ml/min for 10 minutes to react with _NH3 on the sample surface. In the same manner, a decomposition test was performed under conditions in which the temperature of the catalyst layer was set to 200°C and 300°C. The gas composition was analyzed by measuring the ion intensity of each component using an online gas analyzer BELMASS manufactured by BEL JAPAN.

1.2 Results and Observations After NH ₃ /He was adsorbed on the prepared 1 wt % Pt-supported sample, O ₂ /He was passed through the sample to attempt decomposition of ammonia by oxidation. Generally, the decomposition of ammonia proceeds as follows.
_4NH3 + _3O2 → _2N2 + _6H2O ...(1-1)
_4NH3 + _5O2 →4NO+ _6H2O ...(1-2)
_4NH3 + _7O2 → _4NO2 + _6H2O ...(1-3)

Therefore, it is known that the decomposition reaction produces N ₂ , NO, NO ₂ , and H ₂ O. Therefore, the ion intensity changes of m/z = 28 (N ₂ ), m/z = 30 (NO), m/z = 44 (N ₂ O), and m/z = 46 (NO ₂ ) were measured using online gas analysis.

1(a) to (d) are graphs showing the time-dependent changes in ion intensity for _N2 , NO, _N2O and _NO2 gases at 100, 200 and 300° C. In (a), the ion intensity of _N2 (m/z=28) peaked immediately after switching to _O2 /He at reaction temperatures of 200° C. and 300° C., confirming that _N2 was generated by the reaction of _NH3 adsorbed on the sample surface with _O2 .

In addition, the ion intensity of NO ₂ (m/z=46) in Fig. 1(d) showed a peak immediately after switching to O ₂ /He at a reaction temperature of 300°C. It is suggested that at a reaction temperature of 200°C, NH ₃ adsorbed on the sample surface produces N ₂ by the reaction of formula (1-1) above, and at a reaction temperature of 300°C, the production of N ₂ by formula (1-1) and NO ₂ by formula (1-3) proceed simultaneously.

2(a) to (d) are graphs showing the results of measuring the change in ion intensity of N2 (m/z=28) when _NH3 /He gas and _O2 /He gas were alternately passed through samples carrying ₁ wt% Pt, Pd, and Rh, respectively, and a sample carrying no metal, and the reaction temperatures were set to 100, 200, and 300° C. For Pt, Pd, and Rh, peaks appeared at reaction temperatures of 200° C. or higher, and the generation of _N2 was confirmed, whereas _{no N2} peak appeared in the sample carrying no metal.

[Example 2]
2.1 Experimental method (1) Sample preparation 20 g of a composite containing γ-alumina and aluminosilicate was placed in a recovery flask, and a hexachloroplatinic acid solution was added dropwise and stirred for 1 hour while maintaining the temperature at 90°C. After impregnation with the solution, the material was evaporated to dryness in an evaporator to obtain a support. Then, the material was fired at 500°C for 2 hours to prepare a 0.1 wt% Pt-supported sample.

Metal-loaded samples were prepared in a similar manner using nickel nitrate, rhodium(III) nitrate, hexachloroplatinic acid solution, hexaammineruthenium chloride, diamminepalladium nitrite and copper sulfate solutions.

(2) Ammonia decomposition test Fig. 3 is a schematic diagram of an experimental apparatus 1 used in an ammonia decomposition test. 20 g of a sample 13 sandwiched between quartz wool 15 was placed in a quartz glass tube 11 with an inner diameter of 31 mm and a length of 400 mm to form a catalyst layer 16 with a length of 50 mm (volume 37.7 ^cm3 ). The quartz glass tube 11 was placed in a tubular electric furnace 17, and the catalyst layer temperature was adjusted.

The ammonia-containing gas was generated by placing 300 ml of 2.8% ammonia water in a 900 ml glass container 40 and supplying air using an air compressor 20. The air flow rate was adjusted to a range of 100 to 1000 ml/min using a mass flow controller 30. The flow-controlled air was bubbled into the ammonia water to pass the ammonia-containing gas through the catalyst layer. A three-way cock 50 was provided at the inlet of the catalyst layer and used to evaluate the concentration on the inlet side of the catalyst layer 16 (Inlet). The gas that had passed through the catalyst layer was bubbled for 10 minutes in a measuring cylinder 60 containing 250 ml of distilled water, and the ammonia concentration in the solution was analyzed (Outlet).

(3) Evaluation of Ammonia Concentration The ammonia concentration was measured by the spectrophotometric method according to JIS K 0400-42-60: 2000. The ammonia decomposition rate was calculated from the change in ammonia gas concentration before and after passing through the catalyst layer.

(a) Preparation of sample for absorbance measurement (preparation of color-developing reagent)
13.0 g of sodium salicylate and 13.0 g of trisodium citrate dihydrate were dissolved in a small amount of distilled water, and then sodium pentacyanonitrosylferrate (III) dihydrate that had been ground in a mortar was added, and the solution was diluted to 100 ml using a measuring flask.

(Preparation of sodium dichloroisocyanurate solution)
3.2 g of sodium hydroxide was dissolved in a small amount of distilled water, and then 0.2 g of sodium dichloroisocyanurate dihydrate was added thereto, and the solution was diluted to 100 ml using a measuring flask.

(Preparation of standard solutions)
0.3819 g of ammonium chloride was dissolved in a small amount of distilled water and then diluted to 100 ml using a measuring flask to prepare a 1000 ppm ammonium nitrogen standard solution. Based on the prepared 1000 ppm ammonium nitrogen standard solution, a 100 ppm ammonium nitrogen standard solution and a 1 ppm ammonium nitrogen standard solution were prepared.

(b) Absorbance measurement 1 ml of the sample solution in which ammonia gas had been collected was diluted to 100 ml, and 40 ml of this solution was placed in a 50 ml measuring flask. 4 ml each of a color-developing reagent and sodium dichloroisocyanurate solution were added, and the total volume was adjusted to 50 ml. The solution was then left to stand for 10 minutes to develop color, and the ammonia concentration was measured using an absorptiometer.

Ｃｏｎｖｅｒｓｉｏｎ：アンモニア分解率
Ｃ_{ｉｎｌｅｔ}：触媒層通過前のガス中のアンモニア濃度
Ｃ_{ｏｕｔｌｅｔ}：触媒層通過後のガス中のアンモニア濃度 The ammonia decomposition rate was calculated from the following formula.

Conversion: ammonia decomposition rate C _inlet : ammonia concentration in the gas before passing through the catalyst layer C _outlet : ammonia concentration in the gas after passing through the catalyst layer

2.2 Results (1) Ammonia decomposition performance of various metal-supported samples FIG. 4 shows the results of an ammonia decomposition test using samples supporting 0.1 wt % of various metals under conditions set at a catalyst layer temperature of 250° C. and an air supply rate of 100 ml/min.

It was confirmed that samples carrying Pd, Ru, and Pt achieved an ammonia decomposition rate of 90% over a 24-hour period. It was also revealed that samples carrying inexpensive metals such as Ni and Cu decomposed approximately 30% of the ammonia after 24 hours. On the other hand, samples not carrying metals showed almost no ammonia decomposition.

Figure 5 shows the ammonia decomposition rate of Pt and 0.1 wt% Pd supported samples when the air supply volume (SV) was fixed at 100 ml/min and the reaction temperature was changed from 100 to 450°C. With the Pt supported catalyst, a decomposition rate of 95% was achieved even when the temperature was changed. With the Pd supported catalyst, the decomposition rate decreased at reaction temperatures below 200°C, but it was confirmed that a certain amount of ammonia could be decomposed.

Figures 6(a) and (b) show the ammonia decomposition rates of samples carrying 0.1 wt% Pt and Pd when the reaction temperature was fixed at 250°C and the air supply volume (SV) was changed from 100 to 500 ml/min. In this test, the ammonia water was replaced every 24 hours after 48 hours from the start of the reaction.

With the Pt-supported sample, a decomposition rate of 90% was achieved even when the air supply rate was changed. With the Pd-supported sample, the decomposition rate dropped to 73% when the air supply rate was 500 ml/min, but it was confirmed that the ammonia decomposition rate rose to 93% by returning the air supply rate to 100 ml/min.

Figure 7 shows the ammonia decomposition rate when the reaction temperature was fixed at 250°C, the air supply rate was fixed at 100 ml/min, and the Pt loading amount was changed from 0 to 0.1%. It was confirmed that an ammonia decomposition rate of over 90% was achieved even with a loading amount of 0.001 wt%. On the other hand, there was almost no ammonia decomposition in the sample without Pt loading.

Reference Signs List 1 Experimental apparatus 11 Quartz glass tube 13 Sample 15 Quartz wool 16 Catalyst layer 17 Tubular electric furnace 20 Air compressor 30 Mass flow controller 40 Glass container 50 Three-way cock 60 Measuring cylinder

Claims (6)

Heating the catalyst layer to 150° C. or more and 300° C. or less;
and passing an ammonia-containing gas through the heated catalyst bed to oxidatively decompose the ammonia into nitrogen gas and water.
The catalyst layer is formed using a treatment material including a composite containing γ-alumina or θ-alumina and an aluminosilicate, and a metal supported by the composite ,
The method for treating an ammonia-containing gas, wherein the metal is one or a combination of a plurality of metals selected from the group consisting of platinum, palladium, ruthenium, nickel, rhodium and copper. Heating the catalyst layer to 150° C. or more and 300° C. or less;
and passing an ammonia-containing gas through the heated catalyst bed to oxidatively decompose the ammonia into nitrogen gas and water.
The catalyst layer is formed using a treatment material including a composite containing γ-alumina or θ-alumina and an aluminosilicate, and a metal supported by the composite ,
The method for treating an ammonia-containing gas, wherein the metal is present in an amount of 0.001 wt % or more and 0.1 wt % or less relative to the composite . a composite comprising gamma-alumina and an aluminosilicate;
A metal supported by the composite,
The material for treating an ammonia-containing gas is characterized in that the metal is one or a combination of a plurality of metals selected from the group consisting of platinum, palladium, ruthenium, nickel, rhodium and copper . a composite comprising gamma-alumina and an aluminosilicate;
A metal supported by the composite,
The material for treating an ammonia-containing gas, wherein the metal is present in an amount of 0.001 wt % or more and 0.1 wt % or less relative to the composite. a step of kneading γ-alumina and a silicate hydrate so that the content of the γ-alumina is 30 wt % or more and 70 wt % or less to obtain a kneaded product;
A step of molding the kneaded product;
A step of firing the molded body obtained by the molding at 900 ° C. or more and 1200 ° C. or less;
and supporting, on the fired body obtained by the firing, one or a combination of metals selected from the group consisting of platinum, palladium, ruthenium, nickel, rhodium and copper . a step of kneading γ-alumina and a silicate hydrate so that the content of the γ-alumina is 30 wt % or more and 70 wt % or less to obtain a kneaded product;
A step of molding the kneaded product;
A step of firing the molded body obtained by the molding at 900 ° C. or more and 1200 ° C. or less;
and supporting a metal of 0.001 wt % or more and 0.1 wt % or less on the fired body obtained by the firing.

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