Ammonia generation catalyst for reducing nitrogen oxides and method for producing ammonia

Abstract

To provide an ammonia generation catalyst for reducing nitrogen oxides that achieves high selectivity of ammonia during production of ammonia from nitrogen oxides.SOLUTION: An ammonia generation catalyst for reducing nitrogen oxides contains a support and a nickel element supported on the support, the support containing cerium oxide, and the nitrogen oxide reduction catalyst including at least one element A selected from the group consisting of an alkali metal and an alkaline earth metal, the element A being supported on the support.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to nitrogen oxide reduction catalysts for the production of ammonia and methods for producing ammonia. [Background technology]

[0002] From the perspective of preventing environmental pollution, methods are being investigated for treating and neutralizing nitrogen oxides (NOx), such as nitric oxide and nitrogen dioxide, contained in exhaust gases. One known method for treating nitrogen oxides is to reduce them to molecular nitrogen using a reducing agent. However, it is difficult to effectively utilize the resulting molecular nitrogen. In recent years, with growing interest in the Sustainable Development Goals (SDGs), there has been a demand for producing substances that can be effectively utilized from nitrogen oxides. One example of such a substance is ammonia. As a supported catalyst for synthesizing ammonia (NH3) from nitrogen oxide, nitric oxide (NO), Patent Document 1 discloses a catalyst for synthesizing ammonia from nitrogen oxide, which catalyst has cerium oxide and copper supported on the cerium oxide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-007043 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, there have been only a limited number of reports on supported catalysts for synthesizing ammonia (NH3) from nitric oxide (NO). The inventors conducted research and found that a catalyst containing cerium oxide and nickel supported on cerium oxide could be used as a supported catalyst for synthesizing ammonia from nitrogen oxides. Further research revealed that this catalyst had low ammonia selectivity when producing ammonia from the raw material nitrogen oxides.

[0005] The present disclosure has been made in consideration of the above circumstances and provides a nitrogen oxide reduction catalyst for producing ammonia, which has a high ammonia selectivity when producing ammonia from nitrogen oxides. The present disclosure also provides a method for producing ammonia, which has a high ammonia selectivity. [Means for solving the problem]

[0006] The present disclosure provides: A nitrogen oxide reduction catalyst for producing ammonia, comprising a support and elemental nickel supported on the support, the support comprises cerium oxide; The present invention relates to a nitrogen oxide reduction catalyst for producing ammonia, wherein the nitrogen oxide reduction catalyst contains one or more elements A selected from the group consisting of alkali metals and alkaline earth metals, supported on the support.

[0007] The present disclosure also provides: A method for producing ammonia, comprising: a preparation step of preparing a nitrogen oxide reduction catalyst for producing ammonia according to the present disclosure; a contacting step A in which a gas containing nitrogen oxides is contacted with the nitrogen oxide reduction catalyst; a contacting step B in which the nitrogen oxide reducing catalyst having been contacted with the nitrogen oxide-containing gas is contacted with water vapor and a gas containing carbon monoxide; The present invention relates to a method for producing ammonia, comprising the steps of: [Effects of the Invention]

[0008] According to the present disclosure, there is provided a nitrogen oxide reduction catalyst for producing ammonia, which has high ammonia selectivity when producing ammonia from nitrogen oxides. Also, according to the present disclosure, there is provided a method for producing ammonia, which has high ammonia selectivity. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a graph showing the experimental results of Examples 1 to 6 and Comparative Example 1. [Figure 2] 1 is a graph showing the experimental results of Examples 1 to 6 and Comparative Example 1. [Figure 3] 1 is a graph showing the experimental results of Examples 1 to 6 and Comparative Example 1. [Figure 4] 1 is a graph showing experimental results according to Examples 1 and 7 to 12 and Comparative Example 1. [Figure 5] 1 is a graph showing experimental results according to Examples 1 and 7 to 12 and Comparative Example 1. [Figure 6] 1 is a graph showing experimental results according to Examples 1 and 7 to 12 and Comparative Example 1. [Figure 7] 1 is a graph showing the experimental results of Examples 10 and 13 to 16. [Figure 8] 1 is a graph showing the experimental results of Examples 10 and 13 to 16. [Figure 9] 1 is a graph showing the experimental results of Examples 10 and 13 to 16. [Figure 10] 1 is a graph showing experimental results according to Examples 10 and 17 and Comparative Example 2. [Figure 11] 1 is a graph showing experimental results according to Examples 10 and 17 and Comparative Example 2. [Figure 12] 1 is a graph showing experimental results according to Examples 10 and 17 and Comparative Example 2. [Figure 13] FIG. 1 is an explanatory diagram showing the measurement results of a reaction intermediate. DETAILED DESCRIPTION OF THE INVENTION

[0010] The catalyst and ammonia production method of the present disclosure will be described below based on embodiments and examples. The expressions "XX or more and YY or less" and "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined arbitrarily. Further, redundant explanations will be omitted as appropriate.

[0011] The nitrogen oxide reduction catalyst for producing ammonia according to the present disclosure is a nitrogen oxide reduction catalyst for producing ammonia that includes a support and elemental nickel supported on the support, wherein the support includes cerium oxide, and the nitrogen oxide reduction catalyst includes one or more elements A selected from the group consisting of alkali metals and alkaline earth metals that are supported on the support. With this configuration, the nitrogen oxide reduction catalyst for producing ammonia has a high ammonia selectivity when producing ammonia from nitrogen oxides. In this disclosure, the term "nitrogen oxide reduction catalyst" refers to a catalyst capable of reducing nitrogen oxides (NOx), such as nitrogen monoxide and nitrogen dioxide. For example, a nitrogen oxide reduction catalyst for producing ammonia can synthesize ammonia from nitrogen oxides, water vapor, and carbon monoxide. Nitrogen oxides (NO x ) include NO, NO2, NO3, N2O3 (NO 1.5 ), N2O4(NO2), N2O5(NO 2.5 These nitrogen oxides can be used alone or in combination of two or more.

[0012] As described above, the nitrogen oxide reduction catalyst includes a support. The support includes cerium oxide. When nitrogen oxides are reduced, cerium oxide exhibits strong electron donating properties to the catalytic metal due to partial reduction of the cerium oxide, and also serves as a site for the reaction intermediate. The support is preferably a ceria support. The support may include other oxide supports. Examples of other oxide supports include alumina supports, silica supports, titania supports, zirconia supports, and magnesia supports.

[0013] The nitrogen oxide reduction catalyst contains elemental nickel supported on a carrier. The elemental nickel activates and dissociates nitrogen oxides, and also serves as a site for the reaction between the adsorbed nitrogen species produced by the dissociation and carbon monoxide, and as a site for the existence of reaction intermediates. The reaction intermediates produced during this reaction are hydrolyzed by water vapor to produce ammonia. The form in which the nitrogen oxide reduction catalyst contains elemental nickel is not particularly limited, and examples include nickel oxide, hydroxide, nitrate, carbonate, etc.

[0014] The content of elemental nickel in the nitrogen oxide reduction catalyst is not particularly limited, but is preferably 1.0 to 11.0 mass%. Furthermore, from the viewpoint of easily increasing the yield of ammonia, the content of elemental nickel is more preferably 2.5 to 10.0 mass%, further preferably 2.5 to 7.5 mass%, and particularly preferably 4.0 to 6.0 mass%. As the content of elemental nickel increases, the reaction temperature tends to decrease. On the other hand, as the content of elemental nickel decreases, the reaction temperature tends to increase. The nickel content in the nitrogen oxide reduction catalyst can be measured by XRF (X-ray fluorescence analysis) method.

[0015] The nitrogen oxide reduction catalyst contains one or more elements A selected from the group consisting of alkali metals and alkaline earth metals, supported on a support. Element A has high electron donating properties. Therefore, it is believed that electron donation to nickel facilitates the progress of the reduction reaction of nitrogen oxides, facilitating the production of ammonia. In other words, when the nitrogen oxide reduction catalyst contains a support containing cerium oxide, nickel supported on the support, and element A supported on the support, it becomes a nitrogen oxide reduction catalyst for producing ammonia that has a high ammonia selectivity when producing ammonia from nitrogen oxides. Here, high ammonia selectivity means that the ammonia yield is high relative to the nitrogen oxide conversion rate. In this case, the amount of by-products produced during ammonia production is reduced. Examples of by-products include nitrous oxide.

[0016] The alkali metal may be one or more elements selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and francium. Of these, one or more elements selected from the group consisting of lithium, sodium, potassium, and cesium are preferred, and sodium is more preferred. The alkaline earth metal may be one or more elements selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, and radon, and among these, one or more elements selected from the group consisting of calcium and barium are preferred.

[0017] The content of element A in the nitrogen oxide reduction catalyst for producing ammonia is not particularly limited, but is preferably 0.5 to 22.0 mass%, more preferably 3.0 to 22.0 mass%, and even more preferably 4.5 to 22.0 mass%. By keeping the content within the above range, the ammonia selectivity tends to be higher. Furthermore, the ammonia yield tends to be higher. Furthermore, from the viewpoint of further increasing the ammonia yield, the content is preferably 9.0 to 22.0 mass%, more preferably 9.0 to 16.0 mass%, and particularly preferably 11.0 to 13.0 mass%.

[0018] Furthermore, the content of element A in the nitrogen oxide reduction catalyst relative to 100 parts by mass of nickel element is not particularly limited, but is preferably 10 to 440 parts by mass, more preferably 60 to 440 parts by mass, and even more preferably 90 to 440 parts by mass. By being in the above range, the ammonia selectivity tends to be higher. Also, the ammonia yield tends to be higher. Furthermore, from the viewpoint of further increasing the ammonia yield, it is preferably 180 to 440 parts by mass, more preferably 180 to 320 parts by mass, and particularly preferably 220 to 260 parts by mass. The content of element A can be measured by XRF (X-ray fluorescence analysis) method.

[0019] The nitrogen oxide reduction catalyst may contain element A in any form, including, for example, oxide, hydroxide, nitrate, carbonate, and the like.

[0020] As described above, the nitrogen oxide reduction catalyst of the present disclosure can function as a nitrogen oxide reduction catalyst even in an embodiment that does not contain a precious metal. Therefore, it is preferable that the nitrogen oxide reduction catalyst does not contain a precious metal. Precious metals include gold, silver, platinum, palladium, rhodium, iridium, ruthenium, and osmium.

[0021] The nitrogen oxide reduction catalyst may contain inevitable impurities to the extent that the synthesis of ammonia from nitrogen oxides is not hindered. Inevitable impurities are impurities that cannot be avoided during production. The content of inevitable impurities in the nitrogen oxide reduction catalyst is 1 mass% or less. In other words, it is preferable that the nitrogen oxide reduction catalyst for producing ammonia essentially consists of a carrier containing cerium oxide, nickel element supported on the carrier, and one or more elements A selected from the group consisting of alkali metals and alkaline earth metals supported on the carrier. Here, "consisting essentially of only" means that in addition to the carrier, elemental nickel, and element A, trace amounts of other impurities (for example, 5% by mass or less of the nitrogen oxide reduction catalyst) are permitted to be mixed in.

[0022] <Ammonia manufacturing method> The method for producing ammonia includes a preparation step of preparing the nitrogen oxide reduction catalyst for producing ammonia of the present disclosure, a contact step A of bringing a gas containing nitrogen oxides into contact with the nitrogen oxide reduction catalyst for producing ammonia, and a contact step B of bringing water vapor and a gas containing carbon monoxide into contact with the nitrogen oxide reduction catalyst for producing ammonia that has been contacted with the gas containing nitrogen oxides. By using the nitrogen oxide reduction catalyst of the present disclosure, ammonia can be produced with high selectivity.

[0023] The process for preparing the nitrogen oxide reduction catalyst is not particularly limited, and the catalyst can be produced based on a known method for producing a nitrogen oxide reduction catalyst, for example, based on the production method described in the Examples of this specification. For example, the method for producing a nitrogen oxide reduction catalyst preferably includes a dispersion step of dispersing a carrier in an alkaline aqueous solution. It also preferably includes a step of removing water from the dispersion obtained in the dispersion step to obtain a solid. It also preferably includes a sintering step of sintering the solid to obtain a sintered product. Additionally, it preferably includes a reduction step of reducing the sintered product. It is more preferable that the above steps are performed in this order.

[0024] The dispersion step is a step of dispersing the support in an alkaline aqueous solution. The support contains cerium oxide. If necessary, the alkaline aqueous solution may be stirred. The content of the carrier in the alkaline aqueous solution is not particularly limited, but may be 1 to 10 parts by mass, or may be 1 to 5 parts by mass, relative to 100 parts by mass of water.

[0025] The alkaline aqueous solution contains, for example, water and a hydroxide salt. The hydroxide salt is not particularly limited, and examples thereof include hydroxides of alkali metals and hydroxides of alkaline earth metals. More specifically, the hydroxide salt may contain one or more selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and cesium hydroxide. By using such a hydroxide salt, element A can be contained in the nitrogen oxide reduction catalyst. The content of the hydroxide salt in the alkaline aqueous solution is not particularly limited, but may be, for example, 0.010 to 1.000 parts by mass, and more preferably 0.300 to 0.600 parts by mass, per 100 parts by mass of water. It is preferable that the amount is parts by weight.

[0026] The alkaline aqueous solution preferably contains a nickel source such as nickel carbonate, nickel nitrate, nickel acetate, etc. When the alkaline aqueous solution contains a nickel source and the sintering step described below is carried out, elemental nickel is supported on the support. When the alkaline aqueous solution contains a nickel source, the alkaline aqueous solution used in the dispersion step contains an alkali, a nickel source, and a support. When the alkali contains a hydroxide salt, elements derived from the hydroxide salt, nickel element, and the support are present in the alkaline aqueous solution. This allows the elements derived from the hydroxide salt and nickel element to be more uniformly supported on the support. As a result, catalytic activity is likely to be improved. One reason for this is that the elements derived from the hydroxide salt quickly capture carbon monoxide and increase the opportunities for supplying it to nickel element. The content of the nickel source in the alkaline aqueous solution is not particularly limited, but may be, for example, 0.080 to 1.000 parts by mass, or 0.200 to 0.800 parts by mass, relative to 100 parts by mass of water.

[0027] The temperature in the dispersing step is not particularly limited, but may be, for example, 10 to 30° C. The time for the dispersing step is not particularly limited, but may be, for example, 10 minutes to 1 hour.

[0028] The step of removing water from the dispersion obtained in the dispersion step to obtain a solid is not particularly limited, but an example is a method of drying the dispersion. For drying, for example, a rotary evaporator can be used. The drying temperature is not particularly limited, but can be, for example, 30 to 60°C. The drying time is not particularly limited, but can be, for example, 1 to 5 hours.

[0029] The method for producing a nitrogen oxide reduction catalyst may further include an addition step of adding a nickel source such as nickel carbonate, nickel nitrate, or nickel acetate to the solid obtained in the solid obtaining step. By adding the nickel source to the solid and then carrying out the sintering step described below, elemental nickel is supported on the support.

[0030] The sintering step is a step of sintering the solid obtained in the solid obtaining step or the solid obtained in the addition step to obtain a sintered product. The sintering conditions are not particularly limited, but are preferably, for example, 400 to 600° C. and 3 to 5 hours. The sintering atmosphere is not particularly limited, but is preferably air.

[0031] The reduction step is a step of reducing the sintered product. The reduction conditions are not particularly limited, but are preferably, for example, 400 to 600°C and 0.5 to 2 hours. The reduction atmosphere is not particularly limited as long as it is a reducing gas, but is preferably an H2 gas atmosphere. For example, a mixed gas of H2 and N2 may be used.

[0032] In the contact step A, a gas containing nitrogen oxides such as nitric oxide and nitrogen dioxide is contacted with the nitrogen oxide reduction catalyst. The nitrogen oxides used are not particularly limited, and nitrogen oxides directly recovered from the atmosphere or exhaust gases can also be used. The exhaust gas is not particularly limited in terms of its source or components contained therein, as long as it contains nitrogen oxides; for example, exhaust gas produced by waste incineration can be used.

[0033] The concentration of nitrogen oxide in the gas is not particularly limited, but may be, for example, 0.01 to 10.0% by volume, 0.05 to 5.0% by volume, or 0.05 to 1.0% by volume. The temperature in the contact step A is not particularly limited, but is preferably 100 to 600°C, more preferably 200 to 550°C, and even more preferably 300 to 550°C.

[0034] In the contacting step B, a gas containing water vapor and carbon monoxide is brought into contact with the nitrogen oxide reducing catalyst that has been contacted with a gas containing nitrogen oxides, to obtain ammonia. The water vapor and carbon monoxide act as reducing agents. The method for contacting the gas with the nitrogen oxide reduction catalyst is not particularly limited, and any known method can be used. In addition, the contacting step A and the contacting step B may be carried out simultaneously. For example, a gas containing nitrogen oxides, water vapor, and carbon monoxide may be contacted with the nitrogen oxide reduction catalyst.

[0035] The concentration of water vapor in the gas is not particularly limited, but may be, for example, 0.1 to 10.0% by volume, 0.5 to 5.0% by volume, or 0.5 to 2.0% by volume. Furthermore, the concentration of carbon monoxide in the gas is not particularly limited, but may be, for example, 0.03 to 10.0% by volume, 0.1 to 5.0% by volume, or 0.1 to 3.0% by volume.

[0036] The temperature in the contact step B is not particularly limited, but is preferably 100 to 500° C., more preferably 200 to 400° C. When the temperature is within the above range, ammonia can be synthesized more efficiently. [Example]

[0037] The present invention will be explained in more detail below with reference to examples, but is not limited to these examples as long as they do not depart from the gist of the invention.

[0038] Example 1 An aqueous solution was obtained by dissolving 0.45 g of nickel acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 0.185 g of sodium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 100 mL of ion-exchanged water. The aqueous solution was then sonicated for 20 minutes at room temperature (20°C) using an ASU-20 (360 W, 40 kHz) (manufactured by AS ONE Corporation). 2 g of cerium oxide (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was then added to the sonicated aqueous solution to obtain a slurry. This slurry was then dried in a rotary evaporator at 40°C for 3 hours to obtain a solid.

[0039] The obtained solid was calcined in air at 500°C for 4 hours, and then heated at 50°C under a 10% hydrogen / nitrogen stream. A 5 mass% Ni-5 mass% Na / CeO2 catalyst was obtained by reduction at 0°C for 1 hour. Here, the expression 5 mass% Ni-5 mass% Na / CeO2 indicates that the content of elemental nickel in the nitrogen oxide reduction catalyst is 5 mass%, the content of elemental sodium in the nitrogen oxide reduction catalyst is 5 mass%, and the elemental nickel and elemental sodium are supported on the ceria support.

[0040] <Examples 2 to 6> Nitrogen oxide reduction catalysts according to Examples 2 to 6 were obtained in the same manner as in Example 1, except that the 0.185 g of sodium hydroxide used in Example 1 was replaced with 0.65 g of lithium hydroxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 0.153 g of potassium hydroxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 0.155 g of cesium hydroxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 0.245 g of barium hydroxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and 0.2 g of calcium hydroxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.). The nitrogen oxide reduction catalysts according to Examples 2 to 6 were a 5 mass% Ni-5 mass% Li / CeO catalyst, a 5 mass% Ni-5 mass% K / CeO catalyst, a 5 mass% Ni-5 mass% Cs / CeO catalyst, a 5 mass% Ni-5 mass% Ba / CeO catalyst, and a 5 mass% Ni-5 mass% Ca / CeO catalyst, respectively.

[0041] <Examples 7 to 12> Nitrogen oxide reducing catalysts according to Examples 7 to 12 were obtained in the same manner as in Example 1, except that the 0.185 g of sodium hydroxide used in Example 1 was replaced with 0.037 g, 0.074 g, 0.390 g, 0.500 g, 0.610 g, and 0.88 g of sodium hydroxide, respectively. The nitrogen oxide reducing catalysts according to Examples 7 to 12 were a 5 mass% Ni-1 mass% Na / CeO2 catalyst, a 5 mass% Ni-2 mass% Na / CeO2 catalyst, a 5 mass% Ni-10 mass% Na / CeO2 catalyst, a 5 mass% Ni-12 mass% Na / CeO2 catalyst, a 5 mass% Ni-15 mass% Na / CeO2 catalyst, and a 5 mass% Ni-20 mass% Na / CeO2 catalyst, respectively.

[0042] <Comparative Example 1> A nitrogen oxide reducing catalyst was obtained in the same manner as in Example 1, except that 0.185 g of sodium hydroxide used in Example 1 was not used. The nitrogen oxide reducing catalyst of Comparative Example 1 was a 5 mass % Ni / CeO2 catalyst.

[0043] <Examples 13 to 16> The nitrogen oxide reducing catalysts of Examples 13 to 16 were obtained in the same manner as in Example 1, except that the 0.45 g of nickel acetate and 0.185 g of sodium hydroxide used in Example 1 were replaced with 0.095 g of nickel acetate and 0.39 g of sodium hydroxide, 0.095 g of nickel acetate and 0.5 g of sodium hydroxide, 0.950 g of nickel acetate and 0.39 g of sodium hydroxide, and 0.950 g of nickel acetate and 0.5 g of sodium hydroxide, respectively. The nitrogen oxide reducing catalysts of Examples 13 to 16 were a 1 mass% Ni-10 mass% Na / CeO2 catalyst, a 1 mass% Ni-12 mass% Na / CeO2 catalyst, a 10 mass% Ni-10 mass% Na / CeO2 catalyst, and a 10 mass% Ni-12 mass% Na / CeO2 catalyst, respectively.

[0044] Example 17 An aqueous solution was prepared by dissolving 0.500 g of sodium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 100 mL of ion-exchanged water. The aqueous solution was then ultrasonicated for 20 minutes at room temperature (20°C) using an ASU-20 (360 W, 40 kHz) (manufactured by AS ONE Corporation). 2 g of cerium oxide (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was then added to the ultrasonically treated aqueous solution to obtain a slurry. This slurry was then dried in a rotary evaporator at 40°C for 3 hours to obtain a solid. To the obtained solid, 0.45 g of nickel acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was further added to prepare a mixture. The obtained mixture was calcined in air at 500°C for 4 hours, and then reduced in a 10% hydrogen / nitrogen stream at 500°C for 1 hour to obtain 5 mass% Ni-12 mass% Na / CeO Two catalysts were obtained.

[0045] <Comparative Example 2> Except for not using nickel acetate, a nitrogen oxide reducing catalyst was obtained in the same manner as in Example 10. The nitrogen oxide reducing catalyst of Comparative Example 2 was a 12 mass % Na / CeO2 catalyst.

[0046] <Catalytic activity evaluation> Ammonia was synthesized in the following manner using the nitrogen oxide reduction catalysts of Examples 1 to 17 and Comparative Examples 1 and 2. A fixed-bed reactor was used for the experiments. 0.15 g of nitrogen oxide reduction catalyst was placed in a quartz tube in an electric furnace. Prior to measurement, the catalyst was pretreated at 500°C for 30 minutes in a mixed gas atmosphere (composition: 0.1% by volume of nitrogen monoxide, 0.3% by volume of carbon monoxide, 1.0% by volume of water vapor, the remainder being argon). A mixture of argon and nitrous oxide was supplied to the reactor at a flow rate of 250 mL / min at 500°C for 6 minutes. After the mixed gas was supplied, the reaction was carried out at a predetermined temperature for 6 minutes, and the yield of ammonia and the yield of nitrous oxide, a by-product, were measured using an FT-IR equipped with a gas cell. The conversion rate of nitric oxide was also measured in the same manner as the ammonia yield. The results are shown in Figures 1 to 12. In Figures 1, 4, 7, and 10, the vertical axis represents the conversion rate of nitric oxide. In Figures 2, 5, 8, and 11, the vertical axis represents the ammonia yield. In Figures 3, 6, 9, and 12, the vertical axis represents the nitrous oxide yield.

[0047] In Figures 1 to 3, "No additive" indicates the evaluation results of Comparative Example 1, Li indicates the evaluation results of Example 2, Na indicates the evaluation results of Example 1, K indicates the evaluation results of Example 3, Cs indicates the evaluation results of Example 4, Ba indicates the evaluation results of Example 5, and Ca indicates the evaluation results of Example 6. 4 to 6, 0Na indicates the evaluation result of Comparative Example 1, 1Na indicates the evaluation result of Example 7, 2Na indicates the evaluation result of Example 8, 5Na indicates the evaluation result of Example 1, 10Na indicates the evaluation result of Example 9, 12Na indicates the evaluation result of Example 10, 15Na indicates the evaluation result of Example 11, and 20Na indicates the evaluation result of Example 12. Furthermore, in Figures 7 to 9, 5Ni12Na / CeO2 shows the evaluation results of Example 10, 1Ni10Na / CeO2 shows the evaluation results of Example 13, 1Ni12Na / CeO2 shows the evaluation results of Example 14, 10Ni10Na / CeO2 shows the evaluation results of Example 15, and 10Ni12Na / CeO2 shows the evaluation results of Example 16. 10 to 12, 5Ni12Na / CeO2 indicates the evaluation results of Example 10, 5Ni / 12Na / CeO2 indicates the evaluation results of Example 17, and 12Na / CeO2 indicates the evaluation results of Comparative Example 2, respectively.

[0048] <Measurement of reaction intermediates> Fig. 13 is an explanatory diagram showing the measurement results of a reaction intermediate, and is the result of FT-IR measurement of the reaction intermediate. The nitrogen oxide reduction catalysts of Example 10 and Comparative Example 1 were evaluated and FT-IR measurement results were obtained using the same method as the catalytic activity evaluation method described above, except that water vapor was not used and the supply condition was 250°C. In Fig. 13, 5Ni12Na / CeO2 is the result using the nitrogen oxide reduction catalyst of Example 10 (hereinafter also referred to as the upper result), and 5Ni / CeO2 is the result using the nitrogen oxide reduction catalyst of Comparative Example 1 (hereinafter also referred to as the lower result). In measuring the reaction intermediates, water vapor was not used, so the reaction of ammonia production stopped midway. NCO is a reaction intermediate produced when ammonia is produced from nitrogen oxides, and Ni 0 -CO indicates CO adsorbed on the catalyst surface, and Ni 0 -NO indicates NO adsorbed on the catalyst surface. In the results shown in the lower row, which does not contain element A, peaks for NO and CO adsorbed on the catalyst surface are present, but in the results shown in the upper row, which does contain element A, these peaks are absent and only a peak for NCO, a reaction intermediate, is confirmed. In other words, it is thought that when the nitrogen oxide reduction catalyst contains element A supported on a carrier, the decomposition rate of NO increases, making it easier to produce NCO, and ultimately making it easier to produce ammonia.

[0049] Examples of the inventions that have been understood from the above disclosure are as follows. [1] A nitrogen oxide reduction catalyst for producing ammonia, comprising a support and nickel element supported on the support, the support comprises cerium oxide; The nitrogen oxide reduction catalyst for producing ammonia, wherein the nitrogen oxide reduction catalyst comprises one or more elements A selected from the group consisting of alkali metals and alkaline earth metals, supported on the support. [2] The nitrogen oxide reduction catalyst for producing ammonia according to [1], wherein the element A is one or more elements selected from the group consisting of lithium, sodium, potassium, calcium, barium, and cesium. [3] The nitrogen oxide reduction catalyst for producing ammonia according to [2], wherein the element A is sodium. [4] The nitrogen oxide reduction catalyst for producing ammonia according to any one of [1] to [3], wherein the content of the element A in the nitrogen oxide reduction catalyst for producing ammonia is 0.5 to 22.0 mass %. [5] The nitrogen oxide reduction catalyst for producing ammonia according to any one of [1] to [4], wherein the content of the element A in the nitrogen oxide reduction catalyst for producing ammonia is 4.5 to 22.0 mass %. [6] A method for producing ammonia, comprising: a preparation step of preparing the nitrogen oxide reduction catalyst for producing ammonia according to any one of [1] to [5]; a contact step A in which a nitrogen oxide-containing gas is contacted with the nitrogen oxide reduction catalyst for producing ammonia; a contacting step B in which the nitrogen oxide reducing catalyst for producing ammonia, which has been contacted with a gas containing nitrogen oxides, is contacted with water vapor and a gas containing carbon monoxide; A method for producing ammonia comprising the steps of: [7] The method for producing ammonia according to [6], wherein the contact step A and the contact step B are carried out simultaneously. [8] The method for producing ammonia according to [6], wherein the nitrogen oxide is nitric oxide.

Claims

1. A nitrogen oxide reduction catalyst for producing ammonia, comprising a support and elemental nickel supported on the support, the support comprises cerium oxide; The nitrogen oxide reduction catalyst for producing ammonia, wherein the nitrogen oxide reduction catalyst comprises one or more elements A selected from the group consisting of alkali metals and alkaline earth metals, supported on the support.

2. 2. The nitrogen oxide reduction catalyst for producing ammonia according to claim 1, wherein the element A is one or more elements selected from the group consisting of lithium, sodium, potassium, calcium, barium, and cesium.

3. 3. The nitrogen oxide reduction catalyst for producing ammonia according to claim 2, wherein the element A is sodium.

4. 2. The nitrogen oxide reduction catalyst for producing ammonia according to claim 1, wherein the content of the element A in the nitrogen oxide reduction catalyst for producing ammonia is 0.5 to 22.0 mass %.

5. 2. The nitrogen oxide reduction catalyst for producing ammonia according to claim 1, wherein the content of the element A in the nitrogen oxide reduction catalyst for producing ammonia is 4.5 to 22.0 mass %.

6. A method for producing ammonia, comprising: a preparation step of preparing the nitrogen oxide reduction catalyst for producing ammonia according to any one of claims 1 to 5; a contact step A in which a nitrogen oxide-containing gas is contacted with the nitrogen oxide reduction catalyst for producing ammonia; a contacting step B in which water vapor and a gas containing carbon monoxide are contacted with the nitrogen oxide reducing catalyst for producing ammonia that has been contacted with a gas containing nitrogen oxides; A method for producing ammonia comprising the steps of:

7. The method for producing ammonia according to claim 6 , wherein the contacting step A and the contacting step B are carried out simultaneously.

8. 7. The method for producing ammonia according to claim 6, wherein the nitrogen oxide is nitric oxide.

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