Method for synthesizing ammonia and apparatus for synthesizing ammonia

Abstract

This method includes: (1) preparing a first electrode (120) and a second electrode (150), wherein the first electrode (120) has a metal porous body (122), the metal porous body (122) has a first surface (124), a second surface (126), and through pores, and a catalyst is supported on the first surface (124) of the metal porous body (122); (2) bringing liquid water (170) into contact with the second surface (126) of the first electrode (120), so that the first surface (124) of the metal porous body (122) is covered with a film (180) of water supplied from the liquid water (170) by capillary action; (3) disposing the first electrode (120) and the second electrode (150) with a space (155) being interposed therebetween; and (4) applying a voltage between the first electrode (120) and the second electrode (150) and generating plasma in the space (155) in a state in which a nitrogen-containing gas is supplied to the space (155).

Description

Method for synthesizing ammonia and apparatus for synthesizing ammonia

[0001] The present invention relates to a method for synthesizing ammonia and an apparatus for synthesizing ammonia.

[0002] Ammonia is a raw material used in the manufacture of fertilizers, synthetic resins, explosives, pharmaceuticals, etc. Its use as a hydrogen carrier is also being considered. ２ It is also expected to be a fuel that does not produce emissions.

[0003] Ammonia is produced using the Haber-Bosch process, with 200 million tons used worldwide and 1.1 million tons used annually in Japan.

[0004] In the Haber-Bosch process, ammonia can be produced by reacting hydrogen and nitrogen at a temperature of 400°C to 500°C and a pressure of 15 MPa to 30 MPa in the presence of a catalyst.

[0005] Japanese Patent Publication No. 2017-164736

[0006] Currently, the hydrogen used in the Haber-Bosch process is produced from fossil fuels, and a large amount of CO2 is produced during this process. ２ There is the problem of gas generation. Also, when looking at the total process of ammonia production, more than half of the production cost is the cost of hydrogen production. Therefore, CO2 is generated during hydrogen production. ２ While hydrogen production through water electrolysis is being considered to reduce emissions, water electrolysis is costly, and using hydrogen produced through water electrolysis in the Haber-Bosch process would lead to a significant increase in costs.

[0007] Furthermore, the Haber-Bosch process is a high-temperature, high-pressure process, which also presents the problem of high energy consumption.

[0008] Therefore, CO as a total process ２ There is a need for technologies that synthesize ammonia with low emissions and low energy consumption.

[0009] This invention was made in view of the above background, and in this invention, CO ２The objective is to provide a method for synthesizing ammonia that can significantly reduce emissions and significantly reduce energy consumption, as well as an apparatus for such synthesis.

[0010] The present invention provides a method for synthesizing ammonia, comprising: (1) preparing a first electrode and a second electrode, wherein the first electrode has a porous metal body, the porous metal body has a first surface and a second surface facing each other, and a through-pore penetrating from the first surface to the second surface, and a catalyst is supported on the first surface of the porous metal body; (2) contacting the second surface of the first electrode with liquid water, wherein the first surface of the porous metal body is covered with a film of water supplied from the liquid water by capillary action of the through-pore; (3) arranging the first electrode and the second electrode with a space between them such that the first surface of the first electrode faces the second electrode; and (4) supplying a nitrogen-containing gas to the space, applying a voltage between the first electrode and the second electrode to generate plasma in the space, wherein (2) and (3) are in no particular order.

[0011] Furthermore, the present invention provides an apparatus for synthesizing ammonia, comprising a first electrode and a second electrode, wherein the first electrode has a porous metal body, the porous metal body has a first surface and a second surface facing each other, and a through-pore penetrating from the first surface to the second surface, a catalyst is supported on the first surface of the porous metal body, the first surface is covered with a film of water supplied from liquid water present on the second surface side by capillary action of the through-pore, the second electrode is positioned to face the first surface of the first electrode across a space, and when a voltage is applied between the first electrode and the second electrode with nitrogen gas supplied to the space, plasma is generated in the space, and ammonia is produced by the action of the plasma and the catalyst.

[0012] In this invention, CO ２We can provide a method for synthesizing ammonia that can significantly reduce emissions and significantly reduce energy consumption, as well as an apparatus for such synthesis.

[0013] This is a schematic cross-sectional view showing an example of the configuration of an apparatus for synthesizing ammonia according to one embodiment of the present invention. This is a schematic diagram showing an example of the flow of a method for synthesizing ammonia according to one embodiment of the present invention. This is a graph summarizing the relationship between the input power and the ammonia production rate obtained in each example. This is a graph summarizing the relationship between the input power and water temperature obtained in each example.

[0014] The following describes one embodiment of the present invention.

[0015] As mentioned above, in the Haber-Bosch process, which is widely used as the current ammonia production process, CO2 is produced during the process of producing hydrogen gas, the raw material. ２ There are problems such as emissions and high energy consumption.

[0016] In contrast, an embodiment of the present invention provides a method for synthesizing ammonia, comprising: (1) the step of preparing a first electrode and a second electrode, wherein the first electrode has a porous metal body, the porous metal body has a first surface and a second surface facing each other, and a through-pore penetrating from the first surface to the second surface, and a catalyst is supported on the first surface of the porous metal body; (2) the step of bringing liquid water into contact with the second surface of the first electrode, wherein the first surface of the porous metal body is covered with a film of water supplied from the liquid water by capillary action of the through-pore; (3) the step of arranging the first electrode and the second electrode with a space between them such that the first surface of the first electrode faces the second electrode; and (4) the step of supplying nitrogen-containing gas to the space, applying a voltage between the first electrode and the second electrode to generate plasma in the space.

[0017] Note that steps (2) and (3) mentioned above can be performed in any order.

[0018] In an ammonia synthesis process according to one embodiment of the present invention, nitrogen gas supplied to the space between the first electrode and the second electrode, and a water film present on the first surface of a porous metal body are used as reaction raw materials. That is, in one embodiment of the present invention, a plasma environment is formed using nitrogen gas and liquid water as raw materials, and various reactive species are generated. These reactive species react in the presence of a catalyst to produce ammonia.

[0019] The interaction between plasma and liquid water primarily occurs at the surface of the liquid water, and it is said that excited species, radicals, electrons, and ions generated by the plasma can only penetrate to a depth of less than 500 nm. Therefore, in plasma catalytic processes that involve the interaction of plasma and a catalyst, it has not been possible to form a reaction field with liquid water, a catalyst, and plasma. However, in one embodiment of the present invention, a water film of about 30 nm to 100 nm is continuously formed on the catalyst surface, and plasma is applied to this film, thereby enabling interaction between liquid water, plasma, and a catalyst.

[0020] Thus, in one embodiment of the present invention, liquid water is used as the raw material for ammonia production, instead of hydrogen gas. Therefore, in one embodiment of the present invention, CO2 is emitted during the production of the raw material. ２ The amount can be significantly reduced.

[0021] Furthermore, in one embodiment of the present invention, the reaction field is constructed by utilizing plasma and a catalyst. In such a "plasma catalyst" environment, the ammonia production reaction can be easily activated. Therefore, in one embodiment of the present invention, it is not necessary to actively pressurize or heat the reaction field. As a result, in one embodiment of the present invention, a high-temperature, high-pressure environment is not required for the synthesis process, and the amount of energy required for the process can be significantly reduced.

[0022] In particular, in one embodiment of the present invention, liquid water, rather than water vapor, is used as the hydrogen source. Therefore, in one embodiment of the present invention, there is no need to supply energy to the reaction system to gasify water, and in this respect as well, the amount of energy required for the process can be significantly reduced.

[0023] Here, in the ammonia synthesis process according to an embodiment of the present invention, liquid water supplied to the first surface through pores in a metal porous body by capillary action is used as a raw material. In this case, as long as the second surface of the metal porous body is in contact with the liquid water, the raw material water does not deplete on the first surface, and the ammonia generation reaction can continue.

[0024] Further, in the ammonia synthesis process according to an embodiment of the present invention, the liquid water serving as a raw material is provided in the form of a thin film (water film). By utilizing such a thin water film, in the plasma reaction field, the problem that the catalyst supported on the first surface of the metal porous body is covered with a thick water layer, making it difficult to draw out the reaction activity, can be significantly avoided. As a result, in an embodiment of the present invention, it becomes possible to maximize the reaction activity effect by the catalyst, and it becomes possible to generate ammonia at a relatively high production rate.

[0025] Currently, as the active species generated in the aforementioned "plasma catalyst" environment, vibration N ２ molecules, N atom radicals, H atom radicals, OH radicals, O atom radicals, and electrons, etc. are considered. Also, the active species that did not contribute to the ammonia generation reaction are considered to be consumed by the side product generation reaction. As side products, for example, NO ｘ and H ２ O ２ etc. are considered.

[0026] However, it should be noted that the above considerations are based on the data obtained at present, and an embodiment of the present invention is not limited to such a theory.

[0027] (Apparatus for synthesizing ammonia according to an embodiment of the present invention) Hereinafter, referring to FIG. 1, an apparatus for synthesizing ammonia according to an embodiment of the present invention will be described.

[0028] FIG. 1 schematically shows an example of the configuration of an apparatus for synthesizing ammonia (hereinafter referred to as the "first apparatus") according to an embodiment of the present invention.

[0029] As shown in FIG. 1, the first device 100 includes a first electrode 120 housed in a reactor 110, a second electrode 150, and a water source 160.

[0030] The reactor 110 is provided with a gas inlet 112 and a gas outlet 114.

[0031] The first electrode 120 includes a metal porous body 122 carrying a catalyst. The metal porous body 122 has a first surface 124 and a second surface 126 facing each other, and the catalyst is carried on the first surface 124.

[0032] The metal porous body 122 has through-pores penetrating from the first surface 124 to the second surface 126.

[0033] The porosity of the metal porous body 122 is, for example, in the range of 50% to 95%, preferably in the range of 75% to 85%. Also, the average pore diameter of the metal porous body 122 is, for example, in the range of 50 μm to 500 μm, preferably in the range of 100 μm to 300 μm. In the present application, the porosity and the average pore diameter are measured by a mercury porosimeter.

[0034] The second electrode 150 is disposed at a predetermined distance from the first electrode 120. The first electrode 120 and the second electrode 150 are used to generate plasma in the space 155 therebetween.

[0035] The water source 160 contains or circulates liquid water 170. For example, in the example shown in FIG. 1, the water source 160 is composed of a water tank 161 containing water 170.

[0036] The water source 160 is disposed relative to the first electrode 120 such that the water 170 housed therein contacts the second surface 126 of the metal porous body 122 of the first electrode 120. For example, in the example shown in FIG. 1, the metal porous body 122 is disposed relative to the water tank 161 such that the second surface 126 is below the water surface in the water tank 161.

[0037] As described above, the metal porous body 122 has through pores. Therefore, the water 170 on the side of the second surface 126 of the metal porous body 122 reaches the first surface 124 through the inside of the metal porous body 122 due to capillary action. As a result, a water film 180 is formed on the first surface 124.

[0038] The thickness of the water film 180 is, for example, in the range of 5 nm to 500 nm, and preferably in the range of 30 nm to 100 nm.

[0039] When ammonia is synthesized using such a first apparatus 100, first, a nitrogen-containing gas is supplied from the gas inlet 112 of the reactor 110 toward the space 155. Further, a plasma generation voltage is applied between the first electrode 120 and the second electrode 150.

[0040] As a result, a plasma environment is formed in the space 155. In the plasma environment, various components generated from nitrogen gas (for example, vibration nitrogen molecules and nitrogen atom radicals, etc.), and various components formed from the water film 180 (hydrogen atom radicals, oxygen atom radicals, and OH molecule radicals, etc. Hereinafter, these are collectively referred to as "plasma components") are in a mixed state.

[0041] Further, a catalyst is supported on the metal porous body 122. Therefore, ammonia is generated in the space 155 by the reaction of the plasma components in the presence of the catalyst.

[0042] A part of the generated ammonia is discharged as a gas from the gas outlet 114. Also, a part of the obtained ammonia is dissolved in the water 170 stored in the water source 160. Therefore, the synthesized ammonia can be recovered as a gas and a liquid.

[0043] Thus, in the first apparatus 100, ammonia can be synthesized without using hydrogen as a raw material. Also, in the first apparatus 100, ammonia can be synthesized without controlling the inside of the reactor 110 to high temperature and high pressure as in the Haber - Bosch process.

[0044] Therefore, in the first apparatus 100, in the total process of ammonia synthesis, CO ２It can significantly reduce emissions and significantly reduce energy consumption.

[0045] The details of each component used in the first device 100 will be described below.

[0046] (First electrode 120) As described above, the first electrode 120 has a porous metal body 122. The porous metal body 122 is connected to a first lead wire 129, and is electrically connected to an external power supply, etc., via the first lead wire 129.

[0047] (Porous Metal Body 122) The material of the porous metal body 122 is not particularly limited as long as it is a metal. The porous metal body 122 may be made of, for example, stainless steel, copper, titanium, nickel, cobalt, or iron.

[0048] In the example shown in Figure 1, the porous metal body 122 is a plate-shaped member. However, this is merely one example, and the porous metal body 122 may have any shape as long as it has a first surface 124 and a second surface 126.

[0049] For example, the porous metal body 122 may be tubular. In this case, the outer and inner surfaces of the tube become the first surface 124 and the second surface 126, respectively. In this case, water 170 is contained or circulated in the space inside the tube, and the space inside the tube becomes the water source 160.

[0050] The catalyst supported on the porous metal body 122 may include, for example, at least one of ruthenium (Ru), iron (Fe), osmium (Os), molybdenum (Mo), nickel (Ni), rhodium (Rh), iridium (Ir), rhenium (Re), cobalt (Co), platinum (Pt), palladium (Pd), and chromium (Cr). Among these, Ru is preferred.

[0051] Furthermore, the catalyst does not necessarily need to cover the entire first surface 124 of the porous metal body 122. For example, the ratio (S1 / Sc) of the area occupied by the catalyst (Sc) to the area of ​​the first surface 124 (S1) may be in the range of 5 to 80. This increases the specific surface area of ​​the catalyst that comes into contact with the water film 180.

[0052] (Second electrode 150) The shape of the second electrode 150 is not particularly limited. The second electrode 150 may be, for example, in the form of a plate or a rod.

[0053] The second electrode 150 is connected to a second lead wire 159, and is electrically connected to an external power supply or the like via the second lead wire 159.

[0054] In addition, in the first apparatus 100, the plasma may be generated by dielectric barrier discharge.

[0055] In this case, the second electrode 150 may have a conductor 151 covered with a dielectric member 152, as shown in Figure 1.

[0056] The material of the dielectric member 152 is not particularly limited as long as it is a dielectric, but it may be made of, for example, quartz or alumina.

[0057] (Water source 160) As mentioned above, the water source 160 may consist of a water tank 161. Liquid water 170 is contained in the water tank 161, or water 170 is circulated through it.

[0058] Water 170 may be pure water or an aqueous solution. The aqueous solution may be, for example, an aqueous solution of NaCl, an aqueous solution of NaOH, or an aqueous solution of HCl. However, it is preferable that water 170 be pure water.

[0059] The temperature of the water 170 contained or circulated is not particularly limited, but is, for example, in the range of 5°C to 40°C.

[0060] (Method for synthesizing ammonia according to one embodiment of the present invention) Next, a method for synthesizing ammonia according to one embodiment of the present invention will be described with reference to Figure 2.

[0061] Figure 2 schematically shows an example of a flow diagram of a method for synthesizing ammonia according to one embodiment of the present invention (hereinafter referred to as the "first method").

[0062] As shown in Figure 2, the first method comprises: (1) the step of preparing a first electrode and a second electrode, wherein the first electrode has a porous metal body, the porous metal body has a first surface and a second surface facing each other, and a through-pore penetrating from the first surface to the second surface, and a catalyst is supported on the first surface of the porous metal body; (2) the step of bringing liquid water into contact with the second surface of the first electrode, wherein the first surface of the porous metal body is covered with a film of water supplied from the liquid water by capillary action of the through-pore; (3) the step of arranging the first electrode and the second electrode with a space between them such that the first surface of the first electrode faces the second electrode; and (4) the step of supplying nitrogen gas to the space and applying a voltage between the first electrode and the second electrode to generate plasma in the space.

[0063] The following describes each step. For clarity, the following description will use the first method implemented using the first apparatus 100 shown in Figure 1 as an example. Therefore, the reference numerals shown in Figure 1 will be used when referring to each component.

[0064] (Step S110) First, the first electrode 120 and the second electrode 150 are prepared. The first electrode 120 and the second electrode 150 may be housed in the reactor 110.

[0065] The first electrode 120 has a porous metal body 122 on which a catalyst is supported. Details of the porous metal body 122 are as described above. The second electrode 150 may have a conductor 151 and a dielectric member 152, as shown in the configuration in Figure 1.

[0066] (Step S120) Next, the second surface 126 of the porous metal body 122 is brought into contact with liquid water 170. The water 170 may be contained in a water tank 161 located inside the reactor 110.

[0067] The porous metal body 122 has through pores. Therefore, when the second surface 126 of the porous metal body 122 comes into contact with water 170, the water 170 moves from the second surface 126 to the first surface 124 of the porous metal body 122 due to capillary action. As a result, a water film 180 is formed on the first surface 124 of the first electrode 120.

[0068] The water 170 in the tank 161 is preferably pure water, but it may also be an aqueous solution. If the water 170 is an aqueous solution, such an aqueous solution may be selected from, for example, an aqueous solution of NaCl, an aqueous solution of NaOH, or an aqueous solution of HCl.

[0069] The temperature of water 170 is not particularly limited, but for example, it is in the range of 5°C to 40°C.

[0070] (Step S130) Next, the first electrode 120 and the second electrode 150 are positioned in the reactor 110 such that the first surface 124 of the first electrode 120 faces the second electrode 150.

[0071] The distance between the two electrodes is, for example, 1 mm to 2.5 mm.

[0072] (Step S140) Next, nitrogen-containing gas is supplied from the gas inlet 112 into the space 155 between the two electrodes.

[0073] The nitrogen-containing gas may be pure nitrogen gas or a mixed gas containing nitrogen gas and a carrier gas. The carrier gas may be an inert gas such as Ar.

[0074] The supply rate of nitrogen-containing gas varies depending on the dimensions of the reactor 110, but is, for example, in the range of 0.002 mol / min to 2 mol / min.

[0075] (Step S140) Next, with nitrogen-containing gas supplied to the space 155 of the reactor 110, a voltage is applied between the first electrode 120 and the second electrode 150. This generates a plasma containing the aforementioned "plasma component" in the space 155.

[0076] The plasma may be formed by dielectric barrier discharge.

[0077] As mentioned above, a catalyst is supported on the first surface 124 of the porous metal body 122. Therefore, ammonia is generated in the space 155 by the reaction of the "plasma components" in the presence of the catalyst.

[0078] In the first method, ammonia can be synthesized by the above process. NO is produced as a byproduct. ｘ and H ２ O ２ The following may occur.

[0079] Furthermore, it is not necessary for all of the generated ammonia to be recovered as a gas. In other words, some of the ammonia may be dissolved in the water 170 in tank 161 and recovered as an aqueous solution.

[0080] The above describes a method for synthesizing ammonia according to one embodiment of the present invention, using the first method as an example. However, the above description is merely an example, and it will be obvious to those skilled in the art that the method for synthesizing ammonia according to one embodiment of the present invention may have other configurations. For example, in the first method, steps S120 and S130 may be carried out in the reverse order. Various other modifications are also possible.

[0081] The following describes embodiments of the present invention. In the following description, Examples 1 to 6 are examples, and Examples 11 to 12 are comparative examples.

[0082] (Example 1) Ammonia was synthesized using the apparatus shown in Figure 1.

[0083] The reactor used quartz tubes with an outer diameter of 50 mm, an inner diameter of 45 mm, and a length of 80 mm, arranged so that their axial direction was vertical.

[0084] The reactor housed a first electrode (lower electrode) and a second electrode (upper electrode).

[0085] The porous body of the first electrode was a disc made of SUS316L (26 mm in diameter x 1 mm thick). The porosity of the porous body was 82%.

[0086] Ruthenium metal (Ru) was deposited on one surface (the first surface) of the perforated plate by sputtering. Because the sputtering time was intentionally shortened, the Ru was distributed on the first surface not in a layered manner, but rather in a patchy, island-like pattern.

[0087] The second electrode had a configuration as shown in Figure 1, in which a conductive plate (stainless steel) was covered with a dielectric material (quartz).

[0088] Furthermore, pure water was stored at the bottom of the reactor, and the perforated plate was placed in the water tank so that its second surface was in contact with the water surface. The water temperature was set to room temperature.

[0089] The distance between the first electrode and the second electrode was set to 1.5 mm.

[0090] Next, a nitrogen-containing gas was supplied to the space between the first electrode and the second electrode at a flow rate of 0.002 mol / min. The nitrogen-containing gas was a mixture of argon and nitrogen at room temperature (Ar:N ２ = 2:1 vol%) was used.

[0091] Next, a high-frequency voltage of 5000V was applied between the first and second electrodes to generate plasma through dielectric barrier discharge, initiating the "plasma catalyst" reaction.

[0092] The reaction time was set to 10 minutes.

[0093] After processing, the ammonia production rate was evaluated using the indophenol blue method.

[0094] (Examples 2-6) Ammonia was synthesized using the same method as in Example 1. However, in these examples, the power applied to the electrodes was changed from that in Example 1.

[0095] (Example 11) An attempt was made to synthesize ammonia using the same method as in Example 1.

[0096] However, in this example 11, instead of a porous plate, a foil made of SUS316L with a thickness of 0.1 μm was used as the first electrode (porosity was approximately 0).

[0097] (Example 12) An attempt was made to synthesize ammonia using the same method as in Example 1.

[0098] However, in this example 12, a SUS316L foil with a thickness of 0.1 μm was used as the first electrode (porosity was approximately 0). Also, no catalyst was placed on the first electrode.

[0099] (Results) Table 1 summarizes the evaluation results of the ammonia production rate obtained in each example.

[0100] Table 1 shows that in Examples 11 and 12, the ammonia production rates were 0.0057 μmol / sec and 0.0025 μmol / sec, respectively. In contrast, in Examples 1 to 6, the ammonia production rate exceeded at least 0.023 μmol / sec, indicating that relatively high production rates were obtained.

[0101] Figure 3 shows a graph plotting the results obtained in each example.

[0102] In Figure 3, the horizontal axis represents the amount of electricity (W) supplied for plasma generation, and the vertical axis represents the ammonia production rate (μmol / sec).

[0103] Figure 3 also shows that in Examples 1 to 6, a higher generation rate was obtained compared to Examples 11 to 12.

[0104] However, in Examples 1 to 6, it was found that the ammonia production rate tends to decrease when the power input exceeds 60W. In other words, the ammonia production rate does not increase monotonically with respect to the power input, but rather reaches its maximum at approximately 50W to 60W.

[0105] This is thought to be because when the input power increases drastically, the water temperature of the water source rises, causing some of the liquid water to vaporize. ２ When plasma-active species act on the catalyst surface, ammonia can be efficiently produced. However, if water vaporizes, N2 in the gas phase will be lost. ２ Plasma and H ２ O molecules react. As a result, N ２ It is thought that the ammonia production rate decreases because the proportion of active species from the plasma acting on the aqueous film and catalyst surface decreases.

[0106] Figure 4 shows the relationship between the amount of electricity (W) supplied for plasma generation and the temperature of the water in the tank.

[0107] As can be seen from Figure 4, as discussed above, the water temperature rises with increasing power input, and in particular, the water temperature rises significantly when the power input exceeds 60W.

[0108] Thus, it has been found that the presence of gaseous water in the reaction system is undesirable from the viewpoint of the ammonia production rate. Therefore, in one embodiment of the present invention, it is preferable that the temperature of the water source in the reaction system be 50°C or lower.

[0109] (Aspects of the present invention) (Aspect 1) A method for synthesizing ammonia, comprising: (1) preparing a first electrode and a second electrode, wherein the first electrode has a porous metal body, the porous metal body has a first surface and a second surface facing each other, and a through-pore penetrating from the first surface to the second surface, and a catalyst is supported on the first surface of the porous metal body; (2) contacting the second surface of the first electrode with liquid water, wherein the first surface of the porous metal body is covered with a film of water supplied from the liquid water by capillary action of the through-pore; (3) arranging the first electrode and the second electrode with a space between them such that the first surface of the first electrode faces the second electrode; and (4) supplying a nitrogen-containing gas to the space, applying a voltage between the first electrode and the second electrode to generate plasma in the space. The above (2) and (3) are in no particular order, and are methods.

[0110] (Aspect 2) The method according to aspect 1, wherein (4) is carried out at a pressure in the range of 0.5 atmospheres to 1.5 atmospheres.

[0111] (Aspect 3) The method according to aspect 1 or 2, wherein (4) is carried out substantially without heating the porous metal body.

[0112] (Aspect 4) The method according to any one of aspects 1 to 3, wherein the temperature of the liquid water is in the range of 5°C to 55°C.

[0113] (Aspect 5) The plasma is generated by dielectric barrier discharge, according to any one of aspects 1 to 4.

[0114] (Aspect 6) The method according to any one of aspects 1 to 5, wherein in (2), a water tank containing the liquid water is used, and the porous metal body is positioned relative to the water tank such that the second surface is in contact with the liquid water.

[0115] (Aspect 7) The water film having a thickness in the range of 5 nm to 500 nm, according to any one of aspects 1 to 6.

[0116] (Aspect 8) The method according to any one of aspects 1 to 7, wherein the liquid water is pure water.

[0117] (Aspect 9) The method according to any one of aspects 1 to 8, wherein the catalyst is distributed in an island-like manner on the first surface.

[0118] (Aspect 10) The method according to any one of aspects 1 to 9, wherein the porous metal is a plate-shaped member.

[0119] (Aspect 11) The method according to any one of aspects 1 to 10, wherein the catalyst comprises at least one of ruthenium (Ru), iron (Fe), osmium (Os), molybdenum (Mo), nickel (Ni), rhodium (Rh), iridium (Ir), rhenium (Re), cobalt (Co), platinum (Pt), palladium (Pd), and chromium (Cr).

[0120] (Aspect 12) An apparatus for synthesizing ammonia, comprising a first electrode and a second electrode, wherein the first electrode has a porous metal body, the porous metal body has a first surface and a second surface facing each other, and a through-pore penetrating from the first surface to the second surface, a catalyst is supported on the first surface of the porous metal body, the first surface is covered with a film of water supplied from liquid water present on the side of the second surface by capillary action of the through-pore, the second electrode is positioned to face the first surface of the first electrode across a space, and when a voltage is applied between the first electrode and the second electrode with nitrogen gas supplied to the space, plasma is generated in the space, and ammonia is produced by the action of the plasma and the catalyst.

[0121] (Aspect 13) The apparatus according to aspect 12, wherein the plasma is generated by dielectric barrier discharge.

[0122] (Aspect 14) The apparatus according to aspect 13, wherein the second electrode is covered with a dielectric.

[0123] (Aspect 15) The apparatus according to aspect 14, wherein the dielectric is quartz or alumina.

[0124] (Aspect 16) The apparatus according to any one of aspects 12 to 15, wherein the water film has a thickness in the range of 5 nm to 500 nm.

[0125] (Aspect 17) The apparatus according to any one of aspects 12 to 16, further comprising a water tank containing the liquid water, wherein the porous metal body is positioned relative to the water tank such that the second surface is in contact with the liquid water.

[0126] (Aspect 18) The apparatus according to any one of aspects 12 to 17, wherein the liquid water is pure water.

[0127] (Aspect 19) The apparatus according to any one of aspects 12 to 18, wherein the catalyst is distributed in an island-like manner on the first surface.

[0128] (Aspect 20) The apparatus according to any one of aspects 12 to 19, wherein the porous metal is a plate-shaped member.

[0129] (Aspect 21) The apparatus according to any one of aspects 12 to 20, wherein the catalyst comprises at least one of ruthenium (Ru), iron (Fe), osmium (Os), molybdenum (Mo), nickel (Ni), rhodium (Rh), iridium (Ir), rhenium (Re), cobalt (Co), platinum (Pt), palladium (Pd), and chromium (Cr).

[0130] This application claims priority based on Japanese Patent Application No. 2024-161197, filed on 18 September 2024, and incorporates all of its disclosures herein.

[0131] 100 Apparatus for synthesizing ammonia (first apparatus) 110 Reactor 112 Gas inlet 114 Gas outlet 120 First electrode 122 Porous metal 124 First surface 126 Second surface 129 First lead wire 150 Second electrode 151 Conductor 152 Dielectric material 155 Space 159 Second lead wire 160 Water source 161 Water tank 170 Water 180 Water film

Claims

1. A method for synthesizing ammonia, comprising: (1) preparing a first electrode and a second electrode, wherein the first electrode has a porous metal body, the porous metal body has a first surface and a second surface facing each other, and a through-pore penetrating from the first surface to the second surface, and a catalyst is supported on the first surface of the porous metal body; (2) contacting the second surface of the first electrode with liquid water, wherein the first surface of the porous metal body is covered with a film of water supplied from the liquid water by capillary action of the through-pore; (3) arranging the first electrode and the second electrode with a space between them such that the first surface of the first electrode faces the second electrode; and (4) supplying a nitrogen-containing gas to the space, applying a voltage between the first electrode and the second electrode to generate plasma in the space, wherein (2) and (3) are in no particular order.

2. The method according to claim 1, wherein (4) is carried out at a pressure in the range of 0.5 atmospheres to 1.5 atmospheres.

3. The method according to claim 1, wherein (4) is carried out substantially without heating the porous metal.

4. The method according to claim 1, wherein the temperature of the liquid water is in the range of 5°C to 55°C.

5. The method according to claim 1, wherein the plasma is generated by dielectric barrier discharge.

6. The method according to claim 1, wherein in (2) above, a water tank containing the liquid water is used, and the porous metal body is positioned relative to the water tank such that the second surface is in contact with the liquid water.

7. The method according to claim 1, wherein the water film has a thickness in the range of 5 nm to 500 nm.

8. The method according to claim 1, wherein the liquid water is pure water.

9. The method according to claim 1, wherein the catalyst is distributed in an island-like manner on the first surface.

10. The method according to claim 1, wherein the porous metal is a plate-shaped member.

11. The method according to claim 1, wherein the catalyst comprises at least one of ruthenium (Ru), iron (Fe), osmium (Os), molybdenum (Mo), nickel (Ni), rhodium (Rh), iridium (Ir), rhenium (Re), cobalt (Co), platinum (Pt), palladium (Pd), and chromium (Cr).

12. An apparatus for synthesizing ammonia, comprising a first electrode and a second electrode, wherein the first electrode has a porous metal body, the porous metal body has a first surface and a second surface facing each other, and a through-pore penetrating from the first surface to the second surface, a catalyst is supported on the first surface of the porous metal body, the first surface is covered with a film of water supplied from liquid water present on the side of the second surface by capillary action of the through-pore, the second electrode is positioned to face the first surface of the first electrode across a space, and when a voltage is applied between the first electrode and the second electrode with nitrogen gas supplied to the space, plasma is generated in the space, and ammonia is produced by the action of the plasma and the catalyst.

13. The apparatus according to claim 12, wherein the plasma is generated by dielectric barrier discharge.

14. The apparatus according to claim 13, wherein the second electrode is covered with a dielectric material.

15. The apparatus according to claim 14, wherein the dielectric is quartz or alumina.

16. The apparatus according to claim 12, wherein the water film has a thickness in the range of 5 nm to 500 nm.

17. The apparatus according to claim 12, further comprising a water tank containing the liquid water, wherein the porous metal body is positioned relative to the water tank such that the second surface is in contact with the liquid water.

18. The apparatus according to claim 12, wherein the liquid water is pure water.

19. The apparatus according to claim 12, wherein the catalyst is distributed in an island-like manner on the first surface.

20. The apparatus according to claim 12, wherein the porous metal is a plate-shaped member.

21. The apparatus according to claim 12, wherein the catalyst comprises at least one of ruthenium (Ru), iron (Fe), osmium (Os), molybdenum (Mo), nickel (Ni), rhodium (Rh), iridium (Ir), rhenium (Re), cobalt (Co), platinum (Pt), palladium (Pd), and chromium (Cr).

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