Ammonia production apparatus

Abstract

The purpose of the present disclosure is to provide an ammonia production apparatus capable of efficiently producing ammonia and suppressing production cost. The present disclosure relates to an ammonia production apparatus comprising: an anode chamber which has an anode electrode having a water electrolysis catalyst and to which water is supplied; a cathode chamber which has a cathode electrode having an ammonia synthesis catalyst and to which gaseous nitrogen is supplied; a diaphragm provided between the anode chamber and the cathode chamber; and a cathode electrode drying means for drying the cathode electrode. In the ammonia production apparatus, ammonia is synthesized from a hydrogen source and the nitrogen in the presence of the ammonia synthesis catalyst in the cathode chamber.

Description

Ammonia production equipment

[0001] This invention relates to an ammonia production apparatus.

[0002] Ammonia is an important chemical raw material used as a basic material for fertilizers and chemical products, and in recent years its use in coal-fired power generation co-firing and as an energy carrier has also attracted attention. Traditionally, ammonia has been industrially produced by the Haber-Bosch process. The Haber-Bosch process is a method of producing ammonia by reacting nitrogen gas and hydrogen gas in the presence of an iron-based catalyst.

[0003] However, the Haber-Bosch process synthesizes ammonia under high temperature and pressure, requiring large equipment made of specialized materials. Therefore, there is a need for the development of novel ammonia production equipment that does not require special conditions.

[0004] For example, Patent Document 1 discloses an ammonia production apparatus comprising an electrochemical reaction cell which includes a first reaction vessel in which a reducing electrode is arranged and gaseous nitrogen is supplied, a second reaction vessel in which an oxidizing electrode is arranged and an electrolyte containing water or water vapor is supplied, and a diaphragm provided between the first reaction vessel and the second reaction vessel.

[0005] Japanese Patent Publication No. 2024-042595

[0006] Incidentally, when obtaining gaseous ammonia from gaseous nitrogen, a manufacturing apparatus is generally used that includes a cathode, an anode, and a diaphragm to separate the cathode and anode. Gaseous ammonia is obtained on the cathode side, which is equipped with a catalyst for obtaining ammonia. This catalyst is altered by contact with liquid water, and its catalytic performance may decrease as a result of this alteration. Furthermore, if the catalyst is covered with liquid water, the frequency of contact between the catalyst and gaseous nitrogen decreases, which may reduce the yield of ammonia. Moreover, since gaseous ammonia is readily soluble in liquid water, it is difficult to obtain gaseous ammonia in an environment where liquid water is present. In addition, separating ammonia dissolved in liquid water as a gas requires additional processes such as distillation, which incurs extra costs. In other words, in order to efficiently produce gaseous ammonia and reduce its production costs, it is conceivable to remove liquid water from the cathode side.

[0007] On the other hand, when obtaining gaseous ammonia from gaseous nitrogen, a raw material is needed to supply hydrogen to bond with the nitrogen. From a cost perspective, water is generally used as such a raw material. When using the above-mentioned manufacturing apparatus, water is used on the anode side. Here, the cathode and anode are separated by a diaphragm, but water on the anode side may move to the cathode side through the diaphragm, bringing liquid water to the cathode side. Therefore, it has been found that when water is used on the anode side and gaseous ammonia is produced on the cathode side, the efficiency of ammonia production decreases or the production cost is increased.

[0008] This invention has been made in view of the above-mentioned problems, and aims to provide an ammonia production apparatus that can efficiently produce ammonia and suppress production costs.

[0009] The present inventors diligently studied to solve the above problems. As a result, they found that the above problems can be solved by an ammonia production apparatus comprising an anode chamber having an anode electrode with a water electrolytic catalyst and to which water is supplied, a cathode chamber having an ammonia synthesis catalyst and to which gaseous nitrogen is supplied, a diaphragm provided between the anode chamber and the cathode chamber, and a cathode electrode drying means for drying the cathode electrode, wherein ammonia is synthesized in the cathode chamber in the presence of the ammonia synthesis catalyst from a hydrogen source and the nitrogen, and thus the present invention was completed.

[0010] In other words, the present invention includes the following embodiments: [1] An ammonia production apparatus comprising: an anode chamber having an anode electrode having a water electrolytic catalyst and to which water is supplied; a cathode chamber having a cathode electrode having an ammonia synthesis catalyst and to which gaseous nitrogen is supplied; a diaphragm provided between the anode chamber and the cathode chamber; and a cathode electrode drying means for drying the cathode electrode, wherein ammonia is synthesized in the cathode chamber in the presence of the ammonia synthesis catalyst from a hydrogen source and the nitrogen. [2] The ammonia production apparatus according to [1], wherein the cathode electrode drying means comprises at least one selected from the group consisting of a nitrogen flow rate adjusting means for increasing the flow rate of gaseous nitrogen supplied to the cathode chamber, a cathode chamber temperature adjusting means for raising the temperature inside the cathode chamber, and a nitrogen gas temperature adjusting means for raising the temperature of gaseous nitrogen before it is supplied into the cathode chamber. [3] The ammonia production apparatus according to [1] or [2], further comprising an anode chamber temperature adjusting means for adjusting the temperature inside the anode chamber. [4] The ammonia production apparatus according to [3], wherein the anode chamber temperature adjustment means comprises at least one selected from the group consisting of a water temperature adjustment means for adjusting the temperature of water before it is supplied into the anode chamber and an anode chamber temperature adjustment means for raising the temperature inside the anode chamber. [5] The ammonia production apparatus according to any one of [1] to [4], comprising a cathode chamber cooling means for lowering the temperature inside the cathode chamber. [6] The ammonia production apparatus according to any one of [1] to [5], wherein the diaphragm is an ion exchange membrane or a porous membrane. [7] The ammonia production apparatus according to any one of [1] to [6], wherein the ammonia synthesis catalyst comprises a molybdenum complex. [8] The ammonia production apparatus according to any one of [1] to [7], wherein the cathode electrode comprises a carrier supporting the ammonia synthesis catalyst. [9] The ammonia production apparatus according to [8], wherein the carrier comprises at least one porous carbon particle selected from the group consisting of channel black, furnace black, thermal black, acetylene black, activated carbon, natural graphite, artificial graphite, graphitized carbon, graphene, carbon nanotubes, fullerene, Ketjenblack, and glassy carbon.

[10] The ammonia production apparatus according to [8] or [9], wherein the cathode electrode includes a binder for binding the carrier.

[11] The ammonia production apparatus according to

[10] , wherein the binder includes an ionomer.

[12] The ammonia production apparatus according to any one of [1] to

[11] , wherein the cathode electrode includes at least one gas diffusion layer selected from the group consisting of carbon paper, carbon cloth, or carbon felt.

[13] The ammonia production apparatus according to any one of [1] to

[12] , further comprising an ammonia separation means for separating the synthesized ammonia from the gas discharged from the cathode chamber.

[14] The ammonia production apparatus according to any one of [1] to

[13] , further comprising a nitrogen separation means for separating nitrogen from air, wherein the gaseous nitrogen is obtained from the nitrogen separation means.

[15] A method for producing ammonia, comprising an ammonia production step of supplying nitrogen to the cathode chamber of the ammonia production apparatus according to any one of [1] to

[14] , and supplying water to the anode chamber of the ammonia production apparatus, and producing ammonia from nitrogen by electrolytic synthesis.

[16] A method for producing ammonia according to

[15] , further comprising a recovery step of separating and recovering the ammonia produced in the ammonia production step.

[17] An ammonia production apparatus according to any one of [1] to

[14] , wherein the cathode electrode contains a water-absorbing component.

[18] An ammonia production apparatus according to

[17] , wherein the water-absorbing component contains one or more selected from the group consisting of water-absorbing polymers, inorganic desiccants, biodegradable water-absorbing polymers, and water-absorbing metal-organic frameworks.

[19] An ammonia production apparatus according to

[17] or

[18] , wherein the water-absorbing component is at least one selected from the group consisting of sodium polyacrylate, potassium polyacrylate, polyvinyl alcohol, calcium oxide, and calcium chloride.

[20] An ammonia production apparatus according to any one of [1] to

[14] and

[17] to

[19] , wherein the cathode electrode contains a water-repellent component.

[21] The ammonia production apparatus according to

[20] , wherein the water-repellent component comprises one or more selected from the group consisting of organic polymer water-repellent materials and inorganic water-repellent materials.

[22] The ammonia production apparatus according to

[20] or

[21] , wherein the water-repellent component includes a water-repellent metal-organic framework.

[0011] According to the present invention, it is possible to provide an ammonia production apparatus that can efficiently produce ammonia and suppress production costs.

[0012] This is a schematic diagram showing an example of the ammonia production apparatus of this embodiment. This is a schematic enlarged view showing an example of the vicinity of the cathode electrode of this embodiment. This is a schematic enlarged view showing another example of the vicinity of the cathode electrode of this embodiment. This is a schematic enlarged view showing yet another example of the vicinity of the cathode electrode of this embodiment. This is a schematic diagram showing another example of the ammonia production apparatus of this embodiment. This is a schematic diagram showing yet another example of the ammonia production apparatus of this embodiment. This is a schematic diagram showing yet another example of the ammonia production apparatus of this embodiment. This is a schematic diagram showing yet another example of the ammonia production apparatus of this embodiment. This is a schematic enlarged view showing another example of the vicinity of the cathode electrode of this embodiment. This is a schematic diagram showing yet another example of the ammonia production apparatus of this embodiment. This is a schematic diagram showing yet another example of the ammonia production apparatus of this embodiment.

[0013] The embodiments of the present invention (hereinafter referred to as "these embodiments") will be described in detail below, with reference to the drawings as necessary. However, the present invention is not limited thereto, and various modifications are possible without departing from its essence. In the drawings, the same elements will be denoted by the same reference numerals, and redundant explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Moreover, the dimensional ratios in the drawings are not limited to those shown.

[0014] The ammonia production apparatus of this embodiment comprises an anode chamber having an anode electrode with a water electrolytic catalyst and to which water is supplied; a cathode chamber having a cathode electrode with an ammonia synthesis catalyst and to which gaseous nitrogen (hereinafter also referred to as "nitrogen gas") is supplied; a diaphragm provided between the anode chamber and the cathode chamber; and a cathode electrode drying means for drying the cathode electrode. In the cathode chamber, ammonia is synthesized from a hydrogen source and nitrogen in the presence of the ammonia synthesis catalyst.

[0015] Figure 1 is a schematic diagram showing an example of the ammonia production apparatus of this embodiment (hereinafter also simply referred to as the "ammonia production apparatus"). As shown in Figure 1, the ammonia production apparatus 100 comprises an anode chamber 110, a cathode chamber 120, a diaphragm 130, and a cathode electrode drying means 150. The anode chamber 110 is equipped with an anode electrode 112, and the cathode chamber 120 is equipped with a cathode electrode 122. The anode electrode 112 and the cathode electrode 122 are electrically connected via an external circuit so that a voltage can be applied. The various components of the ammonia production apparatus 100 will be described in detail below.

[0016] [Anode Chamber] The anode chamber 110 is equipped with an anode electrode 112. The anode electrode 112 may be arranged to cover the entire surface of the diaphragm 130 on the anode chamber 110 side, which will be described later. The anode electrode 112 has a water electrolytic catalyst, which is a substance that functions as a catalyst in the electrolysis reaction of water. The anode electrode 112 is not particularly limited, but for example, it may include a mesh-like carrier and a water electrolytic catalyst supported on the carrier. The mesh-like carrier is not particularly limited as long as it is conductive, and for example, a conductive mesh woven with conductive fibers including fibers and a conductive coating covering the fibers can be mentioned. The conductive fibers are not particularly limited, but for example, they may include fibers containing resin and a metal coating or carbon coating arranged to cover the surface of the fibers. Examples of water electrolytic catalysts include binary metal oxides such as manganese oxide, iridium oxide, nickel oxide, cobalt oxide, iron oxide, tin oxide, indium oxide, and ruthenium oxide; ternary metal oxides such as Ni-Co-O, La-Co-O, Ni-La-O, and Sr-Fe-O; quaternary metal oxides such as Pb-Ru-Ir-O and La-Sr-Co-O; and metal complexes such as Ru complexes and Fe complexes. The conductive film may also contain the water electrolytic catalyst.

[0017] The anode chamber 110 has a space into which water is supplied as an electrolyte. Here, the water supplied to the anode chamber 110 may be pure water, or it may contain electrolytes as needed. The electrolyte contained in the water supplied to the anode chamber 110 is not particularly limited and varies depending on the type of diaphragm and the electrolysis method, but examples include alkaline electrolytes such as potassium hydroxide and sodium hydroxide, acidic electrolytes such as sulfuric acid, and neutral electrolytes such as potassium sulfate and sodium sulfate. At the anode electrode 112, water is oxidized according to the following formula (1): 2H ２ O→O ２ +4H ＋ +4e － …(1) The electrons generated here are supplied to the cathode chamber 120 via an external circuit. Also, protons (H ＋) is supplied to the cathode chamber 120 via the diaphragm 130. The protons produced by the oxidation of water are hydrated to form hydronium (H ３ O ＋ ) This takes the form of an isohydrous molecule. In this embodiment, protons and the ions obtained by the hydration of protons are collectively referred to as hydrogen ions.

[0018] Waste liquid containing water is discharged from the anode chamber 110. In addition to water, the waste liquid contains oxygen produced by the oxidation of water. The oxygen may be discharged in a dissolved form in the waste liquid or as a gas.

[0019] [Diaphragm] The diaphragm 130 is provided between the anode chamber 110 and the cathode chamber 120, separating the anode chamber 110 and the cathode chamber 120. The diaphragm 130 has the function of selectively allowing ions to pass through and suppressing the permeation of other substances. That is, the diaphragm 130 suppresses the mixing of the liquid present in the anode chamber 110 and the gas present in the cathode chamber 120. Examples of ion exchange membranes for the diaphragm 130 include Neosepta® manufactured by Astrom, Celemion® manufactured by AGC Inc., Aciplex® manufactured by Asahi Kasei Corporation, Fumatesp® and fumapem® manufactured by Fumatech, Nafion® manufactured by DuPont, which is a fluororesin obtained by sulfonating and polymerizing tetrafluoroethylene, Lewabrane® manufactured by LANXESS, Ionsep® manufactured by IONTECH, Mustang® manufactured by PALL, Ralex® manufactured by mega, and Gore-Tex® manufactured by Gore-Tex. In addition, an ion exchange membrane constructed using a membrane with a hydrocarbon as its basic skeleton or a membrane having an amine group may be used as the diaphragm 130. Furthermore, a bipolar membrane formed by laminating a cation exchange membrane and an anion exchange membrane, or an anion exchange membrane, may be used as the diaphragm 130. The following explanation will focus on examples using a membrane that selectively allows cations to pass through (cation exchange membrane) as the diaphragm 130.

[0020] As the separator 130, in addition to those described above, examples include: silicone resins; fluorine-based resins such as perfluoroalkoxyalkane (PFA), perfluoroethylene propene copolymer (FEP), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE); polyester sulfone (PES); glass filters; fillers filled with agar, etc.; insulating porous membranes such as zeolite, oxides, filter paper, and the like.

[0021] [Cathode Chamber] The cathode chamber 120 includes a cathode electrode 122. The cathode chamber 120 has a space into which gaseous nitrogen is supplied. When the separator 130 is a cation exchange membrane, at the cathode electrode 122, a forward reaction for synthesizing ammonia from a hydrogen source and nitrogen and H ２ a side reaction that produces occurs. 2H ＋ +2e － →H ２ ... (2) N ２ +6H ＋ +6e － →2NH ３ ... (3) The electrons consumed in the reaction are supplied from the anode chamber 110 via an external circuit, and the hydrogen ions consumed in the reaction are supplied from the anode chamber 110 via the separator 130. Since the cathode electrode 122 includes an ammonia synthesis catalyst described later, the reaction of formula (3) proceeds more preferentially than the reaction of formula (2). Note that the hydrogen source is, for example, hydrogen ions. The hydrogen source is generated in the anode chamber 110 and supplied to the cathode chamber 120 via the separator 130. The hydrogen source is obtained, for example, by an electrolysis reaction of water in the anode chamber 110. Note that when the separator 130 is an anion exchange membrane, at the cathode electrode 122, N ２ +6H ２ O+6e － →2NH ３ +6OH －According to the reaction equation, a reaction occurs in which ammonia is synthesized from a hydrogen source and nitrogen. Furthermore, if the diaphragm 130 is a porous membrane, the same ammonia synthesis reaction as in the cases of both cation exchange membranes and anion exchange membranes may occur.

[0022] From the cathode chamber 120, a gas containing gaseous ammonia produced by the reaction of formula (3) is discharged. In addition to gaseous ammonia, the gas also contains gaseous nitrogen and gaseous hydrogen.

[0023] The cathode electrode 122 may be positioned to cover the entire surface of the diaphragm 130 on the cathode chamber 120 side. The cathode electrode 122 contains an ammonia synthesis catalyst. Figures 2A to 2C are schematic enlarged views showing different examples of the vicinity of the cathode electrode in this embodiment. As shown in Figure 2A, the cathode electrode 122 may comprise a gas diffusion layer 1221, an ammonia synthesis catalyst 1222, a carrier 1223, and a binder 1224. Alternatively, as shown in Figure 2B, the cathode electrode 122 may comprise a gas diffusion layer 1221, an ammonia synthesis catalyst 1222, a carrier 1223, a binder 1224, and a water-absorbing component 1225. Or, as shown in Figure 2C, the cathode electrode 122 may comprise a gas diffusion layer 1221, an ammonia synthesis catalyst 1222, a carrier 1223, a binder 1224, and a water-repellent component 1226.

[0024] The gas diffusion layer 1221 has a plurality of pores and is provided on the cathode electrode 122 on the side of the space where gaseous nitrogen exists in the cathode chamber 120. The gas diffusion layer 1221 can efficiently bring the nitrogen in the cathode chamber 120 into contact with the ammonia synthesis catalyst 1222. The gas diffusion layer 1221 is preferably conductive. Such a gas diffusion layer 1221 is not particularly limited, but examples include carbon paper, carbon cloth, and carbon felt. These may be used individually or in combination of two or more. The gas diffusion layer 1221 may be, for example, a gas diffusion electrode that functions as an electrode.

[0025] The ammonia synthesis catalyst 1222, the carrier 1223, and the binder 1224, and optionally the water-absorbing component 1225 or the water-repellent component 1226, may be uniformly mixed by known methods. The mixture, in which the ammonia synthesis catalyst 1222, the carrier 1223, and the binder 1224, and optionally the water-absorbing component 1225 or the water-repellent component 1226 are uniformly mixed, may be placed on the side of the gas diffusion layer 1221 facing the diaphragm 130 (for example, on the surface of the gas diffusion layer 1221 facing the diaphragm 130).

[0026] The ammonia synthesis catalyst 1222 promotes the reaction for synthesizing ammonia from nitrogen. Examples of the ammonia synthesis catalyst 1222 include molybdenum complexes. A molybdenum complex is a compound in which the central metal is molybdenum and ligands are coordinated to the molybdenum.

[0027] Examples of ligands for molybdenum complexes include halide ions and tertiary phosphines. Preferably, the ligand is a combination of a pincer ligand (i.e., a ligand in which three coordinating atoms are bonded from three directions on the same plane including the central metal) and a halide ion, more preferably a combination of a PCP (phosphorus-carbon-phosphorus) type pincer ligand or a PNP (phosphorus-nitrogen-phosphorus) type pincer ligand and a halide ion, and even more preferably a combination of a PCP type pincer ligand and a halide ion.

[0028] The above metal complex is not particularly limited, but examples include metal complexes that combine the above central metal with the above ligand. As for the above metal complex, a molybdenum complex having a pincer ligand and a halide ion as ligands is more preferred, a molybdenum complex having a PCP-type pincer ligand or a PNP-type pincer ligand and a halide ion as ligands is even more preferred, and a molybdenum complex having a PCP-type pincer ligand and a halide ion as ligands is even more preferred.

[0029] Examples of molybdenum complexes having a PNP-type pincer ligand and a halide ion as ligands include the molybdenum complex represented by the following formulas (3-1) or (3-2). Examples of molybdenum complexes having a PCP-type pincer ligand and a halide ion as ligands include the molybdenum complex represented by the following formulas (3-3) or (3-4). Other examples of molybdenum complexes include the molybdenum complex represented by the following formula (3-5).

[0030]

[0031] In the above equations (3-1) to (3-5), R １８ , R １９ , R ２０ , and R ２１ (Hereinafter referred to as “R １８ ~R ２１ This is written as ). ) each independently represents a hydrogen atom, or a monovalent hydrocarbon group having 1 to 36 or 1 to 14 carbon atoms in a chain, cyclic or branched configuration. Here, R １８ and R １９ , and / or R ２０ and R ２１ They may be bonded to each other to form a ring, PR １８ R １９ PR ２０ R ２１ It may be the same or different, R １８ ~R ２１ They may all be the same, or at least some may be different. ２２ R represents a hydrogen atom, or a monovalent hydrocarbon group having 1 to 36 or 1 to 14 carbon atoms in a chain, cyclic, or branched configuration. m1 is an integer from 0 to 3. m2 is an integer from 0 to 4, preferably an integer from 0 to 2. ２２ If there are two or three of these R ２２ They may be bonded to each other to form a ring. Also, R ２２ If there are two or three of them, they may all be the same, or at least some of them may be different. １８ ~R ２１ and R ２２In this context, the "linear, cyclic, or branched monovalent hydrocarbon group having 1 to 36 or 1 to 14 carbon atoms" can be selected from, for example, alkyl groups having 1 to 36 or 1 to 6 carbon atoms; alkenyl groups having 2 to 36 or 2 to 6 carbon atoms; alkynyl groups having 2 to 36 or 2 to 6 carbon atoms; cycloalkyl groups having 3 to 36 or 3 to 6 carbon atoms; cycloalkenyl groups having 3 to 36 or 3 to 6 carbon atoms; cycloalkynyl groups having 3 to 36 or 3 to 6 carbon atoms; aryl groups having 6 to 36 or 6 to 14 carbon atoms; alkoxy groups having 1 to 36 or 1 to 6 carbon atoms; and phenyl or naphthyl groups which may have at least one substituent selected from the group consisting of a hydroxyl group, a halogen atom, and a perfluoromethyl group. Among these, R １８ ~R ２１ As such, alkyl groups having 1 to 6 carbon atoms are preferred, and alkyl groups having 1 to 4 carbon atoms are more preferred. Also, R １８ ~R ２１ A butyl group is more preferred, and a tert-butyl group is particularly preferred. １８ ~R ２１A monovalent polycyclic aromatic hydrocarbon ring is preferred. The monovalent polycyclic aromatic hydrocarbon ring may be a monovalent group derived from a ring selected from the group consisting of phenalene, phenanthrene, anthracene, pyrene, chrysene, naphthacene, triphenylene, benz[a]anthracene, picene, perylene, pentaphene, pentacene, benzo[a]pyrene, benzo[e]pyrene, hexaphene, 1,12-benzoperylene, and hexacene. The polycyclic aromatic hydrocarbon ring may be a monovalent group derived from one or more rings selected from the group consisting of terphenyl or quaterphenyl, which are polycyclic aromatic hydrocarbon rings formed by the single bonding of monocyclic aromatic hydrocarbon rings. The polycyclic aromatic hydrocarbon ring may be a monovalent group derived from a ring in which a polycyclic aromatic hydrocarbon ring formed by the condensation of monocyclic aromatic hydrocarbon rings (for example, the polycyclic aromatic hydrocarbon rings exemplified above) and a monocyclic aromatic hydrocarbon ring are bonded by a single bond. Among these, from the viewpoint of more effectively and reliably achieving the effects of this disclosure, a monovalent group derived from pyrene or a monovalent group derived from a polycyclic aromatic hydrocarbon ring in which a benzene ring is single-bonded to pyrene is preferred. Z represents a structure represented by the following formulas (i) to (iii).

[0032]

[0033] In the formula, X Ｈ The arrows indicate halogen atoms. The dashed lines indicate bonds to adjacent atoms. A halogen is selected from the group consisting of fluorine, chlorine, bromine, and iodine.

[0034] In the formula, Y represents the counterion. The counterion Y is not particularly limited, but for example, the triflate ion (OTf － ), PF ６ － BF ４ － , tetrakis(3,5-bis(trifluoromethyl)phenyl)borate ion (Bar Ｆ ４ － ), bis(trifluoromethanesulfonyl)imide ion (NTf ２ － ), N (SO ２ F) ２－ It represents chloride ions, bromide ions, or iodide ions.

[0035] Furthermore, it is preferable that the molybdenum complex contains one or more compounds represented by the following formulas (8-1) to (8-3).

[0036]

[0037] In the formula, tBu represents a tert-butyl group.

[0038] The carrier 1223 supports the ammonia synthesis catalyst 1222 on its surface. The carrier 1223 may have pores on its surface. In that case, the ammonia synthesis catalyst 1222 may be supported within these pores. The carrier 1223 is not particularly limited as long as it is conductive, but examples include porous carbon particles. Examples of such porous carbon particles include channel black, furnace black, thermal black, acetylene black, activated carbon, natural graphite, artificial graphite, graphitized carbon, graphene, carbon nanotubes, fullerene, Ketjenblack, and glassy carbon. The carrier 1223 may be used alone or in combination of two or more types.

[0039] The binder 1224 binds the ammonia synthesis catalyst 1222 and the support 1223 within the cathode electrode 122. This fixes the ammonia synthesis catalyst 1222 and the support 1223 within the cathode electrode 122, preventing them from detaching from the cathode electrode 122. The binder is not particularly limited, but examples include polymer materials. More specifically, examples of polymer materials include polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, and carboxymethylcellulose, and the polymer material may be an ionomer. The ionomer is not particularly limited, but examples include ionomers having proton conductivity. A specific example of such an ionomer is Nafion® manufactured by DuPont. The use of an ionomer facilitates the movement of hydrogen ions within the cathode electrode 122. Ionomers have a polymer with positively charged metal ions and negatively charged functional groups. It is thought that positively charged hydrogen ions move more easily due to Coulomb attraction with the negatively charged functional groups and Coulomb repulsion with the positively charged metal ions, but the cause is not limited to this. In addition, anion conductive ionomers may be used. Binder 1224 may be used alone or in combination of two or more types.

[0040] Although the binder 1224 does not necessarily have to be conductive, conductive materials such as the gas diffusion layer 1221 and the carrier 1223 are electrically connected to each other within the cathode electrode 122, so the cathode electrode 122 as a whole is conductive.

[0041] The water-absorbing component 1225 and the water-repellent component 1226 will be described in detail later.

[0042] The content of the ammonia synthesis catalyst 1222 is 0.01 to 50 mg / cm³ in the cathode electrode 122. ２ Preferably, the concentration is 0.05 to 40 mg / cm³. ２ It is more preferable that the concentration be 0.1 to 30 mg / cm³. ２ It is even more preferable that the ammonia synthesis catalyst content is 0.01 mg / cm³. ２In these cases, the amount of ammonia produced tends to increase.

[0043] In this specification, the content of the ammonia synthesis catalyst 1222 can be measured, for example, using ICP-MS (inductively coupled plasma mass spectrometry) or XRF (X-ray fluorescence analysis).

[0044] The content of the carrier 1223 in the cathode electrode 122 is preferably 0.1 mg / cm³. ２ 10mg / cm or more ２ The following applies:

[0045] The binder 1224 content in the cathode electrode 122 is preferably 0.1 mg / cm³. ２ 10mg / cm or more ２ The following applies:

[0046] [Cathode Electrode Drying Means] The ammonia production apparatus 100 is equipped with a cathode electrode drying means 150 for drying the cathode electrode 122. The cathode electrode drying means 150 dries the cathode electrode 122 to prevent liquid water from adhering to the cathode electrode 122.

[0047] The aforementioned membrane 130 is almost impermeable to substances other than ions, but it may allow small amounts of other substances to pass through. For example, if the concentration of water in the anode chamber 110, which is separated from the cathode chamber 120 by the membrane 130, is higher than the concentration of water in the cathode chamber 120, this concentration difference may act as a driving force, causing water to move from the anode chamber 110 to the cathode chamber 120 through the membrane 130. Also, protons generated at the anode electrode 112 are hydrated to form water molecules such as hydronium, and these water-containing protons move from the anode chamber 110 to the cathode chamber 120 through the membrane 130. Then, in the cathode chamber 120, when nitrogen and protons with water molecules react to produce ammonia, water is also produced simultaneously, resulting in the presence of liquid water. In this regard, the ammonia production apparatus 100 of this embodiment is equipped with a cathode electrode drying means 150, which can immediately dry the liquid water generated in the cathode chamber 120. Therefore, it is possible to suppress the alteration of the ammonia synthesis catalyst 1222 by liquid water, the coating of the ammonia synthesis catalyst 1222 by water, and the dissolution of the generated gaseous ammonia into the liquid water. In other words, ammonia can be produced efficiently, and production costs can be reduced.

[0048] The cathode electrode drying means 150 is not particularly limited as long as it dries the cathode electrode 122 and prevents liquid water from adhering to the cathode electrode 122, but examples include nitrogen flow rate adjustment means 150a, cathode chamber temperature adjustment means 150b, and nitrogen gas temperature adjustment means 150c.

[0049] By reducing the partial pressure of water vapor in the cathode chamber 120, the boiling point of water is lowered, and the amount of liquid water in the cathode chamber 120 decreases. From this perspective, by increasing the flow rate of gaseous nitrogen supplied to the cathode chamber 120 by the nitrogen flow rate adjustment means 150a, the cathode chamber 120 is dried, and the cathode electrode 122 is also dried, thereby suppressing the adhesion of liquid water to the cathode electrode 122. In the nitrogen flow rate adjustment means 150a, for example, a method of opening an adjustment valve that adjusts the flow rate of gaseous nitrogen is used. The flow rate of gaseous nitrogen in the nitrogen flow rate adjustment means 150a is, for example, 10 mL / min or more and 5000 mL / min or less.

[0050] Furthermore, increasing the temperature inside the cathode chamber 120 also reduces the amount of liquid water inside the cathode chamber 120. From this perspective, by increasing the temperature inside the cathode chamber 120 using the cathode chamber temperature adjustment means 150b, the cathode chamber 120 is dried, and the cathode electrode 122 is also dried, thereby suppressing the adhesion of liquid water to the cathode electrode 122. When increasing the temperature inside the cathode chamber 120 using the cathode chamber temperature adjustment means 150b, methods that directly increase the temperature inside the cathode chamber 120 are used, such as resistance heating, which utilizes the resistance heat obtained by passing current through a resistor, or electromagnetic wave heating, which utilizes electromagnetic waves such as infrared rays or microwaves. Figure 1 shows a configuration in which a resistor is installed inside the cathode chamber 120 and the temperature inside the cathode chamber 120 is directly increased by resistance heating. The temperature in the cathode chamber temperature adjustment means 150b is, for example, 0°C to 80°C.

[0051] Furthermore, by increasing the temperature of the nitrogen gas before supplying it into the cathode chamber 120, the temperature inside the cathode chamber 120 increases, reducing the amount of liquid water inside the cathode chamber 120 and suppressing the adhesion of liquid water to the cathode electrode 122. From this viewpoint, the nitrogen gas may be heated by the nitrogen gas temperature adjustment means 150c, and the heated nitrogen gas may be supplied into the cathode chamber 120 to raise the temperature inside the cathode chamber 120. This also dries the cathode chamber 120 and suppresses the adhesion of liquid water to the cathode electrode 122. The temperature in the nitrogen gas temperature adjustment means 150c is, for example, 0°C to 80°C.

[0052] Figure 1 shows an embodiment in which the power supply for applying voltage to the anode electrode 112 and the cathode electrode 122 and the power supply for heating the cathode chamber 120 are the same; however, the two power supplies may be provided separately.

[0053] Figure 1 shows an ammonia production apparatus 100 equipped with a cathode electrode drying means 150a, a cathode chamber temperature adjustment means 150b, and a nitrogen gas temperature adjustment means 150c. However, the ammonia production apparatus may be equipped with only one of these means as the cathode electrode drying means 150, or with any two or more means. Furthermore, the ammonia production apparatus may have multiple nitrogen flow rate adjustment means 150a, cathode chamber temperature adjustment means 150b, and nitrogen gas temperature adjustment means 150c. For example, the ammonia production apparatus may be equipped with two or more valves as the nitrogen flow rate adjustment means 150a for adjusting the flow rate of gaseous nitrogen supplied to the cathode chamber. Furthermore, the ammonia production apparatus may be equipped with means for performing heating by resistance heating and means for performing heating by electromagnetic wave heating as the cathode chamber temperature adjustment means 150b. Furthermore, the ammonia production apparatus may be equipped with means for performing heating by resistance heating and means for performing heating by electromagnetic wave heating as the nitrogen gas temperature adjustment means 150c.

[0054] If the temperature inside the cathode chamber 120 rises too high, the diaphragm 130 in contact with the cathode chamber 120 may be exposed to high temperatures and deteriorate. From this viewpoint, the ammonia production apparatus of this embodiment may be equipped with a cathode chamber cooling means that promotes drying of the cathode electrode 122 while lowering the temperature inside the cathode chamber 120 to an extent that does not cause deterioration of the diaphragm 130. Examples of cathode chamber cooling means include using a tube through which a cooling liquid flows and installing the tube inside the cathode chamber 120 to lower the temperature inside the cathode chamber 120 by heat exchange; and cooling nitrogen gas before supplying it to the cathode chamber 120 to lower the temperature inside the cathode chamber 120. From the viewpoint of drying the cathode electrode 122 and suppressing deterioration of the diaphragm 130, the temperature inside the cathode chamber 120 is preferably 25°C to 100°C, more preferably 30°C to 90°C, and even more preferably 40°C to 80°C.

[0055] [Ammonia Separation Means] The ammonia production apparatus 100 may include an ammonia separation means 170 for separating the ammonia synthesized from the gas discharged from the cathode chamber 120. The gas discharged from the cathode chamber 120 contains gaseous ammonia, as well as gaseous nitrogen, gaseous hydrogen, and water (e.g., water vapor). The ammonia separation means 170 separates gaseous ammonia from the gas. The ammonia separation means 170 is not particularly limited, but for example, ammonia may be separated by cryogenic separation. In addition to ammonia, if nitrogen, hydrogen, and water vapor are to be separated in the ammonia separation means 170, the ammonia may be separated by cryogenic separation, and then the nitrogen, hydrogen, and water vapor may be separated by pressure swing adsorption.

[0056] The separation method is not particularly limited, but for example, distillation, stripping, membrane separation, absorption, chemical separation, cooling condensation, and ion exchange can be used.

[0057] The ammonia production apparatus 200 of this embodiment may also include a nitrogen separation means 160, as shown in Figure 3. The nitrogen separation means 160 will be described in detail below. Elements that are the same as those already described will be given the same numbering and their descriptions will be omitted unless otherwise specified.

[0058] [Nitrogen Separation Means] The nitrogen separation means 160 separates nitrogen from a nitrogen-containing mixed gas such as air. The nitrogen separation means 160 may be supplied with nitrogen by being directly connected to the cathode chamber 120 or the nitrogen flow rate adjustment means 150a via gas piping or the like, or the nitrogen obtained by the nitrogen separation means 160 may be stored in a gas cylinder or the like, and then supplied from the gas cylinder to the cathode chamber 120 or the nitrogen flow rate adjustment means 150a. In the nitrogen separation means 160, nitrogen is separated from the nitrogen-containing mixed gas by using methods such as cryogenic separation, which utilizes the difference in boiling points; adsorption separation, which utilizes the difference in adsorption characteristics of zeolite-based adsorbents for gas molecules; or membrane separation, which utilizes the fact that the permeation rate of the membrane differs depending on the gas molecule.

[0059] The ammonia production apparatus 300 of this embodiment may include an anode chamber temperature adjustment means 140 for adjusting the temperature of the anode chamber 110, as shown in Figure 4. The anode chamber temperature adjustment means 140 will be described in detail below. Elements that are the same as those already described will be given the same numbering and their descriptions will be omitted unless otherwise specified.

[0060] [Anode Chamber Temperature Adjustment Means] By equipping the anode chamber temperature adjustment means 140 in the ammonia production apparatus, the temperature inside the anode chamber 110 can be adjusted, and the temperature of the cathode chamber 120, which is adjacent to the anode chamber 110 via the diaphragm 130, can also be easily adjusted. As a result, the cathode chamber 120 can be dried, and the adhesion of liquid water to the cathode electrode 122 can be suppressed. Furthermore, the presence of liquid water inside the cathode chamber 120 can be suppressed.

[0061] The anode chamber temperature adjustment means 140 is not particularly limited as long as it can adjust the temperature inside the anode chamber 110. Examples include a water temperature adjustment means 140a that adjusts the temperature of the water supplied to the anode chamber 110 before supply, and an anode chamber temperature adjustment means 140b that directly adjusts the temperature inside the anode chamber 110. Figure 4 shows a configuration in which water heated by the water temperature adjustment means 140a is supplied to the anode chamber 110, and a resistor, which is the anode chamber temperature adjustment means 140b, is installed inside the anode chamber 110 to directly heat the inside of the anode chamber 110 by resistive heating. In addition, the temperature inside the anode chamber 110 may be lowered from the viewpoint of suppressing deterioration of the diaphragm 130 in contact with the anode chamber 110 due to high temperatures, and from the viewpoint of suppressing evaporation of the water, which is the electrolyte in the anode chamber 110. In this case, although not shown in the figures, water cooled by the water temperature adjustment means 140a may be supplied to the anode chamber 110, or the temperature inside the anode chamber 110 may be lowered by the anode chamber temperature adjustment means. Specifically, the water temperature adjustment means 140a can be a means for adjusting the temperature of the water supplied into the anode chamber 110 to 25°C or more and 100°C or less, more preferably 30°C or more and 90°C or less, and even more preferably 40°C or more and 80°C or less.

[0062] Figure 4 shows an embodiment in which the power supply for applying voltage to the anode electrode 112 and the cathode electrode 122, the power supply for adjusting the temperature in the anode chamber 110, and the power supply for adjusting the temperature in the cathode chamber 120 are the same. However, the three power supplies may each be provided separately, or two of the three power supplies may be the same and the remaining power supply may be provided separately.

[0063] Figure 4 shows an ammonia production apparatus 300 equipped with a water temperature adjustment means 140a and an anode chamber temperature adjustment means 140b. However, the ammonia production apparatus may be equipped with only one of these means. Furthermore, the ammonia production apparatus may have multiple water temperature adjustment means 140a and multiple anode chamber temperature adjustment means 140b. For example, the ammonia production apparatus may be equipped with means for performing heating by resistance heating and means for performing heating by electromagnetic wave heating as the water temperature adjustment means 140a and anode chamber temperature adjustment means 140b.

[0064] In the ammonia production apparatus 400 of this embodiment, as shown in Figure 5, water may be extracted from the waste liquid from the anode chamber 110 and reused. In this case, the ammonia production apparatus 400 may be equipped with a water separation means 180. The water separation means 180 will be described in detail below. Elements that are the same as those already described will be given the same numbering and their descriptions will be omitted unless otherwise specified.

[0065] [Water Separation Means] In the water separation means 180, water is separated and extracted from the waste liquid containing water, dissolved oxygen in the water, and gaseous oxygen. The water separation means 180 is not particularly limited, but for example, a gas-liquid separation method may be used to remove oxygen from the waste liquid and separate and extract water. When using a gas-liquid separation method, oxygen may be removed from the waste liquid in a gas-liquid separation tank and then the water may be separated and extracted.

[0066] In Figure 5, the ammonia production apparatus 400 is equipped with a water temperature adjustment means 140a, and the water separated and extracted from the waste liquid is returned to the water temperature adjustment means 140a. On the other hand, if the ammonia production apparatus 400 is not equipped with a water temperature adjustment means 140a, a pipe for supplying water to the anode chamber 110 may be connected to a pipe for supplying water extracted from the waste liquid in the water separation means 180.

[0067] In the ammonia production apparatus 500 of this embodiment, as shown in Figure 6, gaseous nitrogen contained in the exhaust gas obtained from the ammonia separation means 170 may be reused. The following describes in detail the manner in which gaseous nitrogen is reused. Elements that have already been described will be given the same numbering and their descriptions will be omitted unless otherwise specified.

[0068] In Figure 6, hydrogen, water (e.g., water vapor), ammonia, and nitrogen are separated in the ammonia separation means 170, and the separated nitrogen is returned to the nitrogen flow rate adjustment means 150a. On the other hand, if the ammonia production apparatus 500 does not have a nitrogen flow rate adjustment means 150a, a pipe for supplying nitrogen separated from the exhaust gas in the ammonia separation means 170 may be connected to the pipe supplying gaseous nitrogen to the cathode chamber 120. Also, if only ammonia is separated in the ammonia separation means 170 and hydrogen, water vapor, and nitrogen are not separated, a device for separating nitrogen from hydrogen and water vapor may be provided between the ammonia separation means 170 and the nitrogen flow rate adjustment means 150a. Alternatively, a pipe for supplying a gas containing hydrogen, water vapor, and nitrogen from the ammonia separation means 170 may be connected to the nitrogen separation means 160. Examples of methods for separating nitrogen from hydrogen and water vapor include cryogenic separation, adsorption separation, and membrane separation.

[0069] The cathode electrodes 122 and 122' of this embodiment may have a water-repellent component 1226, as shown in Figures 2C and 7. Water repellency means, for example, that the contact angle with water is 90° or greater. Furthermore, the cathode electrodes 122 and 122' may have a water-absorbing component 1225 that can absorb water in the cathode chamber 120, as shown in Figures 2B and 7. Moreover, the cathode electrode 122' of this embodiment may contain both the water-absorbing component 1225 and the water-repellent component 1226, as shown in Figure 7. The water-repellent component 1226 and the water-absorbing component 1225 will be described in detail below. Elements identical to those already described will be given the same numbering and their descriptions will be omitted unless otherwise specified.

[0070] The aforementioned diaphragm 130 is almost impermeable to substances other than ions, but it may allow a small amount of other substances to pass through. For example, if the concentration of water in the anode chamber 110, which is separated from the cathode chamber 120 by the diaphragm 130, is higher than the concentration of water in the cathode chamber 120, this concentration difference may act as a driving force, causing water to move from the anode chamber 110 to the cathode chamber 120 through the diaphragm 130. In this regard, the presence of the water-repellent component 1226 in the cathode electrodes 122 and 122' suppresses the entry of water into the cathode electrodes 122 and 122'. As a result, it is possible to suppress contact between the liquid water that has moved from the anode chamber 110 to the cathode chamber 120 via the diaphragm 130 and the ammonia synthesis catalyst 1222 in the cathode electrodes 122 and 122'. Therefore, it is possible to suppress the liquid water from altering the ammonia synthesis catalyst 1222 or the ammonia synthesis catalyst 1222 from being coated with water. In other words, ammonia can be produced efficiently.

[0071] The water-repellent component 1226 is not particularly limited as long as it has water-repellent properties, but examples include water-repellent metal organic frameworks (MOFs), organic polymer water-repellent materials, and inorganic water-repellent materials. Preferred water-repellent MOFs are those consisting of a low-polarity organic skeleton or those having fluorine-containing groups such as fluorinated organic linkers. Specifically, examples include ZIF (zeolitic imidazolate framework)-71, MIL-40B, and Zn(tbip). Examples of organic polymer-based water-repellent materials include fluororesins and silicone resins. Examples of fluororesins include PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), FEP (perfluoroetherpropylene copolymer), ETFE (ethylene tetrafluoroethylene), PCTFE (polychlorotrifluoroethylene), and ECTFE (ethylene chlorotrifluoroethylene). Examples of silicone resins include PDMS (polydimethylsiloxane). Examples of inorganic water-repellent materials include water-repellent silica, hydrophobic oxides, and hydrophobic zeolites. Examples of water-repellent silica include silylated surface-treated silica, fluorinated silica, and silica aerogel. Examples of hydrophobic oxides include hydrophobic aluminum oxide. Examples of hydrophobic zeolites include ZSM-5.

[0072] Furthermore, because the cathode electrodes 122 and 122' have a water-absorbing component 1225, even if water passes through the membrane 130 from the anode chamber 110 to the cathode chamber 120, the water-absorbing component 1225 absorbs the water. This prevents the water from altering the ammonia synthesis catalyst 1222 and prevents the generated gaseous ammonia from dissolving into the liquid water. In other words, ammonia can be produced efficiently.

[0073] The water-absorbing component 1225 is not particularly limited as long as it can absorb liquid water, but examples include water-absorbing polymers such as sodium polyacrylate, potassium polyacrylate, and polyvinyl alcohol; and water-absorbing inorganic materials such as calcium oxide and calcium chloride.

[0074] The water-absorbing component 1225 is not particularly limited, but examples include water-absorbing polymers, water-absorbing inorganic materials (hereinafter also referred to as "inorganic desiccant"), and other water-absorbing materials.

[0075] The superabsorbent polymer is not particularly limited, but examples include sodium polyacrylate, potassium polyacrylate, and polyvinyl alcohol as mentioned above, as well as polyacrylamide and its copolymers, crosslinked carboxymethylcellulose, ethylene-maleic anhydride copolymer, and crosslinked polyethylene glycol.

[0076] Inorganic desiccants are not particularly limited, but examples include calcium oxide and calcium chloride as mentioned above, as well as silica gel, synthetic zeolite (molecular sieve), and clay-based desiccants (bentonite, etc.).

[0077] Other water-absorbing materials include, but are not limited to, biodegradable superabsorbent polymers and water-absorbing metal-organic frameworks (MOFs). Examples of biodegradable superabsorbent polymers include starch. Examples of water-absorbing MOFs include those that are stable to water and have exposed metal coordination unsaturated sites, and those with hydrophilic functional groups (-OH, -COOH, -NH). ２ Preferably, the material has (etc.) or extremely fine pores (about a few Å) that allow water to condense easily at low relative humidity. Specifically, MOF-801, Mg-MOF-74, UiO-66-NH ２ Examples include UiO-66-OH and MIL-101(Cr).

[0078] The content of the water-absorbing component 1225 in the cathode electrode 122 is not particularly limited, but for example, 0.1 mg / cm³. ２ 5mg / cm or more ２ The following is the result. This tends to allow for a balance between the water absorption properties of the cathode electrode 122 and its function as an electrode.

[0079] The amount of water-repellent component 1226 in the cathode electrode 122 is not particularly limited, but for example, 0.1 mg / cm². ２ 5mg / cm or more ２The following is the result. This tends to allow for a balance between the water-repellent properties of the cathode electrode 122 and its function as an electrode.

[0080] There are no particular limitations on the method for preparing the cathode electrode 122', but for example, the following method can be used. That is, first, a carrier 1223 is attached to the gas diffusion layer 1221. Then, the ammonia synthesis catalyst 1222 is supported on the carrier 1223. Then, a binder 1224, a water-absorbing component 1225, and a water-repellent component 1226 are attached to the gas diffusion layer 1221, and the carrier 1223, binder 1224, water-absorbing component 1225, and water-repellent component 1226 are fixed to one side of the gas diffusion layer 1221 to prepare the cathode electrode 122'. Alternatively, first, the ammonia synthesis catalyst 1222 is supported on the carrier 1223. Then, the carrier 1223 supporting the ammonia synthesis catalyst 1222, the binder 1224, the water-absorbing component 1225, and the water-repellent component 1226 are mixed to obtain a mixture. Next, the mixture is attached to the gas diffusion layer 1221, fixing the ammonia synthesis catalyst 1222, the carrier 1223, the binder 1224, the water-absorbing component 1225, and the water-repellent component 1226 to one side of the gas diffusion layer 1221, thereby preparing the cathode electrode 122'.

[0081] The ammonia production apparatus 600 of this embodiment may include a separation device 192, as shown in Figure 8, or it may include a gas-liquid separator 191 and a separation device 192. The gas-liquid separator 191 is a device that receives at least the mixture of this embodiment (hereinafter also simply referred to as "the mixture"), which includes ammonia and water, and gaseous nitrogen and hydrogen, and separates the gas from a liquid containing at least the mixture. The separation device 192 is a device that separates at least one of ammonia and water from the mixture generated in the cathode chamber 120.

[0082] When liquid water is generated in the cathode chamber 120, gaseous ammonia may dissolve slightly in the liquid water within the cathode chamber 120. Even in this case, the separation device 192 can separate the water and ammonia from the mixture. This allows for the efficient acquisition of, for example, highly purified ammonia.

[0083] The following provides a detailed explanation of the gas-liquid separator 191 and the separator 192. Elements identical to those already described will be given the same numbering and their explanations will be omitted unless otherwise specified.

[0084] [Gas-Liquid Separator] When gaseous ammonia dissolves slightly in liquid water within the cathode chamber 120, the discharged material from the cathode chamber 120 contains a mixture and gas (in Figure 8, “N ２ / H ２ / NH ３ (G) / H ２ O / NH ３ (L)"), the discharge is supplied to the gas-liquid separator 191. Here, "liquid containing at least the mixture" contains at least the mixture of this embodiment, and may also contain other liquids discharged from the cathode chamber 120. The discharge supplied to the gas-liquid separator 191 is separated by a gas-liquid separation means (not shown) into a liquid containing the mixture of this embodiment, gaseous nitrogen, gaseous hydrogen, and gaseous ammonia. Performing gas-liquid separation before separating water and ammonia from the mixture by the separator 192 can, for example, increase the stripping efficiency described later or improve the accuracy of the process.

[0085] There are no particular limitations on the gas-liquid separation means in the gas-liquid separation apparatus 191, and known gas-liquid separation means can be used. Examples of gas-liquid separation means include gravity separators, centrifuges, flash tanks (flash drums), gas separation layers, knockout drums (demisters), etc. Although not particularly limited, for example, when separating water and ammonia by stripping in the separation apparatus 192, gravity separation, knockout drums, flash tanks, etc. can be suitably used as the gas-liquid separation means in the gas-liquid separation apparatus 191.

[0086] In the gas-liquid separation device 191, the liquid containing the mixture and the separated gas (in Figure 8, “N ２ / H ２ / NH ３(G)" may be discharged from, for example, the vicinity of the top of the gas-liquid separator 191 and supplied to the first gas separation means 194. Further, for example, a liquid containing a mixture (in FIG. 8, "H ２ O / NH ３ (L)" may be discharged. The liquid containing the mixture discharged from the gas-liquid separator 191 may be supplied to the separator 192.

[0087] [First and Second Gas Separation Means] When the ammonia production apparatus 600 of the present embodiment includes the gas-liquid separator 191 as shown in FIG. 8, it may further include a first gas separation means 194 and a second gas separation means 195.

[0088] The first gas separation means 194 is supplied with the gas discharged from the gas-liquid separator 191. The gas contains nitrogen, hydrogen, and gaseous ammonia. The first gas separation means 194 is an apparatus that separates nitrogen and hydrogen from gaseous ammonia in the supplied gas. The separation method used in the first gas separation means 194 is not particularly limited, and any known means capable of separating nitrogen and hydrogen from gaseous ammonia can be used, for example, cryogenic separation can be used. However, the separation method of the first gas separation means is not limited to this embodiment.

[0089] The gas separated from ammonia in the first gas separation means 194 (in FIG. 8, "N ２ / H ２ ") is discharged from the first gas separation means 194 and supplied to the second gas separation means 195. Further, the ammonia separated in the first gas separation means 194 is liquid ammonia, gaseous ammonia, or a mixture thereof (in FIG. 8, "NH ３ (G / L)"), and is discharged out of the first gas separation means 194. The ammonia discharged from the first gas separation means 194 is then subjected to further ammonia purification treatment as needed and recovered as high-purity ammonia.

[0090] The second gas separation means 195 is supplied with the gas discharged from the first gas separation means 194. This gas contains nitrogen and hydrogen. The second gas separation means 195 is a device that separates nitrogen and hydrogen from the supplied gas. The separation means in the second gas separation means 195 is not particularly limited, and known means capable of separating nitrogen and hydrogen can be used, such as membrane separation or pressure swing adsorption. However, the separation means in the second gas separation means 195 is not limited to this embodiment.

[0091] The nitrogen and hydrogen gases separated in the second gas separation means 195 are discharged separately. The nitrogen gas discharged from the second gas separation means 195 can be reused as a cathode raw material for the ammonia production apparatus 600 or as a separated gas used in the separation apparatus 192 described later. The hydrogen gas discharged from the second gas separation means 195 can be reused within the apparatus or used in another process described later. In particular, if the Faraday efficiency in the system becomes low, the amount of hydrogen may reach a considerable amount. In this case, for example, it can be effectively utilized for other processes (green ammonia production (water electrolysis and Haber-Bosch process, etc.), synthetic fuel production (e-methanol, e-fuel, e-methane, e-propane, etc.)). Furthermore, one example of reusing the hydrogen gas discharged from the second gas separation means 195 is to supply hydrogen gas to the electrolyte on the anode side. When hydrogen gas is supplied to the anode side, H ２ →2H ＋ +2e － The reaction occurs, and the resulting proton moves to the cathode side, where it can be used in the ammonia production reaction.

[0092] [Separation device] The separation device 192 is a device for separating at least one of ammonia and water from the mixture of this embodiment generated in the cathode chamber 120. The means for separating ammonia and water are not particularly limited, and known separation methods can be used. Examples of means for separating ammonia and water include, for example, ammonia stripping, distillation, membrane separation, absorption, separation by chemical reaction, cooling condensation, and ion exchange. Among these, the ammonia stripping method can be used as a separation method from the viewpoint of obtaining gaseous ammonia with low energy and efficiency. For example, the separation device 192 using the ammonia stripping method as a separation method may be a device in which at least the mixture and the separation gas are supplied, and ammonia in the mixture is separated as gaseous ammonia. Hereinafter, an embodiment using the ammonia stripping method as the separation device 192 will be described as an example.

[0093] Ammonia stripping is a method of separating ammonia from a mixture containing ammonia and water by contacting the mixture with a separation gas. Specifically, because ammonia dissolved in an aqueous solution is highly volatile, it can be removed by contacting it with a separation gas under appropriate conditions, thereby transferring the ammonia from the aqueous solution to the separation gas (gas phase).

[0094] The separation device 192 may be, for example, a tower-shaped device with multiple trays installed inside. However, the separation device 192 is not limited to this configuration. The separation device 192 is supplied with a mixture and a separation gas. Although not particularly limited, the mixture can be supplied from near the top of the separation device 192, and the separation gas can be supplied from near the bottom of the separation device 192. In this case, the mixture (liquid) flows down from the top to the bottom of the separation device 192, while the separation gas flows backward from the bottom to the top of the separation device 192, resulting in a so-called counterflow system. This increases the contact time between the mixture and the separation gas, thereby improving the ammonia separation efficiency.

[0095] As described above, ammonia dissolved in water takes on both dissociative and non-dissociative forms depending on the pH, with non-dissociative ammonia (NH₄) being the active form. ３) has high volatility and is therefore likely to migrate to the gas phase, while dissociative ammonium ion (NH ４ ＋ ) is non-volatile and therefore has the property of being unlikely to migrate to the gas phase. The ratio of non-dissociative ammonia to dissociative ammonium ions in a mixture (i.e., the volatility of ammonia in water) mainly depends on the temperature and pH of the mixture in the present embodiment. For example, the higher the pH of the mixture, the more non-dissociative ammonia (NH ３ ) becomes dominant, which makes it easier for ammonia to migrate to the gas phase and allows stripping to proceed more effectively. On the other hand, when the pH is low, ammonia takes the form of ammonium ion (NH ４ ＋ ), which is non-volatile and therefore less likely to migrate to the gas phase. From this perspective, the pH of the mixture (liquid containing the mixture) supplied to the separation device 192 is preferably 8.0 or higher, more preferably 10.5 or higher, and even more preferably 11.0 or higher.

[0096] The pH of the mixture can be adjusted by known pH adjustment means such as adjusting the ammonia concentration in the mixture or introducing an acidic substance. However, from the perspective of simplifying and improving the efficiency of the system, it is preferable to adjust the pH of the mixture by adjusting the temperature of the mixture. The temperature of the mixture (liquid containing the mixture) is preferably 50°C or higher from the viewpoints of facilitating the generation of non-dissociative ammonia and making ammonia more likely to volatilize; furthermore, from the perspectives of suppressing the consumption of large amounts of energy for heating and suppressing water from volatilizing and migrating to the gas phase, a temperature of 50°C or higher and 90°C or lower is more preferable.

[0097] A separation gas is supplied to the separation device 192. By bringing the separation gas into contact with the mixture within the separation device 192, the non-dissociable ammonia in the mixture moves to the separation gas, and the water and ammonia can be separated. The separation gas is not particularly limited as long as it is a separation gas that can be used in the ammonia stripping method, but for example, nitrogen gas, water vapor, etc., can be used. Nitrogen gas has the advantage of being readily available as a separation gas because it is sufficiently present in the device as a raw material gas and is expected to be heated in the electrolytic cell when passing through the cathode side. Water vapor has the advantage of being cost-effective and readily available when it is assumed that a separate separation gas will be prepared for stripping. Figure 8 shows an example in which nitrogen is supplied to the separation device 192 as the separation gas. A separate gas for separation gas may be used as the separation gas, but gas used or produced in the ammonia production device 600 may also be reused. For example, since it is expected that the raw material gaseous nitrogen will flow in amounts greater than stoichiometric (for example, 1.5 times the normal amount or more), the gas containing residual gaseous nitrogen supplied to the cathode chamber 120 can also be used as the separation gas. The "residual gas" can be gaseous nitrogen immediately after being discharged from the cathode chamber 120, or gaseous nitrogen discharged from the second gas separation means 195 shown in Figure 8.

[0098] The temperature inside the separation device is preferably 50°C or higher, and more preferably between 50°C and 90°C, from the viewpoint of maintaining the temperature of the mixture within the above range. Furthermore, the temperature of the separated gas inside the separation device 192 is preferably 50°C or higher, for example, from the viewpoint of increasing the volatility of ammonia in the mixture, and more preferably between 50°C and 90°C, from the viewpoint of suppressing the volatilization of water in the mixture. The separated gas may be heated before being supplied to the separation device 192, but it does not need to be heated before supply as long as the temperature inside the separation device 192 is as described above.

[0099] The flow rate of the separated gas supplied to the separation device 192 is preferably 0.5 times or more, preferably 1.0 times or more, and more preferably 2.0 times or more, the amount of nitrogen (stoichiometric) required for the ammonia synthesis reaction in the ammonia production device 600, from the viewpoint of improving the separation efficiency of ammonia and water in relation to the gas temperature and pH of the mixture in the separation device 192. The upper limit of the flow rate of the separated gas supplied to the separation device 192 is approximately 5.0 times the amount (stoichiometric) required for the ammonia synthesis reaction in the ammonia production device 600. Regarding the relationship between the temperature and flow rate of the separated gas, when the flow rate of the separated gas is 0.5 times the amount of nitrogen (stoichiometric) required for the ammonia synthesis reaction in the ammonia production device 600, the temperature of the separated gas is preferably about 80°C; when the flow rate of the separated gas is 1.0 times, the temperature of the separated gas is preferably about 70°C; and when the flow rate of the separated gas is 2.0 times, the temperature of the separated gas is preferably about 50°C.

[0100] In the separation device 192, a gas containing gaseous ammonia and nitrogen (in Figure 8, “N ２ / NH ３ (G)'') is discharged from, for example, near the top of the column of the separation unit 192, and thereafter, if necessary, further ammonia high-purity treatment is performed to recover it as high-purity ammonia. Examples of such treatments include absorption method, cryogenic separation method, membrane separation method, etc. The water separated from the ammonia in the separation unit 192 is discharged from near the bottom of the separation unit 192. The water discharged from the separation unit 192 is either recycled or treated as wastewater.

[0101] The ammonia production apparatus 700 of this embodiment may also include a separation device 193, as shown in Figure 9. In addition to the mixture produced in the cathode chamber 120, gaseous nitrogen and hydrogen are supplied to the separation device 193, and the separation device 193 can separate at least one of ammonia and water from the mixture produced in the cathode chamber 120. Furthermore, the separation device 193 can separate the gas and liquid within the separation device 193. This type of ammonia production apparatus can have a simpler configuration compared to the ammonia production apparatus shown in Figure 8.

[0102] The separation device 193 will be described in detail below. Elements that have already been described will be given the same numbering and their descriptions will be omitted unless otherwise specified.

[0103] The separation device 193 is supplied with at least the mixture and gaseous nitrogen and hydrogen, and is a device for separating gas from liquid, as well as a device for separating at least one of ammonia and water from the mixture generated in the cathode chamber.

[0104] The separation device 193 has the function of separating at least one of ammonia and water from the mixture generated in the cathode chamber, and in this embodiment, a device using the ammonia stripping method as the separation means is used.

[0105] The separation device 193 may be, for example, a tower-shaped device with multiple trays installed inside. However, the separation device 193 is not limited to this configuration. The separation device 193 is supplied with waste from the cathode chamber 120 containing the mixture. This waste contains residual nitrogen gas supplied to the cathode chamber 120 as a raw material. In this embodiment, the nitrogen gas plays the role of a separation gas for separating (stripping) ammonia from the aqueous solution in the mixture. When using residual nitrogen gas supplied to the cathode chamber 120 as a raw material as a separation gas, the amount of nitrogen gas supplied to the cathode chamber 120 of the ammonia production apparatus 700 is preferably 1.5 times or more, preferably 2.0 times or more, and more preferably 3.0 times or more, the amount of nitrogen gas supplied to the cathode chamber 120 of the ammonia production apparatus 700, in relation to the gas temperature in the separation device 193 and the pH of the mixture, in order to improve the separation efficiency of ammonia and water. The upper limit of the flow rate of the separation gas supplied to the separation device 193 is approximately 5.0 times the amount (stoichiometric) required for the ammonia synthesis reaction in the ammonia production device 700. Although not shown in the figures, the separation device 193 may also be supplied with gaseous nitrogen or water vapor as a separation gas, if necessary. As the nitrogen gas added to the separation device 193, for example, nitrogen discharged from the second gas separation means 195 can be used.

[0106] The separation device 193 may be equipped with means to increase the contact time between the mixture in the discharge from the cathode chamber 120 and the separated gas (for example, nitrogen gas in the discharge). Although not shown in the figures, means to increase the contact time between the mixture in the discharge and the separated gas that can be installed in the separation device 193 include a stirring means for the mixture and the separated gas, such as a propeller, or the separation device 193 may be equipped with a supply port for supplying the separated gas separately, as described above, in addition to the supply port for supplying the discharge from the cathode chamber 120. In this case, the separation device 193 may be equipped with supply ports arranged so that the flows of the discharge and the separated gas supplied from two or more supply ports face each other, and the positions of each supply port may be set so that they form a counterflow system, thereby increasing the contact time between the mixture in the discharge and the separated gas and improving the ammonia separation efficiency. Furthermore, when a separate separation gas is supplied, the sum of the gas flow rate supplied to the cathode chamber 120 and the gas flow rate supplied separately to the separation device 193 is preferably 1.5 times or more, preferably 2.0 times or more, and more preferably 3.0 times or more, the amount required for the ammonia synthesis reaction (stoichiometric) in the ammonia production apparatus 700. The upper limit of the flow rate of the separation gas supplied to the separation device 193 is approximately 5.0 times the amount required for the ammonia synthesis reaction (stoichiometric) in the ammonia production apparatus 700.

[0107] Similar to the case of the ammonia production apparatus 600, the pH of the mixture (liquid containing the mixture) supplied to the separation apparatus 193 in the ammonia production apparatus 700 is preferably 8.0 or higher, more preferably 10.5 or higher, and even more preferably 11.0 or higher. Also, similar to the case of the ammonia production apparatus 700, the temperature of the mixture (liquid containing the mixture) is preferably 50°C or higher, and even more preferably 50°C or higher and 90°C or lower, from the viewpoint of pH and the boiling point of water.

[0108] The temperature inside the separation device 193 is preferably 50°C or higher, and more preferably between 50°C and 90°C, from the viewpoint of maintaining the temperature of the mixture within the above-mentioned range. Furthermore, the temperature of the separated gas inside the separation device 193 is preferably 50°C or higher, for example, from the viewpoint of increasing the volatility of ammonia in the mixture, and more preferably between 50°C and 90°C, from the viewpoint of suppressing the volatilization of water in the mixture. The separated gas may be heated before being supplied to the separation device 193, but it is not necessary to heat it before supply as long as it is at the above-mentioned temperature when discharged from the cathode chamber 120 and the temperature inside the separation device 193 can be kept within the above-mentioned range.

[0109] In the separation device 193, a gas containing ammonia, nitrogen, and hydrogen (in Figure 9, “N ２ / H ２ / NH ３ (G)'') is discharged from, for example, near the top of the separation device 193 and supplied to the first gas separation means 194. The water separated from ammonia in the separation device 193 is discharged from near the bottom of the separation device 193. The water discharged from the separation device 193 is recycled or treated as wastewater. Note that the water discharged from the separation device 193 may contain dissolved liquid ammonia that could not be removed by ammonia stripping. For this reason, the water discharged from the separation device 193 and liquid ammonia (in Figure 9, "H") may be dissolved. ２ O / NH ３ (L)) can be subjected to further ammonia separation treatment (e.g., ammonia stripping treatment) as needed to recover ammonia.

[0110] Furthermore, each of the optional components described above (for example, ammonia separation means, nitrogen separation means, anode chamber temperature adjustment means, water separation means, means for reusing gaseous nitrogen contained in the exhaust gas obtained from the ammonia separation means, water-repellent component in the cathode electrode, and water-absorbing component in the cathode electrode) can be incorporated into the ammonia production apparatus of this embodiment either individually or in any combination of two or more. For example, although not shown, the ammonia production apparatus of this embodiment may include both ammonia separation means and water separation means.

[0111] The ammonia production method of this embodiment includes an ammonia production step in which nitrogen is supplied to the cathode chamber 120 of the ammonia production apparatus of this embodiment, and water is supplied to the anode chamber 110 of the ammonia production apparatus, and ammonia is produced from nitrogen by electrolytic synthesis. The ammonia production method of this embodiment may also include a recovery step in which the ammonia produced in the ammonia production step is separated and recovered.

[0112] In the ammonia production process, water is electrolyzed in the anode chamber 110, supplying hydrogen ions to the cathode chamber 120. Furthermore, ammonia is synthesized from the nitrogen and hydrogen ions supplied to the cathode chamber 120 by the ammonia synthesis catalyst 1222 located on the cathode electrode 122 of the cathode chamber 120.

[0113] In the ammonia recovery process, the ammonia separation means 170 described above may be used. This allows ammonia to be separated and recovered from the gas discharged from the cathode chamber 120.

[0114] 100, 200, 300, 400, 500, 600, 700... Ammonia production apparatus, 110... Anode chamber, 112... Anode electrode, 120... Cathode chamber, 122, 122'... Cathode electrode, 1221... Gas diffusion layer, 1222... Ammonia synthesis catalyst, 1223... Carrier, 1224... Binder, 1225... Water-absorbing component, 1226... Water-repellent component, 130... Diaphragm, 140... Anode chamber temperature adjustment means, 140 a...Water temperature adjustment means, 140b...Anode chamber temperature adjustment means, 150...Cathode electrode drying means, 150a...Nitrogen flow rate adjustment means, 150b...Cathode chamber temperature adjustment means, 150c...Nitrogen gas temperature adjustment means, 160...Nitrogen separation means, 170...Ammonia separation means, 180...Water separation means, 191...Gas-liquid separation device, 192, 193...Separation device, 194...First gas separation means, 195...Second gas separation means.

Claims

1. An ammonia production apparatus comprising: an anode chamber having an anode electrode with a water electrolytic catalyst and to which water is supplied; a cathode chamber having a cathode electrode with an ammonia synthesis catalyst and to which gaseous nitrogen is supplied; a diaphragm provided between the anode chamber and the cathode chamber; and a cathode electrode drying means for drying the cathode electrode, wherein ammonia is synthesized in the cathode chamber from a hydrogen source and nitrogen in the presence of the ammonia synthesis catalyst.

2. The ammonia production apparatus according to claim 1, wherein the cathode electrode drying means comprises at least one selected from the group consisting of a nitrogen flow rate adjusting means for increasing the flow rate of gaseous nitrogen supplied to the cathode chamber, a cathode chamber temperature adjusting means for raising the temperature inside the cathode chamber, and a nitrogen gas temperature adjusting means for raising the temperature of gaseous nitrogen before it is supplied to the cathode chamber.

3. The ammonia production apparatus according to claim 1 or 2, further comprising an anode chamber temperature adjustment means for adjusting the temperature of the anode chamber.

4. The ammonia production apparatus according to claim 3, wherein the anode chamber temperature adjustment means comprises at least one selected from the group consisting of a water temperature adjustment means for adjusting the temperature of water before it is supplied into the anode chamber and an anode chamber temperature adjustment means for raising the temperature inside the anode chamber.

5. An ammonia production apparatus according to any one of claims 1 to 4, comprising a cathode chamber cooling means for lowering the temperature inside the cathode chamber.

6. The ammonia production apparatus according to any one of claims 1 to 5, wherein the diaphragm is an ion exchange membrane or a porous membrane.

7. The ammonia production apparatus according to any one of claims 1 to 6, wherein the ammonia synthesis catalyst comprises a molybdenum complex.

8. The ammonia production apparatus according to any one of claims 1 to 7, wherein the cathode electrode includes a carrier on which the ammonia synthesis catalyst is supported.

9. The ammonia production apparatus according to claim 8, wherein the carrier comprises at least one porous carbon particle selected from the group consisting of channel black, furnace black, thermal black, acetylene black, activated carbon, natural graphite, artificial graphite, graphitized carbon, graphene, carbon nanotubes, fullerene, Ketjenblack, and glassy carbon.

10. The ammonia production apparatus according to claim 8 or 9, wherein the cathode electrode includes a binder for binding the carrier.

11. The ammonia production apparatus according to claim 10, wherein the binder comprises an ionomer.

12. The ammonia production apparatus according to any one of claims 1 to 11, wherein the cathode electrode includes at least one gas diffusion layer selected from the group consisting of carbon paper, carbon cloth, or carbon felt.

13. An ammonia production apparatus according to any one of claims 1 to 12, comprising an ammonia separation means for separating the synthesized ammonia from the gas discharged from the cathode chamber.

14. An ammonia production apparatus according to any one of claims 1 to 13, comprising a nitrogen separation means for separating nitrogen from air, wherein the gaseous nitrogen is obtained from the nitrogen separation means.

15. A method for producing ammonia, comprising an ammonia production step of supplying nitrogen to the cathode chamber of an ammonia production apparatus according to any one of claims 1 to 14, and supplying water to the anode chamber of the ammonia production apparatus, and producing ammonia from nitrogen by electrolytic synthesis.

16. The method for producing ammonia according to claim 15, further comprising a recovery step of separating and recovering the ammonia produced in the ammonia production step.

17. The ammonia production apparatus according to any one of claims 1 to 14, wherein the cathode electrode contains a water-absorbing component.

18. The ammonia production apparatus according to claim 17, wherein the water-absorbing component comprises one or more selected from the group consisting of water-absorbing polymers, inorganic desiccants, biodegradable water-absorbing polymers, and water-absorbing metal-organic frameworks.

19. The ammonia production apparatus according to claim 17 or 18, wherein the water-absorbing component is at least one selected from the group consisting of sodium polyacrylate, potassium polyacrylate, polyvinyl alcohol, calcium oxide, and calcium chloride.

20. The ammonia production apparatus according to any one of claims 1 to 14 and 17 to 19, wherein the cathode electrode contains a water-repellent component.

21. The ammonia production apparatus according to claim 20, wherein the water-repellent component comprises one or more selected from the group consisting of organic polymer-based water-repellent materials and inorganic water-repellent materials.

22. The ammonia production apparatus according to claim 20 or 21, wherein the water-repellent component comprises a water-repellent metal-organic framework.

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