Ammonia production device

Abstract

Provided is an ammonia production device comprising: an electrolysis device including 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, and a diaphragm provided between the anode chamber and the cathode chamber, wherein a mixture containing at least ammonia and water is generated in the cathode chamber; and a separation device that separates at least one among the ammonia and the water from the mixture generated 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] In response to such demands, technology is being developed to produce ammonia from gaseous nitrogen at room temperature and atmospheric pressure. As an 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 ammonia from gaseous nitrogen, an electrolytic apparatus equipped with a cathode, an anode, and a diaphragm separating the cathode and anode is generally used. The cathode of such an electrolytic apparatus is equipped with a catalyst for ammonia synthesis. For example, when a cation exchange membrane is used as the diaphragm, in the presence of the catalyst, gaseous nitrogen (N2) supplied to the cathode and protons (H2) supplied from the anode to the cathode via the diaphragm are used for ammonia synthesis. + ) and are used as raw materials, N2 + 6H + +6e - →It is believed that ammonia is synthesized through the reaction of 2NH3.

[0007] On the other hand, when obtaining 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 the raw material for supplying hydrogen. For example, in the above-mentioned manufacturing apparatus, an electrolyte containing water is often used as the hydrogen supply source on the anode side. Here, the cathode and anode are separated by a diaphragm, but the water in the anode may move to the cathode through the diaphragm. Also, protons (H) generated at the anode + ) is accompanied by water molecules and forms a hydronium ion (H3O + Ammonia can pass through the membrane to the cathode in forms such as Zundel-type or Eigen-type (where two or more water molecules are attached to one proton). For these reasons, water is produced simultaneously with ammonia on the cathode side during ammonia production. Since the produced ammonia is readily soluble in water, gaseous ammonia can be obtained by removing the liquid water and suppressing the dissolution of ammonia in water.

[0008] However, although the amount of water that moves to the cathode side across the diaphragm is thought to be small, more water than expected is sometimes found in the cathode chamber and in equipment located downstream of the ammonia electrolysis unit. Since ammonia dissolves easily in water, when water and ammonia are produced simultaneously in the cathode, the ammonia dissolves in the water and forms a mixture. Therefore, in order to recover the ammonia in the end, there is a need to develop a technology that can separate water and ammonia from the mixture discharged from the cathode chamber of the electrolysis unit.

[0009] The present invention aims to provide an ammonia production apparatus capable of separating water and ammonia from a mixture generated in the cathode chamber of an electrolytic device, in order to solve the above-mentioned problems.

[0010] The inventors of the present invention have conducted intensive studies to solve the above problems. As a result, they have found that in an electrolysis apparatus using water as a hydrogen supply source, water is generated at the cathode due to various causes in addition to water that moves to the cathode side through a diaphragm. More specifically, in addition to the mode where water is generated at the cathode by diffusion of water from the anode side to the cathode side through the diaphragm along with a concentration gradient, protons generated at the anode move to the cathode side together with water molecules, and then H in the protons accompanied by water molecules participates in the ammonia synthesis reaction + and is consumed, whereby a mode where H2O is generated on the cathode side has also been found. The inventors of the present invention have completed the present invention based on the above findings.

[0011] In other words, the present invention includes the following embodiments: <1> An ammonia production apparatus comprising: an electrolytic device 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; and a diaphragm provided between the anode chamber and the cathode chamber, wherein in the cathode chamber, a mixture comprising at least ammonia and water is produced; and a separation device for separating at least one of the ammonia and water from the mixture produced in the cathode chamber. <2> The ammonia production apparatus according to <1>, wherein the pH of the mixture is 8.0 or higher. <3> The ammonia production apparatus according to <1> or <2>, wherein at least the mixture and a separation gas are supplied to the separation device, and the ammonia in the mixture is separated as gaseous ammonia. <4> The ammonia production apparatus according to <3>, wherein the separation gas comprises residual gas of the gaseous nitrogen supplied to the cathode chamber. <5> The ammonia production apparatus according to <3> or <4>, wherein the temperature of the separated gas is 50 to 90°C. <6> The ammonia production apparatus according to any one of <1> to <5>, further comprising a gas-liquid separation device that supplies at least the mixture and gaseous nitrogen and hydrogen, and separates the gas from a liquid containing at least the mixture. <7> The ammonia production apparatus according to any one of <1> to <6>, wherein the amount of gaseous nitrogen supplied to the cathode chamber is 1.5 times or more the amount required for the ammonia synthesis reaction in the electrolytic device. <8> The ammonia production apparatus according to any one of <1> to <7>, wherein the diaphragm is an ion exchange membrane or a porous membrane. <9> The ammonia production apparatus according to any one of <1> to <8>, wherein the ammonia synthesis catalyst contains a molybdenum complex. <10> The ammonia production apparatus according to any one of <1> to <9>, wherein the cathode electrode contains a carrier supporting the ammonia synthesis catalyst.<11> The ammonia production apparatus according to <10>, 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. <12> The ammonia production apparatus according to <10> or <11>, wherein the cathode electrode comprises a binder for binding the carrier. <13> The ammonia production apparatus according to <12>, wherein the binder comprises an ionomer. <14> The ammonia production apparatus according to any one of <1> to <13>, wherein the cathode electrode comprises at least one gas diffusion layer selected from the group consisting of carbon paper, carbon cloth, and carbon felt. <15> The ammonia production apparatus according to any one of <1> to <14>, comprising a nitrogen separation means for separating nitrogen from a nitrogen-containing mixed gas to obtain gaseous nitrogen. <16> A method for producing ammonia, comprising an ammonia production step of supplying nitrogen to the cathode chamber of an ammonia production apparatus described in any one of <1> to <15>, and supplying water to the anode chamber of the ammonia production apparatus, and producing ammonia from nitrogen by electrolytic synthesis. <17> A method for producing ammonia according to <16>, comprising a recovery step of separating and recovering the ammonia produced in the ammonia production step.

[0012] According to the present invention, an ammonia production apparatus capable of separating water and ammonia from a mixture generated in the cathode chamber of an electrolytic device can be provided.

[0013] It is a diagram schematically showing an example of the ammonia production apparatus of the present embodiment. It is an enlarged view schematically showing an example of the vicinity of the cathode electrode of the present embodiment. It is a diagram schematically showing another example of the ammonia production apparatus of the present embodiment. It is an enlarged view schematically showing another example of the vicinity of the cathode electrode of the present embodiment. It is a diagram schematically showing still another example of the ammonia production apparatus of the present embodiment. It is a diagram schematically showing yet another example of the ammonia production apparatus of the present embodiment. It is a diagram schematically showing still further another example of the ammonia production apparatus of the present embodiment. It is a diagram schematically showing still yet another example of the ammonia production apparatus of the present embodiment. It is an enlarged view schematically showing still another example of the vicinity of the cathode electrode of the present embodiment.

[0014] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention. In the drawings, the same reference numerals are assigned to the same elements, and duplicate descriptions are omitted. In addition, unless otherwise specified, positional relationships such as up, down, left and right are based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[0015] The ammonia production apparatus of the present embodiment (hereinafter, also simply referred to as "ammonia production apparatus") comprises: an anode chamber having an anode electrode including a water electrolysis catalyst and supplied with water; a cathode chamber having a cathode electrode including an ammonia synthesis catalyst and supplied with gaseous nitrogen (hereinafter, also referred to as "nitrogen gas"); and a diaphragm provided between the anode chamber and the cathode chamber. The ammonia production apparatus comprises: an electrolytic device that produces a mixture containing at least ammonia and water in the cathode chamber; and a separation device that separates at least one of the ammonia and the water from the mixture produced in the cathode chamber.

[0016] In the ammonia production apparatus using gaseous nitrogen as described above, in addition to water that moves from the anode chamber of the electrolytic device to the cathode chamber through the diaphragm along with a concentration gradient, protons move to the cathode side together with water molecules, and then H3O participates in the ammonia synthesis reaction + in H +Water may be generated due to other causes, such as the consumption of other substances. Since ammonia dissolves readily in water, a mixture containing these substances is generated in the cathode chamber. However, according to the ammonia production apparatus of this embodiment, the separation device can separate water and ammonia from the mixture generated in the cathode chamber of the electrolytic device. This makes it possible to efficiently obtain, for example, highly purified ammonia.

[0017] The ammonia production apparatus of this embodiment will be described with reference to the figures. 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 10 includes an electrolytic device 100, a separation device 300, a gas-liquid separation device 200, a first gas separation means 410, and a second gas separation means 420.

[0018] [Electrolytic Apparatus] The electrolytic apparatus 100 comprises an anode chamber 110, a cathode chamber 120, and a diaphragm 130. 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 configurations of the ammonia production apparatus 10 will be described in detail below.

[0019] (Anode Chamber) The anode chamber 110 includes an anode electrode 112. The anode electrode 112 may be disposed so as to cover the entire surface of a diaphragm 130, which will be described later, on the anode chamber 110 side. The anode electrode 112 includes a water electrolysis catalyst, which is a substance that functions as a catalyst in the water electrolysis reaction. Although the anode electrode 112 is not particularly limited, for example, it may include a mesh-shaped carrier and a water electrolysis catalyst supported on the carrier. The mesh-shaped carrier is not particularly limited as long as it has conductivity, and examples thereof include a conductive mesh woven from conductive fibers including fibers and a conductive coating covering the fibers. The conductive fibers are not particularly limited, and examples thereof include fibers containing a resin, and a metal coating or carbon coating disposed so as to cover the surface of the fibers. Examples of the water electrolysis catalyst 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 coating may include a water electrolysis catalyst.

[0020] The anode chamber 110 has a space into which water as an electrolytic solution is supplied. Here, the water supplied to the anode chamber 110 may be pure water, or may contain an electrolyte or the like as necessary. 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. Examples thereof include alkaline electrolytes such as potassium hydroxide and sodium hydroxide, and acidic electrolytes such as neutral electrolytes including sulfuric acid, potassium sulfate, and sodium sulfate. At the anode electrode 112, water is oxidized according to the following formula (1): 2H₂O→O₂+4H + +4e - ...(1) The electrons generated here are supplied to the cathode chamber 120 via an external circuit. In addition, protons (H + ) are supplied to the cathode chamber 120 via the diaphragm 130. Protons generated by water oxidation hydrate to form hydronium (H₃O+ ) 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.

[0021] 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.

[0022] (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. 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 hydrocarbon-based 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 alone, 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.

[0023] In addition to those mentioned above, other examples of the diaphragm 130 include silicone resin; fluorine-based resins such as perfluoroalkoxyalkane (PFA), perfluoroethylenepropene 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 materials such as zeolites, oxides, and filter paper.

[0024] (Cathode Chamber) The cathode chamber 120 is equipped with a cathode electrode 122. The cathode chamber 120 has a space into which gaseous nitrogen is supplied. When the diaphragm 130 is a cation exchange membrane, a forward reaction to synthesize ammonia from a hydrogen source and nitrogen and a side reaction to produce H2 occur at the cathode electrode 122 according to the following formulas (2) and (3). 2H + +2e - →H2…(2) N2+6H + +6e - →2NH3 …(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 diaphragm 130. Since the cathode electrode 122 has an ammonia synthesis catalyst, which will be described later, the reaction of formula (3) proceeds more favorably than the reaction of formula (2). 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 diaphragm 130. The hydrogen source is obtained, for example, by the electrolysis reaction of water in the anode chamber 110. When the diaphragm 130 is an anion exchange membrane, the reaction at the cathode electrode 122 is N2 + 6H2O + 6e - →2NH3+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, a reaction to synthesize ammonia similar to that in both the cation exchange membrane and anion exchange membrane cases may occur.

[0025] 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. Figure 2 is a schematic enlarged view showing an example of the vicinity of the cathode electrode in this embodiment. As shown in Figure 2, the cathode electrode 122 may include a gas diffusion layer 1221, an ammonia synthesis catalyst 1222, a carrier 1223, and a binder 1224.

[0026] The ammonia synthesis catalyst 1222, the carrier 1223, and the binder 1224 may be uniformly mixed by known methods. The mixture, in which the ammonia synthesis catalyst 1222, the carrier 1223, and the binder 1224 are uniformly mixed, may be placed on the side of the gas diffusion layer 1221 facing the diaphragm 130 (for example, between the gas diffusion layer 1221 and the diaphragm 130).

[0027] <Mixture> In this embodiment, the "mixture" includes at least ammonia and water and is formed in the cathode chamber 120. First, as shown in Figure 1, the diaphragm 130 described above is impermeable to almost nothing other than ions, but it can permeate substances other than ions. 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, the water will move from the anode chamber 110 to the cathode chamber 120 through the diaphragm 130, driven by this concentration difference.

[0028] Furthermore, if the diaphragm 130 is a cation exchange membrane, the protons generated at the anode electrode 112 may hydrate and become accompanied by water molecules, such as hydronium, and then move from the anode chamber 110 to the cathode chamber 120 via the diaphragm 130. When nitrogen and hydronium react to produce ammonia, water is also produced simultaneously. As a result, liquid water is formed in the cathode chamber 120. Specifically, taking the case where hydronium moves to the cathode chamber 120 as an example, it is thought that in addition to the above-mentioned equation (3), a reaction to synthesize ammonia occurs in the cathode chamber 120 according to the following equation (4): 1 / 2N2 + 3H3O + +3e -→NH3 + 3H2O …(4) According to the stoichiometric equation (4), it is assumed that 3 moles of water are produced from 1 / 2 mole of gaseous nitrogen.

[0029] When ammonia and water are simultaneously produced in the cathode chamber 120, at least a portion of the ammonia dissolves in the water in the cathode chamber 120. Therefore, the mixture in this embodiment can be described as a liquid containing water produced in the cathode chamber 120 by various causes and ammonia dissolved in that water. Furthermore, ammonia in water takes on both dissociative and non-dissociative forms depending on the pH, and this reaction is represented by the following formula (5): NH3 + H2O ⇔ NH4 + +OH - …(5) Here, non-dissociative ammonia (NH3) is highly volatile and easily transitions to the gas phase, while dissociative ammonium ions (NH4) + Ammonia is non-volatile and does not easily transition to the gas phase. Hereinafter, gaseous ammonia may be referred to as "NH3(G)" and liquid ammonia as "NH3(L)". The concept of liquid ammonia (NH3(L)) also includes ammonia dissolved in water in a mixture (both non-dissociative and dissociative).

[0030] From the cathode chamber 120, along with the mixture of this embodiment, gases containing gaseous nitrogen, gaseous hydrogen, and gaseous ammonia generated in the cathode are discharged, depending on the composition within the cathode chamber 120.

[0031] <Gas Diffusion Layer> The gas diffusion layer 1221 shown in Figure 2 has a plurality of pores and is provided on the side of the cathode electrode 122 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 at least one selected from the group consisting of 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.

[0032] <Ammonia Synthesis Catalyst> 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.

[0033] 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.

[0034] The aforementioned metal complex is not particularly limited, but examples include metal complexes that combine the above-mentioned central metal and the above-mentioned ligand. As the aforementioned 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.

[0035] 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).

[0036]

[0037] In the above formulas (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).

[0038]

[0039] 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.

[0040] In the formula, Y represents the counterion. The counterion Y is not particularly limited, but for example, the triflate ion (OTf － ), PF6 － BF ４ － , tetrakis(3,5-bis(trifluoromethyl)phenyl)borate ion (BarF ４ － ), bis(trifluoromethanesulfonyl)imide ion (NTf ２ － ), N (SO ２ F) ２ －It represents chloride ions, bromide ions, or iodide ions.

[0041] Furthermore, it is preferable that the molybdenum complex contains one or more compounds represented by the following formulas (4-1) to (4-3).

[0042]

[0043] In the formula, tBu represents a tert-butyl group.

[0044] <Carrier> 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 at least one 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. The carrier 1223 may be used alone or in combination of two or more types.

[0045] <Binder> The binder 1224 binds the ammonia synthesis catalyst 1222 and the support 1223 within the cathode electrode 122. This prevents the ammonia synthesis catalyst 1222 and the support 1223 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. The binder may also contain an ionomer as a polymer material. The ionomer is not particularly limited, but examples include proton-conducting ionomers. 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.

[0046] 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.

[0047] [Gas-Liquid Separator] As shown in Figure 1, the ammonia production apparatus 10 may also include a gas-liquid separator 200. The gas-liquid separator 200 is a device that receives at least the mixture and gaseous nitrogen and hydrogen, and separates the gas from a liquid containing at least the mixture. Specifically, the waste discharged from the cathode chamber 120 contains the mixture and gas in this embodiment (in Figure 1, “N2 / H2 / NH3(G) / H2O / NH3(L)”), and this waste is supplied to the gas-liquid separator 200. Here, “liquid containing at least the mixture” contains at least the mixture in this embodiment, and may also contain other liquids discharged from the cathode chamber 120. The waste supplied to the gas-liquid separator 200 is separated by a gas-liquid separation means (not shown) into a liquid containing the mixture in this embodiment and gaseous nitrogen, hydrogen, and gaseous ammonia. Performing gas-liquid separation before separating water and ammonia from the mixture using the separation device 300 can, for example, increase the stripping efficiency described later and improve the accuracy of the process.

[0048] The gas-liquid separation means in the gas-liquid separation apparatus 200 is not particularly limited, and known gas-liquid separation means can be used. Examples of gas-liquid separation means include gravity separators, centrifugal separators, 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 300, gravity separation, knockout drums, flash tanks, etc. can be suitably used as the gas-liquid separation means of the gas-liquid separation apparatus 200.

[0049] In the gas-liquid separator 200, the gas (in Figure 1, “N2 / H2 / NH3(G)”) separated from the liquid containing the mixture is discharged from, for example, near the top of the gas-liquid separator 200 and supplied to the first gas separation means 410. Also, for example, the liquid containing the mixture (in Figure 1, “H2O / NH3(L)”) is discharged from near the bottom of the gas-liquid separator 200. The liquid containing the mixture discharged from the gas-liquid separator 200 is supplied to the separation device 300.

[0050] [First and Second Gas Separation Means] The first gas separation means 410 is supplied with gas discharged from the gas-liquid separation device 200. The gas contains nitrogen, hydrogen, and gaseous ammonia. The first gas separation means 410 is a device that separates nitrogen and hydrogen from gaseous ammonia from the supplied gas. The separation means in the first gas separation means 410 is not particularly limited, and known means capable of separating nitrogen and hydrogen from gaseous ammonia can be used, for example, a cryogenic separation method can be used. However, the separation means 410 of the first gas separation means is not limited to this embodiment.

[0051] The gas separated from ammonia in the first gas separation means 410 (in Figure 1, “N2 / H2”) is discharged from the first gas separation means 410 and supplied to the second gas separation means 420. The ammonia separated in the first gas separation means 410 is liquid ammonia, gaseous ammonia, or a mixture thereof (in Figure 1, “NH3(G / L)”), and is discharged outside the first gas separation means 410. The ammonia discharged from the first gas separation means 410 is then recovered as high-purity ammonia by further ammonia purification treatment as needed.

[0052] The second gas separation means 420 is supplied with the gas discharged from the first gas separation means 410. This gas contains nitrogen and hydrogen. The second gas separation means 420 is a device that separates nitrogen and hydrogen from the supplied gas. The separation means in the second gas separation means 420 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 420 is not limited to this embodiment.

[0053] The nitrogen and hydrogen gases separated in the second gas separation means 420 are discharged separately. The nitrogen gas discharged from the second gas separation means 420 can be reused as a cathode raw material or separated gas for the electrolytic device 100. The hydrogen gas discharged from the second gas separation means 420 can be reused within the device or used in another process described later. In particular, if the Faraday efficiency in the system is low, the amount of hydrogen may reach a considerable amount. In this case, it can be effectively utilized for other processes, for example (green ammonia production (water electrolysis and Haber-Bosch process, etc.), synthetic fuel production (e-methanol, e-fuel, e-methane, e-propane, etc.)). Another example of reusing the hydrogen gas discharged from the second gas separation means 420 is to supply hydrogen gas to the electrolyte on the anode side. When hydrogen gas is supplied to the anode side, H2 → 2H + +2e - The reaction occurs, and the resulting proton moves to the cathode side, where it can be used in the ammonia production reaction.

[0054] [Separation device] The ammonia production apparatus 10 includes a separation device 300. The separation device 300 is a device that separates at least one of ammonia and water from the mixture produced in the cathode chamber. 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, a separation device 300 using the ammonia stripping method as a separation method may be a device that is supplied with at least the mixture and the separation gas, and separates the ammonia in the mixture as gaseous ammonia. The following description will use an embodiment in which the ammonia stripping method is used as the separation device 300 as an example.

[0055] <Ammonia Stripping> The ammonia stripping method 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 separated or removed by contacting it with a separation gas under appropriate conditions, thereby moving the ammonia from the aqueous solution into the separation gas (gas phase).

[0056] The separation device 300 may be, for example, a tower-shaped device with multiple trays installed inside. However, the separation device 300 is not limited to this configuration. The separation device 300 is supplied with a mixture and a separation gas. Although not particularly limited, the mixture can be supplied from near the top of the tower of the separation device 300, and the separation gas can be supplied from near the bottom of the separation device 300. In this case, the mixture (liquid) flows down from the top to the bottom of the separation device 300, while the separation gas flows backward from the bottom to the top of the separation device 300, 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.

[0057] (pH of the mixture) As described above, ammonia dissolved in water takes on dissociative and non-dissociative forms depending on the pH. Non-dissociative ammonia (NH3) is highly volatile and easily moves into the gas phase, while dissociative ammonium ions (NH4) + Since ammonia is non-volatile, it has the property of not easily migrating into the gas phase. The ratio of non-dissociated ammonia to dissociated ammonium ions in the mixture (i.e., the volatility of ammonia in water) mainly depends on the temperature and pH of the mixture in this embodiment. For example, the higher the pH of the mixture, the more dominant non-dissociated ammonia (NH3) becomes, making it easier for ammonia to migrate into the gas phase, and allowing stripping to proceed more effectively. On the other hand, at low pH, ammonia is dominated by ammonium ions (NH4). + It takes the form of ), which is non-volatile and therefore does not easily transfer to the gas phase. From this viewpoint, the pH of the mixture (liquid containing the mixture) supplied to the separation device 300 is preferably 8.0 or higher, preferably 10.5 or higher, and more preferably 11.0 or higher.

[0058] (Temperature of the mixture) The pH of the mixture can be adjusted by known pH adjustment methods, such as adjusting the ammonia concentration in the mixture or introducing acidic substances. However, from the viewpoint 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 viewpoint of the ease with which non-dissociated ammonia is formed and ammonia is easily volatilized. Furthermore, from the viewpoint of suppressing the consumption of a lot of energy for heating and suppressing the volatilization of water and its movement into the gas phase, a temperature of 50°C to 90°C is even more preferable.

[0059] (Separation Gas) A separation gas is supplied to the separation device 300. By bringing the separation gas into contact with the mixture within the separation device 300, 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 when passed through the cathode side, it is expected to be heated in the electrolytic cell. 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 1 shows an example in which nitrogen is supplied to the separation device 300 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 10 may also be reused. For example, since it is expected that the nitrogen gas used as a raw material may flow in amounts exceeding the stoichiometric limit (e.g., 1.5 times the normal amount), the separation gas can also be a gas containing residual nitrogen gas supplied to the cathode chamber 120. This "residual gas" can include nitrogen gas immediately after discharge from the cathode chamber 120 or nitrogen gas discharged from the second gas separation means 420 shown in Figure 1.

[0060] 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-mentioned range. Furthermore, the temperature of the separated gas inside the separation device 300 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 300, but it does not need to be heated before supply as long as the temperature inside the separation device 300 is as described above.

[0061] The flow rate of the separation gas supplied to the separation device 300 is preferably 0.5 times or more, preferably 1 time or more, and more preferably 2 times or more, the amount of nitrogen (stoichiometric) required for the ammonia synthesis reaction in the electrolytic device 100, 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 300. The upper limit of the flow rate of the separation gas supplied to the separation device 300 is about 5 times the amount (stoichiometric) required for the ammonia synthesis reaction in the electrolytic device 100. Regarding the relationship between the temperature and flow rate of the separation gas, when the flow rate of the separation gas is 0.5 times the amount of nitrogen (stoichiometric) required for the ammonia synthesis reaction in the electrolytic device 100, the temperature of the separation gas is preferably about 80°C, when the flow rate of the separation gas is 1 time, the temperature of the separation gas is preferably about 70°C, and when the flow rate of the separation gas is 2 times, the temperature of the separation gas is preferably about 50°C.

[0062] In the separation unit 300, a gas containing gaseous ammonia and nitrogen (in Figure 1, “N2 / NH3(G)”) is discharged from, for example, near the top of the column of the separation unit 300. Afterward, if necessary, further ammonia purification treatment is performed to recover high-purity ammonia. Examples of such treatments include absorption, cryogenic separation, and membrane separation. The water separated from the ammonia in the separation unit 300 is discharged from near the bottom of the separation unit 300. The water discharged from the separation unit 300 is either recycled or treated as wastewater.

[0063] In this embodiment, the ammonia production apparatus is supplied with nitrogen and hydrogen gases discharged from the electrolytic device in addition to the mixture generated in the cathode chamber to the separation device, and the separation device can separate at least one of the ammonia and water from the mixture generated in the cathode chamber, and further separate the gas and liquid within the separation device. This type of ammonia production apparatus can have a simpler configuration compared to the ammonia production apparatus shown in Figure 1.

[0064] Figure 3 is a schematic diagram showing another example of the ammonia production apparatus of this embodiment. As shown in Figure 3, the ammonia production apparatus 20 performs separation of ammonia and water from the mixture and gas-liquid separation in the separation apparatus 320, instead of the gas-liquid separation apparatus 200 and separation apparatus 300 in Figure 1. The ammonia production apparatus 20 will be described below, focusing on the separation apparatus 320. In addition, elements that have already been described will be given the same numbering and their descriptions will be omitted unless otherwise specified.

[0065] [Separation device] As shown in Figure 3, the ammonia production apparatus 20 includes a separation device 320 instead of the gas-liquid separation device 200 and separation device 300 in Figure 1. The separation device 320 is a device that receives at least the mixture and gaseous nitrogen and hydrogen and separates the gas from the liquid, and also separates at least one of ammonia and water from the mixture produced in the cathode chamber.

[0066] The separation device 320 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.

[0067] The separation device 320 may be, for example, a tower-shaped device with multiple trays installed inside. However, the separation device 320 is not limited to this configuration. The separation device 320 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 in this embodiment, the amount of nitrogen gas supplied to the cathode chamber 120 of the electrolytic device 100 is preferably 1.5 times or more, preferably 2 times or more, and more preferably 3 times or more, the amount of nitrogen gas supplied to the cathode chamber 120 of the electrolytic device 100, from the viewpoint of improving the separation efficiency of ammonia and water in relation to the gas temperature in the separation device 320 and the pH of the mixture. The upper limit of the flow rate of the separation gas supplied to the separation device 320 is approximately five times the amount (stoichiometric) required for the ammonia synthesis reaction in the electrolytic device 100. Although not shown in the figures, the separation device 320 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 320, for example, nitrogen discharged from the second gas separation means 420 can be used.

[0068] The separation device 320 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 320 include a means to agitate the mixture and the separated gas, such as a propeller, or the separation device 320 may be equipped with a supply port to supply the separated gas separately, as described above, in addition to the supply port to which the discharge from the cathode chamber 120 is supplied. In this case, the separation device 320 may be equipped with supply ports such that the flows of the discharge and the separated gas supplied from two or more supply ports face each other, and the position 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 320 is preferably 1.5 times or more, preferably 2 times or more, and more preferably 3 times or more, the amount required for the ammonia synthesis reaction (stoichiometric) in the electrolytic device 100. The upper limit of the flow rate of the separation gas supplied to the separation device 320 is approximately 5 times the amount required for the ammonia synthesis reaction (stoichiometric) in the electrolytic device 100.

[0069] Similar to the case of the ammonia production apparatus 10, the pH of the mixture (liquid containing the mixture) supplied to the separation apparatus 320 in the ammonia production apparatus 20 is preferably 8.0 or higher, preferably 10.5 or higher, and more preferably 11 or higher. Also, similar to the first embodiment, the temperature of the mixture (liquid containing the mixture) is preferably 50°C or higher, and more preferably 50 to 90°C, from the viewpoint of pH and the boiling point of water.

[0070] The temperature inside the separation device 320 is preferably 50°C or higher, and more preferably 50 to 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 320 is preferably 50°C or higher, for example, from the viewpoint of increasing the volatility of ammonia in the mixture, and more preferably 50 to 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 320, but it does not need to be heated 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 320 is within the above-mentioned range.

[0071] In the separation unit 320, gaseous ammonia, nitrogen-containing gas, and hydrogen gas (in Figure 3, “N2 / H2 / NH3(G)”) are discharged from, for example, near the top of the tower of the separation unit 320 and supplied to the first gas separation means 410, where further ammonia purification treatment is performed as needed to recover high-purity ammonia. In addition, the water separated from the ammonia in the separation unit 320 is discharged from near the bottom of the separation unit 320. The water discharged from the separation unit 320 is either recycled or treated as wastewater. Note that the water discharged from the separation unit 320 may contain dissolved liquid ammonia that could not be removed by ammonia stripping. Therefore, the water and liquid ammonia (in Figure 3, “H2O / NH3(L)”) discharged from the separation unit 320 can be subjected to further ammonia separation treatment (for example, ammonia stripping treatment) as needed to recover the ammonia.

[0072] The ammonia production apparatus of this embodiment can be configured such that the cathode electrode further has a water-absorbing component. If the cathode electrode of the ammonia production apparatus has a water-absorbing component, it can immediately absorb the water in the liquid produced in the cathode chamber.

[0073] Figure 4 is a schematic diagram showing another example of the vicinity of the cathode electrode in this embodiment. As shown in Figure 4, the ammonia production apparatus of this embodiment may have a water-absorbing component 1225 on the cathode electrode 122A that can absorb water in the cathode chamber 120. Elements that are the same as those already described will be given the same numbering and their descriptions will be omitted unless otherwise specified.

[0074] As described above, the diaphragm provided in the electrolytic device is almost impermeable to anything other than ions, but water may attempt to move from the anode chamber to the cathode chamber through the diaphragm. Also, protons generated at the anode electrode are hydrated to form hydronium, and this hydronium may move from the anode chamber to the cathode chamber through the diaphragm. When nitrogen and hydronium react to produce ammonia, water is also produced at the same time. As a result, liquid water is produced in the cathode chamber. As shown in Figure 4, if the cathode electrode 122A has a water-absorbing component 1225, it can immediately absorb the liquid water produced in the cathode chamber. 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 desiccants such as calcium oxide and calcium chloride.

[0075] As described above, the ammonia production apparatus, by having a water-absorbing component 1225, can immediately absorb the liquid water generated in the cathode chamber, thereby suppressing the alteration of the ammonia synthesis catalyst 1222 by the liquid water, the coating of the ammonia synthesis catalyst 1222 by water, and the dissolution of the generated gaseous ammonia into the liquid water.

[0076] The ammonia production apparatus of this embodiment further includes a nitrogen separation means, which can separate nitrogen from the air and supply the nitrogen to the cathode chamber.

[0077] Figure 5 is a schematic diagram showing another example of the ammonia production apparatus of this embodiment. As shown in Figure 5, the ammonia production apparatus 40 may also include a nitrogen separation means 160. 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.

[0078] [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 directly connected to the cathode chamber 120 of the electrolytic device 100A via gas piping or the like to supply nitrogen, 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 of the electrolytic device 100A. 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.

[0079] The ammonia production apparatus of this embodiment may further include at least one of an anode chamber temperature adjustment means for adjusting the temperature of the anode chamber of the electrolytic device and a cathode electrode drying means for drying the cathode electrode.

[0080] Figure 6 is a schematic diagram showing yet another example of the ammonia production apparatus of this embodiment. As shown in Figure 6, in the ammonia production apparatus 50, the electrolytic device 100B may include at least one of an anode chamber temperature adjustment means for adjusting the temperature of the anode chamber 110 and a cathode electrode drying means for drying the cathode electrode 122. The anode chamber temperature adjustment means and the cathode electrode drying means 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.

[0081] [Cathode Electrode Drying Means] As described above, in this embodiment, the electrolytic apparatus can be equipped with cathode electrode drying means for drying the cathode electrode. By equipping the electrolytic apparatus 100A with cathode electrode drying means, it is possible to suppress the adhesion of liquid water to the cathode electrode 122 and to suppress the presence of liquid water in the cathode chamber 120. Furthermore, since the presence of liquid water in the cathode chamber 120 can be suppressed, it is possible to suppress the dissolution of the generated gaseous ammonia into liquid water, and the cost of separating ammonia from water tends to be reduced.

[0082] The cathode electrode drying means is not particularly limited as long as it can dry the cathode electrode 122 and prevent liquid water from adhering to the cathode electrode 122. Examples of the cathode electrode drying means 150 include the nitrogen flow rate adjustment means 150a, the cathode chamber temperature adjustment means 150b, and the nitrogen gas temperature adjustment means 150c shown in Figure 6. These can be used individually or in combination of two or more.

[0083] 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 using 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 a control valve that adjusts the flow rate of gaseous nitrogen is used.

[0084] Furthermore, increasing the temperature inside the cathode chamber 120 also reduces the amount of liquid water inside the cathode chamber 120. From this perspective, the cathode chamber temperature adjustment means 150b can increase the temperature inside the cathode chamber 120, thereby drying the cathode chamber 120 and also drying the cathode electrode 122, thereby suppressing the adhesion of liquid water to the cathode electrode 122.

[0085] 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.

[0086] Furthermore, by increasing the temperature of the nitrogen gas flowing 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, heating the nitrogen gas with the nitrogen gas temperature adjustment means 150c and increasing the temperature inside the cathode chamber 120 dries the cathode chamber 120 and suppresses the adhesion of liquid water to the cathode electrode 122. In addition, when lowering the temperature inside the cathode chamber 120, the nitrogen gas temperature adjustment means 150c may be used to cool the nitrogen gas and lower the temperature inside the cathode chamber 120.

[0087] [Anode Chamber Temperature Adjustment Means] In this embodiment, the electrolytic apparatus may be equipped with an anode chamber temperature adjustment means for raising the temperature of the anode chamber. By equipping the ammonia production apparatus with an anode chamber temperature adjustment means, 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.

[0088] The anode chamber temperature adjustment means is not particularly limited as long as it can adjust the temperature inside the anode chamber 110. Examples include an electrolyte temperature adjustment means 140a that adjusts the temperature of the electrolyte 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 6 shows a configuration in which the electrolyte heated by the electrolyte 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, and the inside of the anode chamber 110 is directly heated 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, the electrolyte cooled by the electrolyte 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 electrolyte temperature adjustment means 140a can be a means for adjusting the temperature of the electrolyte solution supplied into the anode chamber 110 to 25°C to 100°C, more preferably 30°C to 90°C, and even more preferably 40°C to 80°C.

[0089] Figure 6 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.

[0090] Figure 6 shows an electrolytic apparatus 100B that includes all of the following: electrolyte temperature adjustment means 140a, anode chamber temperature adjustment means 140b, nitrogen flow rate adjustment means 150a, cathode chamber temperature adjustment means 150b, and nitrogen gas temperature adjustment means 150c. However, the electrolytic apparatus 100B may include only one of these means, or any two or more of them. Furthermore, the ammonia production apparatus 50 may have multiple electrolyte temperature adjustment means 140a, anode chamber temperature adjustment means 140b, 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 40 may include both a means for performing heating by resistance heating and a means for performing heating by electromagnetic wave heating as the electrolyte temperature adjustment means 140a.

[0091] The ammonia production apparatus of this embodiment can extract and reuse water from the waste liquid from the anode chamber.

[0092] Figure 7 is a schematic diagram showing yet another example of the ammonia production apparatus of this embodiment. As shown in Figure 7, the ammonia production apparatus 60 may extract and reuse water from the waste liquid from the anode chamber 110 of the electrolytic device 100C. In this case, the ammonia production apparatus 60 may be equipped with an electrolyte separation means 180. The electrolyte 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 description will be omitted unless otherwise specified.

[0093] [Electrolyte Separation Means] In the electrolyte separation means 180, water is separated and extracted from the electrolyte, the oxygen dissolved in the electrolyte, and the waste liquid containing gaseous oxygen. The electrolyte separation means 180 is not particularly limited, but for example, oxygen is removed from the waste liquid using a gas-liquid separation method, and the electrolyte is separated and extracted.

[0094] In Figure 7, the ammonia production apparatus 60 is equipped with an electrolyte temperature adjustment means 140a, and the electrolyte separated and extracted from the waste liquid is returned to the electrolyte temperature adjustment means 140a. On the other hand, if the ammonia production apparatus 60 is not equipped with an electrolyte temperature adjustment means 140a, a pipe for transporting the electrolyte extracted from the waste liquid in the electrolyte separation means 180 may be connected to the pipe supplying the electrolyte to the anode chamber 110.

[0095] The ammonia production apparatus of this embodiment can reuse the nitrogen gas contained in the exhaust gas obtained from the second gas separation means or separation apparatus.

[0096] Figure 8 is a schematic diagram showing yet another example of the ammonia production apparatus of this embodiment. As shown in Figure 8, in the ammonia production apparatus 70, gaseous nitrogen contained in the exhaust gas obtained from the second gas separation means 420 or separation apparatus 300 in Figure 1 may be reused. The following describes in detail the manner in which gaseous nitrogen is reused. In addition, elements that are the same as those already described will be given the same numbering and their description will be omitted unless otherwise specified.

[0097] In Figure 8, nitrogen discharged in the second gas separation means 420 or separation device 300 is returned to the nitrogen flow rate adjustment means 150a. On the other hand, if the ammonia production apparatus 70 does not have the nitrogen flow rate adjustment means 150a, a pipe for supplying the nitrogen discharged in the second gas separation means 420 or separation device 300 may be connected to the pipe supplying gaseous nitrogen to the cathode chamber 120 of the electrolytic device 100D.

[0098] The ammonia production apparatus of this embodiment can be configured such that the cathode electrode has a water-repellent component.

[0099] Figure 9 is a schematic enlarged view showing another example of the vicinity of the cathode electrode in this embodiment. As shown in Figure 9, the cathode electrode 122B may have a water-repellent component 1226. Water repellency means, for example, that the contact angle with water is 90° or more. The water-repellent component 1226 will be described in detail below. Elements that are the same as those already described will be given the same numbering and their description will be omitted unless otherwise specified.

[0100] The aforementioned membrane 130 is mostly impermeable to substances other than ions, but other substances may permeate it. 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 hydronium, and this hydronium moves from the anode chamber 110 to the cathode chamber 120 through the membrane 130. Then, in the cathode chamber 120, when nitrogen and hydronium react to produce ammonia, water is also produced at the same time, resulting in the presence of liquid water. In this regard, the presence of the water-repellent component 1226 in the cathode electrode 122B suppresses the entry of water into the cathode electrode 122B. As a result, it is possible to suppress the contact of liquid water that has moved from the anode chamber 110 to the cathode chamber 120 via the diaphragm 130 with the ammonia synthesis catalyst 1222 in the cathode electrode 122B. Therefore, it is possible to suppress the alteration of the ammonia synthesis catalyst 1222 by the liquid water, and the ammonia synthesis catalyst 1222 from being coated with water. In other words, ammonia can be produced efficiently.

[0101] 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). Specific examples of MOFs include ZIF (zeolitic imidazolate framework)-71, MIL-40B, and Zn(tbip).

[0102] The method for preparing the cathode electrode 122B is not particularly limited, but for example, the following method can be used. That is, first, the carrier 1223 is attached to the gas diffusion layer 1221. Then, the ammonia synthesis catalyst 1222 is supported on the carrier 1223. Then, the binder 1224 and the water-repellent component 1226 are attached to the gas diffusion layer 1221, and the carrier 1223, binder 1224, and water-repellent component 1226 are fixed to one side of the gas diffusion layer 1221 to prepare the cathode electrode 122B. Alternatively, first, the ammonia synthesis catalyst 1222 is supported on the carrier 1223. Subsequently, the carrier 1223 supporting the ammonia synthesis catalyst 1222, the binder 1224, and the water-repellent component 1226 are mixed to obtain a mixture, and this mixture is attached to the gas diffusion layer 1221 to fix the ammonia synthesis catalyst 1222, the carrier 1223, the binder 1224, and the water-repellent component 1226 to one side of the gas diffusion layer 1221, thereby preparing the cathode electrode 122B. Note that the cathode electrode 122B may also contain the water-absorbing component found in the cathode electrode 122A shown in Figure 4 above, along with the water-repellent component 1226, etc.

[0103] Furthermore, each of the optional components described above (for example, nitrogen separation means, cathode electrode drying means, anode chamber temperature adjustment means, water separation means, means for reusing gaseous nitrogen contained in the exhaust gas obtained from the separation means, and water-absorbing and water-repellent components 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.

[0104] Furthermore, the ammonia production apparatus of this embodiment can be applied to a method for producing ammonia. For example, the method for producing ammonia 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 method for producing ammonia of this embodiment may also include a recovery step in which the ammonia produced in the ammonia production step is separated and recovered.

[0105] 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.

[0106] In the ammonia recovery process, the separation device 300 described above may be used. This allows ammonia to be separated and recovered from the gas discharged from the cathode chamber 120.

[0107] 100, 100A, 100B, 100C, 100D... Electrolytic device, 10, 20, 40, 50, 60, 70... Ammonia production device, 110... Anode chamber, 112... Anode electrode, 120... Cathode chamber, 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, 140a... Electrolyte temperature adjustment means, 140b... Anode chamber temperature adjustment means, 150a... Nitrogen flow rate adjustment means, 150b... Cathode chamber temperature adjustment means, 150c... Nitrogen gas temperature adjustment means, 160... Nitrogen separation means, 180... Electrolyte separation means

Claims

1. An ammonia production apparatus comprising: an electrolytic device having an anode electrode with a water electrolytic catalyst and supplied with water; a cathode chamber having an ammonia synthesis catalyst and supplied with gaseous nitrogen; and a diaphragm provided between the anode chamber and the cathode chamber, wherein the cathode chamber produces a mixture containing at least ammonia and water; and a separation device for separating at least one of the ammonia and water from the mixture produced in the cathode chamber.

2. The ammonia production apparatus according to claim 1, wherein the pH of the mixture is 8.0 or higher.

3. The ammonia production apparatus according to claim 1 or 2, wherein the separation device is supplied with at least the mixture and the separation gas, and separates the ammonia in the mixture as gaseous ammonia.

4. The ammonia production apparatus according to claim 3, wherein the separated gas includes residual nitrogen gas of the gas supplied to the cathode chamber.

5. The ammonia production apparatus according to claim 3 or claim 4, wherein the temperature of the separated gas is 50 to 90°C.

6. An ammonia production apparatus according to any one of claims 1 to 5, further comprising a gas-liquid separation device for supplying at least the mixture and gaseous nitrogen and hydrogen, and separating the gas from a liquid containing at least the mixture.

7. The ammonia production apparatus according to any one of claims 1 to 6, wherein the amount of nitrogen gas supplied to the cathode chamber is 1.5 times or more the amount required for the ammonia synthesis reaction in the electrolytic device.

8. The ammonia production apparatus according to any one of claims 1 to 7, wherein the diaphragm is an ion exchange membrane or a porous membrane.

9. The ammonia production apparatus according to any one of claims 1 to 8, wherein the ammonia synthesis catalyst comprises a molybdenum complex.

10. The ammonia production apparatus according to any one of claims 1 to 9, wherein the cathode electrode includes a carrier on which the ammonia synthesis catalyst is supported.

11. The ammonia production apparatus according to claim 10, 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.

12. The ammonia production apparatus according to claim 10 or claim 11, wherein the cathode electrode includes a binder for binding the carrier.

13. The ammonia production apparatus according to claim 12, wherein the binder comprises an ionomer.

14. The ammonia production apparatus according to any one of claims 1 to 13, wherein the cathode electrode includes at least one gas diffusion layer selected from the group consisting of carbon paper, carbon cloth, and carbon felt.

15. An ammonia production apparatus according to any one of claims 1 to 14, comprising a nitrogen separation means for separating nitrogen from a nitrogen-containing mixed gas to obtain gaseous nitrogen.

16. 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 15, and supplying water to the anode chamber of the ammonia production apparatus, and producing ammonia from nitrogen by electrolytic synthesis.

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

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