Synthesis unit for ammonia

Abstract

To provide a synthesis unit capable of stably producing ammonia.SOLUTION: A synthesis unit comprises: an electrochemical cell which comprises a cylindrical electrolyte, a cathode arranged inside the electrolyte, and an anode arranged outside the electrolyte; and a plasma generation device which includes a cylindrical electrode member including an electrode arranged inside the electrochemical cell leaving space with the cathode, and produces plasma between the electrode and cathode, wherein a raw material gas is supplied to first space inside the electrode member, the electrochemical cell produces hydrogen in second space between the electrode member and cathode, and the electrode is provided with a plurality of holes connecting the first space and second space together, the cathode serving as a ground electrode of the plasma generation device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a synthesis apparatus for synthesizing ammonia by reacting nitrogen with hydrogen. [Background technology]

[0002] A prior art technique for synthesizing ammonia by reacting nitrogen excited using a plasma generator with hydrogen generated by electrolysis of water is disclosed in Patent Document 1. Patent Document 2 and Non-Patent Document 1 disclose prior art techniques for synthesizing ammonia using plasma in combination with an electrochemical cell containing a proton-conductive electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-164736 [Patent Document 2] Chinese Utility Model No. 217148587 [Non-patent literature]

[0004] [Non-Patent Document 1] ACS Energy Lett. 2021, 6, 2, 313-319 Summary of the Invention [Problem to be solved by the invention]

[0005] In the prior art, if the reaction for synthesizing ammonia occurs locally, the amount of ammonia produced becomes unstable.

[0006] The present invention has been made to solve the problems, and an object of the present invention is to provide a synthesis apparatus that can stably produce ammonia. [Means for solving the problem]

[0007] A first aspect for achieving this object is a synthesis apparatus for synthesizing ammonia by exciting a raw material gas containing nitrogen, the synthesis apparatus comprising: an electrochemical cell including a cylindrical electrolyte, a cathode arranged inside the electrolyte, and an anode arranged outside the electrolyte; and a plasma generation device including a cylindrical electrode member including an electrode arranged inside the electrochemical cell with a gap between the cathode, the plasma generation device generating plasma between the electrode and the cathode, wherein the raw material gas is supplied to a first space inside the electrode member, the electrochemical cell generates hydrogen in a second space between the electrode member and the cathode, the electrode member has a plurality of holes connecting the first space and the second space, and the cathode also serves as an earth electrode for the plasma generation device.

[0008] In the second embodiment, in the first embodiment, the largest hole among the holes is 1 / 6 or less of the inner diameter of the electrode.

[0009] In a third aspect, in the first or second aspect, the number of holes provided in the portion of the electrode member that overlaps with the electrochemical cell per unit area of ​​the electrode member is greater in the portion downstream of the raw material gas than in the portion upstream of the raw material gas.

[0010] In a fourth aspect, in any one of the first to third aspects, the sum of the areas of the holes provided in the portion of the electrode member that overlaps with the electrochemical cell is larger in the portion downstream of the raw material gas than in the portion upstream of the raw material gas.

[0011] In a fifth aspect, in any one of the first to fourth aspects, the partial pressure of the source gas in the portion of the first space overlapping with the electrochemical cell is higher in the portion downstream of the source gas than in the portion upstream of the source gas.

[0012] A sixth aspect is any of the first to fifth aspects, further comprising a restrictor that reduces the flow rate of the source gas downstream in a portion of the first space that overlaps with the electrochemical cell compared to the flow rate of the source gas upstream. [Effects of the Invention]

[0013] According to the present invention, an electrochemical cell includes a cylindrical electrolyte, a cathode, and an anode. A cylindrical electrode member is provided inside the cathode, and holes are provided in the electrode member connecting a first space inside the electrode member with a second space between the cathode and the electrode member. Therefore, the source gas supplied to the first space is dispersed through the holes into the second space. Because the cathode of the electrochemical cell also serves as the ground electrode of the plasma generator, the hydrogen generated in the second space is more likely to react with nitrogen activated by the plasma over a wide area of ​​the second space. Therefore, ammonia can be produced stably. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic cross-sectional view of an ammonia synthesis apparatus according to a first embodiment. [Figure 2] FIG. 10 is a schematic cross-sectional view of an ammonia synthesis apparatus according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a schematic cross-sectional view of an ammonia synthesis apparatus 10 according to a first embodiment. The synthesis apparatus 10 includes a plasma generator 11 and an electrochemical cell 20.

[0016] The plasma generator 11 is a device that generates reactive plasma, so-called atmospheric pressure plasma, in a high-density medium at atmospheric pressure or higher. The plasma generator 11 includes an electrode member 11a including an electrode 12, and a power supply 17 that applies a voltage to the electrode 12. The electrode member 11a includes a dielectric 16 arranged on the electrode 12. In this embodiment, the electrode member 11a includes a cylindrical electrode 12 with a bottom, and a cylindrical dielectric 16 arranged on the outer periphery of the electrode 12.

[0017] The electrode member 11a is hollow and cylindrical, with at least one end 12a open and a first space 13 provided inside, and has holes 14 that connect to the first space 13. The holes 14 are connected through the electrode 12 and the dielectric 16. A plurality of holes 14 are scattered between the end 12a and the other end 12b of the electrode member 11a. The size of the holes 14 is smaller than the inner diameter D of the electrode 12 (the diameter of the first space 13). The holes 14 may be formed in the electrode member 11a using a tool such as a drill or laser processing. Alternatively, the electrode 12 and the dielectric 16 may be made of a material such as a mesh or fiber, and the holes 14 may be formed between the fibers or openings in the mesh.

[0018] In this embodiment, the electrode member 11a includes a restricting portion 15 whose end 12b is closed. The restricting portion 15 closes the first space 13 inside the electrode member 11a and restricts the flow of the source gas near the end 12b, which flows from the end 12a toward the end 12b of the electrode member 11a. The source gas contains nitrogen and water (water vapor).

[0019] Examples of the material of electrode 12 include metal and carbon. When electrode 12 is made of a metal, electrode 12 contains one or more elements selected from Groups 4 to 14 of the periodic table based on the IUPAC 1990 Recommendations. Examples of elements include Al, Ti, Cr, Fe, Ni, Co, Cu, Zn, Ru, Ag, Pd, Pt, and Au.

[0020] The dielectric 16 prevents arc discharge caused by a large current flowing locally between the electrode 12 and the cathode 22 (described later). Because electric charge accumulates in the dielectric 16, when the direction of the voltage changes after the initial discharge, a discharge can be generated at a lower voltage than the initial discharge. Therefore, plasma can be generated with a small input energy. Examples of the dielectric 16 include a membrane, film, or cylinder made of a material selected from glass, ceramics, synthetic resin, etc. The dielectric 16 may be provided inside the hole 14 of the electrode 12 as long as it does not block the hole 14.

[0021] The power supply 17 is a device that applies an AC voltage between the electrode 12 and the cathode 22 (described later). The AC voltage may be, for example, a sine wave, a triangular wave, a sawtooth wave, or a pulse wave of about 50 Hz to 100 MHz.

[0022] The electrochemical cell 20 is a device that generates hydrogen and oxygen by electrolysis of water (water vapor). The electrochemical cell 20 is disposed outside the electrode member 11a and is heated to the operating temperature of the electrochemical cell 20 (approximately 400°C to 900°C) by a heater (not shown). Because the electrochemical cell 20 is disposed outside the electrode member 11a, the electrochemical cell 20 can be easily heated by the heater.

[0023] The electrochemical cell 20 includes a cylindrical electrolyte 21, a cathode 22 disposed inside the electrolyte 21, and an anode 23 disposed outside the electrolyte 21. The electrochemical cell 20 is a so-called cylindrical vertical stripe cell. The positive electrode of a power supply 24 (DC power supply) is connected to the anode 23, and the negative electrode of the power supply 24 is connected to the cathode 22. The cathode 22 is grounded and also serves as the earth electrode of the plasma generator 11, which is connected to the earth.

[0024] The electrolyte 21 is made of a solid oxide that exhibits oxide ion conductivity under the operating conditions of the electrochemical cell 20. Examples of the solid oxide include stabilized zirconia and ceria-based solid solutions. Examples of the solid oxide include a solid solution of alumina with one or more selected from stabilized zirconia and ceria-based solid solutions. Examples of stabilizers for stabilized zirconia include CaO, MgO, YO, ScO, and YbO. Examples of elements that dissolve in ceria in ceria-based solid solutions include Gd, Sm, and Y.

[0025] The cathode 22 includes a current collector connected to a power source 24, and a reduction reaction occurs on the cathode 22. The cathode 22 is exemplified by a cermet containing a metal catalyst having electronic conductivity and an oxide having oxide ion conductivity. Examples of the metal catalyst include Cr, Fe, Co, Cu, Ru, Pd, Ag, Pt, Au, and Ni. The oxide is a solid electrolyte, and examples thereof include stabilized zirconia and ceria-based solid solutions. Examples of stabilizers for stabilized zirconia include CaO, MgO, YO, ScO, and YbO. Examples of elements dissolved in ceria in ceria-based solid solutions include Gd, Sm, and Y. Ceria-based solid solutions have electronic conductivity and oxygen ion conductivity.

[0026] The anode 23 includes a current collector connected to a power source 24, and the oxidation reaction occurs on the anode 23. The material of the anode 23 is a perovskite oxide, La 1-X Sr X MnO 3-δ ,La 1-X Sr X CoO 3-δ ,La 1-X Sr X Co 1-Y Fe Y O 3-δ ,Pr 1-X Sr X MnO 3-δ Examples of the material for the anode 23 include a composite material of one or more oxides selected from these perovskite oxides and a material that can form the electrolyte 21.

[0027] A cylindrical second space 25 is provided between the dielectric 16 of the plasma generator 11 and the cathode 22 of the electrochemical cell 20. Holes 14 provided in the electrode member 11a of the plasma generator 11 connect the first space 13 and the second space 25. The size of the largest hole among the holes 14 is 1 / 6 or less of the inner diameter D of the electrode 12.

[0028] When the overlapping portion between the electrode member 11a and the electrochemical cell 20 (the portion where the second space 25 is provided) is divided into two equal parts in the longitudinal direction (the vertical direction in FIG. 1) to partition the electrode member 11a, the first space 13, and the second space 25 into an upstream portion 26 close to the end 12a of the electrode member 11a and a downstream portion 27 close to the end 12b of the electrode member 11a, the number of holes 14 per unit area of ​​the electrode member 11a is greater in the downstream portion 27 than in the upstream portion 26. In addition, the total area of ​​the holes 14 provided in the downstream portion 27 is greater than the total area of ​​the holes 14 provided in the upstream portion 26.

[0029] In the synthesis apparatus 10, the electrochemical cell 20 is heated to an operating temperature of approximately 400°C to 900°C. A plurality of holes 14 are provided in the electrode member 11a, and the size of the holes 14 is smaller than the inner diameter D of the electrode 12. Therefore, when a raw material gas containing nitrogen and water (water vapor) is supplied from the end 12a of the electrode member 11a, the raw material gas passes through the holes 14 and moves little by little from the first space 13 to the second space 25 while flowing toward the end 12b of the electrode member 11a. The water vapor contained in the raw material gas is reduced at the cathode 22, generating hydrogen and oxygen ions.

[0030] When an AC voltage is applied between the electrode 12 and the cathode 22 of the plasma generator 11, and the voltage reaches a discharge initiation voltage, the gas in the second space 25 undergoes dielectric breakdown, generating a dielectric barrier discharge in the second space 25. The nitrogen contained in the source gas is converted into active nitrogen molecules or atomic nitrogen by the dielectric barrier discharge, resulting in the cleavage of nitrogen-nitrogen triple bonds. Highly reactive active species, such as active nitrogen molecules and atomic nitrogen, are present in the plasma in the second space 25. Because the cathode 22 is located in the second space 25, atomic hydrogen generated on the surface of the cathode 22 is more likely to react with active nitrogen molecules or atomic nitrogen before becoming hydrogen molecules. This improves the reactivity of hydrogen. As a result, selectivity to ammonia is improved.

[0031] If the source gas were to be excessively consumed in the upstream section 26, a reaction synthesizing ammonia would occur locally in the upstream section 26, destabilizing the flow rate of the source gas reaching the downstream section 27 and destabilizing the amount of ammonia produced. According to this embodiment, the source gas flows through the first space 13 and reaches the entire second space 25 via the holes 14 in the electrode member 11a, and the reaction between activated nitrogen and hydrogen generated at the cathode 22 occurs in both the upstream section 26 and the downstream section 27. This increases the amount of ammonia produced, enabling stable ammonia production. Furthermore, this prevents localized reactions, reducing partial wear of the cathode 22. This contributes to a longer life for the electrochemical cell 20.

[0032] The oxygen ions generated at the cathode 22 pass through the electrolyte 21 to reach the anode 23 and are oxidized at the anode 23, generating oxygen at the anode 23. The oxygen generated at the anode 23 is supplied to, for example, a combustor (not shown). The combustor supplied with oxygen can reduce the amount of nitrogen involved in combustion, thereby significantly improving efficiency and further reducing the generation of NOx.

[0033] In the synthesis apparatus 10, the operating temperature of the electrochemical cell 20 is high, at around 400°C to 900°C, so the activation overvoltage is very low, and hydrogen can be produced with high efficiency relative to the amount of power input. Furthermore, heat from a waste heat source such as a combustor can be used to bring the electrochemical cell 20 to its operating temperature and to produce steam. This allows less power to be input to the electrochemical cell 20 to obtain the same amount of hydrogen compared to the power input for water electrolysis in prior art. This therefore reduces the power consumption rate for ammonia synthesis.

[0034] Since the electrochemical cell 20 includes an oxide ion conductive electrolyte 21, the transport number of ionic conduction in the electrolyte 21 can be increased, thereby improving the faradaic efficiency of the synthesis apparatus 10.

[0035] The size of the largest hole among holes 14 is 1 / 6 or less of the inner diameter D of electrode 12, which prevents a large amount of source gas from leaking from the large holes into second space 25. This reduces the variation in concentration of the source gas supplied to second space 25 through holes 14, allowing for more stable production of ammonia.

[0036] Since the raw material gas flows from end 12a to end 12b of first space 13, the ammonia concentration in downstream portion 27 of second space 25 becomes higher than the ammonia concentration in upstream portion 26. Therefore, in order to allow the chemical reaction that produces ammonia from nitrogen and hydrogen to proceed in downstream portion 27, it is advantageous for the amount of raw material gas supplied to second space 25 in downstream portion 27 to be greater than the amount of raw material gas supplied to second space 25 in upstream portion 26.

[0037] In the synthesis apparatus 10, the number of holes 14 per unit area of ​​the electrode member 11a is greater in the downstream portion 27 of the electrode member 11a than in the upstream portion 26 thereof, and therefore, compared to the reverse relationship, the amount of source gas supplied to the downstream portion 27 of the second space 25 can be made greater than the amount of source gas supplied to the upstream portion 26 of the second space 25. Since the chemical reaction that produces ammonia can also proceed in the downstream portion 27, the amount of ammonia produced can be increased.

[0038] In the synthesis apparatus 10, the sum of the areas of the holes 14 provided in the downstream portion 27 of the electrode member 11a is larger than the sum of the areas of the holes 14 provided in the upstream portion 26 of the electrode member 11a, and therefore, compared to the case where the relationship is reversed, the amount of source gas supplied to the downstream portion 27 of the second space 25 can be made larger than the amount of source gas supplied to the upstream portion 26 of the second space 25. Since the chemical reaction that produces ammonia can also proceed in the downstream portion 27, the amount of ammonia produced can be increased.

[0039] In the synthesis apparatus 10, the restricting section 15 is provided in the electrode member 11a, so the flow rate of the raw material gas in the downstream section 27 of the first space 13 can be made smaller than the flow rate of the raw material gas in the upstream section 26. Since the average flow velocity of the raw material gas in the downstream section 27 of the first space 13 is smaller than the average flow velocity of the raw material gas in the upstream section 26, the partial pressure of the raw material gas in the downstream section 27 becomes higher than the partial pressure of the raw material gas in the upstream section 26. Since the chemical reaction that produces ammonia can also proceed in the downstream section 27, the amount of ammonia produced can be increased.

[0040] A second embodiment will be described with reference to Fig. 2. In the first embodiment, a synthesis apparatus 10 including an oxide ion conductive electrolyte 21 was described. In contrast, in the second embodiment, a synthesis apparatus 30 including a proton conductive electrolyte 34 will be described. In the second embodiment, the same parts as those described in the first embodiment are designated by the same reference numerals as in the first embodiment, and description thereof will be omitted.

[0041] 2 is a schematic cross-sectional view of an ammonia synthesis apparatus 30 according to the second embodiment. The synthesis apparatus 30 includes a plasma generator 31 that generates atmospheric pressure plasma, and an electrochemical cell 33 that generates hydrogen and oxygen by electrolysis of water (water vapor).

[0042] The plasma generator 31 includes a cylindrical electrode member 31a having a hole 14 formed therein. The electrode member 31a includes a cylindrical electrode 12 and a cylindrical dielectric 16 arranged on the outer periphery of the electrode 12. The hole 14 is formed in an upstream portion 26 near the end 12a of the electrode member 31a and a downstream portion 27 near the end 12b of the electrode member 31a, which are formed by dividing the overlapping portion between the electrode member 31a and the electrochemical cell 33 (the portion where the second space 37 is provided) into two equal parts in the longitudinal direction (the vertical direction in FIG. 2). No hole 14 is formed in any portion of the electrode member 31a other than the upstream portion 26 and the downstream portion 27. This is to prevent waste of the source gas.

[0043] A restricting unit 32 is connected to the end 12b of the electrode member 31a, which makes the flow rate of the raw material gas in the downstream section 27 less than the flow rate of the raw material gas in the upstream section 26. In this embodiment, the restricting unit 32 is a valve whose opening degree can be adjusted, and as the opening degree becomes smaller, the flow rate of the raw material gas in the restricting unit 32 decreases, and when the restricting unit 32 is completely closed, the flow of the raw material gas in the restricting unit 32 stops.

[0044] The electrochemical cell 33 includes a cylindrical electrolyte 34 disposed on the outside of the electrode member 31a, a cathode 35 disposed on the inner periphery of the electrolyte 34, and an anode 36 disposed on the outer periphery of the electrolyte 34. The electrochemical cell 33 is a so-called cylindrical vertical stripe cell. The cathode 35 also serves as a ground electrode for the plasma generator 31.

[0045] The material of the electrolyte 34 may be a substance that exhibits proton conductivity under the operating conditions of the electrochemical cell 33. Examples of the substance that exhibits proton conductivity include perovskite-type oxides (ceramics) such as BaZrO3 in which the B site is substituted with trivalent metal ions such as Y or In.

[0046] The cathode 35 may be made of a cermet containing an electron-conducting metal catalyst and a proton-conducting oxide. Examples of the metal catalyst include Cr, Fe, Co, Cu, Ru, Pd, Ag, Pt, Au, and Ni. Examples of the oxide include perovskite-type oxides such as BaZrO3, in which the B site is substituted with a trivalent metal ion such as Y or In.

[0047] The material of the anode 36 is the perovskite oxide La 1-X Sr X MnO 3-δ ,La 1-X Sr X CoO 3-δ ,La 1-X Sr X Co 1-Y Fe Y O 3-δ ,Pr 1-X Sr X MnO 3-δExamples of the material for the anode 36 include a composite material of one or more oxides selected from these perovskite oxides and a material that can form the electrolyte 34.

[0048] A cylindrical second space 37 is provided between the cathode 35 and the dielectric 16. A cylindrical third space 39 is provided between the anode 36 and an outer casing 38 arranged outside the anode 36. The outer casing 38 can be made of stainless steel or the like. Water (water vapor) is supplied to the third space 39 from the upstream section 26. The water vapor is carried to the anode 36 by an inert gas such as nitrogen or argon, or air. At the anode 36, hydrogen is converted from the water into protons (H + ) and are separated.

[0049] The protons generated at the anode 36 pass through the electrolyte 34 to reach the cathode 35 and are reduced at the cathode 35, generating hydrogen at the cathode 35. While flowing through the first space 13, the raw material gas passes through the holes 14 of the electrode member 31a and spreads throughout the second space 37.

[0050] Because the cathode 35 also serves as the ground electrode of the plasma generator 31, nitrogen ions, activated nitrogen molecules, atomic nitrogen, and the like in the plasma are more likely to reach the surface of the cathode 35. This increases the probability that atomic hydrogen generated on the surface of the cathode 35 will react with activated nitrogen molecules, atomic nitrogen, or nitrogen ions before becoming hydrogen molecules. This improves the reactivity of hydrogen with nitrogen. The reaction between activated nitrogen and hydrogen generated on the cathode 35 occurs in both the upstream section 26 and the downstream section 27, increasing the amount of ammonia produced and ensuring stable ammonia production. Furthermore, because localized reactions can be prevented, partial wear of the cathode 35 can be reduced. This is expected to extend the life of the electrochemical cell 33.

[0051] Since the operating temperature of the electrochemical cell 33 containing the proton-conductive electrolyte 34 is lower than that of the electrochemical cell 20 in the first embodiment, the temperature of the second space 37 can be lower than in the first embodiment. As a result, the equilibrium concentration in the second space 37 in the reaction of synthesizing ammonia from nitrogen and hydrogen can be increased. Therefore, the synthesis apparatus 30 is advantageous for obtaining high-concentration ammonia.

[0052] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0053] In the embodiments, synthesis apparatuses 10 and 30 that utilize dielectric barrier discharge have been described, but the present invention is not limited to this. It is naturally possible to utilize other plasmas. Examples of other plasmas include corona discharge, surface discharge, atmospheric pressure glow discharge, and microwave discharge. It is naturally possible to combine multiple plasmas.

[0054] In the embodiment, the electrode members 11a, 31a are described, each having a hole 14 penetrating both the cylindrical electrode 12 and the cylindrical dielectric 16. However, this is not necessarily limited to this. Other examples of the electrode members 11a, 31a include electrodes 12 arranged in vertical or horizontal stripes on the inner surface of a cylindrical dielectric 16 having holes 14. The electrodes 12 arranged at intervals in a horizontal or vertical stripe pattern are electrically connected to each other. In this case, the source gas flows between the first space 13 and the second space 25, 37 through the gaps between the electrodes 12 arranged in a stripe pattern and through the holes 14, thereby achieving the same effects as those of the present embodiment.

[0055] In the second embodiment, the proton-conductive electrolyte 34 includes a perovskite oxide such as BaZrO3, but is not necessarily limited to this. It is of course possible to use a perfluorocarbon-based or hydrocarbon-based polymer electrolyte for the electrolyte 34. Examples of perfluorocarbon-based proton conductors include Nafion (registered trademark) and Aquivion (registered trademark), in which sulfo groups are linked to perfluoroalkyl-based polymers. To improve the properties of the proton conductor, a polymer may be combined with inorganic particles.

[0056] Examples of hydrocarbon-based proton conductors include polymers in which sulfo groups or phosphate groups are linked to aromatic hydrocarbon-based engineering plastics. Examples of hydrocarbon-based proton conductors include polymers (SPEEK) in which sulfo groups are introduced into the main chain of polyether ether ketone. To improve the properties of proton conductors, hetero elements such as fluorine, sulfur, nitrogen, and phosphorus, or units containing these elements, may be introduced.

[0057] When a polymer electrolyte is used for the electrolyte 34, the anode 36 and the cathode 35 can be made of porous carbon carrying a catalyst such as Pt or Pt—Ru. The operating temperature of the electrochemical cell 33 containing a polymer electrolyte for the electrolyte 34 is 120° C. or less, and therefore the temperature of the second space 37 can be lowered accordingly.

[0058] Although not described in the embodiment, the temperature of the second spaces 25, 37 is set appropriately within a range from room temperature to 500° C. The pressure of the second spaces 25, 37 is set appropriately within a range from 101 kPa to 1000 kPa.

[0059] Although not described in the embodiment, it is possible to place a catalyst in the second spaces 25, 37. There are no particular limitations on the catalyst as long as it is present in the second spaces 25, 37. For example, the catalyst can be attached to the surface of the dielectric 16 that contacts the second spaces 25, 37. Examples of the shape of the catalyst attached to the dielectric 16 include a mesh, plate, and film. The catalyst contains one or more elements selected from Groups 4 to 14 of the Periodic Table based on the IUPAC 1990 Recommendations. Examples of elements include Al, Ti, Cr, Fe, Ni, Co, Cu, Zn, Ru, Ag, Pd, Pt, and Au.

[0060] A catalyst may be filled in the second spaces 25, 37. When the catalyst is filled in the second spaces 25, 37, an example of the catalyst is one in which a three-dimensional network structure skeleton made of a porous oxide such as alumina or zirconia supports the catalyst.

[0061] In the embodiments, restricting units 15, 32 have been described as those that close end 12b of electrode 12 and those that connect a valve to end 12b of electrode 12, but the present invention is not limited thereto. Restricting units 15, 32 may be configured to make the flow rate of the source gas in downstream portion 27 smaller than the flow rate of the source gas in upstream portion 26, and therefore may be configured, for example, to close the end of dielectric 16, to make the cross-sectional area of ​​downstream portion 27 of first space 13 smaller than the cross-sectional area of ​​upstream portion 26, or to connect a tube having a cross-sectional area smaller than the cross-sectional area of ​​first space 13 to end 12b of electrode 12.

[0062] In the embodiment described above, the spacing between the holes 14 in the downstream section 27 is narrower than the spacing between the holes 14 in the upstream section 26. However, this is not necessarily limited to this. It is of course possible to make the spacing between the holes 14 in the downstream section 27 equal to the spacing between the holes 14 in the upstream section 26 and to make the area of ​​each of the holes 14 in the downstream section 27 greater than the area of ​​each of the holes 14 in the upstream section 26. This is because, in this case, the amount of source gas supplied to the downstream section 27 of the second space 25, 37 can be made greater than the amount of source gas supplied to the upstream section 26 of the second space 25, 37. It is also of course possible to make the spacing between the holes 14 in the downstream section 27 equal to the spacing between the holes 14 in the upstream section 26 and to make the area of ​​the holes 14 in the downstream section 27 equal to the area of ​​the holes 14 in the upstream section 26, or to make the number of holes 14 in the downstream section 27 equal to the number of holes 14 in the upstream section 26. This is because, in this case, the flow rate of the source gas reaching the downstream section 27 can be secured. [Explanation of symbols]

[0063] 10,30 Synthesizer 11,31 Plasma generator 11a, 31a Electrode member 12 electrodes 13 The First Space 14 holes 15,32 Restricted section 20,33 Electrochemical cells 21,34 electrolytes 22,35 Cathode (earth electrode) 23,36 Anode 25,37 Second Space 26 Upstream section (upstream section of raw gas) 27 Downstream section (downstream section of raw gas) D Electrode inner diameter

Claims

1. A synthesis apparatus for synthesizing ammonia by exciting a nitrogen-containing raw material gas, comprising: an electrochemical cell comprising a cylindrical electrolyte, a cathode disposed inside the electrolyte, and an anode disposed outside the electrolyte; a plasma generating device including a cylindrical electrode member including an electrode disposed inside the electrochemical cell with a gap between the cathode and the electrode, the plasma generating device generating plasma between the electrode and the cathode; the source gas is supplied to a first space inside the electrode member, the electrochemical cell generates hydrogen in a second space between the electrode member and the cathode; a plurality of holes connecting the first space and the second space are provided in the electrode member; The cathode is a synthesis device that also serves as a ground electrode of the plasma generating device.

2. 2. The synthesis apparatus according to claim 1, wherein the size of the largest hole among the holes is 1 / 6 or less of the inner diameter of the electrode.

3. 3. The synthesis apparatus according to claim 1, wherein the number of holes provided per unit area of ​​the electrode member in a portion overlapping with the electrochemical cell is greater in a downstream portion of the electrode member than in an upstream portion of the electrode member in the direction of the source gas.

4. 3. The synthesis apparatus according to claim 1, wherein a total area of ​​the holes provided in the portion of the electrode member overlapping with the electrochemical cell is larger in a portion downstream of the source gas than in a portion upstream of the source gas.

5. 3. The synthesis apparatus according to claim 1, wherein a partial pressure of the source gas in a portion of the first space overlapping with the electrochemical cell is higher in a downstream portion of the source gas than in an upstream portion of the source gas.

6. 3. The synthesis apparatus according to claim 1, further comprising a restrictor that reduces a flow rate of the source gas on a downstream side in a portion of the first space that overlaps with the electrochemical cell compared to a flow rate of the source gas on an upstream side.

Images