WO2015133410A1 - Electrochemical reactor and composite electrochemical reactor - Google Patents

Electrochemical reactor and composite electrochemical reactor Download PDF

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WO2015133410A1
WO2015133410A1 PCT/JP2015/055968 JP2015055968W WO2015133410A1 WO 2015133410 A1 WO2015133410 A1 WO 2015133410A1 JP 2015055968 W JP2015055968 W JP 2015055968W WO 2015133410 A1 WO2015133410 A1 WO 2015133410A1
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electrochemical reactor
cathode electrode
anode electrode
gas
stabilized zirconia
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PCT/JP2015/055968
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French (fr)
Japanese (ja)
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平田　好洋
真奈 上野
太郎 下之薗
鮫島　宗一郎
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国立研究開発法人科学技術振興機構
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B01D53/229—Integrated processes (Diffusion and at least one other process, e.g. adsorption, absorption)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/32—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by electrical effects other than those provided for in group B01D61/00
    • B01D53/326—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by electrical effects other than those provided for in group B01D61/00 in electrochemical cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/62—Carbon oxides
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
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    • B01D71/0271—Perovskites
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
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    • C25B11/031—Porous electrodes
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    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
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    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
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    • B01D2255/1026—Ruthenium
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    • B01D2255/206—Rare earth metals
    • B01D2255/2061—Yttrium
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    • B01D2255/207—Transition metals
    • B01D2255/20715—Zirconium
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01D2255/00—Catalysts
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    • B01D2255/207—Transition metals
    • B01D2255/20753—Nickel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2256/00—Main component in the product gas stream after treatment
    • B01D2256/12—Oxygen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2256/00—Main component in the product gas stream after treatment
    • B01D2256/16—Hydrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/502—Carbon monoxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
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    • B01D2257/504—Carbon dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
    • B01D2257/702—Hydrocarbons
    • B01D2257/7022—Aliphatic hydrocarbons
    • B01D2257/7025—Methane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/20—Capture or disposal of greenhouse gases of methane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/40—Capture or disposal of greenhouse gases of CO2
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2
    • Y02P20/156—Methane [CH4]

Definitions

  • the present invention relates to an electrochemical reactor and a composite electrochemical reactor.
  • Patent Document 1 describes a technique aimed at artificially generating oxygen gas from carbon dioxide or carbon monoxide. Although this technique achieves the intended purpose, it is difficult to obtain oxygen gas with high efficiency.
  • JP 2013-173980 A Japanese Patent No. 5376381 JP 62-36005 A Japanese Patent Laid-Open No. Sho 62-36006 International Publication No. 2009/157454
  • Electrolytic reduction of carbon dioxide to formic acid K. S. Udupa, Gs Subraman, H. V. K. Udupa, Electrochim. Acta, vol. 16, pp. 1593-1598 (1971) Electroreduction of carbon-dioxide by metal phthalocyanines, N. Furuya, S. Koide, Electrochim. Acta, vol. 36, pp.1309-1313 (1991) Electrocatalytic formation of CH4 from CO2 on a Pt gas diffusion electrode, K. Hara, T. Sakata, J. Electrochem. Soc., Vol. 144, pp. 539-545 (1997) High-rate gas-phase CO2 reduction to ethylene and methane using gas-diffusion electrodes, R. L.
  • An object of the present invention is to provide an electrochemical reactor and a composite electrochemical reactor capable of generating oxygen gas from carbon dioxide or carbon monoxide with high efficiency.
  • the electrochemical reactor according to the present invention is provided between an anode electrode containing ruthenium and yttria stabilized zirconia, a cathode electrode containing nickel and yttria stabilized zirconia, and between the anode electrode and the cathode electrode, And an electrolyte membrane containing yttria-stabilized zirconia, allowing oxide ions to pass therethrough and preventing carbon monoxide from passing therethrough.
  • a composite electrochemical reactor includes a first electrochemical reactor that generates hydrogen and carbon monoxide from methane and carbon dioxide, and oxygen from carbon monoxide generated by the first electrochemical reactor.
  • an electrolyte membrane that is provided between the anode electrode and the cathode electrode, contains yttria-stabilized zirconia, transmits oxide ions, and blocks carbon monoxide transmission.
  • oxygen gas can be artificially generated from carbon dioxide or carbon monoxide with high efficiency by an electrochemical reaction between an anode electrode and a cathode electrode with an appropriate electrolyte membrane interposed therebetween.
  • FIG. 1 is a schematic diagram showing a configuration of an electrochemical reactor according to an embodiment of the present invention.
  • FIG. 2 is a diagram showing a method for producing a powder for an anode electrode.
  • FIG. 3 is a view showing a method for producing a powder for a cathode electrode.
  • FIG. 4 is a diagram showing a method for producing an electrolyte membrane.
  • FIG. 5 is a diagram showing a method for integrating the powder for the anode electrode, the powder for the cathode electrode, and the electrolyte membrane.
  • FIG. 6 is a diagram showing the configuration of the electrochemical reaction system used in the experiment.
  • FIG. 7 is a graph showing the CO decomposition rate in the first experiment.
  • FIG. 1 is a schematic diagram showing a configuration of an electrochemical reactor according to an embodiment of the present invention.
  • FIG. 2 is a diagram showing a method for producing a powder for an anode electrode.
  • FIG. 3 is a view showing a method for
  • FIG. 8 is a graph showing the results of analysis of the anode and cathode electrodes by X-ray diffraction in the first experiment.
  • FIG. 9 is a graph showing changes in the components of the outlet gas in the second experiment.
  • FIG. 10 is a graph showing changes in the components of the outlet gas in the third experiment.
  • FIG. 11 is a graph showing calculated values of the CO decomposition rate and the outlet gas ratio in the third experiment.
  • FIG. 12 is a graph showing the standard Gibbs free energy change ( ⁇ G 0 ) in the reaction in which C is oxidized.
  • FIG. 13 is a graph showing the relationship between precipitated C and the amount of gas used in the experiment.
  • FIG. 1 is a schematic diagram showing a configuration of an electrochemical reactor according to an embodiment of the present invention.
  • the composite electrochemical reactor 1 includes an electrochemical reactor 10, a separation membrane 30, a partition plate 31, and an electrochemical reactor 20, as shown in FIG.
  • an electrolyte membrane 13 of gadolinium-doped ceria (GDC) is sandwiched between the anode electrode 11 and the cathode electrode 12.
  • the anode electrode 11 is made of, for example, a porous body made of a mixture of Ru and GDC.
  • the cathode electrode 12 is made of, for example, a porous body made of a mixture of Ni and GDC.
  • the electrolyte membrane 13 is made of, for example, a GDC porous body.
  • the composition of GDC is not particularly limited, but is represented by, for example, Ce 0.8 Gd 0.2 O 1.9 . In this way, the electrochemical reactor 10 is configured.
  • Separation membrane 30 permeates hydrogen and prevents carbon monoxide permeation.
  • the separation membrane 30 include a polymonochloroparaxylene membrane (UCC), an amorphous nylon film (Allied Chemical and Dye Co.), an amorphous film (Du Pont) of a copolymer of an aromatic tetrabasic acid and an aromatic amine, or the like is used as a polymer non-porous film. Hydrogen molecules having a small size pass through the separation membrane 30 by molecular diffusion, but carbon monoxide does not permeate the separation membrane 30 because of its large size.
  • the separation membrane 30 When the composite electrochemical reactor 1 is used in a relatively high temperature environment, for example, an amorphous silica film is used as the separation membrane 30. In a relatively high temperature environment, hydrogen molecules can diffuse through the gaps in the silica structure, so the hydrogen molecules pass through the separation membrane 30, but carbon monoxide is large in size, so it diffuses through the gaps in the silica structure. Without passing through the separation membrane 30.
  • the partition plate 31 prevents the permeation of hydrogen. As the partition plate 31, a plate that prevents the permeation of gas is used.
  • an electrolyte membrane 23 of yttria-stabilized zirconia (YSZ) is sandwiched between the anode electrode 21 and the cathode electrode 22.
  • the anode electrode 21 is made of, for example, a porous body made of a mixture of Ru and YSZ.
  • the cathode electrode 22 is made of, for example, a porous body made of a mixture of Ni and YSZ.
  • the electrolyte membrane 23 is made of, for example, YSZ.
  • the electrolyte membrane 23 is preferably dense. That is, even if the electrolyte membrane 23 has closed pores, it is preferable that there are no open pores or communication holes.
  • the composition of YSZ is not particularly limited, for example, the proportion of Y 2 O 3 is 8 mol%, the proportion of ZrO 2 is 92 mol%, and represented by Y 0.15 Zr 0.85 O 1.93 .
  • the thickness of the electrolyte membrane 23 is, for example, about 40 ⁇ m. The thickness here is a dimension in a direction connecting the anode electrode 21 and the cathode electrode 22. In this way, the electrochemical reactor 20 is configured.
  • the electrochemical reactors 10 and 20 are used by being put in the tube 2 so that the anode electrode 11 and the cathode electrode 22 face each other with the separation membrane 30 interposed therebetween.
  • a voltage of about 1 V to 5 V is applied between the anode electrode 11 and the cathode electrode 12
  • about 1 V to 8 V is applied between the anode electrode 21 and the cathode electrode 22.
  • the temperature of the electrochemical reactor 10 is about 700 ° C. to 800 ° C.
  • the temperature of the electrochemical reactor 20 is about 800 ° C.
  • Oxide ions (O 2 ⁇ ) generated by this reduction reaction pass through the electrolyte membrane 13 together with carbon monoxide (CO) and methane (CH 4 ) and reach the anode electrode 11.
  • CO carbon monoxide
  • CH 4 methane
  • an oxidation reaction of methane represented by the formula (12) occurs at the anode electrode 11.
  • the electrochemical reactor 10 generates hydrogen and carbon monoxide from carbon dioxide and methane.
  • carbon monoxide cannot pass through the separation membrane 30 but is supplied to the cathode electrode 22 of the electrochemical reactor 20 through the bypass portion 32.
  • Oxide ions (O 2 ⁇ ) generated by this reduction reaction pass through the electrolyte membrane 23 and reach the anode electrode 21.
  • Oxide ions (O 2 ⁇ ) pass through the electrolyte membrane 23 and reach the anode electrode 21.
  • the oxide ions (O 2 ⁇ ) reach the anode electrode 21, reactions shown in the formulas (24) and (25) occur in the anode electrode 21.
  • the reaction ratio of the formula (24) is x (0 ⁇ x ⁇ 1)
  • the reaction ratio of the formula (25) is (1 ⁇ x). Therefore, when the reaction ratio x is taken into account, the reactions of the equations (24) and (25) are expressed by the equations (24 ′) and (25 ′). In the anode electrode 21, the reaction shown in the equation (26) occurs from the sum of the equations (24 ′) and (25 ′).
  • oxygen gas can be produced using the electrochemical reactor 20.
  • hydrogen and oxygen can be produced from methane and carbon dioxide.
  • hydrogen can be used as fuel for fuel cells.
  • biogas As methane, those contained in natural gas and biogas can be used. This embodiment is particularly suitable for the use of biogas. This is because biogas often contains 50 volume% to 70 volume% methane and 30 volume% to 50 volume% carbon dioxide. That is, the biogas contains not only methane supplied to the cathode electrode 22 but also carbon dioxide.
  • the electrochemical reactor 20 can also be used separately from the electrochemical reactor 10.
  • carbon dioxide is supplied toward the cathode electrode 22 of the electrochemical reactor 20, the reactions shown in the equations (31) and (32) occur at the cathode electrode 22.
  • the cathode electrode 22 undergoes a carbon dioxide reduction reaction represented by the equation (33). CO 2 + 2e ⁇ ⁇ CO + O 2 ⁇ (33)
  • the cathode electrode 22 undergoes a carbon dioxide reduction reaction represented by the equation (36). CO 2 + 4e ⁇ ⁇ C + 2O 2 ⁇ (36)
  • the reaction rate of the formula (33) is y (0 ⁇ y ⁇ 1)
  • the reaction rate of the formula (36) is (1-y). Therefore, when the reaction ratio y is taken into account, the reactions of the equations (33) and (36) are represented by the equations (33 ′) and (36 ′). In the anode electrode 21, the reaction shown in the equation (37) occurs from the sum of the equations (33 ′) and (36 ′).
  • Oxide ions (O 2 ⁇ ) generated by this reduction reaction pass through the electrolyte membrane 23 and reach the anode electrode 21.
  • the reaction shown in the equation (38) occurs at the anode electrode 21.
  • oxygen gas can be produced using the electrochemical reactor 20.
  • FIG. 2 is a diagram showing a method for producing a powder for the anode electrode 21
  • FIG. 3 is a diagram showing a method for producing a powder for the cathode electrode 22.
  • a suspension (suspension) dispersed with double-distilled water is prepared so that the solid content of the mixture is 30% by volume, and the pH of the suspension is adjusted to, for example, 10 using a 13M NH 4 OH solution. adjust.
  • the suspension is freeze-dried and calcined at 800 ° C. for 1 hour and calcined at 1000 ° C. for 2 hours in air. In this way, RuO 2 —YSZ powder is obtained as the powder for the anode electrode 21.
  • FIG. 4 is a view showing a method for producing the electrolyte membrane 23.
  • a suspension (suspension) is produced by dispersing YSZ powder in a mixed solution of toluene and isopropanol so that the solid content is 20% by volume.
  • the volume ratio of toluene and isopropanol in the mixed solution is, for example, 1: 2.
  • 9% by mass of polyethylene glycol (plasticizer) and 5% by mass of polyvinyl butyral (binder) are added to the suspension. Thereafter, the suspension is stirred for 24 hours.
  • a YSZ film is formed by the doctor blade method using the suspension after stirring.
  • the front blade is 80 ⁇ m
  • the rear blade is 150 ⁇ m
  • the feed rate is 50 mm / min
  • the drying time is one week.
  • FIG. 5 is a diagram showing a method for integrating the powder for the anode electrode 21, the powder for the cathode electrode 22, and the electrolyte membrane 23.
  • the electrolyte membrane 23 and the NiO—YSZ powder for the cathode electrode 22 are laminated together, and a pellet-like laminate is produced by uniaxial pressing at 50 MPa for 1 minute and isotropic pressing at 100 MPa for 1 minute. To do.
  • the laminate is co-sintered in air at 1400 ° C. for 4 hours to produce a co-sintered body.
  • a suspension was prepared by dispersing RuO 2 -YSZ powder for the anode electrode 21 in a 90 volume% ethanol-10 volume% polyethylene glycol mixed solution so that the solid content was 15 volume%. Screen printing is performed on the surface of the electrolyte film 23 of the co-sintered body. Subsequently, baking is performed at 900 ° C. for 1 hour.
  • the electrochemical reactor 20 provided with the anode electrode 21, the cathode electrode 22, and the electrolyte membrane 23 can be manufactured.
  • the electrochemical reactor 20 was produced by the same method as in the above embodiment. Then, the electrochemical reactor 20 was inserted into the alumina holders 121 and 122 through the glass seal 123. A glass ring 124 was interposed between the alumina holders 121 and 122. A magnetic tube 127 was connected to the lower end of the alumina holder 121 via a glass seal 125, and a magnetic tube 129 was connected to the upper end of the alumina holder 122 via a glass seal 126. An opening through which gas flows is provided at the lower end of the alumina holder 121, and an opening through which gas flows is provided at the upper end of the alumina holder 122.
  • the platinum wire 133 connected to the DC power source 131 and the platinum wire 134 connected to the ammeter 132 were connected to the anode electrode 21 and the cathode electrode 22 through these openings.
  • platinum mesh 136 and platinum paste were used to connect the platinum wires 133 and 134 to the anode electrode 21, and platinum mesh 135 and platinum paste were used to connect the platinum wires 133 and 134 to the cathode electrode 22.
  • a magnetic tube 128 that bisects the space inside the magnetic tube 127 is provided, and a magnetic tube 130 that bisects the space inside the magnetic tube 129 is provided.
  • the alumina holders 121 and 122 and the magnetic tubes 127 to 130 include HB (component: 40.6% by mass SiO 2 , 56.2% by mass Al 2 O 3 , 0.2% by mass TiO 2 , manufactured by Nikkato Co., Ltd. 0.5 wt% Fe 2 O 3, 0.2 wt% CaO, 0.1 wt% MgO, 0.5 wt% Na 2 O, with 1.7 wt% K 2 O).
  • the electrochemical reactor 20 the alumina holders 121 and 122, and the magnetic tubes 127 to 130 were kept at 870 ° C. for 15 minutes.
  • the vertical axis in FIG. 7 indicates the CO decomposition rate.
  • the CO decomposition rate was determined from the amount of O 2 gas generated at the anode electrode 21 derived from the CO decomposition reaction (2CO ⁇ 2C + O 2 ).
  • the CO decomposition rate when the applied voltage was 1.0 V was 9% to 15%.
  • the applied voltage was increased to 2.0 V or more the decomposition rate increased rapidly and reached 67% to 100% over a long period of time, although there was variation.
  • the current flowing through the electrochemical reactor 20 showed a detection limit value of 1.1 A regardless of the applied voltage, but in reality, it is considered that the current increases as the applied voltage increases.
  • FIG. 8A shows the analysis result of the surface of the cathode electrode 22
  • FIG. 8B shows the analysis result of the surface of the anode electrode 21.
  • the presence of YSZ, Ni and Pt was confirmed in the cathode electrode 22.
  • the anode electrode 21, YSZ, Ru, presence of RuO 2 and Pt was confirmed. It can be seen that Ru was oxidized to RuO 2 by a part of the transported O 2 ⁇ ions.
  • FIG. 9A shows the ratio of gas on the cathode electrode 22 side
  • FIG. 9B shows the ratio of gas on the anode electrode 21 side.
  • the cathode electrode 22 side the ratio of CO 2 was about 92% to 94%. That is, the ratio of CO 2 decreased by about 6% to 8%, and the ratio of CO gas increased by about 6% to 8%. This tendency did not depend on the applied voltage.
  • the O 2 gas ratio on the anode electrode 21 side was 2% to 9%.
  • reaction of CO 2 at the cathode electrode 22 will be considered.
  • Reactions considered to occur at the cathode electrode 22 include reactions of the formulas (41) and (42).
  • FIG. 10A shows the ratio of gas on the cathode electrode 22 side
  • FIG. 10B shows the ratio of gas on the anode electrode 21 side.
  • the composition of the outlet gas on the cathode electrode 22 side was close to the composition of the supply gas.
  • the proportion of CO gas was 50%
  • the concentration of CO gas in the outlet gas on the cathode electrode 22 side increased and the concentration of CO 2 gas decreased.
  • the current flowing through the electrochemical reactor 20 showed a detection limit value of 1.1 A regardless of the applied voltage, but in reality, it is considered that the current increases as the applied voltage increases.
  • reaction of CO and CO 2 at the cathode electrode 22 will be considered.
  • Reactions considered to occur at the cathode electrode 22 include reactions of the formulas (47) to (50).
  • CO 2 ⁇ CO + 1 / 2O 2 (47)
  • CO 2 + C ⁇ 2CO (49)
  • FIG. 11 shows calculated values of (a) CO decomposition rate (v) and (b) cathode side outlet gas ratio.
  • the calculated values according to equations (51) and (52) explain the experimental results.
  • the v value was 0%.
  • the calculated CO 2 content was about 7% lower than the measured value.
  • FIG. 12 shows the standard Gibbs free energy value for the reaction of equation (49).
  • the standard Gibbs free energy is negative at the experimental temperature (800 ° C.), which confirms that the reaction of equation (49) proceeds thermodynamically.
  • FIG. 13 is a graph showing the relationship between precipitated C and the amount of gas used in the experiment.
  • the amount of deposited carbon confirmed by the analysis result of the electron beam probe analyzer by the total amount of CO or CO 2 used in the experiment, the amount of deposited carbon with respect to 1 ml of the supply gas can be derived. From the results shown in FIG. 13, it can be said that the carbon deposition amount of CO decomposition is 21.6 times higher than the carbon deposition amount of CO 2 decomposition. Further, the amount of carbon deposited in the CO and CO 2 mixed gas decomposition is almost the same as that of CO 2 alone. This is because C precipitated from CO reacts with CO 2 and changes to CO.
  • the present invention can be used, for example, in industries related to electrochemical reactors.

Abstract

This electrochemical reactor (20) includes: an anode electrode (21) that contains ruthenium and yttria-stabilized zirconia; a cathode electrode (22) that contains nickel and yttria-stabilized zirconia; and an electrolyte membrane (23) that is provided between the anode electrode (21) and the cathode electrode (22), contains yttria-stabilized zirconia, transmits oxide ions, and obstructs the transmission of carbon monoxide.

Description

電気化学反応器及び複合電気化学反応器Electrochemical reactor and combined electrochemical reactor
　本発明は、電気化学反応器及び複合電気化学反応器に関する。 The present invention relates to an electrochemical reactor and a composite electrochemical reactor.
　近年、温室効果を有する二酸化炭素の増加による地球温暖化が、世界的な問題となっている。植物の光合成プロセスは理想的だが、これに基づく工業的システムの実用化には未だ至っていない。植物の光合成プロセスは（１）式で表され、ＣＯ２がブドウ糖として固定化されるとき、酸素ガス及び水が放出される。
　１２Ｈ２Ｏ＋６ＣＯ２＋光エネルギ→Ｃ６Ｈ１２Ｏ６（ブドウ糖）＋６Ｈ２Ｏ＋６Ｏ２・・・（１） In recent years, global warming due to an increase in carbon dioxide having a greenhouse effect has become a global problem. The plant photosynthesis process is ideal, but the industrial system based on it has not yet been put into practical use. The plant photosynthesis process is expressed by the formula (1). When CO 2 is immobilized as glucose, oxygen gas and water are released.
12H 2 O + 6CO 2 + light energy → C 6 H 12 O 6 (glucose) + 6H 2 O + 6O 2 (1)
　また、メタノールを含む水溶液中にＣＯ２を吹き込んで電解を行うと、水素、メタン、エチレン、エタン、ＣＯ、ギ酸メチル等が生成することが報告されている。 Further, it has been reported that hydrogen, methane, ethylene, ethane, CO, methyl formate, and the like are generated when electrolysis is performed by blowing CO 2 into an aqueous solution containing methanol.
　また、人工的に二酸化炭素や一酸化炭素から酸素ガスを生成することを目的とした技術が特許文献１に記載されている。この技術によれば所期の目的は達成されるものの、高い効率で酸素ガスを得ることは困難である。 Also, Patent Document 1 describes a technique aimed at artificially generating oxygen gas from carbon dioxide or carbon monoxide. Although this technique achieves the intended purpose, it is difficult to obtain oxygen gas with high efficiency.
特開２０１３－１７３９８０号公報JP 2013-173980 A 特許第５３７６３８１号公報Japanese Patent No. 5376381 特開昭６２－３６００５号公報JP 62-36005 A 特開昭６２－３６００６号公報Japanese Patent Laid-Open No. Sho 62-36006 国際公開第２００９／１５７４５４号International Publication No. 2009/157454
　本発明の目的は、二酸化炭素や一酸化炭素から酸素ガスを高い効率で生成することができる電気化学反応器及び複合電気化学反応器を提供することにある。 An object of the present invention is to provide an electrochemical reactor and a composite electrochemical reactor capable of generating oxygen gas from carbon dioxide or carbon monoxide with high efficiency.
　本発明に係る電気化学反応器は、ルテニウム及びイットリア安定化ジルコニアを含有するアノード電極と、ニッケル及びイットリア安定化ジルコニアを含有するカソード電極と、前記アノード電極と前記カソード電極との間に設けられ、イットリア安定化ジルコニアを含有し、酸化物イオンを透過させ、一酸化炭素の透過を妨げる電解質膜と、を有することを特徴とする。 The electrochemical reactor according to the present invention is provided between an anode electrode containing ruthenium and yttria stabilized zirconia, a cathode electrode containing nickel and yttria stabilized zirconia, and between the anode electrode and the cathode electrode, And an electrolyte membrane containing yttria-stabilized zirconia, allowing oxide ions to pass therethrough and preventing carbon monoxide from passing therethrough.
　本発明に係る複合電気化学反応器は、メタン及び二酸化炭素から水素及び一酸化炭素を生成する第１の電気化学反応器と、前記第１の電気化学反応器により生成された一酸化炭素から酸素を生成する第２の電気化学反応器と、を有し、前記第２の電気化学反応器は、ルテニウム及びイットリア安定化ジルコニアを含有するアノード電極と、ニッケル及びイットリア安定化ジルコニアを含有するカソード電極と、前記アノード電極と前記カソード電極との間に設けられ、イットリア安定化ジルコニアを含有し、酸化物イオンを透過させ、一酸化炭素の透過を妨げる電解質膜と、を有することを特徴とする。 A composite electrochemical reactor according to the present invention includes a first electrochemical reactor that generates hydrogen and carbon monoxide from methane and carbon dioxide, and oxygen from carbon monoxide generated by the first electrochemical reactor. An anode electrode containing ruthenium and yttria-stabilized zirconia, and a cathode electrode containing nickel and yttria-stabilized zirconia And an electrolyte membrane that is provided between the anode electrode and the cathode electrode, contains yttria-stabilized zirconia, transmits oxide ions, and blocks carbon monoxide transmission.
　本発明によれば、適切な電解質膜を間に挟んだアノード電極及びカソード電極での電気化学反応により、人工的に二酸化炭素や一酸化炭素から酸素ガスを高い効率で生成することができる。 According to the present invention, oxygen gas can be artificially generated from carbon dioxide or carbon monoxide with high efficiency by an electrochemical reaction between an anode electrode and a cathode electrode with an appropriate electrolyte membrane interposed therebetween.
図１は、本発明の実施形態に係る電気化学反応器の構成を示す模式図である。FIG. 1 is a schematic diagram showing a configuration of an electrochemical reactor according to an embodiment of the present invention. 図２は、アノード電極用の粉体を作製する方法を示す図である。FIG. 2 is a diagram showing a method for producing a powder for an anode electrode. 図３は、カソード電極用の粉体を作製する方法を示す図である。FIG. 3 is a view showing a method for producing a powder for a cathode electrode. 図４は、電解質膜を作製する方法を示す図である。FIG. 4 is a diagram showing a method for producing an electrolyte membrane. 図５は、アノード電極用の粉体、カソード電極用の粉体、及び電解質膜を一体化させる方法を示す図である。FIG. 5 is a diagram showing a method for integrating the powder for the anode electrode, the powder for the cathode electrode, and the electrolyte membrane. 図６は、実験で用いた電気化学反応システムの構成を示す図である。FIG. 6 is a diagram showing the configuration of the electrochemical reaction system used in the experiment. 図７は、第１の実験でのＣＯ分解率を示すグラフである。FIG. 7 is a graph showing the CO decomposition rate in the first experiment. 図８は、第１の実験においてアノード電極及びカソード電極のＸ線回折法による分析の結果を示すグラフである。FIG. 8 is a graph showing the results of analysis of the anode and cathode electrodes by X-ray diffraction in the first experiment. 図９は、第２の実験での出口ガスの成分の変化を示すグラフである。FIG. 9 is a graph showing changes in the components of the outlet gas in the second experiment. 図１０は、第３の実験での出口ガスの成分の変化を示すグラフである。FIG. 10 is a graph showing changes in the components of the outlet gas in the third experiment. 図１１は、第３の実験でのＣＯ分解率と出口ガス割合の計算値を示すグラフである。FIG. 11 is a graph showing calculated values of the CO decomposition rate and the outlet gas ratio in the third experiment. 図１２は、Ｃが酸化される反応における標準ギブス自由エネルギ変化（ΔＧ０）を示すグラフである。FIG. 12 is a graph showing the standard Gibbs free energy change (ΔG 0 ) in the reaction in which C is oxidized. 図１３は、析出したＣと実験に使用したガス量との関係を示すグラフである。FIG. 13 is a graph showing the relationship between precipitated C and the amount of gas used in the experiment.
　以下、本発明の実施形態について添付の図面を参照して具体的に説明する。図１は、本発明の実施形態に係る電気化学反応器の構成を示す模式図である。 Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a configuration of an electrochemical reactor according to an embodiment of the present invention.
　本実施形態に係る複合電気化学反応器１には、図１に示すように、電気化学反応器１０、分離膜３０、仕切り板３１、及び電気化学反応器２０が含まれている。 The composite electrochemical reactor 1 according to the present embodiment includes an electrochemical reactor 10, a separation membrane 30, a partition plate 31, and an electrochemical reactor 20, as shown in FIG.
　電気化学反応器１０では、アノード電極１１とカソード電極１２との間に、ガドリニウム固溶セリア（ＧＤＣ：gadolinium-doped ceria）の電解質膜１３が挟持されている。アノード電極１１は、例えばＲｕとＧＤＣとの混合物の多孔質体から構成されている。カソード電極１２は、例えばＮｉとＧＤＣとの混合物の多孔質体から構成されている。電解質膜１３は、例えばＧＤＣの多孔質体から構成されている。ＧＤＣの組成は特に限定されないが、例えばＣｅ０．８Ｇｄ０．２Ｏ１．９で表される。このようにして、電気化学反応器１０が構成されている。 In the electrochemical reactor 10, an electrolyte membrane 13 of gadolinium-doped ceria (GDC) is sandwiched between the anode electrode 11 and the cathode electrode 12. The anode electrode 11 is made of, for example, a porous body made of a mixture of Ru and GDC. The cathode electrode 12 is made of, for example, a porous body made of a mixture of Ni and GDC. The electrolyte membrane 13 is made of, for example, a GDC porous body. The composition of GDC is not particularly limited, but is represented by, for example, Ce 0.8 Gd 0.2 O 1.9 . In this way, the electrochemical reactor 10 is configured.
　分離膜３０は水素を透過させ、一酸化炭素の透過を妨げる。複合電気化学反応器１が３０℃～１００℃程度の比較的低い温度環境下で用いられる場合、分離膜３０としては、例えば、ポリモノクロロパラキシレンの膜（Ｕ．Ｃ．Ｃ）、アモルファスナイロンフィルム（Ａｌｌｉｅｄ　Ｃｈｅｍｉｃａｌ　ａｎｄ　Ｄｙｅ　Ｃｏ．）、芳香族四塩基酸と芳香族アミンとの共重合体のアモルファスフィルム（Ｄｕ　Ｐｏｎｔ）等の高分子非多孔質膜が用いられる。サイズの小さい水素分子は分子拡散により分離膜３０を通過するが、一酸化炭素はサイズが大きいため、分離膜３０を透過しない。複合電気化学反応器１が比較的高い温度環境下で用いられる場合、分離膜３０としては、例えば、非晶質シリカフィルムが用いられる。比較的高い温度環境下では、シリカの構造中の隙間を水素分子が拡散できるため、水素分子は分離膜３０を通過するが、一酸化炭素はサイズが大きいため、シリカの構造中の隙間を拡散せず、分離膜３０を透過しない。仕切り板３１は、水素の透過を妨げる。仕切り板３１としては、気体の透過を妨げる板が用いられる。 Separation membrane 30 permeates hydrogen and prevents carbon monoxide permeation. When the composite electrochemical reactor 1 is used in a relatively low temperature environment of about 30 ° C. to 100 ° C., examples of the separation membrane 30 include a polymonochloroparaxylene membrane (UCC), an amorphous nylon film (Allied Chemical and Dye Co.), an amorphous film (Du Pont) of a copolymer of an aromatic tetrabasic acid and an aromatic amine, or the like is used as a polymer non-porous film. Hydrogen molecules having a small size pass through the separation membrane 30 by molecular diffusion, but carbon monoxide does not permeate the separation membrane 30 because of its large size. When the composite electrochemical reactor 1 is used in a relatively high temperature environment, for example, an amorphous silica film is used as the separation membrane 30. In a relatively high temperature environment, hydrogen molecules can diffuse through the gaps in the silica structure, so the hydrogen molecules pass through the separation membrane 30, but carbon monoxide is large in size, so it diffuses through the gaps in the silica structure. Without passing through the separation membrane 30. The partition plate 31 prevents the permeation of hydrogen. As the partition plate 31, a plate that prevents the permeation of gas is used.
　電気化学反応器２０では、アノード電極２１とカソード電極２２との間に、イットリア安定化ジルコニア（ＹＳＺ：yttria-stabilized zirconia）の電解質膜２３が挟持されている。アノード電極２１は、例えばＲｕとＹＳＺとの混合物の多孔質体から構成されている。カソード電極２２は、例えばＮｉとＹＳＺとの混合物の多孔質体から構成されている。また、電解質膜２３は、例えばＹＳＺから構成されている。また、例えば電解質膜２３は緻密であることが好ましい。つまり、電解質膜２３に閉気孔があっても、開気孔又は連通孔はないことが好ましい。ＹＳＺの組成は特に限定されないが、例えばＹ２Ｏ３の割合が８ｍｏｌ％、ＺｒＯ２の割合が９２ｍｏｌ％であり、Ｙ０．１５Ｚｒ０．８５Ｏ１．９３で表される。電解質膜２３の厚さは、例えば４０μｍ程度である。ここでいう厚さとは、アノード電極２１とカソード電極２２とを結ぶ方向における寸法である。このようにして、電気化学反応器２０が構成されている。 In the electrochemical reactor 20, an electrolyte membrane 23 of yttria-stabilized zirconia (YSZ) is sandwiched between the anode electrode 21 and the cathode electrode 22. The anode electrode 21 is made of, for example, a porous body made of a mixture of Ru and YSZ. The cathode electrode 22 is made of, for example, a porous body made of a mixture of Ni and YSZ. The electrolyte membrane 23 is made of, for example, YSZ. For example, the electrolyte membrane 23 is preferably dense. That is, even if the electrolyte membrane 23 has closed pores, it is preferable that there are no open pores or communication holes. Although the composition of YSZ is not particularly limited, for example, the proportion of Y 2 O 3 is 8 mol%, the proportion of ZrO 2 is 92 mol%, and represented by Y 0.15 Zr 0.85 O 1.93 . The thickness of the electrolyte membrane 23 is, for example, about 40 μm. The thickness here is a dimension in a direction connecting the anode electrode 21 and the cathode electrode 22. In this way, the electrochemical reactor 20 is configured.
　ここで、本実施形態に係る複合電気化学反応器１の動作について説明する。電気化学反応器１０及び２０は、例えば、アノード電極１１とカソード電極２２とが、分離膜３０を間に挟んで対向するように管２に入れられて使用される。電気化学反応器１０では、アノード電極１１とカソード電極１２との間に１Ｖ～５Ｖ程度の電圧が印加され、電気化学反応器２０では、アノード電極２１とカソード電極２２との間に１Ｖ～８Ｖ程度の電圧が印加される。また、例えば、電気化学反応器１０の温度は７００℃～８００℃程度とされ、電気化学反応器２０の温度は８００℃程度とされる。 Here, the operation of the composite electrochemical reactor 1 according to the present embodiment will be described. For example, the electrochemical reactors 10 and 20 are used by being put in the tube 2 so that the anode electrode 11 and the cathode electrode 22 face each other with the separation membrane 30 interposed therebetween. In the electrochemical reactor 10, a voltage of about 1 V to 5 V is applied between the anode electrode 11 and the cathode electrode 12, and in the electrochemical reactor 20, about 1 V to 8 V is applied between the anode electrode 21 and the cathode electrode 22. Is applied. Further, for example, the temperature of the electrochemical reactor 10 is about 700 ° C. to 800 ° C., and the temperature of the electrochemical reactor 20 is about 800 ° C.
　カソード電極１２に向けてメタン（ＣＨ４）及び二酸化炭素（ＣＯ２）を含む原料ガスが供給されると、カソード電極１２において、（１１）式に示す二酸化炭素の還元反応が生じる。
　ＣＯ２＋２ｅ－→ＣＯ＋Ｏ２－・・・（１１） When a source gas containing methane (CH 4 ) and carbon dioxide (CO 2 ) is supplied toward the cathode electrode 12, a reduction reaction of carbon dioxide represented by the formula (11) occurs at the cathode electrode 12.
CO 2 + 2e − → CO + O 2− (11)
　この還元反応で生じた酸化物イオン（Ｏ２－）は一酸化炭素（ＣＯ）及びメタン（ＣＨ４）と共に電解質膜１３を透過し、アノード電極１１まで到達する。そして、酸化物イオン（Ｏ２－）及びメタン（ＣＨ４）がアノード電極１１に到達すると、アノード電極１１において、（１２）式に示すメタンの酸化反応が生じる。
　ＣＨ４＋Ｏ２－→ＣＯ＋２Ｈ２＋２ｅ－・・・（１２） Oxide ions (O 2− ) generated by this reduction reaction pass through the electrolyte membrane 13 together with carbon monoxide (CO) and methane (CH 4 ) and reach the anode electrode 11. When the oxide ions (O 2− ) and methane (CH 4 ) reach the anode electrode 11, an oxidation reaction of methane represented by the formula (12) occurs at the anode electrode 11.
CH 4 + O 2− → CO + 2H 2 + 2e − (12)
　（１１）式及び（１２）式より、電気化学反応器１０における全反応の反応式は、（１３）式で表わされる。
　ＣＯ２＋ＣＨ４→２Ｈ２＋２ＣＯ・・・（１３） From the equations (11) and (12), the reaction equation for all reactions in the electrochemical reactor 10 is represented by the equation (13).
CO 2 + CH 4 → 2H 2 + 2CO (13)
　このように、電気化学反応器１０により、二酸化炭素及びメタンから水素及び一酸化炭素が生成される。 Thus, the electrochemical reactor 10 generates hydrogen and carbon monoxide from carbon dioxide and methane.
　電気化学反応器１０により生成された水素及び一酸化炭素のうち水素は分離膜３０を透過するが、仕切り板３１を透過できず、例えば管２の外部に排出され、収集される。一方、一酸化炭素は分離膜３０を透過できないが、バイパス部３２を通じて電気化学反応器２０のカソード電極２２に供給される。 Among hydrogen and carbon monoxide generated by the electrochemical reactor 10, hydrogen permeates the separation membrane 30 but cannot permeate the partition plate 31. For example, it is discharged outside the tube 2 and collected. On the other hand, carbon monoxide cannot pass through the separation membrane 30 but is supplied to the cathode electrode 22 of the electrochemical reactor 20 through the bypass portion 32.
　カソード電極２２に向けて一酸化炭素が供給されると、カソード電極２２において、（２１）式、（２２）式に示す反応が生じる。
　Ｎｉ＋ＣＯ→ＮｉＯ＋Ｃ・・・（２１）
　ＮｉＯ＋２ｅ－→Ｎｉ＋Ｏ２－・・・（２２） When carbon monoxide is supplied toward the cathode electrode 22, reactions shown in the equations (21) and (22) occur at the cathode electrode 22.
Ni + CO → NiO + C (21)
NiO + 2e − → Ni + O 2− (22)
　従って、カソード電極２２では、（２３）式に示す一酸化炭素の還元反応が生じることとなる。
　ＣＯ＋２ｅ－→Ｃ＋Ｏ２－・・・（２３） Therefore, at the cathode electrode 22, the reduction reaction of carbon monoxide shown in the equation (23) occurs.
CO + 2e − → C + O 2− (23)
　この還元反応で生じた酸化物イオン（Ｏ２－）は電解質膜２３を透過し、アノード電極２１まで到達する。そして、酸化物イオン（Ｏ２－）がアノード電極２１に到達すると、アノード電極２１において、（２４）式、（２５）式に示す反応が生じる。
　２Ｏ２－→Ｏ２＋４ｅ－・・・（２４）
　Ｒｕ＋２Ｏ２－→ＲｕＯ２＋４ｅ－・・・（２５） Oxide ions (O 2− ) generated by this reduction reaction pass through the electrolyte membrane 23 and reach the anode electrode 21. When the oxide ions (O 2− ) reach the anode electrode 21, reactions shown in the formulas (24) and (25) occur in the anode electrode 21.
2O 2− → O 2 + 4e − (24)
Ru + 2O 2 - → RuO 2 + 4e - ··· (25)
　ここで、（２４）式の反応割合をｘ（０≦ｘ≦１）とすると、（２５）式の反応割合は（１－ｘ）となる。従って、反応割合ｘを考慮すると、（２４）式、（２５）式の反応は（２４´）式、（２５´）式で表わされる。アノード電極２１では、（２４´）式と（２５´）式との和より（２６）式に示す反応が生じることとなる。
　２ｘＯ２－→ｘＯ２＋４ｘｅ－・・・（２４´）
　（１－ｘ）Ｒｕ＋２（１－ｘ）Ｏ２－→（１－ｘ）ＲｕＯ２＋４（１－ｘ）ｅ－・・・（２５´）
　２Ｏ２－＋（１－ｘ）Ｒｕ→ｘＯ２＋（１－ｘ）ＲｕＯ２＋４ｅ－・・・（２６） Here, when the reaction ratio of the formula (24) is x (0 ≦ x ≦ 1), the reaction ratio of the formula (25) is (1−x). Therefore, when the reaction ratio x is taken into account, the reactions of the equations (24) and (25) are expressed by the equations (24 ′) and (25 ′). In the anode electrode 21, the reaction shown in the equation (26) occurs from the sum of the equations (24 ′) and (25 ′).
2xO 2- → xO 2 + 4xe - ··· (24')
(1-x) Ru + 2 (1-x) O 2- > (1-x) RuO 2 +4 (1-x) e − (25 ′)
2O 2- + (1-x) Ru → xO 2 + (1-x) RuO 2 + 4e − (26)
　（２３）式及び（２６）式より、電気化学反応器２０では、（２７）式に示す反応が生じる。
　２ＣＯ＋（１－ｘ）Ｒｕ→２Ｃ＋ｘＯ２＋（１－ｘ）ＲｕＯ２・・・（２７） From the equations (23) and (26), the reaction shown in the equation (27) occurs in the electrochemical reactor 20.
2CO + (1-x) Ru → 2C + xO 2 + (1-x) RuO 2 (27)
　このようにして、電気化学反応器２０を用いて酸素ガスを製造することができる。 In this way, oxygen gas can be produced using the electrochemical reactor 20.
　そして、電気化学反応器１０及び電気化学反応器２０を含む複合電気化学反応器１では、（２８）式に示す反応が生じる。
　ＣＯ２＋ＣＨ４→２Ｈ２＋２Ｃ＋Ｏ２・・・（２８） Then, in the composite electrochemical reactor 1 including the electrochemical reactor 10 and the electrochemical reactor 20, the reaction shown in the equation (28) occurs.
CO 2 + CH 4 → 2H 2 + 2C + O 2 (28)
　つまり、複合電気化学反応器１を用いれば、メタン及び二酸化炭素から水素及び酸素を製造することができる。例えば、水素は燃料電池の燃料に用いることができる。 That is, if the composite electrochemical reactor 1 is used, hydrogen and oxygen can be produced from methane and carbon dioxide. For example, hydrogen can be used as fuel for fuel cells.
　メタンとしては天然ガス及びバイオガス等に含まれたものを用いることができる。本実施形態は、バイオガスの利用に特に好適である。これは、バイオガスは５０体積％～７０体積％のメタン及び３０体積％～５０体積％の二酸化炭素を含有していることが多いからである。つまり、バイオガスはカソード電極２２に供給するメタンのみならず二酸化炭素をも含有しているからである。 As methane, those contained in natural gas and biogas can be used. This embodiment is particularly suitable for the use of biogas. This is because biogas often contains 50 volume% to 70 volume% methane and 30 volume% to 50 volume% carbon dioxide. That is, the biogas contains not only methane supplied to the cathode electrode 22 but also carbon dioxide.
　電気化学反応器２０は電気化学反応器１０から分離して用いることもできる。そして、電気化学反応器２０のカソード電極２２に向けて二酸化炭素が供給されると、カソード電極２２において、（３１）式、（３２）式に示す反応が生じる。
　Ｎｉ＋ＣＯ２→ＮｉＯ＋ＣＯ・・・（３１）
　ＮｉＯ＋２ｅ－→Ｎｉ＋Ｏ２－・・・（３２） The electrochemical reactor 20 can also be used separately from the electrochemical reactor 10. When carbon dioxide is supplied toward the cathode electrode 22 of the electrochemical reactor 20, the reactions shown in the equations (31) and (32) occur at the cathode electrode 22.
Ni + CO 2 → NiO + CO ··· (31)
NiO + 2e − → Ni + O 2− (32)
　従って、カソード電極２２では、（３３）式に示す二酸化炭素の還元反応が生じることとなる。
　ＣＯ２＋２ｅ－→ＣＯ＋Ｏ２－・・・（３３） Therefore, the cathode electrode 22 undergoes a carbon dioxide reduction reaction represented by the equation (33).
CO 2 + 2e − → CO + O 2− (33)
　二酸化炭素が供給された場合に、カソード電極２２において、（３４）式、（３５）式に示す反応が生じることもある。
　２Ｎｉ＋ＣＯ２→２ＮｉＯ＋Ｃ・・・（３４）
　２ＮｉＯ＋４ｅ－→２Ｎｉ＋２Ｏ２－・・・（３５） When carbon dioxide is supplied, the reactions shown in the equations (34) and (35) may occur at the cathode electrode 22.
2Ni + CO 2 → 2NiO + C (34)
2NiO + 4e − → 2Ni + 2O 2− (35)
　この場合、カソード電極２２では、（３６）式に示す二酸化炭素の還元反応が生じることとなる。
　ＣＯ２＋４ｅ－→Ｃ＋２Ｏ２－・・・（３６） In this case, the cathode electrode 22 undergoes a carbon dioxide reduction reaction represented by the equation (36).
CO 2 + 4e − → C + 2O 2− (36)
　ここで、（３３）式の反応割合をｙ（０≦ｙ≦１）とすると、（３６）式の反応割合は（１－ｙ）となる。従って、反応割合ｙを考慮すると、（３３）式、（３６）式の反応は（３３´）式、（３６´）式で表わされる。アノード電極２１では、（３３´）式と（３６´）式との和より（３７）式に示す反応が生じることとなる。
　ｙＣＯ２＋２ｙｅ－→ｙＣＯ＋ｙＯ２－・・・（３３´）
　（１－ｙ）ＣＯ２＋４（１－ｙ）ｅ－→（１－ｙ）Ｃ＋２（１－ｙ）Ｏ２－・・・（３６´）
　ＣＯ２＋２（２－ｙ）ｅ－→ｙＣＯ＋（１－ｙ）Ｃ＋（２－ｙ）Ｏ２－・・・（３７） Here, when the reaction rate of the formula (33) is y (0 ≦ y ≦ 1), the reaction rate of the formula (36) is (1-y). Therefore, when the reaction ratio y is taken into account, the reactions of the equations (33) and (36) are represented by the equations (33 ′) and (36 ′). In the anode electrode 21, the reaction shown in the equation (37) occurs from the sum of the equations (33 ′) and (36 ′).
yCO 2 + 2ye − → yCO + yO 2− (33 ′)
(1-y) CO 2 +4 (1-y) e − → (1-y) C + 2 (1-y) O 2− (36 ′)
CO 2 +2 (2-y) e − → yCO + (1-y) C + (2-y) O 2− (37)
　この還元反応で生じた酸化物イオン（Ｏ２－）は電解質膜２３を透過し、アノード電極２１まで到達する。そして、酸化物イオン（Ｏ２－）がアノード電極２１に到達すると、アノード電極２１において、（３８）式に示す反応が生じる。
　２Ｏ２－＋（１－ｘ）Ｒｕ→ｘＯ２＋（１－ｘ）ＲｕＯ２＋４ｅ－・・・（３８） Oxide ions (O 2− ) generated by this reduction reaction pass through the electrolyte membrane 23 and reach the anode electrode 21. When the oxide ions (O 2− ) reach the anode electrode 21, the reaction shown in the equation (38) occurs at the anode electrode 21.
2O 2 + (1-x) Ru → xO 2 + (1-x) RuO 2 + 4e − (38)
　（３７）式及び（３８）式より、電気化学反応器２０では、（３９）式に示す反応が生じる。
　２ＣＯ２＋（１－ｘ）（２－ｙ）Ｒｕ→２ｙＣＯ＋２（１－ｙ）Ｃ＋ｘ（２－ｙ）Ｏ２＋（１－ｘ）（２－ｙ）ＲｕＯ２・・・（３９） From the equations (37) and (38), the reaction shown in the equation (39) occurs in the electrochemical reactor 20.
2CO 2 + (1-x) (2-y) Ru → 2yCO + 2 (1-y) C + x (2-y) O 2 + (1-x) (2-y) RuO 2 (39)
　このようにして、電気化学反応器２０を用いて酸素ガスを製造することができる。 In this way, oxygen gas can be produced using the electrochemical reactor 20.
　次に、電気化学反応器２０を製造する方法について説明する。 Next, a method for manufacturing the electrochemical reactor 20 will be described.
　先ず、アノード電極２１用の粉体及びカソード電極２２用の粉体を作製する。図２は、アノード電極２１用の粉体を作製する方法を示す図であり、図３は、カソード電極２２用の粉体を作製する方法を示す図である。 First, powder for the anode electrode 21 and powder for the cathode electrode 22 are prepared. FIG. 2 is a diagram showing a method for producing a powder for the anode electrode 21, and FIG. 3 is a diagram showing a method for producing a powder for the cathode electrode 22.
　アノード電極２１用の粉体の作製では、図２に示すように、先ず、塩化ルテニウム水和物の粉体及びＹＳＺの粉体をルテニウム量に換算してＲｕ：ＹＳＺ＝３０：７０の体積比で混ぜ合わせる。次いで、この混合物の固体含有量が３０体積％になるように再蒸留水で分散させた懸濁液（サスペンション）を作製し、１３ＭのＮＨ４ＯＨ溶液を用いてサスペンションのｐＨを、例えば１０に調整する。その後、サスペンションの凍結乾燥を行い、８００℃で１時間の仮焼及び１０００℃で２時間の仮焼を空気中で行う。このようにして、アノード電極２１用の粉体としてＲｕＯ２－ＹＳＺ粉体が得られる。 In the preparation of the powder for the anode electrode 21, as shown in FIG. 2, first, the ruthenium chloride hydrate powder and the YSZ powder are converted to the ruthenium amount, and the volume ratio of Ru: YSZ = 30: 70. Mix with. Next, a suspension (suspension) dispersed with double-distilled water is prepared so that the solid content of the mixture is 30% by volume, and the pH of the suspension is adjusted to, for example, 10 using a 13M NH 4 OH solution. adjust. Thereafter, the suspension is freeze-dried and calcined at 800 ° C. for 1 hour and calcined at 1000 ° C. for 2 hours in air. In this way, RuO 2 —YSZ powder is obtained as the powder for the anode electrode 21.
　カソード電極２２用の粉体の作製では、図３に示すように、先ず、１．４Ｍの硝酸ニッケル六水和物水溶液にＹＳＺの粉体をニッケル量に換算してＮｉ：ＹＳＺ＝３０：７０の体積比で混ぜ合わせ、この混合物の懸濁液（サスペンション）を作製する。その後、サスペンションの凍結乾燥を行い、６００℃で１時間の仮焼及び１０００℃で２時間の仮焼を空気中で行う。このようにして、カソード電極２２用の粉体としてＮｉＯ－ＹＳＺ粉体が得られる。 In the preparation of the powder for the cathode electrode 22, as shown in FIG. 3, first, YSZ powder is converted into nickel amount in a 1.4M nickel nitrate hexahydrate aqueous solution, and Ni: YSZ = 30: 70. Are mixed at a volume ratio of 2 to prepare a suspension of the mixture. Thereafter, the suspension is freeze-dried and calcined at 600 ° C. for 1 hour and calcined at 1000 ° C. for 2 hours in air. In this way, NiO—YSZ powder is obtained as the powder for the cathode electrode 22.
　また、電解質膜２３を作製する。図４は電解質膜２３を作製する方法を示す図である。電解質膜２３の作製では、ＹＳＺの粉体を固体含有量が２０体積％になるように、トルエン及びイソプロパノールの混合溶液中に分散させて、懸濁液（サスペンション）を作製する。混合溶液におけるトルエンとイソプロパノールとの体積比は、例えば１：２とする。次いで、サスペンションに、粉体に対して９質量％のポリエチレングリコール（可塑剤）及び５質量％のポリビニルブチラール（結合剤）を加える。その後、サスペンションを２４時間、撹拌する。そして、撹拌後のサスペンションを用いてドクターブレード法によりＹＳＺ膜を形成する。ドクターブレード法によるＹＳＺ膜の形成では、例えば、前ブレードを８０μｍ、後ブレードを１５０μｍ、送り速度を５０ｍｍ／分、乾燥時間を１週間とする。 Also, the electrolyte membrane 23 is produced. FIG. 4 is a view showing a method for producing the electrolyte membrane 23. In the production of the electrolyte membrane 23, a suspension (suspension) is produced by dispersing YSZ powder in a mixed solution of toluene and isopropanol so that the solid content is 20% by volume. The volume ratio of toluene and isopropanol in the mixed solution is, for example, 1: 2. Next, 9% by mass of polyethylene glycol (plasticizer) and 5% by mass of polyvinyl butyral (binder) are added to the suspension. Thereafter, the suspension is stirred for 24 hours. Then, a YSZ film is formed by the doctor blade method using the suspension after stirring. In the formation of the YSZ film by the doctor blade method, for example, the front blade is 80 μm, the rear blade is 150 μm, the feed rate is 50 mm / min, and the drying time is one week.
　次に、アノード電極２１用の粉体、カソード電極２２用の粉体、及び電解質膜２３を一体化させる。図５は、アノード電極２１用の粉体、カソード電極２２用の粉体、及び電解質膜２３を一体化させる方法を示す図である。 Next, the powder for the anode electrode 21, the powder for the cathode electrode 22, and the electrolyte membrane 23 are integrated. FIG. 5 is a diagram showing a method for integrating the powder for the anode electrode 21, the powder for the cathode electrode 22, and the electrolyte membrane 23.
　先ず、電解質膜２３とカソード電極２２用のＮｉＯ－ＹＳＺ粉体とを互いに積層し、５０ＭＰａで１分間の一軸加圧成形及び１００ＭＰａで１分間の等方加圧成形によりペレット状の積層体を作製する。次いで、積層体を空気中、１４００℃で４時間、共焼結して共焼結体を作製する。その後、アノード電極２１用のＲｕＯ２－ＹＳＺ粉体を９０体積％エタノール－１０体積％ポリエチレングリコール混合溶液中に固体含有量が１５体積％となるように分散させてサスペンションを作製し、このサスペンションを共焼結体の電解質膜２３の表面にスクリーン印刷する。続いて、９００℃で１時間、焼き付けを行う。このようにして、アノード電極２１、カソード電極２２及び電解質膜２３を備えた電気化学反応器２０を製造することができる。 First, the electrolyte membrane 23 and the NiO—YSZ powder for the cathode electrode 22 are laminated together, and a pellet-like laminate is produced by uniaxial pressing at 50 MPa for 1 minute and isotropic pressing at 100 MPa for 1 minute. To do. Next, the laminate is co-sintered in air at 1400 ° C. for 4 hours to produce a co-sintered body. Thereafter, a suspension was prepared by dispersing RuO 2 -YSZ powder for the anode electrode 21 in a 90 volume% ethanol-10 volume% polyethylene glycol mixed solution so that the solid content was 15 volume%. Screen printing is performed on the surface of the electrolyte film 23 of the co-sintered body. Subsequently, baking is performed at 900 ° C. for 1 hour. Thus, the electrochemical reactor 20 provided with the anode electrode 21, the cathode electrode 22, and the electrolyte membrane 23 can be manufactured.
　次に、本発明者らが行った実験について説明する。 Next, the experiment conducted by the inventors will be described.
　（第１の実験）
　第１の実験では、図６に示すように、上記の実施形態と同様の構成の電気化学反応器２０を有する電気化学システムを構築し、この電気化学システムを用いて電気化学反応器２０の特性の調査を行った。ここでは、ＹＳＺの粉体として、東ソー株式会社製の純度が９９．９質量％超の８ｍｏｌ％Ｙ２Ｏ３－９２ｍｏｌ％ＺｒＯ２（Ｙ０．１５Ｚｒ０．８５Ｏ１．９３）の粉体を用いた。 (First experiment)
In the first experiment, as shown in FIG. 6, an electrochemical system having an electrochemical reactor 20 having the same configuration as that of the above embodiment is constructed, and the characteristics of the electrochemical reactor 20 are obtained using this electrochemical system. Was conducted. Here, as a powder of YSZ, a powder of 8 mol% Y 2 O 3 -92 mol% ZrO 2 (Y 0.15 Zr 0.85 O 1.93 ) having a purity of more than 99.9 mass% manufactured by Tosoh Corporation Using the body.
　電気化学反応器２０は、上記の実施形態と同様の方法で作製した。そして、ガラスシール１２３を介して電気化学反応器２０をアルミナホルダ１２１及び１２２内に挿入した。なお、アルミナホルダ１２１及び１２２の間にガラスリング１２４を介在させた。アルミナホルダ１２１の下端にガラスシール１２５を介して磁製管１２７を繋ぎ、アルミナホルダ１２２の上端にガラスシール１２６を介して磁製管１２９を繋いだ。また、アルミナホルダ１２１の下端にガスが通流する開口部を設け、アルミナホルダ１２２の上端にもガスが通流する開口部を設けた。そして、これら開口部を介して、直流電源１３１に接続された白金線１３３、及び電流計１３２に接続された白金線１３４を、アノード電極２１及びカソード電極２２に接続した。なお、アノード電極２１への白金線１３３及び１３４の接続には白金メッシュ１３６及び白金ペーストを用い、カソード電極２２への白金線１３３及び１３４の接続には白金メッシュ１３５及び白金ペーストを用いた。磁製管１２７の内側の空間を二分する磁製管１２８を設け、磁製管１２９の内側の空間を二分する磁製管１３０を設けた。 The electrochemical reactor 20 was produced by the same method as in the above embodiment. Then, the electrochemical reactor 20 was inserted into the alumina holders 121 and 122 through the glass seal 123. A glass ring 124 was interposed between the alumina holders 121 and 122. A magnetic tube 127 was connected to the lower end of the alumina holder 121 via a glass seal 125, and a magnetic tube 129 was connected to the upper end of the alumina holder 122 via a glass seal 126. An opening through which gas flows is provided at the lower end of the alumina holder 121, and an opening through which gas flows is provided at the upper end of the alumina holder 122. The platinum wire 133 connected to the DC power source 131 and the platinum wire 134 connected to the ammeter 132 were connected to the anode electrode 21 and the cathode electrode 22 through these openings. Note that platinum mesh 136 and platinum paste were used to connect the platinum wires 133 and 134 to the anode electrode 21, and platinum mesh 135 and platinum paste were used to connect the platinum wires 133 and 134 to the cathode electrode 22. A magnetic tube 128 that bisects the space inside the magnetic tube 127 is provided, and a magnetic tube 130 that bisects the space inside the magnetic tube 129 is provided.
　アルミナホルダ１２１及び１２２並びに磁製管１２７～１３０には、株式会社ニッカトー製のＨＢ（成分：４０．６質量％ＳｉＯ２、５６．２質量％Ａｌ２Ｏ３、０．２質量％ＴｉＯ２、０．５質量％Ｆｅ２Ｏ３、０．２質量％ＣａＯ、０．１質量％ＭｇＯ、０．５質量％Ｎａ２Ｏ、１．７質量％Ｋ２Ｏ）を用いた。そして、電気化学システムの組み立てに当たっては、電気化学反応器２０とアルミナホルダ１２１及び１２２並びに磁製管１２７～１３０との封着のために、８７０℃に１５分間保持した。その後、カソード電極２２内の酸化ニッケル及びアノード電極２１内の酸化ルテニウムを還元するために、８００℃まで降温した後に、カソード電極２２側及びアノード電極２１側に水を含ませた水素（９７体積％Ｈ２、３体積％Ｈ２Ｏ）を１００ｍｌ／分で供給し、２４時間、保持した。還元の後、電気化学反応器２０の内部に残留しているＨ２を除去するためにＡｒを１００ｍｌ／分で１時間供給した。 The alumina holders 121 and 122 and the magnetic tubes 127 to 130 include HB (component: 40.6% by mass SiO 2 , 56.2% by mass Al 2 O 3 , 0.2% by mass TiO 2 , manufactured by Nikkato Co., Ltd. 0.5 wt% Fe 2 O 3, 0.2 wt% CaO, 0.1 wt% MgO, 0.5 wt% Na 2 O, with 1.7 wt% K 2 O). In assembling the electrochemical system, the electrochemical reactor 20, the alumina holders 121 and 122, and the magnetic tubes 127 to 130 were kept at 870 ° C. for 15 minutes. Thereafter, in order to reduce nickel oxide in the cathode electrode 22 and ruthenium oxide in the anode electrode 21, the temperature was lowered to 800 ° C., and then hydrogen (97 vol%) containing water on the cathode electrode 22 side and the anode electrode 21 side was used. H 2 , 3% by volume H 2 O) was fed at 100 ml / min and held for 24 hours. After the reduction, Ar was supplied at 100 ml / min for 1 hour in order to remove H 2 remaining in the electrochemical reactor 20.
　そして、８００℃で、１０体積％ＣＯ－９０体積％Ａｒガスを磁製管１２８の内側を通じて５ｍｌ／分でカソード電極２２に供給し、Ａｒガスを磁製管１３０の内側を通じて２０ｍｌ／分でアノード電極２１に供給した。また、直流電源１３１によりアノード電極２１とカソード電極２２との間に１．０Ｖ～８．０Ｖの電圧を印加し、磁製管１２７と磁製管１２８との間を通じて排出されるガスの組成、磁製管１２９と磁製管１３０との間を通じて排出されるガスの組成をガスクロマトグラフィーで分析した。 Then, at 800 ° C., 10 vol% CO-90 vol% Ar gas is supplied to the cathode electrode 22 through the inside of the magnetic tube 128 at 5 ml / min, and Ar gas is supplied through the inside of the magnetic tube 130 to the anode at 20 ml / min. The electrode 21 was supplied. In addition, a composition of gas exhausted between the magnetic tube 127 and the magnetic tube 128 by applying a voltage of 1.0 V to 8.0 V between the anode electrode 21 and the cathode electrode 22 by the DC power supply 131, The composition of the gas exhausted between the magnetic tube 129 and the magnetic tube 130 was analyzed by gas chromatography.
　この結果を図７に示す。図７中の縦軸はＣＯ分解率を示している。ＣＯ分解率は、ＣＯの分解反応（２ＣＯ→２Ｃ＋Ｏ２）に由来するアノード電極２１でのＯ２ガスの生成量から求めた。印加電圧が１．０Ｖの場合のＣＯ分解率は、９％～１５％であった。一方、印加電圧を２．０Ｖ以上に増加させると、分解率は急激に増加し、ばらつきはあるものの長時間にわたり６７％～１００％に達した。電気化学反応器２０を流れた電流は印加電圧に依らず検出限界値の１．１Ａを示したが、実際には印加電圧の増加と共に電流も増加していると考えられる。 The result is shown in FIG. The vertical axis in FIG. 7 indicates the CO decomposition rate. The CO decomposition rate was determined from the amount of O 2 gas generated at the anode electrode 21 derived from the CO decomposition reaction (2CO → 2C + O 2 ). The CO decomposition rate when the applied voltage was 1.0 V was 9% to 15%. On the other hand, when the applied voltage was increased to 2.0 V or more, the decomposition rate increased rapidly and reached 67% to 100% over a long period of time, although there was variation. The current flowing through the electrochemical reactor 20 showed a detection limit value of 1.1 A regardless of the applied voltage, but in reality, it is considered that the current increases as the applied voltage increases.
　この分解実験を行った後には、カソード電極２２の表面及びアノード電極２１の表面のＸ線回折分析を行った。この結果を図８に示す。図８（ａ）はカソード電極２２の表面の分析結果を示し、図８（ｂ）はアノード電極２１の表面の分析結果を示す。カソード電極２２には、ＹＳＺ、Ｎｉ及びＰｔの存在が確認された。アノード電極２１には、ＹＳＺ、Ｒｕ、ＲｕＯ２及びＰｔの存在が確認された。輸送された一部のＯ２－イオンによって、ＲｕがＲｕＯ２へ酸化されたことが分かる。また、カソード電極２２の断面を電子線プローブマイクロアナライザーで測定したところ、平均で４．７６質量％（表面近傍で０．３１５重量％、中央で１．６７重量％、電解質膜との界面近傍で１２．３０重量％）の炭素の析出が確認された。 After performing this decomposition experiment, X-ray diffraction analysis of the surface of the cathode electrode 22 and the surface of the anode electrode 21 was performed. The result is shown in FIG. FIG. 8A shows the analysis result of the surface of the cathode electrode 22, and FIG. 8B shows the analysis result of the surface of the anode electrode 21. The presence of YSZ, Ni and Pt was confirmed in the cathode electrode 22. The anode electrode 21, YSZ, Ru, presence of RuO 2 and Pt was confirmed. It can be seen that Ru was oxidized to RuO 2 by a part of the transported O 2− ions. Further, when the cross section of the cathode electrode 22 was measured with an electron beam probe microanalyzer, it averaged 4.76% by mass (0.315% by weight near the surface, 1.67% by weight at the center, near the interface with the electrolyte membrane). 12.30% by weight) of carbon was observed.
　以上の実験結果より、上記の（２１）式～（２７）式の反応が生じていることが裏付けられた。すなわち、ＣＯがＮｉ及びＲｕと電気化学的に反応し、その結果、Ｃ、Ｏ２、及びＲｕＯ２が生成された。なお、図７のＣＯ分解率は反応割合ｘが１の場合に相当する値である。 From the above experimental results, it was confirmed that the reactions of the above formulas (21) to (27) occurred. That is, CO reacted electrochemically with Ni and Ru, resulting in C, O 2 , and RuO 2 . The CO decomposition rate in FIG. 7 is a value corresponding to the case where the reaction ratio x is 1.
　（第２の実験）
　第２の実験では、第１の実験で用いた電気化学システムと同様のものを作製した。そして、８００℃で、ＣＯ２ガスを磁製管１２８の内側を通じて５ｍｌ／分でカソード電極２２に供給し、Ａｒガスを磁製管１３０の内側を通じて２０ｍｌ／分でアノード電極２１に供給した。また、直流電源１３１によりアノード電極２１とカソード電極２２との間に１．０Ｖ～８．０Ｖの電圧を印加し、磁製管１２７と磁製管１２８との間を通じて排出されるガスの組成、磁製管１２９と磁製管１３０との間を通じて排出されるガスの組成をガスクロマトグラフィーで分析した。 (Second experiment)
In the second experiment, the same electrochemical system used in the first experiment was produced. Then, at 800 ° C., CO 2 gas was supplied to the cathode electrode 22 through the inside of the magnetic tube 128 at 5 ml / min, and Ar gas was supplied to the anode electrode 21 through the inside of the magnetic tube 130 at 20 ml / min. In addition, a composition of gas exhausted between the magnetic tube 127 and the magnetic tube 128 by applying a voltage of 1.0 V to 8.0 V between the anode electrode 21 and the cathode electrode 22 by the DC power supply 131, The composition of the gas exhausted between the magnetic tube 129 and the magnetic tube 130 was analyzed by gas chromatography.
　この結果を図９に示す。図９（ａ）はカソード電極２２側のガスの割合を示し、図９（ｂ）はアノード電極２１側のガスの割合を示す。カソード電極２２側では、ＣＯ２の割合が９２％～９４％程度であった。つまり、ＣＯ２の割合が６％～８％程度減少し、ＣＯガスの割合が６％～８％程度増加していた。この傾向は印加電圧に依存しなかった。アノード電極２１側でのＯ２ガス割合は２％～９％であった。これらの結果は、ＣＯ２がＣＯ及びＯ２に分解したことを示している。つまり、「ＣＯ２→ＣＯ＋１／２Ｏ２」で表される反応が生じたことを示している。また、ＣＯ２の分解で生成したＣＯガス及びＯ２ガスが完全に分離されたことも示している。電気化学反応器２０を流れた電流は印加電圧に依らず検出限界値の１．１Ａを示したが、実際には印加電圧の増加と共に電流も増加していると考えられる。 The result is shown in FIG. FIG. 9A shows the ratio of gas on the cathode electrode 22 side, and FIG. 9B shows the ratio of gas on the anode electrode 21 side. The cathode electrode 22 side, the ratio of CO 2 was about 92% to 94%. That is, the ratio of CO 2 decreased by about 6% to 8%, and the ratio of CO gas increased by about 6% to 8%. This tendency did not depend on the applied voltage. The O 2 gas ratio on the anode electrode 21 side was 2% to 9%. These results indicate that CO 2 was decomposed into CO and O 2 . That is, the reaction represented by “CO 2 → CO + 1 / 2O 2 ” occurred. It also shows that the CO gas and O 2 gas produced by the decomposition of CO 2 are completely separated. The current flowing through the electrochemical reactor 20 showed a detection limit value of 1.1 A regardless of the applied voltage, but in reality, it is considered that the current increases as the applied voltage increases.
　この分解実験を行った後には、カソード電極２２の表面及びアノード電極２１の表面のＸ線回折分析を行った。この結果、カソード電極２２には、ＹＳＺ、Ｎｉ及びＰｔの存在が確認された。アノード電極２１には、ＹＳＺ、Ｒｕ、ＲｕＯ２及びＰｔの存在が確認された。輸送された一部のＯ２－イオンによって、ＲｕがＲｕＯ２へ酸化されたことが分かる。また、カソード電極２２の断面を電子線プローブマイクロアナライザーで測定したところ、平均で１．１６質量％（表面近傍で１．２４重量％、中央で０．７１１重量％、電解質膜との界面近傍で１．５５重量％）の炭素の析出が確認された。 After performing this decomposition experiment, X-ray diffraction analysis of the surface of the cathode electrode 22 and the surface of the anode electrode 21 was performed. As a result, the presence of YSZ, Ni, and Pt was confirmed in the cathode electrode 22. The anode electrode 21 was confirmed to contain YSZ, Ru, RuO 2 and Pt. It can be seen that Ru was oxidized to RuO 2 by a part of the transported O 2− ions. Further, when the cross section of the cathode electrode 22 was measured with an electron beam probe microanalyzer, the average was 1.16% by mass (1.24% by weight near the surface, 0.711% by weight at the center, and near the interface with the electrolyte membrane). 1.55% by weight) of carbon was observed.
　ここで、ＣＯ２のカソード電極２２での反応について考察する。カソード電極２２で生じると考えられる反応として（４１）式と（４２）式の反応が挙げられる。
　ＣＯ２→ＣＯ＋１／２Ｏ２・・・（４１）
　ＣＯ２→Ｃ＋Ｏ２・・・（４２） Here, the reaction of CO 2 at the cathode electrode 22 will be considered. Reactions considered to occur at the cathode electrode 22 include reactions of the formulas (41) and (42).
CO 2 → CO + 1 / 2O 2 (41)
CO 2 → C + O 2 (42)
　これら各式の反応割合をそれぞれｓ、ｔとすると、未反応のＣＯ２の割合は「１－ｓ－ｔ」、生成したＣＯの割合は「ｓ」、生成したＯ２の割合は「ｓ／２＋ｔ」と表せる。また、（４３）式と（４４）式の定義をすると、（４５）式と（４６）式が得られる。
　［ＣＯ］／（［ＣＯ２］＋［ＣＯ］）＝ｓ／（１－ｔ）＝Ａ・・・（４３）
　［Ｏ２］／（［Ａｒ］＋［Ｏ２］）＝ｓ／２＋ｔ＝Ｂ・・・（４４）
　ｓ＝２Ａ（Ｂ－１）／（Ａ－２）・・・（４５）
　ｔ＝（Ａ－２Ｂ）／（Ａ－２）・・・（４６） When the reaction ratios of these formulas are s and t, respectively, the ratio of unreacted CO 2 is “1-st”, the ratio of generated CO is “s”, and the ratio of generated O 2 is “s / t”. 2 + t ”. Further, when the expressions (43) and (44) are defined, the expressions (45) and (46) are obtained.
[CO] / ([CO 2 ] + [CO]) = s / (1-t) = A (43)
[O 2 ] / ([Ar] + [O 2 ]) = s / 2 + t = B (44)
s = 2A (B-1) / (A-2) (45)
t = (A-2B) / (A-2) (46)
　これらの式に図９に示す結果から得られる値を代入すると、ｓの値は６．５～７．３％であり、１．０－８．０Ｖの印加電圧に無関係であった。ｔの値は１．０Ｖでほぼ０％であり、２．０－８．０Ｖの範囲で約３%に増加した。以上の実験結果より、ＣＯの生成が１．０－８．０Ｖの電圧範囲で支配的な反応である。一方で、炭素析出には１．０Ｖより大きな電圧が必要である。 When the values obtained from the results shown in FIG. 9 were substituted into these equations, the value of s was 6.5 to 7.3%, which was unrelated to the applied voltage of 1.0 to 8.0V. The value of t was almost 0% at 1.0V, and increased to about 3% in the range of 2.0-8.0V. From the above experimental results, the production of CO is a dominant reaction in the voltage range of 1.0-8.0V. On the other hand, a voltage greater than 1.0 V is required for carbon deposition.
　（第３の実験）
　第３の実験では、第１の実験で用いた電気化学システムと同様のものを作製した。そして、８００℃で、１０体積％ＣＯ－９０体積％Ａｒガス及びＣＯ２ガスを磁製管１２８の内側を通じて５０ｍｌ／分でカソード電極２２に供給し、Ａｒガスを磁製管１３０の内側を通じて２０ｍｌ／分でアノード電極２１に供給した。また、直流電源１３１によりアノード電極２１とカソード電極２２との間に８．０Ｖの電圧を印加し、磁製管１２７と磁製管１２８との間を通じて排出されるガスの組成、磁製管１２９と磁製管１３０との間を通じて排出されるガスの組成をガスクロマトグラフィーで分析した。なお、混合ガス中のＣＯガスの割合を２５体積％、５０体積％、７５体積％の順に変化させた。 (Third experiment)
In the third experiment, the same electrochemical system used in the first experiment was produced. Then, at 800 ° C., 10 vol% CO-90 vol% Ar gas and CO 2 gas are supplied to the cathode electrode 22 through the inside of the magnetic tube 128 at 50 ml / min, and Ar gas is 20 ml through the inside of the magnetic tube 130. / Min. To the anode electrode 21. In addition, a voltage of 8.0 V is applied between the anode electrode 21 and the cathode electrode 22 by the DC power supply 131, and the composition of the gas discharged through the gap between the magnetic tube 127 and the magnetic tube 128, the magnetic tube 129. The composition of the gas exhausted between the ceramic tube 130 and the porcelain tube 130 was analyzed by gas chromatography. In addition, the ratio of CO gas in mixed gas was changed in order of 25 volume%, 50 volume%, and 75 volume%.
　この結果を図１０に示す。図１０（ａ）はカソード電極２２側のガスの割合を示し、図１０（ｂ）はアノード電極２１側のガスの割合を示す。アノード電極２１側では、２％～１０％のＯ２ガスが検出された。ＣＯガスの割合を２５体積％、７５体積％とした場合にカソード電極２２側の出口ガスの組成が供給ガスの組成に近かった。一方、ＣＯガスの割合を５０％とした場合には、カソード電極２２側の出口ガスのＣＯガスの濃度が増加し、ＣＯ２ガスの濃度が減少した。電気化学反応器２０を流れた電流は印加電圧に依らず検出限界値の１．１Ａを示したが、実際には印加電圧の増加と共に電流も増加していると考えられる。 The result is shown in FIG. 10A shows the ratio of gas on the cathode electrode 22 side, and FIG. 10B shows the ratio of gas on the anode electrode 21 side. On the anode electrode 21 side, 2% to 10% of O 2 gas was detected. When the CO gas ratio was 25% by volume and 75% by volume, the composition of the outlet gas on the cathode electrode 22 side was close to the composition of the supply gas. On the other hand, when the proportion of CO gas was 50%, the concentration of CO gas in the outlet gas on the cathode electrode 22 side increased and the concentration of CO 2 gas decreased. The current flowing through the electrochemical reactor 20 showed a detection limit value of 1.1 A regardless of the applied voltage, but in reality, it is considered that the current increases as the applied voltage increases.
　この分解実験を行った後には、カソード電極２２の表面及びアノード電極２１の表面のＸ線回折分析を行った。カソード電極２２には、ＹＳＺ、Ｎｉ及びＰｔの存在が確認された。アノード電極２１には、ＹＳＺ、ＲｕＯ２及びＰｔの存在が確認された。輸送された一部のＯ２－イオンによって、ＲｕがＲｕＯ２へ酸化されたことが分かる。また、カソード電極２２の断面を電子線プローブマイクロアナライザーで測定したところ、平均で０．１８５質量％（表面で０．１３１重量％、中央で０．２３４重量％、電解質膜との界面近傍で０．１９０重量％）の炭素の析出が確認された。 After performing this decomposition experiment, X-ray diffraction analysis of the surface of the cathode electrode 22 and the surface of the anode electrode 21 was performed. The presence of YSZ, Ni and Pt was confirmed in the cathode electrode 22. The presence of YSZ, RuO 2 and Pt was confirmed in the anode electrode 21. It can be seen that Ru was oxidized to RuO 2 by a part of the transported O 2− ions. Further, when the cross section of the cathode electrode 22 was measured with an electron beam probe microanalyzer, the average was 0.185% by mass (0.131% by weight on the surface, 0.234% by weight at the center, and 0 near the interface with the electrolyte membrane). .190% by weight) of carbon was confirmed.
　ここで、ＣＯ及びＣＯ２のカソード電極２２での反応について考察する。カソード電極２２で生じると考えられる反応として（４７）式～（５０）式の反応が挙げられる。
　ＣＯ２→ＣＯ＋１／２Ｏ２・・・（４７）
　ＣＯ２→Ｃ＋Ｏ２・・・（４８）
　ＣＯ２＋Ｃ→２ＣＯ・・・（４９）
　ＣＯ→Ｃ＋１／２Ｏ２・・・（５０） Here, the reaction of CO and CO 2 at the cathode electrode 22 will be considered. Reactions considered to occur at the cathode electrode 22 include reactions of the formulas (47) to (50).
CO 2 → CO + 1 / 2O 2 (47)
CO 2 → C + O 2 (48)
CO 2 + C → 2CO (49)
CO → C + 1 / 2O 2 (50)
　これら各式の反応割合をそれぞれｓ、ｔ、ｕ、ｖとし、供給したＣＯの組成をＡ、供給したＣＯ２の組成をＢとすると、ＣＯ、ＣＯ２、Ｏ２の出口ガス割合は（５１）、（５２）、（５３）式でそれぞれ表せる。
　ｆ(ＣＯ)＝Ｂ（１－ｓ－ｔ－ｕ）／（Ａ（１－ｖ）＋Ｂ（１－ｔ－ｕ））・・・（５１）
　ｆ(ＣＯ２)＝（Ａ（１－ｖ）＋Ｂ（ｓ＋２ｕ））／（Ａ（１－ｖ）＋Ｂ（１－ｔ－ｕ））・・・（５２）
　ｆ(Ｏ２)＝Ｂ（ｓ／２＋ｔ）＋Ａｖ／２・・・（５３） Assuming that the reaction ratios of these formulas are s, t, u, and v, the supplied CO composition is A, and the supplied CO 2 composition is B, the outlet gas ratio of CO, CO 2 , and O 2 is (51 ), (52), and (53).
f (CO) = B (1−s−t−u) / (A (1−v) + B (1−t−u)) (51)
f (CO 2 ) = (A (1-v) + B (s + 2u)) / (A (1-v) + B (1-tu)) (52)
f (O 2 ) = B (s / 2 + t) + Av / 2 (53)
　ここで、測定された炭素析出量が小さいことから、ｕ＝Ａｖ／Ｂを仮定した。また、前述のＣＯ２分解実験に基づき、ｓ～０．０７，ｔ～０．０３を用いる。図１１は（ａ）ＣＯの分解率（ｖ）及び（ｂ）カソード側の出口ガス割合の計算値を示す。（５１）と（５２）式による計算値は実験結果を説明する。７５％ＣＯ２混合ガスを供給したとき、ｖ値は０％であった。ＣＯ２に富む混合ガスでは、ＣＯ２の分解がＣＯの分解に比べて優勢であることを示している（（４７）と（４８）式）。計算されたＣＯ２含有量は測定値より約７％低かった。５０％ＣＯ－５０％ＣＯ２混合ガスでは、ｖ値は０．０６－０．１８に増加した。これはＣＯの分解が促進されたことを示している（（５０）式）。生成した炭素は再びＣＯ２により酸化され、ＣＯを生成する（（４９）式）。結果として、ＣＯの出口ガス割合は増加する。計算結果は上記のＣＯとＣＯ２ガスの分解機構を反映し、測定されたＣＯとＣＯ２の出口ガス割合を説明する。７５％ＣＯ－２５％ＣＯ２混合ガスでは、ｖ値は０．１５となり、ほぼ一定であった。ＣＯとＣＯ２の出口ガス割合はそれぞれ８９％と１１％と計算された。しかしながら、測定されたＣＯの出口ガス割合（～７７％）は計算値よりも小さかった。この結果は、ＣＯに富む混合ガスではＣＯ２の分解（（４７）と（４８）式）が抑制されることを示す。混合されたＣＯ２ガスの一部は（４９）式の析出した炭素との反応に消費される。以上の反応機構のために、ＣＯ２の出口ガス割合は計算値より増加する。 Here, since the measured carbon deposition amount was small, u = Av / B was assumed. Further, s˜0.07, t˜0.03 are used based on the above-mentioned CO 2 decomposition experiment. FIG. 11 shows calculated values of (a) CO decomposition rate (v) and (b) cathode side outlet gas ratio. The calculated values according to equations (51) and (52) explain the experimental results. When 75% CO 2 gas mixture was supplied, the v value was 0%. In a mixed gas rich in CO 2, indicating that decomposition of CO 2 is dominant in comparison with the degradation of the CO ((47) and (48) below). The calculated CO 2 content was about 7% lower than the measured value. With 50% CO-50% CO 2 gas mixture, the v value increased to 0.06-0.18. This indicates that the decomposition of CO was promoted (Equation (50)). The generated carbon is oxidized again by CO 2 to generate CO (formula (49)). As a result, the CO outlet gas ratio increases. The calculation results reflect the above-described decomposition mechanism of CO and CO 2 gas, and explain the measured outlet gas ratio of CO and CO 2 . In the 75% CO-25% CO 2 mixed gas, the v value was 0.15, which was almost constant. The CO and CO 2 outlet gas ratios were calculated to be 89% and 11%, respectively. However, the measured CO outlet gas ratio (˜77%) was smaller than the calculated value. This result shows that CO 2 decomposition (equations (47) and (48)) is suppressed in the gas mixture rich in CO. A part of the mixed CO 2 gas is consumed for the reaction with the precipitated carbon of the formula (49). Due to the above reaction mechanism, the outlet gas ratio of CO 2 increases from the calculated value.
　図１２は（４９）式の反応に対する標準ギブス自由エネルギの値を示している。標準ギブス自由エネルギが実験温度（８００℃）において負であり、このことは、（４９）式の反応が熱力学的にも進行することを裏付けている。 FIG. 12 shows the standard Gibbs free energy value for the reaction of equation (49). The standard Gibbs free energy is negative at the experimental temperature (800 ° C.), which confirms that the reaction of equation (49) proceeds thermodynamically.
　図１３は析出したＣと実験に使用したガス量との関係を示すグラフである。電子線プローブアナライザーの分析結果で確認された析出炭素量を、実験で使用したＣＯ又はＣＯ２全ガス量で除すると供給ガス１ｍｌに対する炭素析出量が導出できる。図１３に示す結果から、ＣＯ分解の炭素析出量はＣＯ２分解の炭素析出量と比べて２１．６倍高いといえる。また、ＣＯ及びＣＯ２混合ガス分解の炭素析出量はＣＯ２単体のときとほぼ同程度の量である。これは、ＣＯから析出したＣがＣＯ２と反応し、ＣＯへ変化するためである。 FIG. 13 is a graph showing the relationship between precipitated C and the amount of gas used in the experiment. By dividing the amount of deposited carbon confirmed by the analysis result of the electron beam probe analyzer by the total amount of CO or CO 2 used in the experiment, the amount of deposited carbon with respect to 1 ml of the supply gas can be derived. From the results shown in FIG. 13, it can be said that the carbon deposition amount of CO decomposition is 21.6 times higher than the carbon deposition amount of CO 2 decomposition. Further, the amount of carbon deposited in the CO and CO 2 mixed gas decomposition is almost the same as that of CO 2 alone. This is because C precipitated from CO reacts with CO 2 and changes to CO.
　なお、上記実施形態は、何れも本発明を実施するにあたっての具体化の例を示したものに過ぎず、これらによって本発明の技術的範囲が限定的に解釈されてはならないものである。すなわち、本発明はその技術思想、又はその主要な特徴から逸脱することなく、様々な形で実施することができる。 It should be noted that each of the above-described embodiments is merely a specific example for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.
　本発明は、例えば、電気化学反応器に関連する産業に利用することができる。 The present invention can be used, for example, in industries related to electrochemical reactors.

Claims (3)

  1. 　ルテニウム及びイットリア安定化ジルコニアを含有するアノード電極と、
    　ニッケル及びイットリア安定化ジルコニアを含有するカソード電極と、
    　前記アノード電極と前記カソード電極との間に設けられ、イットリア安定化ジルコニアを含有し、酸化物イオンを透過させ、一酸化炭素の透過を妨げる電解質膜と、
    　を有することを特徴とする電気化学反応器。     An anode electrode containing ruthenium and yttria stabilized zirconia;
    A cathode electrode containing nickel and yttria stabilized zirconia;
    An electrolyte membrane provided between the anode electrode and the cathode electrode, containing yttria-stabilized zirconia, allowing the oxide ions to pass therethrough and preventing the permeation of carbon monoxide;
    An electrochemical reactor comprising:
  2. 　メタン及び二酸化炭素から水素及び一酸化炭素を生成する第１の電気化学反応器と、
    　前記第１の電気化学反応器により生成された一酸化炭素から酸素を生成する第２の電気化学反応器と、
    　を有し、
    　前記第２の電気化学反応器は、
    　ルテニウム及びイットリア安定化ジルコニアを含有するアノード電極と、
    　ニッケル及びイットリア安定化ジルコニアを含有するカソード電極と、
    　前記アノード電極と前記カソード電極との間に設けられ、イットリア安定化ジルコニアを含有し、酸化物イオンを透過させ、一酸化炭素の透過を妨げる電解質膜と、
    　を有することを特徴とする複合電気化学反応器。     A first electrochemical reactor that produces hydrogen and carbon monoxide from methane and carbon dioxide;
    A second electrochemical reactor for producing oxygen from carbon monoxide produced by the first electrochemical reactor;
    Have
    The second electrochemical reactor comprises:
    An anode electrode containing ruthenium and yttria stabilized zirconia;
    A cathode electrode containing nickel and yttria stabilized zirconia;
    An electrolyte membrane provided between the anode electrode and the cathode electrode, containing yttria-stabilized zirconia, allowing the oxide ions to pass therethrough and preventing the permeation of carbon monoxide;
    A composite electrochemical reactor characterized by comprising:
  3. 　前記第１の電気化学反応器と前記第２の電気化学反応器との間に設けられ、前記第１の電気化学反応器により生成された水素及び一酸化炭素を互いに分離する分離膜を有することを特徴とする請求項２に記載の複合電気化学反応器。 A separation membrane provided between the first electrochemical reactor and the second electrochemical reactor and configured to separate hydrogen and carbon monoxide generated by the first electrochemical reactor from each other; The composite electrochemical reactor according to claim 2.
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