Method for producing ethylene, carbon dioxide reduction electrode, and carbon dioxide reduction device

Abstract

To provide a method for producing ethylene, a carbon dioxide reduction electrode, and a carbon dioxide reduction device, each having high ethylene selectivity.SOLUTION: The present invention provides a method for producing ethylene, a carbon dioxide reduction electrode, and a carbon dioxide reduction device, comprising a step of reacting carbon dioxide and water in the presence of a multinuclear copper complex, for example, represented by the following formula (1).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for producing ethylene, a carbon dioxide reduction electrode, and a carbon dioxide reduction device. [Background technology]

[0002] In a method for producing ethylene by reducing carbon dioxide, a carbon dioxide reduction catalyst which is a copper complex may be used. For example, Patent Document 1 proposes a carbon compound reduction catalyst characterized by including a metal complex having a ligand having a phosphorus atom and a metal halide salt having two metal atoms, at least one of which is Cu. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-109157 Summary of the Invention [Problem to be solved by the invention]

[0004] In the ethylene production process using a copper catalyst, which is a carbon dioxide reduction catalyst, a large amount of by-products are easily generated and ethylene selectivity tends to be low. Therefore, there is a demand for the development of an ethylene production process with high ethylene selectivity.

[0005] An object of one embodiment of the present disclosure is to provide a method for producing ethylene with high ethylene selectivity. A problem to be solved by another embodiment of the present disclosure is to provide a carbon dioxide reduction electrode having high ethylene selectivity. A problem to be solved by another embodiment of the present disclosure is to provide a carbon dioxide reduction device having high ethylene selectivity. [Means for solving the problem]

[0006] Means for solving the above problems include the following means. <1> A method for producing ethylene, comprising a step of reacting carbon dioxide with water in the presence of a polynuclear copper complex represented by the following formula (1):

[0007] [ka] (In formula (1), Z is an alkylene group or an arylene group, R represents a hydrogen atom or a substituent, the multiple Rs may be the same or different, adjacent two Rs may be bonded to each other to form a ring, Y is any of the groups shown below, the multiple Ys may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.)

[0008] [ka] (In the formula, R a represents a hydrogen atom or a substituent.

[0009] <2> The polynuclear copper complex represented by the formula (1) is a polynuclear copper complex represented by the following formula (2): <1> The method for producing ethylene according to claim 1 .

[0010] [ka] (In formula (2), Ar 1 and Ar 2 are each independently an arylene group, R represents a hydrogen atom or a substituent, two adjacent Rs may be bonded to each other to form a ring structure, the multiple Rs may be the same or different, Y represents any one of the groups shown below, the multiple Ys may be the same or different, X represents a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.

[0011] [ka] (In the formula, R a represents a hydrogen atom or a substituent.

[0012] <3> A carbon dioxide reduction electrode comprising a conductive material carrying a polynuclear copper complex represented by the following formula (1):

[0013] [ka] (In formula (1), Z is an alkylene group or an arylene group, R represents a hydrogen atom or a substituent, the multiple Rs may be the same or different, adjacent two Rs may be bonded to each other to form a ring, Y is any of the groups shown below, the multiple Ys may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.)

[0014] [ka] (In the formula, R a represents a hydrogen atom or a substituent.

[0015] <4> The conductive material further includes a support. <3> The carbon dioxide reduction electrode according to claim 1. <5> Further comprising an ion conductor <3> or <4> The carbon dioxide reduction electrode according to claim 1. <6> An oxidation electrode; <3> ~ <5> a membrane separating the oxidation electrode and the carbon dioxide reduction electrode; an electrolyte; and a power source connected to the oxidation electrode and the carbon dioxide reduction electrode. Effect of the Invention

[0016] According to one embodiment of the present disclosure, a process for producing ethylene with high ethylene selectivity is provided. According to another embodiment of the present disclosure, a carbon dioxide reduction electrode is provided that has high ethylene selectivity. According to another embodiment of the present disclosure, a carbon dioxide reduction device having high ethylene selectivity is provided. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a carbon dioxide reduction electrode according to the present disclosure. [Diagram 2] 1 is a schematic cross-sectional view showing an example of a carbon dioxide reduction device according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment that is an example of the present disclosure will be described. These descriptions and examples are merely illustrative of the embodiment, and are not intended to limit the scope of the invention. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples.

[0019] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, it is assumed that the composition contains multiple substances corresponding to each component. When a species is present, it means the total amount of the species present in the composition, unless otherwise specified. The term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved.

[0020] Examples of the "substituent" include a halogen atom, an alkyl group (including a cycloalkyl group), an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl group, an aryloxy group, a divalent oxo group, an arylthio group, a monovalent heterocyclic group, a substituted amino group, an acyl group, an imine residue, an amide group, an acid imide group, a substituted oxycarbonyl group, a cyano group, an alkylsulfonyl group, and a nitro group. Note that, in the present specification, when referring to the number of carbon atoms, the number of carbon atoms does not usually include the number of carbon atoms of the substituent A.

[0021] The term "aromatic hydrocarbon ring group" refers to an atomic group remaining after removing one or more hydrogen atoms directly bonded to carbon atoms constituting an aromatic hydrocarbon ring which may be unsubstituted or substituted and which may be condensed with two or more rings.

[0022] The term "aromatic heterocyclic group" refers to an atomic group remaining after removing one or more hydrogen atoms directly bonded to carbon atoms or heteroatoms constituting an aromatic heterocycle, which may be unsubstituted or substituted and may be condensed with two or more rings.

[0023] In the compound names, "t-" means tertiary, "n-" means normal, and "p-" means para position. The dotted portions in the chemical structural formulae represent portions which may be either single bonds or double bonds.

[0024] <Production method of ethylene> The method for producing ethylene according to the present disclosure includes a step of reacting carbon dioxide with water in the presence of a polynuclear copper complex represented by the following formula (1).

[0025] [ka] (In formula (1), Z is an alkylene group or an arylene group, R represents a hydrogen atom or a substituent, the multiple Rs may be the same or different, adjacent two Rs may be bonded to each other to form a ring, Y is any of the groups shown below, the multiple Ys may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.)

[0026] [ka] (In the formula, R a represents a hydrogen atom or a substituent.

[0027] The ethylene production method according to an embodiment of the present disclosure has the above-mentioned configuration, and is therefore a method for producing ethylene with high ethylene selectivity. The reason for this is presumed to be as follows.

[0028] It is speculated that the production of ethylene using a polynuclear copper complex proceeds by the following process: carbon dioxide coordinates to the copper atom of the polynuclear copper complex, and two carbon dioxides coordinated to other copper atoms form bonds with each other, which then react with water to produce ethylene. It is believed that making it easier for two carbon dioxides coordinated to other copper atoms to form bonds with each other is an effective way to improve ethylene selectivity, and it is speculated that shortening the distance between the copper atoms is an effective way to achieve this. Here, the method for producing ethylene according to one embodiment of the present disclosure uses a polynuclear copper complex represented by the formula (1). The polynuclear copper complex represented by the formula (1) has a distance between copper atoms that makes it easy for two carbon dioxide atoms coordinated to different copper atoms to form a bond with each other. Therefore, it is presumed that this will be a method for producing ethylene with high ethylene selectivity.

[0029] (Polynuclear copper complex represented by formula (1)) The polynuclear copper complex represented by the formula (1) used in the method for producing ethylene according to the present disclosure will be described below. The polynuclear copper complex represented by the above formula (1) is suitably used as a carbon dioxide reduction catalyst.

[0030] In terms of ethylene selectivity, Z in formula (1) is preferably an alkylene group having 2 to 6 carbon atoms (also referred to as "number of carbon atoms") or an arylene group having 4 to 14 carbon atoms, more preferably an arylene group having 4 to 14 carbon atoms, and further preferably an arylene group having 6 to 10 carbon atoms. When Z is an alkylene group, Z is preferably a 1,3-propylene group. The arylene group in Z may be a divalent hydrocarbon aromatic group or a divalent heteroaromatic group. When Z is an arylene group, Z is preferably a phenylene group, a pyridinediyl group, a tetrafluorophenylene group, a naphthalenediyl group, a thiophenediyl group, a dimethylphenylene group, or a phenanthrenediyl group, more preferably a 1,2-phenylene group, a 3,4-pyridinediyl group, a 3,4,5,6-tetrafluoro-1,2-phenylene group, a 2,3-naphthalenediyl group, a 3,4-thiophenediyl group, a 3,4-dimethyl-1,2-phenylene group, or a 9,10-phenanthrenediyl group, and particularly preferably a 1,2-phenylene group.

[0031] From the viewpoint of ethylene selectivity, R in formula (1) is preferably a hydrogen atom, an alkyl group, an aryl group, an alkoxy group or an alkylthio group, and more preferably a hydrogen atom or an alkyl group. When R is an alkyl group, R is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and further preferably a methyl group or a t-butyl group. When R is an aryl group, R is preferably an aryl group having 6 to 14 carbon atoms, and more preferably a phenyl group. When R is an alkoxy group, R is preferably an alkoxy group having from 1 to 10 carbon atoms, more preferably an alkoxy group having from 1 to 4 carbon atoms, and further preferably a methoxy group. When R is an alkylthio group, R is preferably an alkylthio group having 1 to 10 carbon atoms, more preferably an alkylthio group having 1 to 4 carbon atoms, and further preferably a methylthio group.

[0032] In terms of ethylene selectivity, each Y in formula (1) is preferably the same group, and more preferably the group shown below.

[0033] [ka]

[0034] R in formula (1) a is preferably a hydrogen atom from the viewpoint of ethylene selectivity.

[0035] The counter ion represented by X in formula (1) is preferably an anion, and more preferably at least one anion selected from the group consisting of a fluoride ion, a chloride ion, a bromide ion, an iodide ion, a sulfide ion, an oxide ion, a hydroxide ion, a hydride ion, a sulfite ion, a phosphate ion, a cyanide ion, an acetate ion, a 2-ethylhexanoate ion, a carbonate ion, a sulfate ion, a nitrate ion, a hydrogen carbonate ion, a trifluoroacetate ion, a thiocyanide ion, a trifluoromethanesulfonate ion, an acetylacetonate, a tetrafluoroborate ion, a hexafluorophosphate ion, and a tetraphenylborate ion. The neutral molecule represented by X is preferably at least one neutral molecule selected from the group consisting of water, methanol, ethanol, n-propanol, isopropyl alcohol, 2-methoxyethanol, 1,1-dimethylethanol, ethylene glycol, N,N'-dimethylformamide, N,N'-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, acetone, chloroform, acetonitrile, benzonitrile, triethylamine, pyridine, pyrazine, diazabicyclo[2.2.2]octane, 4,4'-bipyridine, tetrahydrofuran, diethyl ether, dimethoxyethane, methyl ethyl ether, 1,4-dioxane, acetic acid, propionic acid, and 2-ethylhexanoic acid.

[0036] In formula (1), b is preferably an integer of 0 or more and 4 or less, more preferably an integer of 0 or more and 2 or less, and particularly preferably 2.

[0037] From the viewpoint of ethylene selectivity, the polynuclear copper complex represented by the formula (1) is preferably a polynuclear copper complex represented by the following formula (2).

[0038] [ka] (In formula (2), Ar 1 and Ar 2 are each independently an arylene group, R represents a hydrogen atom or a substituent, two adjacent Rs may be bonded to each other to form a ring structure, the multiple Rs may be the same or different, Y represents any one of the groups shown below, the multiple Ys may be the same or different, X represents a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.

[0039] [ka] (In the formula, R arepresents a hydrogen atom or a substituent.

[0040] Ar in formula (2) 1 and Ar 2 are preferably the same group from the viewpoints of ease of synthesis and ethylene selectivity. In addition, Ar in formula (2) 1 and Ar 2 are each independently preferably an arylene group having 4 to 14 carbon atoms, and more preferably an arylene group having 6 to 10 carbon atoms, from the viewpoint of ethylene selectivity. Ar 1 and Ar 2 The arylene group in may be a divalent hydrocarbon aromatic group or a divalent heteroaromatic group. Ar 1 and Ar 2 Specific examples of the alkyl group include preferably a phenylene group, a pyridinediyl group, a tetrafluorophenylene group, a naphthalenediyl group, a thiophenediyl group, a dimethylphenylene group, and a phenanthrenediyl group, more preferably a 1,2-phenylene group, a 3,4-pyridinediyl group, a 3,4,5,6-tetrafluoro-1,2-phenylene group, a 2,3-naphthalenediyl group, a 3,4-thiophenediyl group, a 3,4-dimethyl-1,2-phenylene group, and a 9,10-phenanthrenediyl group, and particularly preferably a 1,2-phenylene group.

[0041] R, X, Y and b in formula (2) have the same meanings as R, X, Y and b in formula (1), and preferred embodiments are also the same.

[0042] From the viewpoint of ethylene selectivity, the polynuclear copper complex represented by the formula (1) is more preferably a polynuclear copper complex represented by the following formula (3).

[0043] [ka] (In formula (3), Ar 1 and Ar 2are each independently an arylene group; R 1 represents a hydrogen atom, an alkyl group, an alkoxy group, or an alkylthio group, and 1 may be the same or different, R 2 represents a hydrogen atom, an alkyl group, or an aryl group, and 2 may be the same or different, and there may be multiple R 2 may be the same or different, R 3 represents a hydrogen atom, an alkyl group, or an aryl group, and 3 may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.

[0044] The two R in Eq. (3) 1 are preferably the same group from the viewpoints of ease of synthesis and ethylene selectivity. In addition, R in formula (3) 1 From the viewpoint of ethylene selectivity, is preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, even more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and particularly preferably a hydrogen atom or a t-butyl group. The four Rs in Equation (3) 2 are preferably the same group from the viewpoints of ease of synthesis and ethylene selectivity. In addition, R in formula (3) 2 From the viewpoint of ethylene selectivity, is preferably a hydrogen atom, an alkyl group, or an aryl group, more preferably a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, further preferably a hydrogen atom, a methyl group, or a phenyl group, and particularly preferably a hydrogen atom. The four Rs in Equation (3) 3 are preferably the same group from the viewpoints of ease of synthesis and ethylene selectivity. In addition, R in formula (3) 3From the viewpoint of ethylene selectivity, is preferably a hydrogen atom, an alkyl group, or an aryl group, more preferably a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, further preferably a hydrogen atom, a methyl group, or a phenyl group, and particularly preferably a hydrogen atom.

[0045] Ar in formula (3) 1 and Ar 2 is the Ar in formula (2). 1 and Ar 2 The same applies to the preferred embodiments. X and b in formula (3) have the same meanings as X and b in formula (1), and preferred embodiments are also the same.

[0046] A specific structural formula of the polynuclear copper complex represented by the above formula (1) is shown below, but the complex is not limited thereto. In the structural formula below, "t-Bu" means a t-butyl group, and " - "OAc" means acetate ion, and copper is divalent (Cu 2+ ).

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] [ka]

[0051] (Step of reacting carbon dioxide with water) The method for producing ethylene according to the present disclosure includes a step of reacting carbon dioxide with water in the presence of a polynuclear copper complex. This step is not particularly limited as long as it is a step that can react carbon dioxide and water in the presence of a polynuclear copper complex; from the viewpoint of ethylene selectivity, however, it is preferable to perform this step using a carbon dioxide reduction device that includes an oxidation electrode, a carbon dioxide reduction electrode according to the present disclosure described below, a membrane separating the oxidation electrode and the carbon dioxide reduction electrode, an electrolyte, and a power source connected to the oxidation electrode and the carbon dioxide reduction electrode. The carbon dioxide reduction device will be described in detail later.

[0052] A method for reacting carbon dioxide with water using a carbon dioxide reduction device includes passing a current through an oxidation electrode and a carbon dioxide reduction electrode, flowing carbon dioxide into the device so that it comes into contact with the carbon dioxide reduction electrode, and reacting the water contained in the electrolyte of the carbon dioxide reduction device with carbon dioxide on the carbon dioxide reduction electrode.

[0053] <Carbon dioxide reduction electrode> The carbon dioxide reduction electrode according to the present disclosure comprises a conductive material supporting the polynuclear copper complex represented by the formula (1).

[0054] (Conductive materials) As the conductive material, any known material can be used without any particular limitation as long as it can support the polynuclear copper complex. The polynuclear copper complex may be supported on a flat or rod-shaped carbonaceous material or metal material, or on a porous carbonaceous material or metal material such as carbon paper or metal mesh. The polynuclear copper complex may also be supported on a powder material such as carbon black (CB) or metal particles. That is, the polynuclear copper complex can be used as a composite material supported on a conductive material. The composite material supported on a powder material may be molded by compression or the like, or the powder material supported on a powder material may be fixed to a support such as a flat, rod-shaped, lattice-shaped, or porous carbonaceous material or metal material.

[0055] The conductive material is not particularly limited, but is preferably a porous carbon material. Examples of conductive materials include carbon particles such as Norit, Ketjen Black, Vulcan, Black Pearl, and acetylene black; fullerenes such as C60 and C70; carbon nanotubes; carbon nanohorns; carbon fibers; graphene; graphene oxide; reduced graphene oxide; and graphene mesosponge.

[0056] The method of supporting is not particularly limited, and any known method can be applied. Examples of the method include a method of vacuum-depositing the polynuclear copper complex on a conductive support (conductive material), a method of immersing a conductive support in a dispersion liquid in which a polynuclear copper complex is dispersed in a solvent or a solution in which a polynuclear copper complex is dissolved in a solvent, and drying the conductive support, a method of applying a dispersion liquid in which a polynuclear copper complex is dispersed in a solvent or a solution in which a polynuclear copper complex is dissolved in a solvent onto a conductive support, and a method of adding a powdered conductive support to a dispersion liquid in which a polynuclear copper complex is dispersed in a solvent or a solution in which a polynuclear copper complex is dissolved in a solvent, and adsorbing the polynuclear copper complex on the surface of the powder.

[0057] The amount of polynuclear copper complex supported on the conductive material is preferably an amount such that the mass of copper atoms relative to the mass of the conductive material is 1% by mass or more and 50% by mass or less, and more preferably an amount such that the mass of copper atoms is 2% by mass or more and 10% by mass or less.

[0058] The amount of the polynuclear copper complex supported on the conductive material is preferably such that the mass of the polynuclear copper complex is 1% by mass or more and 100% by mass or less relative to the mass of the conductive material, and more preferably such that the mass of the polynuclear copper complex is 5% by mass or more and 50% by mass or less.

[0059] The mass of copper atoms relative to the mass of the conductive material is measured using a thermogravimetric differential thermal analyzer (TG-DTA) device. The measurement method is as follows: This can be done by using a thermogravimetric differential thermal analyzer to measure a TG-DTA curve while increasing the temperature from 25° C. or lower to 900° C. at a rate of 10° C. / min in air.

[0060] (Support) The carbon dioxide reduction electrode according to the present disclosure preferably further includes a support for supporting the conductive material. The support is preferably conductive, and examples thereof include carbon nanotubes, graphene, carbon black, carbon cloth, carbon paper, glassy carbon, graphite, and tantalum (Ta).

[0061] (Ionic conductor) The carbon dioxide reduction electrode according to the present disclosure preferably further includes an ion conductor. As the ion conductor, a known one can be used, and is not particularly limited, but an electrolyte solution in which an ionic substance is dissolved in a solvent such as water may be used, or an ion exchange resin may be used. The ion conductor used between the reduction electrode and the membrane and the ion conductor used between the oxidation electrode and the membrane may be the same or different, and both the electrolyte solution and the ion exchange resin may be used as the ion conductor. The ionic conductor includes an ionomer. An ionomer is a polymer neutralized with an ion. The ionomer is preferably a polymer neutralized with a cation such as a metal (cationic ionomer) or a polymer neutralized with an anion (anionic ionomer). Examples of anionic ionomers include Sustanion manufactured by Dioxide Materials, AEMION manufactured by Ionomer Innovations, Fumasep manufactured by FumaTech, and Orion manufactured by Orion.

[0062] The ion conductor preferably accounts for 10% by mass or more and 200% by mass or less based on the mass of the conductive material on which the polynuclear copper complex is supported.

[0063] (Other Ingredients) The carbon dioxide reduction electrode according to the present disclosure may contain other components in addition to the conductive material, the support, and the ion conductor. Examples of other components include water-repellent materials. Examples of water-repellent materials include fluorine-containing resins, silicon-containing resins, silane coupling agents, waxes, etc., and from the viewpoint of water-repellent effect, fluorine-containing resins are preferred, and examples of fluorine-containing resins include polytetrafluoroethylene.

[0064] (Method of manufacturing carbon dioxide reduction electrode) The carbon dioxide reduction electrode according to the present disclosure is preferably manufactured by preparing an electrode ink in which a conductive material carrying the polynuclear copper complex represented by formula (1) above, an ionic conductor as necessary, and other components are dispersed in a solvent, and then applying the electrode ink to a support and drying it.

[0065] (An example of a carbon dioxide reduction electrode) FIG. 1 shows an example of a carbon dioxide reduction electrode according to the present disclosure. FIG. 1 is a schematic cross-sectional view of a carbon dioxide reduction electrode according to the present disclosure. In FIG. 1, a carbon dioxide reduction electrode 10 has, on a support 2, a layer 1 containing a conductive material on which a polynuclear copper complex represented by the above formula (1) is supported. When components other than the ion conductor are contained, these components are contained in the layer 1 containing the conductive material on which the polynuclear copper complex is supported.

[0066] <Carbon dioxide reduction device> The carbon dioxide reduction device according to the present disclosure comprises: An oxidation electrode; A carbon dioxide reduction electrode according to the present disclosure; a membrane separating the oxidation electrode and the polynuclear copper complex; An electrolyte; and a power source connected to the oxidation electrode and the carbon dioxide reduction electrode.

[0067] (An example of a carbon dioxide reduction device) FIG. 2 shows an example of a carbon dioxide reduction device according to the present disclosure. 2, the carbon dioxide reduction device 100 includes an oxidation electrode 11, a carbon dioxide reduction electrode 10, a membrane 12 separating the oxidation electrode 11 and the carbon dioxide reduction electrode 10, an electrolyte 13, and a power source 14 connected to the oxidation electrode 11 and the carbon dioxide reduction electrode 10. The carbon dioxide reduction device 100 also includes an electrolytic cell 15 including these components, and a reaction cell 16. Here, the carbon dioxide reduction electrode 10 is preferably placed so that the conductive material carrying the polynuclear copper complex is in contact with the electrolyte 13 .

[0068] The carbon dioxide reduction device 100 is suitable for a reaction in which carbon dioxide is reduced to produce ethylene. It is possible to use the carbon dioxide reduction electrode 10 in this reaction. When used in this reaction, it is preferable to use a power source 14 to pass a current from the carbon dioxide reduction electrode 10 to the oxidation electrode 11. It is then preferable to pass carbon dioxide into the reaction vessel 16 in the direction of arrow A. The carbon dioxide that has flowed into the reaction vessel 16 comes into contact with the polynuclear copper complex in the carbon dioxide reduction electrode 10. As a result, the reaction represented by the following reaction formula 1 proceeds on the carbon dioxide reduction electrode 10 side, and the reaction represented by the following reaction formula 2 proceeds on the oxidation electrode 11 side. Reaction 1:2CO 2 +8H 2 O+12e - →C 2 H 4 +12OH - Reaction 2: 12OH - →3O 2 +6H 2 O+12e - The produced ethylene flows out of the reaction tank 16 in the direction of arrow B.

[0069] The carbon dioxide reduction electrode will be described in detail below. Note that reference numerals will be omitted.

[0070] (Oxidation electrode) The oxidation electrode may be any known electrode, and is not particularly limited, but is preferably an electrode that oxidizes water or hydroxide ions to generate oxygen. Examples of the electrode include, but are not limited to, porous materials made of metal materials such as titanium and nickel, and carbonaceous materials such as carbon paper. The oxidation electrode may contain metals such as platinum, palladium, and nickel, or metal oxides such as nickel oxide, iridium oxide, and ruthenium oxide in order to promote the generation of oxygen.

[0071] (Carbon dioxide reduction electrode) The carbon dioxide reduction electrode used is the carbon dioxide reduction electrode according to the present disclosure.

[0072] (film) The membrane separating the reduction electrode and the oxidation electrode may be any known material, and may be any material having ion conductivity, although it is not particularly limited thereto. For example, a porous polymer membrane such as polytetrafluoroethylene (PTFE), a porous membrane such as a glass filter, a cation exchange membrane such as Nafion, an anion exchange membrane such as Sustenion, Neocepta, or Selemion may be used. Although not particularly limited thereto, an ion exchange membrane is preferred. As the ion exchange membrane, an anion exchange membrane is more preferred.

[0073] (electrolyte) The electrolyte may be any known electrolyte, and is not particularly limited. Examples of the electrolyte include an electrolyte containing cations such as sodium ions and potassium ions, anions such as hydrogen carbonate ions, carbonate ions, hydroxide ions, sulfate ions, phosphate ions, and borate ions, and water.

[0074] The ion concentration of the electrolyte is preferably 0.01 mol / L or more and 5.0 mol / L or less, and more preferably 0.5 mol / L or more and 2.0 mol / L or less.

[0075] (power supply) A power source is connected to the oxidation electrode and the carbon dioxide reduction electrode. The power source is not particularly limited as long as it can pass a current between the carbon dioxide reduction electrode and the oxidation electrode. As the power supply, for example, an electrochemical analyzer 701C manufactured by BAS Corporation can be used.

[0076] An Agilent 6130 LCMSD was used for ESI-MS measurements. EXAMPLES

[0077] The present invention will be described in more detail below with reference to examples, but these are merely illustrative and the present invention is not limited thereto. That is, a person skilled in the art can carry out the present invention by making various modifications to the examples shown below. For example, the materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately modified as long as they do not deviate from the gist of the present invention. In addition, the values ​​of various manufacturing conditions and evaluation results in the following examples have the meaning of the preferred upper or lower limit values ​​in the embodiment of the present invention, and the preferred ranges have the meaning of the preferred upper or lower limit values ​​described above, and the preferred ranges may be ranges defined by the combination of the upper or lower limit values ​​and the values ​​of the following examples or the values ​​of the examples. In the following description, unless otherwise specified, all "parts" and "%" are based on mass.

[0078] The performance of the carbon dioxide reduction electrode prepared by the method described in the examples and comparative examples was evaluated using a carbon dioxide reduction device 100 shown in FIG. 2. A platinum mesh was used as the oxidation electrode 11. A carbon dioxide reduction electrode was used as the reduction electrode 10. An anion exchange membrane (Sustainion manufactured by Dioxide Materials) was used as the membrane 12. A 1.0M (=1.0mol / L) potassium hydroxide aqueous solution was used as the electrolyte 13. An electrochemical measurement device (Electrochemical Analyzer 701C manufactured by BAS Corporation) was used as the power source 14. Furthermore, a Hg / HgO reference electrode (manufactured by BAS Corporation) was installed as a reference electrode in the electrolyte 13 between the membrane 12 and the reduction electrode 10. Carbon dioxide gas set at 5mL / min was circulated in the direction of the arrow A of the reaction tank 16, and a constant potential was applied to the reduction electrode 10 using an electrochemical measurement device to perform electrochemical measurement. 50 μL of the outlet gas (gas flowing out of the reaction vessel 16 in the direction of arrow B) was collected using a gas-tight syringe, and the products contained in the gas were quantitatively analyzed using a gas chromatograph (Shimadzu Corporation GC-2010 / BID detector). The Faraday efficiency of each product was calculated from the ratio of the charge used to generate each observed product out of the total charge used in the reaction. A higher value of the Faraday efficiency of ethylene indicates that ethylene is selectively generated, meaning that ethylene selectivity is high.

[0079] <Synthesis Example 1> Polynuclear copper complex (1) was synthesized according to the following procedure.

[0080] [ka]

[0081] 0.88 g of copper acetate monohydrate(II) (Cu(OAc) 2 H 2A 4 mL methanol solution containing 0.52 g of 1,2-phenylenediamine was added to a 50 mL naphtha flask containing 10 mL of a methanol (MeOH) solution containing 1.0 g of 4-t-butyl-2,6-diformylphenol with stirring. Then, 8 mL of methanol containing 1.0 g of 4-t-butyl-2,6-diformylphenol was gradually added, and the mixture was refluxed for 3 hours. The solution was concentrated using an evaporator, and then cooled in a refrigerator to produce a brown precipitate. The resulting precipitate was filtered and dried to obtain polynuclear copper complex (1) (yield 0.26 g: 16% yield). The results of electrospray ionization mass spectrometry (ESI-MS) measurements were confirmed as follows.

[0082] ESI-MS(M / Z):found;740.2,calcd;739.01(M-acetate anion) + .

[0083] <Synthesis Example 2> Polynuclear copper complex (2) was synthesized as follows.

[0084] [ka]

[0085] A 4mL methanol solution containing 0.36g of 1,2-phenylenediamine was added to a 50mL naphtha flask containing 10mL of a methanol solution containing 0.6g of copper acetate monohydrate (II) while stirring. Next, 8mL of methanol containing 0.5g of 2,6-diformylphenol was gradually added, and the mixture was refluxed for 3 hours. The solution was concentrated using an evaporator, and then cooled in a refrigerator to produce a brown precipitate. The resulting precipitate was filtered and dried to obtain polynuclear copper complex (2) (yield 0.27g: 24% yield). The results of the ESI-MS measurement were confirmed as follows.

[0086] ESI-MS(M / Z):found;628.2,calcd;627.01(M-acetate anion) + .

[0087] <Comparative Synthesis Example 1> The mononuclear copper complex (1') was synthesized by the following procedure.

[0088] [ka]

[0089] A 4mL methanol solution containing 0.44g of 1,2-phenylenediamine was added to a 50mL naphtha flask containing 10mL of a methanol solution containing 0.74g of copper acetate monohydrate (II) while stirring. Next, 8mL of methanol containing 1.0g of salicylaldehyde was gradually added, and the mixture was refluxed for 3 hours. The solution was concentrated using an evaporator, and then cooled in a refrigerator to produce a brown precipitate. The resulting precipitate was filtered and dried to obtain the mononuclear copper complex (1') (yield 1.24g: 80% yield). The results of the ESI-MS measurement were confirmed as follows.

[0090] ESI-MS(M / Z):found;378.2, calcd;377.04.

[0091] <Example 1> <<Preparation of Carbon Dioxide Reduction Electrode (1)>> In a reaction vessel, 250 mg of carbon black (KetjenBlack EC600JD manufactured by Lion Specialty Chemicals Co., Ltd.) was weighed as a conductive material. In another reaction vessel, polynuclear copper complex (1) was weighed so that the mass of copper atoms was 5% relative to the carbon black, and a mixed solution of chloroform and methanol was added. After confirming that a solution of polynuclear copper complex (1) had been formed, the solution was transferred to a reaction vessel in which a conductive material had been weighed out and made into a dispersion. By irradiating the dispersion with ultrasonic waves, a suspension in which a conductive material carrying a carbon dioxide reduction catalyst was uniformly dispersed was obtained. After filtering the suspension using a filter, the suspension was dried under reduced pressure to obtain a conductive material (1) carrying a carbon dioxide reduction catalyst.

[0092] 20.0 mg of the conductive material (1) powder and 20.0 mg of PTFE fine particles (Sigma-Aldrich) were weighed into a screw tube, and 2.50 mL of ethanol and 400 mg of a 5% ethanol solution of Sustanion (Dioxide Materials) as an anionic ionomer that is an ion conductor were added to obtain a dispersion. Ultrasonic waves were irradiated to this dispersion to obtain an ink. Carbon paper (diameter 25 mm) was used as a support, and 250 mg of the ink obtained above was applied to the carbon paper and then dried to obtain a carbon dioxide reduction electrode (1).

[0093] <Example 2 and Comparative Example 1> <<Preparation of Carbon Dioxide Reduction Electrodes (2) and (1')>> Carbon dioxide reduction electrodes (2) and (1') were obtained in the same manner as in Example 1, except that the copper complex, conductive material, ion conductor, additive, and support were used in the combinations shown in the table below.

[0094] [Table 1]

[0095] <Evaluation Results> Electrochemical measurements were carried out by the above-mentioned method using the carbon dioxide reduction electrodes obtained in Examples 1 and 2, and Comparative Example 1. The results are shown in Table 2.

[0096] [Table 2]

[0097] From the above results, it is understood that the ethylene production process of this example has higher ethylene selectivity than the comparative example. [Explanation of symbols]

[0098] 1: layer containing a conductive material carrying a polynuclear copper complex, 2: support, 10: carbon dioxide reduction electrode, 11: oxidation electrode, 12: membrane, 13: electrolyte, 14: power source, 15: electrolytic cell, 16: reaction cell, 100: carbon dioxide reduction device

Claims

1. The method includes reacting carbon dioxide with water in the presence of a polynuclear copper complex represented by the following formula (1): A method for producing ethylene. 【Chemistry 1】 (In formula (1), Z is an alkylene group or an arylene group, R represents a hydrogen atom or a substituent, the multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring, Y is any of the groups shown below, the multiple Ys may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.) 【Chemistry 2】 (In the formula, R ａ represents a hydrogen atom or a substituent.

2. The method for producing ethylene according to claim 1, wherein the polynuclear copper complex represented by the formula (1) is a polynuclear copper complex represented by the following formula (2): 【Chemistry 3】 (In formula (2), Ar １ and Ar ２ are each independently an arylene group, R represents a hydrogen atom or a substituent, two adjacent Rs may be bonded to each other to form a ring structure, a plurality of Rs may be the same or different, Y represents any one of the groups shown below, a plurality of Ys may be the same or different, X represents a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are a plurality of Xs, they may be the same or different. 【Chemistry 4】 (In the formula, R ａ represents a hydrogen atom or a substituent.

3. The conductive material includes a polynuclear copper complex represented by the following formula (1): Carbon dioxide reduction electrode. 【Chemistry 5】 (In formula (1), Z is an alkylene group or an arylene group, R represents a hydrogen atom or a substituent, the multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring, Y is any of the groups shown below, the multiple Ys may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.) 【Chemistry 6】 (In the formula, R ａ represents a hydrogen atom or a substituent.

4. The carbon dioxide reduction electrode according to claim 3, further comprising a support for supporting the conductive material.

5. 5. The carbon dioxide reduction electrode according to claim 3 or 4, further comprising an ion conductor.

6. An oxidation electrode; The carbon dioxide reduction electrode according to claim 3 ; a membrane separating the oxidation electrode and the carbon dioxide reduction electrode; An electrolyte; a power source connected to the oxidation electrode and the carbon dioxide reduction electrode; Carbon dioxide reduction device.

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