Electrochemical reactor and method for producing oxygen-containing organic material

Abstract

This electrochemical reactor 10 is provided with: a cathode 11 which comprises a first catalyst 16 that reduces carbon dioxide to carbon monoxide; an anode 12; an electrolyte solution 13 which contains a reaction substrate and an electrolyte; and a second catalyst 17 which synthesizes an oxygen-containing organic material from the carbon monoxide and the reaction substrate. The electrolyte solution 13 has a convection current, and the direction of the convection current F is set such that the convection current comes into contact with the first catalyst 16 and the second catalyst 17 in this order.

Description

Electrochemical reaction device and method for producing oxygen-containing organic substance

[0001] The present invention relates to an electrochemical reaction device for producing an oxygen-containing organic substance such as a carbonyl compound using carbon dioxide as a raw material, and a method for producing an oxygen-containing organic substance.

[0002] Electrochemical synthesis methods have been attracting attention in recent years because they do not require the use of highly toxic substrates or highly explosive oxygen-mixed gases, and can directly utilize electricity from renewable energy sources. Furthermore, in recent years, studies have been conducted to generate organic compounds through electrochemical reactions using raw materials such as carbon dioxide and carbon monoxide obtained by reducing carbon dioxide, with the aim of curbing global warming and replacing fossil fuels.

[0003] Carbonyl compounds such as organic carbonates are used in a variety of fields, including paints, adhesives, electrolytes, and resin raw materials. Recently, attempts have been made to electrochemically synthesize carbonyl compounds using carbon dioxide as a raw material and various catalysts. For example, Patent Document 1 discloses an electrochemical reaction device comprising a first electrolytic cell provided with a first electrode, a second electrolytic cell provided with a second electrode and containing an electrolysis substrate, an ion transport membrane separating the first electrolytic cell from the second electrolytic cell, and a connecting path connecting the first electrolytic cell to the second electrolytic cell. In the electrochemical reaction device of Patent Document 1, carbon dioxide is reduced to carbon monoxide at the first electrode (cathode), and the generated carbon monoxide is discharged to the second electrolytic cell through a connecting pipe. A valuable product such as an organic carbonate is produced from the carbon monoxide and the electrolyte at the second electrode (anode).

[0004] International Publication No. 2019 / 182164

[0005] However, in the conventional method for producing carbonyl compounds such as organic carbonates using an electrochemical reaction device, the structure of the electrochemical reaction device becomes complicated, and further improvements are required for practical use.

[0006] Furthermore, in electrochemical reactors that use carbon monoxide converted at the cathode to produce a target valuable product at the anode, increasing the current density to increase the production volume of the target product makes the halide ions in the electrolyte more reactive, resulting in the generation of halogen as a by-product. When the halogen ions react to form halogen, the electrolyte concentration decreases, increasing electrical resistance and power consumption, which in turn increases production costs. Additionally, the generation of by-products reduces the production volume of the target product, thereby reducing production efficiency. Therefore, when obtaining valuable products such as carbonate compounds from carbon dioxide, there is a demand for electrochemical reactors that can increase production volume while reducing power consumption.

[0007] Therefore, an object of the present invention is to provide an electrochemical reaction device capable of electrochemically synthesizing oxygen-containing organic substances such as carbonyl compounds from carbon dioxide using a device with a relatively simple structure, and a method for producing oxygen-containing organic substances using the electrochemical reaction device.A more specific object of the present invention is to provide an electrochemical reaction device and a method for producing oxygen-containing organic substances using the electrochemical reaction device that can increase production volume while suppressing power consumption when obtaining oxygen-containing organic substances such as carbonyl compounds from carbon dioxide.

[0008] The present invention provides the following [1] to

[29] . [1] An electrochemical reaction device comprising: a cathode having a first catalyst that reduces carbon dioxide to carbon monoxide; an anode; an electrolytic solution containing a reactant and an electrolyte; and a second catalyst that synthesizes an oxygen-containing organic substance from the carbon monoxide and the reactant, wherein the electrolytic solution has convection, and the direction of the convection is formed so that the first catalyst and the second catalyst contact each other in that order. [2] The electrochemical reaction device according to [1] above, wherein the first catalyst and the second catalyst are arranged on the same plane, and the electrolytic solution has convection that flows parallel to the plane. [3] The electrochemical reaction device according to [1] above, wherein the first catalyst and the second catalyst are arranged to face each other within the electrochemical reaction device. [4] The electrochemical reaction device according to [3] above, which has a rectifying layer between the first catalyst and the second catalyst. [5] The electrochemical reaction device according to [3] above, which has an isolation layer between the first catalyst and the second catalyst that separates the carbon monoxide generated at the first catalyst from the oxidant generated at the anode. [6] The electrochemical reaction device according to [1] above, wherein the first catalyst and the second catalyst are arranged perpendicular to or at an angle. [7] The electrochemical reaction device according to any one of [1] to [6] above, wherein the anode has the second catalyst. [8] The electrochemical reaction device according to any one of [1] to [7] above, comprising a first reaction section having the cathode and the anode, and a second reaction section having the second catalyst, and wherein the electrolytic solution has a convection direction flowing through the first reaction section and the second reaction section in this order. [9] The electrochemical reaction device according to [8] above, wherein the first reaction section has an isolation layer separating carbon monoxide generated by the first catalyst from an oxidant generated by the anode.

[10] The electrochemical reaction device according to [8] or [9] above, wherein the interior of the first reaction section is isolated into a cathode-side region and an anode-side region by the isolation layer, and wherein the convection direction flows through the cathode-side region, the anode-side region, and the second reaction section in this order.

[11] The electrochemical reaction device according to any one of [8] to

[10] above, wherein the inside of the first reaction section is separated into a cathode-side region and an anode-side region by the separation layer, and the direction of convection flows from the cathode-side region and the anode-side region to the second reaction section in this order.

[12] The electrochemical reaction device according to any one of [8] to

[11] above, wherein the inside of the first reaction unit is separated into a cathode-side region and an anode-side region by the separating layer, and wherein the electrolytic solution has a convection current that circulates from the cathode-side region to the outside of the first reaction unit and then returns to the cathode-side region.

[13] The electrochemical reaction device according to any one of [8] to

[12] above, wherein the inside of the first reaction unit is separated into a cathode-side region and an anode-side region by the separating layer, and wherein the electrolytic solution has a convection current that circulates between the anode-side region and the second reaction unit.

[14] The electrochemical reaction device according to

[13] above, further comprising a convection current that causes gas in the electrolytic solution to flow from the cathode-side region to a path along which the circulating convection current flows, thereby supplying the gas to the second reaction unit.

[15] The electrochemical reaction device according to any one of [8] to

[14] above, wherein the second reaction section comprises a catalyst layer containing the second catalyst, and wherein the second reaction section has a convection current in which the electrolytic solution flows from bottom to top.

[16] The electrochemical reaction device according to

[15] above, wherein a gas diffusion mechanism is provided below the catalyst layer.

[17] The electrochemical reaction device according to any one of [8] to

[16] above, wherein the second reaction section comprises a catalyst layer containing the second catalyst, and wherein the second catalyst is an active particle-containing catalyst comprising a support and active particles containing a metal element supported on the support, and wherein the amount of metal in the active particles in the catalyst layer is 0.1 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the support.

[18] The electrochemical reaction device according to any one of [1] to

[17] above, wherein the second catalyst is contained in the electrolytic solution.

[19] The electrochemical reaction device according to any one of [1] to

[18] above, wherein the first reaction section is a single-chamber electrochemical cell.

[20] The electrochemical reaction device according to any one of [1] to

[19] above, wherein the first catalyst contains CoO and a component derived from a pyridine derivative.

[21] The electrochemical reaction device according to any one of [1] to

[20] above, wherein the second catalyst contains at least one of Pd and Au.

[22] The electrochemical reaction device according to any one of [1] to

[21] above, wherein the reaction substrate is an alcohol-based compound.

[23] The electrochemical reaction device according to any one of [1] to

[22] above, wherein the second catalyst is a catalyst for synthesizing a carbonyl compound from carbon monoxide and a reactant.

[24] A method for producing an oxygen-containing organic substance by synthesizing an oxygen-containing organic substance from carbon dioxide in an electrochemical reaction device comprising: a cathode having a first catalyst that reduces carbon dioxide to carbon monoxide, an anode, an electrolytic solution containing a reactant and an electrolyte, and a second catalyst that synthesizes an oxygen-containing organic substance from carbon monoxide and the reactant, wherein convection is formed so that the first catalyst and then the second catalyst come into contact with the electrolytic solution.

[25] The method for producing an oxygen-containing organic substance according to

[24] above, wherein the electrochemical reaction device comprises a first reaction section including a cathode and an anode, and a second reaction section including the second catalyst, and wherein a convection direction is formed in the electrolytic solution so that the first reaction section and then the second reaction section flow in that order.

[26] An electrochemical reaction device comprising: an electrochemical cell including a cathode having a first catalyst that reduces carbon dioxide to carbon monoxide and an anode, a reaction section having a second catalyst that synthesizes an oxygen-containing organic substance from carbon monoxide and a reactant, and an electrolytic solution containing a reactant and an electrolyte, wherein the electrolytic solution has a convection direction that flows through the electrochemical cell and the reaction section in that order.

[27] A method for producing an oxygen-containing organic substance by synthesizing an oxygen-containing organic substance from carbon dioxide in an electrochemical reaction device comprising: an electrochemical cell including a cathode having a first catalyst that reduces carbon dioxide to carbon monoxide and an anode, a reaction section having a second catalyst that synthesizes an oxygen-containing organic substance from carbon monoxide and a reactant, and an electrolytic solution containing a reactant and an electrolyte, wherein the electrochemical reaction device forms a convection direction that flows through the electrochemical cell and the reaction section in that order.

[28] An electrochemical cell comprising: a cathode having a first catalyst that reduces carbon dioxide to carbon monoxide; an anode; an electrolytic solution containing a reactant and an electrolyte; and a second catalyst that synthesizes an oxygen-containing organic substance from the carbon monoxide and the reactant, wherein the electrolytic solution has a convection flow, and the direction of the convection flow is formed so that the electrolytic solution contacts the first catalyst and then the second catalyst in that order.

[29] A method for producing an oxygen-containing organic substance, in which an oxygen-containing organic substance is synthesized from carbon dioxide in an electrochemical cell including a cathode having a first catalyst that reduces carbon dioxide to carbon monoxide, an anode, an electrolytic solution containing a reaction substrate and an electrolyte, and a second catalyst that synthesizes an oxygen-containing organic substance from carbon monoxide and the reaction substrate, wherein convection is formed so that the first catalyst and then the second catalyst come into contact with the electrolytic solution.

[0009] According to the present invention, an oxygen-containing organic compound such as a carbonyl compound can be electrochemically synthesized from carbon dioxide using an apparatus having a relatively simple structure. Furthermore, according to one embodiment of the present invention, when obtaining an oxygen-containing organic compound such as a carbonyl compound from carbon dioxide, it is possible to increase the production amount while suppressing power consumption.

[0010] FIG. 1 is a schematic diagram showing an electrochemical reaction device according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing an electrochemical reaction device according to a second embodiment of the present invention. FIG. 3 is a schematic diagram showing an electrochemical reaction device according to a third embodiment of the present invention. FIG. 4 is a schematic diagram showing an electrochemical reaction device according to a modified example of the third embodiment of the present invention. FIG. 5 is a schematic diagram showing an electrochemical reaction device according to a fourth embodiment of the present invention. FIG. 6 is a schematic diagram showing an electrochemical reaction device according to a fifth embodiment of the present invention. FIG. 7 is a schematic diagram showing an electrochemical reaction device according to an eighth embodiment of the present invention. FIG. 9 is a schematic diagram showing an electrochemical reaction device according to a ninth embodiment of the present invention. FIG. 10 is a schematic diagram showing an electrochemical reaction device according to an eleventh embodiment of the present invention. FIG. 11 is a schematic diagram showing an electrochemical reaction device according to Comparative Example 1.

[0011] Hereinafter, an electrochemical reaction device and a method for producing an oxygen-containing organic substance according to the present invention will be described using embodiments. In the following description, the X direction is any one direction inside the cell, and the Y direction is a direction perpendicular to the X direction.

[0012] First Embodiment FIG. 1 shows an electrochemical reaction device according to a first embodiment of the present invention. The electrochemical reaction device 10 according to the first embodiment of the present invention comprises an electrochemical cell including a cathode 11, an anode 12, and an electrolytic solution 13 containing a reactant and an electrolyte. In this embodiment, the electrochemical reaction device comprises a single electrochemical cell, and a series of reactions for obtaining an oxygen-containing organic compound from carbon dioxide are all carried out in the electrochemical cell. The electrochemical reaction device (electrochemical cell) 10 is provided with a plurality of cathodes 11 and anodes 12. Each cathode 11 has a first catalyst 16 that reduces carbon dioxide to carbon monoxide. Each anode 12 has a second catalyst 17 that synthesizes an oxygen-containing organic compound from carbon monoxide and the reactant. The second catalyst 17 is preferably a catalyst that synthesizes a carbonyl compound from carbon monoxide and the reactant. The reactant may be any substance that can react with carbon monoxide to produce an oxygen-containing organic compound, but is preferably a raw material that can be used to produce a carbonyl compound, and, as described below, is more preferably an alcohol-based compound.

[0013] In this embodiment, the electrochemical reaction device 10 consists of one reaction chamber. The reaction chamber is filled with an electrolyte 13. The reaction chamber has wall surfaces 10A and 10B that face each other in the Y direction. In this embodiment, multiple pairs of cathodes 11 and anodes 12 are provided, and each pair of cathodes 11 and anodes 12 is attached to either wall surface 10A or 10B, and is arranged to face each other in the Y direction. Furthermore, the cathodes 11 and anodes 12 are arranged alternately on each of wall surfaces 10A and 10B in the X direction.

[0014] With the above configuration, the pair of opposing cathodes 11 and anodes 12 are arranged alternately along the X direction. Furthermore, on each of the cell wall surfaces 10A and 10B, the first catalyst 16 of the cathode 11 and the second catalyst 17 of the anode 12 are arranged on the same plane. On each of the wall surfaces 10A and 10B, the same plane on which the first and second catalysts 16 and 17 are arranged is a plane parallel to the X direction. A voltage is applied between the pair of opposing cathodes 11 and anodes 12 from a power source (not shown). In FIG. 1 , the multiple cathodes 11 and anodes 12 are connected in series, with one cathode 11 connected to a negative terminal and one anode 12 connected to a positive terminal, but the connection method is not particularly limited. The cathodes 11 and anodes 12 may be connected to terminals via current collectors or the like, but this is not particularly limited.

[0015] A supply port 14 and a discharge port 15 are provided on each of wall surfaces 10C, 10D of the reaction chamber facing each other in the X direction. As a result, the supply port 14 and the discharge port 15 are disposed outside the anode 22 and the cathode 21, and are disposed so as to sandwich the anode 22 and the cathode 21 when viewed along the Y direction. While FIG. 1 illustrates an embodiment in which three pairs of cathode 11 and anode 12 are provided, any number of pairs of cathode 11 and anode 12 may be provided as long as they are two or more pairs, for example, four or more pairs may be provided. The reaction chamber may be formed from, but is not limited to, glass, a resin material, or a combination thereof. The reaction chamber may be assembled, for example, by stacking a frame member 18A having the supply port 14 and the discharge port 15 and substrates 18C, 18D sandwiching the frame member 18A via a packing 18E or the like, but is not particularly limited thereto.

[0016] In this embodiment, the electrolytic solution 13 flows from the supply port 14 toward the discharge port 15 and is discharged from the discharge port 15, thereby generating a convection F. The electrolytic solution 13 discharged from the discharge port 15 may be circulated and resupplied from the supply port 14, and the circulation may be repeated. The supply of the electrolytic solution 13 is not particularly limited, and may be performed by a pump such as a diaphragm pump, a syringe pump, or a peristaltic pump, or may be performed by a known means other than a pump. The electrolytic solution 13 may also be supplied by utilizing gravity to generate a convection F.

[0017] The electrolytic solution 13 supplied from the supply port 14 preferably contains carbon dioxide, and the electrolytic solution 13 filled in the reaction chamber preferably also contains carbon dioxide. The method for adding carbon dioxide to the electrolytic solution 13 is not particularly limited, but it is preferable to dissolve carbon dioxide in the electrolytic solution 13 by bubbling carbon dioxide into the electrolytic solution 13 before supply. It is also preferable to mix the carbon dioxide with the electrolytic solution 13 so that some of the carbon dioxide is dissolved in the electrolytic solution 13 and some of the carbon dioxide is in the form of bubbles. As will be described later, the electrolytic solution 13 may be circulated in the electrochemical reaction device 10, and carbon dioxide may be additionally added to the electrolytic solution 13 by bubbling or the like while the electrolytic solution 13 is circulating.

[0018] The electrolytic solution 13 is caused to flow from the supply port 14 to the discharge port 15, thereby forming a convection current F inside the cell 10 in the X direction. That is, the convection current F is formed so that the electrolytic solution 13 flows in a direction intersecting the direction in which the electrode cells face each other. Therefore, inside the electrochemical reaction device 10, the electrolytic solution 13 comes into contact with the first catalyst 16 of the cathode 11 and the second catalyst 17 of the anode 12, which constitute a pair of separate electrodes, in that order. Then, in the cathode 11, the first catalyst 16 promotes the reduction of carbon dioxide, producing a reduced product of carbon dioxide. The reduced product is carbon monoxide, and the electrochemical reaction that takes place at the cathode is typically as shown in the following formula (A): CO ２ +2H ＋ +2e － →CO+H ２ O (A)

[0019] At the anode 12, an oxygen-containing organic substance is produced from the reduction product (carbon monoxide) produced at the cathode 11 and the reaction substrate in the presence of the second catalyst 17. The oxygen-containing organic substance produced is preferably a carbonyl compound. Examples of carbonyl compounds include organic carbonates, organic oxalates, urea compounds, and carbonyl halides.

[0020] As described above, in this embodiment, the electrochemical reaction device 10 has a simple configuration, yet can synthesize oxygen-containing organic substances such as carbonyl compounds using carbon dioxide as a raw material. Furthermore, since the electrolytic solution 13 generally does not react all of the carbon dioxide contained therein by passing it through the reaction chamber only once, circulating the electrolytic solution 13 can improve the production rate of oxygen-containing organic substances such as carbonyl compounds.

[0021] Furthermore, when carbon dioxide comes into contact with the second catalyst 17, it may inhibit the synthesis of oxygen-containing organic compounds such as carbonyl compounds and cause side reactions. Similarly, when oxidants generated at the anode 12 come into contact with the first catalyst 16, they may inhibit reduction by the first catalyst 16 and cause side reactions. However, in this embodiment, the convection F is oriented so that the electrolytic solution 13 contacts the first catalyst 16 and then the second catalyst 17, thereby reducing the contact of carbon dioxide with the second catalyst 17 and also reducing the contact of oxidized species generated at the anode 12 with the first catalyst 16. Therefore, inhibition of the synthesis of oxygen-containing organic compounds such as carbonyl compounds and the reduction of carbon dioxide and the occurrence of side reactions can be reduced, thereby enabling efficient production of oxygen-containing organic compounds such as carbonyl compounds. Furthermore, in this embodiment, the first and second catalysts 16 and 17 are arranged on the same plane parallel to the X direction, as described above, and therefore the convection F flowing along the X direction is parallel to this same plane. Therefore, the electrolytic solution 13 is efficiently brought into contact with the first and second catalysts 16 and 17 in succession, thereby improving the production rate of oxygen-containing organic substances such as carbonyl compounds.

[0022] Each component used in this embodiment will be described in more detail below. [Cathode] As described above, the cathode 11 is disposed inside the electrochemical reaction device 10 and includes the first catalyst 16. The cathode 11 is an electrode used when electrochemically synthesizing a reduced product such as carbon monoxide from carbon dioxide.

[0023] (First Catalyst) The first catalyst is a reduction catalyst capable of reducing carbon dioxide to a reduced product such as carbon monoxide. The first catalyst is not particularly limited as long as it is a catalyst capable of reducing carbon dioxide to a reduced product such as carbon monoxide, and may, for example, contain a metal element. The metal element may be the metal itself or a metal compound. Examples of the metal element include, but are not limited to, V, Cr, Mn, Fe, Co, Ni, Cu, Sn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Ir, Pt, Au, Hg, Al, Si, In, Sn, Tl, Pb, Bi, Sb, Te, U, Sm, Tb, La, Ce, Zn, Os, and Nd. As the metal compound, inorganic metal compounds and organic metal compounds of these metals can be used, and specific examples thereof include metal halides, metal oxides, metal hydroxides, metal nitrates, metal sulfates, metal acetates, metal phosphates, metal carbonyls, and metal acetylacetonates.

[0024] The metal element used in the first catalyst is preferably a metal element from Groups 7 to 12. Preferred examples include Mn, Fe, Ni, Ru, Co, Rh, Cu, Zn, Ag, Au, Pd, Ir, Pt, and Os, with Co, Fe, Ni, Au, and Ag being more preferred, and Co being particularly preferred. The use of these metal elements makes it easier to increase the efficiency of conversion of carbon dioxide to carbon monoxide, and enhances catalytic activity. The metals used in the metal derivative may be used alone or in combination of two or more.

[0025] The first catalyst may contain a carbon compound in addition to the metal or metal compound. The carbon compound is preferably a conductive carbon compound. More specifically, examples of the carbon compound include mesoporous carbon, activated carbon, carbon black such as ketjen black and acetylene black, graphite, carbon fiber, graphene, and carbon nanotubes. Among these, carbon black is preferred, and conductive carbon black is even more preferred. Furthermore, the carbon compound is preferably porous carbon. When the first catalyst contains a carbon compound, the metal or metal compound may be supported on the carbon compound. Furthermore, the carbon compound may be mixed with a complex containing the metal element and heat-treated to form a catalyst powder. The first catalyst in which the metal or metal compound is supported on the carbon compound may be further supported on an electrode substrate, as described below.

[0026] <<Nitrogen-containing metal catalyst>> The first catalyst is also preferably a catalyst containing a nitrogen element and a metal element (also referred to as a "nitrogen-containing metal catalyst"). Here, the nitrogen element used in the nitrogen-containing metal catalyst is preferably derived from a nitrogen-containing compound described below. Specific examples of the metal element used in the nitrogen-containing metal catalyst are as described above, and the preferred metal elements are also as described above. The use of a nitrogen-containing metal catalyst increases the efficiency of carbon monoxide production, thereby increasing the selectivity of oxygen-containing organic substances such as carbonyl compounds to be synthesized.

[0027] The nitrogen-containing metal catalyst is preferably a catalyst obtained by heat-treating a mixture containing a metal derivative and a nitrogen-containing compound (hereinafter referred to as a "first catalyst raw material mixture"), and is particularly preferably a catalyst obtained by heat-treating a first catalyst raw material mixture containing a metal derivative, a nitrogen-containing compound, and a carbon compound. The heat treatment is typically calcination. The nitrogen-containing metal catalyst is preferably produced by heat-treating the first catalyst raw material mixture, so that metal-nitrogen element bonds derived from the metal derivative and the nitrogen-containing compound are formed in the catalyst. Furthermore, the carbon compound functions as a support in the catalyst, and components derived from the metal derivative and the nitrogen-containing compound are supported on the carbon compound. A nitrogen-containing metal catalyst having the above configuration efficiently reduces carbon dioxide to carbon monoxide, thereby increasing the conversion efficiency.

[0028] The metal element in the metal derivative is as described above. The metal derivative preferably contains a metal ion. The metal derivative may be used, for example, in the form of a metal salt. Examples of metal salts include metal nitrates, metal sulfates, metal chlorides, metal bromides, metal iodides, and metal acetates. Among these, metal nitrates are preferred. Specifically, cobalt nitrate (Co(NO3)2), nickel nitrate (Ni(NO3)2), iron nitrate (Fe(NO3)2), manganese nitrate (Mn(NO3)2), copper nitrate (Cu(NO3)2), and zinc nitrate (Zn(NO3)2) are preferred. The metal salts may be used alone or in combination of two or more.

[0029] The metal content derived from the metal derivative in the first catalyst raw material mixture is, for example, 0.1 mass% to 50 mass% but preferably 0.1 mass% to 10 mass% relative to the total amount of the first catalyst raw material mixture. By ensuring that the content is within this range, the metal is contained in the catalyst without agglomerating, and an appropriate number of catalytic active sites are formed. This facilitates increasing the efficiency of conversion to carbon monoxide. From the standpoint of conversion efficiency and the like, the metal content is more preferably 0.5 mass% or more, even more preferably 1.0 mass% or more, even more preferably 1.5 mass% or more, and more preferably 10 mass% or less, and even more preferably 5 mass% or less. The term "total amount of the first catalyst raw material mixture" refers to the total amount of solids in the first catalyst raw material mixture. If volatile components are blended into the first catalyst raw material mixture during its production process, this refers to the amount excluding the volatile components.

[0030] (Nitrogen-Containing Compound) The nitrogen-containing compound is a compound containing nitrogen, and a component derived from the nitrogen-containing compound may form a bond such as a coordinate bond with a metal element derived from the metal derivative in the nitrogen-containing metal catalyst. Specific examples of the nitrogen-containing compound include compounds containing a nitrogen-containing aromatic ring having a nitrogen element as a constituent element of the aromatic ring. Specific examples of the nitrogen-containing compound include pyridine derivatives, imidazole derivatives, pyrazole derivatives, and triazole derivatives. These compounds may be used alone or in combination of two or more. Among these, from the viewpoint of conversion efficiency, a compound selected from pyridine derivatives, imidazole derivatives, and triazole derivatives is preferred, and a pyridine derivative is particularly preferred. That is, the nitrogen-containing metal catalyst is particularly preferably a catalyst obtained by heat-treating a mixture containing a metal derivative, a pyridine derivative, and a carbon compound.

[0031] (Pyridine Derivative) A pyridine derivative is a compound having a pyridine ring. The pyridine derivative may be a compound having one, two, three, or four or more pyridine rings per molecule. Examples of the pyridine derivative include 4-aminopyridine, 2,2'-bipyridine, 4,4'-diamino-2,2'-bipyridine, etc., and also include polymers having multiple pyridine rings per molecule and a weight-average molecular weight of 1,000 or more. Specific examples of the polymer include polypyridines such as poly(2,5-pyridine) and poly(3,5-pyridine), and polyvinylpyridine, which is a polymer of vinylpyridine. Among these, poly(2,5-pyridine) and poly(4-vinylpyridine) are more preferred, and poly(4-vinylpyridine) is even more preferred. From the viewpoint of conversion efficiency and the like, polyvinylpyridines such as poly(4-vinylpyridine) preferably have a molecular weight of a certain level or higher, and the weight-average molecular weight is, for example, 1,000 or higher, 10,000 or higher, preferably 30,000 or higher, and more preferably 50,000 or higher. From the viewpoint of availability and the like, the weight-average molecular weight is, for example, 200,000 or lower, preferably 100,000 or lower. The weight-average molecular weight is a value measured by gel permeation chromatography (GPC), and polystyrene is preferably used as a standard substance.

[0032] The amount of the nitrogen-containing compound in the first catalyst raw material mixture is preferably adjusted so that the molar ratio of the nitrogen-containing aromatic rings of the nitrogen-containing compound to the metal element of the metal derivative (nitrogen-containing aromatic ring / metal element) is 2 or more and 20 or less. Within this range, the occurrence of side reactions can be suppressed, a catalyst containing an appropriate amount of metal-nitrogen element bonds can be produced, and the conversion efficiency described above can be easily increased. From the viewpoint of conversion efficiency, the molar ratio is more preferably 2 or more, even more preferably 4 or more, and more preferably 18 or less, and more preferably 15 or less. The molar ratio represents the ratio between the number of nitrogen-containing aromatic rings contained in the nitrogen-containing compound and the number of moles of the metal element contained in the metal derivative.

[0033] The carbon compound used in the nitrogen-containing metal catalyst is not particularly limited as long as it can support a heat-treated product (e.g., a calcined product) of a metal derivative and a nitrogen-containing compound such as a pyridine derivative, but a conductive carbon compound is preferred. The use of a conductive carbon compound increases the electrical conductivity at the cathode, making it easier to increase the conversion efficiency to carbon monoxide. Specific examples of carbon compounds are as described above, with carbon black being preferred, and conductive carbon black being even more preferred. The content of the carbon compound in the first catalyst raw material mixture is not particularly limited, but is, for example, 5% by mass or more and 90% by mass or less, preferably 15% by mass or more and 80% by mass or less, and more preferably 20% by mass or more and 70% by mass or less, based on the total amount of the first catalyst raw material mixture. By setting the carbon compound content within the above range, the heat-treated product of the metal derivative and the nitrogen-containing compound can be appropriately supported while maintaining good catalytic activity. The nitrogen-containing metal catalyst is preferably in powder or particulate form. A powder or particulate form makes it easier to support the catalyst on an electrode base material, as described below. Furthermore, the contact area with carbon dioxide is likely to be larger, making it easier to improve the conversion efficiency to carbon monoxide.

[0034] As described above, the nitrogen-containing metal catalyst obtained by heat treatment contains a metal element and a nitrogen element. However, from the viewpoints of selectivity, ease of production, and the like, it is preferable that the metal element is contained in the nitrogen-containing metal catalyst as a metal oxide. As described above, the metal element is preferably cobalt, and therefore the nitrogen-containing metal catalyst preferably contains cobalt oxide. Furthermore, it is particularly preferable that the cobalt oxide contains CoO. Furthermore, as described above, the nitrogen-containing metal catalyst preferably contains a component derived from a nitrogen-containing compound by heat treatment, and in particular, it is preferable that it contains a component derived from a pyridine derivative. Therefore, it is particularly preferable that the nitrogen-containing metal catalyst contains CoO and a component derived from a pyridine derivative. Furthermore, it is preferable that the nitrogen atom derived from the nitrogen-containing compound is coordinated to a metal element such as a cobalt element. The component derived from the nitrogen-containing compound preferably contains a nitrogen-containing aromatic ring structure, specifically a pyridine ring structure, an imidazole ring structure, a pyrazole ring structure, or a triazole ring structure. Among these, a pyridine ring structure, an imidazole ring structure, or a triazole ring structure is preferred, and a pyridine ring structure is particularly preferred. Coordination of cobalt to the nitrogen of the pyridine ring structure is presumed to lower the activation energy of the reaction intermediate, thereby increasing the conversion efficiency. As mentioned above, the nitrogen-containing metal catalyst is produced by heat-treating a mixture containing a nitrogen-containing compound, but the treatment temperature is low. Therefore, the nitrogen-containing aromatic ring contained in the nitrogen-containing compound can be retained in the nitrogen-containing metal catalyst.

[0035] The presence of a nitrogen-containing aromatic ring structure such as a pyridine ring structure in a nitrogen-containing metal catalyst can be confirmed by X-ray photoelectron spectroscopy (XPS) or the like. Furthermore, the coordination of nitrogen elements with metal elements such as cobalt elements can also be confirmed by X-ray photoelectron spectroscopy (XPS). Furthermore, the valence of metal elements, for example, the divalent nature of cobalt oxide, can be confirmed by XPS, X-ray diffraction (XRD), or the like.

[0036] Furthermore, the nitrogen-containing metal catalyst may contain various metal elements as metals in addition to the metal oxides. Thus, when the metal element is cobalt, the catalyst may contain cobalt metal in addition to cobalt oxide. The cobalt metal may, for example, be crystalline. When the nitrogen-containing metal catalyst contains cobalt metal, it preferably has a core-shell structure in which the cobalt metal forms a core and the cobalt oxide is disposed around the core so as to coat the cobalt metal. It is presumed that when the nitrogen-containing metal catalyst has a core-shell structure, the conductivity of the nitrogen-containing metal catalyst is improved, making it easier to improve the carbon dioxide reduction rate, etc. The core-shell structure may be in the form of particles and supported on a carbon compound.

[0037] <<Method for Producing Nitrogen-Containing Metal Catalyst>> The nitrogen-containing metal catalyst can be produced by heat-treating a first catalyst raw material mixture containing a metal derivative and a nitrogen-containing compound such as a pyridine derivative, or a metal derivative, a nitrogen-containing compound, and a carbon compound. In this case, the first catalyst raw material mixture is preferably heated to a heat treatment temperature of 150°C or higher and 550°C or lower. The heat treatment temperature is more preferably 180°C or higher and 500°C or lower, and even more preferably 200°C or higher and 470°C or lower. The heat treatment is preferably carried out in an inert gas atmosphere such as argon or nitrogen gas.

[0038] By heat-treating the first catalyst raw material mixture at the heat treatment temperature described above, a metal-nitrogen bond can be formed and components derived from the metal derivative and the nitrogen-containing compound can be supported on the carbon compound. The heat treatment time (heat treatment time) is not particularly limited, but is, for example, 0.5 hours to 10 hours, preferably 1 hour to 8 hours, and more preferably 2 hours to 5 hours. The first catalyst raw material mixture to be heat-treated is preferably in a powder or particulate form. By being in a powder or particulate form, a powder or particulate catalyst can be obtained by heat treatment. Furthermore, the first catalyst raw material mixture to be heat-treated more preferably consists of a metal derivative, a nitrogen-containing compound, and a carbon compound.

[0039] The first catalyst raw material mixture may be obtained, for example, by preparing a diluted solution of the first catalyst raw material mixture by diluting a metal derivative and a nitrogen-containing compound, or a metal derivative, a nitrogen-containing compound, and a carbon compound, with a dilution solvent, and then drying the diluted solution. The first catalyst raw material mixture may be obtained, for example, in a powder or particulate form. In the diluted solution of the first catalyst raw material mixture, each component (metal derivative, nitrogen-containing compound, and carbon compound) is preferably dispersed or dissolved in the dilution solvent. By dispersing or dissolving each component in the dilution solvent, a first catalyst raw material mixture in which each component is homogeneously mixed can be obtained. The method for obtaining the diluted solution of the first catalyst raw material mixture is not particularly limited. For example, the nitrogen-containing compound may be first added and dispersed in a dispersion medium, and then the metal derivative and, if necessary, the carbon compound may be added to the resulting dispersion.

[0040] The dilution solvent used to dilute the first catalyst raw material mixture may be water or an organic solvent, with organic solvents being preferred. Examples of organic solvents include, but are not limited to, ester solvents, ketone solvents, ether solvents, alcohol solvents, glycol ethers, amide solvents, nitrile solvents, carbonate solvents, halogenated hydrocarbons, hydrocarbons, sulfone solvents, sulfoxides, and formamide. Alternatively, a mixed solvent of an organic solvent and water may be used as the dilution solvent. The concentration of the diluted solution of the first catalyst raw material mixture is not particularly limited, but is, for example, 0.01 to 50 g / L, and preferably 1 to 10 g / L.

[0041] In addition to the above, the first catalyst may be a carbon compound containing at least one of a heteroatom such as nitrogen, a metal, or a metal compound. Examples of such carbon compounds include nitrogen-containing graphite, nitrogen-containing carbon nanotubes, nitrogen-containing graphene, Ni- and nitrogen-containing graphite, Ni- and nitrogen-containing carbon nanotubes, Ni- and nitrogen-containing graphene, Cu- and nitrogen-containing graphite, Cu- and nitrogen-containing carbon nanotubes, Cu- and nitrogen-containing graphene, Co- and nitrogen-containing graphite, Co- and nitrogen-containing carbon nanotubes, and Co- and nitrogen-containing graphene. In the electrochemical reaction device 10, the first catalyst may be used alone or in combination of two or more types.

[0042] (Electrode substrate) The cathode 11 may have an electrode substrate (current collector). The electrode substrate is not particularly limited as long as it is a current collector conventionally used in carbon dioxide reduction electrodes, and examples thereof include carbon substrates, metal substrates, and metal oxide substrates, and it is preferable that the electrode substrate has conductivity. The electrode substrate may also be porous. The substrate is a substrate that constitutes the electrode, and may be, for example, in the form of a sheet or plate, or may be in the form of a layer laminated on the wall surface of a reaction chamber, for example.

[0043] Examples of carbon substrates include porous carbon such as carbon nonwoven fabric. The carbon nonwoven fabric is not particularly limited, and known carbon nonwoven fabrics can be used. For example, commercially available carbon nonwoven fabrics for fuel cells can be used, such as "TORAYCA" (registered trademark) carbon paper and Toray 060 manufactured by Toray Industries, Inc., "AvCarb 1071HCB" manufactured by New Metals and Chemicals, and the BC series manufactured by SGL. Examples of metal substrates include metal mesh, and metals used include gold, silver, platinum, nickel, titanium, and chromium. Examples of metal oxides used in metal oxide substrates include indium oxide, tin oxide, tin-doped indium oxide, and fluorine-doped tin oxide (FTO).

[0044] The first catalyst may be supported on an electrode substrate. The method for supporting the first catalyst on the electrode substrate is not particularly limited. The first catalyst may be attached to the electrode substrate, and it is particularly preferable to attach the nitrogen-containing metal catalyst described above to the electrode substrate. Here, "attached" refers to a state in which the catalyst is physically fixed to the electrode substrate, and the atoms constituting the electrode substrate are not chemically bonded to the atoms constituting the catalyst. Therefore, even if the electrode substrate contains a carbon compound such as porous carbon, the carbon compound itself does not have the metal-nitrogen element bond described above. Furthermore, it does not have a metal-carbon element bond. Here, the carbon element refers to the carbon element constituting the carbon compound such as porous carbon, and the metal refers to a metal element derived from a metal derivative. By attaching the nitrogen-containing metal catalyst to the electrode substrate without chemically bonding it, the conversion efficiency to carbon monoxide is more easily improved and the production thereof is also easier. However, the atoms constituting the first catalyst may be chemically bonded to the atoms constituting the electrode substrate. For example, when the electrode substrate contains a carbon compound such as porous carbon, the carbon compound itself may have the above-mentioned metal-nitrogen element bond or metal-carbon element bond.

[0045] The first catalyst may be supported on the electrode substrate together with a catalyst additive or the like. The catalyst additive also functions as a binder when supporting the catalyst on the electrode substrate. Furthermore, it also functions as an ion conductor, improving the efficiency of the electrochemical reaction. Examples of the catalyst additive include cation-conductive compounds, anion-conductive compounds, and fluorine compounds other than cation-conductive compounds and anion-conductive compounds. Examples of the cation-conductive compound include compounds having a functional group with a Brønsted acid or a salt thereof, which becomes anionized when a hydrogen ion or the like is liberated. Examples of the cation-conductive compound include compounds having at least one functional group such as a sulfonyl group, a phosphate group, a hydroxyl group, or a silicic acid group. Specifically, a commercially available product such as "Nafion" (a trademark of DuPont) can be mentioned.

[0046] Anion-conducting compounds can also be used as catalyst additives. Examples of anion-conducting compounds include compounds having a functional group containing a Bronsted base or a salt thereof, such as a compound having a functional group that becomes cationized when a proton is added. Anion-conducting compounds have excellent conductivity of anions such as hydroxide ions. Specific examples of anion-conducting compounds include compounds having functional groups such as pyridinium groups, imidazolium groups, amino groups, and ammonium groups. Commercially available anion-conducting compounds include "Fumion FAA-3-SOLUT-10" from FuMA-Tech GmbH and "PowerMax NXS125 OH" from Resin Tech Co., Ltd. Furthermore, examples of fluorine compounds other than cation-conducting compounds and anion-conducting compounds include polytetrafluoroethylene (PTFE), tetrafluoroethylene oligomer (TFEO), fluorinated graphite ((CF)n), and fluorinated pitch (FP).

[0047] The catalyst additive may be, for example, in the form of a powder or particles. When a catalyst additive is used, the first catalyst may be mixed with the catalyst additive and the mixture (catalyst composition) may be supported on the electrode substrate. When the catalyst is supported on the electrode substrate together with the catalyst additive, the content of the catalyst additive relative to the total amount of the catalyst additive and the catalyst is preferably 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 45% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less, from the viewpoint of increasing the conversion efficiency of the catalyst.

[0048] The method for supporting the first catalyst on the electrode substrate is not particularly limited, and examples thereof include a method in which a diluted solution obtained by diluting the first catalyst and components other than the catalyst, such as optional catalyst additives, with a dilution solvent is applied to the electrode substrate using various coating devices or by spray coating, and then dried; and a method in which the electrode substrate is immersed in the diluted solution and then dried. In the cathode, the first catalyst (or catalyst composition) may be formed as a layer on the surface of the electrode substrate by applying a coating solution containing the catalyst. The catalyst layer may also be formed in a layer form so that a portion or all of the catalyst layer impregnates the interior of the electrode substrate over a portion or the entire thickness direction of the electrode substrate. For example, the catalyst layer may be formed from the surface to the interior of the electrode substrate. The catalyst layer may also have appropriate voids. The cathode may have a catalyst supported on one surface to form a catalyst layer, but the other surface may not have a catalyst supported on it, or the catalyst may be supported on both surfaces, or a catalyst layer may be formed on both surfaces. The dilution liquid is preferably a dispersion liquid in which the catalyst or the catalyst and components other than the catalyst are dispersed in a dilution solvent, and the dilution solvent may be water or an organic solvent. The organic solvent is as described above, but preferably an alcohol solvent, a ketone solvent, a nitrile solvent, or the like may be used. The dilution liquid may also be a mixed solution of an organic solvent and water.

[0049] [Anode] As described above, the anode 12 is disposed inside the electrochemical reaction device 10, and in this embodiment, includes the second catalyst 17. In this embodiment, the anode 12 is an electrode used when electrochemically synthesizing an oxygen-containing organic substance such as a carbonyl compound from a reduced product (carbon monoxide).

[0050] (Second Catalyst) The second catalyst is not particularly limited as long as it promotes the electrochemical reaction of synthesizing an oxygen-containing organic substance such as a carbonyl compound from carbon monoxide and a reaction substrate. However, it may contain a metal element, and preferably contains a metal element selected from Groups 8 to 11. Using a Group 8 to 11 element as the catalyst facilitates the electrochemical synthesis of a carbonyl compound, particularly an organic carbonate, from carbon monoxide with high selectivity. Examples of carbonyl compounds include organic carbonates, organic oxalates, urea-based compounds, and carbonyl halides. Among these, at least one of an organic carbonate and an organic oxalate is preferred, with organic carbonate being more preferred. Therefore, the second catalyst is preferably a catalyst that promotes the reaction of synthesizing an organic carbonate, an organic oxalate, or both, and more preferably a catalyst that promotes at least the reaction of synthesizing an organic carbonate.

[0051] Specific examples of Group 8 to Group 11 elements used in the second catalyst include Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au. Among these, Co, Ni, Cu, Rh, Pd, Ag, Ir, Au, and Pt are preferred, with Pd, Au, Ag, and Ir being more preferred. Use of the above-mentioned elements facilitates electrochemical synthesis of organic carbonates, organic oxalates, or both from carbon monoxide with high selectivity. From these perspectives, Au and Pd are more preferred as the metal element contained in the catalyst, with Pd being particularly preferred.

[0052] The metal element used in the second catalyst may be used alone or in combination of two or more. When two or more elements are used in combination, two or more metal elements selected from Groups 8 to 11 may be used in combination, or a metal element from Groups 8 to 11 may be used in combination with a metal element other than Groups 8 to 11. The metal element other than Groups 8 to 11 is preferably a metal element from Period 4, but may also be a metal element other than Period 4. Specifically, it is preferable to combine Au with at least one selected from Ti, Mn, Fe, Co, Ni, Cu, and Zn. It is also preferable to combine Pd with at least one selected from Ti, Co, Ni, Cr, Mn, Fe, Cu, Zn, Ru, Rh, Ag, Ir, Pt, Au, and Sn. It is also preferable to combine Ir with at least one selected from Au, Rh, and Ru. Such a combination makes it possible to maintain high selectivity in synthesizing carbonyl compounds while reducing the amount of precious metal used.

[0053] From the viewpoint of improving selectivity, when two or more metal elements are used in combination, the second catalyst preferably contains at least two metal elements selected from Groups 8 to 11. Among these, it is more preferable to use either Pd or Ir in combination with at least one element selected from Groups 8 to 11 other than Pd or Ir. Specifically, a combination of Pd with at least one element selected from Ag, Au, Pt, Ir, and Cu, or a combination of Ir with one element selected from Au, Rh, and Ru is more preferable.

[0054] When two or more metals are used in combination, the content of each metal may be appropriately set. When Pd is used, the content of Pd is, for example, 10 mol% to 99 mol%, and from the viewpoint of selectivity, preferably 25 mol% to 95 mol%. In this case, the content of metals other than Pd (e.g., at least one selected from Ag, Au, Pt, Ir, and Cu) is, for example, 1 mol% to 90 mol%, and preferably 5 mol% to 75 mol%. When Ir is used in combination with Pd, the content of Ir is, for example, 5 mol% to 99 mol%, and from the viewpoint of selectivity, preferably 10 mol% to 95 mol%, and more preferably 25 mol% to 90 mol%. In this case, the content of metals other than Ir (e.g., at least one selected from Au, Rh, and Ru) is, for example, 1 mol% to 95 mol%, and preferably 5 mol% to 90 mol%, and more preferably 10 mol% to 75 mol%. The metal content here refers to the ratio to the total amount of metals contained in the catalyst.

[0055] The second catalyst may be an active particle-containing catalyst, a metal salt, or a combination of these. The use of an active particle-containing catalyst or a metal salt allows carbonyl compounds, particularly organic carbonates, to be produced from carbon monoxide with high conversion efficiency. Of these, the use of an active particle-containing catalyst is particularly preferred.

[0056] <<Active particle-containing catalyst>> The active particles in the active particle-containing catalyst have catalytic activity to promote the reaction when carbon monoxide is electrochemically synthesized into a carbonyl compound. The active particles containing a metal element are not particularly limited as long as they contain a metal element, and may be composed of a metal oxide, a metal itself, or both a metal oxide and a metal. The metal elements used in the active particles are as described above.

[0057] In the second catalyst, the active particles are, for example, in the form of fine particles. Although not particularly limited, they are preferably nano-order particles, preferably having an average particle diameter of 100 nm or less, more preferably 1 nm to 40 nm. By having the above particle diameter and nanostructuring the active particles, the active area increases, making it easier to improve various performances of the catalyst. Note that the particle diameter refers to the area-equivalent circle diameter, which is calculated by determining the area of ​​each particle in image observation using TEM-EDX or the like, and then calculating the diameter from the area of ​​each particle when it is assumed to be a circle.

[0058] Furthermore, it is preferable that the active particle-containing catalyst further contains a support, and that the active particles are supported on the support. Supports used in the active particle-containing catalyst are not particularly limited, but include carbon, silica, aluminum oxide, zirconium oxide, etc., with carbon, silica, and aluminum oxide being preferred from the viewpoint of synthesizing carbonyl compounds from carbon monoxide with high selectivity. Furthermore, it is preferable that the support is porous. Supports used in the active particle-containing catalyst are not particularly limited, but porous carbon is preferred from the viewpoint of synthesizing carbonyl compounds from carbon monoxide with high selectivity. Therefore, it is preferable that the active particle-containing catalyst is a catalyst having active particles containing metal elements and porous carbon supporting the active particles. The porous carbon support allows the reaction substrates described below to diffuse appropriately in the catalyst, making it easier to improve the selectivity and reaction efficiency when synthesizing carbonyl compounds. It is preferable that the carbon be porous, and similarly, it is preferable that the silica and aluminum oxide be porous.

[0059] As described below, an active particle-containing catalyst having a support such as porous carbon can be produced by mixing a metal precursor with a support (e.g., porous carbon, silica, or aluminum oxide, preferably porous carbon) and heat treating the mixture. The metal precursor is converted into active particles by heat treatment, and the active particles are supported on a support such as porous carbon. The porous carbon used in the active particle-containing catalyst is not particularly limited, but is preferably made of a powder or particulate carbon compound, and therefore the active particle-containing catalyst is also preferably powder or particulate. When the active particle-containing catalyst is powder or particulate, it is easier to disperse it in the electrolyte and the contact area with carbon monoxide is likely to be larger, which makes it easier to improve the selectivity and reaction efficiency when synthesizing carbonyl compounds. Supports other than porous carbon are also preferably powder or particulate.

[0060] The BET specific surface area of ​​the porous carbon used in the active particle-containing catalyst is, for example, 10 m 2 / g or more 3000m 2 / g or less, preferably 100m 2 / g or more 1500m 2 / g or less. The BET specific surface area can be measured by gas adsorption analysis. The average primary particle diameter of the porous carbon used in the active particle-containing catalyst is, for example, 1 nm or more and 1000 nm or less, preferably 10 nm or more and 300 nm or less. The average primary particle diameter of the porous carbon can be measured, for example, by observation using an electron microscope. Specifically, there is mentioned a method of determining the area of ​​each particle and calculating the diameter from the area assuming each particle to be a circle to determine the area-equivalent circle diameter. The average pore diameter of the porous carbon is, for example, 0.5 nm or more and 100 nm or less, preferably 1 nm or more and 50 nm or less. The average pore diameter of the porous carbon can be measured by gas adsorption analysis.

[0061] The porous carbon used in the active particle-containing catalyst is not particularly limited as long as it can support the active particles, but a conductive carbon compound is preferred. The use of a conductive carbon compound increases the electrical conductivity of the electrode, making it easier to improve reaction efficiency, etc. More specific examples of porous carbon include mesoporous carbon, activated carbon, carbon black such as ketjen black and acetylene black, carbon nanotubes, graphite, graphene, etc., of which carbon black is preferred, and conductive carbon black is even more preferred.

[0062] The active particle-containing catalyst may further contain a component derived from a nitrogen-containing compound. The active particle-containing catalyst containing a component derived from a nitrogen-containing compound is likely to improve the conversion efficiency, selectivity, and other properties of the carbonyl compound during synthesis. The component derived from the nitrogen-containing compound preferably contains a nitrogen element, and the nitrogen element may be coordinated to a metal element (e.g., a metal element constituting a metal oxide) constituting the active particle, forming a metal-nitrogen bond through a coordinate bond. The component derived from the nitrogen-containing compound may be supported on a support such as porous carbon, silica, or aluminum oxide, preferably porous carbon. That is, the component derived from the nitrogen-containing compound may be coordinated to a metal element constituting the active particle and supported on a support such as porous carbon. The nitrogen-containing compound preferably has a nitrogen-containing aromatic ring structure in which nitrogen is contained in the aromatic ring. When the active particle-containing catalyst contains a component derived from a nitrogen-containing compound, it can be obtained by heat-treating a mixture of a metal precursor, porous carbon, and the nitrogen-containing compound, as described below. Therefore, the component derived from the nitrogen-containing compound is a component obtained by heat-treating the nitrogen-containing compound. By lowering the heat treatment temperature as described below, the nitrogen-containing aromatic ring structure formed by the nitrogen-containing compound remains in the catalyst. The components derived from the nitrogen-containing compound in the active particle-containing catalyst preferably have a nitrogen-containing aromatic ring structure. Details of the nitrogen-containing compound and the nitrogen-containing aromatic ring structure are as described in the first catalyst.

[0063] <<Method for Producing an Active Particle-Containing Catalyst>> Next, a method for producing an active particle-containing catalyst will be described. The above-mentioned active particle-containing catalyst may be obtained by heat-treating at least a metal precursor. Preferably, the metal precursor is mixed with a support such as porous carbon, silica, or aluminum oxide, more preferably, the metal precursor is mixed with porous carbon, and the mixture containing the metal precursor and the support is heat-treated. Note that the metal precursor or the mixture containing the metal precursor and porous carbon, which is the raw material for the active particle-containing catalyst, is also referred to as the second catalyst raw material hereinafter. The heat treatment is typically calcination. Furthermore, when the active particle-containing catalyst contains a component derived from a nitrogen-containing compound, the nitrogen-containing compound may be further mixed with the metal precursor and porous carbon, and the second catalyst raw material may contain the metal precursor, porous carbon, and nitrogen-containing compound.

[0064] The metal precursor is a compound that becomes the above-mentioned active particles by heat treatment. Therefore, the metal precursor may be a precursor containing a metal element selected from the above-mentioned Group 8 to Group 11 elements, and suitable metal elements are also as described above. The metal element used in the metal precursor may be used alone or in combination of two or more types. When two or more types are used in combination, the combination of metal elements is as described above. When two or more types of metal precursors are used in combination, the active particle-containing catalyst may be obtained by mixing two or more types of metal precursors, or mixing two or more types of metal precursors with porous carbon, and then heat treating the mixture; therefore, two or more types of metal precursors may be contained in the second catalyst raw material.

[0065] The metal precursor preferably contains a metal ion. The metal precursor may be used, for example, in the form of a metal salt. Examples of metal salts include metal nitrates, metal sulfates, metal chlorides, metal bromides, metal iodides, and metal acetates. Among these, metal chlorides and metal nitrates are preferred, and metal nitrates are more preferred from the viewpoint of forming suitable active particles. Specific examples of the metal nitrates and metal chlorides used in the metal precursor are the same as the metal salts used as the second catalyst described below, and therefore, further explanation is omitted. The metal salt may also be a hydrate. The porous carbon and nitrogen-containing compound used as raw materials in this production method are as described for the first catalyst above.

[0066] The content of the metal derived from the metal precursor in the second catalyst raw material is preferably 0.1% by mass or more and 70% by mass or less, and more preferably 2% by mass or more and 50% by mass or less, based on the total amount of the second catalyst raw material. By setting the content within the above range, the metal is contained in the catalyst without agglomerating, and an appropriate amount of catalytic active sites is formed. This makes it easier to increase the selectivity when synthesizing carbonyl compounds, and also increases the reaction efficiency.

[0067] The content of the support, such as porous carbon, in the second catalyst raw material is not particularly limited, but is, for example, 10% by mass to 95% by mass, preferably 20% by mass to 85% by mass, and more preferably 30% by mass to 80% by mass. By setting the content of the support, such as porous carbon, within the above range, it is possible to appropriately support the active particles and components derived from the nitrogen-containing compound while maintaining good catalytic activity. When a nitrogen-containing compound is used, the amount of the nitrogen-containing compound blended in the second catalyst raw material is preferably adjusted so that the molar ratio of the nitrogen-containing aromatic ring of the nitrogen-containing compound to the metal element derived from the metal precursor (nitrogen-containing aromatic ring / metal element) is 0.1 to 30, more preferably 1 to 20.

[0068] The temperature at which the second catalyst raw material is heat-treated is preferably 150°C or higher and 800°C or lower, more preferably 180°C or higher and 550°C or lower, and even more preferably 200°C or higher and 380°C or lower. The heat-treatment time is not particularly limited, but is, for example, 0.25 hours or higher and 10 hours or lower, preferably 0.5 hours or higher and 8 hours or lower, and more preferably 1 hour or higher and 5 hours or lower. The heat treatment may be carried out in an inert gas atmosphere such as argon or nitrogen gas, or in a reducing atmosphere such as hydrogen.

[0069] The second catalyst raw material to be heat-treated is preferably in powder or particulate form. If the second catalyst raw material is in powder or particulate form, the catalyst obtained by heat treatment can also be in powder or particulate form. Furthermore, the second catalyst raw material to be heat-treated more preferably consists of a metal precursor and porous carbon, or a metal precursor, porous carbon, and a nitrogen-containing compound. The second catalyst raw material may be obtained, for example, by preparing a diluted solution of the second catalyst raw material and drying the diluted solution. In the diluted solution of the second catalyst raw material, each component (metal precursor and porous carbon, or metal precursor, nitrogen-containing compound, and porous carbon) is preferably dispersed or dissolved in a dilution solvent. By dispersing or dissolving each component in a dilution solvent, a second catalyst raw material in which each component is homogeneously mixed can be obtained. The dilution solvent used to dilute the second catalyst raw material can be water or an organic solvent, preferably water. Ammonia water or the like may also be used as the dilution solvent. Specific examples of organic solvents are as described above. Alternatively, a mixed solvent of an organic solvent and water may also be used as the dilution solvent. The concentration of the diluted solution of the second catalyst raw material is not particularly limited, but is, for example, 0.01 to 25 g / L, preferably 0.1 to 5 g / L.

[0070] Metal salts used as the second catalyst include metal nitrates, metal sulfates, metal chlorides, metal bromides, metal iodides, and metal acetates. Among these, metal chlorides and metal nitrates are preferred, and metal chlorides are more preferred. Specifically, metal nitrates include cobalt nitrate (Co(NO)), nickel nitrate (Ni(NO)), copper nitrate (Cu(NO)), rhodium nitrate (Rh(NO)), and the like. ３), palladium nitrate (Pd(NO3) ２ ), silver nitrate (AgNO ３ ), iridium nitrate (Ir(NO3) ４ ), platinum nitrate (Pt(NO3) ４ ), gold nitrate (AuNO3), ruthenium nitrate (Ru(NO3) ３ ), iron nitrate (Fe(NO ３ ) ３ ), manganese nitrate (Mn(NO ３ ) ２ ), zinc nitrate (Zn(NO ３ ) ２ ), chromium nitrate (Cr(NO ３ ) 　３ ), tin nitrate (Sn(NO ３ ) ４ ) and the like. Specific examples of metal chlorides include PdCl ２ , RuCl ３ , IrCl ３ , PtCl ４ , AuCl ３ Also, HAuCl ４ Among these, PdCl ２ , HAuCl ４ , Ir(III)Cl ３ The second catalyst may be used alone or in combination of two or more.

[0071] (Electrode Base Material) In this embodiment, the anode 17 may include an electrode base material (current collector). Details of the electrode base material (current collector) are the same as those described for the cathode, and therefore will not be described here. The current collector of the anode 17 may be made of the same material as the current collector of the cathode, or may be made of a different material. In this embodiment, the second catalyst may be supported on the electrode base material. The second catalyst may also be supported on the electrode base material together with a catalyst additive or the like. The method for supporting the second catalyst, or the second catalyst and the catalyst additive (catalyst composition) on the electrode base material is not particularly limited, but is the same as that described for the method for supporting the first catalyst on the electrode base material, and therefore will not be described here.

[0072] [Electrolyte] In this embodiment, the electrolyte contains a reaction substrate and an electrolyte. (Electrolyte) The electrolyte preferably contains a redox species as the electrolyte. The redox species may be dissolved in the reaction substrate or a mixture of the reaction substrate and an electrolyte solvent, which will be described later. The redox species may have a molecular or ionic size smaller than that of the reaction substrate, such as an alcohol-based compound, which will be described later, and have redox activity. Specific examples of the redox species include halide salts such as metal halide salts, organic redox, and complex redox. Among these, halide salts are preferred from the viewpoint of improving selectivity and productivity. In this embodiment, the electrolyte contains a redox species as the electrolyte, which generates a redox mediator (an oxidant such as a halogen) at the anode. This redox mediator allows carbon monoxide and the reaction substrate to be efficiently used to generate a carbonyl compound in the presence of the second catalyst. Furthermore, when the redox mediator comes into contact with the first catalyst, it inhibits the reduction reaction of carbon dioxide. However, in this embodiment, the electrolyte has convection, and the direction of the convection is controlled so that it contacts the first catalyst and then the second catalyst. This makes it difficult for the redox mediator to come into contact with the first catalyst, and therefore makes it difficult for the reduction reaction of carbon dioxide to be inhibited.

[0073] Examples of halide salts include metal halide salts, such as lithium halide salts (lithium chloride, lithium bromide, lithium iodide, etc.), sodium halide salts (sodium chloride, sodium bromide, sodium iodide, etc.), potassium halide salts (potassium chloride, potassium bromide, potassium iodide, etc.), cesium halide salts (cesium chloride, cesium bromide, cesium iodide, etc.), and ammonium halide salts (ammonium chloride, ammonium bromide, ammonium iodide, etc.).

[0074] Examples of organic redox compounds include TEMPO-based radical compounds such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MeO-TEMPO), and azaadamantane-N-oxyl (AZADO). Examples of complex redox compounds include palladium acetylacetonate (Pd(OAc) ２ ), tetrakis(triphenylphosphine)palladium (Pd(PPh ３ ) ４ complex), tris(2,2'-bipyridine)cobalt (Co(bpy) ３ complex), tris[1,3-bis(4-pyridyl)propane]cobalt (Co(bpp) ３ complexes) and other cobalt-based complexes.

[0075] Among the above, metal halide salts are preferred as redox species from the viewpoint of increasing the selectivity of carbonyl compounds, with metal chloride salts and metal bromide salts being more preferred, and metal bromide salts being even more preferred. Therefore, the electrolyte contains halogen ions such as chloride ions and bromide ions as redox ions, with bromide ions being particularly preferred. Preferred examples of metal chloride salts include lithium chloride, potassium chloride, and sodium chloride, with sodium chloride being preferred from the viewpoint of easy availability. Preferred examples of metal bromide salts include lithium bromide, potassium bromide, and sodium bromide, with sodium bromide being particularly preferred from the viewpoint of increasing the selectivity of carbonyl compounds. The redox species may be used alone or in combination of two or more. The concentration of the redox species in the electrolyte is not particularly limited, and may be adjusted to a level at which the synthesis of oxygen-containing organic substances such as carbonyl compounds proceeds appropriately. A specific concentration of the redox species is, for example, 0.001 M or more and 5.0 M or less, preferably 0.01 M or more and 1.0 M or less, and more preferably 0.05 M or more and 0.5 M or less.

[0076] (Reaction Substrate) The reaction substrate is a compound that serves as a raw material for an oxygen-containing organic substance such as a carbonyl compound. The reaction substrate is changed depending on the type of target product to be produced. For example, when producing an organic carbonate, an organic oxalate, or both, an alcohol-based compound may be used as the reaction substrate. When producing a urea-based compound, an amine-based compound may be used as the reaction substrate. When producing a carbonyl halide such as phosgene, as will be described later, a halogen or a metal halide salt may be used as the reaction substrate. Of the above, it is preferable to use an alcohol-based compound as the reaction substrate.

[0077] (Alcohol-based Compound) An alcohol-based compound is a reaction substrate that reacts with carbon monoxide in an electrochemical reaction device to produce an organic carbonate, an organic oxalate, or both. The alcohol-based compound may be solid, liquid, or gaseous in the environment in which the electrochemical reaction occurs in the electrochemical reaction device, but is preferably liquid. A liquid alcohol-based compound can be easily filled into an electrochemical reaction device without using a solvent for the electrolyte, which will be described later. The alcohol-based compound is a compound having at least one hydroxyl group, and more specifically, a compound represented by the following general formula (1). In this specification, the term "alcohol-based compound" is a concept that also includes aromatic hydroxy compounds in which a hydroxyl group is directly bonded to an aromatic ring such as a benzene ring, as will be described later, such as phenol.

[0078] ROH (1) (R represents an organic group having 1 to 15 carbon atoms.) The organic group having 1 to 15 carbon atoms represented by R in the above general formula (1) includes a hydrocarbon group having 1 to 15 carbon atoms. Examples of the hydrocarbon group include an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 2 to 15 carbon atoms, and an aryl group having 6 to 15 carbon atoms. Examples of the alkyl group having 1 to 15 carbon atoms include a methyl group, an ethyl group, various propyl groups, various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various dodecyl groups, and various pentadecyl groups. Examples of alkenyl groups having 2 to 15 carbon atoms include vinyl groups, various propynyl groups, various butynyl groups, various pentynyl groups, various hexenyl groups, various heptenyl groups, various octenyl groups, various nonenyl groups, various decenyl groups, various dodecenyl groups, and various pentadecenyl groups. The term "various" refers to various isomers including n-, sec-, tert-, and iso-. The alkyl or alkenyl group may be linear, branched, or cyclic. Examples of aryl groups having 6 to 15 carbon atoms include phenyl and naphthyl groups. The hydrocarbon groups described above may have a substituent, and in such cases, the total carbon number, including the substituent, is 1 to 15.

[0079] Furthermore, the organic group having 1 to 15 carbon atoms in general formula (1) may contain a heteroatom such as a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, or a halogen atom. Among these, an oxygen atom is preferred. When an oxygen atom is contained, the oxygen atom is preferably either a hydroxyl group or an oxygen atom of an ether bond. Therefore, it is preferable that R is a hydrocarbon group having at least either a hydroxyl group or an ether bond. It is also preferable that R has one hydroxyl group. In other words, the alcohol-based compound may have two hydroxyl groups. More specifically, the alcohol-based compound having two hydroxyl groups is preferably a group represented by the following formula (1-1): HO-R 11 —OH (1-1) In addition, in formula (1-1), R 11 is a divalent saturated hydrocarbon group having 2 to 15 carbon atoms, and R 11The number of carbon atoms is preferably 2 to 4, more preferably 2 to 3.

[0080] As the compound represented by the general formula (1), among the above, R is preferably an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, or an aryl group having 6 to 8 carbon atoms. 11 Also preferred are those having 2 to 4 carbon atoms. Among these, compounds in which R is an alkyl group or an aryl group are more preferred, and particularly compounds in which R is an alkyl group are even more preferred. The alkyl group more preferably has 1 to 3 carbon atoms, even more preferably has 1 or 2 carbon atoms, and most preferably has 1 carbon atom. Specifically, from the viewpoints of reactivity and production efficiency, methanol, ethanol, phenol, 1-propanol, ethylene glycol, propylene glycol, etc. are preferred, and among these, methanol is more preferred. The alcohol-based compounds may be used alone or in combination of two or more types.

[0081] When an alcohol-based compound is used as the reaction substrate, a reaction (also referred to as a first reaction) in which an organic carbonate is produced from carbon monoxide and the alcohol-based compound generally occurs in the electrochemical reaction device 10. However, a reaction (also referred to as a second reaction) in which an organic oxalate is produced from carbon monoxide and the alcohol-based compound may also occur, and both the first and second reactions occur, but it is preferable that at least the first reaction occurs.

[0082] The first reaction is a carbonylation reaction in which an organic carbonate is produced. Specifically, the organic carbonate ((RO)) is produced by the reaction shown in the following formula (i): ２ CO) is produced. CO + 2ROH → (RO) ２ CO + 2H ＋ +2e －(i) In (i), R is the same as above, but preferably R is an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, or an aryl group having 6 to 8 carbon atoms, more preferably an alkyl group or an aryl group, and even more preferably an alkyl group. The alkyl group preferably has 1 to 3 carbon atoms, even more preferably has 1 or 2 carbon atoms, and most preferably has 1 carbon atom. However, as mentioned above, two or more alcohol compounds may be used in combination, and in that case, (RO) ２ Two R's in one molecule of CO may be different from each other.

[0083] When ROH is represented by the general formula (1-1), an organic carbonate is produced by the reaction shown in the following formula (ii). In addition, in formula (ii), R 11 is the same as above, but R 11 The number of carbon atoms is preferably 2 to 4, more preferably 2 to 3, and even more preferably 2.

[0084] Specific preferred organic carbonates include one or more selected from dimethyl carbonate, diethyl carbonate, ethylene carbonate, dipropyl carbonate, propylene carbonate, diphenyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate, and among these, dimethyl carbonate is more preferred.

[0085] The second reaction is a reaction in which carbon monoxide and an alcohol-based compound produce an organic oxalate represented by the following formula (2): Specifically, the organic oxalate represented by formula (2) may be synthesized by the reaction represented by formula (iii) below. (In formula (2), R is the same as above. However, two R in one molecule may be the same or different.) (In formula (iii), R is the same as above.)

[0086] When ROH is represented by the general formula (1-1), an organic oxalate represented by the following formula (2-1) is produced by the reaction represented by the following formula (iv). (In addition, in formula (2-1), R １１ is the same as above.) (In the formula (iv), R １１ is the same as above.)

[0087] Specific preferred organic oxalates include one or more selected from dimethyl oxalate, diethyl oxalate, ethylene oxalate, dipropyl oxalate, propylene oxalate, diphenyl oxalate, ethyl methyl oxalate, methyl propyl oxalate, and ethyl propyl oxalate. Among these, dimethyl oxalate is more preferred.

[0088] (Amine Compound) The amine compound used as the reaction substrate is an organic compound having at least one amino group, and is preferably a compound represented by the following formula (3): ２ NH ２ (3) (R ２ represents an organic group having 1 to 15 carbon atoms. 2 The organic group having 1 to 15 carbon atoms represented by R includes a hydrocarbon group having 1 to 15 carbon atoms, and specific descriptions thereof are given in the above R 1 The organic group having 1 to 15 carbon atoms in formula (3) may contain a heteroatom such as a nitrogen atom, an oxygen atom, a sulfur atom, or a phosphorus atom. Of these, a nitrogen atom is preferred, and the nitrogen atom is preferably the nitrogen atom of an amino group. Therefore, R ２ is preferably a hydrocarbon group having an amino group. More specifically, an aminoalkyl group having 1 to 15 carbon atoms is preferred. By using an amine compound as a reaction substrate, a urea compound having a urea bond (—NH—CO—NH—) can be synthesized.

[0089] (Halogen) When the target product is a carbonyl halide, a halogen can be used as the reaction substrate. Examples of halogen include chlorine and bromine. If the halogen is chlorine, phosgene is obtained, and if the halogen is bromine, carbonyl bromide is obtained. Alternatively, instead of a halogen, a halogen may be generated by an electrochemical reaction in the electrochemical reaction device 10 from a metal halide salt used as an electrolyte. Therefore, when producing a carbonyl halide, a metal halide salt may be used as both the reaction substrate and the electrolyte (redox species).

[0090] [Solvent for Electrolyte] When the above-mentioned reaction substrate is a solid or gas, or when it is necessary to improve the solubility of the redox species, the electrolyte may further contain a solvent (also referred to as "solvent for electrolyte"). In this case, the reaction substrate may be filled into the electrochemical reaction device as a mixed solution with the solvent. Of course, even when the reaction substrate is a liquid, it may be filled as a mixed solution with the solvent.

[0091] The solvent for the electrolyte can be appropriately selected from solvents commonly used in electrochemical reactions, and examples thereof include nitrile solvents such as acetonitrile, carbonate solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, lactone solvents such as γ-butyrolactone, ether solvents such as 1,2-dimethoxyethane, 1-ethoxy-2-methoxyethane, 1,2-diethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran, phosphate ester solvents, phosphoric acids, sulfolane solvents, pyrrolidones, etc. These solvents may be used alone or in combination of two or more.

[0092] Second Embodiment Next, a second embodiment of the present invention will be described. FIG. 2 shows an electrochemical reaction device (electrochemical cell) 20 according to a second embodiment of the present invention. In the first embodiment, the first and second catalysts were arranged on the same plane, and the convection current F flowed parallel to that plane. However, in this embodiment, the first and second catalysts 26, 27 are arranged facing each other, and the convection current F is formed in a direction in which the electrolytic solution 23 contacts the first and second catalysts 26, 27 in that order. Hereinafter, differences between the second embodiment and the first embodiment will be described, and portions that will not be described are similar to those of the first embodiment.

[0093] In the second embodiment, an anode 22 and a cathode 21 are provided on wall surfaces 20A, 20B of the reaction chamber 20 that face each other in the Y direction. A voltage is applied between the anode 22 and the cathode 21 from a power supply. As in the first embodiment, the anode 22 and the cathode 21 have a second catalyst 27 and a first catalyst 26, respectively. Therefore, the cathode 21 and the anode 22, i.e., the first catalyst 26 and the second catalyst 27, face each other in the Y direction.

[0094] Furthermore, an outlet 25 and a supply port 24 are provided on each of the wall surfaces 20A, 20B facing each other in the Y direction. As a result, the supply port 24 is positioned on the cathode 21 (first catalyst) side, and the outlet 25 is positioned on the anode 22 (second catalyst) side, with a mutual offset in the Y direction. The electrolytic solution 23 supplied from the supply port 24 is discharged from the outlet 25, so that a convection F of the electrolytic solution 23 is formed along the Y direction (i.e., from the cathode 21 toward the anode 22), and the electrolytic solution 23 comes into contact with the first catalyst 26 and then the second catalyst 27. Therefore, the first catalyst 26 promotes the reduction of carbon dioxide, and a reduced product of carbon dioxide (carbon monoxide) is produced at the cathode 21. Meanwhile, at the anode 22, the second catalyst 27 produces oxygen-containing organic compounds, such as carbonyl compounds, from the reduced product (carbon monoxide) produced at the cathode 21 and the reaction substrate.

[0095] As described above, even in this embodiment, the electrochemical reaction device 20 has a simple configuration, yet can efficiently synthesize oxygen-containing organic compounds, such as carbonyl compounds, from carbon dioxide. Furthermore, by circulating the electrolyte 23, the production rate of oxygen-containing organic compounds can be improved. The supply inlet 24 and the outlet 25 are located outside the cathode 21 and the anode 22, sandwiching them when viewed in the Y direction. This arrangement allows the electrolyte 23 flowing due to convection F to more easily contact the first catalyst 26 of the cathode 21 and the second catalyst 27 of the anode 22, further improving the production rate of oxygen-containing organic compounds. However, the positions of the supply inlet 24 and the outlet 25 are not limited to the configuration shown in FIG. 2 , and are not particularly limited as long as the direction of the convection F is formed so that the electrolyte 23 contacts the first catalyst 26 and the second catalyst 27 in this order.

[0096] <Third Embodiment> Fig. 3 shows an electrochemical reaction device (electrochemical cell) 30 according to a third embodiment of the present invention. Hereinafter, in the third embodiment, differences from the second embodiment will be described, and portions for which description will be omitted are the same as those in the second embodiment. In the third embodiment, the difference from the second embodiment is that the electrochemical reaction device 30 includes a rectifying layer 31. Note that in the third embodiment, the same components as those in the second embodiment are denoted by the same reference numerals.

[0097] The rectifying layer 31 is disposed between the cathode 21 (i.e., the first catalyst 26) and the anode 22 (i.e., the second catalyst 27) so as to separate the cathode 21 region from the anode 22 region. The rectifying layer 31 regulates the flow direction of convection F of the electrolyte 23. The rectifying layer 31 may be, for example, an insulating mesh filter, specifically a resin mesh filter. Resin mesh filters include those in which holes are appropriately formed in a resin sheet by punching or the like. The shape of the holes is not particularly limited and may be circular, elliptical, or polygonal, such as triangular, rectangular, or pentagonal, or may be other shapes. The mesh (opening size) is not particularly limited, but the hole diameter is preferably 0.1 μm or more and 5000 μm or less, and more preferably 1 μm or more and 3000 μm or less. Note that the "diameter of a hole" refers to the longest diameter (major axis) of the hole when the hole is not circular. The same applies hereinafter. Examples of the resin sheet include a fluororesin sheet such as polytetrafluoroethylene (PTFE) or perfluoroalkoxy fluororesin (PFA). In this embodiment, the rectifying layer 31 controls the flow of the convection current F so that it flows along the Y direction, i.e., from the cathode 21 to the anode 22. Therefore, in this embodiment, the provision of the rectifying layer 31 makes it easier for the convection current F to form along the Y direction, which makes it easier for the electrolytic solution 23 to flow so as to come into contact with the first catalyst 26 and then the second catalyst 27, thereby enabling more efficient production of oxygen-containing organic matter.

[0098] The rectifying layer is not limited to a mesh filter and may be, for example, a film having non-mesh-shaped holes formed in the partition wall. For example, the rectifying layer may be a film having one or several holes formed only in a portion of the partition wall. More specifically, the rectifying layer may be a resin sheet having one or several holes formed in a portion of the resin sheet. In this case, the size of the holes may be, for example, 0.1 μm or more and 5000 μm or less in diameter, preferably 1 μm or more and 3000 μm or less in diameter. An electrochemical reaction device (electrochemical cell) 30A using such a rectifying layer 32 is shown in FIG. 4.

[0099] In the example shown in FIG. 4 , the rectifying layer 32 has holes 32A formed in a portion thereof, and the holes 32A are located away from the supply port 24 and the exhaust port 25. Specifically, when viewed in the Y direction, the holes 32A and the supply port 24 are preferably arranged to sandwich a portion (preferably, 50% or more of the portion along the X direction) or the entire portion of the cathode 21 along the X direction. Similarly, the holes 32A and the exhaust port 25 are preferably arranged to sandwich a portion (preferably, 50% or more of the portion along the X direction) or the entire portion of the anode 21 along the X direction. This arrangement of the holes 32A, the supply port 24, and the exhaust port 25 allows the convection F of the electrolytic solution 23 to contact large portions of the first catalyst 26 of the cathode 21 and the second catalyst 27 of the anode 22. Therefore, even in the example shown in FIG. 4 , carbon dioxide reduction and oxygen-containing organic matter production can be efficiently performed.

[0100] <Fourth Embodiment> Fig. 5 shows an electrochemical reaction device (electrochemical cell) 40 according to a fourth embodiment of the present invention. Hereinafter, in the fourth embodiment, differences from the second embodiment will be described, and parts that will not be described are the same as those in the second embodiment. In the fourth embodiment, the same components as those in the second embodiment are denoted by the same reference numerals. In the fourth embodiment, the electrochemical reaction device 40 is different from the second embodiment in that it includes an isolation layer 41, and is provided with first and second supply ports 34A and 34B as supply ports and first and second outlet ports 35A and 35B as outlets.

[0101] The separator layer 41 is disposed between the cathode 21 (i.e., the first catalyst 26) and the anode 22 (i.e., the second catalyst 27) so as to separate the region on the cathode 21 side from the region on the anode 22 side. The separator layer 41 preferably separates the carbon monoxide generated in the first catalyst 26 (cathode 21) from the oxidant generated in the second catalyst 27 (anode 22). The separator layer 41 may be any layer that is permeable to ions but impermeable to the electrolyte 23, carbon monoxide, and oxidants; specifically, an ion exchange membrane is preferred. The ion exchange membrane may be a solid membrane, such as a cation exchange membrane that is permeable to cations such as protons, or an anion exchange membrane that is permeable to anions such as hydroxide ions. However, a cation exchange membrane is preferred from the viewpoints of ionic conductivity and cost.

[0102] Examples of cation exchange membranes include those having at least one of sulfonyl, carboxyl, phosphate, and silicic acid groups as functional groups. Examples of cation exchange membranes having sulfonyl groups as functional groups include hydrocarbon resin-based polysulfonic acids such as polyethylene sulfonic acid and fullerene-crosslinked polysulfonic acid, and fluororesin-based sulfonic acids such as perfluoroethylene sulfonic acid. Examples of perfluoroethylene sulfonic acid include copolymers of tetrafluoroethylene and perfluoro[2-(fluorosulfonylethoxy)propyl vinyl ether], and commercially available products include "Nafion" (a trademark of DuPont). Examples of membranes having carboxyl groups as functional groups include polycarboxylic acids such as polyacrylic acid. Examples of membranes having phosphate or silicic acid groups as functional groups include heteropolyacids such as silicotungstic acid and phosphotungstic acid. Furthermore, cation exchange membranes made of SiO ２ -P ２ O ５ Phosphate glasses such as those listed above, and ceramics such as perovskite oxides can also be used.

[0103] Examples of anion exchange membranes include resins containing quaternary ammonium salts such as poly(styrylmethyltrimethylammonium chloride), polyethers, and polymers containing imidazolium groups. Examples of resins containing ammonium salts include "FAA-3-50" from FuMA-Tech GmbH and "TM1 Durion Grade" from Orion. Examples of polymers containing imidazolium groups include styrene-based polymers containing imidazolium groups, and specific examples include copolymers of styrene and 1-(p-vinylbenzyl)-3-methylimidazolium (PSMIM), copolymers of styrene and 1-(p-vinylbenzyl)-tetramethylimidazolium (PSTMIM), and copolymers of styrene and 1-(p-vinylbenzyl)-2,3-dimethylimidazolium (PSDMIM).

[0104] The first supply port 34A and the first discharge port 35A are provided on the wall surface 20B and are arranged on the wall surface 20B outside the cathode 21 so as to sandwich the cathode 21. The second supply port 34B and the second discharge port 35B are arranged on the wall surface 20A outside the anode 22 so as to sandwich the anode 22. The first discharge port 35A is connected to the second supply port 34B via the connecting path 36. With the above configuration, the electrolytic solution 23 is supplied from the first supply port 34A, flows along the surface of the cathode 21 in the cathode 21-side region, contacts the first catalyst 26 of the cathode 21, and is then supplied to the anode 22-side region via the connecting path 36. The electrolytic solution 23 flows along the surface of the anode 22 in the anode 22-side region, contacts the second catalyst 27 of the anode 22, and is then discharged from the second discharge port 35B. Therefore, also in this embodiment, the electrolytic solution 23 has a direction of convection F in which the electrolytic solution 23 contacts the first catalyst 26 and then the second catalyst 27. Also in this embodiment, the electrolytic solution 23 discharged from the second outlet 35B may be circulated and resupplied from the first supply port 34A, and the circulation may be repeated.

[0105] As described above, the separator 41 does not allow the electrolyte solution 23 and the like to pass through but allows ions to pass through, and therefore, in this embodiment as well, when a voltage is applied between the cathode 21 and the anode 22, an electrochemical reaction occurs between the cathode 21 and the anode 22. Therefore, in this embodiment, carbon dioxide is reduced to produce a reduction product (carbon monoxide) in the region on the cathode 21 side, and oxygen-containing organic substances such as carbonyl compounds are produced by the reduction product and reaction substrates contained in the electrolyte solution 23 in the region on the anode 22 side, and these are discharged from the second outlet 35B.

[0106] Here, the isolation layer 41 prevents carbon monoxide generated in the cathode 21 region from passing through to the anode 22 region, and prevents oxidants (such as redox mediators) generated on the anode 22 region from passing through to the cathode 21 region. Therefore, on the cathode 21 region, the reaction is prevented from being inhibited by the oxidant, and by-products are prevented from being generated due to the oxidant. Similarly, on the anode 22 region, the inhibition of the oxygen-containing organic substance production reaction by carbon monoxide and the generation of by-products are prevented, and oxygen-containing organic substances can be produced more efficiently. Therefore, in this embodiment, the electrochemical reaction device 40 can more efficiently synthesize oxygen-containing organic substances using carbon dioxide as a raw material. Furthermore, by circulating the electrolyte 23, the production rate of oxygen-containing organic substances can be improved.

[0107] Fifth Embodiment Next, an electrochemical reaction device according to a fifth embodiment of the present invention will be described. FIG. 6 shows an electrochemical reaction device (electrochemical cell) 50 according to the fifth embodiment. Differences between the fifth embodiment and the first embodiment will be described below. The electrochemical reaction device 50 according to the fifth embodiment of the present invention includes a cathode 51, an anode 52, and an electrolytic solution 53 containing a reaction substrate and an electrolyte. A plurality of cathodes 51 (two in this embodiment) are provided, each having a first catalyst 56 that reduces carbon dioxide to carbon monoxide. The anode 52 contains a second catalyst 57. In this embodiment, there is only one anode 52.

[0108] The cathodes 51, 51 are provided on the wall surfaces 50A, 50B facing each other in the Y direction, and are arranged parallel to each other. The cathodes 51 are parallel to the X direction. In this manner, the multiple cathodes 51 can be said to be arranged in parallel. On the other hand, the anodes 52 are arranged parallel to the Y direction and are arranged perpendicular to each cathode 51. The anodes 52 are attached to the wall surface 50A of the electrochemical reaction device 50, but this is not a limitation. A first catalyst 56 and a second catalyst 57 are supported, for example, in a layered form, on the surfaces of the cathodes 51 and the anodes 52, respectively. Therefore, the first catalyst 56 of the cathode 51 and the second catalyst 57 of the anode 52 are arranged perpendicular to each other, similar to the cathodes 51 and the anodes 52.

[0109] A first supply path 54A and a first discharge port 55A are provided on the wall surface 50B, and a second supply path 54B and a second discharge port 55B are provided on the wall surface 50A. The supply paths 54A, 55A and the discharge ports 55A, 55B are arranged outside the cathode 51 (first catalyst 56) and the anode 52 (second catalyst 57) and are arranged to sandwich them when viewed in the Y direction. In this embodiment, the electrolytic solution 53 is supplied from the first supply path 54A and the second supply path 54B arranged on the cathode 51 side and discharged from the second discharge path 55A and the second discharge path 55B arranged on the anode 52 side. Therefore, in this embodiment, convection F is formed so that the electrolytic solution 23 flows from the cathode 51 to the anode 52 along the cathode 51 and the anode 52 arranged in the X direction. As a result, in this embodiment as well, the direction of convection F is formed so that the electrolytic solution 53 contacts the cathode 51 (first catalyst 56) and then the anode 52 (second catalyst 57), and similarly to the above-described embodiments, the electrochemical reaction device 50 can efficiently produce oxygen-containing organic substances such as carbonyl compounds. Also in this embodiment, by circulating the electrolytic solution 53, the production rate of oxygen-containing organic substances such as carbonyl compounds can be improved.

[0110] Although this embodiment illustrates an embodiment in which two cathodes 51 are provided, one cathode 51 may be provided, or three or more cathodes 51 may be provided, for example, as shown in FIG. 7 . When three or more cathodes 51 are provided, the cathodes 51 on both sides of the parallel-arranged multiple cathodes 51 may be attached to, for example, the wall surface of the reaction chamber, as shown in FIG. 6 . The other cathodes 51 may be supported by a holder (not shown) or the like provided inside the reaction chamber. Furthermore, FIG. 7 illustrates an embodiment in which the cathodes 51 on both sides have a catalyst layer made of the first catalyst 26 formed on only one surface, and the other cathodes 51 have catalyst layers formed on both surfaces, but this embodiment is not limited to this embodiment. Furthermore, in this embodiment, the cathode 51 and the anode 52 do not need to be orthogonal to each other; the cathode 51 may be disposed at an angle relative to the anode 52. As a result, the first catalyst 56 of the cathode 51 is disposed at an angle relative to the second catalyst 57 of the anode 52. When the anode 52 is disposed at an angle, the angle of inclination may be 1° or more and 179° or less, preferably 60° or more and 120° or less, and more preferably 80° or more and 100° or less. In this embodiment, a plurality of anodes 52 may be provided. Furthermore, although two supply ports and two discharge ports are provided, the number of supply ports and discharge ports is not limited, and may be, for example, one.

[0111] Sixth Embodiment Next, a sixth embodiment of the present invention will be described. FIG. 8 shows an electrochemical reaction device 60 according to the sixth embodiment. Differences between the sixth embodiment and the first embodiment will be described below. The electrochemical reaction device 60 according to the sixth embodiment includes a cathode 61, an anode 62, and an electrolytic solution 63 containing a reaction substrate and an electrolyte. The cathode 61 has a first catalyst 66, as in the first embodiment. On the other hand, in this embodiment, the anode 62 does not need to contain a second catalyst. In order to incorporate a catalyst into the anode, a process for supporting the catalyst on the electrode is required, as described above. However, if the anode does not contain a catalyst, such a process is not necessary, thereby simplifying the configuration of the electrochemical reaction device (electrochemical cell).

[0112] The electrochemical reaction device 60 according to this embodiment includes a second reaction section in addition to an electrochemical cell (first reaction section), and a series of reactions for obtaining oxygen-containing organic compounds from carbon dioxide take place in the first and second reaction sections. The electrochemical reaction device 60 according to this embodiment includes a first reaction chamber (first reaction section) 60X including a cathode 61 and an anode 62, and a second reaction chamber (second reaction section) 60Y. The first reaction chamber 60X is an electrochemical cell having wall surfaces 60A and 60B facing each other in the Y direction. The wall surfaces 60A and 60B are respectively fitted with a cathode 61 and an anode 62, and the cathode 61 and the anode 62 are arranged facing each other in the Y direction. A voltage is applied between the cathode 61 and the anode 62 from a power source (not shown). Furthermore, a first supply port 64A and a first exhaust port 65A are provided on wall surfaces 60C and 60D of the first reaction chamber 20X facing each other in the X direction, respectively. As a result, the first supply port 64A and the first discharge port 65A are disposed outside the anode 62 and the cathode 61, and are disposed so as to sandwich the anode 62 and the cathode 61 when viewed along the Y direction. In this embodiment, the first reaction chamber 60X may be a single-chamber electrochemical cell (electrolysis cell). That is, the first reaction chamber 10X is not divided into an anode chamber and a cathode chamber by a separator layer such as an ion exchange membrane, but is composed of a single electrolysis chamber, in which both the cathode 11 and the anode 12 are provided and which is filled with an electrolytic solution 13. The second reaction chamber 60Y is filled with an electrolytic solution 63, and the electrolytic solution 63 contains a second catalyst 67. The second catalyst 67 may be dispersed or dissolved in the electrolytic solution 63. In addition, the second reaction chamber 60Y has a second supply port 64B and a second discharge port 65B provided on opposing wall surfaces 60E and 60F, respectively. The second supply port 64B is connected to the first discharge port 65A via a connection path 68. The connection path, the circulation path, the supply path, the branch path, the discharge path, and the like, which will be described later, are not particularly limited, but may be composed of piping or the like.

[0113] A filter (not shown) is preferably attached to the second outlet 65B. Attaching a filter to the second outlet 65B prevents the second catalyst 67 in the electrolytic solution 63 filled in the second reaction chamber 60Y from being discharged from the second outlet 65B along with the electrolytic solution 63. In this embodiment, a filter may also be similarly provided at the second supply port 64B. By providing a filter at the second supply port 64B, it is possible to prevent the second catalyst 67 in the second reaction chamber 60Y from flowing back and mixing into the first reaction chamber 60X. Any filter that does not allow the second catalyst 67 to pass through may be used. For example, when the second catalyst is dispersed in the electrolytic solution 63, a membrane filter, a mesh filter, or the like may be used. On the other hand, when the second catalyst 67 is dissolved in the electrolytic solution 63, a chemical adsorption filter, a physical adsorption filter, or the like may be used.

[0114] Furthermore, a stirring device such as a stirring blade or a stirring bar may be provided inside the second reaction chamber 60Y to stir the electrolytic solution 63 therein. By stirring the inside of the second reaction chamber 60Y, even if the second catalyst 67 does not dissolve in the electrolytic solution 63, the second catalyst 67 can be more easily diffused into the electrolytic solution 63, and the reaction efficiency in the second reaction chamber 60Y can be more easily improved. However, a stirring device does not have to be provided in the second reaction chamber 60Y. Even without providing a stirring device, the second catalyst 67 can be diffused into the electrolytic solution 63 by convection F of the electrolytic solution 63. Furthermore, if the electrolytic solution 63 is dissolved in the second catalyst 67, the second catalyst 67 can be diffused into the electrolytic solution 63 without stirring.

[0115] With the above configuration, this embodiment is provided with a first reaction section (first reaction chamber 60X, electrochemical cell) having a cathode 61 with a first catalyst and an anode 62, and a second reaction section (second reaction chamber 60Y) having a second catalyst 67. The electrolytic solution 63 flows from the first supply port 64A of the first reaction chamber 60X toward the first discharge port 65A, and the electrolytic solution 63 discharged from the first discharge port 65A is supplied to the second reaction chamber 60Y via the second supply port 64B. In the second reaction chamber 60Y, the electrolytic solution 63 is discharged from the second discharge port 65B. The electrolytic solution 63 discharged from the second discharge port 65B may be circulated via a circulation path (not shown) and resupplied from the first supply port 64A, and this circulation may be repeated. In addition, when the electrolytic solution 63 flows from the supply port 64A to the discharge port 65A in the first reaction chamber 60X, a convection current F is formed inside the electrochemical cell so as to be directed in the X direction. In other words, the convection current F is formed so that the electrolytic solution 63 flows in a direction intersecting the direction in which the electrodes face each other.

[0116] In this embodiment, by flowing the electrolytic solution 63 as described above, the electrolytic solution 63 has a convection current F flowing in the order of the first reaction section (first reaction chamber 60X, electrochemical cell) and the second reaction section (second reaction chamber 60Y). Then, at the cathode 61, the first catalyst 66 promotes the reduction of carbon dioxide, producing a reduced product of carbon dioxide (carbon monoxide). The electrochemical reaction occurring at the cathode is typically as shown in the above formula (A). Meanwhile, at the anode 62, an oxidant (e.g., a redox mediator) is produced, which is an active intermediate species. That is, at the anode 62, the redox species formed by the electrolyte are converted from reduced species to an oxidant (e.g., a redox mediator) which is an active intermediate species. When the electrolyte is a brominated salt, the reaction occurring at the anode 62 is as shown in the following formula (B), in which bromine is produced as an oxidant: 2Br － → Br ２ +2e －(B) The carbon monoxide and active intermediate species (oxidant) generated in the first reaction chamber 60X are supplied to the second reaction section (second reaction chamber 60Y) by convection F along with the electrolytic solution 63. In the second reaction section (second reaction chamber 60Y), oxygen-containing organic substances such as carbonyl compounds are generated from the carbon monoxide, active intermediate species, and reaction substrates by the action of the second catalyst 67. The electrolytic solution 63 supplied to the second reaction chamber 60Y typically contains carbon dioxide in addition to carbon monoxide. The carbon monoxide may be dissolved in the electrolytic solution 63, or may be present in the electrolytic solution 63 as bubbles without dissolving. Furthermore, although not particularly limited, an example of a reaction in which the reaction substrate is methanol and the electrolyte is a bromide salt is shown in the following formula (C). When the reaction substrate is methanol and the electrolyte is a bromide salt, the oxidant bromine and methanol react in the second reaction chamber 60Y to generate dimethyl carbonate (DMC). Bromine is also reduced to bromide ions, producing, for example, hydrogen bromide. ２ +CH ３ OH → DMC+2HBr (C)

[0117] As described above, in this embodiment, the electrochemical reaction device 60, despite its simple configuration, can synthesize oxygen-containing organic compounds using carbon dioxide as a raw material. Furthermore, by circulating the electrolytic solution 63 in the electrochemical reaction device 60, the production rate of oxygen-containing organic compounds can be improved. Furthermore, in this embodiment, the carbon dioxide reduction reaction and the oxygen-containing organic compound synthesis reaction are carried out in different reaction sections (first and second reaction sections), respectively, which facilitates the progress of each reaction and enables efficient production of oxygen-containing organic compounds such as carbonyl compounds. Furthermore, oxidants such as halogens generated in the first reaction chamber 60X (first reaction section) are sent to the second reaction chamber 60Y (second reaction section) by convection F. This prevents an increase in power consumption due to oxidants such as halogens in the first reaction chamber 60X (first reaction section), and also prevents side reactions caused by oxidants such as halogens at the cathode 61. Therefore, the production yield of the target product can be increased while reducing power consumption. Generally, the electrolytic solution 63 does not react completely with the carbon dioxide contained therein if it passes through the reaction chamber only once. Therefore, in this embodiment as well, by circulating the electrolytic solution 63, it is possible to improve the production rate of oxygen-containing organic substances such as carbonyl compounds.

[0118] The first catalyst used in the sixth embodiment is as described in the first embodiment. As described in the first embodiment, the second catalyst is not particularly limited as long as it promotes the electrochemical reaction of synthesizing an oxygen-containing organic substance, such as a carbonyl compound, from carbon monoxide, and may include a metal element. Details of the metal element are as described in the first embodiment. Specifically, the second catalyst may be an active particle-containing catalyst or a metal salt, but is preferably an active particle-containing catalyst. Details of the active particle-containing catalyst and the metal salt are as described above. In the sixth embodiment, the metal element used in the second catalyst may be contained in the electrolytic solution in the form of metal ions. The metal ions may be formed, for example, by adding the metal salt to the electrolytic solution.

[0119] In the second reaction chamber, the second catalyst may be dissolved or insoluble in the electrolytic solution, and an insoluble second catalyst may be dispersed in the electrolytic solution. The content of the second catalyst in the electrolytic solution is not particularly limited and may be adjusted to a level at which the synthesis of an oxygen-containing organic substance such as a carbonyl compound proceeds appropriately. A specific content of the second catalyst is, for example, 0.01 g to 100 g, preferably 0.05 g to 50 g, and more preferably 0.1 g to 20 g per liter of electrolytic solution. Note that, when the metal salt is a hydrate, the content of the second catalyst refers to the amount excluding the mass of water molecules in the hydrate.

[0120] Seventh Embodiment Fig. 9 shows an electrochemical reaction device 70 according to a seventh embodiment. Hereinafter, in the seventh embodiment, differences from the sixth embodiment will be described, and portions that will not be described are the same as those in the sixth embodiment. The seventh embodiment differs from the sixth embodiment in that an isolation layer 71 is provided in the first reaction chamber 60X of the electrochemical reaction device 70. Note that in the seventh embodiment, the same components as those in the sixth embodiment are denoted by the same reference numerals.

[0121] The separator 71 is disposed between the cathode 61 (i.e., the first catalyst 66) and the anode 62, and is provided to separate the inside of the first reactor 60X (electrochemical cell) into a region on the cathode 61 side (cathode chamber 70A) and a region on the anode 62 side (anode chamber 70B). The configuration of the separator 71 is similar to that of the separator 41 in the fourth embodiment, and it is preferable that the separator 71 separates the carbon monoxide generated in the first catalyst 66 (cathode 61) from the oxidant generated in the anode 62, and is preferably an ion exchange membrane. In this embodiment, the first reactor 60X is provided with two first supply paths 64A1, 64A2 and two first exhaust ports 65A1, 65A2, and the second reaction chamber 60Y is also provided with two second supply ports 64B1, 64B2. The second supply ports 64B1 and 64B2 are connected to the first discharge ports 65A1 and 65A2 via connection paths 68A and 68B, respectively.

[0122] With the above configuration, in the first reaction chamber 60X, in the region on the cathode 61 side isolated by the isolation layer 71, the electrolytic solution 63 flows from the first supply port 64A1 to the second outlet 65A1. As a result, the electrolytic solution 63 flows along the surface of the cathode 61 while contacting the cathode 61 (first catalyst 66). On the other hand, in the region on the anode 62 side isolated by the isolation layer 71, the electrolytic solution 63 flows from the first supply port 64A2 to the second outlet 65A2. As a result, the electrolytic solution 63 flows along the surface of the anode 62 while contacting the anode 62. The electrolytic solution 63 then flows from the region on the cathode 61 side and the region on the anode 62 side to the second reaction chamber 60Y in this order. Therefore, in this embodiment as well, a reduction product of carbon dioxide (carbon monoxide) is generated in the cathode 61, and an oxidant (e.g., a redox mediator such as a halogen) that is an active intermediate species is generated in the anode 62. The carbon monoxide and active intermediate species produced in the first reaction chamber 60X are supplied to the second reaction section (second reaction chamber 60Y) together with the electrolytic solution 63 by convection F. Then, in the second reaction section (second reaction chamber 60Y), oxygen-containing organic substances such as carbonyl compounds are produced from the carbon monoxide, active intermediate species, and reaction substrates by the action of the second catalyst 67.

[0123] In this embodiment, the carbon dioxide reduction reaction and the oxygen-containing organic compound synthesis reaction are carried out in separate reaction chambers (first and second reaction zones), thereby enabling efficient production of oxygen-containing organic compounds such as carbonyl compounds. Furthermore, oxidants such as halogens generated on the anode 62 side are sent to the second reaction zone 60Y (second reaction zone) by convection F, preventing increased power consumption due to oxidants such as halogens. This allows for increased production of the target substance while reducing power consumption. Furthermore, the isolation layer 71 prevents carbon monoxide generated in the cathode 61 side region from permeating to the anode 62 side and prevents oxidants (such as redox mediators) generated on the anode 62 side from permeating to the cathode 21 side. Therefore, similar to the fourth embodiment, the electrochemical reaction device 70 can more efficiently synthesize oxygen-containing organic compounds using carbon dioxide as a raw material. Therefore, similar to the first embodiment, this embodiment also allows for increased production of the target substance while reducing power consumption. Furthermore, similar to the first embodiment, this embodiment also allows for further improvement in the production rate of oxygen-containing organic compounds by circulating the electrolytic solution 13. Also in this embodiment, the production rate of oxygen-containing organic substances can be improved by circulating the electrolytic solution 63 .

[0124] Although the seventh embodiment described above includes the isolation layer 71, other materials may be used instead of the isolation layer 71. For example, a migration prevention layer may be used instead of the isolation layer 71 to prevent carbon monoxide from migrating from the cathode 61 side to the anode 62 side or prevent oxidants from migrating from the anode 62 side to the cathode 61 side. The migration prevention layer may be, for example, the rectifying layer described in the third embodiment. In this embodiment, the electrolytic solution 63 containing carbon dioxide is supplied from both the first supply ports 64A1 and 64A2. However, the electrolytic solution 63 supplied to the anode 63 side region from the supply port 64A2 may be substantially free of carbon dioxide. Supplying the electrolytic solution 63 substantially free of carbon dioxide to the anode side region further facilitates the generation of oxidants at the anode 62. The term "electrolytic solution 63 substantially free of carbon dioxide" means that the electrolytic solution 63 is allowed to contain carbon dioxide at a concentration similar to that present in the atmosphere.

[0125] Eighth Embodiment Fig. 10 shows an electrochemical reaction device 80 according to an eighth embodiment. The eighth embodiment differs from the sixth embodiment in the configuration of the first reaction chamber and the second reaction chamber. Hereinafter, the eighth embodiment will be described in terms of differences from the sixth embodiment, and portions for which description will be omitted are the same as those in the sixth embodiment. In the eighth embodiment, the same components as those in the sixth embodiment are denoted by the same reference numerals.

[0126] In the eighth embodiment, second reaction chamber 60Y is arranged so that second supply port 64B is on the lower side and second discharge port 65B is on the upper side, whereby convection F is formed in second reaction chamber 60Y such that electrolytic solution 63 flows from bottom to top along the vertical direction. Similarly, first reaction chamber 60X (electrochemical cell) is arranged so that supply port 64A is on the lower side and discharge port 65A is on the upper side, whereby convection F is formed in first reaction chamber 60X such that electrolytic solution 63 flows from bottom to top along the vertical direction.

[0127] The second reaction chamber 60Y also includes a catalyst layer 67Y having a second catalyst 67. The catalyst layer 67Y may be configured by packing the second catalyst 67 in a layer inside the second reaction chamber 60Y. The catalyst layer 67Y may be packed on a support such as a tray or mesh inside the second reaction chamber 60Y, but a support need not be provided.

[0128] The second catalyst 67 is preferably an active particle-containing catalyst in which active particles are supported on a support, as described above. However, when the catalyst layer 67Y is configured as in the eighth embodiment, the support may be, as described above, porous carbon, silica, aluminum oxide, or zirconium oxide. Of these, silica, aluminum oxide, and zirconium oxide are preferred, with aluminum oxide being particularly preferred. When the second catalyst 67 constitutes the catalyst layer 67Y as in this embodiment, the metal content of the active particles is 0.1 to 15 parts by mass, preferably 0.2 to 10 parts by mass, and more preferably 0.3 to 3 parts by mass, per 100 parts by mass of the support, from the viewpoint of ensuring the reaction in the second reaction chamber 60Y proceeds appropriately. Therefore, the active particle-containing catalyst used in the catalyst layer 67Y as in the eighth embodiment may be manufactured as described above, but the amounts of the support and metal in the second catalyst raw material may be appropriately adjusted to achieve the above-described ratio.

[0129] The second reaction chamber 60Y may include a gas diffusion mechanism 69 below the catalyst layer 67Y. The gas diffusion mechanism 69 may be provided above the second supply port 64B. The gas diffusion mechanism 69 is not particularly limited as long as it can diffuse carbon monoxide contained in the electrolytic solution 63 supplied from the second supply port 64B, but may be, for example, a stirring device formed of a stirring blade, a stirring bar, or the like.

[0130] As described above, in this embodiment, the carbon monoxide-containing electrolyte 63 flows from bottom to top in the second reaction chamber 60Y. This allows the carbon monoxide bubbles in the electrolyte 63 to move smoothly due to buoyancy, thereby efficiently synthesizing oxygen-containing organic compounds such as carbonyl compounds in the catalyst layer 67Y. Furthermore, the provision of the gas diffusion mechanism 69 allows carbon monoxide to diffuse more appropriately in the electrolyte 63, thereby further increasing the efficiency of oxygen-containing organic compounds. Similarly, the electrolyte 63 flows from bottom to top in the first reaction chamber 60X (electrochemical cell), thereby efficiently reducing carbon dioxide to carbon monoxide in the catalyst 66. Note that this embodiment illustrates an electrochemical reaction device 80 that includes a circulation path 78 connecting the second outlet 65B of the second reaction chamber 60Y and the first supply port 64A of the first reaction chamber 60X, allowing the electrolyte 63 to circulate. However, in this embodiment, as in the sixth and seventh embodiments, the electrolyte 63 does not necessarily have to be circulated.

[0131] Furthermore, in the eighth embodiment, the gas diffusion mechanism 69 may be omitted. Furthermore, although the convection F in the second reaction chamber 60Y is formed such that the electrolytic solution 63 flows from bottom to top along the vertical direction, the present invention is not limited to such a configuration and the electrolytic solution 63 may be formed such that the electrolytic solution 63 flows from top to bottom. Similarly, the convection F in the first reaction chamber 60X does not necessarily have to be formed such that the electrolytic solution 63 flows from bottom to top along the vertical direction and may be formed such that the electrolytic solution 63 flows from top to bottom.

[0132] <Ninth Embodiment> Fig. 11 shows an electrochemical reaction device 90 according to a ninth embodiment. The ninth embodiment differs from the eighth embodiment in the configuration of the first reaction chamber and the flow direction of the convection current F. Hereinafter, the differences between the ninth embodiment and the eighth embodiment will be described in detail, and parts that will not be described are the same as those in the first embodiment. In the ninth embodiment, the same components as those in the eighth embodiment will be denoted by the same reference numerals.

[0133] In the ninth embodiment, the configuration of the first reaction chamber 60X is the same as that of the seventh embodiment, and therefore the first reaction chamber 60X is provided so as to separate the region on the cathode 61 side (cathode chamber 70A) from the region on the anode 62 side (anode chamber 70B) by the isolation layer 71. On the other hand, the second reaction chamber 60Y has the same configuration as the second reaction chamber 60Y in the eighth embodiment.

[0134] In this embodiment, the first exhaust port 65A1 of the cathode chamber 70A is connected to the first supply port 64A2 of the anode chamber 70B via a connection path 96A. Furthermore, the first exhaust port 65A2 of the anode chamber is connected to the second supply port 64B of the second reaction chamber 60Y via a connection path 96B. Therefore, the carbon dioxide-containing electrolytic solution 63 supplied from the supply port 64A1 of the cathode chamber 70A has a convection F direction such that the electrolytic solution 63 flows in the order of the cathode chamber 70A, the anode chamber 70B, and the second reaction chamber 60Y. Therefore, in this embodiment, as in the seventh embodiment, the production yield of the target substance can be increased while suppressing power consumption, and the provision of the partition layer 71 allows for more efficient production of oxygen-containing organic matter. Note that in this embodiment, the electrolytic solution 63 discharged from the second exhaust port 65B may be circulated via a circulation path (not shown) and resupplied from the first supply port 64A, and this circulation may be repeated.

[0135] <Tenth Embodiment> Fig. 12 shows an electrochemical reaction device 100 according to a tenth embodiment. The tenth embodiment differs from the ninth embodiment in that the form of convection of the electrolytic solution 63 is different. Hereinafter, the differences between the tenth embodiment and the ninth embodiment will be described in detail, and parts that will not be described are the same as those in the ninth embodiment. In the tenth embodiment, the same components as those in the ninth embodiment will be denoted by the same reference numerals.

[0136] In this embodiment, the electrochemical reaction device 100 includes a circulation path 106A that connects the first outlet 65A1 and the first supply port 64A1 of the cathode chamber 70A. Therefore, the electrolytic solution 63 in the cathode chamber 70A is circulated by being discharged from the first outlet 65A1 of the cathode chamber 70A, passing through the circulation path 106A, and being resupplied from the first supply port 64A1. That is, the electrolytic solution 63 in the cathode chamber 70A flows so as to form a convection current F1 that circulates from being discharged to the outside of the first reaction chamber 60X and then returning to the cathode chamber 70A. The electrochemical reaction device 100 also includes a circulation path 106B that connects the first outlet 65A2 of the anode chamber 70B with the second supply port 64B of the second reaction chamber 60Y, and a circulation path 106C that connects the second outlet 65B of the second reaction chamber 60Y with the first supply port 64A2 of the anode chamber 70B. Therefore, the electrolytic solution 63 flows between the anode chamber 70B and the second reaction chamber 60Y so as to form a convection current F2 that circulates via the circulation paths 106B and 106C.

[0137] The electrochemical reaction device 100 further includes a branch path 106C branching off from the circulation path 106A, and the first outlet 65A1 of the cathode chamber 70A is also connected to the circulation path 106B via the circulation path 106A and the branch path 106C. This also forms a connection path that connects the first circulation path (circulation path 106A) through which the convection current F1 flows and the second circulation path through which the convection current F2 flows.

[0138] A valve 107 is provided at the connection between the circulation path 106A and the branch path 106C. When the valve 107 is opened, at least a portion of the gas in the electrolytic solution 63 (e.g., gas that does not dissolve in the electrolytic solution 63) flows out to the branch path 106C. Therefore, when the valve 107 is closed, all of the electrolytic solution 63 discharged from the first outlet 65A1 of the cathode chamber 70A circulates through the first circulation path and is returned to the cathode chamber 70A. When the valve 107 is opened, a portion of the gas contained in the electrolytic solution 63 passing through the circulation path 106A is supplied to the second circulation path (i.e., the path circulating through the reaction section (first reaction chamber) 60Y and the anode chamber 70B) via the branch path 106C (i.e., the connecting path). That is, the electrolytic solution 63 discharged from the outlet 65A1 of the cathode chamber 70A can be switched between flowing by convection F1 (also referred to as "circulation") and flowing by convection F1 while at least a portion of the gas is flowing by convection F3 (also referred to as "release"). Circulation and release may be repeated. The gas flowing by convection F3 is a mixed gas of carbon monoxide and carbon dioxide.

[0139] The time during which the electrolytic solution 63 is circulated (also referred to as the "circulation time") is not particularly limited, but may be, for example, approximately 1 to 20 minutes, preferably 2 to 15 minutes, and more preferably 3 to 10 minutes. By setting the circulation time at or above the lower limit, a large amount of carbon dioxide can be reduced to carbon monoxide. By setting the circulation time at or below the upper limit, carbon dioxide can be reduced to carbon monoxide at a rate commensurate with the circulation time. Therefore, by setting the circulation time within the above range, productivity of the target product can be improved. Furthermore, the time during which the gas contained in the electrolytic solution 63 is circulated by convection F3 due to opening (also referred to as the "open time") is not particularly limited, but from the perspective of improving productivity, it is preferable to set the open time shorter than the above circulation time. A specific open time may be, for example, approximately 0.5 to 15 minutes, preferably 1 to 10 minutes, and more preferably 2 to 8 minutes. By setting the open time within the above range, productivity of the target product can be improved.

[0140] A supply channel 106D is further connected to the first supply port 64A1 of the first reaction chamber (electrochemical cell) 60X, and the electrolytic solution 63 containing carbon dioxide is preferably supplied to the cathode chamber 70A via the supply channel 106D and the first supply port 64A1. Furthermore, a discharge channel (not shown) is connected to the second discharge port 65B of the second reaction chamber (second reaction part) 60Y and the first discharge port 65A2 of the anode chamber 70B, and the oxygen-containing organic matter produced in the electrochemical reaction device 100 is preferably discharged together with the electrolytic solution 63 to the outside of the electrochemical reaction device 100 from the second discharge port 65B, the first discharge port 65A2, or the like.

[0141] The electrochemical reaction device 100 according to this embodiment may be operated by switching the convection described above. First, the electrochemical reaction device 100 maintains the valve 107 in a closed state, and the electrolytic solution 63 containing carbon dioxide is circulated by convection F1 so as to repeatedly enter and exit the cathode chamber 70A. Next, after a certain period of circulation has elapsed, the valve 107 is opened, and the electrolytic solution 63 is circulated through the first circulation path and returned to the cathode chamber 70A, while a portion of the gas contained therein (a mixed gas of carbon monoxide and carbon dioxide) is supplied to the second circulation path (i.e., the path circulating through the second reaction chamber (second reaction section) 60Y and the anode chamber 70B) via the branch path 106C. Furthermore, in the second circulation path, convection F2 is formed so that the electrolytic solution 63 circulates between the second reaction chamber 60Y and the anode chamber 70B. Therefore, the second reaction chamber 60Y synthesizes an oxygen-containing organic compound using carbon monoxide supplied via the branch path 106C and an oxidant generated at the anode. The electrolytic solution 63 containing the oxygen-containing organic compound synthesized in the reaction chamber 60Y or the like may be appropriately discharged to the outside via the outlet 65B, the outlet 65A2, or the like. However, the electrolytic solution 63 discharged via the outlet 65B, the outlet 65A2, or the like may be resupplied via the supply port 64A1. That is, the electrolytic solution 63 may also be circulated between the cathode chamber 70A and the anode chamber 70B and the second reaction unit 60Y. Furthermore, if the electrolytic solution 63 is discharged via the outlet 65B, the outlet 65A2, or the like and not resupplied via the supply port 64A1, the amount of electrolytic solution contained in the electrochemical reaction device 100 decreases. Therefore, the electrolytic solution 63 containing carbon dioxide may be additionally supplied via the supply port 64A1.

[0142] By performing the above operation, the electrolytic solution 63 circulated by convection F1 so as to repeatedly enter and exit the cathode chamber 70A repeatedly undergoes a reduction reaction, and carbon dioxide contained in the electrolytic solution 63 can be reduced to carbon monoxide at a high conversion rate. Furthermore, the gas contained in the electrolytic solution 63 is supplied to the second reaction chamber 60Y and the anode chamber 70B with an increased carbon monoxide content. Therefore, in this embodiment, oxygen-containing organic substances are produced while the electrolytic solution 63 is circulated between the anode chamber 70B and the second reaction chamber 60Y in the second circulation path with the gas containing the electrolytic solution 63 having an increased carbon monoxide content, thereby improving production efficiency.

[0143] 11th Embodiment FIG. 13 shows an electrochemical reaction device 110 according to an 11th embodiment. Hereinafter, differences between the 11th embodiment and the 10th embodiment will be described, and portions that will not be described are the same as those in the 10th embodiment. While the valve 107 was provided in the 10th embodiment as described above, the valve 107 is omitted in this embodiment. However, the connection between the circulation path 106A and the branch path 106C has a valve structure that allows a portion of the gas contained in the electrolytic solution 63 passing through the circulation path 106A (e.g., a gas that is not dissolved in the electrolytic solution 63) to flow to the branch path 106C. Therefore, a portion of the gas contained in the electrolytic solution 63 passing through the circulation path 106A (a gas that is not dissolved in the electrolytic solution 63) is always flowed to the branch path 106C side at the connection between the circulation path 106A and the branch path 106C. Therefore, the electrolytic solution 63 discharged from the outlet 65A1 of the cathode chamber 70A is circulated through the first circulation path (circulation path 106A) and returned to the cathode chamber 70A, while a portion of the contained gas (a mixed gas of carbon monoxide and carbon dioxide) is supplied via the branch path 106C to the second circulation path (i.e., the second reaction chamber (second reaction unit 60Y) and the anode chamber 70B). Therefore, in this embodiment, as in the tenth embodiment, the electrolytic solution 63 circulated so as to repeatedly enter and exit the cathode chamber 70A by the convection F1 repeatedly undergoes a reduction reaction, and the carbon dioxide contained in the electrolytic solution 63 can be reduced to carbon monoxide. Furthermore, the gas contained in the electrolytic solution 63 is mixed with the electrolytic solution circulating through the second reaction chamber 60Y and the anode chamber 70B while containing carbon monoxide. Therefore, oxygen-containing organic matter is produced while the electrolyte 63 circulates between the anode chamber 70B and the second reaction chamber 60Y in the second circulation path, so that oxygen-containing organic matter can be produced efficiently in this embodiment as well.

[0144] Other Embodiments In the sixth to eleventh embodiments described above, the anode 62 does not contain a second catalyst. However, the second catalyst may be contained in the anode as well as in the second reaction section (second reaction chamber). By containing the second catalyst in the anode, oxygen-containing organic compounds are produced on the anode in addition to the second reaction section, thereby further improving the efficiency of oxygen-containing organic compound production. Furthermore, when oxygen-containing organic compounds are produced on the anode, at least a portion of the oxidants, such as halogens, produced at the anode are converted back to reduced species, such as halogen ions, thereby preventing increased power consumption and side reactions due to oxidants such as halogens. When the second catalyst is contained in the anode, it is preferable that the second catalyst be supported on the electrode substrate constituting the anode. Furthermore, the second catalyst may be supported on the electrode substrate together with a catalyst additive or the like. The method for supporting the second catalyst, or the second catalyst and catalyst additive (catalyst composition) on the electrode substrate, is not particularly limited. Since the method for supporting the first catalyst on the electrode substrate is the same as that described above, a detailed description thereof will be omitted.

[0145] In the sixth and seventh embodiments described above, the second catalyst is dispersed in the electrolytic solution in the second reaction section (second reaction chamber). However, the second catalyst may form a catalyst layer, as in the eighth to eleventh embodiments. Furthermore, in the eighth to eleventh embodiments, the second catalyst may be dispersed in the electrolytic solution in the second reaction section (second reaction chamber) as shown in the sixth and seventh embodiments, without forming a catalyst layer. Furthermore, in the first reaction chamber of the sixth to eleventh embodiments, a pair of a cathode and an anode are arranged to face each other. However, the arrangement of the cathode and anode is not limited to such an arrangement and may be any arrangement. For example, any of the arrangements described in the first to fifth embodiments may be adopted. Furthermore, in the sixth to eleventh embodiments, the number of cathodes and anodes is not particularly limited and does not need to be one, but may be two or more.

[0146] In the above embodiments, redox species were used as the electrolyte in the electrolytic solution. However, the electrolyte may contain an electrolyte other than the redox species in addition to the redox species. Examples of electrolytes other than the redox species include perchlorates such as sodium perchlorate (NaClO), zinc perchlorate, barium perchlorate, lithium perchlorate, and ammonium perchlorate, as well as sodium sulfate, potassium sulfate, and ammonium sulfate. These electrolytes other than the redox species may be used alone or in combination. Furthermore, for example, in the first to fifth embodiments, the redox species may be omitted as the electrolyte, and an electrolyte other than the redox species may be used instead of the redox species. In the first to fifth embodiments, even when an electrolyte other than the redox species is used instead of the redox species, oxygen-containing organic compounds such as carbonyl compounds can be synthesized at a constant conversion rate. When an electrolyte other than the redox species is used instead of the redox species, the reaction of synthesizing oxygen-containing organic compounds such as carbonyl compounds from carbon monoxide and a reaction substrate does not occur in the presence of oxidizing species. Therefore, the second catalyst synthesizes an oxygen-containing organic compound such as a carbonyl compound from carbon monoxide and a reaction substrate without using an oxidizing species.

[0147] Furthermore, the configurations of the embodiments described above have been specifically described in order to explain the present invention, and the present invention is not limited to the configurations of the embodiments described above.

[0148] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0149] (Example 1) [Preparation of catalyst] 38.0 mg of poly(4-vinylpyridine) (P4VP, weight average molecular weight 60,000) was dispersed in 50 ml of ethanol to obtain a P4VP dispersion. ３ ) ２1.8 ml of the P4VP / ethanol solution (6.5 mg, Co = 2 mg) and 54 mg of Ketjen Black (ECP600JD, manufactured by Lion Specialty Chemicals Co., Ltd.) were mixed with the P4VP dispersion and dried to obtain a powder (first catalyst raw material mixture). The cobalt content in the first catalyst raw material mixture was 2 mass %. The obtained powder was calcined in an argon atmosphere at 200°C for 3 hours to obtain a first catalyst (CoP4VP). 60 mg of Pd(NO ３ ) ２ ・2H ２ O (manufactured by Aldrich) and 60 mg of Ketchan Black (product name "EC-300J" (Fuel Cell Store)), BET specific surface area 800 m ２ / g, average primary particle diameter 40 nm) was dispersed in 50 ml of ion-exchanged water, dried, and then heated at 300° C. for 1 hour to obtain a second catalyst (Pd—C).

[0150] [Electrode Fabrication] A 4 cm x 4 cm FTO (current collecting layer: thickness ∼2 μm) / glass laminate was patterned by laser processing to obtain a substrate with three rows of strip-shaped current collecting layers (1 cm x 4 cm). Two such substrates were prepared. 24 mg of the first catalyst and 120 μL of a 10 mass% dispersion of catalyst additive (Nafion) were mixed and dispersed in 4800 μL of acetone, and spray-applied to every other strip of the current collecting layer of each substrate and dried to form a catalyst layer containing the first catalyst, thereby obtaining a cathode. Also, 24 mg of the second catalyst and 120 μL of a 10 mass% dispersion of catalyst additive (PTFE) were mixed and dispersed in 4800 μL of acetone, and spray-applied to the current collecting layers other than the current collecting layer on which the cathode was formed and dried to form a catalyst layer containing the second catalyst, thereby obtaining an anode.

[0151] [Preparation of Electrochemical Reaction Device (Cell)] A 4 mm thick frame (made of ABS) with tube holes (supply port and discharge port) was prepared, and this was sandwiched between substrates on which a cathode and anode were formed, with the cathode and anode facing each other, via a 0.5 mm thick Teflon (registered trademark) sheet (packing) cut to the same size, and sealed with epoxy resin to prepare the evaluation cell (electrochemical reaction device) shown in Figure 1. [Evaluation of Electrochemical Reaction Device (Cell)] A 50 ml solvent bottle was charged with a 0.1 M LiBr methanol solution, and carbon dioxide was bubbled through it for 15 minutes to prepare an electrolyte solution with carbon dioxide dissolved therein. A diaphragm pump was used to pump and circulate the electrolyte at 5 ml / min, and a current of 12 mA / cm was applied between the cathode and anode. ２ A current of 0.015 was passed for 15 minutes to cause an electrochemical reaction. The resulting electrolyte was analyzed by gas chromatography, and the selectivity of the target substance was calculated. The target substances for each example are as shown in Table 1.

[0152] Example 2 [Catalyst Preparation] The first catalyst and the second catalyst were prepared in the same manner as in Example 1. [Electrode Preparation] Two substrates consisting of a 4 cm x 4 cm FTO / glass laminate (FTO coated surface 3 cm x 4 cm, FTO thickness: 2 μm) were prepared. 24 mg of the first catalyst and 120 μL of a 10% by mass dispersion of a catalyst additive (Nafion) were mixed and dispersed in 4,800 μL of acetone. This was spray-coated on the FTO surface (current collector) of one substrate to form a catalyst layer containing the first catalyst, and a cathode was fabricated on the substrate. Similarly, 24 mg of Ketjen Black and 120 μL of a 10% by mass dispersion of a catalyst additive (Nafion) were mixed and dispersed in 4,800 μL of acetone. This was spray-coated on the FTO surface (current collector) of the other substrate to form a catalyst layer containing the second catalyst, and an anode was fabricated on the substrate.

[0153] [Preparation of Electrochemical Reaction Device] A 4 mm thick frame (made of ABS) with tube holes (first supply port and first exhaust port) was prepared. This was sandwiched between a substrate having an anode and a substrate having a cathode, with the anode and cathode facing each other, via a Teflon (registered trademark) sheet (packing) of the same size, to prepare a first reaction section (first reaction chamber). Next, a 2 cm x 2 cm glass plate and a 4 mm thick frame with tube holes (second supply port and second exhaust port) were prepared. This was sandwiched and held between two glass plates via a Teflon (registered trademark) sheet (packing) cut to the same size to prepare a second reaction section (second reaction chamber). A membrane filter (pore diameter: 3 μm) was inserted into the tube hole (second exhaust port) at the rear of the second reaction section. 10 mg of the second catalyst was dispersed in 1 ml of methanol, and the dispersion was introduced into the second reaction section using a syringe through a separately prepared syringe hole. Furthermore, the tube hole (first outlet) at the rear of the first reaction section was connected to the tube hole (second supply port) at the front of the second reaction section, thereby obtaining the electrochemical reaction device shown in FIG. 8.

[0154] [Evaluation of Electrochemical Reaction Device (Cell)] A 50 ml solution of 0.1 M LiBr in methanol was placed in a solvent bottle, and carbon dioxide was bubbled through it for 15 minutes to prepare an electrolyte solution containing dissolved carbon dioxide. A diaphragm pump was used to pump and circulate the electrolyte at a rate of 5 ml / min, and a current of 12 mA / cm was applied between the cathode and anode. ２ A current of 0.015 was passed for 15 minutes to cause an electrochemical reaction. Furthermore, the second catalyst in the second reaction zone was dispersed using a stirrer. The resulting electrolyte was analyzed by gas chromatography, and the selectivity of the target product was calculated.

[0155] (Example 3) As shown in Figure 9, an ion exchange membrane (trade name: Nafion 117) constituting a separator layer was inserted into the first reaction section to separate the anode side region from the cathode side region, and the same procedure as in Example 2 was carried out.

[0156] Example 4 [Catalyst Preparation] A first catalyst and a second catalyst were prepared in the same manner as in Example 1. [Electrode Preparation] Two sheets of carbon paper (product name "Toray 060", manufactured by Toray Industries, Inc.) were cut to 1 cm x 4 cm and prepared. 8 mg of the first catalyst and 40 μL of a 10% by mass dispersion of a catalyst additive (Nafion) were mixed, dispersed in 1600 μL of acetone, and spray-applied to one of the carbon papers to obtain a cathode having a catalyst layer containing the first catalyst. Furthermore, 8 mg of the second catalyst and 40 μL of a 10% by mass dispersion of a catalyst additive (Nafion) were mixed, dispersed in 1600 μL of acetone, and spray-applied to the other carbon paper to obtain an anode having a catalyst layer containing the second catalyst.

[0157] [Fabrication of Electrochemical Reaction Device (Cell)] Two vinyl chloride casings were prepared, and the casings were processed to install SUS current collectors, anodes or cathodes, and tube holes in each casing as shown in Figure 2. A 4 mm thick frame (vinyl chloride) was prepared, and this was sandwiched between the two casings via similarly shaped Teflon (registered trademark) sheets (packing), to fabricate the evaluation cell (electrochemical reaction device) shown in Figure 2. [Evaluation of Electrochemical Reaction Device (Cell)] The same procedure as in Example 1 was carried out.

[0158] Example 5 The same procedure as in Example 4 was carried out, except that a rectifying layer was inserted between the anode and cathode in the evaluation cell (electrochemical reaction device) as shown in Fig. 3. As the rectifying layer, a 200 µm thick PTFE mesh (mesh size: 0.2 mm (minor axis) × 0.9 mm (major axis), mesh shape: rhombus) was used.

[0159] (Example 6) [Preparation of catalyst and electrode] This was carried out in the same manner as in Example 4. [Preparation of electrochemical reaction device (cell)] Two vinyl chloride casings were prepared, and the casings were processed. A SUS current collector, a cathode or anode, and a tube hole were installed in each casing as shown in FIG. 5. A 4 mm thick frame (vinyl chloride) was prepared, and this was sandwiched between the two casings via a similarly shaped Teflon (registered trademark) sheet (packing) to prepare the evaluation cell (electrochemical reaction device) shown in FIG. 5. An ion exchange membrane (trade name: Nafion 117) constituting a separator layer was inserted into the evaluation cell to separate the anode side region from the cathode side region. [Evaluation of electrochemical reaction device (cell)] This was carried out in the same manner as in Example 1.

[0160] Example 7 [Catalyst Preparation] A first catalyst and a second catalyst were prepared in the same manner as in Example 1. [Electrode Preparation] Two sheets of carbon paper (product name "Toray 060", manufactured by Toray Industries, Inc.) were cut to 1 cm x 4 cm and prepared. 8 mg of the first catalyst and 40 μL of a 10% by mass dispersion of a catalyst additive (Nafion) were mixed, dispersed in 1600 μL of acetone, and spray-applied to carbon paper to obtain a cathode having a catalyst layer containing the first catalyst. Furthermore, 12 mg of the second catalyst and 60 μL of a 10% by mass dispersion of a catalyst additive (Nafion) were mixed, dispersed in 1600 μL of acetone, and spray-applied to carbon paper to obtain a cathode having a catalyst layer containing the second catalyst.

[0161] [Fabrication of Electrochemical Reaction Device (Cell)] Two vinyl chloride casings were prepared and processed, and a SUS current collector rod, a cathode and anode (or cathode), and tube holes were installed in each casing as shown in Fig. 6. A 4 mm thick frame (vinyl chloride) was prepared, and this was sandwiched between the two casings via a similarly shaped Teflon (registered trademark) sheet (packing) to fabricate an evaluation cell.

[0162] Example 8 The same procedure as in Example 3 was carried out, except that the second catalyst prepared as follows was used. [Preparation of second catalyst (PdAu-C)] 25 mg of Pd(NO ３ ) ２ ・2H２ O (Aldrich) and 37 mg of HAuCl ４ ・3H ２ O (manufactured by Aldrich) and 75 mg of Ketjen Black were dispersed in 50 ml of ion-exchanged water, dried, and heated at 300°C for 2 hours to obtain a second catalyst (PdAu-C). In the second catalyst, the molar ratio of Pd to Au was 50:50.

[0163] Example 9 The same procedure as in Example 3 was carried out, except that the first catalyst prepared as follows was used. [Preparation of first catalyst (Au / carbon)] 30 mg of HAuCl ４ ・3H ２ O (manufactured by Aldrich) and 60 mg of Ketjen black were dispersed in 50 ml of ion-exchanged water, dried, and then heated at 300°C for 0.5 hours to obtain a first catalyst (Au / carbon) in which nanogold particles were supported on carbon black.

[0164] Example 10 The same procedure as in Example 6 was carried out, except that the second catalyst was changed to PdAu—C prepared in the same manner as in Example 8.

[0165] Example 11 The same procedure as in Example 6 was carried out, except that the first catalyst was changed to Au / carbon prepared in the same manner as in Example 9.

[0166] Example 12 The same procedure as in Example 6 was carried out, except that the 0.1 M methanol solution of LiBr was changed to a 0.1 M mixed solution of ethylene glycol / acetonitrile (mixing ratio 50:50 (volume ratio)) as the electrolyte.

[0167] Example 13 The same procedure as in Example 6 was carried out, except that the electrolyte solution was changed from a 0.1 M methanol solution of LiBr to a 0.1 M ethanol solution.

[0168] Comparative Example 1 [Catalyst Preparation] A first catalyst and a second catalyst were prepared in the same manner as in Example 1. [Electrode Preparation] Two sheets of carbon paper (product name "Toray 060", manufactured by Toray Industries, Inc.) were cut to 1 cm x 4 cm and prepared. 8 mg of the first catalyst and 40 μL of a 10% by mass dispersion of a catalyst additive (Nafion) were mixed, dispersed in 1600 μL of acetone, and spray-applied to one of the carbon papers to obtain a cathode having a catalyst layer containing the first catalyst. Furthermore, 8 mg of the second catalyst and 40 μL of a 10% by mass dispersion of a catalyst additive (Nafion) were mixed, dispersed in 1600 μL of acetone, and spray-applied to the other carbon paper to obtain an anode having a catalyst layer containing the second catalyst.

[0169] [Cell Fabrication] Two vinyl chloride casings were prepared and processed to install a SUS current collector rod and an anode or cathode in each casing, as shown in FIG. 14 . A 4 mm thick vinyl chloride frame with tube holes (supply and exhaust ports) was prepared and sandwiched between the two casings via a similarly shaped Teflon (registered trademark) sheet (packing), to fabricate the evaluation cell shown in FIG. 14 . As shown in FIG. 14 , the evaluation cell had a cathode 121 with a first catalyst 126 and an anode 122 with a second catalyst 127 on wall surfaces 120B and 120A facing each other in the Y direction, respectively. A supply port 124 and an exhaust port 125 were provided on wall surfaces 120C and 120D facing each other in the X direction, respectively. Convection Y was formed so as to intersect the pair of opposing first catalysts 126 and second catalysts 127. As a result, the convection current Y was formed so that the electrolytic solution 123 was in uniform contact with the first catalyst 126 and the second catalyst 127 .

[0170] DMC = dimethyl carbonate EC = ethylene carbonate DEC = diethyl carbonate

[0171] As shown in Table 1, in Examples 1 to 13, in an electrochemical cell (electrochemical reaction device) including a cathode having a first catalyst, an anode, an electrolytic solution containing a reaction substrate and an electrolyte, and a second catalyst, the electrolytic solution had convection, and the direction of the convection was oriented so that the first catalyst and then the second catalyst came into contact. As a result, carbonyl compounds could be produced with a selectivity above a certain level, despite the simple configuration. In contrast, in Comparative Example 1, the convection F of the electrolytic solution was formed so that it evenly came into contact with the first catalyst and the second catalyst, and the convection Y was not formed so that the first catalyst and then the second catalyst came into contact. As a result, carbonyl compounds could not be produced with a selectivity above a certain level.

[0172] Example 14 An electrochemical reaction device was fabricated in the same manner as in Example 2 and evaluated by the following method. [Evaluation of Electrochemical Reaction Device] A 50 ml solvent bottle was filled with a 0.1 M NaBr solution in methanol, and carbon dioxide was bubbled through it for 15 minutes to prepare an electrolyte solution containing dissolved carbon dioxide. A diaphragm pump was used to pump and circulate the electrolyte at 15 ml / min, and a current of 24 mA / cm was applied between the cathode and anode. ２ A current of 0.015 was passed for 15 minutes to cause an electrochemical reaction. Furthermore, the second catalyst in the reaction zone was dispersed using a stirrer. The resulting electrolyte was analyzed by gas chromatography, and the selectivity of the target product (DMC) was calculated to be 31%.

[0173] Example 15: An ion exchange membrane (product name: Nafion 117) constituting a separator layer was inserted into the first reaction section (electrochemical cell) to separate the anode region from the cathode region. The same procedure as in Example 14 was repeated except that two first supply ports and two first discharge ports were provided in the frame to form the electrochemical reaction device shown in FIG. 9. The selectivity for the target product (DMC) was 38%.

[0174] Comparative Example 2 [Preparation of catalyst] A first catalyst and a second catalyst were prepared in the same manner as in Example 14. An evaluation cell similar to that in Comparative Example 1 was prepared, and convection F was formed so that the electrolytic solution 123 was in uniform contact with the first catalyst 126 and the second catalyst 127. When a current was applied in the same manner as in Example 14, the selectivity of the target product (DMC) was 8%.

[0175] (Example 16) [Preparation of catalyst] The first catalyst was prepared in the same manner as in Example 14. The second catalyst was prepared by adding 0.14 g of PdCl ２ (manufactured by Aldrich) (metal amount: 0.085 g) and 20 g of alumina beads were dispersed in 50 ml of ammonia water with a concentration of 26 mass %, dried, and heated at 200°C for 3 hours to obtain a second catalyst (Pd-Al ２ O ３ ) was obtained.

[0176] [Fabrication of Electrodes] Using the first catalyst and second catalyst obtained above, an anode and a cathode were fabricated on a substrate in the same manner as in Example 14. [Fabrication of Cell] The electrochemical reaction device was an electrochemical reaction device 80 having the configuration shown in FIG. 10 , except that the gas diffusion mechanism 69 was not provided, and the second reaction chamber 60Y was positioned so that the supply port 64B was on the upper side and the discharge port 65B was on the lower side, and the electrolytic solution 63 flowed vertically from top to bottom in the second reaction chamber 60Y. In fabricating the electrochemical reaction device 80, the second reaction chamber 60Y was filled with the second catalyst to form a catalyst layer.

[0177] [Cell Evaluation] A 50 ml solvent bottle was charged with a 0.1 M NaBr solution in methanol, and carbon dioxide was bubbled through it for 15 minutes to prepare an electrolyte solution containing dissolved carbon dioxide. A diaphragm pump was used to pump and circulate the electrolyte at a rate of 15 ml / min, and a current of 12 mA / cm was applied between the cathode and anode. ２ , 24mA / cm ２ , 48mA / cm ２ The electrochemical reaction was carried out by passing a current of 1.000 V for 15 minutes. The selectivity of the target product (DMC) is shown in Table 2 below.

[0178] Example 17 The first catalyst, the second catalyst, and the electrodes were prepared in the same manner as in Example 16. Furthermore, except that a gas diffusion mechanism was not provided, the electrochemical reaction device 90 was prepared in the same manner as in Example 11. An ion exchange membrane (product name: Nafion 117) was used as the isolation layer, and the electrochemical reaction device 90 was prepared in accordance with Example 16, but the first and second reaction chambers were arranged so that the electrolytic solution 13 flowed vertically from bottom to top.

[0179]

[0180] Examples 18 to 20 The first catalyst, second catalyst, and electrodes were prepared in the same manner as in Example 17. Furthermore, a cell was prepared so as to have the configuration of the electrochemical reaction device shown in Fig. 12, except that a gas diffusion mechanism was not provided. Specifically, the same procedures as in Example 17 were carried out, except that valves were provided so as to have the configuration shown in Fig. 12, and tubes were connected so as to have the configuration shown in Fig. 12.

[0181] [Cell Evaluation] A 50 ml solvent bottle was charged with a 0.1 M NaBr solution in methanol, and carbon dioxide was bubbled through it for 15 minutes to prepare an electrolyte solution containing dissolved carbon dioxide. A diaphragm pump was used to pump and circulate the electrolyte at a rate of 15 ml / min, and a current of 12 mA / cm was applied between the cathode and anode. ２ A current of 0.01 was passed for 15 minutes to cause an electrochemical reaction. During the 15-minute period, circulation and release were repeated the number of times shown in Table 3, with the circulation and release times shown in Table 3 below. As explained above, the circulation time is the state in which the electrolyte is flowed by convection F1, while the release time is the time during which the gas in the electrolyte (a mixed gas of carbon dioxide and carbon monoxide) is flowed by F3. The amount of electrolyte flowed by convection F1 during circulation was 15 ml / min. The selectivity of the target product (DMC) in each example is shown in Table 3 below.

[0182]

[0183] (Example 21) The first catalyst, second catalyst, and electrodes were prepared in the same manner as in Example 17. A cell was prepared so as to have the configuration of the electrochemical reaction device shown in FIG. 13, except that a gas diffusion mechanism was not provided. Specifically, the cell was prepared in the same manner as in Example 4, except that the tubes were connected in the configuration shown in FIG. 13. A current of 25 mA / cm was applied between the cathode and anode of the obtained cell. ２ , 50mA / cm ２ The experiment was carried out in the same manner as in Example 17, except that a current of 1000 kJ / min was applied for 15 minutes to cause an electrochemical reaction, and the evaluation was carried out based on the Faraday efficiency (FE) of the target substance (DMC). The results are shown in Table 4 below.

[0184] Example 22 The same procedure as in Example 21 was carried out, except that in the second reaction chamber 60Y, the electrolytic solution 63 was made to flow vertically from top to bottom. The results are shown in Table 4 below.

[0185]

[0186] The electrochemical reaction devices of Examples 14 to 22 described above comprised an electrochemical cell (first reaction section) equipped with a cathode and an anode having a first catalyst, a second reaction section having a second catalyst, and an electrolyte solution containing a reaction substrate and an electrolyte. The electrolytic solution flowed in a convection direction through the electrochemical cell (first reaction section) and then through the second reaction section, thereby increasing the selectivity of the target product. Furthermore, as shown in Examples 16, 17, 21, and 22, even when the current density was increased, the selectivity of the target product remained above a certain level, and it was clear that production volume could be increased while suppressing power consumption. In contrast, the electrochemical reaction device of Comparative Example 2 did not have a convection direction in which the electrolyte flowed through the electrochemical cell and then through the reaction section, making it difficult to increase the selectivity of the target product.

[0187] 10, 20, 30, 30A, 40, 50 Electrochemical reaction device (electrochemical cell) 60, 70, 80, 90, 100, 110 Electrochemical reaction device 10X, 20X, 60X First reaction chamber (first reaction section, electrochemical cell) 10Y, 30Y, 60Y Second reaction chamber (second reaction section) 11, 21, 51, 61 Cathode 12, 22, 52, 62 Anode 13, 23, 53, 63 Electrolyte 14, 24, 34A, 34B, 54A, 54B, 64A, 64B, 64A1, 64A2, 64B1, 64B2 Supply port 15, 25, 35A, 35B, 55A, 55B, 65A, 65B, 65A1, 65A2 Discharge port 16, 26, 56, 66 First catalyst 17, 27, 57, 67 Second catalyst 31, 32 Rectification layer 41, 71 Separation layer 70A Cathode chamber 70B Anode chamber

Claims

1. An electrochemical cell comprising a cathode having a first catalyst that reduces carbon dioxide to carbon monoxide, an anode, and an isolation layer, A reaction section having a second catalyst for synthesizing an oxygen-containing organic substance from carbon monoxide and a reaction substrate, The system comprises a reaction substrate and an electrolyte solution containing an electrolyte, The inside of the electrochemical cell is isolated by the isolation layer into a cathode-side region and an anode-side region. The electrolyte has a convection direction in which it flows in the order of the electrochemical cell and the reaction section, An electrochemical reaction apparatus having convection in which the electrolyte circulates between the anode region and the reaction section.

2. The electrochemical reaction apparatus according to claim 1, wherein the electrolyte flowing from the anode region to the reaction section includes an oxidized product generated at the anode.

3. The electrochemical reaction apparatus according to claim 2, wherein the oxidizer is a halogen.

4. The electrochemical reaction apparatus according to claim 1, wherein the electrolyte has convection that circulates so that it is discharged from the cathode-side region to the outside of the electrochemical cell and then returns to the cathode-side region.

5. The electrochemical reaction apparatus according to any one of claims 1 to 4, further comprising convection flowing from the cathode region to a path through which convection circulates between the anode region and the reaction section, thereby supplying the gas in the electrolyte to the reaction section.

6. The electrochemical reaction apparatus according to claim 5, wherein the gas contains carbon monoxide.

7. The electrochemical reaction apparatus according to any one of claims 1 to 4, further comprising convection for supplying gas in the electrolyte to the reaction section from the cathode side region.

8. The reaction section comprises a catalyst layer containing the second catalyst, The second catalyst is an active particle-containing catalyst comprising a support and active particles containing a metal element supported on the support, The electrochemical reaction apparatus according to any one of claims 1 to 4, wherein the amount of metal in the active particles in the catalyst layer is 0.1 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the support body.

9. The electrochemical reaction apparatus according to any one of claims 1 to 4, wherein the second catalyst is a catalyst for synthesizing a carbonyl compound from carbon monoxide and a reaction substrate.

10. An electrochemical cell comprising a cathode having a first catalyst that reduces carbon dioxide to carbon monoxide, an anode, and an isolation layer, A reaction section having a second catalyst for synthesizing an oxygen-containing organic substance from carbon monoxide and a reaction substrate, An electrochemical reaction apparatus comprising a reaction substrate and an electrolyte solution containing an electrolyte, wherein a method for producing an oxygen-containing organic substance from carbon dioxide is used, The inside of the electrochemical cell is isolated by the isolation layer into a cathode-side region and an anode-side region. In the electrolyte, a convection direction is formed in which the flow is in the order of the electrochemical cell and the reaction section. A method for producing an oxygen-containing organic substance, wherein the electrolyte forms convection that circulates between the anode region and the reaction section.

11. The method for producing an oxygen-containing organic substance according to claim 10, further comprising flowing the gas in the electrolyte from the cathode-side region into the path through which the circulating convection flows, thereby forming convection that supplies the gas to the reaction section.

12. The method for producing an oxygen-containing organic substance according to claim 10, further comprising forming convection that supplies gas from the electrolyte to the reaction section from the cathode-side region.