JP6786426B2 - Electrochemical reduction device and method for producing a hydrogenated product of an aromatic hydrocarbon compound - Google Patents

Description

The present invention relates to a separator for an electrolytic cell, an electrolytic cell, an electrochemical reduction device, and a method for producing a hydrogenated product of an aromatic hydrocarbon compound. In particular, the present invention comprises a separator used in an electrolytic cell that electrochemically hydrogenates an aromatic hydrocarbon compound, an electrolytic cell having the separator for the electrolytic cell, an electrochemical reduction device provided with the electrolytic cell, and the electrolysis. The present invention relates to a method for producing a hydrogenated product of an aromatic hydrocarbon compound using a cell.

Cyclic organic compounds such as cyclohexane and decalin are known to be efficiently obtained by nuclear hydrogenation of the corresponding aromatic hydrocarbon compounds (benzene, naphthalene) using hydrogen gas. This reaction requires high temperature and high pressure reaction conditions. Therefore, it is not suitable for small to medium scale manufacturing. On the other hand, in the electrochemical reaction using an electrolytic cell, water can be used as a hydrogen source. Therefore, it is not necessary to handle gaseous hydrogen, and it is known that the reaction conditions proceed at relatively mild conditions (normal temperature to 200 ° C., normal pressure). For example, in Patent Documents 1 and 2, a cathode catalyst layer for reducing an aromatic hydrocarbon compound such as toluene and an anode catalyst layer for oxidizing water are arranged so as to sandwich a proton-conducting electrolyte membrane. An organic hydride production apparatus comprising a assembly is disclosed.

Japanese Unexamined Patent Publication No. 2012-0272477 International Publication No. 11/122155 Pamphlet

As a result of diligent studies on a technique for electrochemically hydrogenating an aromatic hydrocarbon compound, the present inventors have room to improve the efficiency of hydrogenating an aromatic hydrocarbon compound in the conventional technique. I came to recognize that.

The present invention has been made in view of these circumstances, and an object of the present invention is to provide a technique for improving the efficiency of hydrogenating an aromatic hydrocarbon compound.

One aspect of the present invention is a separator for an electrolytic cell. The separator for an electrolytic cell is a separator for an electrolytic cell that hydrogenates an aromatic hydrocarbon compound by an electrochemical reduction reaction, and the aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer of the electrolytic cell is distributed. It has a conductive porous layer.

Another aspect of the present invention is an electrolytic cell. The electrolytic cell is provided with an electrolyte membrane having proton conductivity, a reducing electrode catalyst layer provided on one side of the electrolyte membrane for hydrogenating an aromatic hydrocarbon compound, and the one side of the electrolyte membrane. An oxygen-evolving electrode catalyst layer provided on the opposite side for oxidizing water to generate protons, an electrolytic cell separator of the above embodiment provided on the reducing electrode catalyst layer side, and an oxygen-evolving electrode catalyst layer side. It is provided with another separator for an electrolytic cell, which is arranged in and has a flow path portion through which water flows.

Yet another aspect of the present invention is an electrochemical reduction device. The electrochemical reduction apparatus includes an electrolytic cell according to the above embodiment, and a supply unit for supplying an aromatic hydrocarbon compound to the reducing electrode catalyst layer included in the electrolytic cell via a separator for an electrolytic cell. Liquid aromatic hydrocarbons so that the difference between the pressure of the aromatic hydrocarbon compound supplied to the porous layer of the separator for an electrolytic cell and the pressure of the aromatic hydrocarbon compound flowing out of the porous layer is more than 9 kPa. Supply hydrogen compounds.

Yet another aspect of the present invention is a method for producing a hydrogenated product of an aromatic hydrocarbon compound. In the production method, an aromatic hydrocarbon compound is supplied to the reducing electrode catalyst layer of the electrolytic cell according to the above embodiment at a ratio of 10% or less of an unhydrogenated material and 90% or more of a hydrogenated material to obtain an aromatic hydrocarbon compound. Includes hydrogenating unhydrogenated materials.

According to the present invention, the efficiency of hydrogenating an aromatic hydrocarbon compound can be improved.

It is a schematic diagram which shows the schematic structure of the electrochemical reduction apparatus including the electrolytic cell which concerns on Embodiment 1. FIG. It is sectional drawing which shows the schematic structure of the electrolytic cell which concerns on Embodiment 1. FIG. It is a top view of the separator seen from the reduction electrode side. It is a graph which shows the relationship between the electric potential and the current density when the concentration of the unhydrogenated form of an aromatic hydrocarbon compound is made different. It is a schematic diagram which shows the schematic structure of the electrochemical reduction apparatus which concerns on Embodiment 2. It is sectional drawing which shows the schematic structure of the electrolytic cell which concerns on modification 1. FIG. It is a top view of the separator which concerns on modification 2 seen from the reduction electrode side. It is a graph which shows the relationship between the electric potential and the current density in the electrolytic cell of Example 1 and Comparative Example 1. FIG. 9A is a diagram showing the volume vacancy rate, the pressure difference, the pressure rise rate, and the diffusion limit current density in each Example and Comparative Example. FIG. 9B is a graph showing the relationship between the cell inlet pressure and the diffusion limit current density at a compound flow rate of 20 mL / min in each Example and Comparative Example. It is a graph which shows the relationship between the supply flow rate of an aromatic hydrocarbon compound, and the cell inlet pressure.

Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The embodiments are not limited to the invention, but are exemplary, and all the features and combinations thereof described in the embodiments are not necessarily essential to the invention. The same or equivalent components, members, and processes shown in the drawings shall be designated by the same reference numerals, and redundant description will be omitted as appropriate. In addition, the scale and shape of each part shown in each figure are set for convenience in order to facilitate explanation, and are not limitedly interpreted unless otherwise specified. In addition, terms such as "first" and "second" used in the present specification or claims do not represent any order or importance, but are intended to distinguish one configuration from another. Is.

(Embodiment 1)
FIG. 1 is a schematic diagram showing a schematic configuration of an electrochemical reduction device including the electrolytic cell according to the first embodiment. In FIG. 1, the separator provided in the electrolytic cell is not shown, and the structure of the membrane electrode assembly is simplified. The electrochemical reduction device 10 is a device that hydrogenates an aromatic hydrocarbon compound by an electrochemical reduction reaction, and includes an electrolytic cell 100, a power control unit 20, an organic substance storage tank 30, a water storage tank 40, a gas-water separation unit 50, and the like. A control unit 60 is provided.

The power control unit 20 is, for example, a DC / DC converter that converts the output voltage of a power source into a predetermined voltage. The positive electrode output terminal of the power control unit 20 is connected to the oxygen generating electrode (positive electrode) 130 of the electrolytic cell 100. The negative electrode output terminal of the power control unit 20 is connected to the reduction electrode (negative electrode) 120 of the electrolytic cell 100. As a result, a predetermined voltage is applied between the oxygen evolution electrode 130 and the reduction electrode 120 of the electrolytic cell 100. The power control unit 20 may be provided with reference electrodes for the purpose of detecting positive and negative potentials. In this case, the reference electrode input terminal is connected to the reference electrode 112 provided on the electrolyte membrane 110. The electric potential in the present application means an electric potential with respect to a reversible hydrogen electrode (RHE).

The control unit 60 controls the outputs of the positive electrode output terminal and the negative electrode output terminal of the power control unit 20 so that the potential of the oxygen generating electrode 130 or the reducing electrode 120 becomes a desired potential. The control unit 60 is realized by elements and circuits such as a computer CPU and memory as a hardware configuration, and is realized by a computer program or the like as a software configuration. This is of course understood by those skilled in the art. The power source is not particularly limited, but ordinary grid power may be used, and power derived from natural energy such as solar power and wind power can also be preferably used.

Aromatic hydrocarbon compounds are stored in the organic matter storage tank 30. The aromatic hydrocarbon compound used in this embodiment is a compound containing at least one aromatic ring. Examples of the aromatic hydrocarbon compound include benzene, naphthalene, anthracene, diphenylethane and the like. These may be used alone or in combination. Further, alkylbenzene and alkylnaphthalene having a structure in which hydrogen atoms 1 to 4 of the aromatic ring of the above compound are substituted with, for example, a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group may be used. For example, examples of monoalkylbenzene include toluene, ethylbenzene and the like. Examples of dialkylbenzene include xylene and diethylbenzene. Further, examples of the trialkylbenzene include mesitylene and the like. Examples of alkylnaphthalene include methylnaphthalene and the like. Further, the aromatic ring of the above-mentioned aromatic hydrocarbon may have 1 to 3 substituents other than the alkyl group. The aromatic hydrocarbon compound is preferably at least one of toluene and benzene. The electrochemical reduction apparatus 10 can also use nitrogen-containing heterocyclic aromatic compounds such as pyridine, pyrimidine, pyrazine, quinoline, isoquinoline, N-alkylpyrrole, N-alkylindole, and N-alkyldibenzopyrrole. Similar to aromatic hydrocarbon compounds, nitrogen-containing heterocyclic aromatic compounds may be substituted with alkyl groups or other substituents.

The aromatic hydrocarbon compound is preferably liquid at room temperature. When a mixture of a plurality of the above-mentioned aromatic hydrocarbon compounds is used, the mixture may be a liquid. When the aromatic hydrocarbon compound is liquid at room temperature, the aromatic hydrocarbon compound can be supplied to the electrolytic cell 100 in a liquid state without performing treatments such as heating and pressurization. As a result, the configuration of the electrochemical reduction device 10 can be simplified.

The aromatic hydrocarbon compound stored in the organic matter storage tank 30 is supplied to the reducing electrode 120 of the electrolytic cell 100 by the first liquid supply device 32. As the first liquid supply device 32, for example, various pumps such as a gear pump or a cylinder pump, a natural flow type device, or the like can be used. A circulation path is provided between the organic matter storage tank 30 and the reducing electrode 120. The circulation route may not be provided. The aromatic hydrocarbon compound (hydrogenated product of the aromatic hydrocarbon compound) nuclear-hydrogenated by the electrolytic cell 100 and the unreacted aromatic hydrocarbon compound (unhydrogenated product of the aromatic hydrocarbon compound) are It is stored in the organic matter storage tank 30 via the circulation route. Gas is not generated in the main reaction that proceeds at the reduction electrode 120, but when gas such as hydrogen is by-produced, a gas-liquid separation means may be provided in the middle of the circulation path.

In the water storage tank 40, for example, ion-exchanged water, pure water, or an aqueous solution obtained by adding an acid such as sulfuric acid to these (hereinafter, as appropriate, simply referred to as "water") is stored. The water stored in the water storage tank 40 is supplied to the oxygen generating electrode 130 of the electrolytic cell 100 by the second liquid supply device 42. As the second liquid supply device 42, for example, various pumps such as a gear pump or a cylinder pump, a natural flow type device, or the like can be used. A circulation path is provided between the water storage tank 40 and the oxygen evolution electrode 130. The circulation route may not be provided. The unreacted water in the electrolytic cell 100 is stored in the water storage tank 40 via the circulation path. A brackish water separation unit 50 is provided in the middle of the circulation path. Gases such as oxygen generated by the electrolysis of water in the electrolytic cell 100 are separated from water by the brackish water separation unit 50 and discharged to the outside of the system.

FIG. 2 is a cross-sectional view showing a schematic configuration of the electrolytic cell according to the first embodiment. The electrolytic cell 100 includes a membrane electrode assembly 102 and a pair of separators 150a and 150b that sandwich the membrane electrode assembly. The membrane electrode assembly 102 has an electrolyte membrane 110, a reducing electrode 120, and an oxygen generating electrode 130.

The electrolyte membrane 110 is formed of a material having proton conductivity (ionomer). While the electrolyte membrane 110 selectively conducts protons, it suppresses the mixing and diffusion of substances between the reducing electrode 120 and the oxygen evolution electrode 130. The thickness of the electrolyte membrane 110 is preferably 5 to 300 μm, more preferably 10 to 150 μm, and even more preferably 20 to 100 μm. By setting the thickness of the electrolyte membrane 110 to 5 μm or more, the barrier property of the electrolyte membrane 110 can be ensured, and the generation of cross leaks of aromatic hydrocarbon compounds, oxygen, and the like can be more reliably suppressed. Further, by setting the thickness of the electrolyte membrane 110 to 300 μm or less, it is possible to prevent the ion transfer resistance from becoming excessive.

The area resistance of the electrolyte membrane 110, that is, the ion transfer resistance per geometric area is preferably 2000 mΩ · cm ² or less, more preferably 1000 mΩ · cm ² or less, and further preferably 500 mΩ · cm ² or less. By setting the area resistance of the electrolyte membrane 110 to 2000 mΩ · cm ² or less, it is possible to more reliably avoid the possibility of insufficient proton conductivity. Examples of the material having proton conductivity include perfluorosulfonic acid polymers such as Nafion (registered trademark) and Flemion (registered trademark). The ion exchange capacity (IEC) of the cation exchange type ionomer is preferably 0.7 to 2 meq / g, more preferably 1 to 1.3 meq / g. By setting the ion exchange capacity of the cation exchange type ionomer to 0.7 meq / g or more, it is possible to more reliably avoid the possibility of insufficient ion conductivity. On the other hand, by setting the ion exchange capacity to 2 meq / g or less, it is possible to more reliably avoid the possibility that the solubility of ionomer in water or an aromatic hydrocarbon compound increases and the strength of the electrolyte membrane 110 becomes insufficient. Can be done.

The electrolyte membrane 110 may be mixed with a reinforcing material such as porous PTFE (polytetrafluoroethylene). By introducing the reinforcing material, it is possible to suppress a decrease in the dimensional stability of the electrolyte membrane 110 due to an increase in the ion exchange capacity. Thereby, the durability of the electrolyte membrane 110 can be improved. In addition, crossover of aromatic hydrocarbon compounds and oxygen can be suppressed.

As shown in FIG. 1, the reference electrode 112 may be provided in the region of the electrolyte membrane 110 away from the reducing electrode 120 and the oxygen evolution electrode 130 so as to be in contact with the electrolyte membrane 110. The reference electrode 112 is electrically isolated from the reducing electrode 120 and the oxygen evolving electrode 130. The reference electrode 112 is held at the reference electrode potential. Examples of the reference electrode 112 include a reversible hydrogen electrode (reference electrode potential = 0V), an Ag / AgCl electrode (reference electrode potential = 0.199V), and the like. The reference electrode 112 is preferably installed on the surface of the electrolyte membrane 110 on the reduction electrode 120 side.

The current flowing between the reduction electrode 120 and the oxygen evolution electrode 130 is detected by the current detection unit 113 shown in FIG. The current detection unit 113 is composed of, for example, a conventionally known ammeter. The current value detected by the current detection unit 113 is input to the control unit 60 and used for the control of the power control unit 20 by the control unit 60. The potential difference between the reference electrode 112 and the reducing electrode 120 is detected by the voltage detection unit 114. The voltage detection unit 114 is composed of, for example, a conventionally known voltmeter. The value of the potential difference detected by the voltage detection unit 114 is input to the control unit 60 and used for the control of the power control unit 20 by the control unit 60.

The reduction electrode 120 is provided on one side of the electrolyte membrane 110. In the present embodiment, the reducing electrode 120 is provided so as to be in contact with one main surface of the electrolyte membrane 110. The reducing electrode 120 has a structure in which a reducing electrode catalyst layer 122, a dense layer 126, and a diffusion layer 124 are laminated. The reducing electrode catalyst layer 122 is arranged closer to the electrolyte membrane 110, the diffusion layer 124 is arranged closer to the separator 150a, and the dense layer 126 is arranged between the reducing electrode catalyst layer 122 and the diffusion layer 124.

The reducing electrode catalyst layer 122 is provided in contact with one main surface of the electrolyte membrane 110. The reduction electrode catalyst layer 122 contains a reduction catalyst for hydrogenating an aromatic hydrocarbon compound. The reduction catalyst used in the reduction electrode catalyst layer 122 includes, for example, at least one of Pt and Pd. Further, the reduction catalyst includes a first catalyst metal (precious metal) composed of at least one of Pt and Pd, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Sn, W, Re and Pb. It may be composed of a metal composition containing one kind or two or more kinds of second catalyst metals selected from Bi. In this case, examples of the form of the metal composition include an alloy of a first catalyst metal and a second catalyst metal, an intermetallic compound composed of a first catalyst metal and a second catalyst metal, and the like. The ratio of the first catalyst metal to the total mass of the first catalyst metal and the second catalyst metal is preferably 10 to 95 wt%, more preferably 20 to 90 wt%, still more preferably 25 to 80 wt%. Is. By setting the ratio of the first catalyst metal to 10 wt% or more, it is possible to more reliably suppress a decrease in durability (dissolution resistance, etc.). On the other hand, by setting the ratio of the first catalyst metal to 95 wt% or less, it is possible to prevent the properties of the reduction catalyst from approaching the properties of the noble metal alone, and to more reliably suppress insufficient electrode activity. Can be done. In the following description, the first catalyst metal and the second catalyst metal are collectively referred to as "catalyst metal" as appropriate.

The catalyst metal described above may be supported by a catalyst carrier composed of an electron conductive material. The electron conductivity of the electron conductive material used for the catalyst carrier is preferably 1.0 × 10 ^-2 S / cm or more, more preferably 3.0 × 10 ^-2 S / cm or more, and further preferably. Is 1.0 × 10 ^-1 S / cm or more. By setting the electronic conductivity of the electron conductive material to 1.0 × 10 ^-2 S / cm or more, the electron conductivity can be more reliably imparted to the reducing electrode catalyst layer 122.

Examples of the catalyst carrier include an electron conductive material containing any one of a porous carbon (mesoporous carbon and the like), a porous metal, and a porous metal oxide as a main component. Examples of the porous carbon include carbon blacks such as Ketjen Black (registered trademark), acetylene black, and Vulcan (registered trademark). The BET specific surface area of the porous carbon measured by the nitrogen adsorption method is preferably 50 m ² / g or more and 1500 m ² / g or less, more preferably 500 m ² / g or more and 1300 m ² / g or less, and further preferably 700 m. ^{It is 2} / g or more and 1000 m ² / g or less. By setting the BET specific surface area of the porous carbon to 50 m ² / g or more, it is possible to easily support the catalyst metal uniformly, and thereby the diffusivity of the aromatic hydrocarbon compound can be more reliably ensured. .. Further, by setting the BET specific surface area of the porous carbon to 1500 m ² / g or less, the catalyst carrier is likely to be deteriorated at the time of the reaction of the aromatic hydrocarbon compound or at the time of starting or stopping the electrochemical reduction device 10. Can be avoided. Thereby, sufficient durability can be imparted to the catalyst carrier.

Examples of the porous metal include Pt black, Pd black, and Pt metal precipitated in a fractal shape. Examples of the porous metal oxide include oxides of Ti, Zr, Nb, Mo, Hf, Ta, and W. Further, the catalyst carrier is a porous metal compound such as a metal nitride such as Ti, Zr, Nb, Mo, Hf, Ta, W, a carbide, an acid nitride, a carbonitride, and a partially oxidized carbonitride. (Hereinafter, appropriately referred to as a porous metal nitride or the like) can also be used. The BET specific surface area of the porous metal, the porous metal oxide, the porous metal carbonitride and the like measured by the nitrogen adsorption method is preferably 1 m ² / g or more, more preferably 3 m ² / g or more. More preferably, it is 10 m ² / g or more. By setting the BET specific surface area of the porous metal, the porous metal oxide, the porous metal carbonitride, etc. to 1 m ² / g or more, it is possible to easily support the catalyst metal uniformly.

The catalyst carrier carrying the catalyst metal is preferably coated with an ionomer. Thereby, the ionic conductivity of the reducing electrode catalyst layer 122 can be improved. Examples of ionomers include perfluorosulfonic acid polymers such as Nafion (registered trademark) and Flemion (registered trademark). The ion exchange capacity (IEC) of the ionomer is preferably 0.7 to 3 meq / g, more preferably 1 to 2.5 meq / g, and even more preferably 1.2 to 2 meq / g. When the catalyst carrier is porous carbon, the mass ratio I / C of the ionomer (I) / catalyst carrier (C) is preferably 0.1 to 2, more preferably 0.2 to 1.5. , More preferably 0.3 to 1.1. By setting the mass ratio I / C to 0.1 or more, sufficient ionic conductivity can be obtained more reliably. On the other hand, by setting the mass ratio I / C to 2 or less, it is possible to suppress the excessive coating thickness of the ionomer with respect to the catalyst metal and inhibit the contact of the aromatic hydrocarbon compound as a reactant with the catalytic active site. It is possible to avoid being done.

The ionomer contained in the reducing electrode catalyst layer 122 is preferably partially coated with the catalyst metal. According to this, the three elements (aromatic hydrocarbon compound, proton, electron) necessary for the electrochemical reaction in the reducing electrode catalyst layer 122 can be efficiently supplied to the reaction field.

The thickness of the reducing electrode catalyst layer 122 is preferably 1 to 100 μm, more preferably 10 to 30 μm. As the thickness of the reducing electrode catalyst layer 122 increases, the transfer resistance of protons increases, and the diffusivity of the aromatic hydrocarbon compound tends to decrease. Therefore, it is desirable to adjust the thickness of the reducing electrode catalyst layer 122 within the above range.

The diffusion layer 124 has a function of uniformly diffusing the liquid aromatic hydrocarbon compound supplied from the separator 150a, which will be described later, into the reducing electrode catalyst layer 122. The material constituting the diffusion layer 124 preferably has a high affinity for the aromatic hydrocarbon compound. As the material constituting the diffusion layer 124, for example, carbon paper, carbon woven fabric, or non-woven fabric can be used. When carbon paper is used as the material constituting the diffusion layer 124, the thickness of the diffusion layer 124 is preferably 50 to 1000 μm, more preferably 100 to 500 μm. The electron conductivity of the material constituting the diffusion layer 124 is preferably ^10-2 S / cm or more.

The dense layer 126 (MPL) has a function of promoting diffusion of liquid aromatic hydrocarbon compounds and hydrogenated products of aromatic hydrocarbon compounds in the plane direction of the reducing electrode catalyst layer 122. The dense layer 126 is formed by applying, for example, a paste-like kneaded product obtained by kneading a conductive powder and a water repellent to the surface of the diffusion layer 124 and drying it. As the conductive powder, for example, conductive carbon such as Vulcan (registered trademark) can be used. As the water repellent, for example, a fluorine-based resin such as tetrafluoroethylene resin (PTFE) can be used. The ratio of the conductive powder to the water repellent is appropriately determined within a range in which the desired conductivity and water repellency can be obtained. As an example, when Vulcan (registered trademark) is used as the conductive powder and PTFE is used as the water repellent, the mass ratio (Vulcan: PTFE) is, for example, 4: 1 to 1: 1.

The average pore diameter of the dense layer 126 is preferably 100 nm to 20 μm, more preferably 500 nm to 5 μm. The thickness of the dense layer 126 is preferably 1 to 50 μm, more preferably 2 to 20 μm. When the dense layer 126 is formed so as to fall inside the surface of the diffusion layer 124, the average film thickness of the dense layer 126 itself including the portion hidden in the diffusion layer 124 is calculated as the dense layer. Defined as a thickness of 126.

The separator 150a (separator for an electrolytic cell) is arranged on the side of the reducing electrode catalyst layer 122 in the electrolytic cell 100. In the present embodiment, the separator 150a is laminated on the main surface of the reducing electrode 120 on the opposite side of the electrolyte membrane 110. FIG. 3 is a plan view of the separator 150a as seen from the reduction electrode 120 side. As shown in FIGS. 2 and 3, the separator 150a includes a main body portion 154 and a porous body layer 156. Both the main body portion 154 and the porous body layer 156 have conductivity.

The main body portion 154 is a plate-like body having a recess 158 on the main surface facing the reducing electrode 120 side. The main body 154 is made of, for example, a carbon resin, Cr-Ni-Fe-based, Cr-Ni-Mo-Fe-based, Cr-Mo-Nb-Ni-based, Cr-Mo-Fe-W-Ni-based, Ti-based, or the like. It can be formed of a corrosion resistant alloy. A supply port 160 and a discharge port 162 are provided at predetermined positions of the main body portion 154. The liquid aromatic hydrocarbon compound supplied from the organic matter storage tank 30 flows into the recess 158 from the supply port 160. Further, the nuclear-hydrogenated aromatic hydrocarbon compound and the unreacted aromatic hydrocarbon compound in the reducing electrode 120 are sent out from the discharge port 162 to the outside of the main body 154.

The porous layer 156 is arranged in the recess 158. The aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer 122 flows through the pores of the porous layer 156. The pores in the porous layer 156 form a flow path 159 for the aromatic hydrocarbon compound. The liquid aromatic hydrocarbon compound supplied from the organic matter storage tank 30 penetrates from the porous layer 156 into the diffusion layer 124. That is, the separator 150a has a flow path 159 stretched in a net shape on the main surface facing the reducing electrode 120 side. Turbulence F of an aromatic hydrocarbon compound is generated in this flow path 159. Thereby, the aromatic hydrocarbon compound can be more uniformly supplied to the entire area of the porous layer 156. Therefore, the aromatic hydrocarbon compound can be uniformly supplied by the reducing electrode catalyst layer 122.

The porous layer 156 is composed of, for example, a sintered body of metal powder 164. As the material of the metal powder 164, various materials can be selected according to the required corrosion resistance, oxidation resistance, thermal expansion characteristics, thermal conductivity, electrical conductivity and the like. Specific examples of the material of the metal powder 164 include stainless steel such as low-carbon austenite-based stainless steel, Ni-based corrosion-resistant superalloy (INCONEL (registered trademark), Hastelloy (registered trademark), etc.), and Ni—Cu-based corrosion-resistant alloy (MONEL). (Registered trademark), etc.), oxidation-resistant alloys (high chromium alloys, etc.), etc.

The average particle size of the metal powder 164 is preferably 1 μm or more and 1000 μm or less. The "average particle size" is defined as the cumulative 50% particle size in the volume distribution of the metal powder used. The average particle size can be measured by a laser diffraction / scattering method. By setting the average particle size of the metal powder 164 to 1 μm or more, it is possible to sufficiently secure connecting pores composed of a space surrounded by a plurality of metal powders. As a result, excellent mass transfer of the aromatic hydrocarbon compound flowing through the pores can be ensured, and the aromatic hydrocarbon compound can be uniformly distributed. Further, by setting the average particle size of the metal powder 164 to 1000 μm or less, a sufficient contact point between the metal powders can be secured. As a result, the sintering strength of the porous layer 156 is maintained, so that the collapse and chipping of the porous layer 156 can be suppressed. Moreover, the aromatic hydrocarbon compound can be uniformly distributed.

The metal powder 164 is produced, for example, by an atomizing method, more preferably a gas atomizing method. When the metal powder 164 produced by the gas atomization method is used, the metal powders 164 can be sintered in a state where they are in substantially point contact with each other. As a result, in the obtained porous layer 156, the pores are sufficiently connected. As a result, the flow path resistance of the aromatic hydrocarbon compound in the porous layer 156 can be reduced.

As the sintering method of the metal powder 164, vacuum sintering, sintering in a reducing atmosphere such as hydrogen, sintering in an inert gas such as argon or nitrogen, air sintering and the like can be adopted. .. If necessary, press working, cutting, polishing, hydrophobic treatment, etc. may be performed during or after sintering.

The layer thickness of the porous layer 156 is preferably 10 μm or more and 2000 μm or less. The "layer thickness" is defined as the distance from the point closest to the bottom surface of the recess 158 in the porous layer 156 to the point closest to the reducing electrode catalyst layer 122. The layer thickness of the porous layer 156 can be measured by observing a cross section using a scanning electron microscope or the like. By setting the thickness of the porous layer 156 to 10 μm or more, the flow path 159 of the aromatic hydrocarbon compound can be formed more reliably. In addition, the strength of the porous layer 156 can be ensured. Further, by setting the thickness of the porous layer 156 to 2000 μm or less, it is possible to suppress a decrease in diffusivity of the aromatic hydrocarbon compound. The thickness of the separator 150a is, for example, 1 mm or more and 50 mm or less. Further, the depth of the recess 158 is preferably smaller than the layer thickness of the porous layer 156. As a result, the porous layer 156 can be brought into close contact with the diffusion layer 124 (in the case of the modification 1 described later, the reducing electrode catalyst layer 122). As a result, the aromatic hydrocarbon compound can be uniformly supplied to the reducing electrode catalyst layer 122.

The volumetric porosity of the porous layer 156 is preferably 5% or more and 95% or less. The "volume vacancy ratio" is the ratio of the volume of vacancy to the total volume of the porous layer 156. The volume vacancy ratio can be calculated by calculation from a cross-sectional image of the porous layer 156 obtained by using a scanning electron microscope. Alternatively, the volume vacancy ratio can be measured by a mercury intrusion method or the like. By setting the volume vacancy ratio of the porous layer 156 to 5% or more, the flow path 159 of the aromatic hydrocarbon compound is more reliably formed, and the deterioration of the performance of the electrolytic cell 100 due to the blockage of the flow path 159 is suppressed. Can be done. Further, by setting the volume vacancy ratio of the porous body layer 156 to 95% or less, the strength of the porous body layer 156 can be ensured. In addition, the decrease in diffusivity of the aromatic hydrocarbon compound can be suppressed.

The average pore diameter of the porous layer 156 is preferably 1 μm or more and 1000 μm or less. The "average pore diameter" can be calculated by calculation from a cross-sectional image of the porous layer 156 obtained by using a scanning electron microscope. Alternatively, the average pore diameter can be measured by image analysis using a focused ion beam scanning electron microscope or the like. The same applies to the average pore diameter of the dense layer 126. By setting the average pore diameter of the porous layer 156 to 1 μm or more, it is possible to more reliably form the flow path 159 of the aromatic hydrocarbon compound and suppress the deterioration of the performance of the electrolytic cell 100 due to the blockage of the flow path 159. it can. Further, by setting the average pore diameter of the porous body layer 156 to 1000 μm or less, the strength of the porous body layer 156 can be ensured.

The oxygen evolution electrode 130 is an electrode for oxidizing water to generate protons, and is provided on the side opposite to one side (the side on which the reduction electrode 120 is arranged) of the electrolyte membrane 110. In the present embodiment, the oxygen evolution electrode 130 is provided so as to be in contact with the other main surface of the electrolyte membrane 110, but the oxygen evolution electrode 130 may be separated from the electrolyte membrane 110. The oxygen evolution electrode 130 has a structure in which an oxygen evolution electrode catalyst layer 132 and a diffusion layer 134 are laminated. The oxygen-evolving electrode catalyst layer 132 is arranged closer to the electrolyte membrane 110 than the diffusion layer 134. The diffusion layer 134 may not be provided.

The oxygen evolution electrode catalyst layer 132 contains one or more metals or metal oxides selected from Ru, Rh, Pd, Ir, and Pt as catalysts. These catalysts may be dispersed-supported or coated on a metal substrate having electron conductivity. Such a metal base material is composed of a metal such as Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ta, W, or an alloy containing these as a main component. Examples thereof include metal fibers (fiber diameter: for example, 10 to 30 μm), meshes (mesh diameter: for example, 500 to 1000 μm), sintered bodies of porous metals, foam molded bodies (foam), expanded metals, and the like. The thickness of the oxygen-evolving electrode catalyst layer 132 is preferably 0.1 to 10 μm, more preferably 0.2 to 5 μm.

The diffusion layer 134 has a function of uniformly diffusing the water supplied from the separator 150b, which will be described later, into the oxygen evolution electrode catalyst layer 132. The material constituting the diffusion layer 134 preferably has a high affinity for water. As the material constituting the diffusion layer 134, for example, carbon paper, carbon woven fabric, or non-woven fabric can be used. When carbon paper is used as the material constituting the diffusion layer 134, the thickness of the diffusion layer 134 is preferably 50 to 1000 μm, more preferably 100 to 500 μm. The electron conductivity of the material constituting the diffusion layer 134 is preferably ^10-2 S / cm or more.

The separator 150b (separator for another electrolytic cell) is arranged on the side of the oxygen-evolving electrode catalyst layer 132 in the electrolytic cell 100. In the present embodiment, the separator 150b is laminated on the main surface of the oxygen evolution electrode 130 on the opposite side of the electrolyte membrane 110. The separator 150b can be made of the same material as the main body 154 of the separator 150a. The separator 150b has a conventionally known structure, and a single or a plurality of groove-shaped flow path portions 152b are provided on the surface on the diffusion layer 134 side.

Water supplied from the water storage tank 40 flows through the flow path portion 152b. A laminar flow of water is generated in the flow path portion 152b. Water permeates the diffusion layer 134 from the flow path portion 152b. The form of the flow path portion 152b is not particularly limited, but for example, a linear flow path, a serpentine flow path, or the like can be adopted. The flow path portion 152b can be formed by cutting, pressing, or the like on a flat plate made of carbon or metal. The flow path width of the flow path portion 152b is, for example, 1 mm, and the depth is, for example, 1 mm.

In the present embodiment, liquid water is supplied to the oxygen evolving electrode 130, but a humidified gas (for example, air or water vapor) may be supplied instead of the liquid water. In this case, the dew point temperature of the humidifying gas is preferably room temperature to 100 ° C, more preferably 50 to 100 ° C.

A current collector (not shown) is connected to the electrolytic cell 100. The current collector is made of a metal having good electron conductivity such as copper and aluminum.

<Method for producing hydrogenated product of aromatic hydrocarbon compound>
In the method for producing a hydrogenated product of an aromatic hydrocarbon compound according to the present embodiment, the aromatic hydrocarbon compound is supplied from the organic substance storage tank 30 to the reducing electrode catalyst layer 122 of the electrolytic cell 100 described above. Further, water is supplied from the water storage tank 40 to the oxygen evolution electrode catalyst layer 132. Then, the electrode reaction proceeds in each of the reducing electrode catalyst layer 122 and the oxygen evolution electrode catalyst layer 132.

The reaction in the electrolytic cell 100 when toluene is used as the unhydrogenated product of the aromatic hydrocarbon compound is as follows.
<Electrode reaction at oxygen evolution electrode>
3H ₂ O → 1.5O ₂ + 6H ⁺ + 6e ⁻ : E ₀ > 1.23V
<Electrode reaction at the reducing electrode>
Toluene ⁺ 6H ^{+ +} 6e ^- → _{methylcyclohexane:} E 0 <0.15V
That is, the electrode reaction at the oxygen evolution electrode 130 and the electrode reaction at the reducing electrode 120 proceed in parallel. Then, the protons generated by the electrolysis of water in the oxygen generating electrode 130 are supplied to the reducing electrode 120 via the electrolyte membrane 110. The protons supplied to the reducing electrode 120 are used for nuclear hydrogenation of the aromatic hydrocarbon compound in the reducing electrode 120. As a result, toluene is hydrogenated to produce methylcyclohexane, which is a hydrogenated form of an aromatic hydrocarbon compound. Therefore, according to the production method according to the present embodiment, the electrolysis of water and the hydrogenation reaction of the aromatic hydrocarbon compound can be carried out in one step.

The aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer 122 has, for example, 100% of an unhydrogenated compound at the start. When the circulation between the organic substance storage tank 30 and the electrolytic cell 100 is repeated, the proportion of the unhydrogenated substance in the aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer 122 gradually decreases, and the hydrogenated product becomes The proportion gradually increases. Even in a configuration in which a plurality of electrolytic cells 100 are connected in series and aromatic hydrocarbon compounds are sequentially supplied to each electrolytic cell 100, the proportion of unhydrogenated material gradually increases each time the electrolytic cells 100 are passed. It decreases and the proportion of hydrocarbons gradually increases.

In the present embodiment, the aromatic hydrocarbon compound is preferably an unhydrogenated product of 10% or less and a hydrogenated product of 90% or more, more preferably an unhydrogenated product of 5% or less and a hydrogenated product of 95% or more. It includes a step of supplying the reducing electrode catalyst layer 122 in proportion. That is, the mixture of the hydrogenated product and the non-hydrogenated product of the aromatic hydrocarbon compound preferably contains 10 mol% or less of the unhydrogenated product and 90 mol% or more of the hydrogenated product with respect to the entire mixture. Preferably, the unhydrogenated compound is supplied to the reducing electrode catalyst layer 122 from the organic substance storage tank 30 in a proportion of 5 mol% or less and 95 mol% or more of the hydrogenated compound with respect to the entire mixture.

FIG. 4 is a graph showing the relationship between the potential and the current density when the concentrations of the unhydrogenated compounds of the aromatic hydrocarbon compound are different. The graph shown in FIG. 4 shows the results when toluene (TL) is used as the unhydrogenated product of the aromatic hydrocarbon compound, and a separator having a conventional structure, that is, a separator having the same structure as the separator 150b is used on the reducing electrode side. Shown. As shown in FIG. 4, as the concentration of the unhydrogenated product in the aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer 122 decreases, the obtained current density tends to decrease. The increase in current density in the region on the left side of the broken line is not due to electrolytic reduction of toluene, but due to hydrogen production in the side reaction.

As a result of diligent studies, the present inventors have found that the diffusion of aromatic hydrocarbon compounds becomes the rate-determining factor and causes a decrease in current density. Then, he came up with a separator 150a having a porous layer 156. By providing the porous layer 156 on the separator 150a, it is possible to increase the diffusion efficiency of the aromatic hydrocarbon compound into the reducing electrode catalyst layer 122 as compared with the separator having the conventional structure. Therefore, the diffusion rate-determining described above can be eliminated. As a result, it is possible to supply the aromatic hydrocarbon compound at a ratio of 10% or less of the unhydrogenated material, further 5% or less. In other words, the proportion of unhydrogenated material can be reduced to 10% or less, and even to 5% or less.

As described above, the separator 150a according to the present embodiment includes the conductive porous body layer 156 through which the aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer 122 flows. By making the voids of the porous layer 156 a flow path 159 of the aromatic hydrocarbon compound, turbulence of the aromatic hydrocarbon compound can be generated. Then, the aromatic hydrocarbon compound can be uniformly distributed over the entire area of the porous layer 156 as compared with the separator having a conventional structure having a groove-shaped flow passage. Further, as compared with the separator having the conventional structure, the region where the main body portion is in direct contact with the diffusion layer (that is, the portion between the flow path groove and the flow path groove, which is called a rib) can be reduced.

As a result, the aromatic hydrocarbon compound can be uniformly supplied to the reducing electrode catalyst layer 122, and the area of the reducing electrode catalyst layer 122 that can be used for the electrode reaction can be increased. Therefore, the amount (current density) of the aromatic hydrocarbon compound that can be hydrogenated per electrode area and time can be improved. That is, the efficiency of hydrogenating the aromatic hydrocarbon compound can be improved.

Further, as the hydrogenation reaction of the aromatic hydrocarbon compound progresses, the proportion of the unhydrogenated material in the aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer 122 gradually decreases. When the proportion of the unhydrogenated compound decreases, the diffusion of the aromatic hydrocarbon compound becomes rate-determining, and the current density or the electrolytic reaction rate tends to decrease. On the other hand, from the viewpoint of transport efficiency of aromatic hydrocarbon compounds, there is a demand to reduce the proportion of unhydrogenated compounds as much as possible. On the other hand, by using the separator 150a provided with the porous layer 156 in the electrolytic cell 100, it is possible to suppress a decrease in the current density even when the unhydrogenated product of the aromatic hydrocarbon compound has a low concentration. be able to. Therefore, the performance of the electrolytic cell 100 can be improved. Further, by using such an electrolytic cell 100, a hydrogenated product of an aromatic hydrocarbon compound can be produced with high efficiency.

(Embodiment 2)
The electrochemical reduction apparatus 10 according to the second embodiment has the same configuration as that of the first embodiment except that the pressure difference between the front and rear of the porous layer of the aromatic hydrocarbon compound is controlled. Hereinafter, the electrochemical reduction apparatus according to the present embodiment will be mainly described with a configuration different from that of the first embodiment, and the common configuration will be briefly described or omitted. FIG. 5 is a schematic view showing a schematic configuration of the electrochemical reduction device according to the second embodiment.

In the electrochemical reduction device 10 according to the present embodiment, the electrolytic cell 100 and the reducing electrode catalyst layer 122 (see FIG. 2) included in the electrolytic cell 100 are aromatic with the separator 150a for the electrolytic cell (see FIG. 2). It is provided with a supply unit for supplying a group hydrocarbon compound. The supply unit is in a liquid state so that the difference between the pressure of the aromatic hydrocarbon compound supplied to the porous layer 156 of the separator 150a and the pressure of the aromatic hydrocarbon compound flowing out from the porous layer 156 is more than 9 kPa. Aromatic hydrocarbon compounds are supplied.

The pressure of the aromatic hydrocarbon compound supplied to the porous layer 156 is detected by the pressure gauge 115. Further, the pressure of the aromatic hydrocarbon compound flowing out from the porous layer 156 is detected by the pressure gauge 116. More specifically, the electrochemical reduction apparatus 10 has a pressure gauge 115 in the vicinity of a supply port 160 (see FIG. 3) for the aromatic hydrocarbon compound to flow into the porous layer 156. Further, a pressure gauge 116 is provided in the vicinity of the discharge port 162 (see FIG. 3) for the aromatic hydrocarbon compound to flow out from the porous layer 156. As the pressure gauges 115 and 116, conventionally known pressure gauges such as a diaphragm type, a Bourdon tube type, and a bellows type can be used. For example, immediately before the supply port 160, the pipe of the aromatic hydrocarbon compound is branched into a T shape, and the pressure gauge 115 is connected to the branched end. Immediately after the discharge port 162, the pipe of the aromatic hydrocarbon compound is branched into a T shape, and the pressure gauge 116 is connected to the branched end.

In the present embodiment, the supply unit includes a first liquid supply device 32 and a control unit 60. The pressure values detected by the pressure gauges 115 and 116 are input to the control unit 60. The control unit 60 calculates the difference between the pressure at the supply port 160 and the pressure at the discharge port 162 from the input pressure value. Then, the control unit 60 transmits a drive signal to the first liquid supply device 32 so that the pressure difference exceeds 9 kPa. For example, the control unit 60 is provided in advance with a conversion table in which the pressure difference and the supply flow rate of the aromatic hydrocarbon compound are associated with each other, and determines a desired supply flow rate according to this conversion table. Then, a drive signal is transmitted to the first liquid supply device 32 so that the supply flow rate is determined. The first liquid supply device 32 is driven based on the drive signal of the control unit 60. As a result, the pressure difference before and after the porous layer 156 is adjusted to more than 9 kPa.

Alternatively, the supply unit is fixed in advance so that the pressure difference between the front and rear of the porous layer 156 becomes more than 9 kPa according to the structure (volumetric porosity, etc.) of the flow path 159 of the porous layer 156. The aromatic hydrocarbon compound is supplied at the supply flow rate. The control unit 60 transmits an ON / OFF signal of the first liquid supply device 32. The first liquid supply device 32 is driven / stopped based on the ON / OFF signal. The ON / OFF signal may be transmitted to the first liquid supply device 32 from an operation panel (not shown) provided in the electrochemical reduction device 10 by an operator's operation. In this case, the supply unit may be composed of only the first liquid supply device 32. When the supply flow rate predetermined according to the porous layer 156 to be used is accompanied by an excessive load on the first liquid supply device 32, piping, etc., or an excessive increase in the driving power of the first liquid supply device 32. Is replaced with, for example, a separator 150a having a porous layer 156 capable of producing a larger pressure loss, thereby achieving a pressure difference of more than 9 kPa.

By adjusting the pressure difference before and after the porous layer 156 to more than 9 kPa, the generation of turbulent flow F in the flow path 159 can be promoted. This makes it possible to increase the diffusion limit current density, which is the upper limit of the current density until hydrogen generation occurs in the side reaction. Therefore, the performance of the electrochemical reduction device 10 can be improved. The pressure difference is more preferably 10 kPa or more, still more preferably 14 kPa or more.

The difference between the pressure at the supply port 160 and the pressure at the discharge port 162 of the aromatic hydrocarbon compound is preferably 1 MPa or less, more preferably 500 kPa or less, and further preferably 300 kPa or less. By setting the upper limit of the pressure difference to 1 MPa or less, it is possible to suppress an excessive amount of electric power consumed by the first liquid supply device 32 and suppress a decrease in energy efficiency in the electrochemical reduction device 10. Further, it is possible to reduce the possibility that the flow path 159 is blocked due to the decrease in the volume vacancy ratio of the porous layer 156, and to suppress the deterioration of the performance of the electrochemical reduction device 10. Further, by setting the upper limit of the pressure difference to 300 kPa or less, the electrochemical reduction device 10 can be configured by using a general sealing material, cell material or pump. Therefore, an inexpensive and long-life electrochemical reduction device 10 can be easily manufactured.

The viscosity (viscosity) of the supplied liquid aromatic hydrocarbon compound is preferably 0.2 to 10 mPa · s, more preferably 0.3 to 5 mPa · s at 20 ° C., and further preferably 0.3 to 5 mPa · s. Is 0.4 to 3 mPa · s. The viscosities of typical alkylbenzenes toluene, ethylbenzene, and o-xylene at 20 ° C. are 0.59, 0.68, and 0.83 mPa · s, respectively. As other aromatic compounds, the viscosities of benzene, pyridine, and o-methoxytoluene at 20 ° C. are 0.65, 0.96, and 1.32 mPa · s, respectively. For these aromatic compounds listed, when they are circulated through the separator 150a provided with the porous layer 156, the pressure difference and the supply flow rate show a relatively good proportional relationship, and the effect of improving the current density can be obtained. The present inventors have confirmed that.

When the discharge port 162 side has a structure open to the atmosphere, the pressure detected by the pressure gauge 115 can be treated as a pressure difference as it is, so that the pressure gauge 116 can be omitted.

Further, the flow path 159 of the porous layer 156 of the present embodiment is a flow path 159, when a liquid aromatic hydrocarbon compound is circulated at a predetermined flow rate when performing an electrochemical reduction reaction, the aromatic hydrocarbon. It has a structure in which the difference between the pressure at the supply port 160 of the compound and the pressure at the discharge port 162 is more than 9 kPa. By incorporating the porous layer 156 having such a flow path 159 into the electrochemical reduction device 10, it is possible to easily adjust the pressure difference of the aromatic hydrocarbon compound before and after the porous layer 156 to more than 9 kPa. .. According to the flow path 159 composed of the voids of the porous layer 156, the supply flow rate of the aromatic hydrocarbon compound is avoided to be excessively increased as compared with the separator having a conventional structure having a groove-shaped flow path. The desired pressure difference can be obtained. Therefore, the turbulent flow F can be generated more reliably. Moreover, a larger turbulent flow F can be generated.

Further, in the method for producing a hydrogenated product of an aromatic hydrocarbon compound according to the present embodiment, the pressure of the aromatic hydrocarbon compound supplied to the porous layer 156 of the separator 150a and the aromatic flowing out from the porous layer 156 It includes supplying a liquid aromatic hydrocarbon compound so that the difference from the pressure of the hydrocarbon compound is more than 9 kPa. Thereby, the diffusion limit current density can be increased. Therefore, the efficiency of hydrogenating the aromatic hydrocarbon compound can be improved.

The present invention is not limited to each of the above-described embodiments, and each embodiment can be combined, and further modifications such as various design changes can be made based on the knowledge of those skilled in the art. , Examples of such combinations or further modifications are also included in the scope of the invention. The combination of the above-described embodiments and the new embodiment caused by the addition of the modification to each of the above-described embodiments have the combined effects of the combined embodiment and the modification.

(Modification example 1)
FIG. 6 is a cross-sectional view showing a schematic configuration of the electrolytic cell according to the first modification. The electrolytic cell 100A according to the first modification is different from the electrolytic cell 100 according to the first and second embodiments in that the diffusion layer 124 and the dense layer 126 are omitted and the porous layer 156 is in direct contact with the reducing electrode catalyst layer 122. different. The porous layer 156 can uniformly distribute the aromatic hydrocarbon compound over the entire area. Therefore, the porous layer 156 has the same functions as the diffusion layer 124 and the dense layer 126. Therefore, the diffusion layer 124 and the dense layer 126 can be omitted. As a result, the size of the electrolytic cell 100 can be reduced.

(Modification 2)
FIG. 7 is a plan view of the separator according to the modified example 2 as viewed from the reduction electrode 120 side. The separator 150c according to the second modification is different from the electrolytic cells 100 according to the first and second embodiments in that the porous layer 156 has a partition member 166 that defines the flow direction of the aromatic hydrocarbon compound. In this modification, the distribution direction is defined by the plate-shaped partition member 166 so that the aromatic hydrocarbon compound meanders from the supply port 160 to the discharge port 162. By providing the partition member 166, the flow velocity of the aromatic hydrocarbon compound in the porous layer 156 can be increased.

(Other)
In the first and second embodiments and the first and second modifications, the separator 150b having the conventional structure is provided on the oxygen evolution electrode 130 side, but the separator 150a of the present embodiment is also provided on the oxygen evolution electrode 130 side. May be done.

Examples of the present invention will be described below, but these examples are merely examples for preferably explaining the present invention, and do not limit the present invention in any way.

(Evaluation of current density)
(Example 1)
The ratio of PtRu / C (product number: TEC61E54, manufactured by Tanaka Kikinzoku Co., Ltd.), 20 wt% Nafion (registered trademark) DE2020CS (manufactured by DuPont), pure water, and 1-propanol (1-Propanol) is The mixture was mixed so as to have a mass ratio of 5:10:20:65. The obtained mixture was pulverized with a ball mill to obtain a catalyst composition for a reducing electrode catalyst layer. This catalyst composition was spray-coated on one main surface of an electrolyte membrane (trade name: Nafion (registered trademark) 212, manufactured by DuPont) to form a reducing electrode catalyst layer. The amount of the catalyst supported was 0.5 mg / cm ² .

In addition, the ratio of iridium oxide powder (manufactured by Wako Junyaku Co., Ltd.) ground in a mortar, 20 wt% Nafion (registered trademark) DE2020CS (manufactured by DuPont), pure water, and 1-PrOH is mass. The mixture was mixed so as to have a ratio of 7:14:18:61. The obtained mixture was pulverized with a ball mill to obtain a catalyst composition for an oxygen-evolving electrode catalyst layer. This catalyst composition was spray-applied to the other main surface of the electrolyte membrane to form an oxygen-evolving polar catalyst layer. The supported amount of the catalyst was 2.5 mg / cm ² .

Further, the catalyst composition for the reducing electrode catalyst layer is spray-coated on a GDL (gas diffusion layer) with MPL (microporous layer) (trade name: SIGRACET GDL 35BC, manufactured by SGL Carbon) to obtain a reference electrode. It was. The amount of the catalyst supported was 0.5 mg / cm ² .

A GDL (gas diffusion layer) with MPL (microporous layer) (trade name: SIGRACET GDL 35BC, manufactured by SGL Carbon Co., Ltd.) was laminated on the surfaces of the reducing electrode catalyst layer and the oxygen evolution electrode catalyst layer. The obtained laminate was hot-pressed at a temperature of 120 ° C. and a pressure of 1 MPa to obtain a membrane electrode assembly. The reference electrode was provided so as to be in contact with the surface of the electrolyte membrane on the reducing electrode side.

A separator having a porous layer was laminated on the main surface of the obtained membrane electrode assembly on the reducing electrode side. The separator with a porous layer was formed as follows. That is, a spherical metal powder was produced by the gas atomizing method. Then, the average particle size was adjusted to 200 μm by classification to obtain a metal powder used for the porous body layer. The material of the metal powder was 59Ni-16Cr-16Mo-5Fe-4W alloy (numerical value is mass%). The obtained metal powder was filled in the recess (depth 1 mm) of the separator so that the layer thickness of the porous body layer was 1 mm and the volume vacancy ratio of the porous body layer was 50%. Then, a vacuum sintering treatment was performed at 1200 ° C. to obtain a separator with a porous body layer. The material of the separator body was SUS316L.

Further, a separator having a conventional structure having a groove-shaped flow path (see separator 150b in FIG. 2) was laminated on the main surface of the membrane electrode assembly on the oxygen-evolving electrode side. As the separator with a grooved flow path, a separator made of titanium and provided with a serpentine flow path (depth 1 mm, flow path width 1 mm, rib width 1 mm) was used. An electrolytic cell was obtained by the above steps.

(Comparative Example 1)
An electrolytic cell was obtained in the same manner as in Example 1 except that a separator having a conventional structure was laminated on the main surface of the membrane electrode assembly on the reducing electrode side. The separator having a conventional structure has a groove-like flow path and does not have a pore structure like the separator of the embodiment. Here, the volume vacancy ratio was conveniently calculated from the volume ratios of the grooved flow path and the rib. As a result, the volume vacancy rate was 66%.

For the electrolytic cells of Example 1 and Comparative Example 1, a mixed solution of 5 mol% toluene and 95 mol% methylcyclohexane was circulated through each reducing electrode at a flow rate of 20 ccm. Further, a 0.5 mol / L sulfuric acid aqueous solution was circulated through each oxygen generating electrode at a flow rate of 20 ccm. Further, a water vapor saturated hydrogen gas was circulated through each reference electrode at a flow rate of 20 ccm. Then, various voltages were applied to each electrolytic cell from the outside, and the current density flowing between the reducing electrode and the oxygen generating electrode and the potential of the reducing electrode with respect to the reference electrode were measured. The result is shown in FIG.

FIG. 8 is a graph showing the relationship between the potential and the current density in the electrolytic cells of Example 1 and Comparative Example 1. In FIG. 7, the solid line shows the result of Example 1, and the broken line shows the result of Comparative Example 1. As shown in FIG. 7, it was confirmed that the current density can be improved by using the separator with a porous body layer as compared with the case of using the separator with a grooved flow path. In particular, this example shows that the current density can be improved even if the supplied toluene has a low concentration.

(Evaluation of the relationship between diffusion limit current density and pressure difference)
(Example 2)
An electrolytic cell was obtained in the same manner as in Example 1 except that the average particle size of the spherical metal powder constituting the porous layer was 40 μm and the volume porosity was 24%.

(Example 3)
An electrolytic cell was obtained in the same manner as in Example 1 except that the average particle size of the spherical metal powder constituting the porous layer was 40 μm and the volume porosity was 30%.

(Example 4)
An electrolytic cell was obtained in the same manner as in Example 1 except that the average particle size of the spherical metal powder constituting the porous layer was 40 μm and the volume vacancy ratio was 39%.

(Example 5)
An electrolytic cell was obtained in the same manner as in Example 1 except that the average particle size of the spherical metal powder constituting the porous layer was 40 μm and the volume vacancy ratio was 19%.

(Example 6)
An electrolytic cell was obtained in the same manner as in Example 1 except that the average particle size of the spherical metal powder constituting the porous layer was 40 μm and the volume vacancy ratio was 14%.

(Example 7)
An electrolytic cell was obtained in the same manner as in Example 1 except that the volume vacancy ratio was 60%.

Piping for supplying and discharging the aromatic hydrocarbon compound was connected to the electrolytic cells of Examples 1 to 7 and Comparative Example 1. A pressure gauge was installed near the supply port of the porous layer in the piping. The outlet of the porous layer was opened to the atmosphere. Therefore, the cell inlet pressure measured by the pressure gauge is equal to the pressure difference between the supply port and the discharge port of the aromatic hydrocarbon compound. Subsequently, a 5 mol% toluene / 95 mol% methylcyclohexane mixed solution was circulated through the reducing electrodes of the electrolytic cells of each Example and Comparative Example at different flow rates. The flow rate was 0, 5, 10, 15, 20 mL / min. Then, the pressure difference at each flow rate was measured. The results are shown in FIG. 9 (A).

Further, in the case of a flow rate of 5, 20 mL / min, the current density was measured by applying various voltages from the outside to each electrolytic cell in the same manner as in the case of evaluating the current density described above. Then, from this result, the diffusion limit current density (mA / cm ² ) was derived. In this evaluation, the current density at the inflection point of the potential-current density curve was defined as the diffusion limit current density. The results are shown in FIG. 9 (A). In addition, a graph showing the relationship between the cell inlet pressure and the diffusion limit current density was created for a flow rate of 20 mL / min. The results are shown in FIG. 9 (B).

In addition, a graph showing the relationship between the supply flow rate of the aromatic hydrocarbon compound and the cell inlet pressure was created. The results are shown in FIG. Then, using this graph, the pressure rise rate per unit supply flow rate was calculated. The pressure increase rate is the slope of the regression line (linear regression) in the graph shown in FIG. The results are shown in FIG. 9 (A).

FIG. 9A is a diagram showing the volume vacancy rate, the pressure difference, the pressure rise rate, and the diffusion limit current density in each Example and Comparative Example. FIG. 9B is a graph showing the relationship between the cell inlet pressure and the diffusion limit current density at a compound flow rate of 20 mL / min in each Example and Comparative Example. FIG. 10 is a graph showing the relationship between the supply flow rate of the aromatic hydrocarbon compound and the cell inlet pressure.

As shown in FIGS. 9 (A) and 9 (B), in each of the examples, a higher diffusion limit current density was obtained as compared with Comparative Example 1. Further, as shown in FIG. 9B, the effect of improving the diffusion limit current density as compared with Comparative Example 1 in Examples 1 to 6 in which the pressure difference exceeds 9 kPa as compared with Example 7 in which the pressure difference is 9 kPa. Was larger. From this, it was confirmed that the diffusion limit current density can be further increased by adjusting the pressure difference before and after the porous layer to more than 9 kPa, more preferably 10 kPa or more, and further preferably 14 kPa or more. Further, as shown in FIG. 10, the supply flow rate of the aromatic hydrocarbon compound and the cell inlet pressure were in a proportional relationship. From this, it was confirmed that a desired pressure difference can be generated by adjusting the supply flow rate of the aromatic hydrocarbon compound.

100 Electrolyte cell, 110 Electrolyte membrane, 122 Reduction electrode catalyst layer, 132 Oxygen evolution electrode catalyst layer, 150a, 150b Separator, 152b Channel part, 156 Porous layer, 164 Metal powder, 166 Partition member.

Claims (9)

An electrolyte membrane having proton conductivity, provided on one side of the electrolyte membrane, a reducing electrode catalyst layer for hydrogenating an aromatic hydrocarbon compound, and provided on the side opposite to the one side of the electrolyte membrane. , An oxygen-evolving electrode catalyst layer for oxidizing water to generate protons, and a conductive porous layer arranged on the side of the reducing electrode catalyst layer and through which an aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer flows. An electrolytic cell having a separator for a reducing electrode side electrolytic cell having a body layer, and an electrolytic cell having an oxygen evolving electrode side electrolytic cell separator arranged on the side of the oxygen evolving electrode catalyst layer and having a flow path for water flow .
Before SL reduction electrode catalyst layer, and a supply unit for supplying the aromatic hydrocarbon compound with a separator for the reduction electrode side electrolysis cell,
The supply unit, as the difference between the pressure of the aromatic hydrocarbon compound pressure before Symbol the aromatic hydrocarbon compound is supplied to the porous body layer and the flowing out of the porous body layer is 9kPa than liquid An electrochemical reduction apparatus characterized by supplying an aromatic hydrocarbon compound in the form of a compound. The electrochemical reduction apparatus according to claim 1, wherein the thickness of the porous layer is 10 μm or more and 2000 μm or less. The electrochemical reduction apparatus according to claim 1 or 2 , wherein the volumetric porosity of the porous layer is 5% or more and 95% or less. The electrochemical reduction apparatus according to any one of claims 1 to 3 , wherein the average pore diameter of the porous layer is 1 μm or more and 1000 μm or less. The electrochemical reduction device according to any one of claims 1 to 4 , wherein the porous layer is composed of a sintered body of metal powder. The electrochemical reduction apparatus according to claim 5 , wherein the average particle size of the metal powder is 1 μm or more and 1000 μm or less. The electrochemical reduction apparatus according to any one of claims 1 to 6 , wherein the porous layer has a partition member that defines a flow direction of the aromatic hydrocarbon compound. The electrochemical reduction apparatus according to any one of claims 1 to 7, wherein the porous layer is in direct contact with the reducing electrode catalyst layer. An electrolyte membrane having proton conductivity, provided on one side of the electrolyte membrane, a reducing electrode catalyst layer for hydrogenating an aromatic hydrocarbon compound, and provided on the side opposite to the one side of the electrolyte membrane. , An oxygen-evolving electrode catalyst layer for oxidizing water to generate protons, a conductive porous layer arranged on the side of the reducing electrode catalyst layer and through which an aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer flows. The reducing electrode of an electrolytic cell having a separator for an electrolytic cell on the reducing electrode side having a body layer and a separator for an electrolytic cell on the reducing electrode side arranged on the side of the oxygen evolving electrode catalyst layer and having a flow path portion through which water flows. The unhydrogenated product of the aromatic hydrocarbon compound is hydrogenated by supplying the catalyst layer with an aromatic hydrocarbon compound at a ratio of 10% or less and 90% or more of the hydrogenated product .
Liquid aromatic hydrocarbons so that the difference between the pressure of the aromatic hydrocarbon compound supplied to the porous layer and the pressure of the aromatic hydrocarbon compound flowing out of the porous layer is more than 9 kPa. A method for producing a hydrogenated product of an aromatic hydrocarbon compound, which comprises supplying a compound.