JP2017179601A - Separator for electrolytic cells, electrolytic cell, electrochemical reduction device, and method for producing hydrogenated body of aromatic hydrocarbon compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique to improve the efficiency of hydrogenating an aromatic hydrocarbon compound.SOLUTION: A separator 150a is a separator for electrolytic cells to hydrogenate an aromatic hydrocarbon compound by an electrochemical reductive reaction. The separator has a conductive porous layer 156 in which an aromatic hydrocarbon compound supplied to a reduction electrode catalyst layer 122 of an electrolytic cell 100 circulates.SELECTED DRAWING: Figure 2

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 relates to a separator used in an electrolytic cell for electrochemically hydrogenating an aromatic hydrocarbon compound, an electrolytic cell having this electrolytic cell separator, an electrochemical reduction apparatus equipped with this electrolytic cell, and this electrolytic 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 obtained efficiently by hydrogenating the corresponding aromatic hydrocarbon compounds (benzene, naphthalene) using hydrogen gas. This reaction requires high temperature and high pressure reaction conditions. For this reason, it is unsuitable for manufacture on a small to medium scale. On the other hand, in an electrochemical reaction using an electrolytic cell, water can be used as a hydrogen source. For this reason, it is known that there is no need to handle gaseous hydrogen, and the reaction conditions are known to proceed at a relatively mild condition (normal temperature to about 200 ° C., normal pressure). For example, in Patent Documents 1 and 2, a membrane electrode in which a cathode catalyst layer that reduces an aromatic hydrocarbon compound such as toluene and an anode catalyst layer that oxidizes water are arranged so as to sandwich a proton conductive electrolyte membrane. An organic hydride manufacturing apparatus including a joined body is disclosed.

JP2012-072477A International Publication No. 11/122155 Pamphlet

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

  This invention is made | formed in view of such a condition, The objective is to provide the technique which improves the efficiency which hydrogenates an aromatic hydrocarbon compound.

  One embodiment of the present invention is an electrolytic cell separator. The electrolytic cell separator is an electrolytic cell separator that hydrogenates an aromatic hydrocarbon compound by an electrochemical reduction reaction, and the aromatic hydrocarbon compound supplied to the reduction electrode catalyst layer of the electrolytic cell circulates. A conductive porous layer is provided.

  Another aspect of the present invention is an electrolytic cell. The electrolytic cell includes an electrolyte membrane having proton conductivity, a reducing electrode catalyst layer for hydrogenating an aromatic hydrocarbon compound provided on one side of the electrolyte membrane, and the one side of the electrolyte membrane. Provided on the opposite side, an oxygen generating electrode catalyst layer for oxidizing water to generate protons, the electrolytic cell separator of the above aspect disposed on the reducing electrode catalyst layer side, and the oxygen generating electrode catalyst layer side And another electrolytic cell separator having a flow path portion through which water flows.

  Yet another embodiment of the present invention is an electrochemical reduction device. The electrochemical reduction device includes the electrolytic cell of the above aspect, and a supply unit that supplies an aromatic hydrocarbon compound to the reduction electrode catalyst layer included in the electrolytic cell via an electrolytic cell separator. Liquid aromatic carbonization so that the difference between the pressure of the aromatic hydrocarbon compound supplied to the porous body layer of the electrolytic cell separator and the pressure of the aromatic hydrocarbon compound flowing out of the porous body layer exceeds 9 kPa. Supply hydrogen compound.

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

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

1 is a schematic diagram illustrating a schematic configuration of an electrochemical reduction device including an electrolytic cell according to Embodiment 1. FIG. 1 is a cross-sectional view showing a schematic configuration of an electrolytic cell according to 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 an electric potential and electric current density in the case of varying the density | concentration of the unhydrogenated body of an aromatic hydrocarbon compound. 4 is a schematic diagram showing a schematic configuration of an electrochemical reduction device according to Embodiment 2. FIG. 6 is a cross-sectional view showing a schematic configuration of an electrolytic cell according to Modification Example 1. FIG. It is a top view of the separator which concerns on the modification 2 seen from the reduction electrode side. It is a graph which shows the relationship between the electric potential in the electrolytic cell of Example 1 and Comparative Example 1, and current density. FIG. 9A is a diagram showing volume porosity, pressure difference, pressure increase rate, and 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 cell inlet pressure.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The embodiments do not limit the invention but are exemplifications, and all features and combinations described in the embodiments are not necessarily essential to the invention. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. In addition, the scale and shape of each part shown in each drawing are set for convenience in order to facilitate the explanation, and are not limitedly interpreted unless otherwise specified. In addition, terms such as “first” and “second” used in the specification or claims do not represent any order or importance, but are used to distinguish one configuration from another. It is.

(Embodiment 1)
FIG. 1 is a schematic diagram illustrating a schematic configuration of an electrochemical reduction apparatus including an electrolytic cell according to Embodiment 1. In addition, in FIG. 1, illustration of the separator with which an electrolysis cell is provided is abbreviate | omitted, and the structure of a 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 steam-water separation unit 50, and A control unit 60 is provided.

  The power control unit 20 is, for example, a DC / DC converter that converts the output voltage of the power source into a predetermined voltage. The positive output terminal of the power control unit 20 is connected to the oxygen generation electrode (positive electrode) 130 of the electrolysis cell 100. The negative output terminal of the power control unit 20 is connected to the reduction electrode (negative electrode) 120 of the electrolysis cell 100. As a result, a predetermined voltage is applied between the oxygen generation electrode 130 and the reduction electrode 120 of the electrolytic cell 100. The power control unit 20 may be provided with a reference electrode for the purpose of positive and negative potential detection. In this case, the reference electrode input terminal is connected to a reference electrode 112 provided on the electrolyte membrane 110. The electric potential in this application shall mean the 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 generation electrode 130 or the reduction electrode 120 becomes a desired potential. The control unit 60 is realized by an element or a circuit including a CPU and a memory of a computer as a hardware configuration, and is realized by a computer program or the like as a software configuration. This will be understood by those skilled in the art. In addition, although it does not specifically limit as a power source, Normal system | strain power may be used and the electric power derived from natural energy, such as sunlight and a wind force, can also be used preferably.

  In the organic substance storage tank 30, an aromatic hydrocarbon compound is stored. The aromatic hydrocarbon compound used in the present embodiment is a compound including 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 1 to 4 hydrogen atoms 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 and ethylbenzene. Examples of the dialkylbenzene include xylene and diethylbenzene. Moreover, mesitylene etc. are illustrated as a trialkylbenzene. Examples of the alkyl naphthalene include methyl naphthalene. Moreover, 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. In addition, 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 the aromatic hydrocarbon compound, the nitrogen-containing heterocyclic aromatic compound may be substituted with an alkyl group or another substituent.

  The aromatic hydrocarbon compound is preferably liquid at normal temperature. Moreover, what is necessary is just to be a liquid as a mixture, when using what mixed multiple types of the above-mentioned aromatic hydrocarbon compound. When the aromatic hydrocarbon compound is liquid at normal temperature, the aromatic hydrocarbon compound can be supplied to the electrolytic cell 100 in a liquid state without performing treatment such as heating or pressurization. Thereby, the structure of the electrochemical reduction apparatus 10 can be simplified.

  The aromatic hydrocarbon compound stored in the organic substance storage tank 30 is supplied to the reduction 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-down device, or the like can be used. A circulation path is provided between the organic substance storage tank 30 and the reduction electrode 120. Note that the circulation path may not be provided. An aromatic hydrocarbon compound (hydrogenated aromatic hydrocarbon compound) and an unreacted aromatic hydrocarbon compound (unhydrogenated aromatic hydrocarbon compound) nuclear hydrogenated by the electrolytic cell 100 are: It is stored in the organic matter storage tank 30 through a circulation path. In the main reaction that proceeds at the reduction electrode 120, no gas is generated, but when a gas such as hydrogen is by-produced, a gas-liquid separation means may be provided in the middle of the circulation path.

  The water storage tank 40 stores, for example, ion exchange water, pure water, or an aqueous solution obtained by adding an acid such as sulfuric acid to these (hereinafter, simply referred to as “water” as appropriate). The water stored in the water storage tank 40 is supplied to the oxygen generation 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-down device, or the like can be used. A circulation path is provided between the water storage tank 40 and the oxygen generating electrode 130. Note that the circulation path may not be provided. Unreacted water in the electrolysis cell 100 is stored in the water storage tank 40 through a circulation path. A steam-water separator 50 is provided in the middle of the circulation path. A gas such as oxygen generated by electrolysis of water in the electrolysis cell 100 is separated from the water by the steam separator 50 and discharged out of the system.

  FIG. 2 is a cross-sectional view illustrating 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 includes an electrolyte membrane 110, a reduction electrode 120, and an oxygen generation electrode 130.

  The electrolyte membrane 110 is formed of a material (ionomer) having proton conductivity. The electrolyte membrane 110 selectively conducts protons, while suppressing the mixing and diffusion of substances between the reduction electrode 120 and the oxygen generation electrode 130. The thickness of the electrolyte membrane 110 is preferably 5 to 300 μm, more preferably 10 to 150 μm, and still more preferably 20 to 100 μm. By setting the thickness of the electrolyte membrane 110 to 5 μm or more, it is possible to ensure the barrier property of the electrolyte membrane 110 and more reliably suppress the occurrence of cross leaks such as aromatic hydrocarbon compounds and oxygen. Further, by setting the thickness of the electrolyte membrane 110 to 300 μm or less, it is possible to suppress the ion migration resistance from becoming excessive.

The area resistance of the electrolyte membrane 110, that is, the ion migration 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, the possibility of insufficient proton conductivity can be avoided more reliably. 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 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 ionomer to 0.7 meq / g or more, it is possible to more reliably avoid the possibility that the ion conductivity is insufficient. 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 the ionomer in water or an aromatic hydrocarbon compound increases and the strength of the electrolyte membrane 110 becomes insufficient. Can do.

  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 dimensional stability of the electrolyte membrane 110 accompanying an increase in ion exchange capacity. Thereby, the durability of the electrolyte membrane 110 can be improved. Moreover, the crossover of an aromatic hydrocarbon compound or oxygen can be suppressed.

  As shown in FIG. 1, a reference electrode 112 may be provided in contact with the electrolyte membrane 110 in a region separated from the reduction electrode 120 and the oxygen generating electrode 130 in the electrolyte membrane 110. The reference electrode 112 is electrically isolated from the reduction electrode 120 and the oxygen generation 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 = 0 V), an Ag / AgCl electrode (reference electrode potential = 0.199 V), 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 generation electrode 130 is detected by the current detection unit 113 shown in FIG. The current detection unit 113 is configured by, 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 control of the power control unit 20 by the control unit 60. The potential difference between the reference electrode 112 and the reduction electrode 120 is detected by the voltage detection unit 114. The voltage detection unit 114 is configured by, 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 controlling 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, reduction electrode 120 is provided in contact with one main surface of electrolyte membrane 110. The reduction electrode 120 has a structure in which a reduction electrode catalyst layer 122, a dense layer 126, and a diffusion layer 124 are laminated. The reducing electrode catalyst layer 122 is disposed near the electrolyte membrane 110, the diffusion layer 124 is disposed near the separator 150 a, and the dense layer 126 is disposed 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 includes a reduction catalyst for hydrogenating the aromatic hydrocarbon compound. The reduction catalyst used for the reduction electrode catalyst layer 122 includes, for example, at least one of Pt and Pd. The reduction catalyst includes a first catalytic metal (noble metal) made of at least one of Pt and Pd, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Sn, W, Re, Pb, You may be comprised with the metal composition containing the 1 type, or 2 or more types of 2nd catalyst metal selected from Bi. In this case, examples of the form of the metal composition include an alloy of the first catalyst metal and the second catalyst metal, or an intermetallic compound composed of the first catalyst metal and the second catalyst metal. 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%, and further preferably 25 to 80 wt%. It 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 (such as dissolution resistance). On the other hand, by setting the ratio of the first catalytic metal to 95 wt% or less, it is possible to more reliably suppress the electrode activity from becoming insufficient by avoiding that the properties of the reduction catalyst approach the properties of the noble metal alone. Can do. 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 made 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 still more preferably. Is 1.0 × 10 ⁻¹ S / cm or more. By setting the electron conductivity of the electron conductive material to 1.0 × 10 ⁻² S / cm or more, electron conductivity can be more reliably imparted to the reducing electrode catalyst layer 122.

Examples of the catalyst carrier include electron conductive materials containing as a main component any one of porous carbon (such as mesoporous carbon), porous metal, and porous metal oxide. Examples of the porous carbon include carbon black 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 carry the catalyst metal uniformly, thereby ensuring the diffusibility of the aromatic hydrocarbon compound more reliably. . 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 during the reaction of the aromatic hydrocarbon compound or when the electrochemical reduction device 10 is started or stopped. You can avoid that. Thereby, sufficient durability can be imparted to the catalyst carrier.

Examples of the porous metal include Pt black, Pd black, and Pt metal deposited in a fractal shape. Examples of the porous metal oxide include Ti, Zr, Nb, Mo, Hf, Ta, and W oxides. The catalyst carrier includes porous metal compounds such as nitrides, carbides, oxynitrides, carbonitrides, partially oxidized carbonitrides of metals such as Ti, Zr, Nb, Mo, Hf, Ta, and W. (Hereinafter referred to as porous metal carbonitride as appropriate) can also be used. The BET specific surface areas of the porous metal, porous metal oxide and porous metal carbonitride measured by the nitrogen adsorption method are 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 and the like to 1 m ² / g or more, the catalyst metal can be easily supported 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 the ionomer 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 further preferably 1.2 to 2 meq / g. When the catalyst support is porous carbon, the mass ratio I / C of ionomer (I) / catalyst support (C) is preferably 0.1 to 2, more preferably 0.2 to 1.5. More preferably, it is 0.3 to 1.1. By setting the mass ratio I / C to be 0.1 or more, sufficient ion 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 an excessive coating thickness of the ionomer on the catalytic metal and to inhibit the aromatic hydrocarbon compound as a reactant from contacting the catalytic active point. Can be avoided.

  In addition, it is preferable that the ionomer contained in the reducing electrode catalyst layer 122 partially coats the catalyst metal. According to this, 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 proton transfer resistance increases, and the diffusibility of the aromatic hydrocarbon compound tends to decrease. For this reason, it is desirable to adjust the thickness of the reducing electrode catalyst layer 122 within the above-described range.

The diffusion layer 124 has a function of uniformly diffusing a liquid aromatic hydrocarbon compound supplied from a separator 150 a described later into the reducing electrode catalyst layer 122. It is preferable that the material constituting the diffusion layer 124 has a high affinity for the aromatic hydrocarbon compound. As a 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 electronic conductivity of the material constituting the diffusion layer 124 is preferably 10 ⁻² S / cm or more.

  The dense layer 126 (MPL: micro porous layer) has a function of promoting the diffusion of the liquid aromatic hydrocarbon compound and the hydrogenated aromatic hydrocarbon compound in the surface direction of the reducing electrode catalyst layer 122. The dense layer 126 is formed, for example, by applying a paste-like kneaded material 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, a fluorine-based resin such as tetrafluoroethylene resin (PTFE) can be used. The ratio between the conductive powder and the water repellent is appropriately determined within a range where desired conductivity and water repellency can be obtained. As an example, the mass ratio (Vulcan: PTFE) when Vulcan (registered trademark) is used as the conductive powder and PTFE is used as the water repellent 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. In the case where the dense layer 126 is formed so as to drop inward from the surface of the diffusion layer 124, the average thickness of the dense layer 126 itself including the portion hidden in the diffusion layer 124 is determined as the dense layer. A thickness of 126 is defined.

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

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

  The porous body layer 156 is disposed 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. An aromatic hydrocarbon compound channel 159 is formed by the pores of the porous layer 156. The liquid aromatic hydrocarbon compound supplied from the organic substance storage tank 30 soaks into the diffusion layer 124 from the porous body layer 156. That is, the separator 150a has a flow path 159 stretched in a net shape on the main surface facing the reduction electrode 120 side. A turbulent flow F of the aromatic hydrocarbon compound is generated in the flow path 159. Thereby, the aromatic hydrocarbon compound can be more uniformly supplied to the entire area of the porous layer 156. For this reason, the aromatic hydrocarbon compound can be supplied uniformly by the reducing electrode catalyst layer 122.

  The porous body layer 156 is made of a sintered body of metal powder 164, for example. As a material of the metal powder 164, various materials can be selected according to 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 austenitic stainless steel, Ni-based corrosion resistant superalloy (INCONEL (registered trademark), Hastelloy (registered trademark), etc.), Ni-Cu based corrosion resistant alloy (MONEL). (Registered trademark, etc.), oxidation resistant alloys (high chromium alloys, etc.) and the like.

  The average particle diameter 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 diameter 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 the connected holes formed by the space surrounded by the plurality of metal powders. Thereby, the outstanding mass transfer of the aromatic hydrocarbon compound which flows through a void | hole part can be ensured, and an aromatic hydrocarbon compound can be distribute | circulated uniformly. Moreover, the contact point of metal powders can fully be ensured by the average particle diameter of the metal powder 164 being 1000 micrometers or less. Thereby, since the sintering strength of the porous body layer 156 is maintained, the collapse or defect of the porous body layer 156 can be suppressed. Moreover, an aromatic hydrocarbon compound can be distribute | circulated uniformly.

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

  As a method for sintering the metal powder 164, vacuum sintering, sintering in a reducing atmosphere such as hydrogen, sintering in an inert gas such as argon or nitrogen, atmospheric sintering, or the like can be employed. . If necessary, press processing, cutting processing, polishing processing, hydrophobic processing, or the like during or after sintering may be performed.

  The layer thickness of the porous body 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 body layer 156 can be measured by cross-sectional observation using a scanning electron microscope. By setting the thickness of the porous body layer 156 to 10 μm or more, the flow path 159 of the aromatic hydrocarbon compound can be more reliably formed. Further, the strength of the porous body layer 156 can be ensured. Moreover, the fall of the diffusibility of an aromatic hydrocarbon compound can be suppressed because the thickness of the porous body layer 156 shall be 2000 micrometers or less. In addition, the thickness of the separator 150a is 1 mm or more and 50 mm or less, for example. The depth of the recess 158 is preferably smaller than the layer thickness of the porous body layer 156. Thereby, the porous body layer 156 can be adhered to the diffusion layer 124 (in the case of Modification 1 described later, to 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 volume porosity of the porous body layer 156 is preferably 5% or more and 95% or less. The “volume porosity” is the ratio of the volume of pores to the entire volume of the porous layer 156. The volume porosity can be obtained by calculation from a cross-sectional image of the porous body layer 156 obtained using a scanning electron microscope. Alternatively, the volume porosity can be measured by a mercury intrusion method or the like. By setting the volume porosity of the porous body layer 156 to 5% or more, the flow path 159 of the aromatic hydrocarbon compound is more reliably formed, and the performance degradation of the electrolytic cell 100 due to the blockage of the flow path 159 is suppressed. Can do. Moreover, the intensity | strength of the porous body layer 156 is securable by setting the volume porosity of the porous body layer 156 to 95% or less. Moreover, the fall of the diffusibility of an aromatic hydrocarbon compound can be suppressed.

  The average pore diameter of the porous body layer 156 is preferably 1 μm or more and 1000 μm or less. The “average pore diameter” can be obtained by calculation from a cross-sectional image of the porous layer 156 obtained using a scanning electron microscope. Alternatively, the average pore diameter can be measured by image analysis using a focused ion beam scanning electron microscope. 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, the flow path 159 of the aromatic hydrocarbon compound can be more reliably formed, and the performance degradation of the electrolytic cell 100 due to the blockage of the flow path 159 can be suppressed. it can. Moreover, the intensity | strength of the porous body layer 156 is securable by the average pore diameter of the porous body layer 156 being 1000 micrometers or less.

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

  The oxygen generation electrode catalyst layer 132 contains one or more metals or metal oxides selected from Ru, Rh, Pd, Ir, and Pt as a catalyst. These catalysts may be dispersedly supported or coated on a metal substrate having electron conductivity. Such a metal substrate 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), mesh (mesh diameter: for example, 500 to 1000 μm), a sintered body of a metal porous body, a foamed molded body (foam), an expanded metal, and the like. The thickness of the oxygen generating 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 water supplied from a separator 150b described later into the oxygen generating electrode catalyst layer 132. The material forming the diffusion layer 134 preferably has a high affinity for water. As a material constituting the diffusion layer 134, for example, carbon paper, carbon woven fabric, or nonwoven 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. Moreover, the electron conductivity of the material which comprises the diffused layer 134 becomes like this. Preferably it is 10 ^<-2 > S / cm or more.

  The separator 150 b (another electrolytic cell separator) is disposed on the oxygen generating electrode catalyst layer 132 side in the electrolytic cell 100. In the present embodiment, the separator 150 b is laminated on the main surface of the oxygen generating electrode 130 on the side opposite to 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 one or a plurality of groove-shaped flow path portions 152b are provided on the surface on the diffusion layer 134 side.

  The 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 soaks into the diffusion layer 134 from the flow path portion 152b. Although the form of the flow path part 152b is not particularly limited, 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 or pressing a carbon or metal flat plate. The channel width of the channel part 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 generation electrode 130, but humidified gas (for example, air or water vapor) may be supplied instead of liquid water. In this case, the dew point temperature of the humidified gas is preferably room temperature to 100 ° C, more preferably 50 to 100 ° C.

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

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

The reaction in the electrolytic cell 100 when toluene is used as the unhydrogenated aromatic hydrocarbon compound is as follows.
<Electrode reaction at the electrode for oxygen generation>
3H ₂ O → 1.5 O ₂ + 6H ⁺ + 6e ⁻ : E ₀ > 1.23V
<Electrode reaction at the reduction electrode>
Toluene + 6H ⁺ + 6e ⁻ → methylcyclohexane: E ₀ <0.15V
That is, the electrode reaction at the oxygen generating electrode 130 and the electrode reaction at the reduction electrode 120 proceed in parallel. Then, protons generated by electrolysis of water in the oxygen generation electrode 130 are supplied to the reduction electrode 120 through the electrolyte membrane 110. The proton supplied to the reduction electrode 120 is used for the nuclear hydrogenation of the aromatic hydrocarbon compound at the reduction electrode 120. Thereby, toluene is hydrogenated and the methylcyclohexane which is a hydrogenated body of an aromatic hydrocarbon compound is produced | generated. Therefore, according to the manufacturing method according to the present embodiment, water electrolysis and aromatic hydrocarbon compound hydrogenation reaction can be performed in one step.

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

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

  FIG. 4 is a graph showing the relationship between potential and current density when the concentration of the unhydrogenated aromatic hydrocarbon compound is varied. The graph shown in FIG. 4 shows the results when toluene (TL) is used as an unhydrogenated aromatic hydrocarbon compound and a separator having the same structure as that of the separator 150b is used on the reduction electrode side. Show. As shown in FIG. 4, the current density obtained tends to decrease as the concentration of the unhydrogenated compound in the aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer 122 decreases. Note that 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 generation in a side reaction.

  As a result of intensive studies, the present inventors have found that the diffusion of the aromatic hydrocarbon compound is rate-limiting and causes a decrease in current density. Then, the inventors arrived at a separator 150a including a porous body layer 156. By providing the porous body layer 156 in the separator 150a, the diffusion efficiency of the aromatic hydrocarbon compound into the reducing electrode catalyst layer 122 can be increased as compared with the separator having the conventional structure. Therefore, the above-described diffusion rate control can be eliminated. As a result, the supply of the aromatic hydrocarbon compound at a rate of 10% or less, further 5% or less of the unhydrogenated product can be realized. In other words, the proportion of unhydrogenated product can be lowered to 10% or less, and further to 5% or less.

  As described above, the separator 150a according to the present embodiment includes the conductive porous body layer 156 in which the aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer 122 flows. By setting the voids of the porous layer 156 as the aromatic hydrocarbon compound flow path 159, a turbulent flow of the aromatic hydrocarbon compound can be generated. And compared with the separator of the conventional structure which has a groove-shaped flow path, an aromatic hydrocarbon compound can be distribute | circulated uniformly throughout the porous body layer 156. FIG. Further, as compared with a separator having a conventional structure, a region where the main body directly contacts the diffusion layer (that is, a portion between the channel groove and the channel 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 / time can be improved. That is, the efficiency of hydrogenating aromatic hydrocarbon compounds can be improved.

  Further, as the hydrogenation reaction of the aromatic hydrocarbon compound proceeds, the proportion of the unhydrogenated substance in the aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer 122 gradually decreases. When the proportion of the unhydrogenated product decreases, the diffusion of the aromatic hydrocarbon compound becomes rate-limiting 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 substances as much as possible. On the other hand, by using the separator 150a including the porous body layer 156 for the electrolytic cell 100, even when the unhydrogenated aromatic hydrocarbon compound has a low concentration, the decrease in current density is suppressed. be able to. Therefore, the performance of the electrolytic cell 100 can be improved. In addition, by using such an electrolytic cell 100, a hydrogenated 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 aromatic hydrocarbon compound before and after the porous body layer is controlled. Hereinafter, the electrochemical reduction apparatus according to the present embodiment will be described mainly with respect to the configuration different from that of the first embodiment, and the common configuration will be described briefly or the description will be omitted. FIG. 5 is a schematic diagram illustrating a schematic configuration of the electrochemical reduction device according to the second embodiment.

  The electrochemical reduction device 10 according to the present embodiment has an electrolysis cell 100 and a reduction electrode catalyst layer 122 (see FIG. 2) provided in the electrolysis cell 100 with an aroma through an electrolytic cell separator 150a (see FIG. 2). A supply section 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 body layer 156 of the separator 150a and the pressure of the aromatic hydrocarbon compound flowing out of the porous body layer 156 exceeds 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 body layer 156 is detected by the pressure gauge 116. More specifically, the electrochemical reduction device 10 includes a pressure gauge 115 in the vicinity of a supply port 160 (see FIG. 3) through which an aromatic hydrocarbon compound flows into the porous layer 156. In addition, a pressure gauge 116 is provided in the vicinity of the outlet 162 (see FIG. 3) through which the aromatic hydrocarbon compound flows out from the porous body 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 piping of the aromatic hydrocarbon compound is branched into a T shape, and the pressure gauge 115 is connected to the branched end. Moreover, immediately after the discharge port 162, the piping 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 the first liquid supply device 32 and the control unit 60. Pressure values detected by the pressure gauges 115 and 116 are input to the control unit 60. The controller 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. And the control part 60 transmits a drive signal to the 1st liquid supply apparatus 32 so that a pressure difference may be over 9 kPa. For example, the control unit 60 includes a conversion table that associates the pressure difference with the supply flow rate of the aromatic hydrocarbon compound in advance, and determines a desired supply flow rate according to the conversion table. And a drive signal is transmitted with respect to the 1st liquid supply apparatus 32 so that it may become the determined supply flow volume. The first liquid supply device 32 is driven based on a drive signal from the control unit 60. Thereby, the pressure difference before and behind the porous body layer 156 is adjusted to more than 9 kPa.

  Alternatively, the supply unit is fixed in advance so that the pressure difference before and after the porous layer 156 exceeds 9 kPa according to the structure (volume porosity, etc.) of the flow path 159 included in the porous layer 156. Aromatic hydrocarbon compounds are supplied at a supply flow rate. The control unit 60 transmits an ON / OFF signal for 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 the operator's operation. In this case, the supply unit may be configured by only the first liquid supply device 32. When the supply flow rate determined in advance according to the porous layer 156 to be used is accompanied by an excessive load on the first liquid supply device 32, piping, or the like, or an excessive increase in driving power of the first liquid supply device 32 For example, by replacing with a separator 150a having a porous layer 156 capable of producing a larger pressure loss, a pressure difference of more than 9 kPa is realized.

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

  Moreover, the difference between the pressure at the supply port 160 of the aromatic hydrocarbon compound and the pressure at the discharge port 162 is preferably 1 MPa or less, more preferably 500 kPa or less, and even more preferably 300 kPa or less. By setting the upper limit of the pressure difference to 1 MPa or less, it is possible to suppress the power consumed by the first liquid supply device 32 from being excessive, and to suppress a decrease in energy efficiency in the electrochemical reduction device 10. Moreover, the possibility that the flow path 159 is blocked due to a decrease in the volume porosity of the porous body layer 156 can be reduced, and a decrease in performance of the electrochemical reduction device 10 can be suppressed. Moreover, the electrochemical reduction apparatus 10 can be comprised using a general sealing material, cell material, and a pump because the upper limit of a pressure difference shall be 300 kPa or less. Therefore, it is possible to easily manufacture the electrochemical reduction device 10 which is inexpensive and has a long life.

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

  In the case where the discharge port 162 side is open to the atmosphere, the pressure detected by the pressure gauge 115 can be handled as a pressure difference as it is, so that the pressure gauge 116 can be omitted.

  In addition, the flow path 159 included in the porous layer 156 of the present embodiment allows the aromatic hydrocarbon compound to flow when the liquid aromatic hydrocarbon compound is circulated at a predetermined flow rate when the electrochemical reduction reaction is performed. It has a structure in which the difference between the pressure at the compound supply port 160 and the pressure at the discharge port 162 exceeds 9 kPa. By incorporating the porous layer 156 having such a flow path 159 into the electrochemical reduction device 10, the pressure difference of the aromatic hydrocarbon compound before and after the porous layer 156 can be easily adjusted to exceed 9 kPa. . According to the flow path 159 constituted by the voids of the porous body layer 156, while avoiding an excessive increase in the supply flow rate of the aromatic hydrocarbon compound, compared to a separator having a conventional structure having a groove-like flow passage. A desired pressure difference can be obtained. Therefore, the turbulent flow F can be generated more reliably. Further, a larger turbulent flow F can be generated.

  Further, in the method for producing a hydrogenated 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 of the porous layer 156 It includes supplying a liquid aromatic hydrocarbon compound so that the difference from the pressure of the hydrocarbon compound exceeds 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 the above-described embodiments, and the embodiments can be combined or further modified such as various design changes based on the knowledge of those skilled in the art. Embodiments that are combined or further modified are also included in the scope of the present invention. A combination of the above-described embodiments and a new embodiment generated by adding a modification to each of the above-described embodiments have the effects of the combined embodiment and the modification.

(Modification 1)
FIG. 6 is a cross-sectional view illustrating a schematic configuration of an electrolysis cell according to the first modification. The electrolytic cell 100A according to Modification 1 is different from the electrolytic cell 100 according to Embodiments 1 and 2 in that the diffusion layer 124 and the dense layer 126 are omitted, and the porous body layer 156 is in direct contact with the reducing electrode catalyst layer 122. Different. The porous body layer 156 can distribute the aromatic hydrocarbon compound uniformly throughout the entire area. Accordingly, the porous body layer 156 has the same function as the diffusion layer 124 and the dense layer 126. For this reason, the diffusion layer 124 and the dense layer 126 can be omitted. As a result, the electrolytic cell 100 can be downsized.

(Modification 2)
FIG. 7 is a plan view of a separator according to Modification 2 as viewed from the reduction electrode 120 side. Separator 150c according to Modification 2 differs from electrolysis cell 100 according to Embodiments 1 and 2 in that porous body layer 156 includes partition member 166 that defines the flow direction of the aromatic hydrocarbon compound. In this modification, the flow direction is defined by the plate-shaped partition member 166 so that the aromatic hydrocarbon compound meanders from the supply port 160 toward the discharge port 162. By providing the partition member 166, the flow rate of the aromatic hydrocarbon compound in the porous body layer 156 can be increased.

(Other)
In Embodiments 1 and 2 and Modifications 1 and 2, the separator 150b having the conventional structure is provided on the oxygen generation electrode 130 side, but the separator 150a of the present embodiment is also provided on the oxygen generation electrode 130 side. May be.

  Examples of the present invention will be described below. However, these examples are merely examples for suitably explaining the present invention, and do not limit the present invention.

(Evaluation of current density)
Example 1
PtRu / C (product number: TEC61E54, manufactured by Tanaka Kikinzoku Co., Ltd.), 20 wt% Nafion (registered trademark) DE2020CS (manufactured by Du Pont), pure water, and 1-propanol (1-PrOH) Mixing was performed at 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 applied to one main surface of an electrolyte membrane (trade name: Nafion (registered trademark) 212, manufactured by Du Pont) by spraying to form a reducing electrode catalyst layer. The supported amount of catalyst was 0.5 mg / cm ² .

In addition, iridium oxide powder (manufactured by Wako Pure Chemical Industries, Ltd.) ground with a mortar, 20 wt% Nafion (registered trademark) DE2020CS (manufactured by Du Pont), pure water, and 1-PrOH are each in a mass ratio. The mixture was mixed at a ratio of 7: 14: 18: 61. The obtained mixture was pulverized with a ball mill to obtain a catalyst composition for an oxygen-generating electrode catalyst layer. This catalyst composition was sprayed onto the other main surface of the electrolyte membrane to form an oxygen-generating electrode catalyst layer. The amount of catalyst supported was 2.5 mg / cm ² .

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

  GDL (gas diffusion layer) with MPL (microporous layer) (trade name: SIGRACET GDL 35BC, manufactured by SGL Carbon Co., Ltd.) was laminated on the respective surfaces of the reduction electrode catalyst layer and the oxygen generation 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 in contact with the surface of the electrolyte membrane on the reduction electrode side.

  A separator provided with a porous body layer was laminated on the main surface on the reduction electrode side of the obtained membrane electrode assembly. The separator with a porous layer was formed as follows. That is, spherical metal powder was produced by a gas atomizing method. And it adjusted to the average particle diameter of 200 micrometers by classification, and obtained the metal powder used for a porous body layer. The material of the metal powder was a 59Ni-16Cr-16Mo-5Fe-4W alloy (numerical value is mass%). The obtained metal powder was filled in the recesses (depth 1 mm) of the separator so that the layer thickness of the porous layer was 1 mm and the volume porosity of the porous layer was 50%. And the vacuum sintering process at 1200 degreeC was performed and the separator with a porous body layer was obtained. The material of the separator body was SUS316L.

  In addition, a separator having a conventional structure having a groove-like channel (see the separator 150b in FIG. 2) was laminated on the main surface of the membrane electrode assembly on the oxygen generating electrode side. The separator with a groove-like flow path was made of titanium and provided with a serpentine flow path (depth 1 mm, flow path width 1 mm, rib width 1 mm). Through the above steps, an electrolytic cell was obtained.

(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 reduction electrode side. In addition, the separator of the conventional structure is provided with a groove-shaped flow path, and does not have a pore structure like the separator of an Example. Here, the volume porosity was calculated for convenience from the respective volume ratios of the groove-like channel and the rib. As a result, the volume porosity was 66%.

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

  FIG. 8 is a graph showing the relationship between potential and current density in the electrolytic cells of Example 1 and Comparative Example 1. In FIG. 7, the solid line indicates the result of Example 1, and the broken line indicates 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 the porous body layer as compared with the case of using the separator with the groove-like channel. In particular, this example shows that the current density can be improved even when the supplied toluene is at a low concentration.

(Evaluation of 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 spherical metal powder constituting the porous layer had an average particle size of 40 μm and a volume porosity of 24%.

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

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

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

(Example 6)
An electrolytic cell was obtained in the same manner as in Example 1 except that the spherical metal powder constituting the porous body layer had an average particle diameter of 40 μm and a volume porosity of 14%.

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

  Pipes for supplying and discharging aromatic hydrocarbon compounds were 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 pipe. The outlet of the porous layer was open 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 allowed to flow through the reduction electrodes of the electrolysis cells of each Example and Comparative Example at different flow rates. The flow rate was 0, 5, 10, 15, 20 mL / min. And the pressure difference in each flow volume was measured. The results are shown in FIG.

Further, in the case of a flow rate of 5, 20 mL / min, as in the case of the above-described evaluation of current density, various voltages were applied to each electrolysis cell from the outside to measure the current density. 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. Further, 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.

  Moreover, the graph which shows the relationship between the supply flow rate of an aromatic hydrocarbon compound and cell inlet pressure was created. The results are shown in FIG. And the pressure increase rate per unit supply flow volume was computed using this graph. 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.

  FIG. 9A is a diagram showing volume porosity, pressure difference, pressure increase rate, and 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), a diffusion limit current density higher than that of Comparative Example 1 was obtained in any of the Examples. Further, as shown in FIG. 9B, compared with Example 7 in which the pressure difference is 9 kPa, Examples 1 to 6 in which the pressure difference is more than 9 kPa have an effect of improving the diffusion limit current density with respect to Comparative Example 1. Was bigger. 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 body layer to more than 9 kPa, more preferably 10 kPa or more, and even more preferably 14 kPa or more. Moreover, 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 could be generated by adjusting the supply flow rate of the aromatic hydrocarbon compound.

  DESCRIPTION OF SYMBOLS 100 Electrolytic cell, 110 Electrolyte membrane, 122 Reduction electrode catalyst layer, 132 Oxygen generation electrode catalyst layer, 150a, 150b Separator, 152b Channel part, 156 Porous body layer, 164 Metal powder, 166 Partition member

Claims (13)

A separator for an electrolytic cell for hydrogenating an aromatic hydrocarbon compound by an electrochemical reduction reaction,
A separator for an electrolytic cell comprising an electrically conductive porous layer through which an aromatic hydrocarbon compound supplied to the reducing electrode catalyst layer of the electrolytic cell flows. A supply port through which the aromatic hydrocarbon compound flows into the porous layer;
A discharge port through which the aromatic hydrocarbon compound flows out from the porous layer;
Further comprising
When the porous layer is made to flow the liquid aromatic hydrocarbon compound at a predetermined flow rate when the electrochemical reduction reaction is performed, the pressure at the supply port of the aromatic hydrocarbon compound and the The separator for electrolysis cells according to claim 1 which has a channel which a difference with the pressure in a discharge port exceeds 9kPa.   The separator for an electrolytic cell according to claim 1 or 2, wherein the layer thickness of the porous body layer is 10 µm or more and 2000 µm or less.   The separator for an electrolytic cell according to any one of claims 1 to 3, wherein the volume porosity of the porous body layer is 5% or more and 95% or less.   5. The electrolytic cell separator according to claim 1, wherein the porous body layer has an average pore diameter of 1 μm or more and 1000 μm or less.   The separator for an electrolytic cell according to any one of claims 1 to 5, wherein the porous body layer is composed of a sintered body of metal powder.   The separator for an electrolytic cell according to claim 6, wherein the average particle diameter of the metal powder is 1 μm or more and 1000 μm or less.   The separator for an electrolytic cell according to any one of claims 1 to 7, wherein the porous layer has a partition member that defines a flow direction of the aromatic hydrocarbon compound. 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;
An oxygen generating electrode catalyst layer provided on the side opposite to the one side of the electrolyte membrane for oxidizing protons to generate protons;
The electrolytic cell separator according to any one of claims 1 to 8, which is disposed on a side of the reducing electrode catalyst layer;
Other electrolytic cell separators disposed on the oxygen generating electrode catalyst layer side and having a flow path portion through which water flows,
An electrolysis cell comprising:   The electrolytic cell according to claim 9, wherein the porous body layer is in direct contact with the reducing electrode catalyst layer. Electrolytic cell according to claim 9 or 10,
A supply unit for supplying an aromatic hydrocarbon compound to the reduction electrode catalyst layer provided in the electrolytic cell via the electrolytic cell separator;
The supply unit has a difference between the pressure of the aromatic hydrocarbon compound supplied to the porous body layer of the electrolytic cell separator and the pressure of the aromatic hydrocarbon compound flowing out of the porous body layer of more than 9 kPa. Thus, an electrochemical reduction apparatus characterized by supplying a liquid aromatic hydrocarbon compound.   The aromatic hydrocarbon compound is supplied to the reduction electrode catalyst layer of the electrolysis cell according to claim 9 or 10 at a ratio of 10% or less of unhydrogenated product and 90% or more of hydride, to form the aromatic hydrocarbon. A method for producing a hydrogenated aromatic hydrocarbon compound comprising hydrogenating an unhydrogenated compound.   The liquid so that the difference between the pressure of the aromatic hydrocarbon compound supplied to the porous layer of the electrolytic cell separator and the pressure of the aromatic hydrocarbon compound flowing out of the porous layer exceeds 9 kPa. The method for producing a hydrogenated product of an aromatic hydrocarbon compound according to claim 12, comprising supplying an aromatic hydrocarbon compound in a form.