US20140144774A1

US20140144774A1 - Device for manufacturing organic hydride

Info

Publication number: US20140144774A1
Application number: US13/817,333
Authority: US
Inventors: Takayuki Hirashige; Takao Ishikawa
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2010-09-30
Filing date: 2011-08-18
Publication date: 2014-05-29
Also published as: JP2012072477A; CN103069051A; WO2012043086A1

Abstract

The device for electrochemically manufacturing an organic hydride of the present invention is characterized by the electrode structure thereof being a structure that forms a matrix in which a metal-catalyst supporting carbon or a metal catalyst is suitably intermingled with a proton-conductive solid polymer electrolyte as catalyst layers, and the catalyst layers are formed on the front and back of a proton-conductive solid polymer electrolyte membrane on which a layer that blocks water from passing through is formed. When water or water vapor is supplied to the anode side of this electrode and a substance to be hydrogenated is supplied to the cathode side, application of a voltage between the anode and the cathode causes an electrolysis reaction to the water to occur at the anode and a hydrogenation reaction to the substance to be hydrogenated to occur at the cathode, producing the organic hydride.

Description

TECHNICAL FIELD

The present invention relates to a device for electrochemically manufacturing an organic hydride.

BACKGROUND ART

Global warming by carbon dioxide and others has been becoming serious. Under this situation, attention is paid to hydrogen as an energy source for the next generation instead of fossil fuels. Hydrogen fuel does not impose a large burden on the environment since a substance discharged when the fuel is consumed is only water and no carbon dioxide is discharged. Unfortunately, hydrogen, which is a gas at a normal temperature and a normal pressure, has disadvantages about transporting, storing and supplying systems thereof.
In recent years, attention has been paid to organic hydride systems using hydrocarbons such as cyclohexane, methylcyclohexane and decalin as a hydrogen-storing method excellent in safety, transporting performance, and storing capacity. These hydrocarbons are liquid at a normal temperature and excellent in transportability. For example, toluene and methylcyclohexane are cyclic hydrocarbons having carbon atoms in the same number. However, toluene is an unsaturated hydrocarbon in which bonds between hydrocarbon atoms are double bonds while methylcyclohexane is a saturated hydrocarbon having no double bond. The hydrogenation reaction of toluene gives methylcyclohexane, while the dehydrogenation reaction of methylcyclohexane gives toluene. In other words, the use of the hydrogenation reaction and dehydrogenation reaction of these hydrocarbons enables storage and supply of hydrogen.
In order to manufacture an organic hydride such as methylcyclohexane, it is necessary to produce hydrogen and react the hydrogen with toluene on a catalyst. Specifically, the present process has two steps of generating hydrogen in, for example, a water electrolysis device, and then reacting the hydrogen with toluene in a hydrogenation reaction device to generate an organic hydride.
Thus, plural devices are necessary for producing the organic hydride, causing a problem that the system is complicated. Also, the hydrogen is in a gas form from the production of hydrogen to the hydrogenation reaction, causing problems about the storage and transportation thereof. When a hydrogen producing device and a hydrogenation device are built up to be adjacent to each other, these problems will be solved. However, another problem is caused about building and running costs, and total energy efficiency will be lowered. Furthermore, the devices are made large in size, so that a place where the devices are installed is restricted.
In recent year, techniques are disclosed which use a single device to manufacture an organic hydride at a single step (for example, in Patent Document 1). These techniques are for electrochemically manufacturing an organic hydride. For example, according to Patent Document 1, an organic hydride is manufactured by arranging metal catalysts onto both sides of a hydrogen-ion-permeable solid polymer electrolyte membrane, through which hydrogen ions are selectively permeated, supplying water or water vapor to one of the sides, supplying a substance to be hydrogenated to the other side, and using hydrogen ions generated by electrolysis of the water or water vapor on the anode side to cause hydrogenation reaction with the substance to be hydrogenated on the cathode side to manufacture an organic hydride.

DOCUMENTS ON PRIOR ARTS

Patent Documents

Patent Document 1: JP 2003-45449 A

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

Unfortunately, these methods for manufacturing an organic hydride have difficulty in giving high energy efficiencies. The reason thereof would be an effect of passed water. Specifically, it is considered that water used in the anode reaction passes through the hydrogen-ion-permeable solid polymer electrolyte membrane to reach the cathode, so that the passed water causes a bad effect onto the cathode reaction. Water and a substance to be hydrogenated, such as toluene, are insoluble into each other and not mixed with each other. Thus, when water is present in the cathode catalyst layer, the water hinders toluene from being supplied into the catalyst. As a result, hydrogen will be generated on the catalyst to which the substance to be hydrogenated, such as toluene, is not supplied. Thus, no hydrogenation reaction is caused to the substance to be hydrogenated and no organic hydride is generated, decreasing the energy efficiency. Moreover, when the passed water is mixed with the organic hydride after the hydrogenation reaction, another process for removing the water is required. This is undesired when the simplification of the system is considered.
An object of the present invention is to provide a small-scale and highly-efficient device for electrochemically manufacturing an organic hydride.

Means for Solving the Problem

In light of such a situation, the inventors have made eager researches to find out that highly-efficient electrodes can be obtained by forming a layer for blocking water from passing from the anode to the cathode on a surface of a solid polymer electrolyte membrane or inside the solid polymer electrolyte membrane. The electrodes in the present invention are characterized in that catalyst layers have a matrix structure in which metal-catalyst supporting carbon or a metal catalyst is suitably intermingled with a proton-conductive solid polymer electrolyte, and the catalyst layers are formed on the front and back of a proton-conductive solid polymer electrolyte membrane which includes a water-blocking layer.
The device for manufacturing an organic hydride of the present invention includes a membrane electrode assembly including a cathode catalyst layer that reduces a substance to be hydrogenated, an anode catalyst layer that oxidizes water, and a proton-conductive solid polymer electrolyte membrane disposed between the cathode catalyst layer and the anode catalyst layer, the membrane including a water-blocking layer from passing through, a member that supplies the substance to be hydrogenated to the cathode catalyst layer, and a member that supplies water or water vapor to the anode catalyst layer. The cathode catalyst layer includes a catalytic metal that reduces the substance to be hydrogenated to react into a hydride, a supporter supporting the catalytic metal, and a proton-conductive solid polymer electrolyte. The anode catalyst layer includes a catalytic metal that oxidizes water to react into protons, a supporter supporting the catalytic metal, and a proton-conductive solid polymer.

Advantageous Effects of the Invention

According to the present invention, a small-scale and highly-efficient device for electrochemically manufacturing an organic hydride can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a device for manufacturing an organic hydride or a fuel cell in accordance with an embodiment of the present invention;

FIG. 2 is a view illustrating a membrane electrode assembly in the present invention;

FIG. 3 is a view illustrating a membrane electrode assembly in a conventional technique;

FIG. 4 is a view showing an embodiment of the device for manufacturing an organic hydride of the present invention;

FIG. 5 is a view showing an embodiment of the device for manufacturing an organic hydride of the present invention;

FIG. 6 is a view showing an example of the device for manufacturing an organic hydride according to a conventional technique; and

FIG. 7 is a view showing an example of the device for manufacturing an organic hydride according to a conventional technique.

DESCRIPTION OF EMBODIMENTS

A device for electrochemically manufacturing an organic hydride of the present invention has an electrode structure that a catalyst layer, the layer having a matrix structure in which a proton-conductive solid polymer electrolyte and a metal-catalyst supporting carbon or metal catalyst are suitably intermingled with each other, is formed on the front and back of a proton-conductive solid polymer electrolyte membrane, the membrane including a water-blocking layer. In the electrodes, water or water vapor is supplied to the anode side, and a substance to be hydrogenated is supplied to the cathode. In this state, a voltage is applied to between the anode and the cathode to cause the electrolysis reaction of water in the anode and hydrogenation reaction of the substance to be hydrogenated in the cathode, thus manufacturing an organic hydride.
Embodiments of the present invention will be described in detail, referring to the drawings.
FIG. 1 illustrates a device for manufacturing an organic hydride in accordance with an embodiment of the present invention. The device for manufacturing an organic hydride of the present embodiment includes a membrane electrode assembly (MEA), a pair of gas diffusion layers 15 and a pair of separators 11 which are disposed to sandwich the membrane electrode assembly. The membrane electrode assembly (MEA) includes a solid polymer electrolyte membrane 12 having a water-blocking layer, an anode catalyst layer 13 on one surface of the sol id polymer electrolyte membrane 12, and a cathode catalyst layer 14 on the other surface of the membrane 12, the anode catalyst layer 13, the membrane 12 and the cathode catalyst layer 14 being joined and integrated. Each of the separators 11 includes a gas channel. A gasket 16 for gas seal is inserted into between the pair of separators 11.
Each of the separators 11 has electroconductivity, and the material thereof is desirably a dense graphite plate, a carbon plate obtained by shaping a carbon material such as graphite or carbon black by aid of a resin, or a metal material excellent in corrosion resistance, such as stainless steel or titanium. It is also desired to plate surfaces of the separators 11 with a noble metal, or apply a conductive paint excellent in corrosion resistance and heat resistance to the surfaces to subject the separators 11 to the surface-treatment. A groove which is a channel for a reactive gas or liquid is formed on each of the surfaces of the separators 11 that face the anode catalyst layer 13 and the cathode catalyst layer 14, respectively. Water or water vapor is supplied into the channel of the separator 11 at the anode side. The water or water vapor flowing through the channel is supplied to the anode catalyst layer through one of the gas diffusion layers 15. A substance to be hydrogenated is supplied to the separator 11 at the cathode side. The substance to be hydrogenated flowing through the other channel is supplied to the cathode catalyst through the other gas diffusion layer 15. The method for supplying the substance to be hydrogenated includes a method of supplying the substance to be hydrogenated which is a liquid substance as it is or supplying the substance to be hydrogenated which is a vapor-form substance using He gas or N₂gas as a carrier.
Each of the gas diffusion layers 15 is provided for supplying uniformly a reactive substance (gas or a liquid), which has been supplied to the channel of the separator 11, over the plane of the catalyst layer. A substrate having permeability to gases is used for the gas diffusion layers 15, such as carbon paper or carbon cloth. Particularly, a water-repellent substrate is preferable.
The gasket 16 has an electrically-insulating property, resistant particularly against hydrogen or the substance to be hydrogenated, and the organic hydride, and made of a material which passes through small amount of these components and has airtightness. Examples of such materials include butyl rubber, Viton rubber, and EPDM rubber.
When a voltage is applied to between the anode and the cathode in the state of supplying water or water vapor to the anode side and supplying toluene as the substance to be hydrogenated to the cathode side, electrolysis reaction of water is caused in the anode according to a formula (1) illustrated below. Protons generated by the electrolysis reaction according to the formula (1) moves through the solid polymer electrolyte membrane 12 to the cathode 14 to cause hydrogenation reaction according to a formula (2) illustrated below in the cathode. Thus, methylcyclohexane, which is an organic hydride, is manufactured.
H₂O→2H⁺+½O₂+2e ⁻ (1)
C₇H₈+6H⁺+6e ⁻→C₇H₁₄ (2)
In the device for manufacturing an organic hydride of the present embodiment, the water-blocking layer is formed on the solid polymer electrolyte membrane, so that the water in the anode does not pass to the cathode. Thus, the organic hydride can be manufactured with a high efficiency.
FIG. 2 illustrates an electrode part of the device for manufacturing an organic hydride of the present embodiment. FIG. 2 shows a plan view of the MEA viewed from the cathode side, a cross sectional view taken from line D-E in the plan view, and an enlarged view. The MEA includes a solid polymer electrolyte membrane 21 on which a water-blocking layer 27 is formed, a cathode catalyst layer 22 and an anode catalyst layer 23 which are formed on the front and back of the solid polymer electrolyte membrane 21.
As illustrated in the cross sectional view taken from line D-E, in the MEA, the cathode and the anode are formed on the upper and lower sides of the solid polymer electrolyte membrane 21, respectively, as dense catalyst layers, the water-bloc layer 27 formed on the membrane 21. As illustrated in the enlarged view of F, in the cathode catalyst layer 22, a catalytic metal 24 is supported on a catalyst supporter 25. The catalyst supporters 25 are bonded to each other by a solid polymer electrolyte 26. The catalytic metal 24 has a network structure in which its portions are connected to each other through the catalyst supporter 25, and forms a passing way for electrons necessary for the reaction (2). In the same manner, the solid polymer electrolyte 26 in the catalyst layer also has a network structure in which its portions are connected to each other, and forms a passing way for protons necessary for the reaction (2).
The electrode reaction is conducted on three-phase interfaces in which the metal catalyst 24 on the catalyst supporter 25, the electrolyte and the reactive substance contact each other. In the electrode of the present embodiment, the solid polymer electrolyte membrane 26 forms the passing way for protons, so that the three-phase interfaces are formed also in the metal catalyst 24, which does not directly contact the solid polymer electrolyte membrane 21. Accordingly, the electrode has a structure in which a large volume of the metal catalyst can contribute to the electrode reaction.
In the electrodes of the device for manufacturing an organic hydride of the present embodiment, the water-blocking layer 27 is formed on the solid polymer electrolyte membrane, so that the water in the anode can be prevented from passing to the cathode. Thus, an organic hydride can be manufactured with a high efficiency.
FIG. 3 illustrates a structure of electrodes in a conventional technique. In the electrodes illustrated in FIG. 3, a catalyst supporter 35 supporting a metal catalyst 34 is directly formed on each surface of a solid polymer electrolyte membrane 31. In the electrode structure in a conventional technique, a portion of the metal catalyst 34 which contributes to the electrode reaction is present only in its region directly contacting the electrolyte membrane. The metal catalyst 34 has small quantity of three-phase interface, so that the catalyst quantity contributing to the reaction is limited. Moreover, it is considered that the formation of the network structure of the catalyst is small in quantity, leading to high resistance.
In FIG. 3, the electrode structure in a conventional technique has been illustrated. The electrodes illustrated in FIG. 3 have a structure in which the catalyst supporter 35 supporting the catalytic metal 34 is mixed with a solid polymer electrolyte 36 on each surface of the solid polymer electrolyte membrane 31. In a conventional technique, passed water 37 is present in the cathode catalyst layer, the passed water 37 being water which has passed through the solid polymer electrolyte membrane 31 from the anode. Water and a substance to be hydrogenated, such as toluene, are insoluble into each other, not miscible with each other. Thus, when water is present in the cathode catalyst layer 32, the water hinders the supply of toluene into the catalyst. As a result, on the catalytic metal 38 to which no substance to be hydrogenated, such as toluene, is supplied, it considered that hydrogen is generated according to a formula (3) illustrated below, without hydrogenation reaction.
2H⁺+2e ⁻H₂ (3)
Thus, the electrodes in a conventional technique include the catalyst causing no reaction of hydrogenation onto the substance to be hydrogenated, so that the manufacture of any organic hydride is restricted. As a result, it is considered that energy efficiency is low in a conventional technique.
The MEA of the present invention can be produced by the following method. First, a cathode catalyst paste and an anode catalyst paste are produced. The cathode catalyst paste is obtained by sufficiently mixing a supporter supporting a catalytic metal, a solid polymer electrolyte, and a solvent in which the solid polymer electrolyte is soluble. The anode catalyst paste is obtained by sufficiently mixing a catalytic metal, a solid polymer electrolyte, and a solvent in which the solid polymer electrolyte is soluble. These pastes are each sprayed onto a peelable film, such as a polyfluoroethylene (PTFE) film, by a spray drying method, for example. The resultants are dried at 80° C. to vaporize the respective solvents to form a cathode catalyst layer and an anode catalyst layer. Next, a hot press method is used to join the cathode and anode catalyst layers sandwiching a solid polymer electrolyte membrane including a water-blocking layer therebetween. The peelable film (PTFE) is then peeled. Thus, the MEA of the invention can be produced.
In another example of the production of the MEA of the invention, a spray-dry method is used to spray a cathode catalyst paste and an anode catalyst paste directly onto a solid polymer electrolyte membrane including a water-blocking layer. The cathode catalyst paste is obtained by sufficiently mixing a supporter supporting a catalytic metal, a solid polymer electrolyte, and a solvent in which the solid polymer electrolyte is soluble. The anode catalyst paste is obtained by sufficiently mixing a catalytic metal and a solid polymer electrolyte, and a solvent in which the solid polymer electrolyte is soluble.
The organic polymer included in the solid polymer electrolyte membrane can be perfluorocarbon sulfonic acid, or a polymer yielded by incorporating a dopant of a proton donor, such as a sulfonate, phosphonate or carboxylate group, or bonding/fixing the donor chemically into polystyrene, polyetherketone, polyetheretherketone, polysulfone, polyethersulfone or some other engineering plastic. It is desired to make the material into a crosslinked structure, or fluoridate the material partially to make the material high in stability. Moreover, a composite electrolyte membrane may be used which is composed of an organic polymer and, e.g., a metal oxide hydrate.
The layer that blocks water from passing through is a layer which can pass through hydrogen ions and blocks water. The layer includes inorganic substance such as palladium and any palladium alloy, for example. Examples of metals which form the alloy with palladium include transition metals such as Rh, Cu, Co, Ir, and Ag. Furthermore, as the metal to be combined with palladium to make the alloy, various metals are conceivable, examples thereof including alkaline earth metals such as Mg and Ca, and rare earth metals such as La and Nd. For the layer that blocks water from passing through, a hydrogen storage alloy may be used. Examples of the hydrogen storage alloy include Ti—Fe based metals, V based metals, Mg based alloys, and Ca based alloys. Other examples thereof include AB₂type metals, each of which contains, as a base, a transition metal such as Ti, Mn, Zr or Ni; and LaNi₅, ReNi₅, and other AB₅type metals, each of which contains, as a base, an alloy containing a rare earth metal, Nb or Zr, and 5 atoms of a transition metal having a catalytic effect (such as Ni, Co or Al) per atom of the rare earth metal, Nb or Zr. Furthermore, it is allowable to use an organic polymer small in quantity of proton donors contained therein, such as sulfonate, phosphonate and carboxylate groups. The organic polymer small in the proton donor quantity is desirably an organic polymer having an amount of ion exchange of 0.75 meq/g or less per dry weight.
The water-blocking layer may be formed on the surface of the solid polymer electrolyte membrane or the inside of the solid polymer electrolyte membrane. In the invention, a layer that blocks water from passing through is formed to restrict the amount of water passing through. The water moves following the movement of protons. Then, the amount of the water passing through is varied in accordance with the value of the flowing current. The membrane electrode assembly including the water-blocking layer in the invention desirably has an amount of water passing through of 30 μg/cm²·sec or less when the current density value is 60 mA/cm². A water-blocking layer described above is used to satisfy this requirement.
In the solid polymer electrolyte included in each of the catalyst layers, a polymer material exhibiting proton conductivity is used. Examples thereof include sulfonated or alkylenesulfonated fluorine-contained polymers and polystyrenes, typical examples thereof including perfluorocarbon based sulfonic acid resins, and polyperfluorostyrene based sulfonic acid resins. Other examples thereof include polysulfones, polyethersulfones, polyetherethersulfones, polyetheretherketones, and materials in which a proton donor such as a sulfonate group is introduced in a hydrocarbon based polymer.
The catalytic metal used in the invention can be a catalytic material having a hydrogenating effect. The material may be, for example, a metal such as Ni, Pd, Pt, Rh, Ir, Re, Ru, Mo, W, V, Os, Cr, Co or Fe, or a catalyst of an alloy of any of these metals. The hydrogenating catalyst is preferably made into fine particles to decrease costs by a reduction in the catalytic metal and increase the reaction surface area. In order to prevent reduction of the specific surface area of the catalyst by the aggregation of the fine particles, the catalyst may be supported on a supporter. The method for producing the catalyst may be a co-precipitation method, a thermal decomposition method or an electroless plating method, and is not particularly limited.
The material of the supporter for the cathode catalyst may be, for example, a carbon material such as activated carbon, carbon nanotube or graphite, silica, alumina, or an alumina silicate such as zeolite. However, when a carbon material is present in the anode, the carbon may be unfavorably oxidized. Thus, the material of the supporter for the anode catalyst may be a non-carbon material such as silica, alumina, or an alumina silicate such as zeolite. Alternatively, in the anode, only the catalytic metal may be used without using any supporting material.
The substance to be hydrogenated may be anyone of benzene, toluene, xylene, mesitylene, naphthalene, methylnaphthalene, anthracene, biphenyl and phenanthroline, and alkyl-substituted compounds thereof, or a mixture of two or more of these compounds. When hydrogen is added to carbon-carbon double bonds of these compounds, the compounds can store the hydrogen.
Hereinafter, the embodiments of the invention will be described in detail. The invention is not limited to the following embodiments.

Embodiment 1

As a solid polymer electrolyte membrane, a membrane was used which was obtained by physically bonding a palladium membrane having a thickness of 25 μm onto a surface of a Nafion (manufactured by Du Pont). The palladium membrane was bonded to the surface on the anode side.
A spray coater was used to apply a catalyst slurry directly onto the solid polymer electrolyte membrane to form a cathode catalyst layer. In the following steps, the cathode catalyst layer was formed by the application onto the solid polymer electrolyte membrane.
The Nafion onto which the palladium membrane was bonded was put on a hot plate of a substrate, and then sucked to be fixed thereon. The temperature of the hot plate was set to 50° C.
Next, a mask was put thereto, and a spray coater (manufactured by Nordson Corp.) was used to apply a cathode catalyst slurry thereon. The used cathode catalyst slurry was a slurry obtained by mixing a platinum supporting carbon catalyst TEC10E70TPM (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), water, a 5% by weight Nafion solution, and a 221 solution (1-propanol:2-propanol:water=2:2:1) with each other at a ratio by weight of 2:1.2:5.4:10.6. Conditions for the application were as follows. The solution pressure was set to 0.01 MPa. The swirl pressure was set to 0.15 MPa. The spraying pressure was set to 0.15 MPa. The distance from the gun to the substrate was set to 60 mm. The temperature of the substrate was set to 50° C. The amount of the cathode catalyst was set to 0.4 mgPt·cm⁻².
The cathode catalyst layer was formed on the surface of the Nafion on which the palladium membrane was bonded. An anode catalytic slayer was formed on the back surface of the Nafion. The anode catalyst layer was formed by a transferring method. First, an anode catalyst slurry was prepared. The used anode catalyst slurry was obtained by mixing a platinum black HiSPEC1000 (manufactured by Johnson Matthey PLC), a 5% by weight Nafion solution, and a 221 solution with each other at a ratio by weight of 1:1.11:2.22. An applicator was used to apply this slurry onto a sheet made of Teflon (registered trademark). The anode catalyst layer applied on the sheet of Teflon (registered trademark) was formed on the surface of the Nafion on which the palladium membrane was bonded by thermal transfer using a hot press (SA-401-M manufactured by Tester Sangyo Co., Ltd.). The hot press pressure was set to 37.2 kgf·cm⁻², the hot press temperature to 120° C., and the hot press time to 2 minutes. The amount of the anode catalyst was set to 4.8 mgPt·cm⁻².
The produced MEA was integrated into the device for manufacturing an organic hydride illustrated in FIG. 1. The cell resistance thereof was 200 mΩ.
Toluene was supplied as a substance to be hydrogenated to the cathode at each of flow rates of 0.03 mL/min and 0.1 mL/min. Pure water was supplied to the anode at a flow rate of 5 mL/min. In these states, a voltage of 2.2 V was applied to between the anode and the cathode. The temperature of the cell was set to each of 25, 40, 60 and 80° C.
FIG. 4 shows the current values relative to the temperatures of the cell. As the cell temperature was made higher, the current densities became larger. The reason of this is considered that as the temperature became higher, the reaction activity of the electrode catalysts for the reaction became higher. In the case of supplying toluene in the amounts of 0.03 mL/min and 0.1 mL/min, the result was that the current flowed at substantially the same level.
After the hydrogenation reaction under each of the conditions, the cathode solution was collected and analyzed by gas chromatography to find a generation of methylcyclohexane, which is an organic hydride. This suggests that the hydrogenation reaction of toluene yielded methylcyclohexane with the electrodes in the invention. The solution collected from the cathode contained no water. It is believed that the palladium membrane formed on the surface of the Nafion was able to prevent the water from passing through from the anode.
FIG. 5 shows the conversion ratios from toluene to methylcyclohexane in the hydrogenation reaction. The conversion ratios were calculated from peak areas of the gas chromatograph according to the following equation:
Conversion ratio=“the peak area of methylcyclohexane”/(“the peak area of toluene”+“the peak area of methylcyclohexane”)×100. (4)
Methylcyclohexane was detected at each of the cell temperatures of 25, 40, 60 and 80° C., and the conversion ratios became larger as the cell temperature became higher. The conversion ratios were higher at the supply amount of toluene of 0.03 mL/min than at that of 0.1 mL/min. The reason of this is considered that as the supply rate of toluene was smaller, a chance for toluene to contact the electrode catalysts was increased. The condition that the cell temperature was 80° C. and the toluene flow rate was 0.03 mL/min gave the highest conversion ratio of 68% among the conditions in this embodiment.

Comparative Example 1

As a solid polymer electrolyte membrane, an MEA was produced using a Nafion. Other producing conditions were same as described above.
The produced MEA was integrated into the device for manufacturing an organic hydride illustrated in FIG. 1. The cell resistance thereof was measured to be 250 mΩ.
Under the same conditions as in embodiment 1, a test of the hydrogenation reaction to toluene was conducted. At a cell temperature of each of 25, 40, 60 and 80° C., a voltage of 2.2 V was applied to between the anode and the cathode. FIG. 6 shows the current values relative to the temperatures of the cell. As the temperature of the cell was made higher, larger currents flowed. However, at each of the temperatures, the current densities were lower than in embodiment 1.
After the hydrogenation reaction under each of the conditions, the cathode solution was collected and analyzed by gas chromatography to find a generation of methylcyclohexane, which is an organic hydride. However, at each of the temperatures, the waste solution collected from the cathode was separated into two phases. The upper phase was presumed to be toluene and methylcyclohexane, and the lower phase was presumed to be water. As the temperature was higher, the proportion of the water in the lower phase was larger. It is considered that the water came to the cathode from the anode passing through the electrolyte membrane. In particular, it is presumed that as the cell temperature was higher and a larger current flowed, a larger quantity of protons was moved from the anode to the cathode and, in accordance with the movement of the protons, a larger quantity of water was moved.
FIG. 7 shows the conversion ratios from toluene to methylcyclohexane. As the cell temperature was made higher, the conversion ratios became higher. However, the conversion ratios were smaller than in embodiment 1. The reason of this is considered that the passed water was present in the cathode catalyst layer and the water hindered the supply of toluene to the catalyst. As a result, it is presumed that hydrogen was generated on the catalyst to which no toluene was supplied, so that methylcyclohexane was not generated to lower the conversion ratios.

Embodiment 2

A Nafion was used as an electrolyte membrane, and an S-PES (sulfonated polyethersulfone) having thickness of 10 μm was bonded onto the surface of the Nation. S-PES is an organic polymer obtained by introducing sulfonate groups into polyethersulfone. The used S-PES had an amount of ion exchange of 0.6 meq/g per dry weight. Other conditions for producing the MEA were same as in embodiment 1.
The produced MEA was integrated into the device for manufacturing an organic hydride illustrated in FIG. 1. The cell resistance thereof was measured to be 350 mΩ. Under the same conditions as in embodiment 1, a test of the hydrogenation reaction to toluene was conducted. At a cell temperature of each of 25, 40, 60 and 80° C., a voltage of 2.2 V was applied to between the anode and the cathode.
After the hydrogenation reaction under each of the conditions, the cathode solution was collected and analyzed by gas chromatography to find a generation of methylcyclohexane, which is an organic hydride. At each of the temperatures, the waste solution collected from the cathode was separated into two phases, although the solution contained smaller amount of water than in comparative example 1. The reason of this is considered that the S-PES did not completely prevent the water from passing through. However, comparing this case with the case where only Nafion was used as the electrolyte membrane in comparative example 1, higher conversion ratios were obtained in this case since the amount of the passed water was reduced. The highest conversion ratio was 58% when the cell temperature was 80° C. and the toluene flow rate was 0.03 mL/min.

EXPLANATION OF REFERENCE CHARACTERS

11: separator
12, 21 and 31: solid polymer electrolyte membranes
13, 23 and 33: anode catalyst layers
14: cathode catalyst layer
15: gas diffusion layer
16: gasket
22 and 32: cathode catalyst layers
24 and 34: catalytic metals
25 and 35: catalyst supporters
26 and 36: solid polymer electrolytes
27: water-blocking layer
37: passed water
38: catalytic metal not contributing to the reaction.

Claims

What is claimed is:

1. A device for manufacturing an organic hydride comprising:

a membrane electrode assembly including a cathode catalyst layer that reduces a substance to be hydrogenated, an anode catalyst layer that oxidizes water, and a proton-conductive solid polymer electrolyte membrane disposed between the cathode catalyst layer and the anode catalyst layer;

a member that supplies the substance to be hydrogenated to the cathode catalyst layer; and

a member that supplies water or water vapor to the anode catalyst layer;

wherein a layer that blocks water is formed on a surface or inside of the solid polymer electrolyte membrane.

2. The device for manufacturing an organic hydride according to claim 1,

wherein the layer that blocks water includes palladium or a palladium alloy.

3. The device for manufacturing an organic hydride according to claim 1,

wherein the layer that blocks water includes an organic polymer having an amount of ion exchange of 0.75 meq/g or less per dry weight.

4. The device for manufacturing an organic hydride according to claim 1,

wherein the cathode catalyst layer includes a catalytic metal and a supporter that supports the catalytic metal, and

wherein the anode catalyst layer includes only a catalytic metal or includes a catalytic metal and a non-carbon supporter that supports the catalytic metal.

5. The device for manufacturing an organic hydride according to claim 1,

wherein the substance to be hydrogenated is selected from the group consisting of benzene, toluene, xylene, mesitylene, naphthalene, methylnaphthalene, and anthracene.

6. The device for manufacturing an organic hydride according to claim 1,

wherein the catalytic metal includes platinum, ruthenium, rhodium, palladium, iridium, molybdenum, rhenium, tungsten, and an alloy including at least one of these metals.

7. A device for manufacturing an organic hydride comprising:

gas diffusion layers disposed on a surface of the cathode catalyst layer and a surface of the anode catalyst layer; and

separators, each of which is disposed on a surface of each of the gas diffusion layers and includes a channel formed on a surface of the separator that contacts the gas diffusion layer;

8. The device for manufacturing an organic hydride according to claim 7,

wherein the layer that blocks water includes palladium or a palladium alloy.

9. The device for manufacturing an organic hydride according to claim 7,

10. The device for manufacturing an organic hydride according to claim 7,

wherein the substance to be hydrogenated is supplied into the channel of the separator at the cathode catalyst layer side, and

wherein water or water vapor is supplied into the channel of the separator at the anode catalyst layer side.

11. The device for manufacturing an organic hydride according to claim 7, wherein the substance to be hydrogenated is selected from the group consisting of benzene, toluene, xylene, mesitylene, naphthalene, methylnaphthalene, and anthracene.

12. The device for manufacturing an organic hydride according to claim 7,