TECHNICAL FIELD
[0001] The present invention relates to an organic hydride production apparatus.
BACKGROUND ART
[0002] In recent years, in order to suppress the carbon dioxide emission amount in the energy
generation process, renewable energy is expected to be used, which is obtained by
solar light, wind power, hydraulic power, geothermal power generation, and the like.
As an example, a system for generating hydrogen by performing water electrolysis using
power derived from renewable energy has been devised. In addition, an organic hydride
system has attracted attention as an energy carrier for large-scale transportation
and storage of hydrogen derived from renewable energy.
[0003] Regarding a technique for producing an organic hydride, a conventional organic hydride
production apparatus including an anode for generating protons from water, a cathode
for hydrogenating an organic compound (substance to be hydrogenated) having an unsaturated
bond, and a membrane for separating the anode and the cathode is known (see, for example,
Patent Literature 1). In the organic hydride production apparatus, water is supplied
to the anode, a substance to be hydrogenated is supplied to the cathode, and a current
is flown between the anode and the cathode, so that hydrogen is added to the substance
to be hydrogenated to obtain an organic hydride.
RELATED-ART LITERATURE
PATENT LITERATURE
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0005] As a result of intensive studies on the above-described technique for producing an
organic hydride, the present inventors have recognized that there is room for improving
stability of electrolytic performance of the organic hydride production apparatus
in the conventional technique.
[0006] The present invention has been made in view of such a situation, and an object thereof
is to provide a technique for improving stability of electrolytic performance of an
organic hydride production apparatus.
SOLUTION TO PROBLEM
[0007] One aspect of the present invention is an organic hydride production apparatus. This
organic hydride production apparatus includes: a membrane electrode assembly in which
an anode electrode that oxidizes water in an anolyte to generate protons and a cathode
electrode that hydrogenates a substance to be hydrogenated in a catholyte with the
protons to generate an organic hydride are laminated with a membrane that moves the
protons from an anode electrode side to a cathode electrode side interposed therebetween;
a cathode flow path that overlaps the membrane electrode assembly when viewed from
a lamination direction of the cathode electrode, the membrane, and the anode electrode,
and feeds and discharges the catholyte to and from the cathode electrode; and a support
member that supports the membrane electrode assembly so as to suppress fitting of
the membrane electrode assembly into the cathode flow path.
[0008] Any combinations of the above components and conversion of the expressions in the
present disclosure between methods, devices, systems, and the like are also effective
as aspects of the present disclosure.
ADVANTAGEOUS EFFECTS OF INVENTION
[0009] According to the present invention, stability of electrolytic performance of an organic
hydride production apparatus can be improved.
BRIEF DESCRIPTION OF DRAWINGS
[0010]
[Fig. 1] Fig. 1 is a schematic diagram of an organic hydride production system according
to an embodiment.
[Fig. 2] Fig. 2 is a cross-sectional view of an organic hydride production apparatus.
[Fig. 3] Fig. 3 is a cross-sectional view taken along the line A-A of Fig. 2.
[Fig. 4] Fig. 4 is a schematic diagram of a membrane electrode assembly and a cathode
flow path viewed from a lamination direction of an electrode and a membrane.
[Fig. 5] Fig. 5 is a diagram showing a relation between a current density and a toluene
concentration at Faraday efficiency of 95% in organic hydride production apparatuses
of Example 1 and Comparative Example 1.
DESCRIPTION OF EMBODIMENTS
[0011] Hereinafter, the present invention will be described based on preferred embodiments
with reference to the drawings. The embodiments are illustrative rather than limiting
the technical scope of the present invention, and all features described in the embodiments
and combinations thereof are not necessarily essential to the invention. Therefore,
the contents of the embodiments can be subjected to many design changes such as changes,
additions, and deletions of components without departing from the spirit of the invention
defined in the claims. A new embodiment to which the design change is made has the
effect of the combined embodiments and modifications. In the embodiment, the contents
that can be subjected to such design changes are emphasized with notations such as
"of the present embodiment" and "in the present embodiment", but the design changes
are allowed even in the contents without such notations. Any combination of the components
described in the embodiment is also effective as an aspect of the present invention.
The same or equivalent components, members, and processes illustrated in the drawings
are denoted by the same reference numerals, and redundant description will be omitted
as appropriate. In addition, the scale and shape of each part illustrated in each
drawing are set for convenience in order to facilitate the description, and are not
to be limitedly interpreted unless otherwise specified. Furthermore, when the terms
"first", "second", and the like are used in the present specification or claims, the
terms do not represent any order or importance, but are used to distinguish one configuration
from another configuration. In addition, in each drawing, some of members that are
not important for describing the embodiments are omitted.
[0012] Fig. 1 is a schematic diagram of an organic hydride production system 1 according
to the embodiment. The organic hydride production system 1 as an example includes
an organic hydride production apparatus 2, an anolyte supply device 4, and a catholyte
supply device 6.
[0013] The organic hydride production apparatus 2 is an electrolyzer for generating an organic
hydride by hydrogenating a substance to be hydrogenated which is a dehydrogenated
product of the organic hydride by an electrochemical reduction reaction. The organic
hydride production apparatus 2 includes a membrane electrode assembly 8. The membrane
electrode assembly 8 has a structure in which an anode electrode 10 and a cathode
electrode 12 are laminated with a membrane 14 interposed therebetween. Although only
one organic hydride production apparatus 2 is shown in Fig. 1, the organic hydride
production system 1 may include a plurality of organic hydride production apparatuses
2. In this case, the respective organic hydride production apparatuses 2 are laminated
in the same direction such that the anode electrode 10 and the cathode electrode 12
are arranged in the same direction. As a result, the organic hydride production apparatuses
2 are electrically connected in series. Note that the organic hydride production apparatuses
2 may be connected in parallel, or may be a combination of series connection and parallel
connection.
[0014] The anode electrode 10 (anode) oxidizes water in an anolyte LA to generate protons.
The anode electrode 10 has, for example, a metal such as iridium (Ir), ruthenium (Ru),
or platinum (Pt), or a metal oxide thereof as an anode catalyst. The anode catalyst
may be dispersedly supported or coated on a base material having electron conductivity.
The base material includes a material containing, for example, a metal such as titanium
(Ti) or stainless steel (SUS) as a main component. Examples of the form of the base
material include a woven fabric sheet or a nonwoven fabric sheet, a mesh, a porous
sintered body, a foamed molded body (foam), and an expanded metal.
[0015] The cathode electrode 12 (cathode) hydrogenates a substance to be hydrogenated in
a catholyte LC with protons to generate an organic hydride. The cathode electrode
12 contains, for example, platinum or ruthenium as a cathode catalyst for hydrogenating
the substance to be hydrogenated. It is preferable that the cathode electrode 12 also
contains a porous catalyst support that supports the cathode catalyst. The catalyst
support includes an electron-conductive material such as porous carbon, a porous metal,
or a porous metal oxide. Furthermore, the cathode catalyst is coated with an ionomer
(cation exchange ionomer). For example, the catalyst support which is in the state
of supporting the cathode catalyst is coated with an ionomer. Examples of the ionomer
include a perfluorosulfonic acid polymer such as Nafion (registered trademark) or
Flemion (registered trademark). It is preferable that the cathode catalyst is partially
coated with the ionomer. As a result, it is possible to efficiently supply three elements
(the substance to be hydrogenated, a proton, and an electron) necessary for an electrochemical
reaction in the cathode electrode 12 to the reaction field.
[0016] The membrane 14 is sandwiched between the anode electrode 10 and the cathode electrode
12. The membrane 14 of the present embodiment includes a solid polymer electrolyte
membrane having proton conductivity, and transfers protons from the side of the anode
electrode 10 to the side of the cathode electrode 12. The solid polymer electrolyte
membrane is not particularly limited as long as it is a material through which protons
conduct, and examples thereof include a fluorine-based ion exchange membrane having
a sulfonate group.
[0017] The anolyte LA is supplied to the anode electrode 10 by the anolyte supply device
4. The anolyte LA contains water to be supplied to the anode electrode 10. Examples
of the anolyte LA include an aqueous sulfuric acid solution, an aqueous nitric acid
solution, an aqueous hydrochloric acid solution, pure water, and ion-exchanged water.
[0018] The catholyte LC is supplied to the cathode electrode 12 by the catholyte supply
device 6. The catholyte LC contains an organic hydride raw material (substance to
be hydrogenated) to be supplied to the cathode electrode 12. As an example, the catholyte
LC does not contain an organic hydride before the start of the operation of the organic
hydride production system 1, and after the start of the operation, the organic hydride
generated by electrolysis is mixed in, whereby the catholyte becomes the liquid mixture
of the substance to be hydrogenated and the organic hydride. The substance to be hydrogenated
and the organic hydride are preferably a liquid at 20°C and 1 atm.
[0019] The substance to be hydrogenated and the organic hydride are not particularly limited
as long as they are organic compounds capable of adding/desorbing hydrogen by reversibly
causing a hydrogenation reaction/dehydrogenation reaction. As the substance to be
hydrogenated and the organic hydride used in the present embodiment, an acetone-isopropanol
type, a benzoquinone-hydroquinone type, an aromatic hydrocarbon type, and the like
can be widely used. Among these, the aromatic hydrocarbon type is preferable from
the viewpoint of transportability during energy transport or the like.
[0020] An aromatic hydrocarbon compound used as the substance to be hydrogenated is a compound
containing at least one aromatic ring. Examples of the aromatic hydrocarbon compound
include benzene, alkylbenzene, naphthalene, alkylnaphthalene, anthracene, and diphenylethane.
The alkylbenzene contains a compound in which 1 to 4 hydrogen atoms in the aromatic
ring are substituted with a linear alkyl group or a branched alkyl group having 1
to 6 carbons. Examples of such a compound include toluene, xylene, mesitylene, ethylbenzene,
and diethylbenzene. The alkylnaphthalene contains a compound in which 1 to 4 hydrogen
atoms in the aromatic ring are substituted with a linear alkyl group or a branched
alkyl group having 1 to 6 carbons. Examples of such a compound include methylnaphthalene.
These compounds may be used alone or in combination.
[0021] The substance to be hydrogenated is preferably at least one of toluene and benzene.
It is also possible to use a nitrogen-containing heterocyclic aromatic compound such
as pyridine, pyrimidine, pyrazine, quinoline, isoquinoline, N-alkylpyrrole, N-alkylindole,
or N-alkyldibenzopyrrole as the substance to be hydrogenated. The organic hydride
is obtained by hydrogenating the above-described substance to be hydrogenated, and
examples thereof include cyclohexane, methylcyclohexane, dimethylcyclohexane, and
piperidine.
[0022] A reaction that occurs in a case where toluene (TL) is used as an example of the
substance to be hydrogenated in the organic hydride production apparatus 2 is as follows.
The organic hydride obtained in a case where toluene is used as the substance to be
hydrogenated is methylcyclohexane (MCH).
<Electrode Reaction in Anode Electrode>
[0023]
3H
2O→3/2O
2+6H
++6e
-
<Electrode Reaction in Cathode Electrode>
[0025] That is, the electrode reaction in the anode electrode 10 and the electrode reaction
in the cathode electrode 12 proceed in parallel. The protons generated by electrolysis
of water in the anode electrode 10 are supplied to the cathode electrode 12 through
the membrane 14. Electrons generated by electrolysis of water are supplied to the
cathode electrode 12 via an external circuit. The protons and electrons supplied to
the cathode electrode 12 are used for the hydrogenation of toluene in the cathode
electrode 12. As a result, methylcyclohexane is generated.
[0026] Therefore, according to the organic hydride production system 1 according to the
present embodiment, the electrolysis of water and the hydrogenation reaction of the
substance to be hydrogenated can be performed in one step. For this reason, organic
hydride production efficiency can be increased as compared with a conventional technique
in which the organic hydride is produced by a two-step process which includes a process
of producing hydrogen by water electrolysis or the like and a process of chemically
hydrogenating the substance to be hydrogenated in a reactor such as a plant. Furthermore,
since the reactor for performing the chemical hydrogenation and a high-pressure vessel
for storing the hydrogen produced by the water electrolysis or the like are not required,
a significant reduction in facility cost can be achieved.
[0027] In the cathode electrode 12, the following hydrogen gas generation reaction may occur
as a side reaction together with the hydrogenation reaction of the substance to be
hydrogenated which is the main reaction. As the supply amount of the substance to
be hydrogenated to the cathode electrode 12 becomes insufficient, this side reaction
is likely to occur.
<Side Reaction That Can Occur in Cathode Electrode>
[0029] When the protons move from the side of the anode electrode 10 to the side of the
cathode electrode 12 through the membrane 14, the protons move together with water
molecules. Therefore, water is accumulated in the cathode electrode 12 as the electrolytic
reduction reaction proceeds.
[0030] The organic hydride production apparatus 2 is supplied with power from an external
power supply (not shown). When power is supplied from the power supply to the organic
hydride production apparatus 2, a predetermined electrolytic current is applied between
the anode electrode 10 and the cathode electrode 12 of the organic hydride production
apparatus 2, and an electrolytic current flows. The power supply sends power supplied
from a power supply device to the organic hydride production apparatus 2. The power
supply device can include a power generation device that generates power using renewable
energy, for example, a wind power generation device, a solar power generation device,
or the like. Note that the power supply device is not limited to the power generation
device using renewable energy, and may be a system power supply, a storage device
storing power from the power generation device using renewable energy or the system
power supply, or the like. In addition, a combination of two or more of them may be
used.
[0031] The anolyte supply device 4 includes an anolyte tank 16, a first anode pipe 18, a
second anode pipe 20, and an anode pump 22. The anolyte LA is stored in the anolyte
tank 16. The anolyte tank 16 is connected to the anode electrode 10 by the first anode
pipe 18. The anode pump 22 is provided in the middle of the first anode pipe 18. The
anode pump 22 can include known pumps such as a gear pump and a cylinder pump. Note
that the anolyte supply device 4 may circulate the anolyte LA using a liquid feeding
device other than the pump. The anolyte tank 16 is connected to the anode electrode
10 by the second anode pipe 20.
[0032] The anolyte LA in the anolyte tank 16 flows into the anode electrode 10 through the
first anode pipe 18 by driving of the anode pump 22. The anolyte LA flowing into the
anode electrode 10 is subjected to an electrode reaction in the anode electrode 10.
The anolyte LA in the anode electrode 10 is returned to the anolyte tank 16 through
the second anode pipe 20. As an example, the anolyte tank 16 also functions as a gas-liquid
separator. In the anode electrode 10, oxygen gas is generated by the electrode reaction.
Therefore, the oxygen gas is mixed into the anolyte LA discharged from the anode electrode
10. The anolyte tank 16 separates the oxygen gas in the anolyte LA from the anolyte
LA and discharges the oxygen gas to the outside of the system.
[0033] In the anolyte supply device 4 of the present embodiment, the anolyte LA is circulated
between the anode electrode 10 and the anolyte tank 16. However, the present invention
is not limited to this configuration, and the anolyte LA may be sent from the anode
electrode 10 to the outside of the system without being returned to the anolyte tank
16.
[0034] The catholyte supply device 6 includes a catholyte tank 24, a first cathode pipe
26, a second cathode pipe 28, a third cathode pipe 30, a cathode pump 32, and a separator
34. The catholyte LC is stored in the catholyte tank 24. The catholyte tank 24 is
connected to the cathode electrode 12 by the first cathode pipe 26. The cathode pump
32 is provided in the middle of the first cathode pipe 26. The cathode pump 32 can
include known pumps such as a gear pump and a cylinder pump. Note that the catholyte
supply device 6 may circulate the catholyte LC using a liquid feeding device other
than the pump.
[0035] The separator 34 is connected to the cathode electrode 12 by the second cathode pipe
28. The separator 34 includes a known gas-liquid separator and a known oil-water separator.
The separator 34 is connected to the catholyte tank 24 by the third cathode pipe 30.
[0036] The catholyte LC in the catholyte tank 24 flows into the cathode electrode 12 through
the first cathode pipe 26 by driving of the cathode pump 32. The catholyte LC flowing
into the cathode electrode 12 is subjected to an electrode reaction in the cathode
electrode 12. The catholyte LC in the cathode electrode 12 flows into the separator
34 through the second cathode pipe 28. The hydrogen gas may be generated by the side
reaction in the cathode electrode 12. Therefore, the hydrogen gas may be mixed in
the catholyte LC discharged from the cathode electrode 12. The separator 34 separates
the hydrogen gas in the catholyte LC from the catholyte LC and discharges the hydrogen
gas to the outside of the system. In addition, water moves from the anode electrode
10 to the cathode electrode 12 together with protons. Therefore, the water may be
mixed in the catholyte LC discharged from the cathode electrode 12. The separator
34 separates the water in the catholyte LC from the catholyte LC and discharges the
water to the outside of the system. The catholyte LC from which the hydrogen gas and
the water have been separated is returned to the catholyte tank 24 through the third
cathode pipe 30.
[0037] In the catholyte supply device 6 of the present embodiment, the catholyte LC is circulated
between the cathode electrode 12 and the catholyte tank 24. However, the present invention
is not limited to this configuration, and the catholyte LC may be sent to the outside
of the system from the cathode electrode 12 without being returned to the catholyte
tank 24.
[0038] Next, a structure of the organic hydride production apparatus 2 will be described
in detail. Fig. 2 is a cross-sectional view of the organic hydride production apparatus
2. Fig. 3 is a cross-sectional view taken along the line A-A of Fig. 2. Fig. 4 is
a schematic diagram of the membrane electrode assembly 8 and a cathode flow path 38
viewed from a lamination direction of the electrodes and the membrane. The organic
hydride production apparatus 2 of the present embodiment includes an anode flow path
36 (anode flow path formation structure), a cathode flow path 38 (cathode flow path
formation structure), a support member 40, a pair of plate members 42a and 42b, and
a gasket 44, in addition to the membrane electrode assembly 8.
[0039] The plate member 42a and the plate member 42b are made of a metal such as stainless
steel or titanium, for example. The plate member 42a is laminated on the membrane
electrode assembly 8 from the side of the anode electrode 10. The plate member 42b
is laminated on the membrane electrode assembly 8 from the side of the cathode electrode
12. Accordingly, the membrane electrode assembly 8 is sandwiched between the pair
of plate members 42a and 42b. A gap between the pair of plate members 42a and 42b
is sealed with the gasket 44. When the organic hydride production system 1 includes
only one organic hydride production apparatus 2, the pair of plate members 42a and
42b can correspond to a so-called end plate. When the organic hydride production system
1 includes a plurality of organic hydride production apparatuses 2, and another organic
hydride production apparatus 2 is arranged next to the plate member 42a or the plate
member 42b, the plate member can correspond to a so-called separator.
[0040] The cathode electrode 12 has a catalyst layer 12a and a diffusion layer 12b. The
catalyst layer 12a is disposed closer to the membrane 14 than the diffusion layer
12b. The catalyst layer 12a is in contact with a main surface of the membrane 14.
The catalyst layer 12a contains the cathode catalyst, the catalyst support, and the
ionomer described above. The diffusion layer 12b is in contact with a main surface
of the catalyst layer 12a on a side opposite to the membrane 14. The diffusion layer
12b uniformly diffuses the catholyte LC supplied from the outside into the catalyst
layer 12a. The organic hydride generated in the catalyst layer 12a is discharged to
the outside of the cathode electrode 12 through the diffusion layer 12b. The diffusion
layer 12b includes a conductive material such as carbon or a metal. In addition, the
diffusion layer 12b is a porous body such as a sintered body of fibers or particles
or a foamed molded body. Examples of the material included in the diffusion layer
12b include a carbon woven fabric (carbon cloth), a carbon nonwoven fabric, and carbon
paper. Note that the diffusion layer 12b may be omitted.
[0041] The anode flow path 36 is connected to the anode electrode 10. The anode flow path
36 feeds and discharges the anolyte LA to and from the anode electrode 10. In the
plate member 42a of the present embodiment, a groove is provided on a main surface
facing the anode electrode 10 side. This groove forms the anode flow path 36. The
anode flow path 36 covers an entire surface of the anode electrode 10, for example.
The first anode pipe 18 and the second anode pipe 20 are connected to the anode flow
path 36. As an example, the first anode pipe 18 is connected to a lower end of the
anode flow path 36, and the second anode pipe 20 is connected to an upper end of the
anode flow path 36. The connection positions of the first anode pipe 18 and the second
anode pipe 20 with respect to the anode flow path 36 can be appropriately changed.
By using the groove provided in the plate member 42a as the anode flow path 36, it
is possible to suppress an increase in the number of parts due to the provision of
the anode flow path 36, complication of the assembly process, and the like.
[0042] The cathode flow path 38 is connected to the cathode electrode 12. The cathode flow
path 38 feeds and discharges the catholyte LC to and from the cathode electrode 12.
In the plate member 42b of the present embodiment, a groove is provided on a main
surface facing the cathode electrode 12 side. This groove forms the cathode flow path
38. The first cathode pipe 26 and the second cathode pipe 28 are connected to the
cathode flow path 38. By using the groove provided in the plate member 42b as the
cathode flow path 38, it is possible to suppress an increase in the number of parts
due to the provision of the cathode flow path 38, complication of the assembly process,
and the like.
[0043] The cathode flow path 38 of the present embodiment includes a supply flow path 38a
(supply flow path formation structure) for supplying the catholyte LC to the cathode
electrode 12, and a collection flow path 38b (collection flow path formation structure)
for collecting the catholyte LC from the cathode electrode 12. As an example, each
of the supply flow path 38a and the collection flow path 38b extends in the vertical
direction. Note that "extending in the vertical direction" means that one end of a
substantially linear flow path is positioned above the other end. Therefore, each
flow path may extend obliquely with respect to a horizontal plane. The supply flow
path 38a is disposed near one end of the plate member 42b in a horizontal direction,
and the collection flow path 38b is disposed near the other end of the plate member
42b in the horizontal direction. The first cathode pipe 26 is connected to a lower
end of the supply flow path 38a, and the second cathode pipe 28 is connected to an
upper end of the collection flow path 38b.
[0044] The catholyte LC flowing from the first cathode pipe 26 into the supply flow path
38a flows from the lower side to the upper side in the supply flow path 38a, and is
sent to the cathode electrode 12. The catholyte LC flowing into the cathode electrode
12 moves toward the collection flow path 38b in the cathode electrode 12. The catholyte
LC that has reached the collection flow path 38b flows into the collection flow path
38b from the cathode electrode 12. Then, the catholyte LC flows from the lower side
to the upper side in the collection flow path 38b and is discharged to the second
cathode pipe 28. Note that the connection positions of the first cathode pipe 26 and
the second cathode pipe 28 with respect to the cathode flow path 38 can be appropriately
changed. For example, each pipe may be connected to a side surface rather than a bottom
surface and a top surface of the cathode flow path 38. In addition, the number and
arrangement of the supply flow path 38a and the collection flow path 38b can be appropriately
changed.
[0045] As shown in Fig. 4, the supply flow path 38a and the collection flow path 38b are
disposed so as to overlap the membrane electrode assembly 8 when viewed from the lamination
direction of the cathode electrode 12, the membrane 14, and the anode electrode 10.
Generally, in the organic hydride production apparatus, a high pressure is applied
to the membrane electrode assembly to bring the layers into close contact with each
other. Accordingly, the production efficiency of the organic hydride can be increased.
The pressure applied to the membrane electrode assembly is larger than the pressure
applied to a general fuel cell. For this reason, when the membrane electrode assembly
8 and the cathode flow path 38 overlap each other, the membrane electrode assembly
8 can be fitted into the cathode flow path 38. When the membrane electrode assembly
8 is fitted into the cathode flow path 38, a pressure loss generated in the catholyte
LC flowing through the cathode flow path 38 may increase. In addition, the cathode
flow path 38 is blocked, the supply of the substance to be hydrogenated to the cathode
electrode 12 is delayed, and the reaction for producing the organic hydride in at
least a part of the cathode electrode 12 may be stopped. In addition, generation of
hydrogen occurs due to the side reactions, and the Faraday efficiency during production
of the organic hydride may be reduced.
[0046] On the other hand, the organic hydride production apparatus 2 of the present embodiment
includes the support member 40 that supports the membrane electrode assembly 8 so
as to suppress fitting of the membrane electrode assembly 8 into the cathode flow
path 38. This makes it possible to maintain the circulation of the catholyte LC in
the cathode flow path 38. Therefore, the stability of the electrolytic performance
of the organic hydride production apparatus 2 can be improved.
[0047] The collection flow path 38b is located at the downstream of the supply flow path
38a in the flow of the catholyte LC, and tends to have a lower internal pressure than
the supply flow path 38a. For this reason, in the collection flow path 38b, the membrane
electrode assembly 8 is easily fitted as compared with the supply flow path 38a. Therefore,
the support member 40 is preferably disposed at least in the collection flow path
38b. In the present embodiment, the support members 40 are disposed in both the supply
flow path 38a and the collection flow path 38b. When the driving of the cathode pump
32 is stopped and the supply of the catholyte LC to the cathode electrode 12 is stopped,
the internal pressure of the supply flow path 38a may also decrease. Therefore, by
disposing the support member 40 in both the supply flow path 38a and the collection
flow path 38b, the stability of the electrolytic performance of the organic hydride
production apparatus 2 can be further improved.
[0048] The support member 40 as an example is an elongated body extending along the cathode
flow path 38 in the cathode flow path 38. That is, the support member 40 provided
in the supply flow path 38a extends along the supply flow path 38a, and the support
member 40 provided in the collection flow path 38b extends along the collection flow
path 38b. The support member 40 has a curved portion protruding toward the membrane
electrode assembly 8. This makes it easy to suppress fitting of the membrane electrode
assembly 8 into the cathode flow path 38. The support member 40 according to the present
embodiment is formed of a coil. The coil is formed of a metal such as titanium or
stainless steel, for example. The coil spirally extends from one end side to the other
end side inside each of the supply flow path 38a and the collection flow path 38b,
that is, inside the groove forming each flow path. This makes it possible to suppress
fitting of the membrane electrode assembly 8 into the cathode flow path 38 while suppressing
inhibition of the circulation of the catholyte LC by the support member 40.
(Modifications)
[0049] The organic hydride production apparatus 2 according to the above-described embodiment
can include the following modifications. That is, the support member 40 of the embodiment
is formed of a coil, but is not particularly limited to this configuration. For example,
the support member 40 may be formed of a stent. The stent is a meshed tube. Therefore,
the stent has a curved portion protruding toward the membrane electrode assembly 8.
The stent also extends along the cathode flow path 38. The material of the stent is
similar to that of the coil. The support member 40 may be formed of a porous member
having liquid permeability such as porous ceramics. The porous member may have a curved
portion protruding toward the membrane electrode assembly 8, or may be an elongated
body extending along the cathode flow path 38. By disposing the stent or the porous
member in the cathode flow path 38, similarly to the case of the coil, fitting of
the membrane electrode assembly 8 can be suppressed while the circulation of the catholyte
LC in the cathode flow path 38 is maintained. Note that the support member 40 may
be intermittently provided in the extension direction of the supply flow path 38a
and the collection flow path 38b.
[0050] The support member 40 may be formed of a plate material interposed between the cathode
flow path 38 and the membrane electrode assembly 8 and having a plurality of through
holes. Examples of such a plate material include a punching plate and a mesh plate.
As an example, the plate material is laminated between the plate member 42b and the
diffusion layer 12b. Also in such an aspect, fitting of the membrane electrode assembly
8 can be suppressed while the circulation of the catholyte LC between the cathode
flow path 38 and the cathode electrode 12 is maintained.
[0051] The embodiments may also be specified as items described below.
[First Item]
[0052] An organic hydride production apparatus (2) including:
a membrane electrode assembly (8) in which an anode electrode (10) that oxidizes water
in an anolyte (LA) to generate protons and a cathode electrode (12) that hydrogenates
a substance to be hydrogenated in a catholyte (LC) with the protons to generate an
organic hydride are laminated with a membrane (14) that moves the protons from an
anode electrode (10) side to a cathode electrode (12) side interposed therebetween;
a cathode flow path (38) that overlaps the membrane electrode assembly (8) when viewed
from a lamination direction of the cathode electrode (12), the membrane (14), and
the anode electrode (10), and feeds and discharges the catholyte (LC) to and from
the cathode electrode (12); and
a support member (40) that supports the membrane electrode assembly (8) so as to suppress
fitting of the membrane electrode assembly (8) into the cathode flow path (38) .
[Second Item]
[0053] The organic hydride production apparatus (2) according to the first item, including:
a plate member (42b) laminated on the membrane electrode assembly (8), wherein
the cathode flow path (38) is formed of a groove provided on a surface of the plate
member (42b).
[Third Item]
[0054] The organic hydride production apparatus (2) according to the first item or the second
item, wherein
the cathode flow path (38) includes a supply flow path (38a) to supply the catholyte
(LC) to the cathode electrode (12), and a collection flow path (38b) to collect the
catholyte (LC) from the cathode electrode (12), and
the support member (40) is disposed at least in the collection flow path (38b).
[Fourth Item]
[0055] The organic hydride production apparatus (2) according to the third item, wherein
the support member (40) is disposed in both the supply flow path (38a) and the collection
flow path (38b).
[Fifth Item]
[0056] The organic hydride production apparatus (2) according to any one of the first to
fourth items, wherein
the support member (40) is an elongated body extending along the cathode flow path
(38) in the cathode flow path (38) .
[Sixth Item]
[0057] The organic hydride production apparatus (2) according to the fifth item, wherein
the support member (40) has a curved portion protruding toward the membrane electrode
assembly (8).
[Seventh Item]
[0058] The organic hydride production apparatus (2) according to the sixth item, wherein
the support member (40) is formed of a coil or a stent.
[Eighth Item]
[0059] The organic hydride production apparatus (2) according to any one of the first to
sixth items, wherein
the support member (40) is formed of a porous member disposed in the cathode flow
path (38).
[Ninth Item]
[0060] The organic hydride production apparatus (2) according to any one of the first to
fourth items, wherein
the support member (40) is formed of a plate material interposed between the cathode
flow path (38) and the membrane electrode assembly (8) and having a plurality of through
holes.
Examples
[0061] Hereinafter, examples of the present invention will be described, but these examples
are merely examples for suitably describing the present invention, and do not limit
the present invention at all.
(Example 1)
[0062] An organic hydride production apparatus was prepared in which the support member
formed of the coil was disposed in the cathode flow path (both the supply flow path
and the collection flow path). A catholyte having a toluene concentration of 100%
was circulated through the cathode electrode of the organic hydride production apparatus.
In addition, an aqueous sulfuric acid solution was circulated as an anolyte to the
anode electrode. Then, an electrolytic reaction was performed at a current density
of 0.6 A/cm
2. The electrolytic reaction was performed until the Faraday efficiency converted from
the production amount of by-product hydrogen reached 95%. When hydrogen in an amount
corresponding to the Faraday efficiency of 95% was generated, the catholyte was collected
at the inlet of the cathode flow path, and the toluene concentration of the catholyte
was measured using a gas chromatograph.
[0063] For the cases where current densities was 0.4 A/cm
2 and 0.2 A/cm
2, the electrolytic reaction was performed in the similar manner, and the toluene concentration
of the catholyte at the Faraday efficiency of 95% was measured. The results are shown
in Fig. 5. The toluene concentration corresponds to the electrolytic performance at
the initial stage of use of the organic hydride production apparatus. This means that
the electrolysis performance is higher when the toluene concentration is lower.
[0064] Subsequently, a catholyte having a toluene concentration of 18% was supplied to the
organic hydride production apparatus of Example 1, and the daily start and stop (DSS)
operation was performed at a current density of 0.6 A/cm
2 for 4 weeks. In the DSS operation, the operation for 6 hours and the stop for 18
hours were alternately repeated. During the DSS operation, the toluene concentration
was maintained at 18% by replenishing the catholyte with toluene and discharging the
catholyte. After completion of the DSS operation, the electrolytic reaction was performed
at the current density of 0.6 A/cm
2, and the toluene concentration of the catholyte at the Faraday efficiency of 95%
was measured. The results are shown in Fig. 5.
(Comparative Example 1)
[0065] An organic hydride production apparatus having the same configuration as Example
1 except that no support member was provided was prepared. Then, the electrolytic
reaction was performed under the same conditions as Example 1, and the toluene concentration
of the catholyte at the Faraday efficiency of 95% at the initial stage of use of the
organic hydride production apparatus was measured. The results are shown in Fig. 5.
In addition, the DSS operation was performed under the same conditions as Example
1 except that the period was set to three weeks. After completion of the DSS operation,
the electrolytic reaction was performed at the current density of 0.6 A/cm
2, and the toluene concentration of the catholyte at the Faraday efficiency of 95%
was measured. The results are shown in Fig. 5.
[0066] Fig. 5 is a diagram showing a relation between a current density and a toluene concentration
at Faraday efficiency (F efficiency) of 95% in the organic hydride production apparatuses
of Example 1 and Comparative Example 1. As shown in Fig. 5, there was little difference
in initial electrolytic performance between Example 1 and Comparative Example 1. For
example, the toluene concentration at the current density of 0.6 A/cm
2 was 12.2% in Example 1 and 13.6% in Comparative Example 1. On the other hand, after
the DSS operation was performed, the toluene concentration of Comparative Example
1 was 49.5%, and the toluene concentration of Example 1 was 12.5%. In Example 1, although
the DSS operation was longer by one week than that in Comparative Example 1, the initial
electrolytic performance was substantially maintained. From the above results, it
was confirmed that the stability of the electrolytic performance of the organic hydride
production apparatus can be improved by suppressing the fitting of the membrane electrode
assembly into the cathode flow path by the support member.
INDUSTRIAL APPLICABILITY
[0067] The present invention can be used in an organic hydride production apparatus.
REFERENCE SIGNS LIST
[0068] 2 organic hydride production apparatus, 8 membrane electrode assembly, 10 anode electrode,
12 cathode electrode, 14 membrane, 38 cathode flow path, 38a supply flow path, 38b
collection flow path, 40 support member, 42b plate member