U.S. patent application number 16/686369 was filed with the patent office on 2020-03-12 for organic hydride production device.
This patent application is currently assigned to National University Corporation YOKOHAMA National University. The applicant listed for this patent is DE NORA PERMELEC LTD, National University Corporation YOKOHAMA National University. Invention is credited to Akihiro KATO, Koji MATSUOKA, Shigenori MITSUSHIMA, Kensaku NAGASAWA, Yoshinori NISHIKI, Setsuro OGATA, Yasushi SATO, Awaludin ZAENAL.
Application Number | 20200080212 16/686369 |
Document ID | / |
Family ID | 64396748 |
Filed Date | 2020-03-12 |
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United States Patent
Application |
20200080212 |
Kind Code |
A1 |
MITSUSHIMA; Shigenori ; et
al. |
March 12, 2020 |
ORGANIC HYDRIDE PRODUCTION DEVICE
Abstract
An organic hydride production apparatus includes: an electrolyte
membrane having proton conductivity; a cathode, provided on one
side of the electrolyte membrane, that contains a cathode catalyst
used to hydrogenate a hydrogenation target substance using protons
to produce an organic hydride; an anode, provided opposite to the
one side of the electrolyte membrane, that contains an anode
catalyst used to oxidize water to produce protons; and an anode
support, provided opposite to the electrolyte membrane side of the
anode, that supports the anode. The anode support is formed of an
elastic porous body of which the Young's modulus is greater than
0.1 N/mm.sup.2 and less than 43 N/mm.sup.2.
Inventors: |
MITSUSHIMA; Shigenori;
(Yokohama-shi, JP) ; NAGASAWA; Kensaku;
(Yokohama-shi, JP) ; NISHIKI; Yoshinori;
(Fujisawa-shi, JP) ; OGATA; Setsuro;
(Fujisawa-shi, JP) ; KATO; Akihiro; (Fujisawa-shi,
JP) ; ZAENAL; Awaludin; (Fujisawa-shi, JP) ;
MATSUOKA; Koji; (Tokyo, JP) ; SATO; Yasushi;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
National University Corporation YOKOHAMA National University
DE NORA PERMELEC LTD |
Yokohama-shi
Fujisawa-shi |
|
JP
JP |
|
|
Assignee: |
National University Corporation
YOKOHAMA National University
Yokohama-shi
JP
DE NORA PERMELEC LTD
Fujisawa-shi
JP
|
Family ID: |
64396748 |
Appl. No.: |
16/686369 |
Filed: |
November 18, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2018/014110 |
Apr 2, 2018 |
|
|
|
16686369 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25B 9/02 20130101; C25B
11/03 20130101; C25B 3/04 20130101; C25B 9/00 20130101 |
International
Class: |
C25B 11/03 20060101
C25B011/03; C25B 3/04 20060101 C25B003/04; C25B 9/02 20060101
C25B009/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 23, 2017 |
JP |
2017-101419 |
Claims
1. An organic hydride production apparatus, comprising: an
electrolyte membrane having proton conductivity; a cathode,
provided on one side of the electrolyte membrane, that contains a
cathode catalyst used to hydrogenate a hydrogenation target
substance using protons to produce an organic hydride; an anode,
provided opposite to the one side of the electrolyte membrane, that
contains an anode catalyst used to oxidize water to produce
protons; and an anode support, provided opposite to the electrolyte
membrane side of the anode, that supports the anode, wherein the
anode support is formed of an elastic porous body of which the
Young's modulus is 0.2 N/mm.sup.2 or greater and less than 43
N/mm.sup.2.
2. The organic hydride production apparatus of claim 1, wherein the
Young's modulus of the anode support is in the range from 0.3
N/mm.sup.2 to 10 N/mm.sup.2 inclusive.
3. The organic hydride production apparatus of claim 1, wherein a
ratio T1/T2 of a thickness T1 of the electrolyte membrane to a
thickness T2 of the anode is 0.35 or greater.
4. The organic hydride production apparatus of claim 1, wherein:
the anode comprises the anode catalyst, and a base material of a
mesh type that supports the anode catalyst; and the shape of the
mesh in the base material is a rhombic shape, and an average value
of short way of mesh SW and long way of mesh LW of the rhombic
shape is in the range from 0.3 mm to 3 mm inclusive.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2017-101419, filed on May 23, 2017, and International Patent
Application No. PCT/JP2018/014110, filed on Apr. 2, 2018, the
entire content of each of which is incorporated herein by
reference.
BACKGROUND
Field of the Invention
[0002] The present invention relates to an organic hydride
production apparatus. The present invention particularly relates to
an organic hydride production apparatus for producing an organic
hydride by electrochemically hydrogenating a hydrogenation target
substance.
Description of the Related Art
[0003] In recent years, widespread use of renewable energy,
obtained by solar power generation, wind power generation,
hydropower generation, geothermal power generation, and the like,
is desired because the renewable energy is considered as new energy
that can be generated with less carbon dioxide emissions, compared
to energy obtained by thermal power generation. However, for such
renewable energy, moderation of output fluctuations, especially the
intermediate and long-period output fluctuations, is required.
Also, large-scale transportation of renewable energy is relatively
difficult. Meanwhile, electric power obtained from renewable energy
can be effectively converted into chemical energy. For processes
for directly converting electric power into chemical energy,
electrochemical systems can be used. Secondary cells, or storage
batteries, are examples of electrochemical systems and are devices
widely used to convert electric power into chemical energy and
store the chemical energy.
[0004] As an electrochemical system based on renewable energy,
there is a promising system in which large-scale solar power or
wind power generation systems are installed in appropriate
locations around the world, and renewable energy obtained therefrom
is converted into an energy carrier appropriate for transportation,
so as to be transported into a country and consumed domestically.
The energy carrier may be liquid hydrogen, for example. However,
since hydrogen is gaseous at ordinary temperatures and pressures,
special tankers are required for transportation and storage
thereof.
[0005] In such a situation, attention is given to organic hydrides
(organic chemical hydrides) as energy carriers alternative to
liquid hydrogen. Organic hydrides may be cyclic organic compounds,
such as cyclohexane, methylcyclohexane, and decalin. Organic
hydrides are generally liquid at ordinary temperatures and
pressures, and hence can be easily handled. Also, organic hydrides
can be electrochemically hydrogenated and dehydrogenated.
Accordingly, when an organic hydride is used as an energy carrier,
it can be transported and stored more easily than liquid hydrogen.
Particularly, when a liquid organic hydride having properties
similar to those of petroleum is selected, since it has excellent
compatibility with relatively large-scale energy supply systems,
the liquid organic hydride has the advantage of being easily
distributed to ends of such energy supply systems.
[0006] As a method for producing an organic hydride, a method is
conventionally known in which hydrogen is produced by water
electrolysis using renewable energy and is added to a hydrogenation
target substance (dehydrogenated product of an organic hydride) in
a hydrogenation reactor, thereby producing an organic hydride.
[0007] Meanwhile, when an electrolytic synthesis method is used,
since hydrogen can be directly added to a hydrogenation target
substance, the processes for organic hydride production can be
simplified. In addition, the efficiency loss is small regardless of
the production scale, and excellent responsiveness to the start and
stop operations of the organic hydride production apparatus can be
seen. With regard to a technology for such organic hydride
production, for example, Patent Document 1 discloses an organic
hydride production apparatus that includes an anode for producing
protons from water, and a cathode for hydrogenating an organic
compound having an unsaturated bond. [0008] Patent Literature 1: WO
2012/091128
[0009] As a result of intensive study regarding the abovementioned
technology for organic hydride production, the inventors have found
that there is room for improving the efficiency of organic hydride
production in the conventional technologies.
SUMMARY OF THE INVENTION
[0010] The present invention has been made in view of such a
situation, and a purpose thereof is to provide a technology for
improving efficiency of organic hydride production.
[0011] One aspect of the present invention is an organic hydride
production apparatus. The organic hydride production apparatus
includes: an electrolyte membrane having proton conductivity; a
cathode, provided on one side of the electrolyte membrane, that
contains a cathode catalyst used to hydrogenate a hydrogenation
target substance using protons to produce an organic hydride; an
anode, provided opposite to the one side of the electrolyte
membrane, that contains an anode catalyst used to oxidize water to
produce protons; and an anode support, provided opposite to the
electrolyte membrane side of the anode, that supports the anode.
The anode support is formed of an elastic porous body of which the
Young's modulus is greater than 0.1 N/mm.sup.2 and less than 43
N/mm.sup.2.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Embodiments will now be described, by way of example only,
with reference to the accompanying drawings which are meant to be
exemplary, not limiting, and wherein like elements are numbered
alike in several Figures, in which:
[0013] FIG. 1 is a sectional view that shows a schematic structure
of an organic hydride production apparatus according to an
embodiment;
[0014] FIG. 2A shows an anode support and a cell voltage in an
organic hydride production apparatus according to each of Test
Examples 1-11; FIG. 2B is a diagram used to describe long way of
mesh LW, short way of mesh SW, and a strand width ST; FIG. 2C shows
relationships between the Young's modulus of the anode support and
the cell voltage;
[0015] FIG. 3A shows thicknesses of an electrolyte membrane and an
anode included in the organic hydride production apparatus
according to each of Test Examples 2 and 12-14, a ratio of the
thicknesses, and a cell voltage; FIG. 3B shows relationships
between the ratio of the thicknesses and the cell voltage;
[0016] FIG. 4A shows mesh dimensions of the anode and a cell
voltage in the organic hydride production apparatus according to
each of Test Examples 15-19; and FIG. 4B shows relationships
between an average value of the long way of mesh LW and the short
way of mesh SW, and the cell voltage.
DETAILED DESCRIPTION OF THE INVENTION
[0017] In the following, the present invention will be described
based on a preferred embodiment with reference to the drawings.
Embodiments of the invention are provided for purposes of
illustration and not limitation, and it should be understood that
not all of the features or combinations thereof described in the
embodiments are necessarily essential to the invention.
[0018] Like reference characters denote like or corresponding
constituting elements, members, and processes in each drawing, and
repetitive description will be omitted as appropriate. Also, the
scale or shape of each component shown in each drawing is set for
the sake of convenience to facilitate the explanation and is not to
be regarded as limitative unless otherwise specified. Further, when
the terms "first", "second", and the likes are used in the present
specification or claims, such terms do not imply any order or
importance and are used to distinguish one configuration from
another, unless otherwise specified.
[0019] FIG. 1 is a sectional view that shows a schematic structure
of an organic hydride production apparatus according to an
embodiment. An organic hydride production apparatus 100 is an
electrolysis cell for hydrogenating a hydrogenation target
substance, which is a dehydrogenated product of an organic hydride,
by an electrochemical reduction reaction, and the organic hydride
production apparatus 100 mainly includes an electrolyte membrane
102, a cathode 104, a cathode chamber 106, an anode 108, an anode
support 110, an anode chamber 112, and a pair of separators 114a
and 114b. The electrolyte membrane 102, cathode 104, and anode 108
constitute a membrane electrode assembly.
[0020] The electrolyte membrane 102 is formed of a
proton-conducting material (an ionomer). The electrolyte membrane
102 selectively conducts protons while restraining mixture and
diffusion of substances between the cathode 104 and the anode 108.
The proton-conducting material may be a perfluorosulfonic acid
polymer, such as Nafion (registered trademark) and Flemion
(registered trademark). The thickness of the electrolyte membrane
102 is not particularly limited, but may preferably be 5-300 .mu.m,
more preferably be 10-150 .mu.m, and further preferably be 20-100
.mu.m. By setting the thickness of the electrolyte membrane 102 to
5 .mu.m or greater, the barrier performance of the electrolyte
membrane 102 can be ensured, so that cross leakage of the
hydrogenation target substance, organic hydride, oxygen, and the
like can be restrained more certainly. Also, setting the thickness
of the electrolyte membrane 102 to 300 .mu.m or less can prevent
excessive increase of ion transfer resistance.
[0021] The electrolyte membrane 102 may be mixed with a
reinforcement material, such as porous polytetrafluoroethylene
(PTFE). Adding a reinforcement material can restrain deterioration
of dimension stability of the electrolyte membrane 102.
Accordingly, durability of the electrolyte membrane 102 can be
improved. Also, crossover of the hydrogenation target substance,
organic hydride, oxygen, and the like can be restrained. A surface
of the electrolyte membrane 102 may be made hydrophilic by coating
the surface with a predetermined inorganic layer, for example.
[0022] The cathode 104 is provided on one side of the electrolyte
membrane 102. In the present embodiment, the cathode 104 is
provided to be in contact with one main surface of the electrolyte
membrane 102. The cathode 104 has a structure in which a cathode
catalyst layer 116, a microporous layer 118, and a diffusion layer
120 are laminated in this order. More specifically, the cathode
catalyst layer 116 is in contact with the one main surface of the
electrolyte membrane 102. The microporous layer 118 is in contact
with a main surface of the cathode catalyst layer 116 opposite to
the electrolyte membrane 102 side. The diffusion layer 120 is in
contact with a main surface of the microporous layer 118 opposite
to the cathode catalyst layer 116 side. The microporous layer 118
and the diffusion layer 120 may be omitted as appropriate.
[0023] The cathode catalyst layer 116 contains a cathode catalyst
(reduction catalyst) used to hydrogenate a hydrogenation target
substance using protons to produce an organic hydride. As the
cathode catalyst, metal particles of a substance selected from a
group including Pt, Ru, Pd, Ir, and an alloy containing at least
one of them may be used. The cathode catalyst may be a commercially
available product, or may be synthesized according to a
publicly-known method. Also, the cathode catalyst may be
constituted by a metal composition that contains a first catalyst
metal (noble metal) including at least one of Pt, Ru, Pd, and Ir,
and one or more kinds of second catalyst metals selected from among
Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Sn, W, Re, Pb, and Bi. In this
case, the form of the metal composition may be an alloy of the
first catalyst metal and the second catalyst metal(s), or an
intermetallic compound constituted by the first catalyst metal and
the second catalyst metal(s), for example.
[0024] The cathode catalyst is supported by a catalyst support made
of an electron-conductive material. When the cathode catalyst is
supported by a catalyst support, the surface area of the cathode
catalyst layer 116 can be increased. Also, cohesion of the cathode
catalyst can be restrained. For the catalyst support, an
electron-conductive material containing, as a major component, one
of porous carbon (such as mesoporous carbon), porous metal, and a
porous metal oxide may be used, for example.
[0025] The porous carbon may be carbon black, for example,
including Ketjenblack (registered trademark), acetylene black,
furnace black, and Vulcan (registered trademark). The average
particle size of carbon particulates, such as carbon black, may
preferably be 0.01-1 .mu.m. The porous metal may be Pt black, Pd
black, or Pt metal deposited in a fractal form, for example. The
porous metal oxide may be an oxide of Ti, Zr, Nb, Mo, Hf, Ta, or W,
for example. Also, for the catalyst support, a porous metal
compound, such as a nitride, a carbide, an oxynitride, a
carbonitride, or a partially-oxidized carbonitride of metal, such
as Ti, Zr, Nb, Mo, Hf, Ta, and W, may also be used.
[0026] The catalyst support supporting the cathode catalyst is
coated with an ionomer. Accordingly, the ion conductivity of the
cathode 104 can be improved. The ionomer may be a perfluorosulfonic
acid polymer, for example, including Nafion (registered trademark)
and Flemion (registered trademark). Preferably, the cathode
catalyst may be partially coated with the ionomer included in the
cathode catalyst layer 116. This enables efficient supply of three
elements (a hydrogenation target substance, protons, and electrons)
necessary for the electrochemical reaction in the cathode catalyst
layer 116, to a reaction field.
[0027] The thickness of the cathode catalyst layer 116 may
preferably be 1-100 .mu.m, and more preferably be 5-30 .mu.m. If
the thickness of the cathode catalyst layer 116 is increased, the
proton transfer resistance will be increased, and, in addition, the
diffusivity of the hydrogenation target substance or organic
hydride will be reduced. Therefore, adjusting the thickness of the
cathode catalyst layer 116 within the abovementioned range would be
desirable.
[0028] The diffusion layer 120 has a function to evenly diffuse, in
the cathode catalyst layer 116, the hydrogenation target substance
in a liquid state supplied from the outside. A constituent material
of the diffusion layer 120 may preferably have high compatibility
with the hydrogenation target substance and organic hydride. The
constituent material of the diffusion layer 120 may be a porous
conductive base material or a fiber sintered body, for example.
Porous conductive base materials and fiber sintered bodies are
preferable because they have porosity suitable for supply and
removal of gas and liquid and are capable of maintaining sufficient
conductivity. The thickness of the diffusion layer 120 may
preferably be 10-5000 .mu.m.
[0029] More specific examples of the constituent material of the
diffusion layer 120 include carbon woven fabric (carbon cloth),
carbon non-woven fabric, and carbon paper. Carbon cloth is woven
fabric made with bundles of hundreds of thin carbon fibers of which
the diameter is a few micrometers. Also, carbon paper is obtained
by making a thin film precursor from carbon material fiber using a
papermaking method and then sintering the thin film precursor.
[0030] The microporous layer 118 has a function to promote
diffusion of the hydrogenation target substance and organic hydride
in liquid states in a surface direction of the cathode catalyst
layer 116. The microporous layer 118 may be formed by applying, to
a surface of the diffusion layer 120, paste-like kneaded matter
obtained by mixing and kneading conductive powder and a water
repellent, and then drying the kneaded matter, for example. As the
conductive powder, conductive carbon such as Vulcan (registered
trademark) may be used, for example. As the water repellent,
fluororesin such as polytetrafluoroethylene (PTFE) resin may be
used, for example. The ratio between the conductive powder and
water repellent may be appropriately determined within a range such
that desired conductivity and water repellency can be obtained. As
with the diffusion layer 120, the microporous layer 118 may also be
formed of carbon cloth, carbon paper, or the like.
[0031] The thickness of the microporous layer 118 may preferably be
1-50 .mu.m. When the microporous layer 118 is formed such as to be
recessed inward from the surface of the diffusion layer 120, an
average thickness of the microporous layer 118, including the
recessed portion in the diffusion layer 120, is defined as the
thickness of the microporous layer 118. A metal component may be
coexistent on a surface of the microporous layer 118. This can
improve the electron conductivity of the microporous layer 118 and
make the current uniform.
[0032] The microporous layer 118 and the diffusion layer 120 are
used in a state where pressure is applied thereto in the respective
thickness directions. Accordingly, it will be unfavorable if such
pressurization in the thickness directions during use changes the
conductivity in the thickness directions. Therefore, the
microporous layer 118 and the diffusion layer 120 may preferably be
subjected to press working in advance. This can improve and
stabilize the conductivity in a thickness direction in each layer.
Further, improving the degree of bonding between the cathode
catalyst layer 116 and the microporous layer 118 also contributes
to improvement of the conductivity of the cathode 104. Such
improvement of the degree of bonding also improves the capability
of supplying a raw material and the capability of removing a
product.
[0033] The cathode chamber 106 is a space for housing the cathode
104. The cathode chamber 106 is defined by the electrolyte membrane
102, the separator 114a, and a spacer 122 of a frame shape disposed
between the electrolyte membrane 102 and the separator 114a. The
cathode chamber 106 also houses a flow passage part 124, besides
the cathode 104.
[0034] The flow passage part 124 is disposed adjacent to the
diffusion layer 120. More specifically, the flow passage part 124
is provided to be in contact with a main surface of the diffusion
layer 120 opposite to the microporous layer 118 side. Accordingly,
the flow passage part 124 is disposed between the diffusion layer
120 and the separator 114a. The flow passage part 124 has a
structure in which grooves 124b are provided on a main surface of a
body part 124a of a plate shape. The grooves 124b constitute a flow
passage for the hydrogenation target substance. The body part 124a
is made of a conductive material. The flow passage part 124 also
functions as a cathode support for positioning the cathode 104
within the cathode chamber 106. The flow passage part 124 receives
pressing force from the anode support 110, which will be described
later, and ensures electron conductivity between the separator 114a
and the cathode 104.
[0035] The spacer 122 also serves as a seal material that prevents
leakage of an organic substance including the hydrogenation target
substance and a hydride to the outside of the cathode chamber 106,
and the spacer 122 may preferably have electronic insulation
properties. The constituent material of the spacer 122 may be
polytetrafluoroethylene resin, for example. In the spacer 122, a
cathode chamber inlet 126 and a cathode chamber outlet 128, which
each communicate with the inside and the outside of the cathode
chamber 106, are disposed.
[0036] The cathode chamber inlet 126 is disposed below the cathode
chamber 106 in the vertical direction. One end of the cathode
chamber inlet 126 is connected to the flow passage of the flow
passage part 124, and the other end thereof is connected to a
catholyte storage tank (not illustrated). Between the cathode
chamber inlet 126 and the catholyte storage tank, a catholyte
supply device (not illustrated) constituted by each of various
pumps, such as a gear pump and a cylinder pump, a gravity flow type
device, or the like is provided.
[0037] The catholyte storage tank stores a hydrogenation target
substance to be hydrogenated by an electrochemical reduction
reaction in the organic hydride production apparatus 100. The
organic hydride used in the present embodiment is not particularly
limited, as long as it is an organic compound that can be
hydrogenated or dehydrogenated by a reversible hydrogenation or
dehydrogenation reaction. Accordingly, acetone-isopropanol-based
organic hydrides, benzoquinone-hydroquinone-based organic hydrides,
aromatic hydrocarbon-based organic hydrides, and the likes may be
widely used. Among them, aromatic hydrocarbon-based organic
hydrides, represented by toluene-methylcyclohexane-based organic
hydrides, may be preferable, in terms of transportability during
the energy transportation, toxicity, safety, and storage stability,
and also in terms of the transportable amount of hydrogen per
volume or mass, ease of hydrogenation and dehydrogenation
reactions, and energy conversion efficiency, including the feature
by which the Gibbs free energy does not change significantly.
[0038] An aromatic hydrocarbon compound used as a hydrogenation
target substance, i.e., a dehydrogenated product of an organic
hydride, is a compound that contains at least one aromatic ring,
such as benzene, an alkylbenzene, naphthalene, an alkylnaphthalene,
anthracene, and diphenylethane. Alkylbenzenes include compounds in
which each of one through four hydrogen atoms in an aromatic ring
is replaced by a linear or branched alkyl group having one through
six carbon atoms, such as toluene, xylene, mesitylene,
ethylbenzene, and diethylbenzene. Alkylnaphthalenes include
compounds in which each of one through four hydrogen atoms in an
aromatic ring is replaced by a linear or branched alkyl group
having one through six carbon atoms, such as methylnaphthalene.
Each of the compounds may be used solely or in combination.
[0039] The hydrogenation target substance may preferably be at
least one of toluene and benzene. As the hydrogenation target
substance, a nitrogen-containing heterocyclic aromatic compound,
such as pyridine, pyrimidine, pyrazine, quinoline, isoquinoline, an
N-alkylpyrrole, an N-alkylindole, and N-alkyldibenzopyrrole, may
also be used. The organic hydride is obtained by hydrogenating the
hydrogenation target substance as set forth above and may be
methylcyclohexane, dimethylcyclohexane, or piperidine, for
example.
[0040] The hydrogenation target substance may preferably be liquid
at ordinary temperatures. When a mixture of a plurality of aromatic
hydrocarbon compounds as set forth above, a mixture of a plurality
of nitrogen-containing heterocyclic aromatic compounds as set forth
above, or a mixture of the both compounds is used, such a mixture
may suitably be liquid. When the hydrogenation target substance is
liquid at ordinary temperatures, such a hydrogenation target
substance in the liquid state can be supplied to the organic
hydride production apparatus 100, without performing a heating or
pressurization process thereon. In the following, the liquid stored
in the catholyte storage tank may be referred to as a "catholyte",
as needed. The catholyte stored in the catholyte storage tank is
supplied to the cathode chamber 106 by the catholyte supply
device.
[0041] The catholyte supplied to the cathode chamber 106 is
introduced into the cathode chamber 106 through the cathode chamber
inlet 126. The catholyte introduced into the cathode chamber 106 is
supplied to the cathode catalyst layer 116 via the grooves 124b of
the flow passage part 124, the diffusion layer 120, and the
microporous layer 118.
[0042] The cathode chamber outlet 128 is disposed above the cathode
chamber 106 in the vertical direction. One end of the cathode
chamber outlet 128 is connected to the flow passage of the flow
passage part 124, and the other end thereof is connected to the
catholyte storage tank, for example. The organic hydride, i.e., the
hydrogenation target substance hydrogenated in the organic hydride
production apparatus 100, and the unreacted hydrogenation target
substance within the cathode chamber 106 are discharged outside the
cathode chamber 106 through the cathode chamber outlet 128. Between
the cathode chamber outlet 128 and the catholyte storage tank, a
separation tank (not illustrated) is provided. In the separation
tank, hydrogen gas as a by-product, an anolyte flowing into the
cathode 104 side via the electrolyte membrane 102, or the like is
separated from the mixture of the organic hydride and the
hydrogenation target substance. The separated anolyte is reused.
The organic hydride and the hydrogenation target substance are then
returned into the catholyte storage tank.
[0043] The separator 114a is disposed on the cathode chamber 106
side. In the present embodiment, the separator 114a is laminated to
a main surface of the flow passage part 124 opposite to the
diffusion layer 120 side. The separator 114a has electron
conductivity and also functions as a power feeding plate. The
constituent material of the separator 114a may be a metal, such as
SUS and Ti.
[0044] The anode 108 is provided opposite to the one side of the
electrolyte membrane 102, i.e., opposite to the cathode 104. In the
present embodiment, the anode 108 is provided to be in contact with
the other main surface of the electrolyte membrane 102. The anode
108 contains an anode catalyst 108a used to oxidize water in the
anolyte to produce protons. As the anode catalyst 108a, metal
particles of a substance selected from a group including Ru, Rh,
Pd, Ir, Pt, and an alloy containing at least one of them may be
used. Also, since the anode catalyst 108a generates oxygen while
being immersed in an acid electrolyte, a platinum metal oxide-based
catalyst may be preferably used therefor. Particularly, iridium
oxide-based catalysts have less voltage loss and excellent
durability. Furthermore, an iridium oxide-based catalyst that
forms, with tantalum oxide, a solid solution exhibits a smaller
increase of voltage loss in a system into which an organic
substance is mixed, so that such an iridium oxide-based catalyst
may be preferable as the anode catalyst 108a.
[0045] The anode 108 includes, besides the anode catalyst 108a, a
base material 108b for supporting the anode catalyst 108a. The base
material 108b has electrical conductivity sufficient to conduct
current required for electrolysis. Also, the base material 108b may
preferably have excellent corrosion resistance to the anolyte. The
base material 108b may be made of metal, such as Ti, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Zr, Nb, Mo, Ta, and W, or an alloy composed
primarily of such metal. More preferably, the base material 108b
may contain 20 parts by mass or more of at least one metal selected
from a group including Ti, Zr, Nb, and Ta.
[0046] The thickness of the base material 108b may preferably be in
the range from 0.05 mm to 1 mm inclusive. The thickness of the
anode 108 is substantially identical with the thickness of the base
material 108b. Also, a ratio T1/T2 of a thickness T1 of the
electrolyte membrane 102 to a thickness T2 of the anode 108 may
preferably be 0.35 or greater, more preferably be 0.6 or greater,
and further preferably be 1 or greater. Setting the ratio T1/T2 to
0.35 or greater can restrain curving of the electrolyte membrane
102, thereby also restraining peeling off of the cathode 104 and
the electrolyte membrane 102. Accordingly, the cell voltage
required to drive the organic hydride production apparatus 100 can
be reduced more certainly.
[0047] The anode 108 is a gas-evolving electrode. Accordingly, in
order to promote the supply of the anolyte to the anode 108 without
increase of resistance caused by bubbles, the base material 108b
may preferably be a porous body. The base material 108b of the
present embodiment is a plate-like body of a mesh type. For
example, the base material 108b may be formed of an expanded mesh.
The shape of the mesh of the base material 108b is a rhombic shape,
and an average value of the short way of mesh SW (see FIG. 2B) and
the long way of mesh LW (see FIG. 2B) of the rhombic shape may
preferably be in the range from 0.3 mm to 3 mm inclusive, more
preferably be greater than 0.3 mm and equal to or less than 3 mm,
and further preferably be in the range from 1.0 mm to 1.5 mm
inclusive. A long way direction is a direction of a slit in the
manufacture of the expanded mesh, and a short way direction is a
direction perpendicular to the slit. The expanded mesh may
desirably be subjected to a smoothing process after the mesh
work.
[0048] By setting the average value of SW and LW to 3 mm or less,
the pressure applied by the anode support 110 to the anode 108 when
the organic hydride production apparatus 100 is fitted can be
provided to the electrolyte membrane 102 side more evenly. Also,
the curving of the electrolyte membrane 102 can be restrained more
certainly. Accordingly, the cell voltage required to drive the
organic hydride production apparatus 100 can be reduced more
certainly. Also, setting the average value of SW and LW to 0.3 mm
or greater can further restrain inhibition of infiltration of the
anolyte into the anode 108, caused by oxygen generated at the anode
108. Accordingly, increase in cell voltage can be restrained more
certainly.
[0049] The aperture rate of the base material 108b may be defined
by the opening area per projected area of the base material 108b
and may be in the range from 40% to 90% inclusive, for example. By
setting the aperture rate to 40% or greater, oxygen bubbles
generated at the anode 108 can be removed more rapidly.
Accordingly, increase in cell resistance (in other words, increase
in cell voltage) due to so-called bubble effect can be restrained.
Also, setting the aperture rate to 90% or less can prevent
excessive decrease of active electrode area.
[0050] The size of the apertures in the base material 108b or the
pitch between the apertures may preferably be the thickness of the
electrolyte membrane 102 or less. Accordingly, a situation can be
prevented in which the electrolyte membrane 102 is distorted and
then stuck into an aperture of the anode 108. As a result, contact
between the electrolyte membrane 102 and the cathode 104 can be
maintained, so that increase in cell voltage can be restrained.
[0051] Besides the expanded mesh, other planar members having
apertures may be appropriately selected for the base material 108b.
For example, part of a metal plate may be punched or smelted, and
the resulting plate provided with round or square apertures can be
used. When a round-hole punched plate is used for the base material
108b, the base material 108b of one embodiment may have a thickness
of 0.5 mm or less, a hole diameter in the range from 0.1 mm to 0.3
mm inclusive, and a hole pitch in the range from 0.2 mm to 5 mm
inclusive.
[0052] Alternatively, the base material 108b may be formed of a
fabric mesh made of metal fiber. In this case, the fiber diameter
of the metal fiber may be 0.2 mm or less, and the mesh pitch may be
0.5 mm or less, for example. Further, the base material 108b may be
formed of a sintered metal porous body, a foam molded body, or a
powder molded body, for example. The metal porous body may be
continuous fiber or chatter fiber containing micropores, for
example. When the base material 108b is formed of a fabric mesh, a
sintered body, or the like, the porosity of the base material 108b
may be in the range from 40% to 90% inclusive, for example. The
"porosity" in the present specification means proportion of the
volume of the pores to the total volume, i.e., volume porosity. The
volume porosity can be calculated based on a cross-sectional image
obtained using a scanning electron microscope, a metallographic
microscope, or the like.
[0053] On a surface of the base material 108b, a conductive film
made of a valve metal, such as tantalum, an alloy containing a
valve metal, a noble metal, or a noble metal oxide may be provided,
for example. This can restrain the formation of an insulating oxide
film on a surface of the base material 108b, caused by contact
between the anode 108 and the anolyte. Therefore, the conductivity
between the anode catalyst 108a and the base material 108b can be
favorably maintained.
[0054] The anode 108 may preferably have larger Young's modulus
than the anode support 110. More preferably, the Young's modulus of
the anode 108 may be in the range from 2 N/mm.sup.2 to 40
N/mm.sup.2 inclusive.
[0055] The anode support 110 is provided opposite to the
electrolyte membrane 102 side of the anode 108 and supports the
anode 108. In present embodiment, the anode support 110 is provided
to be in contact with a main surface of the anode 108 opposite to
the electrolyte membrane 102 side. The anode 108 is pressed onto
the electrolyte membrane 102 by the anode support 110. The anode
support 110 is formed of an elastic porous body of a plate shape.
Since the anode support 110 is a porous body, the anolyte can be
supplied to the anode 108.
[0056] The anode support 110 may preferably be made of a material
having excellent corrosion resistance to the anolyte, such as Ti,
Zr, Nb, and Ta, or an alloy composed primarily of such metal. More
preferably, the anode support 110 may contain 20 parts by mass or
more of at least one metal selected from a group including Ti, Zr,
Nb, and Ta. On a surface of the anode support 110, anti-corrosion
treatment against the anolyte may be performed, similarly to the
base material 108b.
[0057] The anode support 110 has electron conductivity and also
functions as a current collector plate. The thickness of the anode
support 110 may be in the range from 0.5 mm to 5 mm inclusive, for
example. Also, the porosity of the anode support 110 may be in the
range from 40% to 95% inclusive, for example.
[0058] The Young's modulus of the anode support 110 is greater than
0.1 N/mm.sup.2 and less than 43 N/mm.sup.2. The lower limit of the
Young's modulus of the anode support 110 may preferably be 0.2
N/mm.sup.2 or greater, and more preferably be 0.3 N/mm.sup.2 or
greater. The upper limit of the Young's modulus of the anode
support 110 may preferably be 40 N/mm.sup.2 or less, more
preferably be 10 N/mm.sup.2 or less, and further preferably be 7
N/mm.sup.2 or less. The Young's modulus can be calculated by the
following method. First, a support specimen cut out in an
appropriate area is sandwiched between two hard metal plates to
form a laminated body. To the laminated body, a load is applied
using a load cell. The initial thickness and the thickness during
the load application of the support specimen are measured using a
micrometer. Thereafter, the magnitude of the applied load is
divided by the area of the support specimen, and the obtained value
is further divided by the variation of the thickness, thereby
obtaining the Young's modulus.
[0059] By setting the Young's modulus of the anode support 110 to
greater than 0.1 N/mm.sup.2, the anode 108 can be pressed more
certainly. This can restrain peeling off of the cathode 104 and the
electrolyte membrane 102, thereby reducing the cell voltage in the
organic hydride production apparatus 100. When the Young's modulus
is 0.1 N/mm.sup.2 or less, the thickness of the anode support needs
to be remarkably increased in order to press the anode 108 at
desired pressure, which is not preferable.
[0060] Also, by setting the Young's modulus of the anode support
110 to less than 43 N/mm.sup.2, a situation can be prevented in
which the elasticity of the anode support 110 is excessively
reduced and pressure is unevenly applied to the anode 108. This can
restrain the occurrence of partial contact failure between the
anode 108 and the electrolyte membrane 102 or the anode support
110, thereby reducing the cell voltage in the organic hydride
production apparatus 100. Also, a situation can be avoided in which
the deformation amount of the anode support 110 is excessively
reduced and the assembly of the organic hydride production
apparatus 100 becomes difficult.
[0061] The constituent material of the anode support 110 may be a
sintered body of continuous fiber or chatter fiber containing
micropores, a foam molded body, or a powder molded body, for
example. The fiber included as the constituent material of the
anode support 110 may preferably have a fiber diameter in the range
from 10 .mu.m to 100 .mu.m inclusive, and a length in the range
from 1 mm to 100 mm inclusive. The weight per unit area of the
fiber used to form the anode support 110 may be in the range from
100 g/m.sup.2 to 5000 g/m.sup.2 inclusive, for example. Even with
the same dimensions and weight per unit area of the fiber, the
resistance value and the Young's modulus of the anode support 110
can be adjusted by adjusting the temperature and the time of the
heat treatment. A laminated web obtained by sintering fiber may
have an elastic deformation amount in the range from 0.2 mm to 2 mm
inclusive at a pressure of 0.1 MP, for example. The deformation
rate may be in the range from 20% to 80% inclusive, for example.
The anode support 110 may also be formed of a planar member having
multiple apertures, such as an expanded mesh. In other words, the
"porous body" in the subject application includes a planar member
provided with multiple apertures.
[0062] The anode chamber 112 is a space for housing the anode 108
and the anode support 110. The anode chamber 112 is defined by the
electrolyte membrane 102, the separator 114b, and a spacer 130 of a
frame shape disposed between the electrolyte membrane 102 and the
separator 114b.
[0063] The spacer 130 also serves as a seal material that prevents
leakage of the anolyte to the outside of the anode chamber 112, and
the spacer 130 may preferably have electronic insulation
properties. The constituent material of the spacer 130 may be
polytetrafluoroethylene resin, for example. In the spacer 130, an
anode chamber inlet 132 and an anode chamber outlet 134, which each
communicate with the inside and the outside of the anode chamber
112, are disposed.
[0064] The anode chamber inlet 132 is disposed below the anode
chamber 112 in the vertical direction. One end of the anode chamber
inlet 132 is connected to the anode support 110, and the other end
thereof is connected to an anolyte storage tank (not illustrated).
Between the anode chamber inlet 132 and the anolyte storage tank,
an anolyte supply device (not illustrated) constituted by each of
various pumps, such as a gear pump and a cylinder pump, a gravity
flow type device, or the like is provided.
[0065] The anolyte storage tank stores the anolyte. The anolyte may
be a sulfuric acid aqueous solution, nitric acid aqueous solution,
or hydrochloric acid aqueous solution having the ion conductivity
of 0.01 S/cm or greater measured at 20 degrees C., for example. By
setting the ion conductivity of the anolyte to 0.01 S/cm or
greater, industrially sufficient electrochemical reactions can be
induced. The anolyte stored in the anolyte storage tank is supplied
to the anode chamber 112 by the anolyte supply device. Pure water
may also be used as the anolyte. In this case, it may be preferable
to fix the anode catalyst 108a to the base material 108b using a
perfluorosulfonic acid polymer or the like such as to restrain
coming off of the anode catalyst 108a due to bubble generation.
[0066] The anolyte supplied to the anode chamber 112 is introduced
into the anode chamber 112 through the anode chamber inlet 132. The
anolyte introduced into the anode chamber 112 is supplied to the
anode 108 via the anode support 110.
[0067] The anode chamber outlet 134 is disposed above the anode
chamber 112 in the vertical direction. One end of the anode chamber
outlet 134 is connected to the anode support 110, and the other end
thereof is connected to the anolyte storage tank, for example. The
anolyte within the anode chamber 112 is discharged outside the
anode chamber 112 through the anode chamber outlet 134. Between the
anode chamber outlet 134 and the anolyte storage tank, a gas-liquid
separation unit (not illustrated) is provided. In the gas-liquid
separation unit, oxygen produced by electrolysis of the anolyte,
and gases, such as the gasified hydrogenation target substance and
organic hydride, mixed into the anolyte via the electrolyte
membrane 102 are separated from the anolyte. The unreacted anolyte
is returned into the anolyte storage tank.
[0068] The separator 114b is disposed on the anode chamber 112
side. In the present embodiment, the separator 114b is laminated to
a main surface of the anode support 110 opposite to the anode 108
side. The separator 114b has electron conductivity and also
functions as a power feeding plate. The constituent material of the
separator 114b may be a metal, such as SUS and Ti.
[0069] The organic hydride production apparatus 100 may be
assembled in the following way. First, the flow passage part 124,
the cathode 104, the electrolyte membrane 102, the anode 108, and
the anode support 110 are laminated in this order to obtain a
laminated body. Thereafter, the spacers 122 and 130 are fitted to
the laminated body, which is then sandwiched between the pair of
separators 114a and 114b. The pair of separators 114a and 114b
apply appropriate clamping pressure to the laminated body.
[0070] For example, to the laminated body, pressure of 1
kgf/cm.sup.2 or less is applied. Since the organic hydride
production apparatus 100 includes the anode support 110, the
electrical connecting condition in each layer can be favorably
maintained with the small pressure of 1 kgf/cm.sup.2 or less.
Accordingly, weight saving and cost reduction of the organic
hydride production apparatus 100 can be achieved. Also, even when
pressure fluctuation is caused during the operation of the organic
hydride production apparatus 100, the anode support 110 is
elastically deformed, so that a certain pressure can be always
applied to each layer. When the laminated body is prepared, the
anode 108 and the anode support 110 bonded in advance may be used.
Alternatively, the anode support 110 and the separator 114b bonded
in advance may be used. The organic hydride production apparatus
100 may be a bipolar electrolytic cell.
[0071] To the organic hydride production apparatus 100, an electric
power controller and a drive controller, which are not illustrated,
may be connected. The electric power controller may be a DC/DC
converter for converting an output voltage of an electric power
source into a predetermined voltage, for example. The positive
output terminal of the electric power controller is connected to
the anode 108. The negative output terminal of the electric power
controller is connected to the cathode 104. Accordingly, a
predetermined voltage is applied between the anode 108 and the
cathode 104.
[0072] In the electric power controller, a reference terminal may
be provided in order to detect the potentials of the positive and
negative electrodes. In this case, the input side of the reference
terminal is connected to a reference electrode (not illustrated)
provided in the electrolyte membrane 102. The reference electrode
is electrically isolated from the cathode 104 and the anode 108.
The reference electrode is maintained at a reference electrode
potential. The reference electrode potential may be a potential
with respect to a reversible hydrogen electrode (RHE), for example.
The reference electrode potential may also be a potential with
respect to an Ag/AgCl electrode. The current flowing between the
cathode 104 and the anode 108 is detected by a current detector
(not illustrated). The current value detected by the current
detector is input to the drive controller and used for control of
the electric power controller by the drive controller. The
potential difference between the reference electrode and the
cathode 104 is detected by a voltage detector (not illustrated).
The potential difference value detected by the voltage detector is
input to the drive controller and used for control of the electric
power controller by the drive controller.
[0073] The drive controller controls outputs at the positive output
terminal and the negative output terminal of the electric power
controller such that the potentials of the anode 108 and the
cathode 104 become desired potentials. The electric power source
may preferably be renewable energy obtained by solar power
generation, wind power generation, hydropower generation,
geothermal power generation, and the like, but is not particularly
limited thereto.
[0074] In the organic hydride production apparatus 100 having the
structure set forth above, reactions that occur when toluene (TL)
is used as the hydrogenation target substance are as follows. When
toluene is used as the hydrogenation target substance, the organic
hydride to be obtained is methylcyclohexane (MCH).
<Electrode Reaction at the Anode>
[0075] 2H.sub.2O.fwdarw.O.sub.2+4H.sup.++4e.sup.-
<Electrode Reaction at the Cathode>
[0076] TL+6H.sup.++6e.sup.-.fwdarw.MCH
<Total Reaction>
[0077] 2TL+6H.sub.2O.fwdarw.2MCH+3O.sub.2
[0078] Thus, the electrode reaction at the anode 108 and the
electrode reaction at the cathode 104 proceed in parallel. Protons
(H.sup.+) produced by electrolysis of water at the anode 108 are
supplied to the cathode 104 via the electrolyte membrane 102. The
protons supplied to the cathode 104 are used for hydrogenation of
the hydrogenation target substance at the cathode 104. Accordingly,
toluene is hydrogenated, so that methylcyclohexane is produced.
Therefore, with the organic hydride production apparatus 100
according to the present embodiment, the electrolysis of water and
the hydrogenation of the hydrogenation target substance can be
performed in one step.
[0079] As described above, the organic hydride production apparatus
100 according to the present embodiment includes the electrolyte
membrane 102, the cathode 104, the anode 108, and the anode support
110 provided opposite to the electrolyte membrane 102 side of the
anode 108. The anode support 110 is formed of an elastic porous
body of a plate shape of which the Young's modulus is greater than
0.1 N/mm.sup.2 and less than 43 N/mm.sup.2. By providing such an
elastic and porous anode support 110 of a plate shape, the
electrical connecting condition in each member constituting the
organic hydride production apparatus 100 can be favorably
maintained.
[0080] Maintaining the contact between the electrolyte membrane 102
and the cathode 104 is particularly important. Catholytes made of
organic compounds, such as toluene, are less conductive.
Accordingly, if the electrolyte membrane 102 and the cathode 104
are peeled off from each other, supply of protons from the
electrolyte membrane 102 to the cathode 104 in the peeled part will
be inhibited. If the supply of protons is inhibited, the cathode
catalyst may be deactivated.
[0081] However, by providing the anode support 110, the contact
between the electrolyte membrane 102 and the cathode 104 can be
maintained more certainly. Accordingly, the cell voltage in the
organic hydride production apparatus 100 can be reduced. Therefore,
the efficiency of organic hydride production can be improved.
Further, the life of the organic hydride production apparatus 100
can be prolonged.
[0082] The Young's modulus of the anode support 110 may more
preferably be set in the range from 0.2 N/mm.sup.2 to 10 N/mm.sup.2
inclusive. Accordingly, the cell voltage in the organic hydride
production apparatus 100 can be further reduced. Also, the ratio
T1/T2 of the thickness T1 of the electrolyte membrane 102 to the
thickness T2 of the anode 108 is 0.35 or greater. Accordingly, the
cell voltage in the organic hydride production apparatus 100 can be
reduced more certainly. The base material 108b included in the
anode 108 is a mesh type material. The shape of the mesh is a
rhombic shape, and an average value of the short way of mesh SW and
the long way of mesh LW of the rhombic shape is in the range from
0.3 mm to 3 mm inclusive. Accordingly, the cell voltage in the
organic hydride production apparatus 100 can be reduced more
certainly.
[0083] The present invention is not limited to the embodiment
stated above. It is to be understood that various changes and
modifications, including design modifications, may be made based on
the knowledge of those skilled in the art and that embodiments with
such changes and modifications added are also within the scope of
the present invention.
EXAMPLES
[0084] Examples of the present invention will now be described by
way of example only to suitably describe the present invention and
should not be construed as limiting the scope of the invention.
[Evaluation of Relationships Between Young's Modulus of Anode
Support and Cell Voltage]
[0085] FIG. 2A shows an anode support and a cell voltage in an
organic hydride production apparatus according to each of Test
Examples 1-11. FIG. 2B is a diagram used to describe long way of
mesh LW, short way of mesh SW, and a strand width ST. FIG. 2C shows
relationships between the Young's modulus of the anode support and
the cell voltage.
Test Example 1
[0086] The anode was prepared according to the following procedure.
First, as the base material of the anode, an expanded mesh having a
predetermined mesh shape was prepared. Dry blasting was performed
on the surfaces of the base material, and a cleaning process in a
20 percent sulfuric acid aqueous solution was performed.
Thereafter, the base material was set in an arc ion plating
apparatus using a Ti--Ta alloy target. Accordingly, Ti--Ta alloy
coating was formed on the surfaces of the base material, at the
base material temperature of 150 degrees C. and the vacuum of
1.0.times.10.sup.-2 Torr. The thickness of the coating was set to 2
.mu.m. Thereafter, to the base material subjected to the coating
process, a mixed aqueous solution of iridium tetrachloride and
tantalum pentoxide was applied, and heat treatment was performed
thereon at 550 degrees C. in an electric furnace. By repeating this
operation multiple times, the anode containing equimolar amounts of
iridium oxide and tantalum oxide was obtained. The amount of the
catalyst in the anode was set to 12 g/m.sup.2 in terms of the
amount of Ir metal per electrode area. The Young's modulus of the
anode was set to 40 N/mm.sup.2.
[0087] Also, as shown in FIG. 2A, titanium fiber having a fiber
diameter of 50 .mu.m was placed in the furnace such that the weight
per unit area of the fiber became 600 g/m.sup.2. The titanium fiber
was then sintered with an appropriate load applied thereto under an
inert atmosphere while the temperature in the furnace was set to
900 degrees C. and the heating time was set to 30 minutes. Thus,
the anode support formed of a sintered body of metal fiber was
obtained. The thickness of the anode support was set to 3 mm. Also,
the Young's modulus of the anode support was set to 0.1
N/mm.sup.2.
[0088] Also, a laminated body of the cathode and the electrolyte
membrane was formed according to the following procedure. First,
catalyst ink for the cathode catalyst layer was prepared by adding
5 percent Nafion (registered trademark) Dispersion Solution (made
by E. I. du Pont de Nemours and Company) to powder of PtRu/C
catalyst TEC61E54 (made by TANAKA KIKINZOKU KOGYO K.K.) and by
using a solvent as appropriate. The ratio of Nafion to carbon of
the catalyst ink was set to 0.8. The catalyst ink was further
prepared such that the noble metal amount (the amount of Pt and Ru)
therein became 0.5 mg/cm.sup.2, and then applied to carbon paper
GDL10BC (made by SGL Carbon) using a bar coater. Thereafter, the
carbon paper was heated at 80 degrees C. to dry the solvent
component in the catalyst ink, so that the cathode catalyst layer
was obtained.
[0089] Further, the diffusion layer was prepared by allowing carbon
paper to support Pt particles. The Pt particles included in the
diffusion layer function to promote the chemical reaction between
hydrogen gas as a by-product and the unreacted hydrogenation target
substance at the cathode. First, H.sub.2PtCl.sub.6.6H.sub.2O and
1-propanol was mixed together to prepare a mixed solution. The
amount of H.sub.2PtCl.sub.6.6H.sub.2O added was adjusted such that
the amount of Pt supported by the carbon paper became 0.02
mg/cm.sup.2. In the mixed solution thus obtained, carbon paper
GDL10BC (made by SGL Carbon) was immersed.
[0090] Thereafter, the carbon paper was completely dried under a
N.sub.2 gas atmosphere at 60 degrees C. Subsequently, the carbon
paper was immersed in a 1-mg NaBH.sub.4 aqueous solution, and
reduction treatment was performed for two hours. After the
reduction treatment, the carbon paper was immersed in pure water to
be cleaned. Thereafter, the carbon paper was dried and obtained as
the diffusion layer. Also, as the electrolyte membrane, Nafion
(registered trademark) 117 (made by E. I. du Pont de Nemours and
Company) was prepared. The thickness of the electrolyte membrane
was set to 0.175 mm. To the electrolyte membrane, the cathode
catalyst layer and the diffusion layer were laminated, and hot
pressing is performed thereon for three minutes at 120 degrees C.
and 1 MPa. Thus, a laminated body of the cathode and the
electrolyte membrane was obtained.
[0091] Also, a complex of a cathode-side separator and a flow
passage part, an anode-side separator, and a cathode spacer and an
anode spacer were prepared. The complex and the anode-side
separator used are made of titanium. The complex, the cathode
spacer, the laminated body of the cathode and the electrolyte
membrane, the anode, the anode support, the anode spacer, and the
anode-side separator were laminated in this order. The resulting
laminated body was then fitted, with pressure applied thereto from
the outside. Pressing each layer using elastic force of the anode
support could create a state in which the layers are in close
contact with each other. Through the processes set forth above, the
organic hydride production apparatus of Test Example 1 was
obtained. The active electrode area of the organic hydride
production apparatus was set to 100 cm.sup.2.
[0092] To the cathode chamber inlet in the cathode spacer, a supply
passage for the hydrogenation target substance was connected. To
the cathode chamber outlet in the cathode spacer, a discharge
passage for the organic hydride was connected. Also, to the anode
chamber inlet in the anode spacer, a supply passage for the anolyte
was connected. To the anode chamber outlet in the anode spacer, a
discharge passage for the anolyte was connected.
[0093] In this organic hydride production apparatus, toluene as the
catholyte was made to flow through the cathode chamber. Also, 100
g/L sulfuric acid aqueous solution as the anolyte was made to flow
through the anode chamber. The flow rate of the catholyte was set
to 10 mL/minute. The flow rate of the anolyte was also set to 10
mL/minute. At the temperature of 60 degrees C. and the current
density of 0.4 A/cm.sup.2, the electrolytic reaction was caused.
The anolyte was supplied from the anolyte storage tank to the anode
chamber using a pump, and then returned from the anode chamber to
the anolyte storage tank to be circulated (batch operation). The
anolyte was supplied through a lower part of the organic hydride
production apparatus to the anode chamber. Also, the anolyte was
circulated while an amount of water reduced by electrolysis was
supplemented.
[0094] The negative electrode and the positive electrode of a
constant-current power supply were connected respectively to the
cathode and the anode. The output current of the constant-current
power supply was set to 40 A (0.4 A/cm.sup.2) and applied to the
organic hydride production apparatus. The cell voltage in the
organic hydride production apparatus was measured. FIG. 2A shows
the result.
Test Examples 2-9
[0095] The organic hydride production apparatus of each of Test
Examples 2-9 was prepared, in which the fiber diameter and the
weight per unit area of the fiber constituting the anode support,
and the thickness and the Young's modulus of the anode support were
adjusted, as shown in FIG. 2A, and the other procedures were
performed according to Test Example 1. The cell voltage in each
organic hydride production apparatus was measured. FIG. 2A shows
the results.
Test Examples 10 and 11
[0096] The organic hydride production apparatus of each of Test
Examples 10 and 11 was prepared, in which an anode support formed
of an expanded mesh, instead of a sintered body of metal fiber, was
used, as shown in FIG. 2A, and the other procedures were performed
according to Test Example 1. The cell voltage in each organic
hydride production apparatus was measured. FIG. 2A shows the
results. The long way of mesh LW, the short way of mesh SW, and the
strand width ST of the expanded mesh are as illustrated in FIG. 2B
and are matters well known to persons skilled in the art.
[0097] FIG. 2C shows relationships between the Young's modulus of
the anode support and the cell voltage in the organic hydride
production apparatus according to each Test Example. As shown in
FIG. 2C, it is ascertained that, when the Young's modulus of the
anode support is greater than 0.1 N/mm.sup.2 and less than 43
N/mm.sup.2, the cell voltage falls below 2.2 V. The cell voltage of
2.2 V corresponds to a cell voltage in a conventionally well-known
organic hydride production apparatus that does not include the
anode support of the subject application. Accordingly, it is
ascertained that, when the Young's modulus of the anode support is
greater than 0.1 N/mm.sup.2 and less than 43 N/mm.sup.2, the
efficiency of organic hydride production can be improved. It is
also ascertained that, when the Young's modulus of the anode
support is in the range from 0.2 N/mm.sup.2 to 10 N/mm.sup.2
inclusive, the cell voltage is 2.0 V or less. The cell voltage of
2.0 V corresponds to a cell voltage in alkaline water electrolysis.
Accordingly, it is ascertained that, when the Young's modulus of
the anode support is in the range from 0.2 N/mm.sup.2 to 10
N/mm.sup.2 inclusive, the efficiency of organic hydride production
can be improved to be comparable to or greater than the efficiency
of hydrogen production in alkaline water electrolysis. Further, it
is ascertained that, when the Young's modulus of the anode support
is in the range from 0.3 N/mm.sup.2 to 1.2 N/mm.sup.2 inclusive,
the efficiency of organic hydride production can be further
improved.
[Evaluation of Relationships Between Thickness Ratio of Electrolyte
Membrane and Anode, and Cell Voltage]
[0098] FIG. 3A shows thicknesses of the electrolyte membrane and
the anode included in the organic hydride production apparatus
according to each of Test Examples 2 and 12-14, the ratio of the
thicknesses, and the cell voltage. FIG. 3B shows relationships
between the ratio of the thicknesses and the cell voltage.
Test Examples 2 and 12-14
[0099] The organic hydride production apparatus of each of Test
Examples 2 and 12-14 was prepared, in which the thickness T1 of the
electrolyte membrane was fixed while the thickness T2 of the anode
was adjusted to vary the thickness ratio T1/T2, as shown in FIG.
3A, and the other procedures were performed according to Test
Example 1. The Young's modulus of the anode support was set to 0.3
N/mm.sup.2 in all the Test Examples. The cell voltage in each
organic hydride production apparatus was measured. FIG. 3A shows
the results.
[0100] FIG. 3B shows relationships between the ratio T1/T2 of the
thickness T1 of the electrolyte membrane to the thickness T2 of the
anode, and the cell voltage in the organic hydride production
apparatus according to each Test Example. As shown in FIG. 3B, when
the thickness ratio T1/T2 is 0.35 or greater, the cell voltage is
less than 2.0 V. Accordingly, it is ascertained that, when the
thickness ratio T1/T2 is set to 0.35 or greater, the efficiency of
organic hydride production can be improved more certainly to be
greater than the efficiency of hydrogen production in alkaline
water electrolysis.
[Evaluation of Relationships Between Aperture Dimensions of Anode
and Cell Voltage]
[0101] FIG. 4A shows mesh dimensions of the anode and the cell
voltage in the organic hydride production apparatus according to
each of Test Examples 15-19. FIG. 4B shows relationships between an
average value of the long way of mesh LW and the short way of mesh
SW, and the cell voltage.
Test Examples 15-19
[0102] The organic hydride production apparatus of each of Test
Examples 15-19 was prepared, in which the long way of mesh LW and
the short way of mesh SW of the mesh in the anode base material was
varied, as shown in FIG. 4A, and the other procedures were
performed according to Test Example 1. The Young's modulus of the
anode support was set to 0.3 N/mm.sup.2 in all the Test Examples.
The cell voltage in each organic hydride production apparatus was
measured. FIG. 4A shows the results.
[0103] FIG. 4B shows relationships between the average value of the
long way of mesh LW and the short way of mesh SW, and the cell
voltage in the organic hydride production apparatus according to
each Test Example. As shown in FIG. 4B, when the average value is
in the range from 0.3 mm to 3 mm inclusive, the cell voltage is 2.0
V or less. Accordingly, it is ascertained that, when the average
value is set in the range from 0.3 mm to 3 mm inclusive, the
efficiency of organic hydride production can be improved more
certainly to be equal to or greater than the efficiency of hydrogen
production in alkaline water electrolysis. Also, when the average
value is greater than 0.3 mm and equal to or less than 3 mm, the
cell voltage is less than 2.0 V. Accordingly, it is ascertained
that, when the average value is set to be greater than 0.3 mm and
equal to or less than 3 mm, the efficiency of organic hydride
production can be improved more certainly to be greater than the
efficiency of hydrogen production in alkaline water
electrolysis.
* * * * *