U.S. patent application number 13/645117 was filed with the patent office on 2013-04-11 for membrane electrode assembly and organic hydride manufacturing device.
This patent application is currently assigned to Hitachi, Ltd.. The applicant listed for this patent is Hitachi, Ltd.. Invention is credited to Takayuki HIRASHIGE, Takao Ishikawa.
Application Number | 20130087451 13/645117 |
Document ID | / |
Family ID | 48018950 |
Filed Date | 2013-04-11 |
United States Patent
Application |
20130087451 |
Kind Code |
A1 |
HIRASHIGE; Takayuki ; et
al. |
April 11, 2013 |
Membrane Electrode Assembly and Organic Hydride Manufacturing
Device
Abstract
There is provided a membrane electrode assembly and an organic
hydride manufacturing device capable of obtaining higher energy
efficiency even if manufacturing organic hydride in one step with a
single device. A membrane electrode assembly in which a cathode
catalyst layer and an anode catalyst layer are placed to sandwich a
solid polymer electrolyte membrane, wherein the cathode catalyst
layer includes catalytic metal which causes hydrogenation of
unsaturated hydrocarbons to organic hydrides, and a carrier of the
catalytic metal, and the carrier provides on its surface a
functional group which decreases wettability of the unsaturated
hydrocarbons.
Inventors: |
HIRASHIGE; Takayuki;
(Hitachi, JP) ; Ishikawa; Takao; (Hitachi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi, Ltd.; |
Tokyo |
|
JP |
|
|
Assignee: |
Hitachi, Ltd.
Tokyo
JP
|
Family ID: |
48018950 |
Appl. No.: |
13/645117 |
Filed: |
October 4, 2012 |
Current U.S.
Class: |
204/265 ;
204/263; 204/282 |
Current CPC
Class: |
C25B 11/04 20130101;
C25B 3/04 20130101; C25B 11/0442 20130101 |
Class at
Publication: |
204/265 ;
204/282; 204/263 |
International
Class: |
C25B 11/06 20060101
C25B011/06; C25B 13/08 20060101 C25B013/08; C25B 11/08 20060101
C25B011/08; C25B 3/00 20060101 C25B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 6, 2011 |
JP |
2011-221674 |
Claims
1. A membrane electrode assembly in which a cathode catalyst layer
which reduces an unsaturated hydrocarbon and an anode catalyst
layer which oxides water are placed to sandwich a solid polymer
electrolyte membrane which is proton conductive, wherein the
cathode catalyst layer includes a catalytic metal which causes
hydrogenation of a unsaturated hydrocarbon to organic hydride, a
carrier which supports the catalytic metal, and the solid polymer
electrolyte membrane which is proton conductive; and a functional
group which decreases wettability of the unsaturated hydrocarbons
is introduced onto a surface of the carrier.
2. An organic hydride manufacturing device, comprising the membrane
electrode assembly according to claim 1, a member supplying the
unsaturated hydrocarbon to the cathode catalyst layer, and a member
supplying water or steam to the anode catalyst layer.
3. The membrane electrode assembly according to claim 1, wherein
the functional group includes at least one of a sulfonate group, a
phosphonate group, a hydroxyl group, a sulfomethyl group, a
carboxyl group, a carbonyl group, and a carboxylate group.
4. The membrane electrode assembly according to claim 1, wherein
the catalytic metal consists of platinum, ruthenium, rhodium,
palladium, iridium, molybdenum, rhenium, wolfram, and an alloy
including at least some of these.
5. The membrane electrode assembly according to claim 1, wherein
the unsaturated hydrocarbon is benzene, toluene, xylene,
mesitylene, naphthalene, methylnaphthalene, or anthracene.
6. The organic hydride manufacturing device according to claim 2,
wherein the unsaturated hydrocarbon is benzene, toluene, xylene,
mesitylene, naphthalene, methylnaphthalene, or anthracene.
7. An organic hydride manufacturing device comprising a cathode
catalyst layer, an anode catalyst layer, and a separator which
supplies an unsaturated hydrocarbon to the cathode catalyst layer
to remove organic hydride, and supplies H.sub.2O to the anode
catalyst layer to evacuate oxygen and water, wherein the cathode
catalyst layer is placed on one surface of a solid polymer
electrolyte membrane, and the anode catalyst layer is placed on
another surface of the solid polymer electrolyte membrane, the
cathode catalyst layer includes a catalytic metal which causes
hydrogenation of an unsaturated hydrocarbon to the organic hydride,
and a carrier which supports the catalytic metal, and the carrier
has on its surface a functional group which decreases wettability
of the unsaturated hydrocarbon.
8. The organic hydride manufacturing device according to claim 7,
wherein hydrogen is supplied from the anode catalyst layer to the
cathode catalyst layer.
9. The organic hydride manufacturing device according to claim 7,
wherein the carrier is electron-conductive carbon.
10. The organic hydride manufacturing device according to claim 7,
wherein the functional group is a sulfonate group.
11. The organic hydride manufacturing device according to claim 7,
wherein the separator has electroconductivity as well as a channel
groove through which unsaturated hydrocarbons and H.sub.2O
flow.
12. The organic hydride manufacturing device according to claim 7,
wherein supply of unsaturated hydrocarbons onto the cathode
catalyst layer and supply of H.sub.2O onto the anode catalyst layer
are feasible via a diffusion layer.
13. The organic hydride manufacturing device according to claim 12,
wherein the diffusion layer is carbon paper or carbon cloth.
14. The organic hydride manufacturing device according to claim 7,
wherein the cathode catalyst layer includes a solid polymer
electrolyte.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority from Japanese patent
application JP 2011-221674 filed on Oct. 6, 2011 the content of
which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a membrane electrode
assembly and an organic hydride manufacturing device, for
manufacturing organic hydride electrochemically.
[0004] 2. Description of the Related Art
[0005] While global warming by carbon dioxide and the like is
getting serious, hydrogen as an energy source responsible for the
next generation instead of fossil fuels receives attention. With
hydrogen fuels, the only emission during fuel consumption is water,
and due to no carbon dioxide emission, the environmental load is
low. On the other hand, because hydrogen is a gas at the ordinary
temperature and normal pressure, the system of transporting,
storing, and supplying it is an important problem.
[0006] Recently, an organic hydride system using hydrocarbon like
as cyclohexane, methylcyclohexane and decalin is drawing attention
as a superior hydrogen storing system in safety, transportability,
and storing capacity. Since these hydrocarbons are liquid at
ordinary temperature, they are superior in transportability. For
example, although toluene and methylcyclohexane are cyclic
hydrocarbons having the same carbon number, while toluene is an
unsaturated hydrocarbon in which the bonding between the
hydrocarbons is a double bond, methylcyclohexane is a saturated
hydrocarbon having no double bond. Methylcyclohexane is yielded by
the hydrogenation of toluene, and toluene is yielded by the
dehydrogenation. Thus, utilizing the hydrogenation and the
dehydrogenation of hydrocarbon allows the storage and the supply of
hydrogen.
[0007] To manufacture organic hydride such as methylcyclohexane,
firstly, it is needed to manufacture hydrogen, and then react the
hydrogen and toluene on a catalyst. In other words, the current
process is a two-stage process in which hydrogen is yielded in
water-electrolyzer and the like, and hydrogen and toluene is
reacted to yield organic hydride in the hydrogenation device.
[0008] Therefore, plural devices are needed toward manufacturing
organic hydride, and there occurs a problem called complication of
the devices. Furthermore, since hydrogen is a gas until
hydrogenation occurs, there occurs a problem on the storage and the
transport. If the hydrogen manufacturing device and the
hydrogenation device are constructed adjacently, the
above-mentioned problem will be solved; however, there is an issue
of costs of construction and operation, and the overall energy
efficiency is also decreased. Furthermore, since the increasing
size of the devices is needed, there is also a problem that the
installation location is limited.
[0009] Contrary to the two-stage process, the technologies of
manufacturing organic hydride in one-stage with only one device has
been proposed (for example, Japanese Patent Laid-Open 2003-45449,
Catalysis Today, 56, 307 (2000)). They manufacture organic hydride
electrochemically. For example, in Japanese Published Unexamined
Application No. 2003-45449, organic hydride is manufactured by
placing metallic catalysts on the both sides of a hydrogen ion
permeable electrolyte membrane, respectively, supplying water or
steam on one side and unsaturated hydrocarbon (s) on the other
side, and causing the hydrogenation of unsaturated hydrocarbon (s)
to saturated hydrocarbon (s) (organic hydride (s)) by hydrogen ion
yielded by electrolysis of water or steam. Respective reaction
formulae of anode and cathode in the case of using toluene as an
unsaturated hydrocarbon are as follows.
H.sub.2O.fwdarw.2H.sup.++(1/2)O.sub.2+2e.sup.- (1)
C.sub.7H.sub.8+6H.sup.++6e.sup.-.fwdarw.C.sub.7H.sub.14 (2)
SUMMARY OF THE INVENTION
[0010] With these methods of manufacturing organic hydride,
however, it has been difficult to obtain higher energy
efficiency.
[0011] An object of the present invention is to provide a membrane
electrode assembly and an organic hydride manufacturing device
capable of obtaining higher energy efficiency even if manufacturing
organic hydride in one step with a single device.
[0012] One embodiment for achieving the above-mentioned object is a
membrane electrode assembly in which a cathode catalyst layer which
reduces unsaturated hydrocarbons and an anode catalyst layer which
oxides water are placed to sandwich a solid polymer electrolyte
membrane which is proton conductive, wherein the cathode catalyst
layer includes a catalytic metal which makes an organic hydride by
reducing the unsaturated hydrocarbon, a carrier which supports the
catalytic metal, and the solid polymer electrolyte membrane which
is proton conductive; and a functional group which decreases
wettability of the unsaturated hydrocarbon is introduced onto a
surface of the carrier.
[0013] In addition, it is an organic hydride manufacturing device
including the membrane electrode assembly, a member supplying the
unsaturated hydrocarbon to the cathode catalyst layer, and a member
supplying water or steam to the anode catalyst layer.
[0014] Furthermore, it is an organic hydride manufacturing device
including a cathode catalyst layer, an anode catalyst layer, and a
separator which supplies an unsaturated hydrocarbon to the cathode
catalyst layer to remove organic hydride, and supplies H.sub.2O to
the anode catalyst layer to evacuate oxygen and water, wherein the
cathode catalyst layer is placed on one surface of a solid polymer
electrolyte membrane, and the anode catalyst layer is placed on
another surface of the solid polymer electrolyte membrane, the
cathode catalyst layer includes a catalytic metal which makes an
organic hydride by reducing the unsaturated hydrocarbon, and a
carrier which supports the catalytic metal, and the carrier has on
its surface a functional group which decreases wettability of the
unsaturated hydrocarbon.
[0015] According to the present invention, by introducing a
functional group which decreases wettability of the unsaturated
hydrocarbon on the surface of the carrier which supports the
catalytic metal, it is possible to provide a membrane electrode
assembly and an organic hydride manufacturing device capable of
obtaining higher energy efficiency, even if manufacturing organic
hydride in one step with a single device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a cross-sectional view illustrating one example of
an organic hydride manufacturing device with relation to an
embodiment of the present invention;
[0017] FIGS. 2A to 2C are views illustrating a membrane electrode
assembly with relation to an embodiment of the present invention;
2A is a plan view, 2B is a D-E cross-sectional view of the plan
view, and 2C is an enlarged view of part F of the cross-sectional
view;
[0018] FIGS. 3A to 3C are views illustrating a membrane electrode
assembly of a related art; 3A is a plan view, 3B is a D-E
cross-sectional view of the plan view, and 3C is an enlarged view
of part F of the cross-sectional view;
[0019] FIG. 4 is a view illustrating one example of the relation
between current density and applied voltage, in the organic hydride
manufacturing device with relation to First Example of the present
invention;
[0020] FIG. 5 is a view illustrating one example of the relation
between conversion rate and applied voltage, in the organic hydride
manufacturing device with relation to First Example of the present
invention;
[0021] FIG. 6 is a view illustrating one example of the relation
between current density and applied voltage, in the organic hydride
manufacturing device with relation to First Comparative
Example;
[0022] FIG. 7 is a view illustrating one example of the relation
between conversion rate and applied voltage; and
[0023] FIG. 8 is a view illustrating one example of current density
and conversion rate, in the organic hydride manufacturing device
with relation to the first to the third examples of the present
invention, and First Comparative Example.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The inventors examined the reasons why higher energy
efficiency was not obtainable when manufacturing organic hydride in
one-stage with the conventional single device. As a result, they
found that there was a problem in wettability of unsaturated
hydrocarbons such as toluene to electrodes, as one of the reasons.
The electrodes of a single organic hydride manufacturing device in
one-stage is formed of the layer in which a proton conductive
electrolyte is mixed with catalyst, and called as a catalytic
layer. Of the catalytic layer, a catalyst includes a carrier
supports metallic catalyst such as platinum. The condition like
having higher electron conductivity, higher specific surface area
to prevent coagulation of metallic catalyst such as platinum and to
enhance the dispensability, and the like are needed for the
carrier, and carbon-based material is used generally.
[0025] However, the wettability of unsaturated hydrocarbons such as
toluene to carbon-based material is very strong and easy to become
wet. For example, activated carbon is the carbon-based material
which has large specific surface area, and it is known that toluene
is adsorbed to activated carbon. It was speculated that when the
wettability of unsaturated hydrocarbons such as toluene to a
carrier carbon was strong, the unsaturated hydrocarbon was covered
on the carbon surface of the carrier, and absorbed or stagnated on
the carbon surface to inhibit the consecutive supply of unsaturated
hydrocarbons to a catalyst. In that case, a catalyst which is not
supplied with unsaturated hydrocarbons and does not contribute to
reaction appears and the energy efficiency becomes low. Therefore,
when the carrier carbon was surface-reformed, and the wettability
of unsaturated hydrocarbons such as toluene was decreased, it was
found possible to prevent stagnating of unsaturated hydrocarbons on
the surface of a catalytic layer and to supply unsaturated
hydrocarbons to catalyst stably.
[0026] The present invention originated from the basis of the
above-mentioned findings, and is able to make surface reforming to
introduce a functional group such as a sulfonate group, a hydroxyl
group, a carboxylate group and the like in a catalytic carrier in a
membrane electrode assembly and an organic hydride manufacturing
device, for manufacturing organic hydride electrochemically, and is
able to use carbon, as a catalytic carrier, which has been
decreased in wettability of unsaturated hydrocarbons such as
toluene. In addition, the catalyst which supports metallic catalyst
on the carbon, and the catalyst in which a solid polymer
electrolyte membrane which is proton conductive is mixed together
properly have electrode structures which are formed both sides of a
solid polymer electrolyte membrane which is proton conductive. On
the electrodes, by applying voltage between anode-cathode in the
situation that water or steam is supplied onto the anode side and
unsaturated hydrocarbons are supplied onto cathode side, it is
possible to cause electrolysis of water on the anode and
hydrogenation of unsaturated hydrocarbons on the cathode, followed
by producing organic hydride.
[0027] Embodiments according to the present invention will be
described with figures in detail.
[0028] One example of an organic hydride manufacturing device
according to an embodiment of the present invention is shown in
FIG. 1. An organic hydride manufacturing device of the embodiment
is made up by jointing an anode catalyst layer 13 on one surface of
a solid polymer electrolyte membrane 12 and a cathode catalyst
layer 14 on the other surface of the solid polymer electrolyte
membrane 12, and sandwiching integrated membrane electrode assembly
(MEA) with a gas diffusion layer 15 and a separator 11 in which a
groove as a channel for gas and the like is formed. In addition, a
gasket 16 for gas seal is inserted between a pair of the separators
11.
[0029] The separator 11 has electroconductivity, and for its
quality of material, dense graphite plates, carbon plates into
which carbon materials such as graphite and carbon black are molded
by resin, as well as metallic materials with superior corrosion
resistance such as stainless steel and titanium are desirable. In
addition, noble metal plating for the surface of the separator 11
and applying highly corrosion resistant and heat resistant
electro-conductive paint and preparing surface treatment are also
desirable. A groove which becomes a channel of reactive gas or
liquid on the surface opposite to an anode catalyst layer 13 and a
cathode catalyst layer 14 of the separator 11 is formed. Water or
steam is supplied through the groove channel of the separator 11 on
the anode side. Water or steam flowing through the groove channel
is supplied via gas diffusion layer 15 to the anode catalyst layer
13. In addition, unsaturated hydrocarbons are supplied onto the
separator 11 of the cathode side. Unsaturated hydrocarbons flowing
through the groove channel are supplied via gas diffusion layer 15
to a cathode catalyst layer 14. As a method of supplying
unsaturated hydrocarbons, liquid unsaturated hydrocarbons may be
supplied intact, and/or vaporous unsaturated hydrocarbons making He
gas, N.sub.2 gas and the like as a carrier may be supplied.
[0030] A gas diffusion layer 15 is arranged to supply reactive
substances (gas or liquid) supplied into the channel of the
separator 11 in planes of catalyst layers, and uses a substrate
having gas permeability such as carbon paper or carbon cloth.
[0031] The gasket 16 has insulation quality, and has resistance to,
especially, hydrogen, unsaturated hydrocarbons, or organic hydride,
and may have quality of material which has its less permeability
and of which hermeticity can be maintained, including butyl rubber,
Viton rubber, EPDM rubber (ethylene-propylene-diene rubber) and the
like, for example.
[0032] When applying voltage between anode and cathode in the state
of supplying water or steam at the anode side and toluene as an
unsaturated hydrocarbon at the cathode side, electrolysis of water
according to the formula (1) occurs. Proton yielded by electrolysis
according to the formula (1) transfers via a solid polymer
electrolyte membrane 12 to a cathode catalyst layer 14, and in the
cathode catalyst layer, hydrogenation according to the formula (2)
occurs and methylcyclohexane which is organic hydride yields.
H.sub.2O.fwdarw.2H.sup.++(1/2)O.sub.2+2e.sup.- (1)
C.sub.7H.sub.8+6H.sup.++6e.sup.-.fwdarw.C.sub.7H.sub.14 (2)
[0033] An organic hydride device of the present embodiment makes
hydrogenation of unsaturated hydrocarbons electrochemically to
yield organic hydride.
[0034] FIGS. 2A to 2C show electrode parts of an organic hydride
manufacturing device according to the embodiment. FIGS. 2A to 2C
show a plan view of MEA where a cathode catalyst layer 22 or an
anode catalyst layer 23 on each side of a solid polymer electrolyte
membrane is formed seen from the cathode side, a D-E
cross-sectional view of the plan view, and an enlarged view of part
F of the cross-sectional view, respectively.
[0035] As illustrated in the D-E cross-sectional view, the cathode
and the anode are formed as dense catalyst layers on and below a
solid polymer electrolyte membrane 21. As the cathode catalyst
layer 22 is illustrated on the enlarged view, catalytic metal 24 is
supported on the carbon (carrier) 25 which is a catalytic carrier.
The surface treatment is prepared on the carbon 25, and functional
groups 27 are introduced. Thus, unsaturated hydrocarbons such as
toluene are difficult to wet to the catalyst, and unsaturated
hydrocarbons are supplied stably to the catalyst, without covering
the catalytic layer surface with unsaturated hydrocarbons and
stagnating. In addition, fugacity of organic hydride yielded by
hydrogenation becomes also higher. Furthermore, the number 28
denotes unsaturated hydrocarbons or organic hydride.
[0036] The carbons 25 are adhered each other with a solid polymer
electrolyte 26. The catalytic metal 24 has a network configuration
linked via carbon 25 together, and forms a path for electron
required for the reaction of the formula (2). In addition, a solid
polymer electrolyte 26 has a linking network configuration as well,
and forms a path for proton required for the reaction of the
formula (2).
[0037] Electrode reaction is conducted at the three-phase interface
where the catalytic metal 24 on the carbons 25, a solid polymer
electrolyte, and the reactant unsaturated hydrocarbons contact. In
the electrode of the embodiment, a path for proton is formed by a
solid polymer electrolyte 26, so that the three-phase interface is
formed even in the catalytic metal 24 which does not contact
directly the solid polymer electrolyte membrane 21, then there is
provided a configuration in which many metallic catalysts are able
to contribute to the electrode reaction, provided that the solid
polymer electrolyte membrane 21 provides a solid polymer
electrolyte and it is desirable but not essential for a cathode
catalyst layer to comprise solid polymer electrolytes 26.
[0038] An electrode part of an organic hydride manufacturing device
of a related art is shown in FIGS. 3A to 3C. FIGS. 3A to 3C show a
plan view of an MEA where a cathode catalyst layer 32 and an anode
catalyst layer are formed on each side of a solid polymer
electrolyte membrane 31, part D-part E cross-sectional view of the
plan view, and an enlarged view of part F of the cross-sectional
view, respectively. On the electrodes in the FIGS. 3A to 3C,
unsaturated hydrocarbons cover on the carbon surface of the
carrier, and absorb or stagnate on the carbon surface, so that
unsaturated hydrocarbons are not supplied, catalysts not
contributing to the reaction are generated, and energy efficiency
becomes lower. Furthermore, the number 34 denotes catalytic metal,
the number 35 denotes carbon carrier, and the number 36 denotes
unsaturated hydrocarbons or organic hydride.
[0039] The carbon 25, which is a catalytic carrier of the
embodiment, is characterized in that the functional groups 27 are
introduced by surface reforming. Hereby, unsaturated hydrocarbons
become difficult to wet, stagnation of unsaturated hydrocarbons on
the surface of a cathode catalyst layer 22 is prevented, and the
supply of unsaturated hydrocarbons to the cathode catalyst layer 22
is not inhibited.
[0040] Anything is acceptable for the functional groups 27 which
are introduced on the carbon surface as long as they decrease
wettability of unsaturated hydrocarbons such as toluene and
increase oil repellency. For example, they include a sulfonate
group, a phosphonate group, a hydroxyl group, a sulfomethyl group,
a carboxyl group, a carbonyl group, a carboxylate group and the
like. At least one of these may be included, and especially a
sulfonate group is practically suitable.
[0041] As the carrier 25, anything is acceptable as long as it is
electron-conductive carbon. For example, it includes furnace black
and channel black, acetylene black, amorphous black, carbon
nanotube, carbon nanohorn, carbon black, activated carbon, graphite
and the like. These can be used alone or by mixture.
[0042] As a method of surface-treating of carbon to introduce
functional groups, for example, it is possible to treat carbon with
sulfuric gas, fuming sulfuric acid, sulfuric acid and the like to
introduce sulfonate groups. In addition, it is possible to treat
carbon with sodium sulfite, sodium bisulfite, aqueous formalin
solution, paraformaldehyde and the like to introduce a sulfomethyl
group. Moreover, it can be considered to irradiate oxygen plasma
for the introduction of hydroxyl groups.
[0043] On the other hand, a catalytic material causing
hydrogenation is used as the catalytic metal 24 used in the present
embodiment, metals such as Ni, Pd, Pt, Rh, Ir, Re, Ru, Mo, W, V,
Os, Cr, Co, Fe and the like as well as their alloy catalysts, for
example, are possible to use, and especially, Pt (platinum),
ruthenium (Ru), rhodium (Rh), palladium (Pa), iridium (Ir),
molybdenum (Mo), rhenium (Re), wolfram (W) and their alloy are
practically suitable. It is preferable to micronized hydrogenation
catalysts, for cost reduction by the decrease of catalytic metals,
and an increased reaction surface area.
[0044] In addition, as a method of supporting the catalytic metal
24 on the carrier carbon 25, there are coprecipitation, thermal
decomposition, electroless plating and the like, and have no
particular limitation.
[0045] The MEA of the embodiment can be prepared by the following
method. Firstly, a cathode catalyst paste to which a catalyst with
the catalytic metal 24 supported by the surface-treated carbon 25,
a solid polymer electrolyte, and a solvent which dissolved a solid
polymer electrolyte, is added to mix thoroughly, and an anode
catalyst paste where platinum black, a solid polymer electrolyte,
and a solvent which dissolved a solid polymer electrolyte are added
to mix thoroughly are prepared. Those pastes are sprayed onto
release film such as polyfluoroethylene (PTFE) film, with spray-dry
method and the like, respectively, and dried at 80.degree. C. to
evaporate the solvent to form cathode and anode catalyst layers.
Next, those cathode and anode catalyst layers are joined by hot
press method with sandwiching the solid polymer electrolyte
membrane 21 in the middle, and it is possible to prepare MEA of the
embodiment by peeling off the release film (PTFE).
[0046] In addition, as another example of MEA preparation of the
present embodiment, it is also possible to prepare it by spraying a
cathode catalyst paste in which a catalyst with the catalytic metal
24 supported by the surface-treated carbon 25, a solid polymer
electrolyte, and a solvent which dissolves a solid polymer
electrolyte are added to the above-mentioned surface-treated carbon
25 and mixed thoroughly, and anode catalyst paste in which platinum
black, a solid polymer electrolyte, and a solvent which dissolves a
solid polymer electrolyte, to the solid polymer electrolyte
membrane 21 directly with spray-dry method and the like.
[0047] As polymer electrolytes which compose the solid polymer
electrolyte membrane 21, perfluorocarbon sulfonate, or materials
which have doped or bound chemically and fixed proton donor such as
sulfonate groups, phosphonate groups and carboxyl groups to
polystyrene, polyether ketone, polyetherether ketone, polysulfone,
polyethersulfone or the other engineering plastic materials, can be
used. In addition, by transforming the above-mentioned materials to
cross-linked structure or fluorinating it partially, the material
stability can be enhanced.
[0048] For a solid polymer electrolyte contained in a catalytic
layer, a polymer material which shows proton conductivity is used,
and examples include sulfonated or alkylene-sulfonated
fluorine-based polymer and polystyrenes which are represented by
perfluorocarbon-based sulfonate resin and
polyperfluorostyrene-based sulfonate resin. Further, the materials
in which proton donor is introduced to polysulfones
polyethersulfones, polyetherethersulfones, polyetherether ketones,
or hydrocarbon-based polymer are included. In addition, composite
electrolyte of polymer material of the embodiment and metal oxide
hydrates can be used.
[0049] As an unsaturated hydrocarbon, aromatic hydrocarbon can be
used, and for example either of benzene, toluene, xylene,
mesitylene, naphthalene, methylnaphthalene, anthracene, biphenyl,
phenanthroline and their alkyl substitutes, or a multi-mixture can
be used. Hydrogen is added to a double bond of these carbons so
that hydrogen can be stored.
[0050] In the following, the present invention will be described
with examples in detail. However, the present invention is not
limited to examples mentioned below.
First Example
[0051] As a catalyst, a catalyst where 30 wt % of Pt particulates
was dispersed and supported on carbon black was used. Firstly, 100
g of this catalyst was preheated for one hour at 105.degree. C.
Subsequently, sulfur trioxide heated to 100.degree. C. was
transferred at 12 vol. % of concentration to dry air, and reacted
with the catalyst. Reaction time was two hours. Subsequently, it
was cooled, the catalyst was submitted to ion exchanged water,
stirred and filtrated, and washed with ion exchanged water until pH
of the filtrate became constant.
[0052] When the infrared absorption spectrum was measured to the
obtained catalyst, the peaks were observed at 620 cm.sup.-1, 1037
cm.sup.-1 and 1225 cm.sup.-1. This was considered as the peak based
on the sulfonate group --SO.sub.3H, and it was confirmed that the
sulfonate group was introduced on the surface of the carbon black
which was a carrier. The equivalent of the introduced sulfonate
group was 1.8 milliequivalent/g dry carbon carrier.
[0053] The above-obtained catalyst was used as a cathode catalyst,
and MEA, the configuration of which was shown in FIG. 2, was
prepared. Nafion (manufactured by DuPont) was used for an
electrolyte membrane. A cathode catalyst layer 22 was formed by
applying catalyst slurry on Nafion directly with a spray coater.
The cathode catalyst layer 22 was applied on Nafion in the
following order.
[0054] Firstly, Nafion was put on a hotplate as a substrate, and
was fixed by suction. The temperature of the hot plate was
50.degree. C. Next, a mask was put on it, and cathode catalyst
slurry was sprayed with a spray coater (manufactured by Nordson).
The mixture of the catalyst prepared in the example and water, 5%
(wt) Nafion solution and 221 solution (the solution of
1-propanol:2-propanol:water=2:2:1) was used in the weight ratio of
2:1.2:5.4:10.6. Spraying condition was 0.01 MPa of hydraulic
pressure, 0.15 MPa of swirl pressure, 0.15 MPa of atomization
pressure, 60 mm of gun/substrate distance and 50.degree. C. of
substrate temperature. The amount of the cathode catalyst was 0.4
mg Ptcm.sup.-2.
[0055] A cathode catalyst layer 22 was formed on a Nafion surface,
followed by forming an anode catalyst layer 23 on the opposite
surface. The anode catalyst layer 23 was formed by transferal.
Firstly, anode catalyst slurry was prepared. A mixture of platinum
black HiSPEC1000 (manufactured by Johnson Matthey), 5% (wt) Nafion
solution and 221 solution was used in the weight ratio of
1:1.11:2.22. It was applied on Teflon (registered trademark) sheet
by an applicator. The anode catalyst layer which was applied on
Teflon (registered trademark) sheet was formed on the Nafion
surface with heat transfer printing by hot press (SA-401-M
manufactured by Tester Sangyo). The pressure of hot press was 37.2
kgfcm.sup.2, the temperature of hot press was 120.degree. C., and
hot press time was two minutes. The amount of anode catalyst was
4.8 mg Ptcm.sup.-2.
[0056] The prepared MEA was incorporated into the device of
manufacturing organic hydride in FIG. 1. Toluene was used as an
unsaturated hydrocarbon. In the state that toluene was supplied to
cathode in 10 cc/min and purified water was supplied to the anode
in 5 cc/min, voltage was applied between the anode and the cathode.
It was conducted at 80.degree. C. of the cell temperature. The
value of the current to the applied voltage is shown in FIG. 4.
When applying 1.6 V or above of voltage, a current flowed and the
reaction proceeded. As the voltage was increased to 2.2 V, the
current increased and the reaction proceeded. When the cathode
emission gas was analyzed by gas chromatography, toluene and
methylcyclohexane were detected. Hereby, it was confirmed that
methylcyclohexane was yielded by hydrogenation of toluene. FIG. 5
shows the conversion ratio of toluene to methylcyclohexane,
calculated from the peak intensity of gas chromatography. As the
voltage was increased, the conversion ratio was improved, and the
maximum value in this condition was 55% when applying 2.2 V.
[0057] As mentioned above, according to the example, a membrane
electrode assembly and an organic hydride manufacturing device
capable of obtaining higher energy efficiency can be provided by
introducing functional groups, which decrease wettability of
unsaturated hydrocarbons, on the carrier surface of a catalyst even
if organic hydride is manufactured with a single device in one
step.
First Comparative Example
[0058] As a catalyst, a catalyst was used where 30% (wt) of Pt
particulates was dispersed and supported on carbon black for which
surface treatment to introduce functional groups was not conducted.
This catalyst was used as cathode catalyst to prepare MEA. The
preparation was conducted in the method and condition for the
preparation similar to those of First Example.
[0059] The prepared MEA was incorporated into the device of
manufacturing organic hydride in FIG. 1, and the experiment of
hydrogenation of toluene in similar condition to First Example was
conducted. FIG. 6 shows a value of the current to the applied
voltage. The value of the current was smaller than that of First
Example. This is considered to be because the wettability of
toluene to carbon was strong, toluene was stagnated on the carbon
surface, and the supply of toluene onto catalyst was prevented.
Furthermore, when the occurred gas flow rate was measured, the gas
flow rate was increased in First Comparative Example in comparison
with First Example. This is considered to be because, on the
catalyst where toluene is not supplied, hydrogen generation occurs
by the reaction according to the following formula (3)
2H.sup.++2e.sup.-.fwdarw.H.sub.2 (3)
[0060] FIG. 7 shows the conversion ratio of toluene to
methylcyclohexane. The maximum value in this condition was 30% when
applying 2.2 V. It was a lower conversion ratio than that of First
Example. This is considered to be because not only hydrogenation
but also hydrogen generation occurs simultaneously. The energy
efficiency of organic hydride production can be lower to that
extent.
[0061] As mentioned above, even if there is a similar configuration
to First Example except for the introduction of functional groups,
a membrane electrode assembly and an organic hydride manufacturing
device which have higher energy efficiency cannot be obtained.
Second Embodiment
[0062] As a catalyst, a catalyst where 30% (wt) of Pt particulates
was dispersed and supported on carbon black was used. 10 g of this
catalyst and 15 g of anhydrous aluminum chloride (AlCl.sub.3) were
mixed and thiophosphoryl chloride (PSCl.sub.3) was added gradually.
The temperature of PSCl.sub.3 was fixed at 35.degree. C. and 54 mL
was added slowly. Subsequently, it was kept at 75.degree. C. for 45
minutes. After cooling, 50 mL of chloroform was added and
filtrated. After washing with diethyl ether thoroughly, 200 mL of
ion-exchanged water was added and refluxed for 20 hours. When the
infrared absorption spectrum of the obtained catalyst was measured,
the peaks were observed at 1000 to 1120 cm.sup.-1 and 840 to 910
cm.sup.-1. This was considered as the peak based on phosphonate,
and it was confirmed that phosphonate groups were introduced onto
the surface of the carrier carbon black. The equivalent of the
introduced phosphonate groups was 1.8 milliequivalent/g dry carbon
carrier.
[0063] The prepared catalyst was used for cathode catalyst to
prepare an MEA. The preparation was conducted in the method and
condition for the preparation similar to those of First
Example.
[0064] The prepared MEA was incorporated into the device of
manufacturing organic hydride in FIG. 1, and the experiment of
hydrogenation of toluene was conducted in the similar condition to
First Example. The result is shown in FIG. 8. FIG. 8 is the current
density and the conversion ratio when applying 2.2 V between the
anode and the cathode. Compared to First Comparative Example in
which surface treatment of carrier carbon was not conducted, it
resulted in an increase of both the current density and the
conversion ratio, and the effect of introducing phosphonate groups
onto the carbon surface was found.
[0065] As mentioned above, according to the example, a membrane
electrode assembly and an organic hydride manufacturing device
capable of obtaining higher energy efficiency can be provided by
introducing functional groups, which decrease wettability of
unsaturated hydrocarbons, on the carrier surface of catalyst even
if organic hydride is manufactured with a single device in one
step.
Third Example
[0066] As a catalyst, a catalyst where 30 wt % of Pt particulates
was dispersed and supported on carbon black was used. Oxygen plasma
was irradiated to this catalyst. The device to use for irradiation
was a plasma device, Cat. No. PDC210 manufactured by Yamato Glass,
and the pressure in the chamber before introducing oxygen was 0.1
Torr or lower, and the pressure after introducing oxygen was 0.5
Torr. The output of a high frequency power source of the device was
100 W, and plasma irradiation time was 150 seconds. When infrared
absorption spectrum of the yielded catalyst was measured, a broad
peak was observed at 3000 to 3600 cm.sup.-1. This was considered as
the peak based on the hydroxyl group --OH, and it was confirmed
that the hydroxyl group was introduced on the surface of Pt
supported carbon black.
[0067] The prepared catalyst was used for cathode catalyst to
prepare an MEA. The preparation was conducted in the method and
condition for the preparation similar to those of First
Example.
[0068] The prepared MEA was incorporated into the device of
manufacturing organic hydride in FIG. 1, and the experiment of
hydrogenation of toluene in the similar condition to First Example.
The result is shown in FIG. 8. Compared to First Comparative
Example in which surface treatment of carrier carbon was not
conducted, it resulted in an increase of both the current density
and the conversion ratio, and the effect of introducing hydroxyl
groups onto the carbon surface was found.
[0069] As mentioned above, according to the example, a membrane
electrode assembly and an organic hydride manufacturing device
capable of obtaining higher energy efficiency can be provided by
introducing functional groups, which decrease wettability of
unsaturated hydrocarbons, on the carrier surface of catalyst even
if organic hydride is manufactured with a single device in one
step.
[0070] However, the present invention is not limited the
above-mentioned examples, and various modifications are included.
For example, the above-mentioned examples are explained in detail
to explain the present invention simply, and not necessarily
limited to that provides all the configurations explained. In
addition, it is also possible to substitute part of the
configuration of one example with configuration of another example,
and moreover, it is also possible to add, to the configuration of
one example, the configuration of another example. Furthermore, for
part of the configuration of each example, it is possible to make
addition, deletion, or substitution of another configuration.
* * * * *