JP2006225423A - Preserving method of fuel for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preserving method of a fuel for fuel cells, capable of stably preserving the fuel for fuel cells. <P>SOLUTION: The fuel for fuel cells is stably preserved as a molecular compound. As the molecular compound an inclusion compound formed from the fuel for fuel cells and a host compound can be used. As the fuel cells preferable are polymer electrolyte fuel cells, particularly direct methanol fuel cells. The fuel for the fuel cells is preferably one or more selected from the group consisting of alcohols, ethers, hydrocarbons and acetals. The fuel for the fuel cells can have various forms such as the molecular compound is filled in a cartridge. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for storing fuel for a fuel cell, and more particularly to a fuel cell for operating a fuel cell on-site and generating electric power when power cannot be supplied due to a natural disaster such as an earthquake or a typhoon. The present invention relates to a fuel cell fuel storage method capable of storing fuel safely and stably.

A solid polymer electrolyte fuel cell has a solid electrolyte membrane such as a perfluorosulfonic acid membrane as an electrolyte, and a fuel electrode (anode) and an oxidant electrode (cathode) are joined to both sides of the membrane, and hydrogen is connected to the anode. It is a device that generates oxygen by electrochemical reaction by supplying oxygen to the cathode and methanol. The electrochemical reaction that occurs at each electrode, when methanol is used as the fuel,
CH ₃ OH + H ₂ O → 6H ⁺ + CO ₂ + 6e ⁻ (1)
And at the cathode,
3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O (2)
It is. In order to cause this reaction, both electrodes are composed of a mixture of carbon fine particles carrying a catalyst material and a solid polymer electrolyte.

  In such a solid polymer electrolyte fuel cell, when methanol is used as the fuel, the methanol supplied to the anode reaches the catalyst through the pores in the electrode, and the methanol is decomposed by the catalyst. Electrons and hydrogen ions are generated by the reaction of reaction formula (1). The hydrogen ions reach the cathode through the electrolyte in the anode and the solid electrolyte membrane between the two electrodes, react with oxygen supplied to the cathode and electrons flowing from the external circuit, and water in the reaction of the above reaction formula (2). Arise. On the other hand, electrons emitted from methanol are led to the external circuit through the catalyst carrier in the anode, and flow into the cathode from the external circuit. As a result, in the external circuit, electrons flow from the anode to the cathode and electric power is taken out.

  This direct methanol fuel cell using methanol as a fuel has a high possibility of being applicable as a portable small fuel cell, and in recent years, development has been activated as a next-generation secondary battery such as a portable computer or a mobile phone. In addition, this direct methanol fuel cell can supply a large amount of power for a long time when compared with a commercially available dry cell, so it can be generated on-site as power when a commercial power source becomes unavailable during a natural disaster such as an earthquake or typhoon. Because it is useful.

  However, hydrogen and methanol used as fuel for fuel cells are highly dangerous and have many problems in handling. In particular, as fuel for disasters and emergencies, it must be stocked for a long time or transported urgently, but since methanol is a dangerous substance, there is a limit to the amount that can be stored in one place and the transport amount. there were.

Specifically, methanol has the following problems. That is,
(1) The stock solution of methanol falls under the category of deleterious substances under the Poisonous and Deleterious Substances Control Law, and also falls under the Class 4 dangerous goods under the Fire Service Law. Can not do it.
(2) In order to solve the problem of the regulation (1) above, there is a method of storing as a methanol aqueous solution of about 1 to 30% by mass, but there is a possibility of freezing in an aqueous solution of this concentration, There is a problem that the storage container bursts and it takes time to defrost, and it is not suitable for stockpiling in cold regions.
(3) Since both methanol and aqueous methanol solution are liquids, it is necessary to provide a highly airtight container that does not leak.

  Therefore, a technology for safely storing methanol as a fuel as a non-hazardous material in order to stockpile and transport without safety and legal restrictions has been demanded.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell fuel storage method capable of stably storing fuel cell fuel.

  The fuel cell fuel storage method for fuel cell fuel according to the present invention is characterized in that the fuel cell fuel is stably stored as a molecular compound (claim 1). As a result, when power cannot be supplied from a commercial power source, the molecular compound is brought into contact with water or an aqueous fuel solution to release fuel for the fuel cell, and the fuel cell is operated on-site to generate power. Can do.

  In particular, the molecular compound is preferably stored in a cartridge (claim 2). As a result, the fuel cell fuel can be stored in a state where functions such as detachable to the fuel cell and supply of the fuel cell fuel little by little are provided, and further the storage stability and transportation of the fuel cell fuel. Can greatly improve the performance.

  The fuel cell fuel storage method of the present invention can be suitably applied to solid polymer fuel cells, particularly direct methanol fuel cells (claims 3 and 4).

  The fuel cell fuel storage method of the present invention is particularly suitable for portable small fuel cells. When applied to a portable small fuel cell, the fuel can be easily carried along with the fuel cell itself as a power source, which is suitable as an emergency power source.

  The fuel for the fuel cell is one or more selected from the group consisting of alcohols, ethers, hydrocarbons, and acetals (Claim 6). These fuels can be molecular compounds and are suitable for applying the preservation method of the present invention.

  The molecular compound of the fuel cell fuel is an inclusion compound formed from the fuel cell fuel and a host compound (Claim 7). By making the host compound clathrate the fuel to form an clathrate compound, the fuel for the fuel cell can be released by contact with water or an aqueous fuel solution.

  The host compound may be supported on a porous material (Claim 8), or one or more selected from the group consisting of an organic compound, an inorganic compound, and an organic / inorganic composite compound (Claim 9), Alternatively, one or more selected from the group consisting of a monomolecular system, a polymolecular system, and a polymer host compound can be used (claim 10).

  According to the present invention, fuel for fuel cells can be stored relatively easily and lightly under conditions close to normal temperature and normal pressure. In addition, many fuels for fuel cells are designated as dangerous or deleterious substances. However, according to the method of the present invention, the flash point of the fuel for fuel cells can be raised, and the fuel cell is highly safe. It can be stored as a fuel. Moreover, the fuel for the fuel cell stored by the method of the present invention can be easily supplied without heating. Furthermore, since the liquid component does not coexist by filling the cartridge with the molecular compound containing the fuel for the fuel cell, the liquid does not leak during carrying.

For example, when methanol is taken as an example of the fuel for the fuel cell, the following effects can be obtained. That is,
(1) When stocking methanol, the designated quantity that can be stocked is determined from the danger, but it can be stocked avoiding this restriction.
(2) When stockpiling as an aqueous methanol solution, there are problems such as rupture of the container due to freezing and thawing in cold regions, but these problems can be avoided.
(3) Since methanol and aqueous methanol solution are liquids, it is necessary to prepare a highly airtight container without liquid leakage when stockpiling, but this liquid leakage problem can also be avoided.
In addition, although the effect of this invention was demonstrated above by taking methanol as an example, it cannot be overemphasized that the same effect can be anticipated also with the fuel for other fuel cells.

Hereinafter, the fuel cell fuel storage method of the present invention will be described in detail.
Examples of the fuel for the fuel cell in the present invention include hydrogen, alcohols, ethers, hydrocarbons, and acetals. However, any fuel can be used as long as it can be used as a fuel for a polymer electrolyte fuel cell. Is not to be done. Specifically, hydrogen; alcohols such as methanol, ethanol, n-propanol, isopropanol, and ethylene glycol; ethers such as dimethyl ether, methyl ethyl ether, and diethyl ether; hydrocarbons such as propane and butane; dimethoxymethane, trimethoxy Examples include, but are not limited to, acetals such as methane, and these may be used alone or in admixture of two or more.

  The form of the fuel cell is preferably a polymer electrolyte fuel cell. As the polymer electrolyte fuel cell, a direct methanol fuel cell is the most representative, but is not limited thereto. Absent.

  In the present invention, the molecular compound is a compound in which two or more kinds of compounds that can exist stably alone are bonded by a relatively weak interaction other than a covalent bond typified by a hydrogen bond or van der Waals force. And includes hydrates, solvates, addition compounds, inclusion compounds, and the like. Such a molecular compound can be formed by a contact reaction between the compound forming the molecular compound and the fuel for the fuel cell, and the fuel for the fuel cell can be changed into a solid compound, which is relatively light and stable. In addition, fuel for fuel cells can be stored.

  As such a molecular compound, an inclusion compound in which a fuel cell fuel is included by a contact reaction between a host compound and a fuel cell fuel is preferable.

  Among molecular compounds, host compounds that form an inclusion compound that includes a fuel for a fuel cell are known, and organic compounds, inorganic compounds, and organic / inorganic composite compounds are known. Molecular, multimolecular, and polymeric host compounds are known.

  Monomolecular host compounds include cyclodextrins, crown ethers, cryptands, cyclophanes, azacyclophanes, calixarenes, cyclotriveratrylenes, spherands, cyclic oligopeptides, etc. . Examples of the multi-molecular host compound include ureas, thioureas, deoxycholic acids, cholic acids, perhydrotriphenylenes, tri-o-thymotides, beanthryls, spirobifluorenes, cyclophosphazenes, Monoalcohols, diols, hydroxybenzophenones, acetylene alcohols, phenols, bisphenols, trisphenols, tetrakisphenols, polyphenols, naphthols, bisnaphthols, diphenylmethanols, carboxylic acid amides, thioamides , Bixanthenes, carboxylic acids, imidazoles, hydroquinones and the like. Further, examples of the polymeric host compound include celluloses, starches, chitins, chitosans, polyvinyl alcohols, polyethylene glycol arm polymers having 1,1,2,2-tetrakisphenylethane as a core, α, Examples include polyethylene glycol arm type polymers having α, α ′, α′-tetrakisphenylxylene as a core. In addition, organophosphorus compounds, organosilicon compounds, and the like are also included.

  Examples of inorganic host compounds include titanium oxide, graphite, alumina, transition metal dicargogenite, lanthanum fluoride, clay minerals (such as montmorillonite), silver salts, silicates, phosphates, zeolites, silica, and porous glass. It is done.

  Furthermore, some organometallic compounds exhibit properties as host compounds. For example, organoaluminum compounds, organotitanium compounds, organoboron compounds, organozinc compounds, organoindium compounds, organogallium compounds, organotellurium compounds, organotin compounds. , Organic zirconium compounds, and organic magnesium compounds. Further, a metal salt of an organic carboxylic acid, an organic metal complex, or the like can be used. However, the organic carboxylic compound is not particularly limited as long as it is an organic metal compound.

  Of these host compounds, multi-molecular host compounds whose inclusion ability is less influenced by the molecular size of the guest compound are more effective.

  Specific examples of the multimolecular host compound include urea, 1,1,6,6-tetraphenylhexa-2,4-diyne-1,6-diol, and 1,1-bis (2,4-dimethyl). Phenyl) -2-propyn-1-ol, 1,1,4,4-tetraphenyl-2-butyne-1,4-diol, 1,1,6,6-tetrakis (2,4-dimethylphenyl)- 2,4-hexadiyne-1,6-diol, 9,10-diphenyl-9,10-dihydroanthracene-9,10-diol, 9,10-bis (4-methylphenyl) -9,10-dihydroanthracene- 9,10-diol, 1,1,2,2-tetraphenylethane-1,2-diol, 4-methoxyphenol, 2,4-dihydroxybenzophenone, 4,4′-dihydroxybenzophenone, 2 2'-dihydroxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4'-sulfonylbisphenol, 2,2'-methylenebis (4- Methyl-6-tert-butylphenol), 4,4′-ethylidenebisphenol, 4,4′-thiobis (3-methyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy) -5-t-butylphenyl) butane, 1,1,2,2-tetrakis (4-hydroxyphenyl) ethane, 1,1,2,2-tetrakis (4-hydroxyphenyl) ethylene, 1,1,2, 2-tetrakis (3-methyl-4-hydroxyphenyl) ethane, 1,1,2,2-tetrakis (3-fluoro-4-hydroxy) Phenyl) ethane, α, α, α ′, α′-tetrakis (4-hydroxyphenyl) -p-xylene, 3,6,3 ′, 6′-tetramethoxy-9,9′-bi-9H-xanthene, 3,6,3′6′-tetraacetoxy-9,9′-bi-9H-xanthene, 3,6,3 ′, 6′-tetrahydroxy-9,9′-bi-9H-xanthene, gallic acid, Methyl gallate, catechin, bis-β-naphthol, α, α, α ′, α′-tetraphenyl 1,1′-biphenyl-2,2′-dimethanol, diphenic acid bis (dicyclohexylamide), fumarate bis (Dicyclohexylamide), cholic acid, deoxycholic acid, 1,1,2,2-tetrakis (4-carboxyphenyl) ethane, 1,1,2,2-tetrakis (3-carboxyphenyl) ethane, acetylene Dicarboxylic acid, 2,4,5-triphenylimidazole, 1,2,4,5-tetraphenylimidazole, 2-phenylphenanthro [9,10-d] imidazole, 2- (o-cyanophenyl) phenanthro [9,10-d] imidazole, 2- (m-cyanophenyl) phenanthro [9,10-d] imidazole, 2- (p-cyanophenyl) phenanthro [9,10-d] imidazole, hydroquinone, 2-t -Butylhydroquinone, 2,5-di-t-butylhydroquinone, 2,5-bis (2,4-dimethylphenyl) hydroquinone and the like, such as 1,1-bis (4-hydroxyphenyl) cyclohexane A phenolic host compound is advantageous in that it is easy to use industrially.

  These host compounds may be used individually by 1 type, and may use 2 or more types together. These host compounds may be any shape compounds as long as they form a solid clathrate compound with the fuel for the fuel cell.

  The organic host compound described above can also be used as an organic / inorganic composite material supported on an inorganic porous material. In this case, examples of the porous material supporting the organic host compound include intercalation compounds such as clay minerals and montmorillonites in addition to silicas, zeolites and activated carbons, but are not limited thereto. Absent. As a method for producing such an organic / inorganic composite material, the aforementioned organic host compound is dissolved in a solvent that can be dissolved, the solution is impregnated in an inorganic porous material, the solvent is dried, and dried under reduced pressure, etc. Can be manufactured. Although there is no restriction | limiting in particular as the load of the organic host compound with respect to an inorganic porous material, Usually, it is about 10-80 mass% with respect to an inorganic porous material.

  As a method of synthesizing a fuel cell fuel clathrate compound using a host compound such as 1,1-bis (4-hydroxyphenyl) cyclohexane described above, the fuel cell fuel and the host compound are directly contacted and mixed. It can also be easily synthesized by a method of dissolving the host compound in a heated fuel cell fuel and recrystallizing it. Further, when the fuel for the fuel cell is gas or liquid, it can be obtained by contacting the fuel with the host compound in a pressurized state.

  The temperature at which the fuel for the fuel cell is brought into contact with the host compound is not particularly limited, but is preferably from room temperature to about 100 ° C.

  The time for contacting the fuel cell fuel with the host compound is not particularly limited, but is preferably about 0.01 to 24 hours from the viewpoint of work efficiency.

  The fuel for the fuel cell to be brought into contact with the host compound is preferably a high-purity fuel. However, when a host compound having the selective inclusion ability of the fuel for the fuel cell is used, the fuel for the fuel cell and other components are used. And a mixed liquid.

  The clathrate compound thus obtained varies depending on the type of the host compound used, the contact conditions with the fuel for the fuel cell, etc., but usually 0.1 to 10 fuel molecules for the fuel cell per mole of the host compound. It is an clathrate compound that clathrates a mole.

  The clathrate compound thus obtained can stably store fuel for fuel cells over a long period of time in a normal temperature / normal pressure environment. Moreover, since this inclusion compound is lightweight and excellent in handleability and is solid, it can be easily stored in a container such as glass, metal, plastic, etc., and the problem of liquid leakage is also eliminated. . In addition, since the liquid fuel is usually solidified by inclusion, the property as a deleterious substance or a dangerous substance can be avoided. Furthermore, the chemical reactivity of the fuel for the fuel cell can be reduced, and for example, the corrosiveness to metals can be alleviated.

  The clathrate containing the fuel cell fuel as described above is detachable from the fuel cell and stored in a cartridge-type container having a function of supplying the fuel cell fuel little by little. May be.

  In the fuel cell fuel storage method of the present invention, as a method of removing the fuel cell fuel from the state in which the fuel cell fuel is stored by using the clathrate compound, a solid clathrate compound of the fuel cell fuel is used. It can be taken out by bringing water or a fuel aqueous solution for a fuel cell into contact with each other and releasing the fuel for the fuel cell in the clathrate compound to the water or the fuel aqueous solution for the fuel cell. Moreover, the fuel for fuel cells can be taken out by heating the solid clathrate compound of the fuel for fuel cells.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

[Example 1]
By re-dissolving 26.8 g (0.1 mol) of 1,1-bis (4-hydroxyphenyl) cyclohexane (BHC) in 50 mL of methanol at 60 ° C., BHC: methanol = 1: 1 (mol) Ratio) solid methanol clathrate compound (methanol content = 10.6% by mass).

  About this clathrate compound, the flash point was 94 degreeC as a result of having performed the test twice with the seta sealing type flash point evaluation apparatus. The flash point when methanol is stored as a stock solution is 11 ° C, and since methanol belongs to the Class 4 dangerous substances (flammable liquid) alcohol of the Fire Service Act, the specified quantity is up to 400L. Since it is made into a solid powder by using the above clathrate compound, it does not become a dangerous substance class 4, and since the flash point could be raised to 94 ° C, both the dangerous substance class 2 (flammable solid) of the Fire Service Act However, as a result, it became clear that stock can be stored without restriction of the specified quantity of these regulations.

[Example 2]
By performing recrystallization by dissolving 39.8 g (0.1 mol) of 1,1,2,2-tetrakis (4-hydroxyphenyl) ethane (THPE) in 100 mL of methanol at 60 ° C., THPE: methanol = 1 : 2 (molar ratio) to obtain a solid methanol clathrate compound (methanol content 14% by mass).

About this clathrate compound, the flash point was 75 degreeC as a result of having performed the test twice with the seta sealing type flash point evaluation apparatus. The flash point when stocking methanol with stock solution is 11 ° C and belongs to the Class 4 (flammable liquid) dangerous substances of the Fire Service Act, so the specified quantity is up to 400L. Since it is made into a solid powder by making it into a compound, it does not become a dangerous substance class 4, and since the flash point could be raised to 75 ° C, it does not become a dangerous substance class 2 (flammable solid) of the Fire Service Act, As a result, it became clear that stock can be stored without restriction of the specified quantity of these laws and regulations.

Claims (10)

  A fuel cell fuel storage method characterized by stably storing a fuel cell fuel as a molecular compound.   2. The fuel cell fuel storage method according to claim 1, wherein the molecular compound is filled in a cartridge.   3. The fuel cell fuel storage method according to claim 1, wherein the fuel cell is a polymer electrolyte fuel cell.   4. The fuel cell fuel storage method according to claim 3, wherein the polymer electrolyte fuel cell is a direct methanol fuel cell.   5. The fuel cell fuel storage method according to claim 1, wherein the fuel cell is a portable small fuel cell.   6. The fuel cell fuel according to claim 1, 2, 3 or 5, wherein the fuel for the fuel cell is one or more selected from the group consisting of alcohols, ethers, hydrocarbons, and acetals. Fuel cell storage method.   The fuel cell fuel storage according to any one of claims 1 to 6, wherein the molecular compound of the fuel cell fuel is an inclusion compound formed from the fuel cell fuel and a host compound. Method.   The fuel cell fuel storage method according to claim 7, wherein the host compound is supported on a porous material.   9. The fuel cell fuel storage method according to claim 7, wherein the host compound is one or more selected from the group consisting of an organic compound, an inorganic compound, and an organic / inorganic composite compound. The fuel cell according to any one of claims 7 to 9, wherein the host compound is one or more selected from the group consisting of a monomolecular system, a polymolecular system, and a polymer host compound. How to save fuel.