JP2006278197A - Cooling liquid composition for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling liquid composition for a fuel cell in which increase of conductivity due to oxidation of a base material is small even in a long-term use and in which the initial conductivity can be maintained. <P>SOLUTION: Because the cooling liquid composition for the fuel cell has at least one nitrogen atom in a molecule, and because at least one nitrogen atom contains in which atomic groups composed of (a) hydrocarbon of which the carbon number constituting the main chain is 3 or more and its derivative, or (b) amino alcohol or amino phenol of which the carbon number constituting the main chain is 2 or more and to which atomic groups composed of hydrocarbon and its derivative containing a hetero atom are bonded, increase of conductivity of the cooling liquid due to oxidation of the base material is effectively suppressed, and the initial conductivity can be maintained even when it is used over a long period. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coolant composition used for cooling a fuel cell, particularly an automobile fuel cell. More specifically, the present invention relates to a fuel cell coolant composition capable of maintaining the initial conductivity with little increase in conductivity due to oxidation of the base material even after long-term use.

  A fuel cell is generally configured as a stack having a structure in which a large number of single cells as power generation units are stacked. Since heat is generated from the stack during power generation, a cooling plate is inserted every several cells to cool the stack. A cooling fluid passage is formed inside the cooling plate, and the stack is cooled by flowing the cooling fluid through the passage.

  In this way, the coolant of the fuel cell circulates in the stack that is generating power to cool the stack, so if the electrical conductivity of the coolant is high, the electricity generated in the stack will move to the coolant side. It flows and loses electricity, and the power generation in the fuel cell is reduced. Therefore, pure water having low electrical conductivity, in other words, high electrical insulation, has been used as a conventional fuel cell coolant.

  However, for example, when considering a fuel cell for automobiles and a fuel cell for household cogeneration systems, the cooling liquid is lowered to the ambient temperature during non-operation. In particular, when there is a possibility of use below freezing point, there is a possibility that the battery performance of the fuel cell is impaired, such as freezing in pure water and damage to the cooling plate due to volume expansion of the coolant.

Under such circumstances, it is conceivable to use bases such as glycols and alcohols for the purpose of antifreezing in the fuel cell coolant. Conventionally, a coolant composition for a fuel cell has been proposed that includes a base composed of, for example, a mixed solution of water and glycols, and an amine-based alkaline additive that maintains the conductivity of the coolant at a low conductivity (patent) Reference 1).
JP 2001-164244 A

  However, in the conventional fuel cell coolant composition, glycols and alcohols used as a base in the coolant are oxidized during fuel cell operation to produce an ionic substance. For this reason, when used for a long period of time, the amount of the ionic substance in the cooling liquid increases, and as a result, there is a possibility that the initial conductivity cannot be maintained.

  The present invention has been made in view of such circumstances, and provides a coolant composition for a fuel cell in which the increase in conductivity due to oxidation of the base is small and the initial conductivity can be maintained over a long period of time. It is intended to provide.

  The fuel cell coolant composition (hereinafter simply referred to as composition) of the present invention has at least one nitrogen atom in the molecule, and at least one nitrogen atom includes the following (a) or (b): It is characterized by containing amino alcohols or aminophenols to which the atomic group is bonded.

(A) a hydrocarbon having 3 or more carbon atoms constituting the main chain and its derivative,
(B) A hydrocarbon having 2 or more carbon atoms constituting the main chain and containing a hetero atom and derivatives thereof.

  The composition of the present invention contains amino alcohols or aminophenols having at least one nitrogen atom in the molecule and having the atomic group (a) or (b) bonded to at least one nitrogen atom. Therefore, the increase in the conductivity of the coolant due to the oxidation of the base is effectively suppressed, and the initial conductivity is maintained even when used for a long time.

  As the base in the composition of the present invention, those having low electrical conductivity and non-freezing properties are desirable. Specifically, those composed of one or a mixture of two or more selected from water, alcohols, glycols, and glycol ethers are desirable.

  Examples of the alcohols include those composed of one or a mixture of two or more selected from methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, and octanol.

  Examples of glycols include one selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, and hexylene glycol, or The thing which consists of 2 or more types of mixtures can be mentioned.

  Examples of glycol ethers include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monomethyl ether. Mention may be made of one or a mixture of two or more selected from ethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and tetraethylene glycol monobutyl ether.

  Among the above bases, ethylene glycol and / or propylene glycol are preferable from the viewpoints of handleability, cost, and availability.

  In the above base, the hydrocarbon having at least one nitrogen atom in the molecule, and (a) a hydrocarbon having 3 or more carbon atoms constituting the main chain at least one nitrogen atom and its derivative, or (b) Amino alcohols or aminophenols having 2 or more carbon atoms constituting the main chain and bonded with an atomic group comprising a hydrocarbon containing a hetero atom and a derivative thereof are included. The atomic group (a) or (b) bonded to the nitrogen atom in these amino alcohols or amino phenols consists of a saturated chain hydrocarbon or unsaturated chain hydrocarbon, and a cyclic hydrocarbon. And things. The number of carbon atoms contained in these atomic groups (a) and (b) is preferably 20 or less, particularly 2 to 10 carbon atoms. Examples of the hetero atom in the amino alcohol or amino phenol to which the atomic group (b) is bonded include a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, a silicon atom, a boron atom, and a fluorine atom. Is a nitrogen atom.

  These amino alcohols or aminophenols are excellent in oxidation inhibiting function, so that these amino alcohols or aminophenols are contained in the base, and the composition is diluted with water to a predetermined concentration. In this case, the increase in the conductivity of the coolant due to the oxidation of the base is effectively suppressed, and the initial conductivity of the coolant is stopped within a slight fluctuation range and maintained.

  Among aminoalcohols or aminophenols having such effects, those having 1 to 3 nitrogen atoms in the molecule are desirable because of their excellent oxidation-inhibiting function. Further, from the viewpoint of easy solubility in the base, amino alcohols or aminophenols having 20 or less, particularly 2 to 10 carbon atoms, contained in the atomic group bonded to the nitrogen atom in the molecule are desirable. Structurally, it is desirable that the atomic group bonded to the nitrogen atom in the molecule has a saturated chain structure or an unsaturated chain structure, particularly a hydrocarbon having a straight chain structure.

  Examples of amino alcohols in which the atomic group bonded to the nitrogen atom has a saturated chain structure include aminopropanol, aminomethylpropanol, dimethylaminopropanol, aminoethylpropanol, diethylaminopropanol, aminopropanediol, aminomethylpropanediol, and aminoethyl. Propanediol, aminohydroxymethylpropanediol, (dimethylamino) propanediol, aminobutanol, aminomethylbutanol, dimethylaminobutanol, aminoethylbutanol, aminopentanol, aminohexanol, aminoheptanol, aminooctanol, dimethylaminooctanol, ( Aminoethylamino) ethanol, (aminoethylamino) propanol, aminoethoxyethanol, (t rt- butylamino) ethanol, can include any one or a mixture of two or more selected from the group consisting of diethylamino-ethoxy ethanol.

  Examples of amino alcohols in which the atomic group bonded to the nitrogen atom has an unsaturated chain structure include aminopropenol, methylaminopropenol, aminopropinol, methylaminopropinol, aminobutenol, methylaminobutenol, amino Mention may be made of any one kind or a mixture of two or more kinds selected from the group consisting of butynol, methylaminobutynol, dimethylaminobutynol, and diethylaminobutynol.

  Examples of aminophenols in which the atomic group bonded to the nitrogen atom has a cyclic structure include (benzylamino) ethanol, aminobenzylethanol, (methylaminomethyl) benzyl alcohol, aminocyclohexanol, aminophenylethanol, aminophenylpropanol, Examples include one or a mixture of two or more selected from the group consisting of aminocresol, aminonaphthol, aminophenol, aminonitrophenol, aminomethylphenol, dimethylaminophenol, aminoethylphenol, and diethylaminophenol. .

  The content of amino alcohols or aminophenols is preferably in the range of 0.001 to 20 parts by weight with respect to 100 parts by weight of the base. When the content of amino alcohols or aminophenols is lower than the above range, sufficient base oxidation inhibition effect cannot be obtained, and when the content of amino alcohols or aminophenols exceeds the above range, , The effect of only the content can not be expected, uneconomical.

  In addition, in the composition of this invention, the form which uses the said amino alcohols or aminophenols as a base can also be taken. In this case, the base itself is difficult to oxidize and has a function of suppressing an increase in the conductivity of the coolant due to oxidation.

  The composition of the present invention may contain at least one corrosion inhibitor as long as it does not affect conductivity in order to effectively suppress corrosion of the metal used in the fuel cell. it can.

  Corrosion inhibitors include phosphoric acid and / or salts thereof, aliphatic carboxylic acids and / or salts thereof, aromatic carboxylic acids and / or salts thereof, triazoles, thiazoles, silicates, nitrates, nitrites, borates, Any one or a mixture of two or more of molybdate and amine salts can be mentioned.

  Examples of phosphoric acid and / or salts thereof include orthophosphoric acid, pyrophosphoric acid, hexametaphosphoric acid, tripolyphosphoric acid, and alkali metal salts thereof, preferably sodium salts and potassium salts.

  Examples of aliphatic carboxylic acids and salts thereof include pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, 2-ethylhexanoic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanoic acid, Examples include dodecanedioic acid and alkali metal salts thereof, preferably sodium salt and potassium salt.

  Aromatic carboxylic acids and / or salts thereof include benzoic acid, toluic acid, para-tert-butylbenzoic acid, phthalic acid, paramethoxybenzoic acid, cinnamic acid, and alkali metal salts thereof, preferably sodium salt and potassium salt. Can be mentioned.

  Examples of triazoles include benzotriazole, methylbenzotriazole, cyclobenzotriazole, and 4-phenyl-1,2,3-triazole.

  Examples of thiazoles include mercaptobenzothiazole and alkali metal salts thereof, preferably sodium salt and potassium salt.

Examples of silicates include sodium and potassium salts of metasilicate and an aqueous solution of sodium silicate represented by Na ₂ O / XSiO ₂ (X is 0.5 to 3.3) called water glass. Examples of the nitrate include sodium nitrate and potassium nitrate, and examples of the nitrite include sodium nitrite and potassium nitrite. Examples of the borate include sodium tetraborate and potassium tetraborate.

  Examples of molybdate include sodium molybdate, potassium molybdate, and ammonium molybdate.

  In addition, for example, a pH adjusting agent such as sodium hydroxide or potassium hydroxide, an antifoaming agent, or a coloring agent can be appropriately added to the composition of the present invention as long as the electrical conductivity is not affected.

  In addition, this invention is not limited to the following Example, It can implement freely by changing in the range described in the "Claims".

  Hereinafter, the preferable example of the composition of this invention is given and the performance is evaluated, contrasting with a comparative example. Table 1 lists the compositions of Examples 1 to 5 and Comparative Examples 1 to 5. Each of the compositions of Examples 1 to 5 and Comparative Examples 1 to 5 is based on ion-exchanged water and ethylene glycol, and the one obtained by adding 2-amino-1-phenylethanol to this base was carried out. In Example 1, 2-amino-2-methyl-1-propanol was added as Example 2, 4-amino-1-butanol was added as Example 3, and 6-amino-1-hexanol was added. The product was Example 4 and 2- (2-aminoethylamino) ethanol was used as Example 5.

  On the other hand, the above-mentioned base alone was used as Comparative Example 1, the base added with benzyl alcohol in Comparative Example 2, the acetonitrile added with Comparative Example 3, and the 1-propanol added with Comparative Example Comparative Example 5 was obtained by adding 4,2-aminoethanol.

表１に示す実施例１〜５並びに比較例１〜５の各組成物について、酸化劣化後の酸の生成量を測定した。その結果を表２に示した。尚、各組成物の酸化劣化は、１００℃で５００時間の条件で実施した。

About each composition of Examples 1-5 shown in Table 1, and Comparative Examples 1-5, the production amount of the acid after oxidation deterioration was measured. The results are shown in Table 2. The oxidative deterioration of each composition was performed at 100 ° C. for 500 hours.

表２から、酸化劣化後の酸の生成量を見たとき、基剤のみの比較例１の酸の生成量が２２となっているのに対し、比較例２〜４の酸の生成量は１８〜２７となっており、実質上、比較例１の組成物と比較例２〜４の各組成物の性能はほとんど同じか、むしろ悪くなるという結果が得られた。比較例５の酸の生成量については１０となっており、酸の生成が幾分抑えられていると考えられる。これに対し、実施例１〜５の各組成物の場合、それらの酸の生成量は測定困難又は２〜５と微量な量であり、酸の生成の抑制効果に優れることが確認された。

From Table 2, when the amount of acid produced after oxidative degradation was observed, the amount of acid produced in Comparative Example 1 with only the base was 22, whereas the amount of acid produced in Comparative Examples 2 to 4 was As a result, the performance of the composition of Comparative Example 1 and each composition of Comparative Examples 2 to 4 was substantially the same or rather deteriorated. The amount of acid produced in Comparative Example 5 was 10, and it is considered that the acid production was somewhat suppressed. On the other hand, in the case of each composition of Examples 1-5, the production amount of those acids is difficult or it is a very small amount with 2-5, and it was confirmed that it is excellent in the inhibitory effect of the production | generation of an acid.

Claims (8)

It contains at least one nitrogen atom in the molecule, and contains an amino alcohol or aminophenol to which an atomic group consisting of the following (a) or (b) is bonded to at least one nitrogen atom: A fuel cell coolant composition.
(A) a hydrocarbon having 3 or more carbon atoms constituting the main chain and its derivative,
(B) A hydrocarbon having 2 or more carbon atoms constituting the main chain and containing a hetero atom, and derivatives thereof. The fuel cell coolant composition according to claim 1, wherein the heteroatom in the amino alcohol or aminophenol is nitrogen. 3. The fuel cell coolant composition according to claim 1, wherein the number of nitrogen atoms in the molecule of the amino alcohol or aminophenol is 1 to 3. 4. The fuel cell coolant composition according to claim 1, wherein the atomic group bonded to the nitrogen atom in the molecule of the amino alcohol or aminophenol has 20 or less carbon atoms. 5. The fuel according to any one of claims 1 to 4, wherein the atomic group bonded to the nitrogen atom in the amino alcohol or aminophenol molecule is a saturated chain hydrocarbon or an unsaturated chain hydrocarbon. Battery coolant composition. The fuel cell coolant composition according to any one of claims 1 to 4, wherein the atomic group bonded to the nitrogen atom in the amino alcohol or aminophenol molecule is a cyclic hydrocarbon. The amino alcohol or aminophenol is contained in a base composed of any one kind or a mixture of two or more kinds selected from water, alcohols, glycols, and glycol ethers. The coolant composition for fuel cells according to any one of 1 to 6. The fuel cell coolant composition according to any one of claims 1 to 7, wherein the content of amino alcohols or aminophenols is 0.001 to 20 parts by weight with respect to 100 parts by weight of the base. object.