JP2008059990A - Cooling liquid composition for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling liquid composition for a fuel cell with little rise of conductivity due to oxidation of a base agent even after a long-term use and capable of maintaining initial conductivity. <P>SOLUTION: The cooling liquid composition for a fuel cell contains cyclo alkylamine or its derivative, so that rise of conductivity of the cooling liquid due to oxidation of a base agent is effectively suppressed, and initial conductivity can be maintained even in case of a long-term use. <P>COPYRIGHT: (C)2008,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 of the present invention (hereinafter simply referred to as a composition) is characterized by containing a cyclic compound, cycloalkylamine, or a derivative thereof.

  Since the composition of the present invention contains a cycloalkylamine or a derivative thereof, the cycloalkylamine or a derivative thereof suppresses the oxidation of the base, and the increase in the conductivity of the coolant due to the oxidation of the base is effective. Even when used over a long period of time, the initial conductivity can be maintained.

  As the base used in the composition of the present invention, those having low electrical conductivity and having antifreezing 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 monoethyl 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.

  The above base contains cycloalkylamine or a derivative thereof. Cycloalkylamine is an antioxidant, and by containing it in the base, the oxidation of the base is effectively suppressed, and the production of ionic substances due to the oxidation of the base is suppressed. For this reason, even if it is used for a long time, the amount of the ionic substance in the cooling liquid can be reduced, and as a result, the initial conductivity is maintained.

  Examples of cycloalkylamines or derivatives thereof having such effects include methylcyclopropanamine, aminocyclopropanecarboxylic acid, methylcyclopentylamine, cyclohexanediamine, cyclohexylhydroxylamine, methylcyclohexylamine, dimethylcyclohexylamine, and trimethylcyclohexylamine. , Aminomethyltrimethylcyclohexylamine, hydroxymethylcyclohexylamine, ethylcyclohexylamine, ethynylcyclohexylamine, diethylcyclohexylamine, hydroxyethylcyclohexylamine, isopropylcyclohexylamine, cyclohexylpropanediamine, allylcyclohexylamine, butylhexylamine, diacetylcyclohexanediamine , Cyclohexanediamine tetraacetic acid, dicyclohexylamine, methyl dicyclohexylamine, di cycloheptylamine, and the like can be illustrated cyclooctyl hydroxyethylamine, it can be used in the form of these one or two or more thereof. Among the above cycloalkylamines or derivatives thereof, cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, cyclooctylamine, and cyclododecylamine having 3 to 12 carbon atoms are excellent in oxidation-inhibiting effect and are easy to handle and obtain. It is more preferable in terms of ease.

  The content of cycloalkylamine or a derivative thereof is preferably in the range of 0.001 to 20 parts by weight, more preferably 0.001 to 15 parts by weight with respect to 100 parts by weight of the base. 01 to 10 parts by weight. When the content of cycloalkylamine or a derivative thereof is less than 0.001 part by weight with respect to 100 parts by weight of the base, a sufficient base oxidation inhibition effect cannot be obtained, and when the content exceeds 20 parts by weight. However, it is not possible to expect the effect of suppressing oxidation just exceeding the value, which is uneconomical.

  In addition, the composition of the present invention can contain at least one or more types of corrosion inhibitors as long as they do not affect the conductivity in order to effectively suppress the corrosion of the metal used in the fuel cell. .

  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.

  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".

  Hereafter, the preferable Example of the composition of this invention was given and the performance was evaluated, contrasting with a comparative example. Table 1 lists the compositions of Examples 1 to 3 and Comparative Examples 1 to 3. Each of the compositions of Examples 1 to 3 and Comparative Examples 1 to 3 is based on ion-exchanged water and ethylene glycol, and Example 1 was obtained by adding cyclohexylamine to this base. Example 2 was obtained by adding amine, and Example 3 by adding 1,2-cyclohexanediamine.

  On the other hand, Comparative Example 1 was obtained by adding only the above-mentioned base, Comparative Example 2 was obtained by adding ethanolamine to the above-mentioned base, and Comparative Example 3 was obtained by adding acetonitrile.

表１に示す実施例１〜３並びに比較例１〜３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３３６時間の条件で実施した。

About each composition of Examples 1-3 shown in Table 1, and Comparative Examples 1-3, the production amount of the acid after oxidative degradation was measured. The results are shown in Table 2. The oxidative deterioration of each composition was performed at 100 ° C. for 336 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１４、アセトニトリルを添加した比較例３の酸の生成量が１７となっているのに対し、エタノールアミンを添加した比較例２の酸の生成量は幾分抑えられて８となった。これに対し、環式化合物であるシクロアルキルアミン又はその誘導体を添加した実施例１〜３の各組成物の場合、それらの酸の生成量は３〜５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 14, and the amount of acid produced in Comparative Example 3 with the addition of acetonitrile was 17. On the other hand, the amount of acid produced in Comparative Example 2 to which ethanolamine was added was somewhat suppressed to 8. On the other hand, in the case of each composition of Examples 1 to 3 to which a cycloalkylamine or a derivative thereof, which is a cyclic compound, was added, the amount of acid produced was a very small amount of 3 to 5, and the acid was produced. It was confirmed that it was excellent in the suppression effect.

Claims (4)

A fuel cell coolant composition comprising a cycloalkylamine or a derivative thereof. Cycloalkylamine or a derivative thereof is any one or a mixture of two or more selected from cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, cyclooctylamine, and cyclododecylamine, or derivatives thereof. The fuel cell coolant composition according to claim 1, wherein the fuel cell coolant composition is provided. 3. The fuel cell coolant composition according to claim 1, wherein one or a mixture of two or more selected from water, glycols, alcohols, and glycol ethers is used as a base. The fuel cell coolant composition according to any one of claims 1 to 3, wherein the content of the cycloalkylamine or a derivative thereof is 0.001 to 20 parts by weight with respect to 100 parts by weight of the base. .