JPWO2006103757A1 - Coolant composition for fuel cell - Google Patents

Abstract

The present invention relates to a coolant composition for a fuel cell that maintains low conductivity over a long period of time and is excellent in antifreeze by suppressing generation of an ionic substance due to oxidation of a base. It is characterized by containing a compound having a cyclic atomic arrangement into which a carbonyl group is introduced and having an unsaturated bond in the cyclic atomic arrangement.

Description

  TECHNICAL FIELD The present invention relates to a coolant composition used for cooling a fuel cell, particularly an automotive fuel cell, and more specifically, cooling for a fuel cell excellent in maintaining a low conductivity over a long period of time. It relates to a liquid composition.

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

  A coolant passage is formed inside the cooling plate, and the stack is cooled by the flow of the coolant 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, low conductivity and antifreeze are required for the coolant of fuel cells, particularly automobile fuel cells.

Conventionally, as a fuel cell coolant composition that can meet the above requirements, a base composed of a mixed solution of water and glycols, and an amine-based alkaline addition that maintains the conductivity of the coolant at a low conductivity The thing containing an agent is proposed (refer patent document 1).
JP 2001-164244 A

  However, bases such as glycols in the composition are oxidized during fuel cell operation to produce ionic substances. For this reason, the amount of ionic substances in the cooling liquid increases with long-term use, and as a result, the low conductivity of the cooling liquid cannot be maintained.

  The present invention has been made in view of such circumstances, and by suppressing generation of an ionic substance due to oxidation of the base, a fuel cell that maintains low conductivity over a long period of time and is excellent in antifreeze An object of the present invention is to provide a cooling liquid composition.

  The fuel cell coolant composition of the present invention (hereinafter simply referred to as a composition) has a cyclic atomic arrangement in which a carbonyl group is introduced in the structural formula, and an unsaturated bond exists in the cyclic atomic arrangement. It is characterized by containing a compound.

  The base in this composition has low electrical conductivity and antifreeze, specifically, one or more selected from water, alcohols, glycols, and glycol ethers. Can be used.

  Examples of alcohols include one 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 can be mentioned.

  Glycol ethers include polyoxyalkylene glycol alkyl ethers such as 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. Mention may be made of one or more selected from monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether and tetraethylene glycol monobutyl ether. .

  The above base contains a compound having a cyclic atomic arrangement in which a carbonyl group is introduced in the structural formula and having an unsaturated bond in the cyclic atomic arrangement (hereinafter simply referred to as a compound). . Since this compound has a function of effectively suppressing the production of ionic substances due to the oxidation of the above-mentioned base, it is used as a cooling liquid for cooling the fuel cell by diluting the composition containing this compound. In such a case, the coolant has a low conductivity for a long time.

  The compound having such a function is not particularly limited as long as it has a cyclic atomic arrangement in which a carbonyl group is introduced in the structural formula and an unsaturated bond exists in the cyclic atomic arrangement. Are preferably those having 3 to 35 carbon atoms (especially those having 5 to 10 carbon atoms) in the cyclic atomic arrangement in that they are excellent in the effect of effectively suppressing the production of ionic substances due to oxidation of the base.

  Specific examples of this compound include oxazolone, pyrazolone, jasmon, benzoquinone, pyrone, γ-pyridone, uracil, tropone, tropolone, chromone, naphthoquinone, oxindole, phthalide, oxanthrone, anthrone, anthraquinone, alizarin, acridone, and their Derivatives can be mentioned.

  The compound is preferably contained in the range of 0.01 to 20 parts by weight with respect to 100 parts by weight of the base. When the content of the compound is less than 0.01 parts by weight, the effect of effectively suppressing the production of ionic substances due to oxidation of the base is not sufficient, and when the content of the compound exceeds 20 parts by weight, It is not possible to expect the effect of exceeding it, and it becomes uneconomical.

  In addition, the composition of the present invention may contain, for example, an antifoaming agent or a colorant in addition to the above-described components, as long as the low conductivity of the composition is not impaired. Additives such as molybdate, tungstate, sulfate, nitrate, benzoate, amine, triazole, and phosphate can be used in combination.

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

  Since the composition of the present invention contains a compound having a cyclic atomic arrangement in which a carbonyl group is introduced in the structural formula and an unsaturated bond is present in the cyclic atomic arrangement, ions generated by oxidation of the base It is possible to effectively suppress the generation of the active substance and maintain the low conductivity over a long period of time.

  Hereinafter, the composition of the present invention will be described in more detail with reference to Examples. In Table 1 below, 50% by weight of ethylene glycol and 50% by weight of ion-exchanged water are used as a base, and 0.1% by weight of α-pyrone is added as Example 1. Example 2 was prepared by adding 1.7% by weight of hinokitiol (tropolone).

  Moreover, what comprised only the said base was made into the comparative example 1, what added 1.0 weight% furfuryl alcohol to the said base was made into the comparative example 2, and 5.0 weight% cinnamon alcohol was added to the said base. Comparative Example 3 was obtained by adding

  About each composition of the said Examples 1 and 2, and Comparative Examples 1-3, the oxidation deterioration test was done and the electrical conductivity (microS / cm) after a test was measured. The results are shown in Table 2. In addition, the oxidation deterioration test of each composition was implemented on the conditions for 168 hours at 100 degreeC.

  From Table 2, when the electrical conductivity of each composition after oxidative degradation is seen, the composition of Comparative Example 1 consisting only of the base material has an initial electrical conductivity of 0.2, and the electrical conductivity after the oxidative degradation test is 43. The fluctuation was as large as 42.8, and it was confirmed that the conductivity was greatly increased due to oxidative degradation of the base.

  On the other hand, in the case of the composition of Comparative Example 2, the initial conductivity is 2.5, and the conductivity after the oxidative degradation test is 53. It was confirmed that the increase in conductivity due to oxidative deterioration of the base was not suppressed at all, but rather increased in conductivity.

  In the case of the composition of Comparative Example 3, the initial conductivity was 4.2 and the conductivity after the oxidative degradation test was 28, and the variation was 23.8, indicating that the base was oxidatively degraded. It was confirmed that the increase in conductivity due to was somewhat suppressed.

  On the other hand, in the composition of Example 1, the initial conductivity was 0.3 while the conductivity after the oxidative degradation test was 7.4, and the variation in the conductivity was 7 It was confirmed that the increase in conductivity due to oxidative deterioration of the base was effectively suppressed.

  Furthermore, the composition of Example 2 has an initial conductivity of 3.6, and the conductivity after the oxidative degradation test is 4.9, and its variation is as small as 1.3. It was confirmed that the increase in conductivity due to oxidative degradation was effectively suppressed, and the antioxidant effect of the base in the composition was much better than expected.

  From the above results, the compositions according to Examples 1 and 2 have an extremely small increase in conductivity despite being subjected to an oxidative deterioration test under severe conditions. Even when the product is diluted and applied as a coolant for a fuel cell, it is predicted that the production of ionic substances due to the oxidation of the base can be effectively suppressed, and the maintenance of low conductivity over a long period can be expected. .

Claims (5)

In the coolant composition for cooling the fuel cell,
A coolant composition for a fuel cell, comprising a compound having a cyclic atomic arrangement in which a carbonyl group is introduced in the structural formula and having an unsaturated bond in the cyclic atomic arrangement. 2. The coolant composition for a fuel cell according to claim 1, wherein the number of carbon atoms in the cyclic atomic arrangement of the compound is 3 to 35. The compound is oxazolone, pyrazolone, jasmon, benzoquinone, pyrone, γ-pyridone, uracil, tropone, tropolone, chromone, naphthoquinone, oxindole, phthalide, oxanthrone, anthrone, anthraquinone, alizarin, acridone, and derivatives thereof. The fuel cell coolant composition according to claim 2, wherein: 4. The compound according to claim 3, wherein the compound is contained in a base composed of one or a mixture of two or more selected from water, alcohols, glycols, and glycol ethers. A fuel cell coolant composition. 5. The fuel cell coolant composition according to claim 4, wherein the content of the compound is 0.01 to 20 parts by weight with respect to 100 parts by weight of the base.