A fuel cell coolant and a method of making the same

Abstract

The present application relates to the technical field of cooling liquid, and particularly relates to a fuel cell cooling liquid, which comprises the following components measured by weight parts: 480-510 parts of ultrapure water, 350-450 parts of ethylene glycol, 60-180 parts of glycerol, 4.3-5.1 parts of a sugar alcohol mixture, and 6-7 parts of an inhibitor; the preparation method of the sugar alcohol mixture comprises the following steps: mixing 150-250 parts of lactitol, 100-175 parts of mannitol and 3-8 parts of pyridine by weight, stirring at a temperature of 0-5 DEG C until completely dissolved to obtain a mixed standby solution; slowly adding 95-110 parts of acetic anhydride to the mixed standby solution at a temperature of 0-5 DEG C, and then standing at a temperature of 25-30 DEG C for 12-14 hours after the addition is completed to obtain a to-be-purified solution; pouring the to-be-purified solution into an ice water mixture prepared from ultrapure water, standing for 30-60 minutes, filtering the precipitated sediment, washing with 0-10 DEG C ethanol, and vacuum drying to obtain the sugar alcohol mixture. The present application has good antifreezing performance and good flow performance in a low-temperature environment.

Description

Technical Field

[0001] This invention relates to the field of coolant technology, and more particularly to a fuel cell coolant and its preparation method. Background Technology

[0002] Fuel cells are typically stacked together to form a battery pack. To cool the fuel cells, a cooling plate is installed in each of the multi-layered battery packs. Coolant flow paths are designed inside the cooling plate, through which the coolant flows to cool the fuel cell stack.

[0003] Coolants used in fuel cells typically use ultrapure water as a refrigerant and ethylene glycol as an antifreeze to lower the freezing point. Auxiliary agents generally include corrosion inhibitors, defoamers, and pH adjusters. However, under prolonged high-temperature conditions, ethylene glycol oxidizes and decomposes to produce organic acids, aldehydes, and other substances, leading to reduced thermal conductivity of the coolant and contamination of the proton exchange membrane, causing performance degradation of the membrane electrode assembly. To address the issue of ethylene glycol's easy high-temperature oxidation and decomposition, glycerol can be added, utilizing its antioxidant properties to potentially inhibit ethylene glycol oxidation and decomposition. However, the addition of glycerol raises the freezing point of the coolant. To further lower the freezing point, the concentration of glycerol needs to be increased, which in turn leads to a significant increase in the coolant's viscosity. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides a fuel cell coolant that has good antifreeze properties and good flow properties in low-temperature environments.

[0005] To address the aforementioned problems, this invention proposes a fuel cell coolant comprising the following components in parts by weight: 480-510 parts ultrapure water, 350-450 parts ethylene glycol, 60-180 parts glycerol, 4.3-5.1 parts sugar alcohol mixture, and 6-7 parts corrosion inhibitor. The method for preparing the sugar alcohol mixture includes the following steps: Mix 150-250 parts by weight of lactitol, 100-175 parts by weight of mannitol, and 3-8 parts by volume of pyridine, and stir at 0-5°C until completely dissolved to obtain a mixed solution for later use. At a temperature of 0~5℃, slowly add 95~110 volume parts of acetic anhydride to the mixed standby solution. After the addition is complete, let it stand at a temperature of 25~30℃ for 12~14 hours to obtain the solution to be purified. Pour the solution to be purified into an ice-water mixture made of ultrapure water, let it stand for 30-60 minutes, filter the precipitate, wash it with ethanol at 0-10℃, and dry it under vacuum to obtain a sugar alcohol mixture.

[0006] As an improvement to the above technical solution, the weight ratio of lactitol to mannitol is 1:(0.67~0.85).

[0007] As an improvement to the above technical solution, in the preparation method of the sugar alcohol mixture, the mixing and stirring time of lactitol, mannitol and pyridine is 45~70 min.

[0008] As an improvement to the above technical solution, the acetic anhydride is added over a period of 15-20 minutes.

[0009] As an improvement to the above technical solution, the preparation method of the sustained-release agent includes the following steps: Benzotriazole and 2-isopropylimidazoline were mixed at a weight ratio of 1:(0.5~0.8) and stirred until homogeneous to obtain a sustained-release agent.

[0010] As an improvement to the above technical solution, the weight ratio of the mixture of ethylene glycol, glycerol, and sugar alcohol is 94:31:1.

[0011] Accordingly, the present invention also provides a method for preparing fuel cell coolant, comprising the following steps: Weigh the corrosion inhibitor according to the ratio, and weigh the first predetermined part by weight of ultrapure water. Mix the corrosion inhibitor and ultrapure water and stir for the first time to obtain the first mixture. Weigh out the mixture of glycerol and sugar alcohol according to the formula, and weigh out the first predetermined part by weight of ethylene glycol, and add it to the first mixture. Stir for the second time at a temperature of 150~160°C to obtain the second mixture. After the second mixture has cooled to 25-30°C, add a second predetermined weight of ultrapure water and a second predetermined weight of ethylene glycol, stir until homogeneous, and then cool.

[0012] As an improvement to the above technical solution, the weight ratio of the first predetermined weight part of ultrapure water to the second predetermined weight part of ultrapure water is 1:(3.3~3.8). The weight ratio of the first predetermined part by weight of ethylene glycol to the second predetermined part by weight of ethylene glycol is 1:(4.3~4.7).

[0013] As an improvement to the above technical solution, the stirring time for the first stirring is 30-45 minutes, and the stirring time for the second stirring is 2-3 hours.

[0014] The implementation of this invention has the following beneficial effects: (1) The fuel cell coolant of the present invention comprises the following components by weight: 480-510 parts ultrapure water, 350-450 parts ethylene glycol, 60-180 parts glycerol, 4.3-5.1 parts sugar alcohol mixture, and 6-7 parts corrosion inhibitor. This coolant uses a mixture of glycerol and ethylene glycol as an antifreeze agent. Glycerol has the ability to inhibit the easy oxidation and decomposition of ethylene glycol under high temperature conditions, thus solving the problem that long-term use of ethylene glycol easily affects battery performance.

[0015] (2) The sugar alcohol mixture is made by mixing lactitol, mannitol, pyridine and acetic anhydride. This mixture can solve the problem of increased freezing point after the introduction of glycerol into the refrigerant, as well as the problem of poor fluidity of the refrigerant under low temperature conditions. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0017] This invention provides a fuel cell coolant comprising the following components by weight: 480-510 parts ultrapure water, 350-450 parts ethylene glycol, 60-180 parts glycerol, 4.3-5.1 parts sugar alcohol mixture, and 6-7 parts corrosion inhibitor.

[0018] To address the issue of increased cooling point after the addition of glycerol, this embodiment incorporates 4.3 to 5.1 parts of a sugar alcohol mixture.

[0019] Specifically, the preparation method of the sugar alcohol mixture includes the following steps: Mix 150-250 parts by weight of lactitol, 100-175 parts by weight of mannitol, and 3-8 parts by volume of pyridine, and stir at 0-5°C until completely dissolved to obtain a mixed solution for later use. At a temperature of 0~5℃, slowly add 95~110 volume parts of acetic anhydride to the mixed standby solution. After the addition is complete, let it stand at a temperature of 25~30℃ for 12~14 hours to obtain the solution to be purified. Pour the solution to be purified into an ice-water mixture made of ultrapure water, let it stand for 30-60 minutes, filter the precipitate, wash it with ethanol at 0-10℃, and dry it under vacuum to obtain a sugar alcohol mixture.

[0020] It should be noted that the above correspondence between parts by weight and parts by volume is in g / ml.

[0021] It should be noted that the ethanol mentioned above is analytical grade ethanol.

[0022] The sugar alcohol mixture obtained by the above preparation method can significantly reduce the ion concentration of the coolant, thus decreasing its conductivity. When combined with glycerol, the sugar alcohol mixture can capture free radicals in the coolant, blocking the ethylene glycol oxidation chain reaction and solving the problem of ethylene glycol easily oxidizing and decomposing into organic acids at high temperatures during long-term use. The pH value is stabilized at 6.0-7.5, reducing corrosion of metal pipelines. Furthermore, the addition of this mixture can lower the freezing point of the coolant containing glycerol and solve the problem of increased coolant viscosity after the addition of glycerol.

[0023] Preferably, the weight ratio of lactitol to mannitol is 1:(0.67~0.85). Examples include 1:0.67, 1:0.68, 1:0.73, 1:0.77, 1:0.81, and 1:0.85, but these are not limited to these. The long-chain structure of lactitol synergizes with the small molecule of mannitol, allowing the sugar alcohol mixture to be uniformly dispersed in the coolant without crystallization at low temperatures. When the above weight ratio is less than 0.85, the amount of mannitol added is excessive, leading to enhanced intermolecular hydrogen bonding, resulting in deteriorated low-temperature fluidity and increased corrosion. When the above weight ratio is greater than 1:0.67, the amount of mannitol added is too small, which will increase the conductivity of the coolant, posing a risk of short circuit in the fuel cell.

[0024] Preferably, in the method for preparing the sugar alcohol mixture, the mixing and stirring time of lactitol, mannitol, and pyridine is 45-70 min. Examples of such stirring times are 45 min, 55 min, 63 min, 67 min, 69 min, and 70 min, but are not limited to these. Controlling the stirring time is to ensure that the above substances do not agglomerate at low temperatures. When the stirring time is less than 45 min, residual lactitol microcrystals will increase the conductivity of the coolant, posing a risk of short circuit in the fuel cell. When the stirring time is greater than 70 min, it is easy to cause pyridine decomposition or partial oxidation of the sugar alcohol.

[0025] Preferably, the acetic anhydride is added dropwise over a period of 15-20 minutes. When acetic anhydride is added dropwise to the mixture of lactitol, mannitol, and pyridine, a significant amount of heat is generated. Slow addition allows the heat of reaction to be released gradually, preventing a temperature rise exceeding 5°C / min and avoiding localized overheating. If the addition time is less than 15 minutes, the rapid drop rate generates excessive heat, which can lead to carbonization and coking of lactitol and mannitol. If the addition time is greater than 20 minutes, prolonged exposure of acetic anhydride increases hydrolysis, causing the pH of the coolant system to drop below 5.0, corroding metal pipes.

[0026] The corrosion inhibitor used in this embodiment can be any commercially available product. Specifically, it can be an oxide film type corrosion inhibitor (molybdate, tungstate, borate, etc.), a precipitation film type corrosion inhibitor (phosphate, silicate, zinc salt), or an adsorption film type corrosion inhibitor (benzotriazole, toluenetriazole, mercaptobenzothiazole, hexadecaneamine).

[0027] Preferably, the corrosion inhibitor in this embodiment includes benzotriazole and 2-isopropylimidazoline. Specifically, the preparation method of the slow-release agent includes the following steps: Benzotriazole and 2-isopropylimidazoline were mixed at a weight ratio of 1:(0.5~0.8) and stirred until homogeneous to obtain a sustained-release agent.

[0028] Examples of the above-mentioned corrosion inhibitor dosage weight ratios are 1:0.5, 1:0.6, and 1:0.8, but are not limited to these. Controlling the weight mixing ratio of benzotriazole and 2-isopropylimidazoline can balance pH buffering and conductivity. The tertiary amine group of imidazoline can neutralize acidic byproducts, and both can improve high-temperature stability within the above mixing ratios. If the above mixing weight ratio is less than 1:0.8, excessive 2-isopropylimidazoline is added, hindering BTA film formation, causing copper ions to dissolve, and the ionization of excess tertiary amine results in conductivity >5 μS / cm. If the above mixing ratio is greater than 1:0.5, excessive benzotriazole is added, resulting in insufficient alkyl chain coverage and an increased oxygen diffusion corrosion rate.

[0029] Benzotriazole can form a dense polymer film (≤10nm thick) with copper ions, blocking electrochemical corrosion channels and exhibiting high corrosion inhibition rate at pH 6-10. The hydrophobic long-chain alkyl group of 2-isopropylimidazoline adsorbs onto the steel surface, forming an oriented molecular film that inhibits oxygen diffusion corrosion. The corrosion inhibitor formulated from these two substances has a wide range of applications, is less expensive than other common types of corrosion inhibitors, and is less prone to scaling.

[0030] Preferably, the weight ratio of the ethylene glycol, glycerol, and sugar alcohol mixture is 94:31:1. This ratio offers advantages such as optimized low-temperature fluidity, maintenance of ultra-low conductivity, high-temperature stability, and corrosion inhibition. The sugar alcohol mixture disrupts the ordered arrangement of water molecules, preventing localized crystallization at low temperatures that could clog the pipeline. The sugar alcohol mixture keeps the conductivity ≤2 μS / cm, avoiding short circuits in the fuel cell. Glycerol compensates for the low-boiling-point defect of ethylene glycol, increasing the boiling point of the mixture and reducing the risk of cavitation.

[0031] Accordingly, this invention also provides a method for preparing fuel cell coolant, comprising the following steps: Weigh the corrosion inhibitor according to the ratio, and weigh the first predetermined weight of ultrapure water. Mix the corrosion inhibitor and ultrapure water and stir for the first time to obtain the first mixture; specifically, the stirring time for the first stirring is 30~45min. Weigh out the mixture of glycerol and sugar alcohol according to the formula, and weigh out the first predetermined weight of ethylene glycol, and add it to the first mixture. Stir for a second time at a temperature of 150~160℃ to obtain the second mixture; specifically, the second stirring time is 2~3 hours.

[0032] After the second mixture has cooled to 25-30°C, add a second predetermined weight of ultrapure water and a second predetermined weight of ethylene glycol, stir until homogeneous, and then cool.

[0033] The weight ratio of the first predetermined part by weight of ultrapure water to the second predetermined part by weight of ultrapure water is 1:(3.3~3.8). The weight ratio of the first predetermined part by weight of ethylene glycol to the second predetermined part by weight of ethylene glycol is 1:(4.3~4.7).

[0034] The first stirring is to ensure complete dissolution and activation of the corrosion inhibitor. Benzotriazole and imidazoline corrosion inhibitors require sufficient hydration and dissociation; 30 minutes is the minimum dissolution and activation threshold. Stirring for less than this time results in particle residue and localized corrosion. Stirring for more than 45 minutes introduces dissolved oxygen, accelerating the oxidation and decomposition of the corrosion inhibitor. The second stirring involves uniformly mixing ethylene glycol, glycerol, and sugar alcohol. The controlled stirring times ensure that the coolant conductivity remains stable at ≤2 μS / cm, meeting the insulation requirements of the fuel cell.

[0035] Ultrapure water and ethylene glycol are added in steps. This ensures efficient activation and dispersion of the corrosion inhibitor. The initial addition of a small amount of ultrapure water mixes with the inhibitor, and stirring for 30-45 minutes allows for complete hydration and dissociation of the inhibitor molecules, forming nanoscale pre-film micelles. This prevents subsequent high-concentration alcohols from interfering with its dispersion. The initial addition of a small amount of ethylene glycol serves as a co-solvent, improving the corrosion inhibitor's solubility and stability at high temperatures.

[0036] Step-by-step quantity control avoids high-temperature hydrolysis side reactions, maintaining conductivity ≤2μS / cm. Pre-activation ensures uniform film formation of the corrosion inhibitor on the metal surface. It avoids high-temperature decomposition of sugar alcohols and oxidation of ethylene glycol, extending coolant life.

[0037] The present invention will now be described with reference to specific embodiments: Example 1 This embodiment provides a fuel cell coolant, comprising the following components measured in parts by weight: 500 parts ultrapure water, 423 parts ethylene glycol, 139.5 parts glycerol, 4.5 parts sugar alcohol mixture, and 6.5 parts corrosion inhibitor; The method for preparing the sugar alcohol mixture includes the following steps: 200 parts by weight of lactitol, 150 parts by weight of mannitol and 5.5 parts by volume of pyridine were mixed and stirred at 0°C for 58 minutes until completely dissolved to obtain a mixed solution for later use. At 0°C, 100 volumes of acetic anhydride were slowly added dropwise (total adding time 18 min) to the mixed stand solution. After the addition was complete, the solution was allowed to stand at 25°C for 13 h to obtain the solution to be purified. The solution to be purified was poured into an ice-water mixture made of ultrapure water and allowed to stand for 45 minutes. The precipitate was filtered, washed with analytical grade ethanol at 0 to -10 °C, and dried under vacuum to obtain a sugar alcohol mixture.

[0038] The preparation method of the sustained-release agent includes the following steps: Benzotriazole and 2-isopropylimidazoline were mixed at a weight ratio of 1:0.7 and stirred until homogeneous to obtain a sustained-release agent.

[0039] The above-mentioned method for preparing fuel cell coolant includes the following steps: Weigh the corrosion inhibitor according to the ratio, and weigh the first predetermined part by weight of ultrapure water. Mix the corrosion inhibitor and ultrapure water and stir for the first time to obtain the first mixture. Weigh out the mixture of glycerol and sugar alcohol according to the formula, and weigh out the first predetermined part by weight of ethylene glycol, and add it to the first mixture. Stir for the second time at a temperature of 155°C to obtain the second mixture. After the second mixture has cooled to 25°C, add a second predetermined weight of ultrapure water and a second predetermined weight of ethylene glycol, stir until homogeneous, and then cool.

[0040] The weight ratio of the first predetermined part by weight of ultrapure water to the second predetermined part by weight of ultrapure water is 1:3.5; The weight ratio of the first predetermined part by weight of ethylene glycol to the second predetermined part by weight of ethylene glycol is 1:4.5.

[0041] The first stirring time is 38 minutes, and the second stirring time is 2.5 hours.

[0042] Example 2 The difference between this embodiment and Embodiment 1 is that: The amount of lactitol added is 250 parts by weight, and the amount of mannitol added is 100 parts by weight.

[0043] Example 3 The difference between this embodiment and Embodiment 1 is that: The amount of lactitol added was 150 parts by weight, and the amount of mannitol added was 147 parts by weight.

[0044] Example 4 The difference between this embodiment and Embodiment 1 is that: In the preparation method of the sugar alcohol mixture, the mixing and stirring time of lactitol, mannitol and pyridine is 30 min.

[0045] Example 5 The difference between this embodiment and Embodiment 1 is that: In the preparation method of the sugar alcohol mixture, the mixing and stirring time of lactitol, mannitol and pyridine is 90 min.

[0046] Example 6 The difference between this embodiment and Embodiment 1 is that: The acetic anhydride was added over a period of 10 minutes.

[0047] Example 7 The difference between this embodiment and Embodiment 1 is that: The acetic anhydride was added over a period of 30 minutes.

[0048] Example 8 The difference between this embodiment and Embodiment 1 is that: The fuel cell coolant comprises the following components in parts by weight: 500 parts ultrapure water, 423 parts ethylene glycol, 60 parts glycerol, 5.1 parts sugar alcohol mixture, and 6.5 parts corrosion inhibitor.

[0049] Example 9 The difference between this embodiment and Embodiment 1 is that: The fuel cell coolant comprises the following components in parts by weight: 500 parts ultrapure water, 350 parts ethylene glycol, 180 parts glycerol, 4.3 parts sugar alcohol mixture, and 6.5 parts corrosion inhibitor.

[0050] Comparative Example 1 This comparative example provides a fuel cell coolant comprising the following components measured in parts by weight: 500 parts ultrapure water, 423 parts ethylene glycol, 139.5 parts glycerol, and 6.5 parts corrosion inhibitor.

[0051] Comparative Example 2 This comparative example provides a fuel cell coolant comprising the following components measured in parts by weight: 500 parts ultrapure water, 423 parts ethylene glycol, 139.5 parts glycerol, 4.5 parts sugar alcohol mixture, and 6.5 parts corrosion inhibitor; The sugar alcohol mixture is made by mixing lactitol and mannitol, and the weight ratio of lactitol to mannitol is 1:0.75.

[0052] The fuel cell coolants prepared in Examples 1-9 and Comparative Examples 1-2 were subjected to performance tests. Freezing point testing was conducted according to SH / T 0090 "Determination of Freezing Point of Engine Coolant" to demonstrate antifreeze performance; electrical conductivity testing was conducted according to GB / T 6682 "Specifications and Test Methods for Water Used in Analytical Laboratories" to demonstrate insulation performance; and dynamic viscosity (0℃) testing was conducted according to GB / T 265 "Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity of Petroleum Products" to demonstrate low-temperature fluidity.

[0053] The test results are shown in the table below.

[0054] In summary, the present invention, by adding glycerol, effectively inhibits the easy oxidation and decomposition of ethylene glycol at high temperatures, thus solving the problem that long-term use of ethylene glycol can negatively impact battery performance. Furthermore, the addition of a modified sugar alcohol mixture effectively lowers the freezing point and conductivity of the coolant. Simultaneously, it addresses the issue of increased viscosity of the coolant at low temperatures after the addition of glycerol. Through these technical means, the coolant possesses excellent high-temperature oxidation resistance, good antifreeze properties, and good flow properties at low temperatures.

[0055] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A fuel cell coolant, characterized in that, It includes the following components by weight: 480-510 parts ultrapure water, 350-450 parts ethylene glycol, 60-180 parts glycerol, 4.3-5.1 parts sugar alcohol mixture, and 6-7 parts corrosion inhibitor; The method for preparing the sugar alcohol mixture includes the following steps: Mix 150-250 parts by weight of lactitol, 100-175 parts by weight of mannitol, and 3-8 parts by volume of pyridine, and stir at 0-5°C until completely dissolved to obtain a mixed solution for later use. At a temperature of 0~5℃, slowly add 95~110 volume parts of acetic anhydride to the mixed standby solution. After the addition is complete, let it stand at a temperature of 25~30℃ for 12~14 hours to obtain the solution to be purified. Pour the solution to be purified into an ice-water mixture made of ultrapure water, let it stand for 30 to 60 minutes, filter the precipitate, wash it with ethanol at 0 to -10°C, and dry it under vacuum to obtain a sugar alcohol mixture. In the method for preparing the sugar alcohol mixture, the mixing and stirring time of lactitol, mannitol and pyridine is 45-70 min; The acetic anhydride is added over a period of 15 to 20 minutes.

2. The fuel cell coolant as described in claim 1, characterized in that, The weight ratio of lactitol to mannitol is 1:(0.67~0.85).

3. The fuel cell coolant as described in claim 1, characterized in that, The method for preparing the corrosion inhibitor includes the following steps: Benzotriazole and 2-isopropylimidazoline were mixed at a weight ratio of 1:(0.5~0.8) and stirred until homogeneous to obtain a corrosion inhibitor.

4. The fuel cell coolant as described in claim 1, characterized in that, The weight ratio of the mixture of ethylene glycol, glycerol, and sugar alcohol is 94:31:

1.

5. A method for preparing a fuel cell coolant as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Weigh the corrosion inhibitor according to the ratio, and weigh the first predetermined part by weight of ultrapure water. Mix the corrosion inhibitor and ultrapure water and stir for the first time to obtain the first mixture. Weigh out the mixture of glycerol and sugar alcohol according to the formula, and weigh out the first predetermined part by weight of ethylene glycol, and add it to the first mixture. Stir for the second time at a temperature of 150~160°C to obtain the second mixture. After the second mixture cools to 25~30℃, add a second predetermined weight of ultrapure water and a second predetermined weight of ethylene glycol, stir evenly and cool.

6. The method for preparing fuel cell coolant as described in claim 5, characterized in that, The weight ratio of the first predetermined part by weight of ultrapure water to the second predetermined part by weight of ultrapure water is 1:(3.3~3.8); The weight ratio of the first predetermined part by weight of ethylene glycol to the second predetermined part by weight of ethylene glycol is 1:(4.3~4.7).

7. The method for preparing fuel cell coolant as described in claim 5, characterized in that, The first stirring time is 30-45 minutes, and the second stirring time is 2-3 hours.

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