Preparation method and application of tetravalent vanadium electrolyte capable of reducing residues of reducing agent

Abstract

The invention relates to a preparation method and application of a tetravalent vanadium electrolyte capable of reducing residues of a reducing agent, and belongs to the technical field of chemical engineering. The method comprises the following steps: mixing concentrated sulfuric acid with water; oxalic acid is added into the sulfuric acid aqueous solution, the mass ratio of sulfuric acid to oxalic acid is 1: 3.5-4.5, vanadium pentoxide powder is added, heat released by mixing of oxalic acid and vanadium pentoxide continues to be utilized, the reaction rate is increased, and then heating is conducted to 95-100 DEG C; adding concentrated sulfuric acid into the solution so as to continuously utilize heat released by mixing the concentrated sulfuric acid and water, and further heating to 95-100 DEG C; and naturally cooling the obtained solution, and filtering to obtain the reduced tetravalent vanadium electrolyte, namely the vanadyl sulfate solution. The method is short in technological process, high in reaction speed, high in product yield and suitable for industrial scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical industry, and particularly relates to a preparation method and application of a 4-valence vanadium electrolyte with reduced residual reducing agent. BACKGROUND

[0002] As a new type of energy storage technology, all-vanadium redox flow batteries have broad application prospects in large-scale energy storage due to their intrinsic safety, long service life, and flexible energy storage capacity. Electrolyte, as a core component of all-vanadium redox flow batteries, directly affects the overall performance and service life of the battery. Therefore, the preparation of high-stability, high-concentration, and high-purity electrolyte is the key to the commercial application of all-vanadium redox flow batteries.

[0003] In the preparation process of electrolyte, the use of reducing agent is essential, which is used to reduce high-valence vanadium ions to the required low-valence ions. However, the reducing agent is often difficult to completely consume during the reaction, resulting in a certain amount of residual reducing agent in the electrolyte. These residual reducing agents not only reduce the purity of the electrolyte, but also may have a negative impact on the battery performance, such as increasing the self-discharge rate and shortening the battery life.

[0004] In order to reduce the impact of reducing agents on energy storage equipment, researchers have been working to develop new preparation methods and technologies. These technologies aim to minimize the residual amount of reducing agent in the electrolyte by optimizing the preparation process, selecting the appropriate type and amount of reducing agent, and introducing effective removal mechanisms. This is of great significance to improving the quality of electrolyte, enhancing the overall performance of the battery, and prolonging the service life of the battery.

[0005] Although reducing the residual reducing agent is an important issue in the preparation of electrolyte, there are still many challenges in achieving this goal. For example, how to ensure that the reducing agent is fully consumed during the reaction, how to effectively remove the residual reducing agent in the electrolyte, and how to improve the purity of the electrolyte without introducing new impurities. Therefore, future research directions can include the following aspects: Optimize the preparation process: improve the reaction efficiency and utilization of reducing agents by improving the preparation process and conditions.

[0006] Select the appropriate reducing agent: find the type and amount of reducing agent with high reaction activity and low residual amount.

[0007] Introduce removal mechanism: use physical, chemical, or electrochemical methods to remove residual reducing agents in the electrolyte.

[0008] Improve the purity of the electrolyte: further improve the purity of the electrolyte through fine filtration, ion exchange, distillation, etc.

[0009] In summary, the technical background of the preparation method of the reducing agent residual 4-valence electrolyte is an important link in the commercial application of the all-vanadium redox flow battery. By continuously optimizing the preparation technology, the performance and stability of the electrolyte can be improved, which will help to promote the wide application of the all-vanadium redox flow battery in the energy storage field. SUMMARY

[0010] The technical problem to be solved by the present application is to provide a preparation method and application of a reducing agent residual 4-valence vanadium electrolyte. The present application utilizes the heat released by mixing concentrated sulfuric acid and water to accelerate the reaction, utilizes the heat released by the reaction to accelerate the dissolution of oxalic acid, and again utilizes the heat released by mixing concentrated sulfuric acid and water to increase the temperature to the purpose of emptying the oxalic acid residue; the waste residue and waste liquid are discharged during the reaction process, which meets the requirements of green environmental protection and clean production; the process flow is short, the reaction speed is fast, the product yield is high, the equipment investment is small, and it is suitable for industrial scale production.

[0011] To solve the above technical problems, the technical scheme adopted by the present application is: a preparation method of a reducing agent residual 4-valence vanadium electrolyte, characterized in that the preparation method comprises the following steps: (1) mixing concentrated sulfuric acid and water; the mass ratio of concentrated sulfuric acid to water is 1:3.8-4.1; (2) immediately adding oxalic acid to the sulfuric acid aqueous solution obtained in step (1), the mass ratio of sulfuric acid to oxalic acid is 1:3.5-4.5, so as to utilize the heat released by mixing concentrated sulfuric acid and water to improve the dissolution efficiency of oxalic acid; (3) adding vanadium pentoxide powder to the solution obtained in step (2), so as to continue utilizing the heat released by mixing oxalic acid and vanadium pentoxide to improve the reaction rate, and then heating to 95-100℃; (4) adding concentrated sulfuric acid to the solution obtained in step (3), so as to continue utilizing the heat released by mixing concentrated sulfuric acid and water, and then heating to 95-100℃; (5) naturally cooling the solution obtained in step (4) and filtering to obtain the reduced 4-valence vanadium electrolyte, i.e. vanadyl sulfate solution.

[0012] The method of the present application further comprises solid-liquid separation after the reaction is completed to remove solid impurities and obtain a 4-valence vanadium electrolyte solution.

[0013] The separation of the present application is filtration separation or centrifugal separation.

[0014] The steps (3) and (4) of the present application both need to be heated, the temperature is 95-100℃, and the holding time is 0.5-1h.

[0015] The mass fraction of the concentrated sulfuric acid added in step (4) of the present application is 96-98%, and the density is 1.82-1.85g / L.

[0016] The mass ratio of the vanadium pentoxide powder, the concentrated sulfuric acid and the oxalic acid in the method is 1:2.88:0.7-0.9, and the concentrated sulfuric acid is the total amount of the concentrated sulfuric acid.

[0017] The oxalic acid is dihydrate oxalic acid with a mass fraction of ≥99.6%.

[0018] The molar ratio of vanadium to sulfur in the vanadyl sulfate solution prepared by the method is 1.7±0.05:4.3±0.05.

[0019] The vanadium electrolyte prepared by the method is detected by the oxidation-reduction titration method, and the residual amount of the reducing agent oxalic acid in the obtained tetravalent vanadium electrolyte is as low as 0.

[0020] Another object of the application is to provide a tetravalent vanadium electrolyte prepared by the method for reducing the residual reducing agent, and the tetravalent vanadium electrolyte is used as a vanadium battery electrolyte.

[0021] The design idea of the application is that, compared with the traditional process (which requires an external heat source for step-by-step temperature control), the application realizes the key temperature of 100 DEG C by self-sufficient energy in the reaction system, which is the first time to realize the "zero external heat input" design in the preparation of vanadium electrolyte. The present application finds that the three-stage exothermic process can be synergistically amplified and accurately matched with the reaction energy barrier, which breaks through the thinking stereotype that "dilution heat is only used for preheating".

[0022] The beneficial effects of the above technical solution are as follows: 1. The application creatively connects the three-stage exothermic process of concentrated sulfuric acid dilution heat, oxalic acid dissolution heat and V2O5 reduction reaction heat in series to form a self-sustaining heat circulation system. The heat released by the mixing of concentrated sulfuric acid and water is used to accelerate the reaction, the heat released by the reaction is used to accelerate the dissolution of oxalic acid, and the heat released by the mixing of concentrated sulfuric acid and water is used again to increase the temperature to the purpose of clearing the residual oxalic acid. The waste residue and waste liquid are discharged during the reaction process, which meets the requirements of green environmental protection and clean production. The process flow is short, the reaction speed is fast, the product yield is high, the equipment investment is small, and it is suitable for industrial scale production. 2. The raw materials selected by the method are few in type and high in purity, and no other organic substances are involved except oxalic acid, which reduces the introduction of foreign impurities. The obtained vanadyl sulfate solution has no impurity residues, and it is a new type of fast and clean method for preparing vanadyl sulfate electrolyte. 3. The molar ratio of vanadium to sulfur in the vanadyl sulfate solution prepared by the application is 1.7±0.05:4.3±0.05. When the vanadyl sulfate solution is used as an electrolyte, the excess oxalic acid in the vanadyl sulfate electrolyte can be avoided, and the phenomenon of precipitation blocking the vanadium battery can be avoided. DETAILED DESCRIPTION

[0023] The application will be further described in detail below in combination with specific embodiments. Embodiment 1

[0024] A method for preparing a tetravalent vanadium electrolyte with reduced reducing agent residue, comprising the following steps: (1) mixing concentrated sulfuric acid and water; the mass ratio of concentrated sulfuric acid (mass fraction 98%, density 1.84 g / L) to water is 1:3.8; (2) immediately adding oxalic acid to the sulfuric acid aqueous solution obtained in step (1), the mass ratio of sulfuric acid to oxalic acid (oxalic acid is oxalic acid dihydrate, mass fraction 99.6%) is 1:3.5; (3) adding vanadium pentoxide powder to the solution obtained in step (2) to continue utilizing the heat released by the mixture of oxalic acid and vanadium pentoxide to improve the reaction rate, and then heating to 100℃, the holding time is 0.5h; (4) adding concentrated sulfuric acid to the solution obtained in step (3) to continue utilizing the heat released by the mixture of concentrated sulfuric acid and water, and then heating to 95℃, the holding time is 1h; the mass ratio of vanadium pentoxide powder:concentrated sulfuric acid (total amount):oxalic acid is 1:2.88:0.7; (5) naturally cooling the solution obtained in step (4) and filtering to perform solid-liquid separation (filtration separation or centrifugal separation) to remove solid impurities, and to obtain the reduced 4-valence vanadium electrolyte, i.e. vanadyl sulfate solution; the molar ratio of vanadium to sulfur in the vanadyl sulfate solution is 1.7:4.3.

[0025] The 4-valence vanadium electrolyte of this example is detected by oxidation-reduction titration method, and the residual oxalic acid in the reduced 4-valence vanadium electrolyte is as low as 0. Example 2

[0026] A method for preparing a 4-valence vanadium electrolyte with reduced residual reducing agent, comprising the following steps: (1) mixing concentrated sulfuric acid and water; the mass ratio of concentrated sulfuric acid (mass fraction 98%, density 1.84 g / L) to water is 1:4.1; (2) immediately adding oxalic acid to the sulfuric acid aqueous solution obtained in step (1), the mass ratio of sulfuric acid to oxalic acid (oxalic acid is oxalic acid dihydrate, mass fraction 99.8%) is 1:4.5; (3) adding vanadium pentoxide powder to the solution obtained in step (2) to continue utilizing the heat released by the mixture of oxalic acid and vanadium pentoxide to improve the reaction rate, and then heating to 95℃, the holding time is 1h; (4) adding concentrated sulfuric acid to the solution obtained in step (3) to continue utilizing the heat released by the mixture of concentrated sulfuric acid and water, and then heating to 98℃, the holding time is 0.8h; the mass ratio of vanadium pentoxide powder:concentrated sulfuric acid (total amount):oxalic acid is 1:2.88:0.9; (5) naturally cooling the solution obtained in step (4) and filtering to perform solid-liquid separation (filtration separation or centrifugal separation) to remove solid impurities, and to obtain the reduced 4-valence vanadium electrolyte, i.e. vanadyl sulfate solution; the molar ratio of vanadium to sulfur in the vanadyl sulfate solution is 1.75:4.25.

[0027] The 4-valence vanadium electrolyte of the present example is detected by redox titration method, and the residual reducing agent oxalic acid in the obtained 4-valence vanadium electrolyte is as low as 0. Example 3

[0028] A method for preparing a 4-valence vanadium electrolyte with reduced residual reducing agent, comprising the following steps: (1) mixing concentrated sulfuric acid and water; the mass ratio of concentrated sulfuric acid (mass fraction 98%, density 1.84 g / L) to water is 1:3.9; (2) immediately adding oxalic acid to the sulfuric acid aqueous solution obtained in step (1), the mass ratio of sulfuric acid to oxalic acid (oxalic acid is oxalic acid dihydrate, mass fraction 99.7%) is 1:3.8; (3) adding vanadium pentoxide powder to the solution obtained in step (2) to continue utilizing the heat released by the mixture of oxalic acid and vanadium pentoxide to increase the reaction rate, and then heating to 96℃, and keeping the temperature for 1h; (4) adding concentrated sulfuric acid to the solution obtained in step (3) to continue utilizing the heat released by the mixture of concentrated sulfuric acid and water, and then heating to 100℃, and keeping the temperature for 0.5h; the mass ratio of vanadium pentoxide powder to concentrated sulfuric acid (total amount) to oxalic acid is 1:2.88:0.9; (5) naturally cooling the solution obtained in step (4) and filtering to separate the solid and liquid (filtering separation or centrifugal separation) to remove solid impurities, and obtaining the reduced 4-valence vanadium electrolyte, i.e. vanadyl sulfate solution; the molar ratio of vanadium to sulfur in the vanadyl sulfate solution is 1.7:4.25.

[0029] The 4-valence vanadium electrolyte of the present example is detected by redox titration method, and the residual reducing agent oxalic acid in the obtained 4-valence vanadium electrolyte is as low as 0. Example 4

[0030] A method for preparing a 4-valence vanadium electrolyte with reduced residual reducing agent, comprising the following steps: (1) mixing concentrated sulfuric acid and water; the mass ratio of concentrated sulfuric acid (mass fraction 98%, density 1.84 g / L) to water is 1:4.0; (2) immediately adding oxalic acid to the sulfuric acid aqueous solution obtained in step (1), the mass ratio of sulfuric acid to oxalic acid (oxalic acid is oxalic acid dihydrate, mass fraction 99.6%) is 1:4.0; (3) adding vanadium pentoxide powder to the solution obtained in step (2) to continue utilizing the heat released by the mixture of oxalic acid and vanadium pentoxide to increase the reaction rate, and then heating to 99℃, and keeping the temperature for 1h; (4) adding concentrated sulfuric acid to the solution obtained in step (3) to continue using the heat released by mixing concentrated sulfuric acid and water, and then heating to 100°C, and keeping the temperature for 0.5h; the mass ratio of vanadium pentoxide powder: concentrated sulfuric acid (total amount): oxalic acid is 1:2.88:0.8; (5) naturally cooling the solution obtained in step (4) to perform filtration to separate solid and liquid (filtration separation or centrifugal separation) to remove solid impurities, and to obtain the reduced 4-valence vanadium electrolyte, i.e. vanadyl sulfate solution; the molar ratio of vanadium to sulfur in the vanadyl sulfate solution is 1.65:4.3.

[0031] The 4-valence vanadium electrolyte of the present example is detected by using the oxidation-reduction titration method, and the residual oxalic acid in the obtained 4-valence vanadium electrolyte is as low as 0. Example 5

[0032] A method for preparing a 4-valence vanadium electrolyte with reduced residual reducing agent, comprising the following steps: (1) mixing concentrated sulfuric acid and water; the mass ratio of concentrated sulfuric acid (mass fraction of 98%, density of 1.84g / L) to water is 1:4.1; (2) immediately adding oxalic acid to the sulfuric acid aqueous solution obtained in step (1), and the mass ratio of sulfuric acid to oxalic acid (oxalic acid is oxalic acid dihydrate, mass fraction of 99.6%) is 1:4.2; (3) adding vanadium pentoxide powder to the solution obtained in step (2) to continue using the heat released by mixing oxalic acid and vanadium pentoxide to improve the reaction rate, and then heating to 98°C, and keeping the temperature for 0.8h; (4) adding concentrated sulfuric acid to the solution obtained in step (3) to continue using the heat released by mixing concentrated sulfuric acid and water, and then heating to 97°C, and keeping the temperature for 0.8h; the mass ratio of vanadium pentoxide powder: concentrated sulfuric acid (total amount): oxalic acid is 1:2.88:0.85; (5) naturally cooling the solution obtained in step (4) to perform filtration to separate solid and liquid (filtration separation or centrifugal separation) to remove solid impurities, and to obtain the reduced 4-valence vanadium electrolyte, i.e. vanadyl sulfate solution; the molar ratio of vanadium to sulfur in the vanadyl sulfate solution is 1.75:4.35.

[0033] The 4-valence vanadium electrolyte of the present example is detected by using the oxidation-reduction titration method, and the residual oxalic acid in the obtained 4-valence vanadium electrolyte is as low as 0.

[0034] The above examples are only used to illustrate but not to limit the technical solutions of the present application. Although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that the present application can still be modified or equivalently replaced without departing from the spirit and scope of the present application, and any modification or partial replacement should be covered in the scope of the claims of the present application.

Claims

1. A method for preparing a tetravalent vanadium electrolyte with reduced reducing agent residue, characterized in that: The preparation method comprises the following steps: (1) Mix concentrated sulfuric acid and water; the mass ratio of concentrated sulfuric acid to water is 1:3.8-4.1; (2) immediately adding oxalic acid to the aqueous sulfuric acid solution obtained in step (1), with the mass ratio of sulfuric acid to oxalic acid being 1:3.5-4.5; (3) adding vanadium pentoxide powder to the solution obtained in step (2) to continue utilizing the heat released by the mixing of oxalic acid and vanadium pentoxide to increase the reaction rate, and then heating to 95-100°C; (4) adding concentrated sulfuric acid to the solution obtained in step (3) to continue utilizing the heat released by the mixing of concentrated sulfuric acid and water, and heating to 95-100°C; (5) The solution obtained in step (4) is naturally cooled and filtered to obtain a reduced tetravalent vanadium electrolyte, i.e., a vanadyl sulfate solution.

2. The method for preparing a tetravalent vanadium electrolyte with reduced reducing agent residue according to claim 1, wherein: The method further comprises performing solid-liquid separation after the reaction is completed to remove solid impurities and obtain a tetravalent vanadium electrolyte solution.

3. The method for preparing a tetravalent vanadium electrolyte with reduced reducing agent residue according to claim 2, wherein: The separation is performed by filtration separation or centrifugal separation.

4. A method for preparing a tetravalent vanadium electrolyte with reduced reducing agent residue according to any one of claims 1 to 3, characterized in that: Both steps (3) and (4) need to be heated to 95-100°C for 0.5-1h.

5. A method for preparing a tetravalent vanadium electrolyte with reduced reducing agent residue according to any one of claims 1 to 3, characterized in that: The mass fraction of concentrated sulfuric acid added in step (4) is 96-98%, and the density is 1.82-1.85 g / L.

6. A method for preparing a tetravalent vanadium electrolyte with reduced reducing agent residue according to any one of claims 1 to 3, characterized in that: In the method, the mass ratio of vanadium pentoxide powder: concentrated sulfuric acid: oxalic acid is 1:2.88:0.7-0.9, and the concentrated sulfuric acid is the total amount of concentrated sulfuric acid.

7. A method for preparing a tetravalent vanadium electrolyte with reduced reducing agent residue according to any one of claims 1 to 3, characterized in that: The oxalic acid is oxalic acid dihydrate, with a mass fraction of ≥99.6%.

8. A method for preparing a tetravalent vanadium electrolyte with reduced reducing agent residue according to any one of claims 1 to 3, characterized in that: The molar ratio of vanadium to sulfur in the vanadyl sulfate solution is 1.7±0.05:4.3±0.

05.

9. Use of the tetravalent vanadium electrolyte obtained by the method for preparing a tetravalent vanadium electrolyte with reduced reducing agent residue according to any one of claims 1 to 8 as an electrolyte for vanadium batteries.