Benzopyrazine fluorenone derivatives, and preparation method and application thereof

Abstract

The application discloses a kind of benzo pyrazine fluorenone derivatives.The compound is composed of pyrazine and fluorenone two molecules, can accept six electrons.The benzo pyrazine fluorenone derivative of the application can be used as negative electrode active material in organic liquid flow battery, compared with single pyrazine, fluorenone molecule, the molecule greatly improves the energy density of liquid flow battery.The compound of the application has larger molecular size, which helps to reduce the permeability between positive and negative electrodes, increase the battery life.Two carboxyl groups and other solubilizing groups are easily soluble in alkaline aqueous solution, further improving the energy density of liquid flow battery.The assembled organic liquid flow battery has wide application background in the field of renewable energy scale power storage and grid peak shaving.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage, and relates to a class of benzopyrazine fluorenone derivatives, their preparation methods and applications. Background Technology

[0002] With the increase in newly installed capacity, the proportion of photovoltaic and wind power in the energy mix will rise significantly, and they are expected to become the dominant energy sources in the future. However, their inherent intermittency and volatility pose new challenges to the stable output of traditional power grids. Therefore, there is an urgent need for cost-effective, safe, reliable, and scalable power storage systems to effectively mitigate the volatility caused by large-scale renewable energy generation being integrated into the grid, promote the balance of power sources and loads in power system operation, and improve the safety, economy, and flexibility of grid operation.

[0003] Among numerous energy storage systems, redox flow batteries (RFBs) are a promising energy storage technology. Their battery power and energy storage capacity can be designed independently, there are no solid-phase reactions, no changes in the electrode material structure, and they are inexpensive, have a long lifespan, high reliability, and low operating and maintenance costs, thus leading to their rapid development. Aqueous organic redox flow batteries (AORFBs) based on non-flammable electrolytes dissolve organic active molecules in aqueous solutions, rather than in flammable and expensive organic solvents, making them safer to operate and more suitable for large-scale energy storage. Furthermore, aqueous organic flow batteries have high electrolyte conductivity, fast electrochemical reaction rates, and high output power. However, most organic active molecules involve single-electron or two-electron transfer processes, and their solubility does not exceed 3 mol·L⁻¹. -1 (i.e., capacity not exceeding 80.4 A·h·L) -1 However, energy density is limited. Improving the solubility of active molecules by selecting appropriate functional groups often has little effect; therefore, there is an urgent need to develop more organic active molecules that can transfer electrons (>2 electrons). Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, one of the objectives of this invention is to provide a class of benzopyrazine fluorenone derivatives. The charging and discharging process of these compounds involves multiple electron transfers, which can significantly improve the energy density of flow batteries, reduce the permeability between the positive and negative electrodes, and increase battery life.

[0005] The second objective of this invention is to provide a method for preparing the above-mentioned benzopyrazine fluorenone derivative.

[0006] A third objective of this invention is to provide the application of the above-mentioned benzopyrazine fluorenone derivative in organic flow batteries.

[0007] The benzopyrazine fluorenone derivatives described in this invention have the general structural formula shown in Figure I:

[0008]

[0009] R1, R2, R3, and R4 are selected from COOH, CH2COOH, and CH2(CH2). n COOH, n=1-3; SO3H, CH2SO3H; OH; O(CH2CH2O) n H, n = 1-3; NH(CH2) n COOH, n=1-3, NHCH(CH3)COOH; O(CH2) n COOH, n = 1-3. Among them, R1, R2, R3 and R4 can be the same or different, and also include sodium salts, potassium salts, ammonium salts and lithium salts of all structures.

[0010] The preparation method of a class of benzopyrazine fluorenone derivatives according to the present invention comprises the following steps:

[0011]

[0012] (1) Add cyclopentazone, 3,4-diaminobenzene derivative and solvent to the reaction vessel and heat to reflux; after the reaction is completed, cool to room temperature, filter, wash and dry to obtain crude product of benzopyrazine fluorenone derivative;

[0013] (2) Add the crude product of benzopyrazine fluorenone derivative obtained in step (1) and dilute nitric acid to a reaction vessel, stir and mix, heat and react for 1-5 hours, then cool to room temperature, filter, wash and dry to obtain pure benzopyrazine fluorenone derivative.

[0014] The method for preparing a class of benzopyrazine fluorenone derivatives according to the present invention, wherein in step (1), the molar ratio of cyclopentazone and 3,4-diaminobenzene derivative is 1:2-1:5, the substrate concentration is 0.01-1M, and the solvent is one, two or more of acetic acid, methanol, ethanol, isopropanol, water, etc.

[0015] In the preparation method of a class of benzopyrazine fluorenone derivatives of the present invention, in step (2), the concentration of dilute nitric acid is 20%-40% and the reaction temperature is 120-140℃.

[0016] The application of a class of benzopyrazine fluorenone derivatives described in this invention in organic flow batteries, wherein the battery composition is as follows:

[0017] The benzopyrazine fluorenone derivatives described in this invention can be used as negative electrode materials in organic flow batteries, forming alkaline or neutral organic flow batteries with positive electrode active materials. The positive electrode material can be potassium iodide, potassium ferricyanide, tetramethylpiperidine oxide, or hydroquinone derivatives; the electrolyte in the alkaline organic flow battery is sodium hydroxide, potassium hydroxide, lithium hydroxide, or sodium carbonate; the electrolyte in the neutral organic flow battery is sodium chloride, lithium chloride, or ammonium chloride.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention provides a class of benzopyrazine fluorenone derivatives, which are composed of fluorenone and pyrazine molecules and can accept six electrons. As a negative electrode material for aqueous organic flow batteries, they can significantly improve the battery's energy density. To date, six-electron system negative electrode active materials have been rarely reported. This invention also provides a method for preparing the above-mentioned compounds, which is simple and requires mild and environmentally friendly conditions.

[0020] This invention also provides the application of the above-mentioned compound as a negative electrode active material in organic flow batteries. The molecular size of this compound is significantly larger than that of a single pyrazine or fluorenone molecule, reducing the permeability between the positive and negative electrodes and increasing battery life. Its carboxyl and other solubilizing groups are readily soluble in alkaline aqueous solutions, further improving the energy density of the flow battery. The benzopyrazine fluorenone derivative of this invention, as a negative electrode active material in aqueous organic flow batteries, when assembled with positive electrode active materials to form organic flow batteries, has broad application prospects in large-scale renewable energy storage and grid peak shaving. Attached Figure Description

[0021] Figure 1 This is a cyclic voltammetry curve of benzopyrazine fluorenone dioic acid as the negative electrode active material of the present invention;

[0022] Figure 2 This is a Levich curve of benzopyrazine fluorenone dioic acid as the negative electrode active material of the present invention;

[0023] Figure 3 This is a battery charge-discharge test diagram of the flow battery composed of benzopyrazine fluorenidone dicarboxylic acid and K4[Fe(CN)6] of the present invention. Detailed Implementation

[0024] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0025] Example 1

[0026] A benzopyrazine fluorenone dicarboxylic acid compound, the preparation process of which includes the following steps:

[0027]

[0028] Add 840 mg of cyclopentazone, 2 g of 3,4-diaminobenzoic acid, and 120 ml of acetic acid to a 250 ml round-bottom flask. Reflux the mixture for 24 h, cool to room temperature, precipitate a solid, filter, wash with water and ethanol, and dry to obtain crude benzopyrazine fluorenone dicarboxylic acid.

[0029] The crude product was mixed with 35% dilute nitric acid and heated for 3 hours. After cooling to room temperature, a yellow solid precipitated out. The solid was filtered, washed with water and ethanol, and dried under vacuum to obtain the product benzopyrazine fluorenone dicarboxylic acid, with a yield of 55%.

[0030] Example 2

[0031] A benzopyrazine fluorenone tetracarboxylic acid compound, the preparation process of which includes the following steps:

[0032]

[0033] Add 840 mg of cyclopentazone, 2.9 g of 3,4-diaminophthalic acid, and 60 ml of acetic acid to a 250 ml round-bottom flask. Reflux the mixture for 48 h, cool to room temperature, precipitate a solid, filter, wash with water and ethanol, and dry to obtain crude benzopyrazine fluorenone tetracarboxylic acid.

[0034] The crude product was mixed with 40% dilute nitric acid and heated for 5 hours. After cooling to room temperature, a yellow solid precipitated out. The solid was filtered, washed with water and ethanol, and dried under vacuum to obtain the product benzopyrazine fluorenone tetracarboxylic acid, with a yield of 45%.

[0035] Example 3

[0036]

[0037] Add 840 mg of cyclopentazone, 2 g of 3,4-diaminobenzoic acid, 30 ml of acetic acid, and 30 ml of ethanol to a 250 ml round-bottom flask. Reflux the mixture for 36 h, cool to room temperature, precipitate a solid, filter, wash with water and ethanol, and dry to obtain crude benzopyrazine fluorenone dicarboxylic acid.

[0038] The crude product was mixed with 35% dilute nitric acid and heated for 5 hours. After cooling to room temperature, a yellow solid precipitated out. The solid was filtered, washed with water and ethanol, and dried under vacuum to obtain the product benzopyrazine fluorenone dicarboxylic acid, with a yield of 50%.

[0039] Example 4

[0040]

[0041] Add 840 mg of cyclopentazone, 2.5 g of 3,4-diaminobenzenesulfonic acid, 30 ml of acetic acid, and 30 ml of ethanol to a 250 ml round-bottom flask. Reflux the mixture for 24 h, cool to room temperature, precipitate a solid, filter, wash with water and ethanol, and dry under vacuum to obtain crude benzopyrazine fluorenone sulfonic acid.

[0042] The crude product was mixed with 30% dilute nitric acid and heated for 2 hours. After cooling to room temperature, a yellow solid precipitated out. The solid was filtered, washed with water and ethanol, and dried under vacuum to obtain the product benzopyrazine fluorenone dicarboxylic acid, with a yield of 35%.

[0043] The electrochemical and battery performance test results of benzopyrazine fluorenidone dicarboxylic acid are as follows:

[0044] Figure 1 The figure shows the cyclic voltammetry curve of the benzopyrazine fluorenidone dicarboxylic acid prepared in this invention as the negative electrode active material. The electrolyte is an aqueous solution of potassium hydroxide with a concentration of 1 mol / L. Benzopyrazine fluorenidone dicarboxylic acid is added to dissolve it, resulting in a concentration of 2 mmol / L. As shown in the figure, the flow battery exhibits four pairs of reversible redox peaks at different scan rates (where fluorenone undergoes a two-step, two-electron process). With increasing scan rate, the oxidation peak potential becomes more positive, and the reduction peak potential becomes more negative. This indicates that the six-electron benzopyrazine fluorenidone dicarboxylic acid prepared in this invention has good electrochemical reversibility, and the provided six-electron charge-discharge system significantly improves the energy density of the battery.

[0045] Figure 2 The figure shows the Levich curve of the six-electron benzopyrazine fluorenone dicarboxylic acid prepared in this invention as the negative electrode active material. As can be seen from the figure, the limiting current and ω... 1 / 2 The graph shows a linear relationship, indicating that the redox process of benzopyrazine fluorenidone dicarboxylic acid is a quasi-reversible reaction. The reversible chemical equations for the gain and loss of six electrons in the six-electron benzopyrazine fluorenidone dicarboxylic acid obtained in this invention are shown below.

[0046]

[0047] Figure 3 This figure shows the charge-discharge test results of the flow battery composed of benzopyrazine fluorenidone diacid prepared in this invention and K4[Fe(CN)6]. As can be seen from the figure, the battery efficiency is relatively stable in the alkaline system, with coulombic efficiency and energy efficiency consistently above 99%. The battery capacity increases with decreasing charge / discharge current, and the capacity retention rate is approximately 80%.

[0048] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the invention shall fall within the scope of protection claimed by the present invention.

Claims

1. The application of a benzopyrazine fluorenone dicarboxylic acid compound, wherein the structural formula of the benzopyrazine fluorenone dicarboxylic acid compound is: Its characteristics are, The benzopyrazine fluorenone dicarboxylic acid compound is used as the negative electrode active material in organic flow batteries; The benzopyrazine fluorenone dicarboxylic acid compound and the positive electrode active material form an alkaline or neutral organic flow battery; The positive electrode active material is selected from potassium iodide, potassium ferricyanide, or tetramethylpiperidine oxide. The electrolyte in the alkaline organic flow battery is sodium hydroxide, potassium hydroxide, lithium hydroxide, or sodium carbonate. The electrolyte in the neutral organic flow battery is sodium chloride, lithium chloride, or ammonium chloride.

2. The application of the benzopyrazine fluorenone dicarboxylic acid compound as described in claim 1, characterized in that, The preparation method of the benzopyrazine fluorenone dicarboxylic acid compound includes the following steps: (1) Add cyclopentazone, 3,4-diaminobenzoic acid and solvent to the reaction vessel and heat to reflux; after the reaction is completed, cool to room temperature, filter, wash and dry to obtain crude benzopyrazine fluorenone dicarboxylic acid; (2) Add the crude product of benzopyrazine fluorenidone dicarboxylic acid obtained in step (1) and dilute nitric acid to the reaction vessel, stir and mix, heat and react for 1-5 hours, then cool to room temperature, filter, wash and dry to obtain pure benzopyrazine fluorenidone dicarboxylic acid; In step (1), the molar ratio of cyclopentazone to 3,4-diaminobenzoic acid is 1:2-1:5, and the substrate concentration is 0.01-1M. The solvent is one, two, or more of acetic acid, methanol, ethanol, isopropanol, and water; In step (2), the concentration of dilute nitric acid is 20%-40%, and the reaction temperature is 120-140℃.

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