A method for preparing vanadyl sulfate crystal based on salting-out-salting-in combined crystallization

Abstract

The application discloses a method for preparing vanadyl sulfate crystals based on salting-out-solvent-out combined crystallization, specifically comprising the following steps: adding solid ammonium sulfate into a vanadyl sulfate solution, wherein the molar ratio of the vanadyl sulfate to the solid ammonium sulfate is n 硫酸氧钒 ∶n 硫酸铵 =6:1~10:1, and stirring to fully dissolve the solid ammonium sulfate; then, adding ethanol into the solution according to a volume ratio of V 硫酸氧钒溶液 :V 乙醇 =4:1~10:1, continuing to stir after the addition of the ethanol is completed, and allowing the crystals to be analyzed and separated out; filtering, washing and drying the crystals, and thus vanadyl sulfate crystals are obtained. The method can realize efficient crystallization of vanadyl sulfate at room temperature, and in the process of the crystallization of the vanadyl sulfate, external heating or heat removal is not needed, energy consumption is significantly reduced, and through recycling of the filtrate and the washing liquid, organic solvent emission can be effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, specifically relating to a method for preparing vanadium oxysulfate crystals based on salting-dissolution composite crystallization. Background Technology

[0002] Vanadyl sulfate (VOSO4) is a key active substance in vanadium oxysulfate electrolytes. Currently, it is mainly prepared industrially using a solution method. This involves placing vanadium-containing raw materials, sulfuric acid, and solid or gaseous reducing agents in a reaction vessel, heating and stirring to promote the oxidation of vanadium. 5+ The reduction process yields vanadium oxysulfate solution; however, transporting vanadium oxysulfate solution is costly. Therefore, developing a crystallization process for vanadium oxysulfate is of great significance for reducing transportation and storage costs.

[0003] Currently, the main methods for preparing solid vanadium oxysulfate are evaporation crystallization and cooling crystallization. Evaporation crystallization often yields a high-viscosity, sticky solid, making it difficult to obtain well-structured crystals, and the evaporation process generates a large amount of acid gas, which can easily cause air pollution. Cooling crystallization, on the other hand, suffers from problems such as long crystallization time, low crystallization temperature, and high energy consumption. Therefore, exploring a suitable crystallization process is of great significance for the preparation of solid vanadium oxysulfate.

[0004] Patent application CN 117383612 A discloses a method for preparing solid vanadium oxysulfate. The method involves adding a trace amount of reducing agent (V₂(SO₄)₃, oxalic acid, V₂O₃, or sodium sulfite) to a vanadium oxysulfate solution before crystallization. Solid vanadium oxysulfate is then obtained through vacuum distillation, crystallization filtration, and drying. The addition of the trace reducing agent raises the drying temperature of vanadium oxysulfate to 60-95°C, achieving a higher drying temperature and shorter drying time, while also ensuring that vanadium oxysulfate is not oxidized to the pentavalent vanadium intermediate state at higher drying temperatures. However, during the concentration of the vanadium oxysulfate solution, the increased solid-liquid ratio of the slurry leads to a sharp increase in viscosity, resulting in poor slurry flowability, difficulty in filtration, and the tendency for crystals to be mixed with mother liquor or impurities during crystallization, thus affecting product purity and vanadium precipitation rate.

[0005] Patent CN 103420415 B discloses a method for preparing vanadium oxysulfate. The method involves removing the solvent from a vanadium oxysulfate solution by vacuum distillation until the solvent is no longer easily concentrated, then stopping the evaporation. The resulting paste-like vanadium oxysulfate is then dispersed in an alcohol solvent, allowed to settle for 1-2 hours, and the solution is separated to obtain solid vanadium oxysulfate. This method uses vacuum distillation to remove some of the solvent and then uses an alcohol solvent as a dispersant to promote the sedimentation of vanadium oxysulfate. However, the dispersion process requires a large amount of alcohol solvent, resulting in the generation of a large amount of organic waste liquid, and the vacuum distillation solvent removal process is energy-intensive. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing vanadium oxysulfate crystals based on salting-dissolution composite crystallization. Using this method, efficient crystallization of vanadium oxysulfate can be achieved at room temperature.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing vanadium oxysulfate crystals based on salting-out and dissolution composite crystallization specifically involves adding solid ammonium sulfate to a vanadium oxysulfate solution, wherein the molar ratio of vanadium oxysulfate to solid ammonium sulfate is n. 硫酸氧钒 ∶n 硫酸铵 =6:1~10:1, stir for 1~2 hours to ensure complete dissolution; then proceed according to V 硫酸氧钒溶液 V 乙醇 Ethanol is added dropwise to the solution at a volume ratio of 4:1 to 10:1. After the addition is complete, stirring is continued to allow the crystals to fully separate out. The solution is then filtered, and the crystals are washed and dried to obtain vanadium oxysulfate crystals.

[0008] Furthermore, the concentration C of vanadium in the vanadium oxysulfate solution of the present invention is... V =4~8 mol / kg water.

[0009] Furthermore, this invention uses ethanol as a washing agent to wash the vanadium oxysulfate crystals in small amounts multiple times. After washing, the resulting vanadium oxysulfate is dried in a vacuum oven. The washing liquid and filtrate can be collected for the next batch of vanadium oxysulfate crystallization experiments to reduce the amount of ethanol and ammonium sulfate used in the crystallization process, while excess waste liquid is treated through an ammonium recovery device.

[0010] Further, the preparation method of the vanadium oxysulfate solution of the present invention is as follows: Premixed solid oxalic acid and vanadium pentoxide are added to a sulfuric acid solution at 60-70°C with an initial concentration of 8.5-10.0 mol / L; after the addition is complete, the reaction system is heated to 95-100°C and kept at this temperature for 14-16 hours; after the reaction is complete, insoluble impurities are removed by hot filtration, and the filtrate is the vanadium oxysulfate solution. This method uses vanadium pentoxide as the vanadium source, concentrated sulfuric acid as the sulfur source and solvent to promote the dissolution of V₂O₅, and solid oxalic acid as the reducing agent to dissolve the pentavalent vanadium (VO₂). + Reduced to tetravalent vanadium VO 2+ This process yields a vanadium oxysulfate solution.

[0011] Furthermore, the molar ratio n of vanadium pentoxide to sulfuric acid in the sulfuric acid solution of the present invention is... 五氧化二钒 ∶n 硫酸 =0.35:1~0.47:1.

[0012] Furthermore, the molar ratio n of vanadium pentoxide to oxalic acid in this invention is... 五氧化二钒 ∶n 草酸=1:1~1:1.2.

[0013] Furthermore, the addition rate of oxalic acid solid and vanadium pentoxide in this invention is controlled at 1.5~3.5 g / min to avoid the oxalic acid decomposing violently and generating a large amount of gas due to excessively rapid addition, which would cause the reaction solution to foam and overflow.

[0014] The inventive principle and beneficial technical effects of this invention are as follows: This invention is based on the fact that ammonium sulfate has a significantly higher solubility in water or sulfuric acid solution than vanadium oxysulfate at room temperature. Ammonium sulfate solid is used as a salting-out agent to dissolve it in vanadium oxysulfate solution, effectively promoting the crystallization of vanadium oxysulfate. Then, ethanol is used as a solvent to further reduce the solubility of vanadium oxysulfate in the solvent and promote the crystallization of vanadium oxysulfate.

[0015] This invention employs a combination of salting-out crystallization and dissolution crystallization. By optimizing the addition amount of concentrated sulfuric acid, the feeding ratio and feeding rate of vanadium pentoxide and oxalic acid, as well as the dosage of salting-out agent and dissolution agent, vanadium oxysulfate can crystallize at room temperature, significantly reducing the energy consumption of the crystallization process. Furthermore, by recycling the filtrate and washing liquid, the large-scale discharge of organic solvents is reduced. Attached Figure Description

[0016] Figure 1 The image shows the vanadium oxysulfate product prepared in Example 1.

[0017] Figure 2 The image shows the XRD pattern of the vanadium oxysulfate product prepared in Example 1. Detailed Implementation

[0018] To better understand the present invention, the present invention will be described in detail below with reference to embodiments. Example 1

[0019] The method for preparing vanadium oxysulfate crystals in this embodiment is as follows: (1) Preparation of vanadium pentoxide solution: Add a certain amount of water to a double-walled glass reactor, start stirring, then slowly add a certain amount of concentrated sulfuric acid and mix evenly to obtain a sulfuric acid solution with a concentration of 8.5 mol / L; after heating the sulfuric acid solution to 65℃, according to the molar ratio of vanadium pentoxide to sulfuric acid in the sulfuric acid solution n 五氧化二钒 ∶n 硫酸 =0.4∶1, the molar ratio of vanadium pentoxide to oxalic acid, n 五氧化二钒 ∶n 草酸With a feed ratio of 1:1.05, premixed solid oxalic acid and vanadium pentoxide were uniformly added to sulfuric acid solution at a feed rate of 2 g / min. The vanadium concentration in the vanadium oxysulfate solution was adjusted to 6.8 mol / L by adjusting the amount of water added. After the addition was completed, the reaction system was heated to 99℃ and kept at that temperature for 14 h. After the reaction was completed, insoluble impurities were removed by hot filtration to obtain a vanadium oxysulfate solution with a vanadium concentration of 6.8 mol / L.

[0020] (2) Preparation of vanadium oxysulfate crystals: according to the molar ratio of vanadium oxysulfate to ammonium sulfate solid n 硫酸氧钒 ∶n 硫酸铵 Ammonium sulfate solid was added to the above vanadium oxysulfate solution in a ratio of 6:1. After stirring for 1 h, ethanol was slowly added dropwise as a solvent, maintaining a volume ratio of vanadium oxysulfate solution to ethanol of 8:1. Stirring was continued for 5 h to allow the crystals to fully precipitate. Subsequently, the crystals were filtered, washed, and dried to obtain blue vanadium oxysulfate solid.

[0021] The vanadium oxysulfate product prepared in this embodiment and its XRD pattern are shown below. Figure 1 and Figure 2 As shown. By Figure 1 As can be seen, the vanadium oxysulfate prepared by crystallization in this embodiment is blue; from Figure 2 It can be seen that the XRD pattern of the vanadium oxysulfate prepared by this crystallization is consistent with the standard card of VOSO4·3H2O (PDF#27-0950), indicating that vanadium oxysulfate crystals can be successfully prepared by the salting-dissolution composite crystallization method.

[0022] The vanadium oxysulfate products prepared in the other examples and their XRD patterns are the same as in Example 1, and will not be provided one by one. Example 2

[0023] The method for preparing vanadium oxysulfate crystals in this embodiment is as follows: (1) Preparation of vanadium pentoxide solution: Add a certain amount of water to a double-walled glass reactor, start stirring, then slowly add a certain amount of concentrated sulfuric acid and mix evenly to obtain a sulfuric acid solution with a concentration of 9.5 mol / L; heat the sulfuric acid solution to 65℃, and add vanadium pentoxide to the sulfuric acid solution according to the molar ratio n 五氧化二钒 ∶n 硫酸 =0.47∶1, the molar ratio of vanadium pentoxide to oxalic acid, n 五氧化二钒 ∶n 草酸The premixed solid oxalic acid and vanadium pentoxide were uniformly added to the sulfuric acid solution at a feeding rate of 1.5 g / min at a ratio of 1:1. The vanadium concentration in the vanadium oxysulfate solution was adjusted to 8 mol / L by adjusting the amount of water added. After the addition was completed, the reaction system was heated to 95℃ and kept at that temperature for 16 h. After the reaction was completed, the insoluble impurities were removed by hot filtration to obtain a vanadium oxysulfate solution with a vanadium concentration of 8 mol / L.

[0024] (2) Preparation of vanadium oxysulfate crystals: according to the molar ratio of vanadium oxysulfate to ammonium sulfate solid n 硫酸氧钒 ∶n 硫酸铵 Ammonium sulfate solid was added to the above vanadium oxysulfate solution in a ratio of 8:1. After stirring for 1 h, ethanol was slowly added dropwise as a solvent, maintaining a volume ratio of vanadium oxysulfate solution to ethanol of 10:1. Stirring was continued for 5 h to allow the crystals to fully precipitate. The crystals were then filtered, washed, and dried to obtain blue vanadium oxysulfate solid. Example 3

[0025] The method for preparing vanadium oxysulfate crystals in this embodiment is as follows: (1) Preparation of vanadium pentoxide solution: Add a certain amount of water to a double-walled glass reactor, start stirring, then slowly add a certain amount of concentrated sulfuric acid and mix evenly to obtain a sulfuric acid solution with a concentration of 9.2 mol / L; heat the sulfuric acid solution to 65℃, and add vanadium pentoxide to the sulfuric acid solution according to the molar ratio n 五氧化二钒 ∶n 硫酸 =0.35∶1, the molar ratio of vanadium pentoxide to oxalic acid, n 五氧化二钒 ∶n 草酸 At a feed ratio of 1:1.1, premixed solid oxalic acid and vanadium pentoxide were uniformly added to a sulfuric acid solution at a feed rate of 3.5 g / min. The vanadium concentration in the vanadium oxysulfate solution was adjusted to 6.0 mol / L by adjusting the amount of water added. After the addition was complete, the reaction system was heated to 98℃ and kept at that temperature for 15 h. After the reaction was completed, insoluble impurities were removed by hot filtration to obtain a vanadium oxysulfate solution with a vanadium concentration of 6.0 mol / L.

[0026] (2) Preparation of vanadium oxysulfate crystals: according to the molar ratio of vanadium oxysulfate to ammonium sulfate solid n 硫酸氧钒 ∶n 硫酸铵 Ammonium sulfate solid was added to the above vanadium oxysulfate solution in a ratio of 10:1. After stirring for 1.5 h, ethanol was slowly added dropwise as a solvent, controlling the volume ratio of vanadium oxysulfate solution to ethanol at 4:1. Stirring was continued for 5 h to allow the crystals to fully precipitate. Subsequently, the crystals were filtered, washed, and dried to obtain blue vanadium oxysulfate solid. Example 4

[0027] The method for preparing vanadium oxysulfate crystals in this embodiment is as follows: (1) Preparation of vanadium pentoxide solution: Add a certain amount of water to a double-walled glass reactor, start stirring, then slowly add a certain amount of concentrated sulfuric acid and mix evenly to obtain a sulfuric acid solution with a concentration of 10.0 mol / L; heat the sulfuric acid solution to 65℃, and add vanadium pentoxide to the sulfuric acid solution according to the molar ratio n 五氧化二钒 ∶n 硫酸 =0.42∶1, the molar ratio of vanadium pentoxide to oxalic acid, n 五氧化二钒 ∶n 草酸 With a feed ratio of 1:1.14, premixed solid oxalic acid and vanadium pentoxide were uniformly added to sulfuric acid solution at a feed rate of 1.8 g / min. The vanadium concentration in the vanadium oxysulfate solution was adjusted to 7.2 mol / L by adjusting the amount of water added. After the addition was completed, the reaction system was heated to 99℃ and kept at that temperature for 15 h. After the reaction was completed, insoluble impurities were removed by hot filtration to obtain a vanadium oxysulfate solution with a vanadium concentration of 7.2 mol / L.

[0028] (2) Preparation of vanadium oxysulfate crystals: according to the molar ratio of vanadium oxysulfate to ammonium sulfate solid n 硫酸氧钒 ∶n 硫酸铵 Ammonium sulfate solid was added to the above vanadium oxysulfate solution in a ratio of 7:1. After stirring for 1 hour, ethanol was slowly added dropwise as a solvent, maintaining a volume ratio of vanadium oxysulfate solution to ethanol of 6:1. Stirring was continued for 5 hours to allow the crystals to fully precipitate. The crystals were then filtered, washed, and dried to obtain blue vanadium oxysulfate solid. Comparative Example 1

[0029] The method for preparing vanadium oxysulfate crystals in this comparative example is as follows: (1) Preparation of vanadium oxysulfate solution: The method is the same as in Example 1.

[0030] (2) Preparation of vanadium oxysulfate crystals: The vanadium oxysulfate solution prepared in step (1) was placed in a double-layered glass reactor, stirred, and cooled to 5°C for 6 h to crystallize. After standing at 10°C for 12 h, no crystals were found to precipitate. Subsequently, the cooling was continued to crystallize at 5°C for 12 h, and after standing at 10°C for 48 h, no crystals were found to precipitate. Comparative Example 2

[0031] The method for preparing vanadium oxysulfate crystals in this comparative example is as follows: (1) Preparation of vanadium oxysulfate solution: The method is the same as in Example 1.

[0032] (2) Preparation of vanadium oxysulfate crystals: Place the vanadium oxysulfate solution prepared in step (1) in a beaker, and add vanadium oxysulfate to ammonium sulfate solid according to the molar ratio n 硫酸氧钒 ∶n 硫酸铵Ammonium sulfate solid was added in a ratio of 6:1. After stirring for 12 hours and standing for 8 hours, no vanadium oxysulfate crystals were observed to precipitate. Comparative Example 3

[0033] The method for preparing vanadium oxysulfate crystals in this comparative example is as follows: (1) Preparation of vanadium oxysulfate solution: The method is the same as in Example 1.

[0034] (2) Preparation of vanadium oxysulfate crystals: Place the vanadium oxysulfate solution prepared in step (1) in a beaker, slowly add ethanol, control the volume ratio of vanadium oxysulfate solution to ethanol to be 4:1, stir for 6 h, let stand for 12 h, and find that only a small amount of crystals precipitate. Comparative Example 4

[0035] The method for preparing vanadium oxysulfate crystals in this comparative example is as follows: (1) Preparation of vanadium oxysulfate solution: The method is the same as in Example 1.

[0036] (2) Preparation of vanadium oxysulfate crystals: The vanadium oxysulfate solution prepared in step (1) was placed in a beaker, and concentrated sulfuric acid was slowly added dropwise as a salting-out agent. The volume ratio of vanadium oxysulfate solution to concentrated sulfuric acid was controlled to be 20:3. After stirring for 8 h, no crystals were found to precipitate.

[0037] As can be seen from the above examples and comparative examples, neither cooling crystallization alone, nor the addition of a salting-out agent (ammonium sulfate) or a solvent (ethanol) can effectively induce vanadium oxysulfate crystallization. Therefore, combining salting-out crystallization with solvent crystallization is the key to achieving efficient vanadium oxysulfate crystallization.

[0038] The present invention has been described in detail through embodiments. Those skilled in the art cannot achieve the technical effects described in this invention by modifying or appropriately altering and combining the methods described herein. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered part of this invention.

Claims

1. A method for preparing vanadium oxysulfate crystals based on salting-out and dissolution composite crystallization, characterized in that, Ammonium sulfate solid is added to a vanadium oxysulfate solution, wherein the molar ratio of vanadium oxysulfate to ammonium sulfate solid is n. 硫酸氧钒 ∶n 硫酸铵 The ratio of the solvent mixture is 6:1 to 10:1; stir until fully dissolved; then follow the steps outlined in V. 硫酸氧钒溶液 V 乙醇 Ethanol is added dropwise to the solution at a volume ratio of 4:1 to 10:

1. After the addition is complete, stirring is continued to allow the crystals to fully separate out. The solution is then filtered, and the crystals are washed and dried to obtain vanadium oxysulfate crystals.

2. The method for preparing vanadium oxysulfate crystals based on salting-out and dissolution composite crystallization according to claim 1, characterized in that, The concentration C of vanadium in the vanadium oxysulfate solution V =4~8 mol / kg water.

3. The method for preparing vanadium oxysulfate crystals based on salting-out and dissolution composite crystallization according to claim 1, characterized in that, The washing process uses ethanol as the detergent, and the vanadium oxysulfate crystals are washed in small amounts multiple times.

4. The method for preparing vanadium oxysulfate crystals based on salting-out and dissolution composite crystallization according to claim 1, characterized in that, The preparation method of the vanadium oxysulfate solution is as follows: premixed solid oxalic acid and vanadium pentoxide are added to a sulfuric acid solution at 60-70℃ with an initial concentration of 8.5-10.0 mol / L; after the addition is complete, the reaction system is heated to 95-100℃ and kept at that temperature for 14-16 hours; after the reaction is completed, insoluble impurities are removed by hot filtration, and the filtrate is a vanadium oxysulfate solution.

5. The method for preparing vanadium oxysulfate crystals based on salting-out and dissolution composite crystallization according to claim 4, characterized in that, The molar ratio n of vanadium pentoxide to sulfuric acid in the sulfuric acid solution 五氧化二钒 ∶n 硫酸 =0.35:1~0.47:

1.

6. The method for preparing vanadium oxysulfate crystals based on salting-out and dissolution composite crystallization according to claim 4, characterized in that, The molar ratio n of vanadium pentoxide to oxalic acid 五氧化二钒 ∶n 草酸 =1:1~1:1.

2.

7. A method for preparing vanadium oxysulfate crystals based on salting-out and dissolution composite crystallization according to claim 4, characterized in that, The addition rate of the oxalic acid solid and vanadium pentoxide is controlled at 1.5~3.5 g / min.

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