Method for preparing high-purity vanadium powder by molten salt electrolysis

Abstract

The application provides a method for preparing high-purity vanadium powder by molten salt electrolysis, which comprises the following steps: placing dehydrated vanadium pentoxide into molten salt to perform a reduction reaction, and after the reaction is completed, performing cleaning and solid-liquid separation to obtain metallic vanadium; and sequentially performing annealing treatment, vacuum dehydrogenation and grinding treatment on the metallic vanadium to obtain the high-purity vanadium powder. The technical scheme realizes efficient and rapid preparation of metallic vanadium, and the obtained product has high purity, a single phase and uniform particles. The process is environmentally friendly and non-polluting, avoids the use of traditional strong acid / alkali electrolyte, reduces the harm to equipment and environment, simultaneously does not require special electrolysis equipment, effectively reduces the production cost, and is simple to operate and easy to scale up.

Description

Technical Field

[0001] This invention relates to the field of electrolytic metal preparation technology, and in particular to a method for preparing high-purity vanadium powder by molten salt electrolysis. Background Technology

[0002] Vanadium, as a key strategic material, is increasingly widely used in aerospace, nuclear engineering, and new battery manufacturing, driven by the rapid development of modern high-tech industries. However, current mainstream vanadium preparation processes, primarily traditional metallurgical techniques such as the aluminothermic, silicothermic, and carbothermic methods, generally rely on extremely high reaction temperatures and pressures, resulting in enormous energy consumption and often severe environmental pollution. More importantly, the products obtained by these methods often suffer from inherent problems such as limited purity, complex phase composition, and uneven particle morphology and size distribution, making it difficult to meet the stringent performance requirements of high-end applications.

[0003] To address these issues, researchers have turned their attention to electrolysis, a highly promising preparation method. Compared to traditional thermal reduction, electrolysis can theoretically be carried out under relatively mild physical conditions and is expected to directly yield vanadium metal with higher purity, a single phase, and regular particle morphology, thus attracting considerable attention. However, most existing electrolysis technologies rely on strong acid (such as hydrochloric acid and sulfuric acid) or strong alkali (such as sodium hydroxide) systems as electrolytes. This leads to severe chemical corrosion of the electrolytic cell and related components, significantly shortening equipment lifespan and increasing maintenance costs. Furthermore, the disposal of waste electrolytes poses serious environmental challenges, potentially causing water and soil pollution, which contradicts the development concept of green manufacturing.

[0004] Despite the advantages of electrolysis in principle, current electrolytic preparation processes still have several significant drawbacks that hinder their industrial-scale adoption. First, there is the issue of efficiency: the current efficiency or space-time yield of existing electrolytic processes is often low, and the reaction time is long, resulting in low output per unit of energy consumption and making it difficult to achieve efficient, continuous, large-scale production. Second, there are issues of cost and complexity: to adapt to highly corrosive media or achieve special electrolytic conditions (such as high-temperature molten salt electrolysis), expensive corrosion-resistant materials (such as special alloys and precious metal coated electrodes) are often required, or complex electrolytic cell structures and sealing systems are designed, significantly increasing equipment investment and operating costs. Finally, there are limitations to product quality: although the purity of vanadium obtained by electrolysis is improved compared to traditional methods, its impurity content—especially interstitial elements such as carbon and oxygen—may still be high, and particle uniformity is sometimes not ideal. The presence of these trace impurities can seriously affect the ductility, conductivity, and high-temperature performance of vanadium, thus limiting its application in precision fields.

[0005] Therefore, there is a need to provide a method for preparing metallic vanadium that can solve the problems of low purity, uneven particle size, and high carbon and oxygen content in metallic vanadium powder prepared by traditional electrolysis. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for preparing high-purity vanadium powder by molten salt electrolysis. This process is environmentally friendly and pollution-free, avoids the use of traditional strong acid / alkali electrolytes, reduces the harm to equipment and the environment, and does not require special electrolysis equipment, effectively reducing production costs. Moreover, it is simple to operate and easy to scale up production.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a method for preparing high-purity vanadium powder by molten salt electrolysis, the method comprising the following steps:

[0009] The dehydrated vanadium pentoxide was placed in molten salt to carry out a reduction reaction. After the reaction was completed, the vanadium metal was obtained by washing and solid-liquid separation.

[0010] The metallic vanadium is subjected to annealing, vacuum dehydrogenation, and grinding processes in sequence to obtain the high-purity vanadium powder.

[0011] The molten salt electrolysis method can completely avoid water interference, prevent the hydrolysis or oxidation of cathode products, and also prevent hydrogen evolution and the hydrogen embrittlement problem it causes.

[0012] This invention dehydrates the vanadium source under vacuum conditions, avoiding hydrolysis side reactions that lead to vanadium loss and product contamination. Dehydration also ensures the stability of the molten salt system and improves electrolysis efficiency. The dehydrated vanadium source is then reduced in a specialized molten salt system. This system possesses unique chemical and physical properties, enabling highly efficient reduction reactions at relatively low temperatures, thus reducing energy consumption and environmental pollution. Further separation and purification techniques can enhance the purity of the obtained metallic vanadium, achieving higher standards and improving product quality.

[0013] As a preferred embodiment of the present invention, the vacuum degree of the dehydration is (0.5-1.5)×10⁻⁶. -3 Pa, for example, could be 0.5 × 10⁻⁶. -3 Pa, 0.6×10 -3 Pa, 0.7×10 -3 Pa, 0.8×10 -3 Pa, 0.9×10 -3 Pa, 1.0 × 10 -3 Pa, 1.1×10 -3 Pa, 1.2×10 -3 Pa, 1.3×10-3 Pa, 1.4 × 10 -3 Pa or 1.5 × 10 -3 Pa, etc., but not limited to the listed values, other unlisted values ​​within the range also apply.

[0014] Preferably, the dehydration temperature is 750-850℃, for example, it can be 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃ or 850℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0015] Preferably, the dehydration time is 1.5-2.5 h, for example, it can be 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h or 2.5 h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] As a preferred embodiment of the present invention, the molten salt comprises sodium chloride and potassium chloride.

[0017] Preferably, the molar ratio of sodium chloride to potassium chloride is (0.5-1.5):1, for example, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] In the molten salt electrolysis of vanadium process, the molar ratio of sodium chloride to potassium chloride primarily affects the energy consumption, efficiency, and yield of the electrolysis process by altering the liquidus temperature, conductivity, and surface tension of the molten salt system. A ratio exceeding 1:1 will increase the melting point, requiring electrolysis to be completed at higher temperatures, leading to equipment corrosion and increased heat loss. Furthermore, it will hinder the aggregation of the electrolyzed vanadium droplets, disrupting the stable environment of vanadium ions and causing co-deposition of impurities, ultimately resulting in a lower purity of the electrolyzed product.

[0019] As a preferred technical solution of the present invention, the temperature of the reduction reaction is 650-750℃, for example, it can be 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃ or 750℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] As a preferred technical solution of the present invention, the reduction reaction time is 2-4 h, for example, it can be 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h or 4 h, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] By precisely controlling the temperature and time of the reaction during the reduction process, the vanadium source can be reduced to elemental vanadium in a short time. This method not only improves reaction efficiency and reduces production costs, but also yields vanadium with extremely high purity, a single phase, and uniform and regular particle size.

[0022] As a preferred embodiment of the present invention, the annealing process is carried out in a hydrogen atmosphere.

[0023] Hydrogen annealing can remove oxygen and nitrogen from vanadium powder, followed by vacuum annealing to remove hydrogen introduced during the process and avoid hydrogen embrittlement.

[0024] As a preferred technical solution of the present invention, the annealing temperature is 850-950℃, for example, it can be 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃ or 950℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0025] As a preferred technical solution of the present invention, the annealing time is 0.5-1.5 h, for example, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h or 1.5 h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] As a preferred embodiment of the present invention, the vacuum degree of the vacuum dehydrogenation is <10. -3 Pa.

[0027] As a preferred technical solution of the present invention, the temperature of the vacuum dehydrogenation is 800-900℃, for example, it can be 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃ or 900℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0028] Preferably, the vacuum dehydrogenation time is 5-7 h, for example, it can be 5 h, 5.2 h, 5.4 h, 5.6 h, 5.8 h, 6 h, 6.2 h, 6.4 h, 6.6 h, 6.8 h or 7 h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0030] (1) High efficiency and speed: The method for preparing metallic vanadium provided by the present invention dehydrates the vanadium source under vacuum conditions and reduces the vanadium source in a special molten salt system and at a temperature, which can obtain metallic vanadium in a short time and greatly improve the preparation efficiency.

[0031] (2) High purity: This invention can obtain vanadium metal powder with a purity of over 99.95%, and the phase is uniform and the particles are regular, which is something that existing technologies cannot achieve. This means that this invention can provide higher quality vanadium metal to meet a wider range of application needs;

[0032] (3) Environmentally friendly and pollution-free: The present invention uses a special molten salt system for electrolysis, which avoids the problem of traditional electrolysis methods requiring the use of strong acid or strong alkali as electrolyte, thereby reducing the corrosion of equipment and the pollution to the environment;

[0033] (4) Reduced costs: Compared with existing electrolytic methods for preparing metallic vanadium, this invention does not require the use of special electrolytic equipment, thereby reducing production costs;

[0034] (5) Simplified process: The preparation method of the present invention is simple and easy to implement, without the need for complicated operations and equipment, which is conducive to large-scale industrial production. Detailed Implementation

[0035] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0036] In one specific embodiment, the present invention provides a method for preparing high-purity vanadium powder by molten salt electrolysis, the method comprising the following steps:

[0037] Step 1: Place vanadium pentoxide into a vacuum dehydration furnace and set the vacuum level to (0.5-1.5)×10⁻⁶. -3 Pa, temperature 750-850℃, dehydration time 1.5-2.5 hours, to remove the moisture;

[0038] Step 2: The dehydrated vanadium pentoxide is placed in a special molten salt system, which is composed of sodium chloride and potassium chloride mixed in a molar ratio of (0.5-1.5):1. The reaction temperature is set at 650-750℃, and the reaction time is 2-4 hours. Under these conditions, vanadium pentoxide is reduced to metallic vanadium.

[0039] Step 3: After the reaction is complete, the reaction product is cooled to room temperature, and then vanadium metal is separated by washing and filtration.

[0040] Step 4: Anneal the separated vanadium metal in a hydrogen atmosphere at 850-950℃ for 0.5-1.5 hours to further improve the purity of the vanadium metal.

[0041] Step 5: Perform vacuum dehydrogenation on the annealed metallic vanadium, with a vacuum degree of <10. -3 Pa, temperature 800-900℃, time 5-7 hours;

[0042] Step 6: Grind and sieve the vacuum dehydrogenated vanadium metal to obtain vanadium metal powder with a particle size of 10-100 μm.

[0043] Through the above steps, vanadium metal powder with a purity of over 99.95% can be obtained, with a single phase and uniform and regular particles.

[0044] It should be clarified that any use of the process provided in the embodiments of the present invention or any substitution or change of conventional data falls within the protection and disclosure scope of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for preparing high-purity vanadium powder by molten salt electrolysis, the method comprising the following steps:

[0047] Step 1: Place vanadium pentoxide into a vacuum dehydration furnace and set the vacuum level to 1×10⁻⁶. -3 Pa, temperature 800℃, dehydration time 2 hours, to remove the water;

[0048] Step Two: The dehydrated vanadium pentoxide is placed in a special molten salt system, which is composed of sodium chloride and potassium chloride in a 1:1 molar ratio. The reaction temperature is set at 700℃, and the reaction time is 3 hours. Under these conditions, vanadium pentoxide is reduced to metallic vanadium.

[0049] Step 3: After the reaction is complete, the reaction product is cooled to room temperature, and then vanadium metal is separated by washing and filtration.

[0050] Step 4: The separated vanadium metal is annealed in a hydrogen atmosphere at 900°C for 1 hour to further improve the purity of the vanadium metal.

[0051] Step 5: Perform vacuum dehydrogenation on the annealed metallic vanadium, with a vacuum degree of <10. -3 Pa, temperature 850℃, time 6 hours;

[0052] Step 6: Grind and sieve the vacuum-dehydrogenated vanadium metal to obtain vanadium metal powder.

[0053] Example 2

[0054] This embodiment provides a method for preparing high-purity vanadium powder by molten salt electrolysis, the method comprising the following steps:

[0055] Step 1: Place vanadium pentoxide into a vacuum dehydration furnace and set the vacuum level to 0.5 × 10⁻⁶. -3 Pa, temperature 850℃, dehydration time 1.5 hours, to remove the water;

[0056] Step Two: The dehydrated vanadium pentoxide is placed in a special molten salt system, which is composed of sodium chloride and potassium chloride in a molar ratio of 0.5:1. The reaction temperature is set at 750℃, and the reaction time is 2 hours. Under these conditions, vanadium pentoxide is reduced to metallic vanadium.

[0057] Step 3: After the reaction is complete, the reaction product is cooled to room temperature, and then vanadium metal is separated by washing and filtration.

[0058] Step 4: The separated vanadium metal is annealed in a hydrogen atmosphere at 850°C for 1.5 hours to further improve the purity of the vanadium metal.

[0059] Step 5: Perform vacuum dehydrogenation on the annealed metallic vanadium, with a vacuum degree of <10. -3 Pa, temperature 800℃, time 7 hours;

[0060] Step 6: Grind and sieve the vacuum-dehydrogenated vanadium metal to obtain vanadium metal powder.

[0061] Example 3

[0062] This embodiment provides a method for preparing high-purity vanadium powder by molten salt electrolysis, the method comprising the following steps:

[0063] Step 1: Place vanadium pentoxide into a vacuum dehydration furnace and set the vacuum level to 1.5 × 10⁻⁶. -3 Pa, temperature 750℃, dehydration time 2.5 hours, to remove the water;

[0064] Step Two: The dehydrated vanadium pentoxide is placed in a special molten salt system, which is composed of sodium chloride and potassium chloride in a molar ratio of 1.5:1. The reaction temperature is set at 650℃, and the reaction time is 4 hours. Under these conditions, vanadium pentoxide is reduced to metallic vanadium.

[0065] Step 3: After the reaction is complete, the reaction product is cooled to room temperature, and then vanadium metal is separated by washing and filtration.

[0066] Step 4: The separated vanadium metal is annealed in a hydrogen atmosphere at 950°C for 0.5 hours to further improve the purity of the vanadium metal.

[0067] Step 5: Perform vacuum dehydrogenation on the annealed metallic vanadium, with a vacuum degree of <10. -3 Pa, temperature 900℃, time 5 hours;

[0068] Step 6: Grind and sieve the vacuum-dehydrogenated vanadium metal to obtain vanadium metal powder.

[0069] Example 4

[0070] This embodiment provides a method for preparing high-purity vanadium powder by molten salt electrolysis. The only difference between this method and Embodiment 1 is that the annealing treatment is carried out in an air atmosphere, while the rest is the same as Embodiment 1.

[0071] Example 5

[0072] This embodiment provides a method for preparing high-purity vanadium powder by molten salt electrolysis. The only difference between this method and Example 1 is that the temperature of the reduction reaction is changed to 630°C, while the rest is the same as in Example 1.

[0073] Example 6

[0074] This embodiment provides a method for preparing high-purity vanadium powder by molten salt electrolysis. The only difference between this method and Example 1 is that the temperature of the reduction reaction is changed to 770℃, while the rest is the same as Example 1.

[0075] Example 7

[0076] This embodiment provides a method for preparing high-purity vanadium powder by molten salt electrolysis. The only difference between this method and Example 1 is that the molar ratio of sodium chloride to potassium chloride is changed to 0.4:1, while the rest is the same as in Example 1.

[0077] Example 8

[0078] This embodiment provides a method for preparing high-purity vanadium powder by molten salt electrolysis. The only difference between this method and Example 1 is that the molar ratio of sodium chloride to potassium chloride is changed to 1.6:1, while the rest is the same as in Example 1.

[0079] Example 9

[0080] This embodiment provides a method for preparing high-purity vanadium powder by molten salt electrolysis. The only difference between this method and that of Embodiment 1 is that the molten salt is replaced with lithium chloride, and all other aspects are the same as those of Embodiment 1.

[0081] Comparative Example 1

[0082] This comparative example provides a method for preparing high-purity vanadium powder by molten salt electrolysis. The only difference between this method and Example 1 is that vanadium pentoxide is not dehydrated and is directly placed into the molten salt system. All other aspects are the same as in Example 1.

[0083] Comparative Example 2

[0084] This comparative example provides a method for preparing high-purity vanadium powder by molten salt electrolysis. The only difference between this method and Example 1 is that the metallic vanadium is not annealed but directly subjected to vacuum dehydrogenation treatment. All other aspects are the same as in Example 1.

[0085] Comparative Example 3

[0086] This comparative example provides a method for preparing high-purity vanadium powder by molten salt electrolysis. The only difference between this method and Example 1 is that the annealed vanadium metal is not subjected to vacuum dehydrogenation but is directly ground. All other aspects are the same as in Example 1.

[0087] Performance testing

[0088] The purity and particle uniformity of the vanadium powder provided in the examples and comparative examples were tested, and the results are shown in Table 1.

[0089]

[0090] As shown in Table 1, the technical solution provided by this invention can obtain vanadium powder with high purity (99.95%) and uniform particle size. Due to its moderate temperature, it avoids the energy consumption and corrosion caused by excessively high temperatures, and also prevents the instability of vanadium ions caused by excessively low temperatures. The reasonable molar ratio also promotes electrolysis efficiency and deposition. A comprehensive comparison of Examples 1 and Examples 4-9 shows that air annealing in Example 4 introduces a large amount of oxygen impurities, causing vanadium to be oxidized. The low reaction temperatures in Examples 5 and 6 significantly reduce the reaction rate, leading to incomplete reduction. Higher temperatures exacerbate the dissolution loss of vanadium in the molten salt, which is detrimental to yield and purity. In Examples 7 and 8, because the molten salt molar ratio deviates from the stable system, the melting point of the molten salt system increases significantly, and the conductivity deteriorates, leading to instability in the electrolysis process and incomplete reaction. Therefore, the purity and particle uniformity of the vanadium powder obtained are slightly worse than in Examples 2 and 3. In Example 9, the salt in the molten salt system is replaced with LiCl. Due to the change in the system, differences in solubility, decomposition voltage, etc., result in vanadium not being deposited.

[0091] A comprehensive comparison of Example 1 and Comparative Examples 1-3 reveals that in Comparative Example 1, the raw materials were not dehydrated, allowing moisture to carry impurities into the molten salt, severely polluting the electrolysis environment. In Comparative Example 2, the lack of annealing resulted in increased vanadium brittleness due to residual hydrogen, affecting the performance of the final product. In Comparative Example 3, the absence of vacuum dehydrogenation led to the formation of hydrides from residual hydrogen, reducing purity and severely impacting the mechanical properties of the resulting product.

[0092] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing high-purity vanadium powder by molten salt electrolysis, characterized in that, The method includes the following steps: The dehydrated vanadium pentoxide was placed in molten salt to carry out a reduction reaction. After the reaction was completed, the vanadium metal was obtained by washing and solid-liquid separation. The metallic vanadium is subjected to annealing, vacuum dehydrogenation, and grinding processes in sequence to obtain the high-purity vanadium powder.

2. The method according to claim 1, characterized in that, The vacuum degree of the dehydration is (0.5-1.5)×10 -3 Pa; Preferably, the dehydration temperature is 750-850℃; Preferably, the dehydration time is 1.5-2.5 h.

3. The method according to claim 1 or 2, characterized in that, The molten salt includes sodium chloride and potassium chloride; Preferably, the molar ratio of sodium chloride to potassium chloride is (0.5-1.5):

1.

4. The method according to any one of claims 1 to 3, characterized in that, The reduction reaction is carried out at a temperature of 650-750℃.

5. The method according to any one of claims 1 to 4, characterized in that, The reduction reaction takes 2-4 hours.

6. The method according to any one of claims 1 to 5, characterized in that, The annealing process is carried out in a hydrogen atmosphere.

7. The method according to any one of claims 1 to 6, characterized in that, The annealing temperature is 850-950℃.

8. The method according to any one of claims 1 to 7, characterized in that, The annealing process takes 0.5-1.5 hours.

9. The method according to any one of claims 1 to 8, characterized in that, The vacuum degree of the vacuum dehydrogenation is <10. -3 Pa.

10. The method according to any one of claims 1 to 9, characterized in that, The temperature for vacuum dehydrogenation is 800-900℃; Preferably, the vacuum dehydrogenation time is 5-7 hours.

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