Method for preparing molten salt containing vanadium dichloride

Abstract

The invention belongs to the technical field of vanadium metallurgy, and particularly relates to a method for preparing molten salt containing vanadium dichloride, which comprises the following steps: a) mixing NaCl and KCl according to a molar ratio of 1: (0.95-1.05), and heating and dehydrating under a vacuum condition to obtain mixed salt; b) putting vanadium into a graphite sleeve with holes in the wall surface, then putting the graphite sleeve into a reactor made of a non-metal material, and burying the vanadium by mixed salt; vacuumizing the reactor, and continuously introducing protective gas into the reactor; c) heating the reactor to 710-830 DEG C, and keeping the temperature for a period of time; then switching the introduced gas into hydrogen chloride, and carrying out heat preservation reaction for a first section; after the reaction is finished, cooling to obtain prefabricated molten salt; and d) the prefabricated molten salt is placed in an electrolytic bath for heat preservation electrolysis, cooling is conducted, and the molten salt containing vanadium dichloride is obtained. The method provided by the invention has a good application prospect in the field of preparing high-purity metal vanadium through molten salt electrolysis.

Description

Technical Field

[0001] This invention belongs to the field of vanadium metallurgy technology, and particularly relates to a method for preparing molten salt containing vanadium dichloride. Background Technology

[0002] High-purity metallic vanadium has the characteristics of high melting point, good processing performance, strong corrosion resistance and small fast neutron absorption cross section. It has applications in important fields such as aerospace bearing steel, vanadium alloys for nuclear engineering and vanadium-nickel alloy targets for integrated circuits. Each field has extremely high requirements for the purity of metallic vanadium.

[0003] Vanadium dichloride is an important molten salt electrolyte for the electrolytic production of high-purity vanadium metal, and its quality significantly affects the purity of the vanadium metal. Currently, commercially available vanadium dichloride products generally have a purity of around 85%, and importantly, these products are sold by the gram, which is insufficient to meet the quantity requirements for high-purity vanadium metal production via molten salt electrolysis. Therefore, developing a simple and scalable method for preparing molten salts containing vanadium dichloride is of great significance for the electrolytic production of high-purity vanadium metal. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing molten salt containing vanadium dichloride, which has the advantages of low impurity content in the product, simple preparation process, and applicability to large-scale production.

[0005] This invention provides a method for preparing molten salt containing vanadium dichloride, comprising the following steps:

[0006] a) Mix NaCl and KCl at a molar ratio of 1:(0.95~1.05), place them in a non-metallic container, and then heat them under vacuum to dehydrate them, thus obtaining a mixed salt.

[0007] b) Vanadium is placed inside a graphite sleeve with perforated walls, and a venting pipe is inserted inside the graphite sleeve; then the graphite sleeve is placed in a non-metallic reactor and submerged by the mixed salt; subsequently, the reactor is evacuated, and then a protective gas is continuously introduced into the reactor through the venting pipe.

[0008] c) After completing step b), heat the reactor to 710-830°C and keep it at that temperature for a period of time; then switch the gas introduced through the vent pipe to hydrogen chloride and keep it at that temperature for a period of time; after the reaction is completed, switch the gas introduced through the vent pipe back to the protective gas, cool it, and obtain the pre-made molten salt.

[0009] d) The pre-prepared molten salt is placed in an electrolytic cell, and the electrolytic cell is heated to 710-830°C under a protective gas atmosphere and kept at that temperature for a period of time; then the anode and cathode are inserted into the electrolytic cell for electrolysis under heat preservation; after electrolysis, the mixture is cooled to obtain molten salt containing vanadium dichloride.

[0010] Preferably, in step a), the content of impurity Fe in the NaCl is ≤0.01wt%, the content of impurity Cr is ≤0.01wt%, and the content of impurity Si is ≤0.01wt%; the content of impurity Fe in the KCl is ≤0.01wt%, the content of impurity Cr is ≤0.01wt%, and the content of impurity Si is ≤0.01wt%.

[0011] Preferably, in step a), the container is made of quartz, graphite, corundum, or magnesium oxide, with a material purity ≥ 99.9%.

[0012] Preferably, in step a), the heating and dehydration temperature is 250–350°C, and the time is 8–24 hours.

[0013] Preferably, in step b), the vanadium is vanadium particles with a particle size of 0.5 to 5 cm; the content of impurities Al in the vanadium is ≤0.01 wt%, the content of impurities Fe is ≤0.01 wt%, the content of impurities Cr is ≤0.01 wt%, and the content of impurities Si is ≤0.01 wt%.

[0014] Preferably, in step b), the inner wall diameter of the graphite sleeve is 3-10 cm, the diameter of the opening on the wall surface is 0.3-1 cm, and the wall surface opening rate is 10-40%.

[0015] Preferably, in step b), the material of the reactor is quartz, graphite, corundum, or magnesium oxide, and the material purity is ≥99.9%.

[0016] Preferably, in step c), the flow rate of hydrogen chloride is 0.05–5 L / min; and the time for the heat preservation reaction is 4–24 h.

[0017] Preferably, in step d), the anode is made of vanadium; the cathode is made of graphite, molybdenum, copper, or iron.

[0018] Preferably, in step d), the current density of the heat-insulating electrolysis is 0.01–0.1 A·cm⁻¹. -2 The time is 2 to 6 hours.

[0019] Compared with the prior art, the present invention provides a method for preparing molten salt containing vanadium dichloride, comprising the following steps: a) mixing NaCl and KCl at a molar ratio of 1:(0.95~1.05), placing the mixture in a non-metallic container, and then heating it under vacuum to dehydrate it, thereby obtaining a mixed salt; b) placing vanadium in a graphite sleeve with perforated walls, and inserting a venting pipe into the graphite sleeve; then placing the graphite sleeve in a non-metallic reactor and burying it in the mixed salt; subsequently evacuating the reactor, and then continuously introducing a protective gas into the reactor through the venting pipe; c) After completing step b), the reactor is heated to 710–830°C and held at that temperature for a period of time; then the gas introduced through the vent pipe is switched to hydrogen chloride, and the reaction is continued at that temperature for a period of time; after the reaction is completed, the gas introduced through the vent pipe is switched back to the protective gas, and the reactor is cooled to obtain a pre-prepared molten salt; d) The pre-prepared molten salt is placed in an electrolytic cell, and the electrolytic cell is heated to 710–830°C under a protective gas atmosphere and held at that temperature for a period of time; then the anode and cathode are inserted into the electrolytic cell, and electrolysis is performed at that temperature; after electrolysis is completed, the reactor is cooled to obtain a molten salt containing vanadium dichloride. The method provided by this invention has the advantages of low impurity content in the product, simple preparation process, and applicability to large-scale production, and has good application prospects in the field of molten salt electrolysis for the preparation of high-purity metallic vanadium. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a reactor with a graphite sleeve and mixed salt provided in an embodiment of the present invention.

[0022] Explanation of the attached diagram labels: 1 is the reactor, 2 is the vent pipe, 3 is the mixed salt, 4 is the graphite sleeve, and 5 is vanadium. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a method for preparing molten salt containing vanadium dichloride, comprising the following steps:

[0025] a) Mix NaCl and KCl at a molar ratio of 1:(0.95~1.05), place them in a non-metallic container, and then heat them under vacuum to dehydrate them, thus obtaining a mixed salt.

[0026] b) Vanadium is placed inside a perforated graphite sleeve, and a venting tube is inserted inside the graphite sleeve; then the graphite sleeve is placed in a non-metallic reactor and submerged by the mixed salt (e.g., Figure 1 (as shown); then the reactor is evacuated, and then protective gas is continuously introduced into the reactor through the vent pipe;

[0027] c) After completing step b), heat the reactor to 710-830°C and keep it at that temperature for a period of time; then switch the gas introduced through the vent pipe to hydrogen chloride and keep it at that temperature for a period of time; after the reaction is completed, switch the gas introduced through the vent pipe back to the protective gas, cool it, and obtain the pre-made molten salt.

[0028] d) The pre-prepared molten salt is placed in an electrolytic cell, and the electrolytic cell is heated to 710-830°C under a protective gas atmosphere and kept at that temperature for a period of time; then the anode and cathode are inserted into the electrolytic cell for electrolysis under heat preservation; after electrolysis, the mixture is cooled to obtain molten salt containing vanadium dichloride.

[0029] In the method provided by the present invention, in step a), the NaCl is preferably analytical grade NaCl, and the content of impurity Fe is preferably ≤0.01wt%, the content of impurity Cr is preferably ≤0.01wt%, and the content of impurity Si is preferably ≤0.01wt%.

[0030] In the method provided by the present invention, in step a), the KCl is preferably analytical grade KCl, and the content of impurity Fe is preferably ≤0.01wt%, the content of impurity Cr is preferably ≤0.01wt%, and the content of impurity Si is preferably ≤0.01wt%.

[0031] In the method provided by the present invention, in step a), the molar ratio of NaCl to KCl can specifically be 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04 or 1:1.05.

[0032] In the method provided by the present invention, in step a), the container is preferably a crucible; the material of the container is preferably quartz, graphite, corundum or magnesium oxide, and the purity of the material is preferably ≥99.9%.

[0033] In the method provided by the present invention, in step a), the temperature of heating and dehydration is preferably 250-350°C, specifically 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C or 350°C.

[0034] In the method provided by the present invention, in step a), the heating and dehydration time is preferably 8 to 24 hours, specifically 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours.

[0035] In the method provided by the present invention, in step b), the vanadium is preferably vanadium particles; the particle size of the vanadium particles is preferably 0.5 to 5 cm, specifically 0.5 cm, 1 cm, 1.5 cm, 2 cm, 2.5 cm, 3 cm, 3.5 cm, 4 cm, 4.5 cm or 5 cm.

[0036] In the method provided by the present invention, in step b), the content of impurity Al in the vanadium is preferably ≤0.01wt%, the content of impurity Fe is preferably ≤0.01wt%, the content of impurity Cr is preferably ≤0.01wt%, and the content of impurity Si is preferably ≤0.01wt%.

[0037] In the method provided by this invention, in step b), the inner wall diameter of the graphite sleeve is preferably 3-10 cm, specifically 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, or 10 cm; the aperture diameter of the wall opening of the graphite sleeve is preferably 0.3-1 cm, specifically 0.3 cm, 0.4 cm, 0.5 cm, 0.6 cm, 0.7 cm, 0.8 cm, 0.9 cm, or 1 cm; the wall opening ratio of the graphite sleeve is preferably 10-40%, specifically 10%, 15%, 20%, 25%, 30%, 35%, or 40%.

[0038] In the method provided by the present invention, in step b), the reactor is preferably a crucible; the material of the reactor is preferably quartz, graphite, corundum or magnesium oxide, and the purity of the material is preferably ≥99.9%.

[0039] In the method provided by the present invention, in step b), the protective gas is preferably argon.

[0040] In the method provided by the present invention, during step b), the pressure inside the reactor remains essentially constant at atmospheric pressure during the aeration process.

[0041] In the method provided by the present invention, in step c), the reactor can be specifically heated to 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C or 830°C.

[0042] In the method provided by the present invention, in step c), the heat preservation time before the gas introduced into the vent pipe is switched to hydrogen chloride is preferably 1 to 2 hours, specifically 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours.

[0043] In the method provided by the present invention, in step c), the flow rate of hydrogen chloride is preferably 0.05 to 5 L / min, specifically 0.05 L / min, 0.1 L / min, 0.2 L / min, 0.3 L / min, 0.4 L / min, 0.5 L / min, 0.7 L / min, 1 L / min, 1.5 L / min, 2 L / min, 2.5 L / min, 3 L / min, 3.5 L / min, 4 L / min, 4.5 L / min or 5 L / min.

[0044] In the method provided by the present invention, in step c), the temperature at which the heat preservation reaction is carried out after the gas introduced through the vent pipe is switched to hydrogen chloride is the same as the temperature at which the heat preservation is carried out before the gas introduced through the vent pipe is switched to hydrogen chloride.

[0045] In the method provided by the present invention, in step c), after the gas introduced through the vent pipe is switched to hydrogen chloride, the heat preservation reaction time is preferably 4 to 24 hours, specifically 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours.

[0046] In the method provided by the present invention, during step c), the pressure inside the reactor is kept essentially constant at atmospheric pressure during the aeration process.

[0047] In the method provided by the present invention, in step d), the protective gas is preferably argon.

[0048] In the method provided by the present invention, in step d), the electrolytic cell can be specifically heated to 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C or 830°C.

[0049] In the method provided by the present invention, in step d), the heat preservation time before inserting the anode and cathode into the electrolytic cell is preferably 1 to 2 hours, specifically 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours.

[0050] In the method provided by the present invention, in step d), the material of the anode is preferably vanadium; the material of the cathode is preferably graphite, molybdenum, copper or iron.

[0051] In the method provided by the present invention, in step d), the temperature at which the electrolysis is performed after inserting the anode and cathode is consistent with the temperature at which the electrolysis is performed before inserting the anode and cathode.

[0052] In the method provided by this invention, in step d), the current density of the heat-insulating electrolysis is preferably 0.01–0.1 A·cm⁻¹. -2 Specifically, it can be 0.01 A·cm. -2 0.02A·cm -2 0.03A·cm -2 0.04A·cm -2 0.05A·cm -2 0.06A·cm -2 0.07A·cm -2 0.08A·cm -2 0.09A·cm -2 Or 0.1A·cm -2 .

[0053] In the method provided by the present invention, in step d), the time for heat preservation electrolysis is preferably 2 to 6 hours, specifically 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0054] In the method provided by the present invention, in step d), the vanadium dichloride content of the molten salt containing vanadium dichloride is preferably 0.5 to 30 wt%, specifically 0.5 wt%, 0.82 wt%, 1 wt%, 5 wt%, 9.87 wt%, 10 wt%, 15 wt%, 18.16 wt%, 20 wt%, 25 wt%, or 30 wt%.

[0055] In the method provided by the present invention, in step d), the content of impurity Fe in the molten salt containing vanadium dichloride is preferably ≤0.01wt%, the content of impurity Cr is preferably ≤0.01wt%, and the content of impurity Si is preferably ≤0.01wt%.

[0056] The method provided by this invention has the advantages of low impurity content in the product, simple preparation process, and applicability to large-scale production, and has good application prospects in the field of preparing high-purity metallic vanadium by molten salt electrolysis.

[0057] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0058] In the following embodiments and comparative examples of the present invention, the Fe, Cr, and Si contents of the analytical grade NaCl and KCl used are all ≤0.01wt%; the quartz purity of the high-purity quartz crucible used is ≥99.9%; and the Al, Fe, Cr, and Si contents of the crude vanadium metal used are all ≤0.01wt%.

[0059] Example 1

[0060] 4 kg of analytical grade NaCl and KCl were mixed evenly at a molar ratio of 1:1 and placed in a high-purity quartz crucible. The mixture was then heated to 300°C under vacuum and held for 12 hours to obtain a dried mixed salt. Coarse metallic vanadium particles (1–3 cm in size) and a venting tube were placed in a perforated graphite sleeve with an inner diameter of 6 cm, a pore size of 0.6 cm, and a porosity of 40%. This sleeve was then placed inside the high-purity quartz crucible, with the dried mixed salt (such as...) placed around and above it. Figure 1 (As shown), after evacuation, argon gas is introduced into the vent pipe for protection. Argon gas is continuously introduced, and the tail gas is drained to maintain a pressure of approximately atmospheric pressure inside the crucible. The crucible is heated to 780℃ and held for 1 hour. Then, the argon gas in the vent pipe is switched to hydrogen chloride at a flow rate of 0.2 L / min, and the reaction is maintained for 8 hours. After the reaction, the hydrogen chloride gas in the vent pipe is switched back to argon gas, and the mixture is cooled to obtain a pre-prepared molten salt. The pre-prepared molten salt is placed in an electrolytic cell, evacuated, and purged with argon gas for protection. The electrolytic cell is heated to 780℃ and held for 1 hour. Then, a vanadium anode and a graphite cathode are inserted, and the current density is 0.05 A·cm⁻¹. -2 After electrolysis at a constant temperature for 4 hours, the mixture is cooled to obtain a molten salt suitable for the electrolysis of high-purity vanadium metal.

[0061] After the above operations, the mass content of VCl2 in the molten salt was 9.87%, and the mass contents of Fe, Cr, and Si were all <0.01%.

[0062] Example 2

[0063] 4 kg of analytical grade NaCl and KCl were mixed evenly at a molar ratio of 1:1.03 and placed in a high-purity quartz crucible. The mixture was then heated to 300°C under vacuum and held for 12 hours to obtain a dried mixed salt. Coarse metallic vanadium particles (1–3 cm in size) and a venting tube were placed in a perforated graphite sleeve with an inner diameter of 6 cm, a pore size of 0.6 cm, and a porosity of 40%. This sleeve was then placed inside the high-purity quartz crucible, with the dried mixed salt (e.g., [missing information]) placed around and above it. Figure 1 (As shown), after evacuation, argon gas is introduced into the vent pipe for protection. Argon gas is continuously introduced, and the tail gas is drained to maintain a pressure of approximately atmospheric pressure inside the crucible. The crucible is heated to 780℃ and held for 1 hour. Then, the argon gas in the vent pipe is switched to hydrogen chloride at a flow rate of 0.3 L / min, and the reaction is maintained for 12 hours. After the reaction, the hydrogen chloride gas in the vent pipe is switched back to argon gas, and the mixture is cooled to obtain a pre-prepared molten salt. The pre-prepared molten salt is placed in an electrolytic cell, evacuated, and purged with argon gas for protection. The electrolytic cell is heated to 780℃ and held for 1 hour. Then, a vanadium anode and a graphite cathode are inserted, and the current density is 0.05 A·cm⁻¹. -2 After electrolysis at a constant temperature for 4 hours, the mixture is cooled to obtain a molten salt suitable for the electrolysis of high-purity vanadium metal.

[0064] After the above operations, the mass content of VCl2 in the molten salt was 18.16%, and the mass contents of Fe, Cr, and Si were all <0.01%.

[0065] Example 3

[0066] 4 kg of analytical grade NaCl and KCl were mixed evenly at a molar ratio of 1:0.98 and placed in a high-purity quartz crucible. The mixture was then heated to 300°C under vacuum and held for 12 hours to obtain a dried mixed salt. Coarse metallic vanadium particles (1–3 cm in size) and a venting tube were placed in a perforated graphite sleeve with an inner diameter of 6 cm, a pore size of 0.6 cm, and a porosity of 40%. This sleeve was then placed inside the high-purity quartz crucible, with the dried mixed salt (e.g., [missing information]) placed around and above it. Figure 1 (As shown), after evacuation, argon gas is introduced into the vent pipe for protection. Argon gas is continuously introduced, and the tail gas is drained to maintain a pressure of approximately atmospheric pressure inside the crucible. The crucible is heated to 780℃ and held for 1 hour. Then, the argon gas in the vent pipe is switched to hydrogen chloride at a flow rate of 0.05 L / min, and the reaction is maintained for 4 hours. After the reaction, the hydrogen chloride gas in the vent pipe is switched back to argon gas, and the mixture is cooled to obtain a pre-prepared molten salt. The pre-prepared molten salt is placed in an electrolytic cell, evacuated, and purged with argon gas for protection. The electrolytic cell is heated to 780℃ and held for 1 hour. Then, a vanadium anode and a graphite cathode are inserted, and the current density is 0.05 A·cm⁻¹. -2 After electrolysis at a constant temperature for 4 hours, the mixture is cooled to obtain a molten salt suitable for the electrolysis of high-purity vanadium metal.

[0067] After the above operations, the mass content of VCl2 in the molten salt is 0.82%, and the mass contents of Fe, Cr, and Si are all <0.01%.

[0068] Comparative Example 1

[0069] 4 kg of analytical grade NaCl and KCl were mixed evenly at a molar ratio of 1:1 and placed in a stainless steel crucible. The mixture was then heated to 300°C under vacuum and held for 12 hours to obtain a dried mixed salt. Coarse metallic vanadium particles (1–3 cm in size) and a venting tube were placed in a perforated graphite sleeve with an inner diameter of 6 cm, a pore size of 0.6 cm, and a porosity of 40%. This sleeve was then placed inside a stainless steel crucible, with the dried mixed salt (e.g., [missing information]) placed around and above it. Figure 1 (As shown), after evacuation, argon gas is introduced into the vent pipe for protection. Argon gas is continuously introduced, and the tail gas is drained to maintain a pressure of approximately atmospheric pressure inside the crucible. The crucible is heated to 780℃ and held for 1 hour. Then, the argon gas in the vent pipe is switched to hydrogen chloride at a flow rate of 0.2 L / min, and the reaction is maintained for 8 hours. After the reaction, the hydrogen chloride gas in the vent pipe is switched back to argon gas, and the mixture is cooled to obtain a pre-prepared molten salt. The pre-prepared molten salt is placed in an electrolytic cell, evacuated, and purged with argon gas for protection. The electrolytic cell is heated to 780℃ and held for 1 hour. Then, a vanadium anode and a graphite cathode are inserted, and the current density is 0.05 A·cm⁻¹. -2 Electrolysis was carried out at a constant temperature for 4 hours. After electrolysis, the mixture was cooled to obtain a molten salt containing VCl2.

[0070] After the above operations, the mass content of VCl2 in the molten salt is 8.76%, the mass content of Fe is 3.41%, the mass content of Cr is 2.69%, and the mass content of Si is <0.01%.

[0071] Comparative Example 2

[0072] 4 kg of analytical grade NaCl and KCl were mixed evenly at a molar ratio of 1:0.1 and placed in a high-purity quartz crucible. The mixture was then heated to 300°C under vacuum and held for 12 hours to obtain a dried mixed salt. Coarse metallic vanadium particles (1–3 cm in size) and a venting tube were placed in a perforated graphite sleeve with an inner diameter of 6 cm, a pore size of 0.6 cm, and a porosity of 40%. This sleeve was then placed inside the high-purity quartz crucible, with the dried mixed salt (e.g., [missing information]) placed around and above it. Figure 1(As shown), after evacuation, argon gas is introduced into the vent pipe for protection. Argon gas is continuously introduced, and the tail gas is drained to maintain a pressure of approximately atmospheric pressure inside the crucible. The crucible is heated to 780℃ and held for 1 hour. Then, the argon gas in the vent pipe is switched to hydrogen chloride at a flow rate of 0.2 L / min, and the reaction is maintained for 8 hours. After the reaction, the hydrogen chloride gas in the vent pipe is switched back to argon gas, and the mixture is cooled to obtain a pre-prepared molten salt. The pre-prepared molten salt is placed in an electrolytic cell, evacuated, and purged with argon gas for protection. The electrolytic cell is heated to 780℃ and held for 1 hour. Then, a vanadium anode and a graphite cathode are inserted, and the current density is 0.05 A·cm⁻¹. -2 Electrolysis was carried out at a constant temperature for 4 hours. After electrolysis, the mixture was cooled to obtain molten salt.

[0073] After the above operations, the molten salt does not contain VCl2. This is mainly because the NaCl-KCl mixed salt was not completely melted, and the VCl2 generated in the reaction did not come into sufficient contact with the mixed salt. A large amount of VCl2 was oxidized to VCl3 and VCl4.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a molten salt containing vanadium dichloride, characterized in that, Includes the following steps: a) Mix NaCl and KCl at a molar ratio of 1:(0.95~1.05), place them in a non-metallic container, and then heat them under vacuum to dehydrate them, thus obtaining a mixed salt. b) Vanadium is placed inside a graphite sleeve with perforated walls, and a venting pipe is inserted inside the graphite sleeve; then the graphite sleeve is placed in a non-metallic reactor and submerged by the mixed salt; subsequently, the reactor is evacuated, and then a protective gas is continuously introduced into the reactor through the venting pipe. c) After completing step b), heat the reactor to 710–830°C and keep it at that temperature for a period of time; Then the gas introduced through the vent pipe is switched to hydrogen chloride, and the reaction is kept at a certain temperature for a period of time. After the reaction is completed, the gas introduced through the vent pipe is switched back to the protective gas, and the mixture is cooled to obtain the pre-made molten salt. d) Place the pre-prepared molten salt in an electrolytic cell, heat the electrolytic cell to 710-830°C under a protective gas atmosphere, and keep it at that temperature for a period of time; then insert the anode and cathode into the electrolytic cell and perform electrolysis while keeping it at that temperature. After electrolysis, the solution is cooled to obtain a molten salt containing vanadium dichloride.

2. The method according to claim 1, characterized in that, In step a), the content of impurity Fe in NaCl is ≤0.01wt%, the content of impurity Cr is ≤0.01wt%, and the content of impurity Si is ≤0.01wt%; the content of impurity Fe in KCl is ≤0.01wt%, the content of impurity Cr is ≤0.01wt%, and the content of impurity Si is ≤0.01wt%.

3. The method according to claim 1, characterized in that, In step a), the container is made of quartz, graphite, corundum, or magnesium oxide, with a purity of ≥99.9%.

4. The method according to claim 1, characterized in that, In step a), the heating and dehydration temperature is 250–350°C, and the time is 8–24 hours.

5. The method according to claim 1, characterized in that, In step b), the vanadium is vanadium particles with a particle size of 0.5 to 5 cm; the content of impurities Al in the vanadium is ≤0.01 wt%, the content of impurities Fe is ≤0.01 wt%, the content of impurities Cr is ≤0.01 wt%, and the content of impurities Si is ≤0.01 wt%.

6. The method according to claim 1, characterized in that, In step b), the inner wall diameter of the graphite sleeve is 3-10 cm, the diameter of the opening on the wall surface is 0.3-1 cm, and the wall surface opening rate is 10-40%.

7. The method according to claim 1, characterized in that, In step b), the reactor material is quartz, graphite, corundum, or magnesium oxide, with a material purity ≥ 99.9%.

8. The method according to claim 1, characterized in that, In step c), the flow rate of hydrogen chloride is 0.05–5 L / min; the time for the heat preservation reaction is 4–24 h.

9. The method according to claim 1, characterized in that, In step d), the anode is made of vanadium; the cathode is made of graphite, molybdenum, copper, or iron.

10. The method according to claim 1, characterized in that, In step d), the current density of the heat-insulating electrolysis is 0.01–0.1 A·cm. -2 The time is 2 to 6 hours.

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