Defluorination preparation method of niobium pentoxide

Abstract

The invention provides a defluorination preparation method of niobium pentoxide, which comprises the following steps: (1) mixing a niobium hydroxide raw material with deionized water, and stirring until the niobium hydroxide raw material and the deionized water are uniformly mixed to obtain a slurry material; (2) uniformly smearing the slurry-like material on the inner surface of a hollow cylindrical crucible, and putting the hollow cylindrical crucible into the middle section of a glass tube of a microwave tube furnace; (3) inserting a thermocouple from one side of the glass tube, enabling the end part of the thermocouple to be in contact with the slurry-like material in the hollow cylindrical crucible, placing a water vapor generating device on the other side of the glass tube, and enabling a water vapor tube of the water vapor generating device to extend into the glass tube; and (4) starting the water vapor generating device and the microwave tube furnace, raising the temperature of the slurry-like material in the hollow cylindrical crucible to a target temperature, preserving heat for 20-40 minutes, naturally cooling to room temperature, and taking out to obtain niobium pentoxide. According to the method, residual fluorine can be efficiently removed while the purity of niobium pentoxide is guaranteed, the water consumption for washing is reduced, and the process period is shortened.

Description

Technical Field

[0001] This invention relates to a method for preparing niobium pentoxide, and more particularly to a method for preparing niobium pentoxide by defluorination. Background Technology

[0002] Niobium (Nb) is an important rare metal resource with unique physicochemical properties such as high-temperature resistance, corrosion resistance, high melting point, low thermal neutron capture cross-section, and good electrical and thermal conductivity. It is widely used in many high-tech fields, particularly in the steel and aerospace industries, as well as in the research and application of superconducting materials. Among niobium and its compounds, niobium pentoxide (Nb₂O₅) is a strategically important functional oxide material, serving as a key precursor for the preparation of various high-end niobium-based materials and compounds. Due to its excellent chemical stability, dielectric properties, optical refractive index, and electrochemical activity, Nb₂O₅ is widely used in optoelectronic devices, lithium-ion batteries, electronic ceramics, capacitor dielectrics, gas-sensitive elements, and catalytic materials. With the rapid development of high-end electronic devices, optical communication, and new energy technologies, the demand for high-purity, structurally controllable Nb₂O₅ continues to grow, placing higher demands on its preparation and purification processes.

[0003] Currently, the main industrial processes for preparing niobium pentoxide (Nb₂O₅) include hydrometallurgy, pyrometallurgy, and chlorination-hydrolysis. Among these, hydrometallurgy has become the mainstream technology for Nb₂O₅ industrial production due to its advantages such as low equipment requirements, high metal recovery rate, and controllable product particle size. This process includes key steps such as leaching, extraction and back-extraction, precipitation, washing, and calcination. First, in the leaching stage, niobium-containing raw materials (such as columbite tantalite, spent Nb oxide catalysts, etc.) are leached with a mixed acid of HF-H₂SO₄. Hydrofluoric acid is used as the main complexing agent to form a highly stable fluorine complex [NbF₆] with niobium. - ,[NbOF5] 2-Sulfuric acid plays a role in adjusting acidity and ionic strength, and promoting the separation of niobium and tantalum. Secondly, in the extraction and back-extraction stages, since Nb and Ta have similar chemical properties in their fluorine complex forms, organic extractants (such as MIBK, TBP, or Alamine 336) are used to achieve liquid-liquid separation of Nb and Ta, and then back-extraction returns the niobium to the aqueous phase. Subsequently, in the precipitation stage, ammonia or ammonium carbonate is added to the back-extraction solution to adjust the pH to 5-8, causing the fluorine complex to decompose and generate niobium hydroxide (Nb(OH)5) precipitate. This stage is one of the main sources of fluorine residue. During this process, some fluoride ions are embedded in the Nb(OH)5 structure as Nb-F bonds, or are physically adsorbed and embedded in the gel pores as NH4F, making subsequent washing difficult to completely remove them. Finally, in the washing and calcination stages, the precipitate is washed multiple times to remove soluble fluorides, and then calcined at 400-800℃ to dehydrate and transform into Nb2O5.

[0004] In the preparation of niobium pentoxide (Nb₂O₅) using the HF-H₂SO₄ wet process, the residual fluorine in the final product mainly originates from the niobium hydroxide precursor and its thermal conversion process. Fluorine can exist in Nb₂O₅ in several forms:

[0005] First, some of the F originates from soluble Nb-F complexes (such as [NbF6]) in the original leachate. - ,[NbOF5] 2- (e.g., fluorine) is not completely removed during the hydrolysis and precipitation stage and enters the solid phase along with the niobium hydroxide precipitate; secondly, during precipitation and washing, some fluorine is bound to the particle surface in the form of surface adsorption or chemical bonding with hydroxyl groups, and its content is affected by pH value, ionic strength and washing conditions; thirdly, during drying or calcination, fluorine may be embedded in the crystal lattice to form stable oxyfluoride or metastable NbOxFy phase, which exists as an endogenous impurity that is difficult to remove; finally, some fluorine is adsorbed or embedded in the pores in the form of ammonium salts (such as NH4F or NH4HF2), and may still remain after calcination and react with Nb to form impurity phases such as NbF3, NbF5 or (NH4)2NbF7.

[0006] In actual production, to reduce the residual fluoride content in niobium hydroxide generated during the precipitation stage, the product typically requires extensive water washing. Taking niobium hydroxide from the precipitation stage (with an F content of approximately 150,000 ppm) as an example, to reduce the fluoride content to approximately 3,600 ppm, it is usually necessary to wash each kilogram of niobium hydroxide precipitate with approximately 50 L of dilute ammonia solution prepared with deionized water. This process requires repeated washing multiple times to effectively remove adsorbed and soluble fluorides, leading to high water consumption, long process cycles, and high fluoride concentrations in the wastewater. Furthermore, residual fluoride can still react with niobium to form impurity phases such as NbF3, NbF5, or (NH4)2NbF7, which not only reduces the purity of Nb2O5 but also affects its dielectric properties and thermal stability in optoelectronic, ceramic, and capacitor materials. In addition, fluorination byproducts are highly corrosive to equipment, significantly increasing the burden of wastewater treatment and environmental management. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for defluorinating niobium pentoxide, which can efficiently remove residual fluorine while ensuring the purity of niobium pentoxide, reduce the amount of washing water and shorten the process cycle.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0009] A method for preparing niobium pentoxide by defluorination includes the following steps:

[0010] (1) Mix niobium hydroxide raw material with deionized water and stir until the mixture is uniform to obtain a slurry-like material;

[0011] (2) The mud-like material obtained in step (1) is evenly coated on the inner surface of the hollow cylindrical crucible, and then the hollow cylindrical crucible is placed in the middle section of the glass tube of the microwave tube furnace.

[0012] (3) Insert the thermocouple into one side of the glass tube after step (2) and make the end of the thermocouple contact the slurry material in the hollow cylindrical crucible. Place the water vapor generator on the other side of the glass tube and make the water vapor tube of the water vapor generator extend into the glass tube.

[0013] (4) Turn on the steam generator and microwave tube furnace to raise the temperature of the slurry material in the hollow cylindrical crucible to the target temperature and keep it at that temperature for 20-40 minutes. After naturally cooling to room temperature, take it out to obtain niobium pentoxide.

[0014] Furthermore, in step (1) of the present invention, the niobium hydroxide raw material is niobium hydroxide obtained by wet sulfuric acid-hydrofluoric acid mixed acid leaching process HF-H2SO4 method, wet hydrochloric acid-hydrofluoric acid mixed acid leaching process HCl-HF method, or fluorine-containing salt melt-leaching process NaF / KF system.

[0015] Furthermore, in step (1) of the present invention, the mass ratio of niobium hydroxide raw material to deionized water is (1-5):1, and the stirring speed is 200-400 rpm.

[0016] Furthermore, in step (2) of the present invention, the hollow cylindrical crucible has an inner diameter of 50 mm, an outer diameter of 54 mm, a length of 150 mm, and a thickness of 5 mm.

[0017] Furthermore, in step (2) of the present invention, the inner diameter of the glass tube is 56mm, the outer diameter is 60mm, the length is 1500mm, and the thickness is 2mm.

[0018] Furthermore, in step (3) of the present invention, the thermocouple is a type K thermocouple; the water vapor tube extends 10 mm into the glass tube.

[0019] Furthermore, in step (4) of the present invention, the water vapor flow rate of the water vapor generator is 0.05-0.2 L / h, and the water vapor temperature is room temperature.

[0020] Furthermore, in step (4) of the present invention, the microwave frequency of the microwave tube furnace is 2.45 GHz and the microwave power is 2000 W.

[0021] Furthermore, in step (4) of the present invention, the target temperature is 500-800℃.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention starts with the principle of microwave heating, using microwave heating of water vapor with high dielectric constant and fluorine-containing impurities (ammonium fluoride, ammonium hydrogen fluoride, fluorine niobium compounds, etc.) to rapidly raise the temperature of the material and allow the fluorine-containing impurities to be discharged through the flow of water vapor. Compared with the traditional dilute ammonia washing process, this process has advantages such as reducing water consumption, shortening process time, and being environmentally friendly (no wastewater treatment required). It can efficiently remove residual fluorine while ensuring the purity of niobium pentoxide. Detailed Implementation

[0024] The present invention will now be described in detail with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0025] Example 1

[0026] The method for preparing niobium pentoxide by defluorination includes the following steps:

[0027] (1) Niobium hydroxide raw material was mixed with deionized water at a mass ratio of 3:1 and stirred at 300 rpm until the mixture was uniform to obtain a slurry. The niobium hydroxide raw material was niobium hydroxide obtained by wet sulfuric acid-hydrofluoric acid mixed acid leaching process HF-H2SO4 method, and its F concentration was 2271.390 ppm (IC-F test).

[0028] (2) Apply 20g of the slurry material obtained in step (1) evenly to the inner surface of the hollow cylindrical crucible, and then place the hollow cylindrical crucible into the middle section of the glass tube of the microwave tube furnace; the inner diameter of the hollow cylindrical crucible is 50mm, the outer diameter is 54mm, the length is 150mm, and the thickness is 5mm; the inner diameter of the glass tube is 56mm, the outer diameter is 60mm, the length is 1500mm, and the thickness is 2mm.

[0029] (3) Insert the K-type thermocouple into one side of the glass tube after step (2) and make the end of the K-type thermocouple contact the slurry material in the hollow cylindrical crucible. Place the water vapor generator on the other side of the glass tube and make the water vapor tube of the water vapor generator extend into the glass tube by 10 mm.

[0030] (4) Turn on the water vapor generator and microwave tube furnace, raise the temperature of the slurry material in the hollow cylindrical crucible to 500°C and keep it at that temperature for 30 minutes. After naturally cooling to room temperature, take out the sample. XRD test confirmed that it was niobium pentoxide. Then, the F concentration was tested using a PXSJ-270F instrument. The F content was 37.723 ppm. The water vapor flow rate of the water vapor generator was 0.16 L / h and the water vapor temperature was room temperature. The microwave frequency of the microwave tube furnace was 2.45 GHz and the microwave power was 2000 W.

[0031] Example 2

[0032] The defluorination preparation method of niobium pentoxide includes the following steps:

[0033] (1) Niobium hydroxide raw material was mixed with deionized water at a mass ratio of 3:1 and stirred at 300 rpm until the mixture was uniform to obtain a slurry. The niobium hydroxide raw material was niobium hydroxide obtained by the wet hydrochloric acid-hydrofluoric acid mixed acid leaching process HCl-HF method, and its F concentration was 23,000 ppm (IC-F test).

[0034] (2) Apply 20g of the slurry material obtained in step (1) evenly to the inner surface of the hollow cylindrical crucible, and then place the hollow cylindrical crucible into the middle section of the glass tube of the microwave tube furnace; the inner diameter of the hollow cylindrical crucible is 50mm, the outer diameter is 54mm, the length is 150mm, and the thickness is 5mm; the inner diameter of the glass tube is 56mm, the outer diameter is 60mm, the length is 1500mm, and the thickness is 2mm.

[0035] (3) Insert the K-type thermocouple into one side of the glass tube after step (2) and make the end of the K-type thermocouple contact the slurry material in the hollow cylindrical crucible. Place the water vapor generator on the other side of the glass tube and make the water vapor tube of the water vapor generator extend into the glass tube by 10 mm.

[0036] (4) Turn on the water vapor generator and microwave tube furnace, raise the temperature of the slurry material in the hollow cylindrical crucible to 500°C and keep it at that temperature for 30 minutes. After naturally cooling to room temperature, take out the sample. XRD test confirmed that it was niobium pentoxide. Then, the F concentration was tested using a PXSJ-270F instrument. The F content was 42.154 ppm. The water vapor flow rate of the water vapor generator was 0.1 L / h and the water vapor temperature was room temperature. The microwave frequency of the microwave tube furnace was 2.45 GHz and the microwave power was 2000 W.

[0037] Example 3

[0038] The defluorination preparation method of niobium pentoxide includes the following steps:

[0039] (1) Niobium hydroxide raw material was mixed with deionized water at a mass ratio of 3:1 and stirred at 400 rpm until the mixture was uniform to obtain a slurry. The niobium hydroxide raw material was niobium hydroxide obtained by the NaF / KF system of fluorine salt melt-leaching process, and its F concentration was 30,000 ppm (IC-F test).

[0040] (2) Apply 20g of the slurry material obtained in step (1) evenly to the inner surface of the hollow cylindrical crucible, and then place the hollow cylindrical crucible into the middle section of the glass tube of the microwave tube furnace; the inner diameter of the hollow cylindrical crucible is 50mm, the outer diameter is 54mm, the length is 150mm, and the thickness is 5mm; the inner diameter of the glass tube is 56mm, the outer diameter is 60mm, the length is 1500mm, and the thickness is 2mm.

[0041] (3) Insert the K-type thermocouple into one side of the glass tube after step (2) and make the end of the K-type thermocouple contact the slurry material in the hollow cylindrical crucible. Place the water vapor generator on the other side of the glass tube and make the water vapor tube of the water vapor generator extend into the glass tube by 10 mm.

[0042] (4) Turn on the water vapor generator and microwave tube furnace, raise the temperature of the slurry material in the hollow cylindrical crucible to 500°C and keep it at that temperature for 20 minutes. After naturally cooling to room temperature, take out the sample. XRD test confirmed that it was niobium pentoxide. Then, the F concentration was tested using a PXSJ-270F instrument. The F content was 45.473 ppm. The water vapor flow rate of the water vapor generator was 0.05 L / h and the water vapor temperature was room temperature. The microwave frequency of the microwave tube furnace was 2.45 GHz and the microwave power was 2000 W.

[0043] Example 4

[0044] The method for preparing niobium pentoxide by defluorination includes the following steps:

[0045] (1) Niobium hydroxide raw material was mixed with deionized water at a mass ratio of 1:1 and stirred at 200 rpm until the mixture was uniform to obtain a slurry. The niobium hydroxide raw material was niobium hydroxide obtained by wet sulfuric acid-hydrofluoric acid mixed acid leaching process HF-H2SO4 method, and its F concentration was 2271.390ppm (IC-F test).

[0046] (2) Apply 20g of the slurry material obtained in step (1) evenly to the inner surface of the hollow cylindrical crucible, and then place the hollow cylindrical crucible into the middle section of the glass tube of the microwave tube furnace; the inner diameter of the hollow cylindrical crucible is 50mm, the outer diameter is 54mm, the length is 150mm, and the thickness is 5mm; the inner diameter of the glass tube is 56mm, the outer diameter is 60mm, the length is 1500mm, and the thickness is 2mm.

[0047] (3) Insert the K-type thermocouple into one side of the glass tube after step (2) and make the end of the K-type thermocouple contact the slurry material in the hollow cylindrical crucible. Place the water vapor generator on the other side of the glass tube and make the water vapor tube of the water vapor generator extend into the glass tube by 10 mm.

[0048] (4) Turn on the water vapor generator and microwave tube furnace, raise the temperature of the slurry material in the hollow cylindrical crucible to 600°C and keep it at that temperature for 40 minutes. After naturally cooling to room temperature, take out the sample. XRD test confirmed that it was niobium pentoxide. Then, the F concentration was tested using a PXSJ-270F instrument. The F content was 37.745 ppm. The water vapor flow rate of the water vapor generator was 0.2 L / h and the water vapor temperature was room temperature. The microwave frequency of the microwave tube furnace was 2.45 GHz and the microwave power was 2000 W.

[0049] Example 5

[0050] The method for preparing niobium pentoxide by defluorination includes the following steps:

[0051] (1) Niobium hydroxide raw material was mixed with deionized water at a mass ratio of 5:1 and stirred at 200 rpm until the mixture was uniform to obtain a slurry. The niobium hydroxide raw material was niobium hydroxide obtained by wet sulfuric acid-hydrofluoric acid mixed acid leaching process HF-H2SO4 method, and its F concentration was 2271.390ppm (IC-F test).

[0052] (2) Apply 20g of the slurry material obtained in step (1) evenly to the inner surface of the hollow cylindrical crucible, and then place the hollow cylindrical crucible into the middle section of the glass tube of the microwave tube furnace; the inner diameter of the hollow cylindrical crucible is 50mm, the outer diameter is 54mm, the length is 150mm, and the thickness is 5mm; the inner diameter of the glass tube is 56mm, the outer diameter is 60mm, the length is 1500mm, and the thickness is 2mm.

[0053] (3) Insert the K-type thermocouple into one side of the glass tube after step (2) and make the end of the K-type thermocouple contact the slurry material in the hollow cylindrical crucible. Place the water vapor generator on the other side of the glass tube and make the water vapor tube of the water vapor generator extend into the glass tube by 10 mm.

[0054] (4) Turn on the water vapor generator and microwave tube furnace, raise the temperature of the slurry material in the hollow cylindrical crucible to 700°C and keep it at that temperature for 40 minutes. After naturally cooling to room temperature, take out the sample. XRD test confirmed that it was niobium pentoxide. Then, the F concentration was tested using a PXSJ-270F instrument. The F content was 36.056 ppm. The water vapor flow rate of the water vapor generator was 0.15 L / h and the water vapor temperature was room temperature. The microwave frequency of the microwave tube furnace was 2.45 GHz and the microwave power was 2000 W.

[0055] Example 6

[0056] The method for preparing niobium pentoxide by defluorination includes the following steps:

[0057] (1) Niobium hydroxide raw material was mixed with deionized water at a mass ratio of 2:1 and stirred at 400 rpm until the mixture was uniform to obtain a slurry. The niobium hydroxide raw material was niobium hydroxide obtained by wet sulfuric acid-hydrofluoric acid mixed acid leaching process HF-H2SO4 method, and its F concentration was 2271.390 ppm (IC-F test).

[0058] (2) Apply 20g of the slurry material obtained in step (1) evenly to the inner surface of the hollow cylindrical crucible, and then place the hollow cylindrical crucible into the middle section of the glass tube of the microwave tube furnace; the inner diameter of the hollow cylindrical crucible is 50mm, the outer diameter is 54mm, the length is 150mm, and the thickness is 5mm; the inner diameter of the glass tube is 56mm, the outer diameter is 60mm, the length is 1500mm, and the thickness is 2mm.

[0059] (3) Insert the K-type thermocouple into one side of the glass tube after step (2) and make the end of the K-type thermocouple contact the slurry material in the hollow cylindrical crucible. Place the water vapor generator on the other side of the glass tube and make the water vapor tube of the water vapor generator extend into the glass tube by 10 mm.

[0060] (4) Turn on the water vapor generator and microwave tube furnace, raise the temperature of the slurry material in the hollow cylindrical crucible to 800℃ and keep it at that temperature for 20 minutes. After naturally cooling to room temperature, take out the sample. XRD test confirmed that it was niobium pentoxide. Then, the F concentration was tested using a PXSJ-270F instrument. The F content was 37.617ppm. The water vapor flow rate of the water vapor generator was 0.16L / h and the water vapor temperature was room temperature. The microwave frequency of the microwave tube furnace was 2.45GHz and the microwave power was 2000W.

[0061] Comparative Example 1

[0062] The preparation method of niobium pentoxide includes the following steps:

[0063] The niobium hydroxide raw material used was obtained by wet sulfuric acid-hydrofluoric acid mixed acid leaching process (HF-H2SO4 method), with an F concentration of 2271.390 ppm (IC-F test). No treatment was performed on the niobium hydroxide raw material. 20 g of the raw material was placed in a conventional boat-shaped crucible, which was then placed in a conventional box furnace and heated to 1000℃ at a rate of 10℃ / min and held for 2 hours. After naturally cooling to room temperature, the sample was removed, and XRD analysis confirmed it to be niobium pentoxide. Subsequently, the F concentration was tested using a PXSJ-270F instrument, and the F content was 658.907 ppm.

[0064] Comparative Example 2

[0065] The preparation method of niobium pentoxide includes the following steps:

[0066] The niobium hydroxide raw material used was obtained by wet sulfuric acid-hydrofluoric acid mixed acid leaching process (HF-H2SO4 method), with an F concentration of 2271.390 ppm (IC-F test). No treatment was performed on the niobium hydroxide raw material. 20 g of the raw material was placed in a standard boat-shaped crucible, which was then placed in the middle section of a glass tube in a microwave tube furnace. The glass tube had an inner diameter of 56 mm, an outer diameter of 60 mm, a length of 1500 mm, and a thickness of 2 mm. A K-type thermocouple was then inserted from one side of the glass tube, with its end contacting the raw material in the crucible. The temperature was raised to 500 °C at 2000 W and held for 30 minutes. After naturally cooling to room temperature, the sample was removed. XRD analysis confirmed it to be niobium pentoxide. The F concentration was then tested using a PXSJ-270F instrument, and the F content was 546.786 ppm.

[0067] The comparison of Example 1, Comparative Example 1, and Comparative Example 2 shows that the sample prepared in Example 1 of the present invention has the lowest F content. Comparative Example 1 used conventional heating without introducing water vapor, while Comparative Example 2 used microwave heating without introducing water vapor. The F content of the samples prepared in both examples was significantly higher than that in Example 1 of the present invention, indicating that the preparation method of microwave heating and water vapor introduction used in the present invention can efficiently remove residual fluorine.

[0068] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing niobium pentoxide by defluorination, characterized in that: Includes the following steps: (1) Mix niobium hydroxide raw material with deionized water and stir until the mixture is uniform to obtain a slurry-like material; (2) The mud-like material obtained in step (1) is evenly coated on the inner surface of the hollow cylindrical crucible, and then the hollow cylindrical crucible is placed in the middle section of the glass tube of the microwave tube furnace. (3) Insert the thermocouple into one side of the glass tube after step (2) and make the end of the thermocouple contact the slurry material in the hollow cylindrical crucible. Place the water vapor generator on the other side of the glass tube and make the water vapor tube of the water vapor generator extend into the glass tube. (4) Turn on the steam generator and microwave tube furnace to raise the temperature of the slurry material in the hollow cylindrical crucible to the target temperature and keep it at that temperature for 20-40 minutes. After naturally cooling to room temperature, take it out to obtain niobium pentoxide.

2. The method for preparing niobium pentoxide by defluorination according to claim 1, characterized in that: In step (1), the niobium hydroxide raw material is niobium hydroxide obtained by wet sulfuric acid-hydrofluoric acid mixed acid leaching process HF-H2SO4 method, wet hydrochloric acid-hydrofluoric acid mixed acid leaching process HCl-HF method, or fluorine-containing salt melt-leaching process NaF / KF system.

3. The method for preparing niobium pentoxide by defluorination according to claim 2, characterized in that: In step (1), the mass ratio of niobium hydroxide raw material to deionized water is (1-5):1, and the stirring speed is 200-400 rpm.

4. The method for preparing niobium pentoxide by defluorination according to claim 1, characterized in that: In step (2), the hollow cylindrical crucible has an inner diameter of 50 mm, an outer diameter of 54 mm, a length of 150 mm, and a thickness of 5 mm.

5. The method for preparing niobium pentoxide by defluorination according to claim 1, characterized in that: In step (2), the inner diameter of the glass tube is 56mm, the outer diameter is 60mm, the length is 1500mm, and the thickness is 2mm.

6. The method for preparing niobium pentoxide by defluorination according to claim 1, characterized in that: In step (3), the thermocouple is a type K thermocouple; the water vapor tube extends 10 mm into the glass tube.

7. The method for preparing niobium pentoxide by defluorination according to claim 1, characterized in that: In step (4), the steam flow rate of the steam generator is 0.05-0.2 L / h, and the steam temperature is room temperature.

8. The method for preparing niobium pentoxide by defluorination according to claim 1, characterized in that: In step (4), the microwave frequency of the microwave tube furnace is 2.45 GHz and the microwave power is 2000 W.

9. The method for preparing niobium pentoxide by defluorination according to claim 1, characterized in that: In step (4), the target temperature is 500-800℃.