Preparation method of 4N or more super-high purity molybdenum powder

Abstract

The application provides a preparation method of 4N-grade or above super-high-purity molybdenum powder, comprising the following steps: dissolving molybdenum-containing raw materials in hydrogen peroxide, removing solid residues by filtration to obtain a crude permolybdate solution; adjusting the pH value of the crude permolybdate solution to 2.0-4.0, adding a complexing agent after hydrolysis and precipitation, and then sequentially performing active carbon adsorption, solvent extraction and membrane filtration to obtain a mixed refined solution; performing azeotropic distillation on the mixed refined solution, concentrating and crystallizing, drying in an oxygen-containing atmosphere and calcining to obtain high-purity molybdenum trioxide powder; performing three-stage gradient reduction on the high-purity molybdenum trioxide powder in a hydrogen atmosphere, performing surface passivation after cooling, and obtaining 4N-grade or above super-high-purity molybdenum powder. The preparation method of 4N-grade or above super-high-purity molybdenum powder provided by the application realizes full-process deep control of refractory impurities, has wide raw material adaptability, is green and controllable, and is suitable for large-scale production.

Description

Technical Field

[0001] This application belongs to the field of materials preparation technology and relates to a method for preparing ultra-high purity molybdenum powder of grade 4N or higher. Background Technology

[0002] Molybdenum, a refractory metal with a high melting point, high thermal conductivity, and low thermal expansion, is a fundamental material in semiconductor chip electrodes, flat panel display targets, high-temperature alloys, and the nuclear industry. As semiconductor manufacturing processes advance towards 7nm and below, the purity requirements for molybdenum powder continue to increase. In particular, refractory metal impurities such as W, Ta, Nb, and Zr can severely affect the uniformity of target film formation and the electrical performance of devices. Therefore, there is an urgent need to develop ultra-high purity molybdenum powder preparation technology that can control the total refractory metal impurities to below 0.5ppm.

[0003] Currently, wet purification routes for high-purity molybdenum powder are mainly divided into two categories: one is the ammonia purification process using ammonium molybdate as raw material, which removes impurities through ion exchange, extraction, and other means. However, this process generates a large amount of ammonia nitrogen wastewater, resulting in high environmental treatment costs and difficulty in deeply removing refractory metal impurities with properties similar to molybdenum. The other is the hydrogen peroxide hydrogen hydration dissolution process, which utilizes the property of molybdenum forming a soluble peroxide complex with hydrogen peroxide to achieve the dissolution and preliminary purification of molybdenum. This process is simple to operate and the reagents are easily decomposed without residue. However, the existing process does not utilize the difference in solubility between molybdenum and refractory metal peroxide complexes for selective separation. A large amount of refractory impurities such as W, Ta, and Nb enter the liquid phase along with molybdenum. Subsequent simple water washing and decomposition cannot achieve deep removal, and the purity of the final product is generally lower than 99.996%, which is difficult to meet the stringent requirements of the high-end semiconductor field.

[0004] In addition, existing hydrogen reduction processes mostly employ one or two stages of heating without designing a gradient reduction regime that takes into account the volatilization characteristics of impurities. This makes it impossible to further synergistically remove refractory impurities remaining at grain boundaries during the reduction process, thus restricting further improvement in the purity of molybdenum powder. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to provide a method for preparing ultra-high purity molybdenum powder of grade 4N and above. This method achieves in-depth control of refractory impurities throughout the entire process, has wide raw material adaptability, and is a green and controllable process suitable for large-scale production.

[0006] To achieve this objective, the present application adopts the following technical solution:

[0007] This application provides a method for preparing ultra-high purity molybdenum powder of grade 4N or higher, comprising the following steps:

[0008] (1) Dissolve the molybdenum-containing raw material with hydrogen peroxide, filter to remove solid residue, and obtain crude permolybdic acid solution;

[0009] (2) Adjust the pH of the crude permolybdic acid solution to 2.0~4.0, hydrolyze and precipitate, add a complexing agent, and then perform activated carbon adsorption, solvent extraction and membrane filtration in sequence to obtain a mixed purified solution;

[0010] (3) The mixed refined liquid is subjected to azeotropic distillation, concentrated and crystallized, and dried and calcined in an oxygen-containing atmosphere to obtain high-purity molybdenum trioxide powder;

[0011] (4) The high-purity molybdenum trioxide powder is subjected to a three-stage gradient reduction in a hydrogen atmosphere, and then surface passivation is performed after cooling to obtain the ultra-high purity molybdenum powder of grade 4N or above.

[0012] The preparation method provided in this application utilizes a selective oxidation dissolution process with hydrogen peroxide. Taking advantage of the difference in stability and solubility of molybdenum and refractory metals such as W, Ta, and Nb in their peroxide complexes, it effectively intercepts a significant amount of refractory metal impurities at the source, reducing the impurity removal load in subsequent refining processes. A multi-stage impurity removal system consisting of pH hydrolysis precipitation, activated carbon adsorption, selective extraction, and membrane filtration simultaneously and deeply removes conventional metals, trace amounts of refractory metals, and colloidal impurities, reducing the total metal impurities in the liquid phase to below 1 ppm. The precursor preparation process employing azeotropic distillation combined with drying and calcination avoids premature separation of permolybdic acid due to high-temperature concentration. By decapsulating impurities, organic components and volatile impurities can be removed to prepare orthorhombic molybdenum trioxide powder with a pure phase. Combined with a three-stage gradient reduction process, while reducing molybdenum oxide step by step, the total amount of refractory impurities in the powder is further reduced through the synergistic effect of low-temperature removal of volatile impurities, medium-temperature precise reduction of molybdenum components, and high-temperature promotion of grain boundary impurity migration and volatilization. Finally, it stably produces 4N~5N grade ultra-high purity molybdenum powder that meets the requirements of high-end semiconductor targets. Moreover, the whole process does not rely on high-purity ammonium molybdate raw materials, is compatible with a variety of molybdenum-containing materials, the reagents are easily decomposed and leave no residue, and it has strong environmental protection and industrial adaptability.

[0013] In some embodiments, the temperature at which hydrogen peroxide dissolves the molybdenum-containing raw material in step (1) is ≤15°C.

[0014] In some embodiments, the molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material in step (1) is 2.5:1 to 4:1.

[0015] In some embodiments, the molybdenum-containing raw material in step (1) includes industrial molybdenum powder and / or molybdenum trioxide.

[0016] In some embodiments, step (2) involves adjusting the pH of the crude permolybdic acid solution to 2.0-4.0 using ammonia or nitric acid.

[0017] In some embodiments, the complexing agent in step (2) is gluconic acid.

[0018] In some embodiments, the amount of the complexing agent added is 0.1wt% to 0.5wt% of the total mass of the system.

[0019] In some embodiments, the activated carbon used in step (2) adsorption is 0.1wt% to 0.5wt% of the total mass of the system.

[0020] In some embodiments, the activated carbon adsorption method in step (2) includes stirring at room temperature.

[0021] In some embodiments, the extractant used in step (2) of solvent extraction includes N235;

[0022] In some embodiments, the solvent extraction method in step (2) includes countercurrent extraction;

[0023] In some embodiments, the solvent-extracted loaded organic phase in step (2) is back-extracted with 5wt%~10wt% nitric acid to obtain a molybdenum-containing aqueous phase; n-butanol and / or isopropanol are added to the molybdenum-containing aqueous phase, and then the membrane filtration is performed.

[0024] In some embodiments, the membrane filtration includes: ultrafiltration using an ultrafiltration membrane with a molecular weight cutoff of 100,000 Da to 500,000 Da, followed by nanofiltration using a nanofiltration membrane with a molecular weight cutoff of 1,000 Da to 5,000 Da.

[0025] In some embodiments, the azeotropic distillation temperature is 60°C to 80°C.

[0026] In some embodiments, the absolute pressure of the azeotropic distillation is 0.02 MPa to 0.05 MPa.

[0027] In some embodiments, the drying temperature is 80°C to 120°C, and the time is 1 hour to 2 hours.

[0028] In some embodiments, the calcination temperature is 380℃~450℃ and the time is 2h~4h.

[0029] In some embodiments, the three-stage gradient reduction includes: first, a first reduction at 420℃~480℃ for 1h~3h; then, a second reduction at 620℃~680℃ for 1h~3h; and finally, a third reduction at 980℃~1050℃ for 1h~3h.

[0030] In some embodiments, the surface passivation is performed at temperatures below 80°C.

[0031] In some embodiments, the surface passivation is performed using an argon-oxygen mixture with an oxygen volume percentage of 0.5% to 2%.

[0032] In some embodiments, the surface passivation time is 30 min to 60 min.

[0033] As a preferred embodiment of the preparation method provided in this application, the preparation method includes the following steps:

[0034] (1) Dissolve the molybdenum-containing raw material with hydrogen peroxide at a temperature ≤15℃, filter to remove solid residue, and obtain crude permolybdic acid solution;

[0035] The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 2.5:1 to 4:1;

[0036] The molybdenum-containing raw materials include industrial molybdenum powder and / or molybdenum trioxide;

[0037] (2) Adjust the pH of the crude permolybdic acid solution to 2.0~4.0, hydrolyze and precipitate, add a complexing agent, and then perform activated carbon adsorption, solvent extraction and membrane filtration in sequence to obtain a mixed purified solution;

[0038] The complexing agent is gluconic acid, and the amount of the complexing agent added is 0.1wt%~0.5wt% of the total mass of the system.

[0039] The activated carbon adsorption method includes stirring at room temperature, and the activated carbon used accounts for 0.1wt%~0.5wt% of the total mass of the system.

[0040] The solvent extraction uses N235 as the extractant, and the solvent extraction method includes countercurrent extraction.

[0041] The solvent-extracted loaded organic phase is back-extracted with 5wt%~10wt% nitric acid to obtain a molybdenum-containing aqueous phase; n-butanol and / or isopropanol are added to the molybdenum-containing aqueous phase, and then the membrane is filtered.

[0042] The membrane filtration includes: ultrafiltration using an ultrafiltration membrane with a molecular weight cutoff of 100,000 Da to 500,000 Da, followed by nanofiltration using a nanofiltration membrane with a molecular weight cutoff of 1,000 Da to 5,000 Da.

[0043] (3) The mixed refined liquid is subjected to azeotropic distillation, concentrated and crystallized, and dried and calcined in an oxygen-containing atmosphere to obtain high-purity molybdenum trioxide powder;

[0044] The azeotropic distillation temperature is 60℃~80℃, and the absolute pressure is 0.02MPa~0.05MPa;

[0045] The drying temperature is 80℃~120℃, and the time is 1h~2h;

[0046] The calcination temperature is 380℃~450℃, and the time is 2h~4h;

[0047] (4) The high-purity molybdenum trioxide powder is subjected to a three-stage gradient reduction in a hydrogen atmosphere, and then surface passivation is performed after cooling to obtain the ultra-high purity molybdenum powder of grade 4N or above.

[0048] The three-stage gradient reduction includes: first, a first reduction at 420℃~480℃ for 1h~3h; then, a second reduction at 620℃~680℃ for 1h~3h; and finally, a third reduction at 980℃~1050℃ for 1h~3h.

[0049] The surface passivation is carried out at a temperature below 80°C, using an argon-oxygen mixture with an oxygen volume percentage of 0.5% to 2%, for a time of 30 to 60 minutes.

[0050] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0051] Compared with the prior art, this application has the following advantages:

[0052] The method for preparing ultra-high purity molybdenum powder of grade 4N and above provided in this application employs a selective oxidation dissolution process using hydrogen peroxide. This process utilizes the difference in stability and solubility of molybdenum with refractory metals such as W, Ta, and Nb in peroxide complexes to intercept a significant amount of refractory metal impurities at the source, reducing the impurity removal load in subsequent refining processes. A multi-stage impurity removal system consisting of pH hydrolysis precipitation, activated carbon adsorption, selective extraction, and membrane filtration can simultaneously and deeply remove conventional metals, trace amounts of refractory metals, and colloidal impurities, reducing the total metal impurities in the liquid phase to below 1 ppm. The precursor preparation process employs azeotropic distillation combined with drying and calcination to avoid the drawbacks caused by high-temperature concentration. By pre-decomposing and encapsulating impurities with permolybdic acid, organic components and volatile impurities can be removed, resulting in orthorhombic molybdenum trioxide powder with a pure phase. Combined with a three-stage gradient reduction process, while reducing molybdenum oxide step by step, the total amount of refractory impurities in the powder is further reduced through the synergistic effect of low-temperature removal of volatile impurities, medium-temperature precise reduction of molybdenum components, and high-temperature promotion of grain boundary impurity migration and volatilization. Ultimately, it stably produces 4N~5N grade ultra-high purity molybdenum powder that meets the requirements of high-end semiconductor targets. Moreover, the entire process does not rely on high-purity ammonium paramolybdate raw materials, is compatible with a variety of molybdenum-containing materials, the reagents are easily decomposed and leave no residue, and it has strong environmental friendliness and industrial compatibility. Detailed Implementation

[0053] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0054] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be independently included or excluded, and they can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0055] In this application, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any one or at least two combinations" means one or more of the two. It can be understood that "a combination of at least two" refers to any suitable combination of multiple items, that is, a combination of "at least two" items that are not conflicting and can be implemented in the manner described in this application.

[0056] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0057] The term "embodiment" as used in this application means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0058] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0059] In this application, open-ended technical features or solutions described with terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both technical features or solutions where "A consists of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0060] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0061] This application provides a method for preparing ultra-high purity molybdenum powder of grade 4N or higher, comprising the following steps:

[0062] (1) Dissolve the molybdenum-containing raw material with hydrogen peroxide, filter to remove solid residue, and obtain crude permolybdic acid solution;

[0063] (2) Adjust the pH of the crude permolybdic acid solution to 2.0~4.0, hydrolyze and precipitate, add a complexing agent, and then perform activated carbon adsorption, solvent extraction and membrane filtration in sequence to obtain a mixed purified solution;

[0064] (3) The mixed refined liquid is subjected to azeotropic distillation, concentrated and crystallized, and dried and calcined in an oxygen-containing atmosphere to obtain high-purity molybdenum trioxide powder;

[0065] (4) The high-purity molybdenum trioxide powder is subjected to a three-stage gradient reduction in a hydrogen atmosphere, and then surface passivation is performed after cooling to obtain the ultra-high purity molybdenum powder of grade 4N or above.

[0066] The preparation method provided in this application utilizes a selective oxidation dissolution process with hydrogen peroxide. Taking advantage of the difference in stability and solubility of molybdenum and refractory metals such as W, Ta, and Nb in their peroxide complexes, it effectively intercepts a significant amount of refractory metal impurities at the source, reducing the impurity removal load in subsequent refining processes. A multi-stage impurity removal system consisting of pH hydrolysis precipitation, activated carbon adsorption, selective extraction, and membrane filtration simultaneously and deeply removes conventional metals, trace amounts of refractory metals, and colloidal impurities, reducing the total metal impurities in the liquid phase to below 1 ppm. The precursor preparation process employing azeotropic distillation combined with drying and calcination avoids premature separation of permolybdic acid due to high-temperature concentration. By decapsulating impurities, organic components and volatile impurities can be removed to prepare orthorhombic molybdenum trioxide powder with a pure phase. Combined with a three-stage gradient reduction process, while reducing molybdenum oxide step by step, the total amount of refractory impurities in the powder is further reduced through the synergistic effect of low-temperature removal of volatile impurities, medium-temperature precise reduction of molybdenum components, and high-temperature promotion of grain boundary impurity migration and volatilization. Finally, it stably produces 4N~5N grade ultra-high purity molybdenum powder that meets the requirements of high-end semiconductor targets. Moreover, the whole process does not rely on high-purity ammonium molybdate raw materials, is compatible with a variety of molybdenum-containing materials, the reagents are easily decomposed and leave no residue, and it has strong environmental protection and industrial adaptability.

[0067] In some embodiments, the temperature at which hydrogen peroxide dissolves the molybdenum-containing raw material in step (1) is ≤15°C, for example, it can be 5°C, 6°C, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C or 15°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] In some embodiments, the molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material in step (1) is 2.5:1 to 4:1, for example, it can be 2.5:1, 2.7:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.6:1 or 4:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] In some embodiments, the molybdenum-containing raw material in step (1) includes industrial molybdenum powder and / or molybdenum trioxide.

[0070] In some embodiments, step (2) uses ammonia or nitric acid to adjust the pH of the crude permolybdic acid solution to 2.0 to 4.0, for example, 2, 2.5, 3, 3.5 or 4, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0071] In some embodiments, the complexing agent in step (2) is gluconic acid.

[0072] In some embodiments, the amount of complexing agent added is 0.1wt% to 0.5wt% of the total mass of the system, for example, it can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt% or 0.5wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] In some embodiments, when the activated carbon adsorption is performed in step (2), the mass of activated carbon used is 0.1wt% to 0.5wt% of the total mass of the system. For example, it can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt% or 0.5wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] The total mass of the system refers to the total mass of the added objects when the corresponding components are added.

[0075] In some embodiments, the activated carbon adsorption method in step (2) includes stirring at room temperature.

[0076] In some embodiments, the extractant used in step (2) of solvent extraction includes N235.

[0077] In some embodiments, the solvent extraction method in step (2) includes countercurrent extraction.

[0078] Optionally, during solvent extraction, the volume ratio of the oil phase to the aqueous phase can be 1:2 to 1:4, for example, 1:2, 1:3 or 1:4, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, with 1:3 being the preferred ratio.

[0079] In some embodiments, the organic phase loaded by solvent extraction in step (2) is back-extracted with 5wt% to 10wt% (e.g., 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, or 10wt%) of nitric acid to obtain a molybdenum-containing aqueous phase; n-butanol and / or isopropanol are added to the molybdenum-containing aqueous phase, and then the membrane filtration is performed.

[0080] In some embodiments, the membrane filtration includes: ultrafiltration using an ultrafiltration membrane with a molecular weight cutoff of 100,000 Da to 500,000 Da (e.g., 100,000 Da, 150,000 Da, 200,000 Da, 250,000 Da, 300,000 Da, 350,000 Da, 400,000 Da, 450,000 Da, or 500,000 Da, etc.), followed by nanofiltration using a nanofiltration membrane with a molecular weight cutoff of 1,000 Da to 5,000 Da (e.g., 1,000 Da, 1,500 Da, 2,000 Da, 2,500 Da, 3,000 Da, 3,500 Da, 4,000 Da, 4,500 Da, or 5,000 Da, etc.).

[0081] In some embodiments, the azeotropic distillation temperature is 60°C to 80°C, for example, 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0082] In some embodiments, the absolute pressure of the azeotropic distillation is 0.02 MPa to 0.05 MPa, for example, it can be 0.02 MPa, 0.03 MPa, 0.04 MPa or 0.05 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0083] In some embodiments, the drying temperature is 80°C to 120°C, and the time is 1 hour to 2 hours.

[0084] The drying temperature is 80℃~120℃, for example, it can be 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0085] The drying time is 1 to 2 hours, for example, 1 hour, 1.2 hours, 1.5 hours, 1.6 hours, 1.8 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0086] In some embodiments, the calcination temperature is 380℃~450℃ and the time is 2h~4h.

[0087] The calcination temperature is 380℃~450℃, for example, it can be 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃ or 450℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0088] The calcination time is 2h to 4h, for example, it can be 2h, 2.5h, 3h, 3.5h or 4h, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0089] In some embodiments, the three-stage gradient reduction includes: first, a first reduction at 420℃~480℃ for 1h~3h; then, a second reduction at 620℃~680℃ for 1h~3h; and finally, a third reduction at 980℃~1050℃ for 1h~3h.

[0090] The temperature for the first reduction is 420℃~480℃, for example, it can be 420℃, 430℃, 440℃, 450℃, 460℃, 470℃ or 480℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0091] The first restoration time is 1 hour to 3 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0092] The second reduction temperature is 620℃~680℃, for example, it can be 620℃, 630℃, 640℃, 650℃, 660℃, 670℃ or 680℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0093] The second reduction time is 1 hour to 3 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0094] The temperature for the third reduction is 980℃~1050℃, for example, it can be 980℃, 990℃, 1000℃, 1010℃, 1020℃, 1030℃, 1040℃ or 1050℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0095] The third reduction time is 1 to 3 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0096] In some embodiments, the surface passivation is performed at temperatures below 80°C.

[0097] In some embodiments, the surface passivation is performed using an argon-oxygen mixture with an oxygen volume percentage of 0.5% to 2%, for example, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.6%, 1.8%, or 2%, but not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0098] In some embodiments, the surface passivation time is 30 min to 60 min, for example, it can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0099] As a preferred embodiment of the preparation method provided in this application, the preparation method includes the following steps:

[0100] (1) Dissolve the molybdenum-containing raw material with hydrogen peroxide at a temperature ≤15℃, filter to remove solid residue, and obtain crude permolybdic acid solution;

[0101] The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 2.5:1 to 4:1;

[0102] The molybdenum-containing raw materials include industrial molybdenum powder and / or molybdenum trioxide;

[0103] (2) Adjust the pH of the crude permolybdic acid solution to 2.0~4.0, hydrolyze and precipitate, add a complexing agent, and then perform activated carbon adsorption, solvent extraction and membrane filtration in sequence to obtain a mixed purified solution;

[0104] The complexing agent is gluconic acid, and the amount of the complexing agent added is 0.1wt%~0.5wt% of the total mass of the system.

[0105] The activated carbon adsorption method includes stirring at room temperature, and the activated carbon used accounts for 0.1wt%~0.5wt% of the total mass of the system.

[0106] The solvent extraction uses N235 as the extractant and the solvent extraction method includes countercurrent extraction, with an oil phase to water phase volume ratio of 1:3.

[0107] The solvent-extracted loaded organic phase is back-extracted with 5wt%~10wt% nitric acid to obtain a molybdenum-containing aqueous phase; n-butanol and / or isopropanol are added to the molybdenum-containing aqueous phase, and then the membrane is filtered.

[0108] The membrane filtration includes: ultrafiltration using an ultrafiltration membrane with a molecular weight cutoff of 100,000 Da to 500,000 Da, followed by nanofiltration using a nanofiltration membrane with a molecular weight cutoff of 1,000 Da to 5,000 Da.

[0109] (3) The mixed refined liquid is subjected to azeotropic distillation, concentrated and crystallized, and dried and calcined in an oxygen-containing atmosphere to obtain high-purity molybdenum trioxide powder;

[0110] The azeotropic distillation temperature is 60℃~80℃, and the absolute pressure is 0.02MPa~0.05MPa;

[0111] The drying temperature is 80℃~120℃, and the time is 1h~2h;

[0112] The calcination temperature is 380℃~450℃, and the time is 2h~4h;

[0113] (4) The high-purity molybdenum trioxide powder is subjected to a three-stage gradient reduction in a hydrogen atmosphere, and then surface passivation is performed after cooling to obtain the ultra-high purity molybdenum powder of grade 4N or above.

[0114] The three-stage gradient reduction includes: first, a first reduction at 420℃~480℃ for 1h~3h; then, a second reduction at 620℃~680℃ for 1h~3h; and finally, a third reduction at 980℃~1050℃ for 1h~3h.

[0115] The surface passivation is carried out at a temperature below 80°C, using an argon-oxygen mixture with an oxygen volume percentage of 0.5% to 2%, for a time of 30 to 60 minutes.

[0116] To clearly illustrate the technical solution of this application, the molybdenum-containing raw material in the following embodiments and comparative examples is industrial molybdenum powder, which, calculated by mass percentage, mainly includes: 80.2 wt% molybdenum, 3.5 wt% iron, 1.8 wt% aluminum, 0.6 wt% titanium, 0.3 wt% zirconium, 1.2 wt% silicon, 0.8 wt% tungsten, 0.15 wt% potassium, 0.08 wt% sodium, and trace amounts of nickel, chromium, calcium, magnesium, and other elements. The membrane filtration in the following embodiments and comparative examples includes: ultrafiltration using an ultrafiltration membrane with a molecular weight cutoff of 300,000 Da, followed by nanofiltration using a nanofiltration membrane with a molecular weight cutoff of 3,000 Da. The above description is only for clearly illustrating the technical solution of this application and is not considered a further limitation of this application.

[0117] Example 1

[0118] This embodiment provides a method for preparing ultra-high purity molybdenum powder, including the following steps:

[0119] (1) Dissolve the molybdenum-containing raw material with hydrogen peroxide at a temperature of 15℃, filter to remove solid residue, and obtain crude permolybdic acid solution;

[0120] The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 3:1;

[0121] (2) Adjust the pH of the crude permolybdic acid solution to 3.0, hydrolyze and precipitate, add a complexing agent, and then perform activated carbon adsorption, solvent extraction and membrane filtration in sequence to obtain a mixed purified solution;

[0122] The complexing agent is gluconic acid, and the amount of the complexing agent added is 0.3 wt% of the total mass of the system.

[0123] The activated carbon adsorption method includes stirring at room temperature, and the mass of activated carbon used is 0.3 wt% of the total mass of the system.

[0124] The solvent extraction uses N235 as the extractant and the solvent extraction method includes countercurrent extraction, with an oil phase to water phase volume ratio of 1:3.

[0125] The solvent-extracted loaded organic phase is back-extracted with 8 wt% nitric acid to obtain a molybdenum-containing aqueous phase; n-butanol is added to the molybdenum-containing aqueous phase, and then membrane filtration is performed.

[0126] (3) The mixed refined liquid is subjected to azeotropic distillation, concentrated and crystallized, dried and calcined in air atmosphere to obtain high-purity molybdenum trioxide powder;

[0127] The azeotropic distillation temperature was 70°C and the absolute pressure was 0.03 MPa.

[0128] The drying temperature is 100℃ and the time is 1.5h;

[0129] The calcination temperature was 400℃ and the time was 3 hours.

[0130] (4) The high-purity molybdenum trioxide powder is subjected to a three-stage gradient reduction in a hydrogen atmosphere, and then surface passivation is performed after cooling to obtain ultra-high-purity molybdenum powder.

[0131] The three-stage gradient reduction includes: first, a first reduction at 450℃ for 2 hours; then, a second reduction at 650℃ for 2 hours; and finally, a third reduction at 1000℃ for 2 hours.

[0132] The surface passivation was performed at a temperature of 80°C using an argon-oxygen mixture with an oxygen volume percentage of 0.1% for 45 minutes.

[0133] Example 2

[0134] This embodiment provides a method for preparing ultra-high purity molybdenum powder, including the following steps:

[0135] (1) Dissolve the molybdenum-containing raw material with hydrogen peroxide at a temperature of 15℃, filter to remove solid residue, and obtain crude permolybdic acid solution;

[0136] The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 2.5:1;

[0137] (2) Adjust the pH of the crude permolybdic acid solution to 2.0, hydrolyze and precipitate, add a complexing agent, and then perform activated carbon adsorption, solvent extraction and membrane filtration in sequence to obtain a mixed purified solution;

[0138] The complexing agent is gluconic acid, and the amount of the complexing agent added is 0.1 wt% of the total mass of the system.

[0139] The activated carbon adsorption method includes stirring at room temperature, and the mass of activated carbon used is 0.1 wt% of the total mass of the system.

[0140] The solvent extraction uses N235 as the extractant and the solvent extraction method includes countercurrent extraction, with an oil phase to water phase volume ratio of 1:3.

[0141] The solvent-extracted loaded organic phase is back-extracted with 5 wt% nitric acid to obtain a molybdenum-containing aqueous phase; n-butanol is added to the molybdenum-containing aqueous phase, and then membrane filtration is performed.

[0142] (3) The mixed refined liquid is subjected to azeotropic distillation, concentrated and crystallized, dried and calcined in air atmosphere to obtain high-purity molybdenum trioxide powder;

[0143] The azeotropic distillation temperature was 60°C and the absolute pressure was 0.02 MPa.

[0144] The drying temperature is 80℃ and the time is 2 hours;

[0145] The calcination temperature was 380℃ and the time was 4 hours.

[0146] (4) The high-purity molybdenum trioxide powder is subjected to a three-stage gradient reduction in a hydrogen atmosphere, and then surface passivation is performed after cooling to obtain ultra-high-purity molybdenum powder.

[0147] The three-stage gradient reduction includes: first, a first reduction at 420℃ for 3 hours; then, a second reduction at 620℃ for 3 hours; and finally, a third reduction at 980℃ for 3 hours.

[0148] The surface passivation was performed at a temperature of 80°C using an argon-oxygen mixture with an oxygen volume percentage of 0.5%, for a duration of 60 minutes.

[0149] Example 3

[0150] This embodiment provides a method for preparing ultra-high purity molybdenum powder, including the following steps:

[0151] (1) Dissolve the molybdenum-containing raw material with hydrogen peroxide at a temperature of 15℃, filter to remove solid residue, and obtain crude permolybdic acid solution;

[0152] The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 4:1;

[0153] (2) Adjust the pH of the crude permolybdic acid solution to 4.0, hydrolyze and precipitate, add a complexing agent, and then perform activated carbon adsorption, solvent extraction and membrane filtration in sequence to obtain a mixed purified solution;

[0154] The complexing agent is gluconic acid, and the amount of the complexing agent added is 0.5 wt% of the total mass of the system.

[0155] The activated carbon adsorption method includes stirring at room temperature, and the mass of activated carbon used is 0.5 wt% of the total mass of the system.

[0156] The solvent extraction uses N235 as the extractant and the solvent extraction method includes countercurrent extraction, with an oil phase to water phase volume ratio of 1:3.

[0157] The solvent-extracted loaded organic phase is back-extracted with 10 wt% nitric acid to obtain a molybdenum-containing aqueous phase; n-butanol is added to the molybdenum-containing aqueous phase, and then membrane filtration is performed.

[0158] (3) The mixed refined liquid is subjected to azeotropic distillation, concentrated and crystallized, dried and calcined in air atmosphere to obtain high-purity molybdenum trioxide powder;

[0159] The azeotropic distillation temperature is 80℃ and the absolute pressure is 0.05MPa;

[0160] The drying temperature is 120℃ and the time is 1 hour;

[0161] The calcination temperature was 450℃ and the time was 2 hours.

[0162] (4) The high-purity molybdenum trioxide powder is subjected to a three-stage gradient reduction in a hydrogen atmosphere, and then surface passivation is performed after cooling to obtain ultra-high-purity molybdenum powder.

[0163] The three-stage gradient reduction includes: first, a first reduction at 480℃ for 1 hour; then, a second reduction at 680℃ for 1 hour; and finally, a third reduction at 1050℃ for 1 hour.

[0164] The surface passivation was performed at a temperature of 80°C using an argon-oxygen mixture with 2% oxygen by volume for 30 minutes.

[0165] Example 4

[0166] This embodiment provides a method for preparing ultra-high purity molybdenum powder. Except that the amount of complexing agent is 0.01 wt% of the total mass of the system, the rest is the same as in Example 1.

[0167] Example 5

[0168] This embodiment provides a method for preparing ultra-high purity molybdenum powder. Except that the amount of complexing agent is 0.6 wt% of the total mass of the system, the rest is the same as in Example 1.

[0169] Example 6

[0170] This embodiment provides a method for preparing ultra-high purity molybdenum powder. Except for the temperature at which hydrogen peroxide dissolves the molybdenum-containing raw material, which is 20°C, the rest is the same as in Example 1.

[0171] Example 7

[0172] This embodiment provides a method for preparing ultra-high purity molybdenum powder, which is the same as in Example 1 except that the first reduction is not performed.

[0173] Example 8

[0174] This embodiment provides a method for preparing ultra-high purity molybdenum powder, which is the same as in Example 1 except that a second reduction is not performed.

[0175] Example 9

[0176] This embodiment provides a method for preparing ultra-high purity molybdenum powder. Except for the oxygen volume fraction of 0.1% in the surface passivation treatment, the rest is the same as in Example 1.

[0177] Example 10

[0178] This embodiment provides a method for preparing ultra-high purity molybdenum powder. Except for the oxygen volume fraction of 3% in the surface passivation treatment, the rest is the same as in Example 1.

[0179] Comparative Example 1

[0180] This comparative example provides a method for preparing ultra-high purity molybdenum powder, which is the same as in Example 1 except that no complexing agent is used.

[0181] Performance Characterization

[0182] The purity, total refractory metal impurity content, and oxygen content of the ultra-high purity molybdenum powder obtained in the above examples were measured, and the results are shown in Table 1.

[0183] Table 1

[0184]

[0185] As can be seen from Examples 1 to 3 in Table 1, the preparation method of ultra-high purity molybdenum powder of grade 4N or above provided in this application can stably produce ultra-high purity molybdenum powder with a purity ≥99.9990% under the preferred process parameters, with the total impurity content of refractory metals as low as 0.00015% and the oxygen content controlled below 0.0007wt%.

[0186] A comparison of Examples 4 and 5 with Example 1 shows that the amount of gluconic acid added as a complexing agent affects the depth of removal of refractory metal impurities and the purity of the product. When the amount added is too low, down to 0.01 wt% (Example 4), the complexing and masking ability for refractory metals is insufficient, resulting in a decrease in the purity of the final molybdenum powder to 99.9982% and an increase in the total impurity content of refractory metals to 0.00028%. When the amount added is too high, up to 0.6 wt% (Example 5), the excessive organic complexing agent may remain or decompose in subsequent processes, similarly causing a decrease in purity and an increase in oxygen content.

[0187] A comparison of Example 6 and Example 1 shows that the temperature for dissolving molybdenum-containing raw materials with hydrogen peroxide needs to be strictly controlled below 15°C. When the dissolution temperature rises to 20°C, the total impurity content of refractory metals increases significantly from 0.00012% to 0.00055%, and the product purity drops to 99.9975%. This is because higher temperatures enhance the dissolution capacity of hydrogen peroxide for associated refractory metal oxides (such as WO3) in the raw materials, causing more refractory metals to enter the crude permolybdic acid solution. This weakens the core role of the dissolution step in removing impurities from the source through solid-liquid separation, increasing the burden on subsequent deep purification.

[0188] A comparison of Examples 7 and 8 with Example 1 shows that the oxygen content increases when the first reduction step (Example 7) is omitted; similarly, the oxygen content increases when the second reduction step (Example 8) is omitted. This is because the first reduction causes MoO3 to slowly transform into MoO2 and form fine crystal nuclei, which is beneficial for the uniform removal of oxygen and particle refinement in subsequent reduction processes; the second reduction further reduces MoO2 to metallic molybdenum; the absence of either stage disrupts the stepwise reduction rhythm, leading to insufficient deoxidation and abnormal particle growth, ultimately resulting in a deterioration in oxygen content and particle size control.

[0189] A comparison of Examples 9 and 10 with Example 1 shows that the oxygen volume fraction in the surface passivation treatment needs to be controlled within the range of 0.5% to 2%. When the oxygen volume fraction is too low (0.1%, Example 9), a complete and dense oxide film cannot be formed on the surface of the molybdenum powder, resulting in excessively high powder activity. During subsequent operations and storage, oxygen is easily adsorbed, leading to an oxygen content as high as 0.0013%. When the oxygen volume fraction is too high (3%, Example 10), the powder surface is over-oxidized, forming an excessively thick oxide layer, directly causing the product oxygen content to increase significantly to 0.0060%.

[0190] As can be seen from the comparison between Comparative Example 1 and Example 1, when no complexing agent gluconic acid was used, the complexing-solubilizing effect on refractory metals in the refining solution was missing, resulting in a significant increase in the total impurity content of refractory metals in the final molybdenum powder to 0.00120%, and the product purity also dropped to 99.9945%.

[0191] In summary, the preparation method for ultra-high purity molybdenum powder of grade 4N and above provided in this application employs a selective oxidation dissolution process using hydrogen peroxide. This process leverages the differences in stability and solubility of molybdenum with refractory metals such as W, Ta, and Nb in their peroxide complexes to remove a significant amount of refractory metal impurities at the source, reducing the impurity removal load in subsequent refining processes. A multi-stage impurity removal system consisting of pH hydrolysis precipitation, activated carbon adsorption, selective extraction, and membrane filtration simultaneously and deeply removes conventional metals, trace amounts of refractory metals, and colloidal impurities, reducing the total metal impurities in the liquid phase to below 1 ppm. The precursor preparation process, employing azeotropic distillation combined with drying and calcination, avoids high-temperature concentration... The shrinkage process leads to the premature decomposition and impurity encapsulation of permolybdate, which removes organic components and volatile impurities, resulting in the preparation of orthorhombic molybdenum trioxide powder with a pure phase. Combined with a three-stage gradient reduction process, while completing the reduction of molybdenum oxide step by step, the synergistic effect of removing volatile impurities at low temperature, accurately reducing molybdenum components at medium temperature, and promoting the migration and volatilization of grain boundary impurities at high temperature further reduces the total amount of refractory impurities in the powder. Ultimately, it stably produces 4N~5N grade ultra-high purity molybdenum powder that meets the requirements of high-end semiconductor target materials. Moreover, the entire process does not rely on high-purity ammonium paramolybdate raw materials, is compatible with a variety of molybdenum-containing materials, and the reagents are easily decomposed without residue, making it highly environmentally friendly and industrially adaptable.

[0192] The applicant declares that the above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A method for preparing ultra-high purity molybdenum powder of grade 4N or higher, characterized in that, Includes the following steps: (1) Dissolve the molybdenum-containing raw material with hydrogen peroxide, filter to remove solid residue, and obtain crude permolybdic acid solution; (2) Adjust the pH of the crude permolybdic acid solution to 2.0~4.0, hydrolyze and precipitate, add a complexing agent, and then perform activated carbon adsorption, solvent extraction and membrane filtration in sequence to obtain a mixed purified solution; (3) The mixed refined liquid is subjected to azeotropic distillation, concentrated and crystallized, and dried and calcined in an oxygen-containing atmosphere to obtain high-purity molybdenum trioxide powder; (4) The high-purity molybdenum trioxide powder is subjected to a three-stage gradient reduction in a hydrogen atmosphere, and then surface passivation is performed after cooling to obtain the ultra-high purity molybdenum powder of grade 4N or above.

2. The preparation method according to claim 1, characterized in that, In step (1), the temperature at which hydrogen peroxide dissolves the molybdenum-containing raw material is ≤15℃; And / or, the molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material in step (1) is 2.5:1 to 4:1; And / or, the molybdenum-containing raw material in step (1) includes industrial molybdenum powder and / or molybdenum trioxide.

3. The preparation method according to claim 1, characterized in that, Step (2) Adjust the pH of the crude permolybdic acid solution to 2.0~4.0 using ammonia or nitric acid.

4. The preparation method according to claim 1, characterized in that, The complexing agent in step (2) is gluconic acid; And / or, the amount of the complexing agent added is 0.1wt% to 0.5wt% of the total mass of the system.

5. The preparation method according to claim 1, characterized in that, In step (2), the activated carbon used for adsorption is 0.1 wt% to 0.5 wt% of the total mass of the system. And / or, the activated carbon adsorption method in step (2) includes stirring at room temperature.

6. The preparation method according to claim 1, characterized in that, The extractant used in step (2) of solvent extraction includes N235; And / or, the solvent extraction method in step (2) includes countercurrent extraction; And / or, the solvent-extracted loaded organic phase in step (2) is back-extracted with 5wt%~10wt% nitric acid to obtain a molybdenum-containing aqueous phase; n-butanol and / or isopropanol are added to the molybdenum-containing aqueous phase, and then the membrane filtration is performed.

7. The preparation method according to claim 6, characterized in that, The membrane filtration includes: ultrafiltration using an ultrafiltration membrane with a molecular weight cutoff of 100,000 Da to 500,000 Da, followed by nanofiltration using a nanofiltration membrane with a molecular weight cutoff of 1,000 Da to 5,000 Da.

8. The preparation method according to claim 1, characterized in that, The azeotropic distillation temperature is 60℃~80℃; And / or, the absolute pressure of the azeotropic distillation is 0.02 MPa to 0.05 MPa; And / or, the drying temperature is 80℃~120℃, and the time is 1h~2h; And / or, the calcination temperature is 380℃~450℃, and the time is 2h~4h.

9. The preparation method according to claim 1, characterized in that, The three-stage gradient reduction includes: first, a first reduction at 420℃~480℃ for 1h~3h; then, a second reduction at 620℃~680℃ for 1h~3h; and finally, a third reduction at 980℃~1050℃ for 1h~3h. And / or, the surface passivation is performed at a temperature below 80°C; And / or, the surface passivation is performed using an argon-oxygen mixture with an oxygen volume percentage of 0.5% to 2%; And / or, the surface passivation time is 30 min to 60 min.

10. The preparation method according to any one of claims 1 to 9, characterized in that, The preparation method includes the following steps: (1) Dissolve the molybdenum-containing raw material with hydrogen peroxide under the condition of temperature ≤15℃, filter to remove solid residue, and obtain crude permolybdic acid solution; The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 2.5:1 to 4:1; The molybdenum-containing raw materials include industrial molybdenum powder and / or molybdenum trioxide; (2) Adjust the pH of the crude permolybdic acid solution to 2.0~4.0, hydrolyze and precipitate, add a complexing agent, and then perform activated carbon adsorption, solvent extraction and membrane filtration in sequence to obtain a mixed purified solution; The complexing agent is gluconic acid, and the amount of the complexing agent added is 0.1wt%~0.5wt% of the total mass of the system. The activated carbon adsorption method includes stirring at room temperature, and the mass of activated carbon used is 0.1wt%~0.5wt% of the total mass of the system. The solvent extraction uses N235 as the extractant, and the solvent extraction method includes countercurrent extraction. The solvent-extracted loaded organic phase is back-extracted with 5wt%~10wt% nitric acid to obtain a molybdenum-containing aqueous phase; n-butanol and / or isopropanol are added to the molybdenum-containing aqueous phase, and then the membrane is filtered. The membrane filtration includes: ultrafiltration using an ultrafiltration membrane with a molecular weight cutoff of 100,000 Da to 500,000 Da, followed by nanofiltration using a nanofiltration membrane with a molecular weight cutoff of 1,000 Da to 5,000 Da. (3) The mixed refined liquid is subjected to azeotropic distillation, concentrated and crystallized, and dried and calcined in an oxygen-containing atmosphere to obtain high-purity molybdenum trioxide powder; The azeotropic distillation temperature is 60℃~80℃, and the absolute pressure is 0.02MPa~0.05MPa; The drying temperature is 80℃~120℃, and the time is 1h~2h; The calcination temperature is 380℃~450℃, and the time is 2h~4h; (4) The high-purity molybdenum trioxide powder is subjected to a three-stage gradient reduction in a hydrogen atmosphere, and then surface passivation is performed after cooling to obtain the ultra-high purity molybdenum powder of grade 4N or above. The three-stage gradient reduction includes: first, a first reduction at 420℃~480℃ for 1h~3h; then, a second reduction at 620℃~680℃ for 1h~3h; and finally, a third reduction at 980℃~1050℃ for 1h~3h. The surface passivation is carried out at a temperature below 80°C, using an argon-oxygen mixture with an oxygen volume percentage of 0.5% to 2%, for a time of 30 to 60 minutes.

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