Preparation method of ultra-high purity molybdenum powder

Abstract

The application provides a preparation method of ultra-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 2-4, adding a complexing agent after hydrolysis and precipitation; then performing resin adsorption and membrane filtration in sequence to obtain a refined permolybdate solution; performing vacuum concentration and crystallization of the refined permolybdate solution under the condition of ≤60 DEG C, then performing drying and calcination in an oxygen-containing atmosphere to obtain alpha-MoO3 powder; performing heat treatment and surface passivation treatment of the alpha-MoO3 powder in a reducing atmosphere to obtain the ultra-high purity molybdenum powder. The preparation method of the ultra-high purity molybdenum powder is simple in steps, high in impurity removal efficiency, and suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of molybdenum powder preparation technology, and relates to a method for preparing ultra-high purity molybdenum powder. Background Technology

[0002] Currently, the application of high-purity molybdenum powder in high-end target materials, special alloys, and advanced electronic materials places stringent requirements on its purity, necessitating the control of the total amount of refractory metal impurities such as tungsten, tantalum, and niobium at the sub-ppm level. At present, the wet preparation processes for high-purity molybdenum powder mainly include the ammonia-based wet process and the hydrogen peroxide liquid-phase oxidation-reduction route. The ammonia-based wet process primarily relies on the repeated dissolution and precipitation of ammonium paramolybdate, combined with resin purification, to achieve purification. The hydrogen peroxide liquid-phase oxidation-reduction route uses hydrogen peroxide as an oxidant to convert the molybdenum source into a permolybdic acid solution, which is then calcined and reduced with hydrogen to obtain the finished molybdenum powder.

[0003] However, in ammonia-based systems, tungsten and molybdate have highly similar chemical properties, making them prone to co-dissolution and co-precipitation. Existing methods for removing tungsten not only introduce secondary pollution but also have limited impurity removal capabilities. Furthermore, under conventional process conditions, hydrogen peroxide dissolution systems do not fully utilize the fundamental difference in complexation and dissolution capabilities between molybdenum and refractory metals in weakly acidic peroxy media, nor do they implement selective retention control during the dissolution process. This results in a large amount of impurities such as tungsten, tantalum, and niobium in the raw materials being transferred into the solution, forming colloidal or ionic impurities, which increases the difficulty of subsequent separation and purification.

[0004] The aforementioned limitations prevent conventional processes from achieving targeted and deep removal of refractory metal impurities through simple filtration, hydrolysis precipitation, or single resin exchange steps. Meanwhile, traditional hydrogen reduction processes often employ a single temperature-increasing reduction mode, failing to consider the physicochemical properties of different impurities to create a staged purification reaction environment, thus hindering the simultaneous migration of grain boundary impurities and reduction of low-volatile components. Consequently, the overall purity of molybdenum powder produced by existing processes is generally below 99.99%, and the total amount of refractory metal impurities is difficult to stably control below 0.5 ppm, far from meeting the quality standards of 4N~5N grade ultra-high purity molybdenum powder. Therefore, the industry urgently needs a new process route to solve the problem of refractory metal migration from the raw material to the solution and achieve purification in subsequent liquid-phase refining and reduction stages. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing ultra-high purity molybdenum powder. This method has simple steps, high impurity removal efficiency, and is suitable for industrial production.

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

[0007] This invention provides a method for preparing ultra-high purity molybdenum powder, the method 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 2-4, hydrolyze and precipitate, add a complexing agent; then perform resin adsorption and membrane filtration in sequence to obtain a refined permolybdic acid solution;

[0010] (3) The refined permolybdic acid solution is concentrated and crystallized under reduced pressure at ≤60℃, and then dried and calcined in an oxygen-containing atmosphere to obtain α-MoO3 powder;

[0011] (4) The α-MoO3 powder is subjected to heat treatment and surface passivation in a reducing atmosphere to obtain the ultra-high purity molybdenum powder.

[0012] This invention first dissolves molybdenum-containing raw materials with hydrogen peroxide. Utilizing the difference in solubility between molybdenum and refractory metal impurities, most of the refractory impurities are filtered and separated in solid form, significantly reducing the subsequent impurity removal load from the source. Subsequently, the pH of the resulting crude permolybdic acid solution is adjusted to 2-4 for hydrolysis precipitation. A complexing agent is then added to mask residual impurities, and deep purification is achieved through resin adsorption and membrane filtration to obtain a high-purity permolybdic acid solution. This solution is concentrated and crystallized under reduced pressure at ≤60℃, and then dried and calcined in an oxygen-containing atmosphere to prepare an α-MoO3 precursor, effectively avoiding impurity encapsulation and external contamination. Finally, the precursor undergoes stepwise heat treatment and surface passivation under a reducing atmosphere to further remove trace impurities, yielding ultra-high purity molybdenum powder. This invention features simple steps, strong impurity control, and is suitable for the industrial production of 4N-5N grade ultra-high purity molybdenum powder.

[0013] In some embodiments, the temperature at which the hydrogen peroxide dissolves the molybdenum-containing raw material is below 15°C.

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

[0015] In some embodiments, the molybdenum-containing raw material includes molybdenum powder and / or molybdenum trioxide.

[0016] In some embodiments, in step (2), the pH of the crude permolybdic acid solution is adjusted to 2-4 using nitric acid or ammonia.

[0017] In some embodiments, the complexing agent comprises fluoride and / or tartaric acid;

[0018] When the complexing agent is a fluoride, the amount of complexing agent used is such that the concentration of fluoride ions in the system is 0.001 mol / L to 0.01 mol / L;

[0019] When the complexing agent is tartaric acid, the amount of complexing agent used is such that the concentration of tartaric acid in the system is 0.01 mol / L to 0.05 mol / L.

[0020] In some embodiments, the fluoride includes any one or a combination of at least two of potassium fluoride, sodium fluoride, or ammonium fluoride.

[0021] In some embodiments, the resin adsorption includes sequentially using a styrene-based strong basic anion exchange resin and an iminodiacetic acid type aminocarboxyl chelating resin for resin adsorption.

[0022] The membrane filtration includes filtration using ultrafiltration membranes and / or nanofiltration membranes.

[0023] In some embodiments, the drying temperature is 80°C to 120°C.

[0024] In some embodiments, the drying time is 1 to 2 hours.

[0025] In some embodiments, the calcination temperature is 380°C to 450°C.

[0026] In some embodiments, the calcination time is 2h to 4h.

[0027] In some embodiments, the heat treatment includes: firstly, performing a first reduction at a temperature of 420°C to 480°C for 1 hour to 3 hours, then performing a second reduction at a temperature of 620°C to 680°C for 1 hour to 3 hours, and finally performing a third reduction at a temperature of 980°C to 1050°C for 1 hour to 3 hours.

[0028] In some embodiments, the surface passivation treatment includes passivation in an argon-oxygen mixture with an oxygen volume fraction of 0.5% to 2% for 30 to 60 minutes.

[0029] As a preferred embodiment of the preparation method provided by the present invention, the preparation method includes the following steps:

[0030] (1) Hydrogen peroxide is used to dissolve molybdenum-containing raw materials at temperatures below 15°C, and the solid residue is removed by filtration to obtain a crude permolybdic acid solution;

[0031] The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 2.5:1 to 4:1;

[0032] The molybdenum-containing raw material includes molybdenum powder and / or molybdenum trioxide;

[0033] (2) Adjust the pH of the crude permolybdic acid solution to 2-4 using nitric acid or ammonia, hydrolyze and precipitate, add a complexing agent; then perform resin adsorption and membrane filtration in sequence to obtain a refined permolybdic acid solution.

[0034] The complexing agent includes fluoride and / or tartaric acid, wherein the fluoride includes any one or a combination of at least two of potassium fluoride, sodium fluoride, or ammonium fluoride; when the complexing agent is fluoride, the amount of complexing agent used is such that the concentration of fluoride ions in the system is 0.001 mol / L to 0.01 mol / L; when the complexing agent is tartaric acid, the amount of complexing agent used is such that the concentration of tartaric acid in the system is 0.01 mol / L to 0.05 mol / L.

[0035] The resin adsorption process includes sequentially using a styrene-based strong basic anion exchange resin and an iminodiacetic acid type aminocarboxyl chelating resin for resin adsorption.

[0036] The membrane filtration includes filtration using ultrafiltration membranes and / or nanofiltration membranes;

[0037] (3) The refined permolybdic acid solution is concentrated and crystallized under reduced pressure at ≤60℃, and then dried and calcined in an oxygen-containing atmosphere to obtain α-MoO3 powder;

[0038] The drying temperature is 80℃~120℃, and the time is 1h~2h;

[0039] The calcination temperature is 380℃~450℃, and the time is 2h~4h;

[0040] (4) The α-MoO3 powder is heat-treated in a reducing atmosphere and then cooled to ≤80℃ for surface passivation treatment to obtain the ultra-high purity molybdenum powder.

[0041] The heat treatment includes: firstly, a first reduction is carried out at a temperature of 420℃~480℃ for 1h~3h, then a second reduction is carried out at a temperature of 620℃~680℃ for 1h~3h, and finally a third reduction is carried out at a temperature of 980℃~1050℃ for 1h~3h.

[0042] The surface passivation treatment includes: passivation in an argon-oxygen mixture with an oxygen volume fraction of 0.5% to 2% for 30 to 60 minutes.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The method for preparing ultra-high purity molybdenum powder provided by this invention first involves dissolving molybdenum-containing raw materials with hydrogen peroxide. Utilizing the difference in solubility between molybdenum and refractory metal impurities, most of the refractory impurities are filtered and separated in solid form, significantly reducing the subsequent impurity removal load from the source. Subsequently, the pH of the resulting crude permolybdic acid solution is adjusted to 2-4 for hydrolysis precipitation. A complexing agent is then added to mask residual impurities, and deep purification is achieved through resin adsorption and membrane filtration to obtain a high-purity permolybdic acid solution. This solution is concentrated and crystallized under reduced pressure at ≤60℃, and then dried and calcined in an oxygen-containing atmosphere to prepare an α-MoO3 precursor, effectively avoiding impurity encapsulation and external contamination. Finally, the precursor undergoes stepwise heat treatment and surface passivation treatment under a reducing atmosphere to further remove trace impurities, yielding ultra-high purity molybdenum powder. This invention features simple steps, strong impurity control, and is suitable for industrial production of 4N-5N grade ultra-high purity molybdenum powder. Detailed Implementation

[0045] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0046] The "range" disclosed in this invention 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 the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning 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 specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​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 invention, 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.

[0047] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0048] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0049] The term "embodiment" as used in this invention 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 the invention. 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 invention can be combined with other embodiments.

[0050] 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 the present invention 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.

[0051] In this invention, open-ended technical features or solutions described using 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, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed 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."

[0052] In this invention, 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.

[0053] This invention provides a method for preparing ultra-high purity molybdenum powder, the method comprising the following steps:

[0054] (1) Dissolve the molybdenum-containing raw material with hydrogen peroxide, filter to remove solid residue, and obtain crude permolybdic acid solution;

[0055] (2) Adjust the pH of the crude permolybdic acid solution to 2-4, hydrolyze and precipitate, add a complexing agent; then perform resin adsorption and membrane filtration in sequence to obtain a refined permolybdic acid solution;

[0056] (3) The refined permolybdic acid solution is concentrated and crystallized under reduced pressure at ≤60℃, and then dried and calcined in an oxygen-containing atmosphere to obtain α-MoO3 powder;

[0057] (4) The α-MoO3 powder is subjected to heat treatment and surface passivation in a reducing atmosphere to obtain the ultra-high purity molybdenum powder.

[0058] This invention first dissolves molybdenum-containing raw materials with hydrogen peroxide. Utilizing the difference in solubility between molybdenum and refractory metal impurities, most of the refractory impurities are filtered and separated in solid form, significantly reducing the subsequent impurity removal load from the source. Subsequently, the pH of the resulting crude permolybdic acid solution is adjusted to 2-4 for hydrolysis precipitation. A complexing agent is then added to mask residual impurities, and deep purification is achieved through resin adsorption and membrane filtration to obtain a high-purity permolybdic acid solution. This solution is concentrated and crystallized under reduced pressure at ≤60℃, and then dried and calcined in an oxygen-containing atmosphere to prepare an α-MoO3 precursor, effectively avoiding impurity encapsulation and external contamination. Finally, the precursor undergoes stepwise heat treatment and surface passivation under a reducing atmosphere to further remove trace impurities, yielding ultra-high purity molybdenum powder. This invention features simple steps, strong impurity control, and is suitable for the industrial production of 4N-5N grade ultra-high purity molybdenum powder.

[0059] In some embodiments, the temperature at which the hydrogen peroxide dissolves the molybdenum-containing raw material is below 15°C, for example, it can be 5°C, 6°C, 8°C, 10°C, 12°C or 15°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] Dissolving hydrogen peroxide below 15°C utilizes the significant difference in reactivity between molybdenum and refractory metals such as tungsten, tantalum, and niobium in the peroxide system at low temperatures. This allows molybdenum to rapidly form soluble permolybdate complexes, while the refractory metals, due to their extremely slow reaction or inability to form stable complexes, are retained by the solid phase. This achieves highly efficient and selective separation while effectively inhibiting the ineffective self-decomposition of hydrogen peroxide, ensuring reagent utilization and process safety.

[0061] In some embodiments, the molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 2.5:1 to 4:1, for example, it can be 2.5:1, 3:1, 3.5:1 or 4:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0062] In some embodiments, the molybdenum-containing raw material includes molybdenum powder and / or molybdenum trioxide.

[0063] In some embodiments, in step (2), the pH of the crude permolybdic acid solution is adjusted to 2 to 4 using nitric acid or ammonia. For example, it can be 2, 2.5, 3, 3.5 or 4, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] Controlling the pH of the crude permolybdate solution to 2-4 serves two purposes: firstly, it utilizes the weakly acidic environment to promote the hydrolysis of common metallic impurities such as iron and aluminum, forming precipitates that are then removed; secondly, it ensures that molybdenum remains in the stable permolybdate ion form without precipitation, while simultaneously providing optimal ion exchange conditions for subsequent complexing agent masking and resin adsorption.

[0065] In some embodiments, the complexing agent comprises fluoride and / or tartaric acid;

[0066] When the complexing agent is a fluoride, the amount of complexing agent used is such that the concentration of fluoride ions in the system is 0.001 mol / L to 0.01 mol / L, for example, it can be 0.001 mol / L, 0.003 mol / L, 0.005 mol / L, 0.006 mol / L, 0.008 mol / L or 0.01 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] When the complexing agent is tartaric acid, the amount of complexing agent used is such that the concentration of tartaric acid in the system is 0.01 mol / L to 0.05 mol / L, for example, it can be 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L or 0.05 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] In some embodiments, the fluoride includes any one or a combination of at least two of potassium fluoride, sodium fluoride, or ammonium fluoride. Typical but non-limiting combinations include combinations of potassium fluoride and sodium fluoride, combinations of sodium fluoride and ammonium fluoride, or combinations of potassium fluoride, sodium fluoride, and ammonium fluoride.

[0069] In some embodiments, the resin adsorption includes sequentially using a styrene-based strong basic anion exchange resin and an iminodiacetic acid type aminocarboxyl chelating resin for resin adsorption.

[0070] The membrane filtration includes filtration using ultrafiltration membranes and / or nanofiltration membranes.

[0071] In the pre-treatment styrene-based strong-base anion exchange resin, the strong-base quaternary ammonium groups primarily target residual trace impurities existing in anionic form for efficient ion exchange adsorption. The subsequent iminodiacetic acid-type aminocarboxylic acid chelating resin utilizes its chelating groups to chelate and remove trace cationic impurities that are difficult for the preceding anion exchange resin to capture. Membrane filtration is used to trap tiny colloidal particles and suspended solids that may penetrate the resin column or be generated during hydrolysis, ultimately ensuring the solution achieves extremely high purity.

[0072] In some embodiments, the drying temperature is 80°C to 120°C, for example, it can be 80°C, 90°C, 100°C, 110°C or 120°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] In some embodiments, the drying time is 1h to 2h, for example, it can be 1h, 1.2h, 1.5h, 1.6h, 1.8h or 2h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] In some embodiments, the calcination temperature is 380°C to 450°C, for example, 380°C, 400°C, 420°C, 440°C or 450°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0075] In some embodiments, the calcination time is 2h to 4h, for example, it can be 2h, 2.5h, 3h, 3.5h or 4h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0076] In some embodiments, the heat treatment includes: firstly, performing a first reduction at a temperature of 420°C to 480°C for 1 hour to 3 hours, then performing a second reduction at a temperature of 620°C to 680°C for 1 hour to 3 hours, and finally performing a third reduction at a temperature of 980°C to 1050°C for 1 hour to 3 hours.

[0077] The first reduction stage primarily removes adsorbed moisture and a small amount of volatile alkali metal impurities from the surface of molybdenum trioxide (MoO3), while initially reducing MoO3 to MoO2 to avoid localized sintering caused by direct high temperatures. The second reduction stage is the main reduction phase, where MoO2 is fully reduced to metallic molybdenum by hydrogen gas. Meanwhile, refractory metal oxides such as tungsten, tantalum, and niobium remain in their oxidized state and do not enter the molybdenum lattice due to their reduction temperatures being much higher than this range. The third reduction stage involves deep fine reduction and grain boundary purification. At this temperature, the molybdenum powder grains grow sufficiently, and residual impurities migrate to the grain boundaries and partially volatilize due to the decrease in solid solubility, ultimately reducing the total refractory metal impurities to below 0.5 ppm.

[0078] The first reduction temperature 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.

[0079] The second reduction temperature is 620℃~680℃, for example, it can be 620℃, 630℃, 640℃, 650℃, 660℃ or 680℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0080] The temperature for the third reduction is 980℃~1050℃, for example, it can be 980℃, 990℃, 1000℃, 1020℃, 1040℃ or 1050℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0081] The time for the first, second, and third reductions is independently 1 to 3 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0082] In some embodiments, the surface passivation treatment includes: passivating in an argon-oxygen mixture with an oxygen volume fraction of 0.5% to 2% (e.g., 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.6%, or 2%) for 30 to 60 minutes (e.g., 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes).

[0083] This invention utilizes surface passivation to form an extremely thin and dense oxide film on the surface of molybdenum powder, thereby preventing its violent reaction with the outside air and achieving safe and stable discharge and storage. Controlling the oxygen volume fraction within a low concentration range of 0.5% to 2% ensures that the passivation reaction proceeds slowly and uniformly under oxygen-deficient conditions. This avoids rapid and violent oxidation or even localized sintering of the molybdenum powder surface caused by high oxygen concentrations, which could result in an excessively thick, porous, or unevenly composed oxide film. Therefore, while ensuring the dust-proof effect of powder passivation, this invention maximizes the intrinsic purity and subsequent performance of the molybdenum powder.

[0084] As a preferred embodiment of the preparation method provided by the present invention, the preparation method includes the following steps:

[0085] (1) Hydrogen peroxide is used to dissolve molybdenum-containing raw materials at temperatures below 15°C, and the solid residue is removed by filtration to obtain a crude permolybdic acid solution;

[0086] The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 2.5:1 to 4:1;

[0087] The molybdenum-containing raw material includes molybdenum powder and / or molybdenum trioxide;

[0088] (2) Adjust the pH of the crude permolybdic acid solution to 2-4 using nitric acid or ammonia, hydrolyze and precipitate, add a complexing agent; then perform resin adsorption and membrane filtration in sequence to obtain a refined permolybdic acid solution.

[0089] The complexing agent includes fluoride and / or tartaric acid, wherein the fluoride includes any one or a combination of at least two of potassium fluoride, sodium fluoride, or ammonium fluoride; when the complexing agent is fluoride, the amount of complexing agent used is such that the concentration of fluoride ions in the system is 0.001 mol / L to 0.01 mol / L; when the complexing agent is tartaric acid, the amount of complexing agent used is such that the concentration of tartaric acid in the system is 0.01 mol / L to 0.05 mol / L.

[0090] The resin adsorption process includes sequentially using a styrene-based strong basic anion exchange resin and an iminodiacetic acid type aminocarboxyl chelating resin for resin adsorption.

[0091] The membrane filtration includes filtration using ultrafiltration membranes and / or nanofiltration membranes;

[0092] (3) The refined permolybdic acid solution is concentrated and crystallized under reduced pressure at ≤60℃, and then dried and calcined in an oxygen-containing atmosphere to obtain α-MoO3 powder;

[0093] The drying temperature is 80℃~120℃, and the time is 1h~2h;

[0094] The calcination temperature is 380℃~450℃, and the time is 2h~4h;

[0095] (4) The α-MoO3 powder is heat-treated in a reducing atmosphere and then cooled to ≤80℃ for surface passivation treatment to obtain the ultra-high purity molybdenum powder.

[0096] The heat treatment includes: firstly, a first reduction is carried out at a temperature of 420℃~480℃ for 1h~3h, then a second reduction is carried out at a temperature of 620℃~680℃ for 1h~3h, and finally a third reduction is carried out at a temperature of 980℃~1050℃ for 1h~3h.

[0097] The surface passivation treatment includes: passivation in an argon-oxygen mixture with an oxygen volume fraction of 0.5% to 2% for 30 to 60 minutes.

[0098] To clearly illustrate the technical solution of the present invention, in the following examples and comparative examples, the flow rate of resin adsorption was 2 BV / h, the styrene-based strong basic anion exchange resin was D201 type macroporous styrene-based strong basic anion exchange resin, and the iminodiacetic acid type aminocarboxylic acid chelating resin was D401 type iminodiacetic acid type aminocarboxylic acid chelating resin; the membrane filtration included first using a polyethersulfone hollow fiber ultrafiltration membrane with a molecular weight cutoff of 10 kDa to remove any possible colloidal particles, and then using a polyamide nanofiltration membrane with a molecular weight cutoff of 200 Da to remove residual low molecular weight organic matter and small particle ions.

[0099] Example 1

[0100] This embodiment provides a method for preparing ultra-high purity molybdenum powder, including the following steps:

[0101] (1) Hydrogen peroxide is dissolved in molybdenum-containing raw material (molybdenum powder) at a temperature of 15°C, and the solid residue is removed by filtration to obtain crude permolybdic acid solution;

[0102] The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 3:1;

[0103] (2) Adjust the pH of the crude permolybdic acid solution to 3, hydrolyze and precipitate, add a complexing agent; then perform resin adsorption and membrane filtration in sequence to obtain a refined permolybdic acid solution;

[0104] The complexing agent is sodium fluoride; the amount of complexing agent used is such that the concentration of fluoride ions in the system is 0.005 mol / L;

[0105] (3) The refined permolybdic acid solution is concentrated and crystallized under reduced pressure at 60°C, and then dried and calcined in air to obtain α-MoO3 powder;

[0106] The drying temperature is 100℃ and the time is 1.5h;

[0107] The calcination temperature was 400℃ and the time was 3 hours.

[0108] (4) The α-MoO3 powder is heat-treated in a reducing atmosphere and then cooled to 80°C for surface passivation treatment to obtain the ultra-high purity molybdenum powder.

[0109] The heat treatment includes: firstly, a first reduction at 450°C for 2 hours, then a second reduction at 650°C for 2 hours, and finally a third reduction at 1000°C for 2 hours.

[0110] The surface passivation treatment includes: passivation in an argon-oxygen mixture with an oxygen volume fraction of 1% for 45 minutes.

[0111] Example 2

[0112] This embodiment provides a method for preparing ultra-high purity molybdenum powder, including the following steps:

[0113] (1) Hydrogen peroxide is dissolved in molybdenum-containing raw material (molybdenum powder) at a temperature of 15°C, and the solid residue is removed by filtration to obtain crude permolybdic acid solution;

[0114] The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 2.5:1;

[0115] (2) Adjust the pH of the crude permolybdic acid solution to 2, hydrolyze and precipitate, add a complexing agent; then perform resin adsorption and membrane filtration in sequence to obtain a refined permolybdic acid solution;

[0116] The complexing agent is sodium fluoride; the amount of complexing agent used is such that the concentration of fluoride ions in the system is 0.001 mol / L;

[0117] (3) The refined permolybdic acid solution is concentrated and crystallized under reduced pressure at 60°C, and then dried and calcined in air to obtain α-MoO3 powder;

[0118] The drying temperature is 80℃ and the time is 2 hours;

[0119] The calcination temperature was 380℃ and the time was 4 hours.

[0120] (4) The α-MoO3 powder is heat-treated in a reducing atmosphere and then cooled to 80°C for surface passivation treatment to obtain the ultra-high purity molybdenum powder.

[0121] The heat treatment includes: firstly, a first reduction at 420°C for 3 hours, then a second reduction at 620°C for 3 hours, and finally a third reduction at 980°C for 3 hours.

[0122] The surface passivation treatment includes: passivation in an argon-oxygen mixture with an oxygen volume fraction of 0.5% for 60 minutes.

[0123] Example 3

[0124] This embodiment provides a method for preparing ultra-high purity molybdenum powder, including the following steps:

[0125] (1) Hydrogen peroxide is dissolved in molybdenum-containing raw material (molybdenum powder) at a temperature of 15°C, and the solid residue is removed by filtration to obtain crude permolybdic acid solution;

[0126] The molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 4:1;

[0127] (2) Adjust the pH of the crude permolybdic acid solution to 4, hydrolyze and precipitate, add a complexing agent; then perform resin adsorption and membrane filtration in sequence to obtain a refined permolybdic acid solution;

[0128] The complexing agent is sodium fluoride; the amount of complexing agent used is such that the concentration of fluoride ions in the system is 0.01 mol / L;

[0129] (3) The refined permolybdic acid solution is concentrated and crystallized under reduced pressure at 60°C, and then dried and calcined in air to obtain α-MoO3 powder;

[0130] The drying temperature is 120℃ and the time is 1 hour;

[0131] The calcination temperature was 450℃ and the time was 2 hours.

[0132] (4) The α-MoO3 powder is heat-treated in a reducing atmosphere and then cooled to 80°C for surface passivation treatment to obtain the ultra-high purity molybdenum powder.

[0133] The heat treatment includes: firstly, a first reduction at 480°C for 1 hour, then a second reduction at 680°C for 1 hour, and finally a third reduction at 1050°C for 1 hour.

[0134] The surface passivation treatment includes: passivation in an argon-oxygen mixture with an oxygen volume fraction of 2% for 30 minutes.

[0135] Example 4

[0136] This embodiment provides a method for preparing ultra-high purity molybdenum powder. Except that the complexing agent is tartaric acid and the amount of complexing agent is such that the concentration of tartaric acid in the system is 0.01 mol / L, everything else is the same as in Example 1.

[0137] Example 5

[0138] This embodiment provides a method for preparing ultra-high purity molybdenum powder. Except that the complexing agent is tartaric acid and the amount of complexing agent is such that the concentration of tartaric acid in the system is 0.05 mol / L, everything else is the same as in Example 1.

[0139] Example 6

[0140] 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.

[0141] Example 7

[0142] 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.

[0143] Example 8

[0144] 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.

[0145] Example 9

[0146] 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.

[0147] Example 10

[0148] 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.

[0149] Performance Characterization

[0150] The purity, total refractory metal impurity content, oxygen content, and Fisher particle size of the ultra-high purity molybdenum powder obtained in the above examples were determined, and the results are shown in Table 1.

[0151] Table 1

[0152]

[0153] As can be seen from Examples 1 to 3 in Table 1, the method for preparing ultra-high purity molybdenum powder provided by the present invention can stably produce ultra-high purity molybdenum powder with a purity ≥ 99.9990%, a total refractory metal impurity content as low as 0.00015%, an oxygen content controlled below 0.0007wt%, and a Fisher particle size in the range of 2.9~3.2μm. This indicates that the process has a strong ability to synergistically remove impurities within the preferred parameter range, and the product has high purity and controllable particle size.

[0154] A comparison of Examples 4 and 5 with Example 1 shows that the type of complexing agent affects the depth of removal of refractory metal impurities. When tartaric acid is used as the complexing agent, the final purity of molybdenum powder decreases slightly, while the total content of refractory metal impurities increases compared to when sodium fluoride is used.

[0155] 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 content of refractory metal impurities increases significantly, and the product purity decreases accordingly. 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.

[0156] A comparison of Examples 7 and 8 with Example 1 shows that when the first reduction step is omitted, the oxygen content increases and the Fisher particle size increases significantly; when the second reduction step is omitted, the increase in oxygen content is even greater. The low-temperature first reduction slowly transforms MoO3 into MoO2 and forms fine crystal nuclei; the medium-temperature second reduction further reduces MoO2 to metallic molybdenum while simultaneously deoxidizing a large amount; the high-temperature third reduction completes deep deoxidation and densification. The absence of any stage disrupts the reduction rhythm, leading to insufficient deoxidation and abnormal particle growth, resulting in a deterioration of both oxygen content and particle size.

[0157] A comparison of Examples 9 and 10 with Example 1 shows that the oxygen volume fraction during 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%), a complete and dense oxide film cannot be formed on the surface of the molybdenum powder, resulting in excessively high powder activity. This leads to oxygen adsorption during subsequent operations and storage, resulting in a high oxygen content. When the oxygen volume fraction is too high (3%), excessive oxidation occurs on the powder surface, forming an excessively thick oxide layer, directly causing a significant increase in the product's oxygen content. Only passivation in a mixed gas with a moderate oxygen content can an extremely thin and dense protective film be formed on the particle surface, maintaining the low-oxygen characteristics of ultra-high purity molybdenum powder while ensuring storage safety.

[0158] In summary, the method for preparing ultra-high purity molybdenum powder provided by this invention first involves dissolving molybdenum-containing raw materials with hydrogen peroxide. Utilizing the difference in solubility between molybdenum and refractory metal impurities, most of the refractory impurities are filtered and separated in solid form, significantly reducing the subsequent impurity removal load from the source. Subsequently, the pH of the obtained crude permolybdic acid solution is adjusted to 2-4 for hydrolysis precipitation. A complexing agent is then added to mask residual impurities, and deep purification is achieved through resin adsorption and membrane filtration to obtain a high-purity permolybdic acid solution. This solution is concentrated and crystallized under reduced pressure at ≤60℃, and then dried and calcined in an oxygen-containing atmosphere to prepare an α-MoO3 precursor, effectively avoiding impurity encapsulation and external contamination. Finally, the precursor undergoes stepwise heat treatment and surface passivation treatment under a reducing atmosphere to further remove trace impurities, yielding ultra-high purity molybdenum powder. This invention features simple steps, strong impurity control, and is suitable for industrial production of 4N-5N grade ultra-high purity molybdenum powder.

[0159] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention 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 technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing ultra-high purity molybdenum powder, characterized in that, The preparation method 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 2-4, hydrolyze and precipitate, add a complexing agent; then perform resin adsorption and membrane filtration in sequence to obtain a refined permolybdic acid solution; (3) The refined permolybdic acid solution is concentrated and crystallized under reduced pressure at ≤60℃, and then dried and calcined in an oxygen-containing atmosphere to obtain α-MoO3 powder; (4) The α-MoO3 powder is subjected to heat treatment and surface passivation in a reducing atmosphere to obtain the ultra-high purity molybdenum powder.

2. The preparation method according to claim 1, characterized in that, The temperature at which hydrogen peroxide dissolves molybdenum-containing raw materials is below 15°C; And / or, the molar ratio of hydrogen peroxide to molybdenum in the molybdenum-containing raw material is 2.5:1 to 4:1; And / or, the molybdenum-containing raw material includes molybdenum powder and / or molybdenum trioxide.

3. The preparation method according to claim 1 or 2, characterized in that, In step (2), the pH of the crude permolybdic acid solution is adjusted to 2-4 using nitric acid or ammonia.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The complexing agent includes fluorides and / or tartaric acid; When the complexing agent is a fluoride, the amount of complexing agent used is such that the concentration of fluoride ions in the system is 0.001 mol / L to 0.01 mol / L; When the complexing agent is tartaric acid, the amount of complexing agent used is such that the concentration of tartaric acid in the system is 0.01 mol / L to 0.05 mol / L.

5. The preparation method according to claim 4, characterized in that, The fluoride includes any one or a combination of at least two of potassium fluoride, sodium fluoride, or ammonium fluoride.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The resin adsorption process includes sequentially using a styrene-based strong basic anion exchange resin and an iminodiacetic acid type aminocarboxyl chelating resin for resin adsorption. The membrane filtration includes filtration using ultrafiltration membranes and / or nanofiltration membranes.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The drying temperature is 80℃~120℃; And / or, the drying time is 1h to 2h; And / or, the calcination temperature is 380℃~450℃; And / or, the calcination time is 2h~4h.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The heat treatment includes: firstly, 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.

9. The preparation method according to any one of claims 1 to 8, characterized in that, The surface passivation treatment includes: passivation in an argon-oxygen mixture with an oxygen volume fraction of 0.5% to 2% for 30 to 60 minutes.

10. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) Hydrogen peroxide is used to dissolve molybdenum-containing raw materials at temperatures below 15°C, and the solid residue is removed by filtration to obtain a 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 material includes molybdenum powder and / or molybdenum trioxide; (2) Adjust the pH of the crude permolybdic acid solution to 2-4 using nitric acid or ammonia, hydrolyze and precipitate, add a complexing agent; then perform resin adsorption and membrane filtration in sequence to obtain a refined permolybdic acid solution. The complexing agent includes fluoride and / or tartaric acid, wherein the fluoride includes any one or a combination of at least two of potassium fluoride, sodium fluoride, or ammonium fluoride; when the complexing agent is fluoride, the amount of complexing agent used is such that the concentration of fluoride ions in the system is 0.001 mol / L to 0.01 mol / L; when the complexing agent is tartaric acid, the amount of complexing agent used is such that the concentration of tartaric acid in the system is 0.01 mol / L to 0.05 mol / L. The resin adsorption process includes sequentially using a styrene-based strong basic anion exchange resin and an iminodiacetic acid type aminocarboxyl chelating resin for resin adsorption. The membrane filtration includes filtration using ultrafiltration membranes and / or nanofiltration membranes; (3) The refined permolybdic acid solution is concentrated and crystallized under reduced pressure at ≤60℃, and then dried and calcined in an oxygen-containing atmosphere to obtain α-MoO3 powder; 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 α-MoO3 powder is heat-treated in a reducing atmosphere and then cooled to ≤80℃ for surface passivation treatment to obtain the ultra-high purity molybdenum powder. The heat treatment includes: firstly, a first reduction is carried out at a temperature of 420℃~480℃ for 1h~3h, then a second reduction is carried out at a temperature of 620℃~680℃ for 1h~3h, and finally a third reduction is carried out at a temperature of 980℃~1050℃ for 1h~3h. The surface passivation treatment includes: passivation in an argon-oxygen mixture with an oxygen volume fraction of 0.5% to 2% for 30 to 60 minutes.

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