High-purity rhenium powder based on polyol thermal reduction and a method for preparing the same

Abstract

The application discloses a kind of high-purity rhenium powder based on polyol thermal reduction and preparation method thereof, belong to the technical field of rhenium powder preparation method.The preparation method includes: at 60-100 DEG C, to the aqueous solution of high-purity ammonium rhenium, add polyol, control the molar ratio of polyol and rhenium (4-10):1, reaction obtains modified precursor solution;Modified precursor solution is carried out spray drying, after which in inert atmosphere and / or hydrogen, at 700-1100 DEG C, carbon thermal in-situ reduction is obtained high-purity rhenium powder.The application preparation period is short, preparation condition is mild, and high-purity rhenium powder of high efficiency fast can be obtained with high dispersibility, particle size is uniform.

Description

Technical Field

[0001] This invention relates to the technical field of rhenium powder preparation methods, and particularly to a high-purity rhenium powder based on the thermal reduction of polyols and its preparation method. Background Technology

[0002] Rhenium (Re) is a scarce strategic refractory metal with a high melting point (3180℃), high density, and excellent corrosion resistance. High-purity rhenium powder is a key raw material for preparing rhenium metal billets, high-temperature alloy additives, petroleum reforming catalysts, and electron emission materials. With the rapid development of technology, the quality requirements for rhenium powder are constantly increasing, with the highest requirements being purity and particle size. The purity needs to reach 5N grade (99.999%) or higher, i.e., high-purity rhenium powder, to avoid grain boundary embrittlement caused by impurities; the particle size must be fine and uniformly distributed to improve the density and mechanical properties of subsequent molding processes (such as isostatic pressing and 3D printing).

[0003] Currently, the main industrial method for preparing high-purity rhenium powder is the hydrogen reduction method. This method uses hydrogen gas as a reducing agent to reduce rhenium oxides or ammonium salts to elemental metal at high temperatures. Its typical process flow usually includes the following two independent stages: Pretreatment stage: Industrial-grade ammonium perrylate (NH4ReO4) is mechanically crushed, ground, and sieved to increase the reaction contact area; Reduction stage: The pre-treated material is loaded into a boat and sent into a tube furnace or pusher furnace to undergo reduction treatment under a hydrogen atmosphere, finally obtaining rhenium metal powder.

[0004] This method has a long process and is prone to introducing impurities during preparation, which leads to a decrease in product purity. At the same time, as shown in the prior art CN119407185A, the reduction process in the reduction stage often adopts a high-temperature gradient reduction method. The rhenium powder is loaded in a boat in a high-temperature zone and placed statically for a long time, which easily leads to grain growth and sintering agglomeration.

[0005] To address the above issues, existing technologies have undergone certain improvements. For example, CN115026297A proposes a spray reduction process for preparing high-purity rhenium powder, which includes: dissolving primary rhenium products, purifying them through ion exchange to obtain high-purity perrhenic acid, and then feeding the perrhenic acid into a spray reactor (600~950℃) for hydrogen reduction to obtain high-purity rhenium powder. Although this technology has a short process and high purity, the rhenium powder particles are prone to agglomeration during the high-temperature hydrogen reduction process, and the particle morphology and particle size distribution are difficult to control precisely, often resulting in a poor particle size distribution that fails to meet the requirements of some high-end fields for ultrafine and uniform rhenium powder. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a novel continuous preparation method for high-purity rhenium powder. This method utilizes the reducing carbon environment generated by the pyrolysis of polyols and the micro-airflow generated by the decomposition of organic matter to create pores and disperse rhenium powder in situ. Simultaneously, external auxiliary heating is used to promote the reaction, thereby obtaining high-purity rhenium powder in one step.

[0007] The technical solution of the present invention is as follows: A method for preparing high-purity rhenium powder based on the thermal reduction of polyols, comprising the following steps: (1) Obtain an aqueous solution of high-purity ammonium perrylate; wherein the purity of the high-purity ammonium perrylate is ≥99.99%; (2) At 60-100℃, add a polyol to the aqueous solution of the high-purity ammonium rhenium, and control the molar ratio of the polyol to rhenium to be (4-10):1, and react to obtain a modified precursor solution; (3) The modified precursor solution is spray-dried to obtain precursor microsphere powder; (4) Under a carrier gas atmosphere, the precursor microsphere powder is heated to 700-1100℃ and carbothermic in-situ reduction is performed to obtain the high-purity rhenium powder; the carrier gas atmosphere is selected from an inert atmosphere and / or hydrogen.

[0008] The preparation method of the present invention can change the crystallization habit of ammonium permanganate and inhibit the excessively rapid growth of crystals in a certain direction by forming hydrogen bonds or complexes with the polyhydroxy structure of polyols and permanganate, thereby obtaining a precursor with uniform particle size. At the same time, the high boiling point of polyols (such as ethylene glycol, which can reach 197 °C) can provide a stable solvothermal environment during spray drying, delaying the dehydration and shrinkage process of permanganate oxides and enabling permanganate powder to complete nucleation and growth inside the solvent droplets, thereby obtaining solid spherical particles. In addition, at the high temperature of carbothermal in-situ reduction, the carbon layer formed by the carbonization of polyols can not only prevent particle sintering and agglomeration, but also participate in the reduction process as a carbon source, reducing the reduction activation energy of permanganate oxides in the precursor, changing the nucleation and growth mechanism of permanganate powder, solving the problem of uneven particle size in the traditional hydrogen reduction method, and based on the fact that the reduction potential of carbon is lower than that of hydrogen, the preparation temperature of permanganate powder can be significantly reduced (150-200 °C lower than the traditional process).

[0009] In the above preparation method of the present invention, the modified precursor solution is a transparent solution composed of ammonium perrylate and polyol; the precursor microspheres are mainly composed of ammonium perrylate, polyol, a small amount of rhenium oxide formed by pyrolysis, carbides, small aggregates or spheroids formed by polyol dehydration and adhesion of ammonium perrylate crystals or rhenium oxide during the drying process.

[0010] In the above preparation method of the present invention, the inventors unexpectedly discovered that controlling the molar ratio of polyol to rhenium to be (4-10):1 can achieve sufficient in-situ reduction (below 4:1 will lead to incomplete reduction and carbon residue), and can also avoid waste of reagents and obtain better product morphology.

[0011] According to some preferred embodiments of the present invention, the concentration of high-purity ammonium peroxide in the aqueous solution of the high-purity ammonium peroxide is 0.67-1.24 mol / L.

[0012] According to some preferred embodiments of the present invention, the particle size of the high-purity ammonium perrylate is 100-300 mesh.

[0013] According to some preferred embodiments of the present invention, the polyol is selected from one or more of ethylene glycol, glycerol, and polyethylene glycol.

[0014] More preferably, the polyol is selected from ethylene glycol and glycerol in a volume ratio of 1:1.

[0015] According to some preferred embodiments of the present invention, the reaction time in step (2) is 1-3 hours.

[0016] According to some preferred embodiments of the present invention, the carbothermic in-situ reduction time is 1-3 hours.

[0017] According to some preferred embodiments of the present invention, the spray drying adopts a centrifugal spray drying tower with an inlet temperature of 180-220°C and an outlet temperature of 80-120°C.

[0018] According to some preferred embodiments of the present invention, the carbothermic in-situ reduction is carried out in a jet reactor.

[0019] According to some preferred embodiments of the present invention, the flow rate of the inert atmosphere and / or hydrogen is 0.1-3 L / min.

[0020] According to some preferred embodiments of the present invention, the carrier gas atmosphere is selected from an inert atmosphere and has a flow rate of 1-3 L / min.

[0021] According to some preferred embodiments of the present invention, the carrier gas atmosphere is selected from hydrogen, and its flow rate is 0.1-1 L / min.

[0022] The present invention further provides high-purity rhenium powder prepared according to the above preparation method.

[0023] The high-purity rhenium powder is solid, spherical in shape, with uniform particle size and a loose packing density of 3.5-4.0 g / cm³. 50 The particle size is 1-5μm, the purity is ≥99.999%, and the impurity carbon content is <10ppm.

[0024] The present invention has the following beneficial effects: (1) The preparation method of the present invention utilizes the coordination effect of polyols to overcome the phenomenon of rapid solidification of particle surface leading to hollow interior in traditional spray drying, and obtains solid spherical or near-spherical rhenium powder particles, whose D 50 The particle size can be controlled within 2-5μm (suitable for 3D printing applications); at the same time, the spray granulation process based on the thermal reduction of polyols can ensure a consistent reaction environment within each microsphere, resulting in rhenium powder with an extremely narrow particle size distribution, no large particle inclusions, and highly uniform particle size; in addition, during the preparation process, the gas generated by the polyol can expand the rhenium powder particles at the microscale, effectively solving the problem of hard agglomeration of rhenium powder, making the powder loosely spherical or near-spherical with good flowability; (2) The preparation process of the present invention does not require physical powdering processes such as filtration and grinding, thus avoiding the introduction of impurities and dust hazards; the polyols used, such as ethylene glycol / glycerol, are non-toxic or low-toxic solvents, and the reaction process basically has no harmful gas emissions. The decomposition products are CO2 and so on, with no harmful residues, making it green and environmentally friendly. (3) In this invention, the polyol can not only provide a uniform reaction field, but also prepare rhenium powder with excellent monodispersity through its steric hindrance effect and reducing properties; at the same time, its reducing properties are relatively mild, avoiding the problem of excessively fast reaction and difficult morphology control caused by strong reducing agents (such as hydrazine hydrate), thus realizing precise morphology control of high-purity rhenium powder and obtaining products with stable and regular morphology. (4) The preparation method of the present invention can achieve in-situ reduction, which greatly reduces the dependence on external hydrogen, reduces hydrogen consumption, and reduces production costs. Attached Figure Description

[0025] Figure 1 Here is a SEM image of the rhenium powder prepared in Example 1; Figure 2 SEM image of the modified precursor powder microspheres prepared in Example 1; Figure 3 The image shows the SEM morphology of the rhenium powder prepared in Comparative Example 2. Detailed Implementation

[0026] The technical solutions of the present invention will be further described below with reference to the embodiments and accompanying drawings. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] In the following embodiments, the bulk density was determined by a Hall flow meter, the particle size was determined by a laser particle size analyzer, the impurity carbon content was determined by an infrared carbon-sulfur analyzer, and the purity was tested by glow discharge mass spectrometry (GDMS). In accordance with the nonferrous metal industry standard YS / T 1017-2015, 30 impurity elements involved were detected to obtain the purity of the main element Re.

[0028] Example 1 High-purity rhenium powder based on the thermal reduction of polyols was prepared by the following process: (1) Weigh 1000g of high-purity ammonium perrylate with a purity ≥99.99% and a particle size ≤75μm, dissolve it in 3L of deionized water, filter out the undissolved ammonium perrylate crystals, and obtain an ammonium perrylate solution with a rhenium concentration of about 1.11mol / L; (2) Take 1L of ammonium perrylate solution and place it in a 60℃ water bath and stir continuously. Slowly add a polyol solution consisting of 500mL of ethylene glycol (analytical grade) and 500mL of glycerol (analytical grade). Add a total of about 450mL of polyol solution to obtain a molar ratio of polyol to rhenium of about 6.5:1. After the addition is complete, continue stirring for 2 hours to obtain a dark brown transparent modified precursor solution. (3) The modified precursor solution is pumped into a centrifugal spray drying tower and spray dried at an inlet temperature of 200℃ and an outlet temperature of 100℃ to obtain loose precursor microsphere powder, as shown in the attached figure. Figure 2 As shown; (4) The precursor microsphere powder is fed into the jet reactor and nitrogen gas with a flow rate of 2L / min is introduced as the carrier gas. The furnace temperature is raised to 850℃ and the reaction is held for 1h. The precursor microspheres decompose in the furnace and are reduced in situ by carbothermal process to generate high-purity rhenium powder.

[0029] The obtained high-purity rhenium powder is a dark gray ultrafine powder, with solid spherical or near-spherical particles. The particles have a relatively regular morphology and show no obvious agglomeration. (See attached image.) Figure 1 As shown. Its loose bulk density was determined to be 3.8 g / cm³. 3 With a purity of 99.9992%, D 50 The size is 3.2 μm, and the impurity carbon content is less than 10 ppm.

[0030] Example 2 High-purity rhenium powder based on the thermal reduction of polyol was prepared using the same process as in Example 1, except that the amount of polyol added was adjusted to approximately 280 ml so that the molar ratio of polyol to rhenium was approximately 4:1.

[0031] The high-purity rhenium powder obtained in Example 2 was darker in color than that in Example 1, and SEM showed that its particles were solid spherical or near-spherical. Its loose bulk density was measured to be 2.8 g / cm³. 3 D 50The particle size is 5.1 μm, the impurity carbon content is 100 ppm, and the purity is 99.9872%.

[0032] Example 3 High-purity rhenium powder based on polyol thermal reduction was prepared using the same process as in Example 1, except that hydrogen gas with a flow rate of 0.5 L / min was used as the carrier gas in step (4).

[0033] SEM analysis showed that the obtained high-purity rhenium powder particles were solid spherical or near-spherical, slightly larger than the rhenium powder particles obtained in Example 1. The loose bulk density was measured to be 2.5 g / cm³. 3 D 50 The particle size is 4.0 μm, the impurity carbon content is less than 10 ppm, and the purity is 99.9965%.

[0034] The results showed that the rhenium powder particles obtained in Example 3 were slightly larger than those obtained in Example 1, but the reduction was more thorough, making them suitable for preparing dense rhenium bars.

[0035] Comparative Example 1 High-purity rhenium powder is prepared through the following process: (1) Weigh 1000g of high-purity ammonium perrylate and dissolve it in 3L of deionized water to obtain an ammonium perrylate solution with a perrylate concentration of about 1.11mol / L; (2) Pump the ammonium perrylate solution into a centrifugal spray drying tower and spray dry it at an inlet temperature of 200°C and an outlet temperature of 100°C to obtain loose ammonium perrylate crystalline powder. (3) The ammonium permanganate crystal powder is fed into the jet reactor and hydrogen gas with a flow rate of 0.5 L / min is introduced as the carrier gas. The furnace temperature is raised to 950℃ and the reaction is kept at the temperature for 1 hour. The ammonium permanganate decomposes in the furnace and is reduced by hydrogen to produce high-purity rhenium powder.

[0036] The obtained high-purity rhenium powder was a grayish-black powder. SEM showed that it was solid spherical or near-spherical, but the particle size varied, with a large number of irregular aggregates of 5-20 μm, and the particles were severely adhered to each other. Its loose bulk density was determined to be 2.2 g / cm³. 3 D 50 The particle size is 8.6 μm, the impurity carbon content is less than 10 ppm, and the purity is 99.993%.

[0037] The results showed that although the product of Comparative Example 1 had high purity, its particle size uniformity was poor, making it difficult to meet the needs of high-end applications.

[0038] Comparative Example 2 High-purity rhenium powder is prepared through the following process: (1) Slowly add a polyol solution consisting of 500 mL of ethylene glycol and 500 mL of glycerol to 300 g of high-purity ammonium perrylate powder, controlling the addition of about 450 mL of polyol solution to obtain a molar ratio of polyol to rhenium of 6.5:1. After the addition is complete, mechanically stir for 2 h, then heat to 100 °C and dry until completely dry to obtain white modified high-purity ammonium perrylate powder; (2) The modified high-purity ammonium rhenium powder was loaded into a pure molybdenum boat and placed in a tube furnace for two reductions. During the reduction process, nitrogen gas with a flow rate of 2L / min was introduced as the carrier gas. The first reduction temperature was 300℃ and the time was 6h; the second reduction temperature was 750℃ and the time was 4h; high-purity rhenium powder was obtained.

[0039] The obtained high-purity rhenium powder was a dark gray fine powder. SEM showed that it had a flaky and dendritic morphology (mainly flaky), with obvious local small agglomerations, as shown in the attached image. Figure 3 As shown. Its loose bulk density was determined to be 1.2 g / cm³. 3 D 50 The particle size is 25 μm, the impurity carbon content is less than 10 ppm, and the purity is 99.9983%.

[0040] The test results of the examples and comparative examples are shown in Table 1 below: Table 1 Detection Results of Examples Appearance spherical or near-spherical, solid spherical or near-spherical, solid spherical or near-spherical, solid spherical or near-spherical, solid flake-like, dendritic Loose packing density 3.8 g / cm³ 2.8 g / cm³ 2.5 g / cm³ 2.2 g / cm³ 1.2 g / cm³ <![CDATA[D 50 Particle size 3.2 μm 5.1 μm 4.0 μm 8.6 μm 25 μm Impurity content (C element) < 10 ppm 100 ppm < 10 ppm < 10 ppm < 10 ppm Purity Re (%) 99.9992% 99.9872% 99.9965% 99.993% 99.9983% It should be noted that the above descriptions are merely preferred embodiments of the present invention and should not limit the scope of protection of the technical solutions of the present invention. Any modifications made to the technical solutions described in the foregoing embodiments, or equivalent substitutions of technical features, by those skilled in the art within the spirit and principles of the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity rhenium powder based on the thermal reduction of polyols, characterized in that, It includes the following steps: (1) Obtain an aqueous solution of high-purity ammonium perrylate; wherein the purity of the high-purity ammonium perrylate is ≥99.99%; (2) At 60-100℃, add a polyol to the aqueous solution of the high-purity ammonium rhenium, and control the molar ratio of the polyol to rhenium to be (4-10):1, and react to obtain a modified precursor solution; (3) The modified precursor solution is spray-dried to obtain precursor microsphere powder; (4) Under a carrier gas atmosphere, the precursor microsphere powder is heated to 700-1100℃ and carbothermic in-situ reduction is performed to obtain the high-purity rhenium powder; the carrier gas atmosphere is selected from an inert atmosphere and / or hydrogen.

2. The preparation method according to claim 1, characterized in that, in, The concentration of the high-purity ammonium peroxide in the aqueous solution is 0.67-1.24 mol / L; and / or the particle size of the high-purity ammonium peroxide is 100-300 mesh.

3. The preparation method according to claim 1, characterized in that, The polyol is selected from one or more of ethylene glycol, glycerol, and polyethylene glycol.

4. The preparation method according to claim 1, characterized in that, in, The reaction time in step (2) is 1-3 h; and / or the carbothermic in-situ reduction time is 1-3 h.

5. The preparation method according to claim 1, characterized in that, in, The spray drying is carried out in a centrifugal spray drying tower with an inlet temperature of 180-220℃ and an outlet temperature of 80-120℃; and / or, the carbothermic in-situ reduction is carried out in a spray reactor.

6. The preparation method according to claim 1, characterized in that, The flow rate of the inert atmosphere and / or hydrogen is 0.1-3 L / min.

7. The preparation method according to claim 1, characterized in that, The polyol is selected from ethylene glycol and glycerol in a volume ratio of 1:

1.

8. The preparation method according to claim 1, characterized in that, The carrier gas atmosphere is selected from an inert atmosphere, and its flow rate is 1-3 L / min.

9. The preparation method according to claim 1, characterized in that, The carrier gas atmosphere is selected from hydrogen, and its flow rate is 0.1-1 L / min.

10. A high-purity rhenium powder, characterized in that, It is prepared by the method according to any one of claims 1-9.

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