A clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide

Abstract

The present invention provides a clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide, comprising: reducing pure MoS3 in a closed rotary tube furnace; simultaneously introducing pure nitrogen and hydrogen into the closed rotary furnace tube from the discharge end to the feed end, with the hydrogen having a dew point of -30°C and an oxygen content of less than 0.1 ppm; exhaust gas being withdrawn from the feed end air pipe by negative pressure; three-zone furnace temperatures set at 500-600°C, 700-800°C, and 900-1000°C, respectively; and a reduction time of 20-85 minutes. Molybdenum powder with an oxygen content of less than 10 ppm and a purity of 99.99% is obtained. The present invention utilizes a wide range of raw materials, eliminates ammoniation, and utilizes green recycling for exhaust gas treatment. This method is both efficient and economical, with precisely controlled process parameters. The resulting molybdenum powder has a lower oxygen content than traditional methods, and all other quality indicators meet national standards and market requirements for deep processing.

Description

Technical Field

[0001] The invention belongs to the technical field of high-purity molybdenum powder preparation, and relates to a clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide. Background Art

[0002] Molybdenum and its alloys have the advantages of high melting point, high hardness, high strength, excellent wear resistance and thermal conductivity, small expansion coefficient, good corrosion resistance, good thermal shock resistance, good formability, small thermal neutron absorption cross section, and high long-lasting strength. They are widely used in steel, metal processing, aerospace, nuclear industry, electronics and electrical fields.

[0003] At present, industrial production mainly adopts traditional technology to prepare molybdenum powder. Generally, ammonium molybdate, molybdenum trioxide or molybdenum dioxide are used as raw materials in fixed bed or fluidized bed reduction equipment to produce metallic molybdenum powder through hydrogen reduction. The produced molybdenum powder has a particle size of micron level and is mainly used as raw material for pressing molybdenum materials and preparing other powder metallurgy products.

[0004] Molybdenum oxide hydrogen reduction method: ammonium molybdate - low temperature calcination (430 ° C) - molybdenum oxide ammonia reduction (540 ° C, H2: 0.3m 3 / h)-Molybdenum dioxide-primary ammonia reduction (940℃; H2:2.5m 3 Molybdenum powder is prepared by reducing MoO3 and MoO2 with hydrogen. The industrial process for reducing molybdenum oxide with hydrogen to produce molybdenum powder is mainly divided into three types: the MoO3 single-stage reduction method, the MoO3 two-stage reduction method, and the MoO2 single-stage reduction method. The specific preparation principles are as follows:

[0005] (1) MoO3 two-stage reduction method

[0006] MoO3+H2=MoO2+H2O

[0007] MoO2+2H2=Mo+2H2O

[0008] (2) MoO3 one-stage reduction method

[0009] MoO3+3H2=Mo+3H2O

[0010] (3) MoO2 one-stage reduction method

[0011] MoO2+2H2=Mo+2H2O

[0012] While the single-stage reduction method has a shorter process, the reduction process is difficult to control, resulting in coarse molybdenum powder of poor quality. This also reduces the density of the sintered compact, making it generally unsuitable for processing molybdenum wire. The two-stage reduction method, on the other hand, is easier to control and produces fine molybdenum powder, but suffers from long processes, time-consuming processes, and complex equipment. Whether it's molybdenum trioxide or molybdenum dioxide, the raw material is ammonium molybdate. The production of ammonium molybdate requires the following steps: ammonia leaching of molybdenum roasted sand - filtration - decontamination of the ammonium molybdate solution with ammonia sulfide - filtration - filtrate concentration - acid precipitation - ammonia dissolution - evaporation (neutralization) - filtration - washing - drying - and finally ammonium molybdate. The production process for preparing various ammonium molybdates is long and suffers from high energy consumption, a single raw material, complex operations, and low recovery rates. This results in a long molybdenum powder production cycle, slow cash flow, and high production costs. Furthermore, the quality of the produced molybdenum powder suffers from high oxygen content.

[0013] Ammonium molybdate hydrogen reduction method: Ammonium molybdate can be calcined at 500-600°C to produce MoO₃. Alternatively, it can be reduced in a hydrogen atmosphere at 450-650°C and 800-900°C to produce gray molybdenum powder. This powder is free of agglomerates and metallic inclusions, but exhibits coarse, needle-like and flake-like particle shapes. Alternatively, a two-step method (also known as the single-step reduction method) is used to produce molybdenum powder. This method combines calcination with a first-step reduction at a temperature of 500-600°C to produce MoO₃ powder. The temperature is then raised to above 1100°C and held for a specified period to produce molybdenum powder. Compared to the double-step reduction method, this method simplifies the production process, resulting in comparable molybdenum powder purity and particle shape. However, the resulting molybdenum powder particles are coarser, resulting in a lower density in the sintered compact. Therefore, this method is generally not used in industrial production. The preparation of molybdenum chloride as a raw material is not suitable for industrial production due to the use of chlorine. The preparation of molybdenum hydroxylate as a raw material requires more stringent conditions, and reports of its industrial production are rare. Summary of the Invention

[0014] In response to the above technical problems, the purpose of the present invention is to provide a clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide, which has wide raw material adaptability, no ammonia production, and uses recycling for tail gas treatment, which is both efficient and economical.

[0015] The technical solution adopted by the present invention to achieve the technical purpose is:

[0016] A clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide, comprising:

[0017] Pure MoS3 is reduced in a closed rotary tube furnace, and pure nitrogen and hydrogen are simultaneously introduced into the closed rotary furnace tube from the discharge end to the feed end. The hydrogen dew point is -30°C and the oxygen content is less than 0.1ppm. The tail gas is extracted from the feed end air pipe through negative pressure. The three-zone furnace temperature is set at 500-600°C, 700-800°C, and 900-1000°C, respectively. The reduction time is 20-85min, and molybdenum powder with an oxygen content of less than 10ppm and a purity of 99.99% is obtained.

[0018] Preferably, the reaction in the above method comprises:

[0019] MoS3+H2=MoS2+H2S

[0020] MoS2+2H2=Mo+2H2S

[0021] MoS3+3H2=Mo+3H2S.

[0022] Preferably, the purity of pure MoS3 is ≥99.995%.

[0023] Preferably, the purity of the pure nitrogen and hydrogen is ≥99.99%.

[0024] Preferably, the hydrogen flow rate is 2.5 to 5 m 3 / h, nitrogen flow rate 0.8~1.8m 3 / h.

[0025] Preferably, pure MoS3 is prepared by the following method:

[0026] 1) adjusting the pH of a crude sodium molybdate solution to 11-13, heating the solution to 60-90° C., adding calcium molybdate to the solution at a liquid-to-solid ratio of 10:1-1000:1, stirring the solution for 1-5 hours, and filtering the solution to obtain a filtrate;

[0027] 2) introducing H2S into the sodium molybdate filtrate obtained in step 1) until the solution has a pH of 10, stirring for 1 to 5 hours, and filtering to obtain a pure sodium molybdate solution; adjusting the pH value of the pure sodium molybdate solution to 6.5 to 8, stirring the solution, and heating to 40 to 60°C after the pH value is qualified, introducing H2S into the solution until the residual S in the solution is 1. 2- The mass concentration is 0.5-4 g / l. After stirring and reacting for 1-5 hours, the pH value is adjusted to 2.5-3 again. After the pH value meets the requirements, it is immediately filtered and the solid obtained by washing and filtering is washed until the pH of the effluent is 6.5-7.0 to obtain pure MoS3.

[0028] Preferably, in step 1), the Mo concentration in the crude sodium molybdate solution is 20-200 g / l, more preferably 50-130 g / l.

[0029] Preferably, in step 2), the pH value of the purified sodium molybdate solution is adjusted to 6.5-8 with an inorganic acid, and the inorganic acid is selected from one of hydrochloric acid and sulfuric acid.

[0030] Preferably, in step 2), the solid obtained by filtration is washed with water without saline at a temperature below 15°C.

[0031] Preferably, in step 2), the Mo concentration in the filtrate is lower than 50 mg / l.

[0032] Preferably, the above method further comprises: collecting the H2S collected from the tail gas, washing it with water to remove soluble components, then passing it through a water separator and into a dryer to remove residual moisture, and returning it to the molybdenum trisulfide preparation process for recycling.

[0033] The beneficial effects of the present invention are:

[0034] This invention uses molybdenum trisulfide as a raw material to develop a molybdenum powder preparation process that features a short process, rapid cash flow, high recovery rate, low production cost, simple operation, and stable quality. Through nitrogen-protected hydrogen reduction, the molybdenum powder product is produced for pressing molybdenum materials and manufacturing other powder metallurgy products. This process has a wide range of raw material adaptability, does not require ammonia production, and utilizes a green recycling approach for tail gas treatment. It is both efficient and economical, with precise control of process parameters. The resulting molybdenum powder has a lower oxygen content than traditional methods, and all other quality indicators meet national standards and market requirements for further processing. DETAILED DESCRIPTION

[0035] In order to illustrate the present invention more clearly, the present invention is further described in detail below in conjunction with Examples. It should be understood by those skilled in the art that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0036] Example 1

[0037] The implementation of the technical solution of this embodiment mainly includes:

[0038] 1. Preparation of pure molybdenum trisulfide

[0039] (1) Using crude sodium molybdate solution as raw material, the solution Mo concentration is 50.76 g / l. The pH of the crude sodium molybdate solution is adjusted to 11 using NaOH and heated to 70°C. Depending on the impurity content, industrial-grade calcium molybdate is added to the sodium molybdate solution at a liquid-to-solid mass ratio of 1000:1. The mixture is stirred for 5 hours and filtered to obtain a filtrate. The impurity contents of P, As, Si, W, V, and C in the filtrate are all less than 10 mg / l.

[0040] (2) introducing H2S into the sodium molybdate filtrate with a pH value of 11 until the solution has a pH value of about 10, stirring for 1.5 hours, and filtering to obtain a pure sodium molybdate solution; adjusting the pH value of the sodium molybdate solution after impurities removal to 6.5 with hydrochloric acid, stirring the reaction until the pH value meets the requirements, heating to 50°C, and introducing H2S into the sodium molybdate solution until the residual S in the solution is reduced to 0. 2- The mass concentration was 0.58 g / l. After stirring for 1 hour, the pH value was adjusted to 2.5 by adding hydrochloric acid again. After the pH value met the requirements, it was immediately filtered and the filtered solid was washed with salt water at a temperature below 15°C until the pH of the effluent was 6.5 to obtain pure MoS3. The Mo concentration in the filtrate was 36.9 mg / l, and the molybdenum conversion rate was 99.68%.

[0041] 2. Preparation of Mo powder by hydrogen reduction

[0042] The pure MoS3 product is reduced in a closed rotary tube furnace. The rotary furnace tube adopts a quartz liner. Pure nitrogen and hydrogen (purity ≥ 99.99%) are introduced into the closed rotary furnace tube from the discharge end to the feed end. The hydrogen dew point is -30℃ and the oxygen content is less than 0.1ppm. The tail gas is extracted from the feed end gas pipe by negative pressure. The three zone furnace temperatures are set at 500℃, 700℃, and 900℃ respectively. The hydrogen flow rate is 2.5m 3 / h, nitrogen flow rate 0.8m 3 / h, reduction time 85min, to obtain molybdenum powder with oxygen content less than 10ppm and purity of 99.992%.

[0043] 3. Exhaust Gas Circulation

[0044] The H2S collected from the tail gas is collected and washed with water to remove the soluble components, then passes through a water separator and enters a dryer to remove residual moisture, and then returns to the molybdenum trisulfide preparation process for recycling.

[0045] Example 2

[0046] The implementation of the technical solution of this embodiment mainly includes:

[0047] 1. Preparation of pure molybdenum trisulfide

[0048] (1) Using crude sodium molybdate solution as raw material, the solution Mo concentration is 125.31 g / l. The pH of the crude sodium molybdate solution is adjusted to 13 using NaOH and heated to 80°C. Depending on the impurity content, industrial-grade calcium molybdate is added to the sodium molybdate solution at a liquid-to-solid mass ratio of 10:1. The mixture is stirred for 1 hour and filtered to obtain a filtrate. The impurity content of P, As, Si, W, V, C, etc. in the filtrate is less than 10 mg / l.

[0049] (2) introducing H2S into the sodium molybdate filtrate with a pH value of 13 until the solution has a pH value of about 10, stirring for 5 hours, and filtering to obtain a pure sodium molybdate solution; adjusting the pH value of the sodium molybdate solution after impurity removal to 8 with sulfuric acid, stirring the reaction until the pH value meets the requirements, heating to 45°C, and introducing H2S into the sodium molybdate solution until the residual S in the solution is 1%. 2- The mass concentration was 2 g / l. After stirring for 5 hours, the pH value was adjusted to 3 again by adding sulfuric acid. After the pH value met the requirements, it was immediately filtered and the filtered solid was washed with salt water at a temperature below 15°C until the pH of the effluent was 7.0 to obtain pure MoS3. The Mo concentration in the filtrate was 25.1 mg / l, and the molybdenum conversion rate was 99.79%.

[0050] 2. Preparation of Mo powder by hydrogen reduction

[0051] The pure MoS3 product is reduced in a closed rotary tube furnace. The rotary furnace tube adopts a quartz liner. Pure nitrogen and hydrogen (purity ≥ 99.99%) are introduced into the closed rotary furnace tube from the discharge end to the feed end. The hydrogen dew point is -30℃ and the oxygen content is less than 0.1ppm. The tail gas is extracted from the feed end gas pipe by negative pressure. The three zone furnace temperatures are set at 600℃, 800℃, and 1000℃ respectively. The hydrogen flow rate is 5m 3 / h, nitrogen flow rate 1.8m 3 / h, reduction time 25min, to obtain molybdenum powder with oxygen content less than 10ppm and purity of 99.993%.

[0052] 3. Exhaust Gas Circulation

[0053] The H2S collected from the tail gas is collected and washed with water to remove the soluble components, then passes through a water separator and enters a dryer to remove residual moisture, and then returns to the molybdenum trisulfide preparation process for recycling.

[0054] Example 3

[0055] The implementation of the technical solution of this embodiment mainly includes:

[0056] 1. Preparation of pure molybdenum trisulfide

[0057] (1) Using crude sodium molybdate solution as raw material, the solution has a Mo concentration of 98.82 g / L. Adjust the pH of the crude sodium molybdate solution to 12 using hydrochloric acid (or other common inorganic acids), heat to 90°C, and add industrial-grade calcium molybdate to the sodium molybdate solution at a liquid-to-solid mass ratio of 100:1, depending on the impurity content. Stir and react for 3 hours, then filter to obtain a filtrate. The impurity contents of P, As, Si, W, V, and C in the filtrate are all less than 10 mg / L.

[0058] (2) introducing H2S into the sodium molybdate filtrate with a pH value of 12 until the solution has a pH value of about 10, stirring for 3 hours, and filtering to obtain a pure sodium molybdate solution; adjusting the pH value of the sodium molybdate solution after impurity removal to 7 with hydrochloric acid, stirring the reaction until the pH value meets the requirements, heating to 60°C, and introducing H2S into the sodium molybdate solution until the residual S in the solution is 1%. 2- The mass concentration is 3.8 g / l. After stirring and reacting for 4 hours, the pH value is adjusted to 3 again by adding hydrochloric acid. After the pH value meets the requirements, it is immediately filtered and the filtered solid is washed with salt water at a temperature below 15°C until the pH of the effluent is 7.0 to obtain pure MoS3. The Mo concentration in the filtrate is 15.7 mg / l, and the molybdenum conversion rate is higher than 99.89%.

[0059] 2. Preparation of Mo powder by hydrogen reduction

[0060] The pure MoS3 product is reduced in a closed rotary tube furnace. The rotary furnace tube adopts a quartz liner. Pure nitrogen and hydrogen (purity ≥ 99.99%) are introduced into the closed rotary furnace tube from the discharge end to the feed end. The hydrogen dew point is -30℃ and the oxygen content is less than 0.1ppm. The tail gas is extracted from the feed end air pipe by negative pressure. The three zone furnace temperatures are set at 550℃, 750℃, and 950℃ respectively. The hydrogen flow rate is 3m 3 / h, nitrogen flow rate 1m 3 / h, reduction time 60min, to obtain molybdenum powder with oxygen content less than 10ppm and purity of 99.995%.

[0061] 3. Exhaust Gas Circulation

[0062] The H2S collected from the tail gas is collected and washed with water to remove the soluble components, then passes through a water separator and enters a dryer to remove residual moisture, and then returns to the molybdenum trisulfide preparation process for recycling.

[0063] It is understandable that the pure molybdenum trisulfide raw material used in the present invention can also include high-purity MoS3 prepared by any other raw materials and methods, and is not limited to the raw materials and preparation methods in the above embodiments.

[0064] Obviously, the above embodiments of the present invention are merely examples to more clearly illustrate the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to enumerate all implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide, comprising: Pure MoS3 is reduced in a closed rotary tube furnace. Pure nitrogen and hydrogen are introduced simultaneously from the discharge end to the feed end of the closed rotary tube furnace. The hydrogen flow rate is 2.5~5m 3 / h, nitrogen flow rate 0.8~1.8m 3 / h, hydrogen dew point -30℃ oxygen content less than 0.1ppm, tail gas is extracted from the feed end gas pipe by negative pressure, three-zone furnace temperature is set at 500~600℃, 700~800℃, 900~1000℃, reduction time is 20~85min, and the oxygen content is less than 10ppm and the purity of molybdenum powder with 99.99% purity is obtained; Pure MoS3 was prepared by the following method: 1) After adjusting the pH of the crude sodium molybdate solution to 11-13, heat it to 60-90°C, add calcium molybdate to the sodium molybdate solution at a liquid-to-solid mass ratio of 10:1-1000:1, stir and react for 1-5 hours, and filter to obtain a filtrate; 2) Add H2S to the sodium molybdate filtrate obtained in step 1) until the solution has a pH of 10, stir for 1 to 5 hours, and filter to obtain a pure sodium molybdate solution; adjust the pH value of the pure sodium molybdate solution to 6.5 to 8, stir and react until the pH value meets the requirements, heat to 40 to 60°C, and add H2S to the solution until the residual S in the solution is 10. 2- The mass concentration is 0.5-4 g / l. After stirring for 1-5 hours, the pH value is adjusted to 2.5-3 again. After the pH value meets the requirements, it is immediately filtered and the solid obtained by washing and filtering is washed to the pH of the effluent water of 6.5-7.0 to obtain pure MoS3; The reactions in the method include: MoS3+H2=MoS2+H2S MoS2+2H2=Mo+2H2S MoS3+3H2=Mo+3H2S; The H2S collected from the tail gas is collected and washed with water to remove the soluble components, then passes through a water separator and enters a dryer to remove residual moisture, and then returns to the molybdenum trisulfide preparation process for recycling.

2. A clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide according to claim 1, characterized in that: The purity of pure MoS3 is ≥99.995%.

3. A clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide according to claim 1, characterized in that: The purity of pure nitrogen and hydrogen is ≥99.99%.

4. A clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide according to claim 1, characterized in that, In step 1), the Mo concentration in the crude sodium molybdate solution is 20-200 g / l.

5. A clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide according to claim 1, characterized in that, In step 2), the pH value of the purified sodium molybdate solution is adjusted to 6.5-8 with an inorganic acid, wherein the inorganic acid is selected from hydrochloric acid and sulfuric acid.

6. A clean production method for preparing high-purity molybdenum powder from molybdenum trisulfide according to claim 1, characterized in that, In step 2), the solid obtained by filtration is washed with salt water at a temperature below 15° C.; the Mo concentration in the filtrate is less than 50 mg / l.