A method for preparing flake-shaped ammonium dimolybdate

Abstract

This invention belongs to the field of metallurgical technology and discloses a method for preparing flake-shaped ammonium dimolybdate. The method includes the following steps: (1) adjusting the pH of the ammonium molybdate solution to 0.5~1.5, then adding an oxidant for oxidation. After the reaction is complete, the solution is filtered, acid-washed, and dried to obtain molybdic acid; (2) mixing the ammonium source and the molybdic acid obtained in step (1) to obtain a mixture. The mixture is placed in a closed system for a one-step solid-phase conversion reaction at a reaction temperature of 110℃~150℃. After the reaction is complete, the product is removed, dried, and flake-shaped ammonium dimolybdate is obtained. This invention uses a one-step solid-phase ammonium conversion to produce ammonium dimolybdate, which can obtain large-size, flake-shaped ammonium dimolybdate products. This method has a high molybdenum conversion rate, is economical and environmentally friendly, has low energy consumption, low cost, is easy to operate, and has a short process.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology and relates to a method for preparing flake-shaped ammonium dimolybdate. Background Technology

[0002] Molybdenum is in high demand in both traditional and new energy sectors. Molybdenum and its alloys possess excellent thermal conductivity, electrical conductivity, high-temperature resistance, wear resistance, and corrosion resistance, making them widely used in steel metallurgy, chemical industry, energy, and machinery manufacturing, with broad development prospects. Ammonium molybdate is the most important intermediate material in the preparation of molybdenum metal products and molybdenum compounds, directly affecting the performance of subsequent molybdenum products.

[0003] Ammonium dimolybdate (AM) is a commonly used ammonium molybdate with the molecular formula (NH4)2Mo2O7. Currently, AM is widely used in dyes, pigments, catalysts, fire retardants, micronutrient fertilizers, ceramic colorants, and as a raw material for the synthesis of other compounds. AM has a profound impact on the production of molybdenum trioxide (MoO3), molybdenum powder, and their deep-processed products. According to feedback from domestic and international users, the morphology and particle size of AM is crucial to subsequent processing and product performance. For example, commonly used powdered AM forms irregular, chaotically distributed small particles during calcination, which may also contain fine particles, resulting in uneven particle size distribution and a higher impurity content in the MoO3 product. In contrast, regular, crystalline AM is less prone to breakage during calcination, resulting in smaller particle size variations, uniform distribution, clear grain boundaries, and high purity. Compared to powdered AM, large-crystal crystalline AM produces MoO3 with increased mass per unit volume during subsequent processing, facilitating transport and improving production efficiency. Furthermore, its chemical and structural advantages are more conducive to the production of high-performance deep-processed products.

[0004] Patent CN107043129A discloses a method for preparing ammonium dimolybdate, which involves a metathesis reaction of a molybdenum source and an ammonium source to obtain ammonium dimolybdate. However, this method cannot produce large-sized, flake-shaped ammonium dimolybdate. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to provide a method for preparing large-sized, sheet-like ammonium dimolybdate.

[0006] To achieve the objectives of this invention, the specific technical solution is as follows: A method for preparing flake-shaped ammonium dimolybdate includes the following steps: (1) Adjust the pH of the ammonium molybdate solution to 0.5~1.5, then add an oxidant to carry out the oxidation reaction. After the reaction is completed, filter, acid wash, and dry to obtain molybdic acid; (2) Take the ammonium source and the molybdenum acid obtained in step (1) and mix them to obtain a mixture. Place the mixture in a closed system to carry out a solid-phase one-step transformation reaction. The reaction temperature is 110℃~150℃. After the reaction is completed, take out the product, dry it, and obtain flake ammonium dimolybdate.

[0007] Further, in step (1), the mass concentration of the ammonium molybdate solution is 30~200g / L.

[0008] More preferably, molybdenum trioxide is mixed with ammonia water to obtain an ammonium molybdate solution.

[0009] More preferably, the mass ratio of molybdenum trioxide to ammonia is 1:0.40~0.45.

[0010] More preferably, the mass concentration of the ammonia water is 10~25g / L.

[0011] Further, in step (1), the pH value of the ammonium molybdate solution is adjusted to 0.9~1.1.

[0012] More preferably, in step (1), sulfuric acid is added to adjust the pH value of the ammonium molybdate solution.

[0013] More preferably, in step (1), the mass concentration of the sulfuric acid solution is 200~350g / L.

[0014] Further, in step (1), the solution after the oxidation reaction is completed is a white or pale yellow turbid solution. More preferably, an oxidant is added to carry out the oxidation reaction until no molybdenum blue is produced in the solution, which is a white or pale yellow turbid solution.

[0015] Further, the oxidant is hydrogen peroxide or nitric acid. More preferably, the hydrogen peroxide has a weight percentage of 3-5%. More preferably, the nitric acid has a concentration of 200-400 g / L.

[0016] Further, in step (1), after the reaction is completed, the reaction temperature is maintained for 20-40 minutes, filtered, acid-washed, and the acid-precipitated product is obtained. After drying, molybdic acid is obtained.

[0017] Further, in step (2), the ammonium source is at least one of ammonium carbonate, ammonium bicarbonate, and ammonia.

[0018] More preferably, in step (2): When ammonium bicarbonate is selected as the ammonium source, the molar ratio of molybdic acid to ammonium bicarbonate is 1:0.8~1.5, preferably 1:0.9~1.3, and most preferably 1:1; When ammonium carbonate is selected as the ammonium source, the molar ratio of molybdic acid to ammonium carbonate is 1.8~2.5:1, preferably 1.9~2.3:1, and most preferably 2:1; When ammonia is selected as the ammonium source, the molar ratio of molybdic acid to ammonia is 1:0.8~1.5, preferably 1:0.9~1.3, and most preferably 1:1; When the ammonium source is a mixture of ammonium bicarbonate and ammonium carbonate, the molar ratio of molybdic acid to ammonium bicarbonate and ammonium carbonate is 1:0.4~0.75:0.1~0.35, preferably 1:0.5~0.6:0.2~0.3; When the ammonium source is a mixture of ammonium bicarbonate and ammonia, the molar ratio of molybdic acid to ammonium bicarbonate and ammonia is 1:0.4~0.75:0.4~0.75, preferably 1:0.5~0.6:0.5~0.6; When the ammonium source is a mixture of ammonium carbonate and ammonia, the molar ratio of molybdic acid to ammonium carbonate and ammonia is 1:0.1~0.35:0.4~0.75, preferably 1:0.2~0.3:0.5~0.6; When the ammonium source is a mixture of ammonium bicarbonate, ammonium carbonate and ammonia, the molar ratio of molybdic acid to ammonium bicarbonate, ammonium carbonate and ammonia is 1:0.5~1.2:0.1~0.6:0.5~1.2, preferably 1:0.7~0.9:0.2~0.4:0.7~0.9.

[0019] Furthermore, in step (2), the reaction time is 120 min to 200 min.

[0020] Furthermore, in step (2), the mixture is placed in a low-pressure steel ball and then placed in a homogeneous reactor for a solid-phase one-step transformation reaction.

[0021] More preferably, the low-pressure steel bullet is provided with a polytetrafluoroethylene liner.

[0022] More preferably, the low-pressure steel bullet is preheated; the preheating parameters are set to a temperature of 50~100℃.

[0023] More preferably, after the solid-phase one-step transformation reaction is completed, the low-pressure steel bullet is cooled to room temperature, then the low-pressure steel bullet is dried, and the product on the low-pressure steel bullet is taken out for ultrasonic dispersion.

[0024] More preferably, the ultrasonic power is 30~60W and the ultrasonic frequency is 20~40KHz.

[0025] Furthermore, in step (2), the drying temperature is 40~200℃; the drying time is 2~10h.

[0026] Further, in step (2), after drying, the product is filtered through a vibrating screen of 150-400 mesh to obtain flake-shaped ammonium dimolybdate. Vibrating screen filtration can remove impurities and loose, uneven powder.

[0027] Furthermore, in step (2), after the reaction is complete, when the product is removed, an alkaline absorbent is used to recover the carbon dioxide in the product. This invention does not have special requirements regarding the concentration or amount of the alkaline absorbent; specifically, it only needs to be sufficient to ensure that all the generated CO2 gas is absorbed.

[0028] More preferably, the alkaline absorbent is ammonia or ammonium carbonate solution.

[0029] More preferably, the alkaline absorbent solution after absorbing carbon dioxide is returned to step (2) as an ammonium source.

[0030] Furthermore, an appropriate amount of water is added during the solid-phase one-step transformation reaction to provide a wetting state for the reaction and promote its progress. In this invention, the mass ratio of the molybdenum source to water is preferably 10:(0.25~1), more preferably 10:(0.5~0.75).

[0031] Furthermore, in step (2), the D50 of the obtained flake ammonium dimolybdate is 86.61 μm to 247.39 μm.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention adopts a one-step conversion / transformation of solid phase ammonium to generate ammonium dimolybdate, which can obtain large-size, flake-shaped ammonium dimolybdate products. This method has a high molybdenum conversion rate, is economical and environmentally friendly, has low energy consumption, low cost, is easy to operate, and has a short process.

[0033] (2) The process flow of the present invention is universal. By controlling the molar ratio of molybdenum and ammonium, temperature, reaction time and other conditions, large-sized, flake-shaped ammonium dimolybdate products with controllable morphology and particle size can be obtained. The produced ammonium dimolybdate particles have regular morphology and good uniformity in particle size and purity. Attached Figure Description

[0034] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a process flow diagram of the present invention.

[0035] Figure 2 The X-ray diffraction pattern of the product shown in Example 1 is shown.

[0036] Figure 3 The image shown is a scanning electron microscope (SEM) image of the product shown in Example 1.

[0037] Figure 4 The DSC and TGA curves of the product shown in Example 2 are shown.

[0038] Figure 5The image shows the scanning electron microscope (SEM) morphology of the product shown in Comparative Example 1.

[0039] Figure 6 The X-ray diffraction pattern of the product shown in Comparative Example 1 is shown. Detailed Implementation

[0040] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0041] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0042] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0043] Example 1 This embodiment provides a method for preparing sheet-like ammonium dimolybdate, such as... Figure 1 As shown, it includes the following steps: (1) Weigh 7.34 g of molybdenum trioxide and 3.26 ml of AR25%wt ammonia water and put them into a beaker placed on a heating plate. Add 50 ml of deionized water and stir magnetically until it is completely dissolved and forms a clear and transparent solution. Then make up to 300 ml and slowly titrate it into a three-necked flask containing sulfuric acid at 250 g / L. Adjust the temperature to 75 °C and the stirring power to 350 rpm. Titrate until the pH endpoint is 1.0, keep warm for 15 min and stop stirring. Then wash with acid, filter and dry to obtain molybdic acid precursor. (2) Mix 2.50g of molybdate precursor and 1.14g of ammonium bicarbonate and load them into a low-pressure steel pellet. Place the mixture into a homogeneous reactor, turn on the temperature control and set the preheating temperature to 90℃. After preheating for 20min, set the reaction temperature to 100℃ and the stirring power to 15rpm. Seal the system and react for 120min. After the reaction is complete, place the low-pressure steel pellet in a cold water bath to cool to room temperature, and then transfer it to a 50℃ drying oven to dry for 60min. After removing the sample, place the ammonium molybdate in an ultrasonic chamber with a power of 60W and a frequency of 25KHz for 10min. Then dry the product at 70℃ for 6h to obtain flaky, non-agglomerated ammonium dimolybdate crystals (NH4)2Mo2O7.

[0044] The X-ray diffraction pattern of the obtained sheet-like, non-agglomerated ammonium dimolybdate crystals is as follows: Figure 2 As shown in the scanning electron microscope (SEM) morphology images, Figure 3As shown in the figure. X-ray diffraction analysis revealed that the product contained a single phase, with a purity >99%. Furthermore, the microstructure consisted of plate-like, non-agglomerated ammonium dimolybdate crystals with a bulk density of 0.28 g / cm³. 3 The Fess particle size is 6.31 μm, and the D50 is 86.61 μm.

[0045] Example 2 This embodiment provides a method for preparing sheet-like ammonium dimolybdate, such as... Figure 1 As shown, it includes the following steps: (1) Weigh 8.15g of molybdenum trioxide and 3.6ml of AR25%wt ammonia water and put them into a beaker placed on a heating plate. Add 50ml of deionized water and stir magnetically until it is completely dissolved and forms a clear and transparent solution. Then make up to 100ml and slowly titrate it into a three-necked flask containing sulfuric acid at 250g / L. Adjust the temperature to 70℃ and the stirring power to 350rpm. Titrate until the pH endpoint is 1.06, keep warm for 20min and stop stirring. Then wash with acid, filter and dry to obtain molybdic acid precursor. (2) 2.00 g of molybdate precursor and 1.22 g of mixed ammonium source (molybdate and ammonium bicarbonate, with a molar ratio of ammonium carbonate of 1:0.5:0.2) were mixed and loaded into a low-pressure steel pellet, placed in a homogeneous reactor, and the temperature control was turned on and the preheating temperature was set to 90°C. After preheating for 20 min, the reaction temperature was set to 110°C and the stirring power was 12 rpm. The system was sealed and reacted for 140 min. After the reaction was completed, the low-pressure steel pellet was placed in a cold water bath to cool to room temperature, and then transferred to a 50°C drying oven to dry for 60 min. After taking out the sample, the ammonium molybdate was placed in an ultrasonic chamber with an ultrasonic power of 60 W and an ultrasonic frequency of 25 kHz for 5 min. Then the product was dried at 95°C for 2 h to obtain plate-like non-agglomerated ammonium dimolybdate crystals (NH4)2Mo2O7.

[0046] X-ray diffraction analysis revealed that the product contained a single phase, with a purity >99% and a bulk density of 0.51 g / cm³. 3 The Fess particle size is 13.77 μm, and the D50 is 151.31 μm. For example... Figure 4 As shown, its DSC and TGA curves indicate that the prepared ammonium dimolybdate has high purity and its crystal form meets the requirements of a single crystal.

[0047] Example 3 This embodiment provides a method for preparing sheet-like ammonium dimolybdate, such as... Figure 1 As shown, it includes the following steps: (1) Weigh 9.78g of molybdenum trioxide and 4.3ml of AR25%wt ammonia water and put them into a beaker placed on a heating plate. Add 40ml of deionized water and stir magnetically until it is completely dissolved and forms a clear and transparent solution. Then make up to 100ml and slowly titrate it into a three-necked flask containing sulfuric acid at 250g / L. Adjust the temperature to 73℃ and the stirring power to 400rpm. Titrate until the pH endpoint is 0.96, keep warm for 20min and stop stirring. Then wash with acid, filter and dry to obtain molybdic acid precursor. (2) 2.00 g of molybdate precursor and 1.22 g of mixed ammonium source (molybdate and ammonium bicarbonate in a molar ratio of 1:0.6:0.6) were mixed and loaded into a low-pressure steel ball, placed in a homogeneous reactor, and the temperature control was turned on and the preheating temperature was set to 90°C. After preheating for 20 min, the reaction temperature was set to 120°C and the stirring power was 12 rpm. The system was sealed and reacted for 160 min. After the reaction was completed, the low-pressure steel ball was placed in a cold water bath to cool to room temperature, and then transferred to a 50°C drying oven to dry for 60 min. After taking out the sample, the ammonium molybdate was placed in an ultrasonic chamber with an ultrasonic power of 60 W and an ultrasonic frequency of 25 kHz for 5 min. Then the product was dried at 95°C for 5 h to obtain flaky, non-agglomerated ammonium dimolybdate crystals (NH4)2Mo2O7.

[0048] X-ray diffraction analysis revealed that the product contained a single phase, with a purity >99% and a bulk density of 0.67 g / cm³. 3 The Fess particle size is 15.30 μm, and the D50 is 194.73 μm.

[0049] Example 4 This embodiment provides a method for preparing sheet-like ammonium dimolybdate, such as... Figure 1 As shown, it includes the following steps: (1) Weigh 9.78g of molybdenum trioxide and 4.3ml of AR25%wt ammonia water and put them into a beaker placed on a heating plate. Add 65ml of deionized water and stir magnetically until completely dissolved to form a clear and transparent solution. Then make up to 200ml and slowly titrate it into a three-necked flask containing sulfuric acid at 250g / L. Adjust the temperature to 73℃ and the stirring power to 400rpm. Titrate until the pH endpoint is 1.09, keep warm for 20min and stop stirring. Then wash with acid, filter and dry to obtain molybdic acid precursor. (2) 2.50 g of molybdate precursor and 1.38 g of mixed ammonium source (molar ratio of molybdate and ammonium bicarbonate, ammonium carbonate and ammonia water is 1:0.8:0.3:0.8) were mixed and loaded into a low-pressure steel ball, placed in a homogeneous reactor, and the temperature control was turned on and the preheating temperature was set to 85℃. After preheating for 25 min, the reaction temperature was set to 130℃ and the stirring power was 10 rpm. The system was sealed and reacted for 180 min. After the reaction was completed, the low-pressure steel ball was placed in a cold water bath to cool to room temperature, and then transferred to a 50℃ drying oven to dry for 60 min. After taking out the sample, the ammonium molybdate was placed in an ultrasonic chamber with an ultrasonic power of 60 W and an ultrasonic frequency of 25 kHz for 5 min. Then the product was dried at 55℃ for 3 h to obtain flaky non-agglomerated ammonium dimolybdate crystals (NH4)2Mo2O7.

[0050] X-ray diffraction analysis revealed that the product contained a single phase, with a purity >99% and a bulk density of 0.71 g / cm³. 3 The Fess particle size is 17.85 μm, and the D50 is 219.30 μm.

[0051] Example 5 This embodiment is basically the same as embodiment 1, except that: (2) Molybdic acid, ammonium bicarbonate and water were mixed evenly at a mass ratio of 10:4.6:0.2, loaded into a low-pressure steel ball, placed in a homogeneous reactor, and the temperature control was turned on and the preheating temperature was set to 90℃. After preheating for 20 min, the reaction temperature was set to 150℃ and the stirring power was 10 rpm. The system was sealed and reacted for 200 min. After the reaction was completed, the low-pressure steel ball was placed in a cold water bath to cool to room temperature, and then transferred to a 50℃ drying oven to dry for 60 min. After taking out the sample, ammonium molybdate was placed in an ultrasonic chamber with an ultrasonic power of 60W and an ultrasonic frequency of 25KHz for 10 min. Then the product was dried at 70℃ for 6 h to obtain flaky non-agglomerated ammonium dimolybdate crystals (NH4)2Mo2O7.

[0052] The X-ray diffraction analysis results showed that the product contained a single phase, the ammonium dimolybdate product purity was >99%, the bulk density was 0.78 g / cm3, the Fess particle size was 19.13 μm, and the D50 was 247.39 μm.

[0053] Comparative Example 1 This comparative example is basically the same as Example 1, except that: (2) Mix 2.50g of molybdate precursor and 1.14g of ammonium bicarbonate and load them into a low-pressure steel pellet. Place the pellet in a homogeneous reactor, set the reaction temperature to 70℃ and the stirring power to 15rpm, and seal the system for 30min. After the reaction, cool the low-pressure steel pellet in a cold water bath to room temperature, and then transfer it to a 50℃ drying oven for 45min. After removing the sample, place the ammonium molybdate in an ultrasonic chamber with a power of 60W and a frequency of 25KHz for 3min, and then dry the product at 55℃ for 6h to obtain blocky and flaky agglomerated ammonium molybdate crystals, such as... Figure 6 As shown, X-ray diffraction analysis results indicate that the product contains multiple ammonium molybdate components, which does not meet the industry standard for ammonium molybdate (GB / T 3460-2017). Figure 5 As shown in the figure, various types of ammonium polymolybdate exhibit strong agglomeration, multiple crystal forms, and uneven grain distribution.

[0054] Comparative Example 2 This comparative example is basically the same as Example 1, except that: (2) 2.50 g of molybdate precursor and 1.14 g of ammonium bicarbonate were mixed and loaded into a low-pressure steel pellet, placed in a homogeneous reactor, and the reaction temperature was set to 80 °C and the stirring power to 15 rpm. The system was sealed and reacted for 45 min. After the reaction was completed, the low-pressure steel pellet was placed in a cold water bath to cool to room temperature, and then transferred to a 50 °C drying oven to dry for 45 min. After the sample was taken out, the ammonium molybdate was placed in an ultrasonic chamber with an ultrasonic power of 60 W and an ultrasonic frequency of 25 kHz for 3 min. Then the product was dried at 55 °C for 6 h to obtain blocky and flaky agglomerated ammonium molybdate crystals. The X-ray diffraction analysis results showed that the phases present in the product contained multiple ammonium molybdate components, which did not meet the industry standard for ammonium molybdate (GB / T 3460-2017).

[0055] Comparative Example 3 This comparative example is basically the same as Example 1, except that: (2) Mix 2.50g of molybdate precursor and 1.14g of ammonium bicarbonate and load them into a low-pressure steel pellet. Place the pellet into a homogeneous reactor, set the reaction temperature to 90℃ and the stirring power to 15rpm, and seal the system for 6min. After the reaction, place the low-pressure steel pellet in a cold water bath to cool to room temperature, and then transfer it to a 50℃ drying oven to dry for 45min. After taking out the sample, place the ammonium molybdate in an ultrasonic chamber with an ultrasonic power of 60W and an ultrasonic frequency of 25KHz for 3min. Then dry the product at 55℃ for 6h to obtain blocky and flaky agglomerated ammonium molybdate crystals. The X-ray diffraction analysis results show that the phases present in the product contain multiple ammonium molybdate components, which do not meet the industry standard for ammonium molybdate (GB / T 3460-2017).

[0056] Comparative Example 4 This comparative example is basically the same as Example 1, except that: (2) Mix 2.50g of molybdate precursor and 1.14g of ammonium bicarbonate and load them into a low-pressure steel ball. Place the mixture into a homogeneous reactor, turn on the temperature control and set the preheating temperature to 90℃. After preheating for 20min, set the reaction temperature to 160℃ and the stirring power to 15rpm. Seal the system and react for 75min. After the reaction, place the low-pressure steel ball in a cold water bath to cool to room temperature, and then transfer it to a 50℃ drying oven to dry for 45min. After taking out the sample, place the ammonium molybdate in an ultrasonic chamber with an ultrasonic power of 60W and an ultrasonic frequency of 25KHz for 3min. Then dry the product at 55℃ for 6h to obtain blocky and flaky agglomerated ammonium molybdate crystals. The X-ray diffraction analysis results show that the phases present in the product contain multiple ammonium molybdate components, which do not meet the industry standard for ammonium molybdate (GB / T 3460-2017).

[0057] Comparative Example 5 This comparative example is basically the same as Example 1, except that: No step (1) is needed; industrial molybdic acid is used directly.

[0058] Comparative Example 5 used industrial molybdic acid, and the final product was analyzed. The X-ray diffraction analysis results showed that the product contained multiple ammonium molybdate phases and had multiple crystal forms in its microstructure.

[0059] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the present invention.

Claims

1. A method for preparing flake-shaped ammonium dimolybdate, characterized in that, Includes the following steps: (1) Adjust the pH of the ammonium molybdate solution to 0.9~1.1, then add an oxidant to carry out the oxidation reaction. After the reaction is completed, filter, acid wash, and dry to obtain molybdic acid; (2) Take the ammonium source and the molybdenum acid obtained in step (1) and mix them to obtain a mixture. Place the mixture in a closed system to carry out a solid-phase one-step transformation reaction. The reaction temperature is 110℃~150℃ and the reaction time is 120min~200min. After the reaction is completed, take out the product, dry it, and obtain flake ammonium dimolybdate. In step (1), the mass concentration of the ammonium molybdate solution is 30~200 g / L; molybdenum trioxide and ammonia water are mixed to obtain the ammonium molybdate solution; the mass ratio of molybdenum trioxide to ammonia water is 1:0.40~0.45; the mass concentration of the ammonia water is 10~25 g / L; sulfuric acid is added to adjust the pH value of the ammonium molybdate solution; the mass concentration of the sulfuric acid is 200~350 g / L; the oxidant is hydrogen peroxide solution or nitric acid solution. In step (2), the ammonium source is at least one of ammonium carbonate, ammonium bicarbonate, and ammonia. When ammonium bicarbonate is selected as the ammonium source, the molar ratio of molybdic acid to ammonium bicarbonate is 1:0.8~1.5; When ammonium carbonate is selected as the ammonium source, the molar ratio of molybdic acid to ammonium carbonate is 1.8~2.5∶1; When ammonia is used as the ammonium source, the molar ratio of molybdic acid to ammonia is 1:0.8~1.

5. When the ammonium source is a mixture of ammonium bicarbonate and ammonium carbonate, the molar ratio of molybdic acid to ammonium bicarbonate and ammonium carbonate is 1:0.4~0.75:0.1~0.35; When the ammonium source is a mixture of ammonium bicarbonate and ammonia, the molar ratio of molybdic acid to ammonium bicarbonate and ammonia is 1:0.4~0.75:0.4~0.75; When the ammonium source is a mixture of ammonium carbonate and ammonia, the molar ratio of molybdic acid to ammonium carbonate and ammonia is 1:0.1~0.35:0.4~0.75; When the ammonium source is a mixture of ammonium bicarbonate, ammonium carbonate, and ammonia, the molar ratio of molybdic acid to ammonium bicarbonate, ammonium carbonate, and ammonia is 1:0.5~1.2:0.1~0.6:0.5~1.

2.

2. The method for preparing flake-shaped ammonium dimolybdate as described in claim 1, characterized in that, In step (1), the hydrogen peroxide has a weight percentage of 3-5%; the nitric acid has a concentration of 200-400 g / L.

3. The method for preparing flake-shaped ammonium dimolybdate as described in claim 1 or 2, characterized in that, In step (1), after the reaction is completed, the reaction temperature is maintained for 20-40 minutes, filtered and acid-washed to obtain the acid-precipitated product, which is then dried to obtain molybdic acid.

4. The method for preparing flake-shaped ammonium dimolybdate as described in claim 1, characterized in that, In step (2): When ammonium bicarbonate is selected as the ammonium source, the molar ratio of molybdic acid to ammonium bicarbonate is 1:0.9~1.3; When ammonium carbonate is selected as the ammonium source, the molar ratio of molybdic acid to ammonium carbonate is 1.9~2.3∶1; When ammonia is used as the ammonium source, the molar ratio of molybdic acid to ammonia is 1:0.9~1.3; When the ammonium source is a mixture of ammonium bicarbonate and ammonium carbonate, the molar ratio of molybdic acid to ammonium bicarbonate and ammonium carbonate is 1:0.5~0.6:0.2~0.3; When the ammonium source is a mixture of ammonium bicarbonate and ammonia, the molar ratio of molybdic acid to ammonium bicarbonate and ammonia is 1:0.5~0.6:0.5~0.6; When the ammonium source is a mixture of ammonium carbonate and ammonia, the molar ratio of molybdic acid to ammonium carbonate and ammonia is 1:0.2~0.3:0.5~0.6; When the ammonium source is a mixture of ammonium bicarbonate, ammonium carbonate and ammonia, the molar ratio of molybdic acid to ammonium bicarbonate, ammonium carbonate and ammonia is 1:0.7~0.9:0.2~0.4:0.7~0.

9.

5. The method for preparing flake-shaped ammonium dimolybdate as described in claim 4, characterized in that, In step (2): When ammonium bicarbonate is selected as the ammonium source, the molar ratio of molybdic acid to ammonium bicarbonate is 1:1; When ammonium carbonate is selected as the ammonium source, the molar ratio of molybdic acid to ammonium carbonate is 2:

1. When ammonia is used as the ammonium source, the molar ratio of molybdic acid to ammonia is 1:

1.

6. The method for preparing flake-shaped ammonium dimolybdate as described in claim 1, characterized in that, In step (2), the drying temperature is 40~200℃; the drying time is 2~10h.

7. The method for preparing flake-shaped ammonium dimolybdate as described in claim 1, characterized in that, In step (2), after drying, the ammonium dimolybdate is filtered through a vibrating screen with a mesh size of 150-400 to obtain flake-shaped ammonium dimolybdate.

8. The method for preparing flake-shaped ammonium dimolybdate as described in claim 1, characterized in that, In step (2), the D50 of the obtained flake ammonium dimolybdate is 86.61 μm to 247.39 μm.

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