Preparation method of high-purity molybdenum trioxide

Abstract

The present invention provides a method for preparing high-purity molybdenum trioxide, belongs to the technical field of molybdenum trioxide production, and comprises the following steps: step S1, molybdenum ore is crushed and ground, roasted, crude molybdenum oxide is obtained, added to sodium hydroxide solution, heated and stirred, filtered, and crude sodium molybdate solution is obtained; step S2, the crude sodium molybdate solution is adjusted to pH 5.5-7.0, an exchange column of macroporous cation exchange resin is passed, and the solution pH is adjusted to 7.0-8.5, and an exchange column equipped with anion exchange resin is passed to obtain a high-purity sodium molybdate solution; step S3, excessive ammonia water is added to the high-purity sodium molybdate solution, ammonium molybdate is precipitated, washed, and dried to obtain high-purity ammonium molybdate; step S4, high-purity ammonium molybdate is put into a rotary calcining furnace, the inner wall of the furnace tube is sprayed with rare earth oxide, and a calcination mode of first heating, then cooling, and then heating is adopted to prepare high-purity molybdenum trioxide. The present invention realizes the purpose of producing high-purity molybdenum trioxide.

Description

Technical Field

[0001] The invention relates to the technical field of molybdenum trioxide production, and in particular to a method for preparing high-purity molybdenum trioxide. Background Art

[0002] Molybdenum is an important metal element with important industrial application value. With the development of high-tech industries, especially high-performance materials, electronics industry, energy field, etc., the demand for molybdenum is increasing. High-purity trioxide is one of the main chemical forms of molybdenum, which is mainly used in the manufacture of molybdenum alloys, thin film materials, electronic components and high-temperature coatings.

[0003] High-purity molybdenum trioxide has excellent physical and chemical properties and can be used in the manufacture of semiconductors and electronic components; as a chemical catalyst, high-purity molybdenum trioxide is used in petrochemicals, catalytic reactions, ammonia synthesis and other processes. Therefore, the preparation of high-purity molybdenum trioxide has become a key technical direction in the fields of materials science and chemical engineering, especially in the steps of ion exchange and purification of sodium molybdate solution and precipitation of ammonium molybdate, which has become an important technical route for the preparation of high-purity molybdenum compounds.

[0004] Ammonium molybdate solution generally contains cationic impurities Fe 2+ , Cu 2+ Mg 2+ , Ca 2+ , K + 、Na + And anionic impurities Cl - 、SO4 2- 、NO 3- In the crystallization process of ammonium molybdate, multiple recrystallizations are often required to obtain high-purity ammonium molybdate. The ion exchange of existing sodium molybdate solutions generally involves single ion exchange, which results in the formation of metal impurity ions or Cl - 、SO4 2- The plasma cannot be removed, which affects the purity of the subsequently produced ammonium molybdate and molybdenum trioxide and makes it impossible to meet high-purity standards.

[0005] The process of preparing molybdenum trioxide by ammonium molybdate roasting often adopts the method of passing oxygen and gradually increasing the temperature for calcination. The gradual increase in temperature makes it difficult to control the reaction, making it difficult for the purity of the final molybdenum trioxide to reach high purity standards.

[0006] Therefore, it is necessary to provide a method for preparing high-purity molybdenum trioxide to solve the problems existing in the above-mentioned prior art. Summary of the invention

[0007] In view of this, the present invention provides a method for preparing high-purity molybdenum trioxide, which can achieve the purpose of producing high-purity molybdenum trioxide.

[0008] The specific scheme of the present invention is as follows: a method for preparing high-purity molybdenum trioxide comprises the following steps:

[0009] Step S1, crushing and grinding molybdenum ore, roasting to obtain crude molybdenum oxide, adding it to a sodium hydroxide solution, heating and stirring, filtering, and obtaining a crude sodium molybdate solution;

[0010] Step S2, adjusting the pH of the crude sodium molybdate solution to 5.5-7.0, passing it through an exchange column of a macroporous cation exchange resin, and then adjusting the solution pH to 7.0-8.5, passing it through an exchange column filled with an anion exchange resin to obtain a high-purity sodium molybdate solution;

[0011] Step S3, adding excess ammonia water to the high-purity sodium molybdate solution to precipitate ammonium molybdate, washing, and drying to obtain high-purity ammonium molybdate;

[0012] Step S4, placing high-purity ammonium molybdate into a rotary calcining furnace, spraying the inner wall of the furnace tube with rare earth oxide, and adopting a calcination method of first heating, then cooling, and then heating again to obtain high-purity molybdenum trioxide;

[0013] The rare earth oxide is one of yttrium oxide, lanthanum oxide and cerium oxide.

[0014] Cation exchange resin exchanges cationic impurities in the solution through electrostatic adsorption. Usually, the exchangeable cations in the resin will exchange with cations in the solution (such as calcium, magnesium, iron and other metal ions), thereby removing the impurity metal ions in the sodium molybdate solution. Anion exchange resin absorbs impurity anions in the solution (such as SO4 2- 、NO 3- ), further improve the purity of sodium molybdate solution.

[0015] Although some impurities can be removed in a single ion exchange process, they are usually not completely removed. These impurities will have an adverse effect on the purity of sodium molybdate at higher concentrations, and in the preparation of high-purity sodium molybdate, these impurities often cause problems in subsequent processes and reduce the purity of the final product.

[0016] Through two ion exchanges, different types of impurities can be removed more effectively in stages. The first time, cation exchange resin is used to remove cationic impurities in the sodium molybdate solution. Macroporous cation exchange resin is specially used to adsorb cationic impurities in the sodium molybdate solution. After pH adjustment, the molybdate ions in the sodium molybdate solution can continue to enter the second ion exchange process in a state of higher purity. The second ion exchange uses anion exchange resin to remove anionic impurities. This step-by-step exchange for different ions effectively improves the resin selectivity in each step, thereby ensuring higher purity. This staged exchange process makes the removal of impurities more thorough and effectively improves the purity of sodium molybdate. The two staged ion exchanges reduce the load on the resin. The resin in each step only needs to deal with specific types of ionic impurities, which extends the service life of the resin and reduces the decrease in adsorption efficiency due to excessive resin load.

[0017] The inner wall of the furnace tube of the calcining furnace is sprayed with rare earth oxides such as cerium oxide, lanthanum oxide, and yttrium oxide. Its surface has abundant surface active sites. During the calcination process, it can adsorb impurity metal ions and react with them to form a stable complex, preventing them from entering the crystal structure of molybdenum trioxide, inhibiting their doping in molybdenum trioxide crystals, so that metal impurities are effectively captured and the purity of molybdenum trioxide is improved. During the high-temperature calcination process, molybdenum oxide crystals may produce crystal defects (such as dislocations, vacancies, etc.) due to uneven temperature or high-temperature stress. Cerium oxide, lanthanum oxide, yttrium oxide, etc. can promote the crystallization of molybdenum oxide, make the crystal growth more regular, reduce the occupancy of impurities, and ultimately improve the purity of molybdenum trioxide.

[0018] The traditional gradual heating process easily leads to excessive temperature, too violent or incomplete reaction, and the generation of by-products, which affects the purity of the final product. The process of heating first, then cooling, and then gradually heating can effectively suppress the situation of excessive or incomplete reaction. By cooling in the second temperature range, the reaction is slowed down, which helps to further optimize the crystal morphology of the product, promote the crystallization and purification of the target product, and is also conducive to controlling the smooth progress of the reaction and avoiding the occurrence of excessive oxidation. In addition, some impurities or intermediates may be unstable at high temperatures. The cooling stage helps to promote their decomposition or transformation, reduce the incorporation of impurities into the target product, and further improve the purity of molybdenum trioxide.

[0019] Preferably, in step S1, the particle size of the molybdenum ore after grinding is 80-100 mesh; the roasting temperature is 600-800°C, and the time is 1.5-2.5h; the heating and stirring speed is 400-500rpm, the time is 2-3h, and the temperature is 80-90°C.

[0020] Preferably, in step S2, the flow rate of the solution in the exchange column is 0.5-2 BV / h, and the temperature is 20-30°C.

[0021] Preferably, the macroporous cation exchange resin includes one of Dowex 50W-X8, Amberlite IR120 and ZL-300; the anion exchange resin includes one of Dowex 2X8, Amberlite IRA-400 and ZL-100.

[0022] Preferably, in step S3, the concentration of aqueous ammonia is 25-28 wt %.

[0023] Preferably, in step S4, the furnace tube of the calcining furnace is divided into five temperature zones, namely, a first temperature zone, a second temperature zone, a third temperature zone, a fourth temperature zone and a fifth temperature zone.

[0024] Preferably, the temperature of the first temperature zone is 350-400°C, and the residence time is 3-5min; the temperature of the second temperature zone is 300-350°C, and the residence time is 5-8min; the temperature of the third temperature zone is 450-550°C, and the residence time is 10-15min; the temperature of the fourth temperature zone is 550-650°C, and the residence time is 6-10min; the temperature of the fifth temperature zone is 650-700°C, and the residence time is 3-5min.

[0025] Preferably, 1-2 parts by weight of diethylenetriaminepentaacetic acid are also added to the second temperature zone.

[0026] Preferably, the speed of introducing air into the first temperature zone is 20-30 L / min; the speed of introducing oxygen into the second temperature zone is 15-25 L / min, and the concentration of oxygen is 30-35wt%; the speed of introducing pure oxygen into the third temperature zone is 30-40 L / min; the speed of introducing pure oxygen into the fourth temperature zone is 30-40 L / min; the speed of introducing oxygen into the fifth temperature zone is 20-30 L / min, and the concentration of oxygen is 21-30wt%.

[0027] Diethylenetriaminepentaacetic acid contains multiple coordination sites and can effectively chelate light metal ions, such as calcium and magnesium. By chelating these metal impurity ions, volatile complexes are formed and discharged with the tail gas during the calcination process, thereby reducing the content of impurities in the final product and helping to improve the purity of the target product, molybdenum trioxide. In addition, the amount of diethylenetriaminepentaacetic acid added is small and has no effect on the yield of molybdenum trioxide.

[0028] Preferably, the following components are included in parts by weight:

[0029] 40-50 parts of molybdenum ore, 80-90 parts of sodium hydroxide solution, 90-100 parts of ammonia water, and 1-2 parts of rare earth oxide.

[0030] The above technical solution of the present invention includes at least the following beneficial effects:

[0031] (1) Two ion exchanges can more effectively remove different types of impurities in stages. The first ion exchange uses cation exchange resin to remove cationic impurities in the sodium molybdate solution, and the second ion exchange uses anion exchange resin to remove anionic impurities, making the removal of impurities more thorough, effectively improving the purity of sodium molybdate, and further improving the purity of the target product molybdenum trioxide.

[0032] (2) Yttrium oxide, lanthanum oxide and cerium oxide can adsorb impure metal ions, effectively capturing metal impurities and preventing them from entering the crystal structure of molybdenum trioxide. They can also promote the crystallization of molybdenum oxide and improve the purity of molybdenum trioxide.

[0033] (3) By cooling in the second temperature range, the reaction is slowed down, which helps to further optimize the structure and crystal morphology of molybdenum trioxide, promote its crystallization and purification, and control the smooth progress of the reaction to avoid the occurrence of excessive oxidation. At the same time, it helps to promote the decomposition or transformation of impurities, reduce the incorporation of impurities, and further improve the purity of molybdenum trioxide. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described in combination with the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0035] Example 1

[0036] (1) 45 parts of molybdenum ore were crushed and ground to obtain powdered molybdenum ore (80-100 mesh), and the powdered ore was calcined at 700°C for 2 hours to obtain crude molybdenum oxide, which was dissolved in 85 parts of sodium hydroxide solution, heated to 80°C, stirred at 500 rpm for 2.5 hours, and filtered to obtain a crude sodium molybdate solution.

[0037] (2) The pH value of the crude sodium molybdate solution is adjusted to 5.5-7.0, and the crude sodium molybdate solution is passed through an exchange column filled with a macroporous cation exchange resin. The flow rate of the solution is controlled at 1 BV / h and the temperature is maintained at 25°C to obtain a sodium molybdate solution. The pH value of the sodium molybdate solution is adjusted to 7.0-8.5, and the crude sodium molybdate solution is passed through an exchange column filled with an anion exchange resin. The flow rate is controlled at 1 BV / h and the temperature of the solution is maintained at 25°C to obtain a high-purity sodium molybdate solution.

[0038] (3) Add 95 parts of aqueous ammonia (28 wt % concentration) to the high-purity sodium molybdate solution to precipitate ammonium molybdate, wash with deionized water, and dry to obtain high-purity ammonium molybdate.

[0039] (4) High-purity ammonium molybdate is placed in a rotary calcining furnace, and 2 parts of lanthanum oxide are sprayed on the inner wall of the furnace tube for calcination. The temperature of the first temperature zone is 400°C, and air is introduced at a rate of 25 L / min for a residence time of 4 minutes. The temperature of the second temperature zone is 300°C, and 30-35wt% oxygen is introduced at a rate of 20 L / min, and 2 parts of diethylenetriaminepentaacetic acid are added for a residence time of 7 minutes. The temperature of the third temperature zone is 500°C, and pure oxygen is introduced at a rate of 35 L / min for a residence time of 15 minutes. The temperature of the fourth temperature zone is 600°C, and pure oxygen is introduced at a rate of 35 L / min for a residence time of 8 minutes. The temperature of the fifth temperature zone is 700°C, and 21-30wt% oxygen is introduced at a rate of 25 L / min for a residence time of 3 minutes to obtain high-purity molybdenum trioxide.

[0040] Example 2

[0041] (1) 40 parts of molybdenum ore were crushed and ground to obtain powdered molybdenum ore (80-100 mesh), and the powdered ore was calcined at 750°C for 1.5 hours to obtain crude molybdenum oxide, which was dissolved in 85 parts of sodium hydroxide solution, heated to 90°C, stirred at 400 rpm for 3 hours, and filtered to obtain a crude sodium molybdate solution.

[0042] (2) The pH value of the crude sodium molybdate solution is adjusted to 5.5-7.0, and the crude sodium molybdate solution is passed through an exchange column filled with a macroporous cation exchange resin. The flow rate of the solution is controlled at 1.5 BV / h and the temperature is maintained at 25°C to obtain a sodium molybdate solution. The pH value of the sodium molybdate solution is adjusted to 7.0-8.5, and the crude sodium molybdate solution is passed through an exchange column filled with an anion exchange resin. The flow rate is controlled at 1.5 BV / h and the temperature of the solution is maintained at 25°C to obtain a high-purity sodium molybdate solution.

[0043] (3) Add 100 parts of aqueous ammonia (28 wt% concentration) to the high-purity sodium molybdate solution to precipitate ammonium molybdate, wash with deionized water, and dry to obtain high-purity ammonium molybdate.

[0044] (4) High-purity ammonium molybdate is placed in a rotary calcining furnace, and 1 part of yttrium oxide is sprayed on the inner wall of the furnace tube for calcination. The temperature of the first temperature zone is 380°C, and air is introduced at a rate of 30 L / min for a residence time of 3 min. The temperature of the second temperature zone is 350°C, and 30-35 wt% oxygen is introduced at a rate of 15 L / min, and 1 part of diethylenetriamine pentaacetic acid is added for a residence time of 6 min. The temperature of the third temperature zone is 550°C, and pure oxygen is introduced at a rate of 35 L / min for a residence time of 10 min. The temperature of the fourth temperature zone is 550°C, and pure oxygen is introduced at a rate of 35 L / min for a residence time of 6 min. The temperature of the fifth temperature zone is 680°C, and 21-30 wt% oxygen is introduced at a rate of 20 L / min for a residence time of 4 min to obtain high-purity molybdenum trioxide.

[0045] Example 3

[0046] (1) 50 parts of molybdenum ore are crushed and ground to obtain powdered molybdenum ore (80-100 mesh), and the powdered ore is calcined at 650°C for 2.5 hours to obtain crude molybdenum oxide, which is dissolved in 80 parts of sodium hydroxide solution, heated to 80°C, stirred at 450 rpm for 2.5 hours, and filtered to obtain a crude sodium molybdate solution.

[0047] (2) The pH value of the crude sodium molybdate solution is adjusted to 5.5-7.0, and the crude sodium molybdate solution is passed through an exchange column filled with a macroporous cation exchange resin. The flow rate of the solution is controlled at 1.5 BV / h and the temperature is maintained at 20°C to obtain a sodium molybdate solution. The pH value of the sodium molybdate solution is adjusted to 7.0-8.5, and the crude sodium molybdate solution is passed through an exchange column filled with an anion exchange resin. The flow rate is controlled at 1.5 BV / h and the temperature of the solution is maintained at 20°C to obtain a high-purity sodium molybdate solution.

[0048] (3) Add 95 parts of aqueous ammonia (26 wt % concentration) to the high-purity sodium molybdate solution to precipitate ammonium molybdate, wash with deionized water, and dry to obtain high-purity ammonium molybdate.

[0049] (4) High-purity ammonium molybdate is placed in a rotary calcining furnace, and 1 part of cerium oxide is sprayed on the inner wall of the furnace tube for calcination. The temperature of the first temperature zone is 350°C, and air is introduced at a rate of 30 L / min for a residence time of 5 min. The temperature of the second temperature zone is 320°C, and 30-35 wt% oxygen is introduced at a rate of 17 L / min, and 2 parts of diethylenetriaminepentaacetic acid are added for a residence time of 8 min. The temperature of the third temperature zone is 450°C, and pure oxygen is introduced at a rate of 40 L / min for a residence time of 15 min. The temperature of the fourth temperature zone is 600°C, and pure oxygen is introduced at a rate of 37 L / min for a residence time of 9 min. The temperature of the fifth temperature zone is 680°C, and 21-30 wt% oxygen is introduced at a rate of 22 L / min for a residence time of 3 min to obtain high-purity molybdenum trioxide.

[0050] Example 4

[0051] (1) 43 parts of molybdenum ore were crushed and ground to obtain powdered molybdenum ore (80-100 mesh), and the powdered ore was calcined at 800°C for 1.5 hours to obtain crude molybdenum oxide, which was dissolved in 90 parts of sodium hydroxide solution, heated to 85°C, stirred at 400 rpm for 3 hours, and filtered to obtain a crude sodium molybdate solution.

[0052] (2) The pH value of the crude sodium molybdate solution is adjusted to 5.5-7.0, and the crude sodium molybdate solution is passed through an exchange column filled with a macroporous cation exchange resin. The flow rate of the solution is controlled at 2BV / h and the temperature is maintained at 20°C to obtain a sodium molybdate solution. The pH value of the sodium molybdate solution is adjusted to 7.0-8.5, and the crude sodium molybdate solution is passed through an exchange column filled with an anion exchange resin. The flow rate is controlled at 2BV / h and the temperature of the solution is maintained at 20°C to obtain a high-purity sodium molybdate solution.

[0053] (3) Add 90 parts of aqueous ammonia (28 wt% concentration) to the high-purity sodium molybdate solution to precipitate ammonium molybdate, wash with deionized water, and dry to obtain high-purity ammonium molybdate.

[0054] (4) High-purity ammonium molybdate is placed in a rotary calcining furnace, 1.5 parts of yttrium oxide are sprayed on the inner wall of the furnace tube, and calcination is carried out. The temperature of the first temperature zone is 400°C, air is introduced at a rate of 20 L / min, and the residence time is 4 minutes. The temperature of the second temperature zone is 350°C, 30-35wt% oxygen is introduced at a rate of 15 L / min, and 1.5 parts of diethylenetriaminepentaacetic acid are added, and the residence time is 6 minutes. The temperature of the third temperature zone is 450°C, pure oxygen is introduced at a rate of 40 L / min, and the residence time is 12 minutes. The temperature of the fourth temperature zone is 580°C, pure oxygen is introduced at a rate of 35 L / min, and the residence time is 10 minutes. The temperature of the fifth temperature zone is 650°C, 21-30wt% oxygen is introduced at a rate of 20 L / min, and the residence time is 5 minutes, to obtain high-purity molybdenum trioxide.

[0055] Example 5

[0056] (1) 46 parts of molybdenum ore were crushed and ground to obtain powdered molybdenum ore (80-100 mesh), and the powdered ore was roasted at 600°C for 2 hours to obtain crude molybdenum oxide, which was dissolved in 90 parts of sodium hydroxide solution, heated to 80°C, stirred at 450 rpm for 2 hours, and filtered to obtain a crude sodium molybdate solution.

[0057] (2) The pH value of the crude sodium molybdate solution is adjusted to 5.5-7.0, and the crude sodium molybdate solution is passed through an exchange column filled with a macroporous cation exchange resin. The flow rate of the solution is controlled at 0.5 BV / h and the temperature is maintained at 25°C to obtain a sodium molybdate solution. The pH value of the sodium molybdate solution is adjusted to 7.0-8.5, and the crude sodium molybdate solution is passed through an exchange column filled with an anion exchange resin. The flow rate is controlled at 0.5 BV / h and the temperature of the solution is maintained at 25°C to obtain a high-purity sodium molybdate solution.

[0058] (3) Add 95 parts of aqueous ammonia (25 wt% concentration) to the high-purity sodium molybdate solution to precipitate ammonium molybdate, wash with deionized water, and dry to obtain high-purity ammonium molybdate.

[0059] (4) High-purity ammonium molybdate is placed in a rotary calcining furnace, and 2 parts of cerium oxide are sprayed on the inner wall of the furnace tube for calcination. The temperature of the first temperature zone is 350°C, and air is introduced at a rate of 25 L / min for a residence time of 3 min. The temperature of the second temperature zone is 300°C, and 30-35wt% oxygen is introduced at a rate of 20 L / min, and 1 part of diethylenetriaminepentaacetic acid is added for a residence time of 7 min. The temperature of the third temperature zone is 550°C, and pure oxygen is introduced at a rate of 38 L / min for a residence time of 10 min. The temperature of the fourth temperature zone is 600°C, and pure oxygen is introduced at a rate of 40 L / min for a residence time of 6 min. The temperature of the fifth temperature zone is 700°C, and 21-30wt% oxygen is introduced at a rate of 25 L / min for a residence time of 4 min to obtain high-purity molybdenum trioxide.

[0060] Example 6

[0061] (1) 47 parts of molybdenum ore were crushed and ground to obtain powdered molybdenum ore (80-100 mesh), and the powdered ore was roasted at 700°C for 2 hours to obtain crude molybdenum oxide, which was dissolved in 90 parts of sodium hydroxide solution, heated to 80°C, stirred at 450 rpm for 2 hours, and filtered to obtain a crude sodium molybdate solution.

[0062] (2) The pH value of the crude sodium molybdate solution is adjusted to 5.5-7.0, and the crude sodium molybdate solution is passed through an exchange column filled with a macroporous cation exchange resin. The flow rate of the solution is controlled at 1 BV / h and the temperature is maintained at 30°C to obtain a sodium molybdate solution. The pH value of the sodium molybdate solution is adjusted to 7.0-8.5, and the crude sodium molybdate solution is passed through an exchange column filled with an anion exchange resin. The flow rate is controlled at 1 BV / h and the temperature of the solution is maintained at 30°C to obtain a high-purity sodium molybdate solution.

[0063] (3) Add 100 parts of aqueous ammonia (28 wt% concentration) to the high-purity sodium molybdate solution to precipitate ammonium molybdate, wash with deionized water, and dry to obtain high-purity ammonium molybdate.

[0064] (4) High-purity ammonium molybdate is placed in a rotary calcining furnace, 1.5 parts of lanthanum oxide is sprayed on the inner wall of the furnace tube, and calcination is performed. The temperature of the first temperature zone is 360°C, air is introduced at a rate of 25 L / min, and the residence time is 3 min. The temperature of the second temperature zone is 330°C, 30-35wt% oxygen is introduced at a rate of 20 L / min, and 1 part of diethylenetriaminepentaacetic acid is added, and the residence time is 7 min. The temperature of the third temperature zone is 550°C, pure oxygen is introduced at a rate of 37 L / min, and the residence time is 12 min. The temperature of the fourth temperature zone is 550°C, pure oxygen is introduced at a rate of 38 L / min, and the residence time is 8 min. The temperature of the fifth temperature zone is 650°C, 21-30wt% oxygen is introduced at a rate of 20 L / min, and the residence time is 5 min, to obtain high-purity molybdenum trioxide.

[0065] Example 7

[0066] (1) 42 parts of molybdenum ore were crushed and ground to obtain powdered molybdenum ore (80-100 mesh), and the powdered ore was roasted at 750°C for 2.5 hours to obtain crude molybdenum oxide, which was dissolved in 85 parts of sodium hydroxide solution, heated to 85°C, stirred at 500 rpm for 2 hours, and filtered to obtain a crude sodium molybdate solution.

[0067] (2) The pH value of the crude sodium molybdate solution is adjusted to 5.5-7.0, and the crude sodium molybdate solution is passed through an exchange column filled with a macroporous cation exchange resin. The flow rate of the solution is controlled at 2 BV / h and the temperature is maintained at 30°C to obtain a sodium molybdate solution. The pH value of the sodium molybdate solution is adjusted to 7.0-8.5, and the crude sodium molybdate solution is passed through an exchange column filled with an anion exchange resin. The flow rate is controlled at 2 BV / h and the temperature of the solution is maintained at 30°C to obtain a high-purity sodium molybdate solution.

[0068] (3) Add 90 parts of aqueous ammonia (28 wt% concentration) to the high-purity sodium molybdate solution to precipitate ammonium molybdate, wash with deionized water, and dry to obtain high-purity ammonium molybdate.

[0069] (4) High-purity ammonium molybdate is placed in a rotary calcining furnace, 2 parts of yttrium oxide are sprayed on the inner wall of the furnace tube, and calcination is performed. The temperature of the first temperature zone is 350°C, air is introduced at a rate of 20 L / min, and the residence time is 5 min. The temperature of the second temperature zone is 300°C, 30-35wt% oxygen is introduced at a rate of 17 L / min, and the residence time is 8 min. The temperature of the third temperature zone is 500°C, pure oxygen is introduced at a rate of 35 L / min, and the residence time is 15 min. The temperature of the fourth temperature zone is 550°C, pure oxygen is introduced at a rate of 40 L / min, and the residence time is 7 min. The temperature of the fifth temperature zone is 680°C, 21-30wt% oxygen is introduced at a rate of 25 L / min, and the residence time is 3 min, to obtain high-purity molybdenum trioxide.

[0070] The present invention also carries out comparative examples and related tests.

[0071] Comparative Example 1

[0072] The difference between Comparative Example 1 and Example 1 is that no anion exchange resin is used for ion exchange, and other compositions and preparation methods are the same as those of Example 1, and high-purity molybdenum trioxide is prepared.

[0073] Comparative Example 2

[0074] The difference between Comparative Example 2 and Example 1 is that none of yttrium oxide, lanthanum oxide and cerium oxide is sprayed on the inner wall of the furnace tube, and the other compositions and preparation methods are the same as those of Example 1, and high-purity molybdenum trioxide is prepared.

[0075] Comparative Example 3

[0076] The difference between Comparative Example 3 and Example 1 is that during the calcination process, the second temperature zone is not cooled down, but gradually heated up for calcination. The other compositions and preparation methods are the same as those of Example 1, and high-purity molybdenum trioxide is prepared.

[0077] Performance testing

[0078] The purity analysis test of the molybdenum trioxide prepared in Examples 1-7 and Comparative Examples 1-3 was performed respectively, and the test results are shown in Table 1 below.

[0079] Table 1

[0080]

[0081] According to the data in Table 1, the purity and molybdenum oxidation rate of the high-purity molybdenum trioxide prepared in Comparative Example 1 are lower than those of the high-purity molybdenum trioxide prepared in Examples 1-7. It can be seen that the use of only a single ion exchange resin has a greater impact on the purity of high-purity molybdenum trioxide, indicating that anion and cation exchange is helpful to improve the purity of high-purity molybdenum trioxide; the high-purity molybdenum trioxide prepared in Comparative Example 2 has a certain gap compared with Examples 1-7. It can be seen that yttrium oxide, lanthanum oxide and cerium oxide can promote the crystallization of high-purity molybdenum trioxide and reduce the influence of impurities during the calcination process; Comparative Example 3 adopts the traditional calcination method, and the result is obviously poor, indicating that the method of first heating, then cooling and then gradually heating up in Example 1-7 for preparing high-purity molybdenum trioxide is better than the traditional calcination method; compared with Example 1-6, Example 7 does not add diethylenetriamine pentaacetic acid in the second temperature zone, and the oxidation rate of molybdenum and the purity of molybdenum trioxide are slightly reduced, indicating that diethylenetriamine pentaacetic acid can promote the removal of impurities during the calcination process, which is beneficial to the improvement of the purity of molybdenum trioxide.

[0082] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity molybdenum trioxide, characterized in that: The following steps are involved: Step S1, crushing and grinding molybdenum ore, roasting to obtain crude molybdenum oxide, adding it to a sodium hydroxide solution, heating and stirring, filtering, and obtaining a crude sodium molybdate solution; Step S2, adjusting the pH of the crude sodium molybdate solution to 5.5-7.0, passing it through an exchange column of a macroporous cation exchange resin, and then adjusting the solution pH to 7.0-8.5, passing it through an exchange column filled with an anion exchange resin to obtain a high-purity sodium molybdate solution; Step S3, adding excess ammonia water to the high-purity sodium molybdate solution to precipitate ammonium molybdate, washing, and drying to obtain high-purity ammonium molybdate; Step S4, placing high-purity ammonium molybdate into a rotary calcining furnace, spraying the inner wall of the furnace tube with rare earth oxide, and adopting a calcination method of first heating, then cooling, and then heating again to obtain high-purity molybdenum trioxide; The rare earth oxide is one of yttrium oxide, lanthanum oxide and cerium oxide; In the step S4, the furnace tube of the calcining furnace is divided into five temperature zones, namely the first temperature zone, the second temperature zone, the third temperature zone, the fourth temperature zone and the fifth temperature zone; the temperature of the first temperature zone is 350-400°C, and the residence time is 3-5min; the temperature of the second temperature zone is 300-350°C, and the residence time is 5-8min; the temperature of the third temperature zone is 450-550°C, and the residence time is 10-15min; the temperature of the fourth temperature zone is 550-650°C, and the residence time is 6-10min; the temperature of the fifth temperature zone is 650-700°C, and the residence time is 3-5min.

2. The method for preparing high-purity molybdenum trioxide according to claim 1, characterized in that: In the step S1, the molybdenum ore sand is ground to a particle size of 80-100 mesh; the roasting temperature is 600-800°C, the time is 1.5-2.5h; the heating and stirring speed is 400-500rpm, the time is 2-3h, and the temperature is 80-90°C.

3. The method for preparing high-purity molybdenum trioxide according to claim 1, characterized in that: In step S2, the flow rate of the solution in the exchange column is 0.5-2 BV / h, and the temperature is 20-30°C.

4. The method for preparing high-purity molybdenum trioxide according to claim 1, characterized in that: The macroporous cation exchange resin is one of Dowex 50W-X8, Amberlite IR120 and ZL-300; the anion exchange resin is one of Dowex 2X8, Amberlite IRA-400 and ZL-100.

5. The method for preparing high-purity molybdenum trioxide according to claim 1, characterized in that: In step S3, the concentration of aqueous ammonia is 25-28 wt %.

6. The method for preparing high-purity molybdenum trioxide according to claim 1, characterized in that: 1-2 parts by weight of diethylenetriaminepentaacetic acid are also added into the second temperature zone.

7. The method for preparing high-purity molybdenum trioxide according to claim 1, characterized in that: The air is introduced into the first temperature zone at a speed of 20-30 L / min; the oxygen is introduced into the second temperature zone at a speed of 15-25 L / min, and the concentration of oxygen is 30-35 wt%; the pure oxygen is introduced into the third temperature zone at a speed of 30-40 L / min; the pure oxygen is introduced into the fourth temperature zone at a speed of 30-40 L / min; the oxygen is introduced into the fifth temperature zone at a speed of 20-30 L / min, and the concentration of oxygen is 21-30 wt%.

8. The method for preparing high-purity molybdenum trioxide according to claim 1, characterized in that: The composition comprises the following components in parts by weight: 40-50 parts of molybdenum ore, 80-90 parts of sodium hydroxide solution, 90-100 parts of ammonia water, and 1-2 parts of rare earth oxide.

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