Preparation method of high-purity nano tungsten oxide

Abstract

The invention discloses a preparation method of high-purity nano tungsten oxide, which comprises the following steps: S1, dispersing an ammonium metatungstate crude product in ethanol to obtain a mixture, and centrifugally separating the mixture with the ammonium metatungstate crude product to obtain solid ammonium metatungstate and an impurity solution; s2, dissolving the ammonium metatungstate crude product solid ammonium metatungstate in water to obtain an ammonium metatungstate aqueous solution, and then sequentially adding a complexing agent and a chelating agent to obtain a mixed solution; s3, stirring the mixed solution with the ammonium metatungstate crude product, performing evaporative crystallization to obtain crystals, and then calcining the crystals with the ammonium metatungstate crude product to obtain the high-purity nano tungsten oxide with the ammonium metatungstate crude product; according to the method, ammonium metatungstate is primarily purified by utilizing the solubility difference of ethanol on ammonium metatungstate and water-soluble inorganic salt, transition metal impurities and alkaline earth metal ion impurities are sequentially complexed by combining a complexing agent and a chelating agent, step-by-step purification is performed, meanwhile, charge adsorption on the surfaces of particles is reduced, ammonium metatungstate agglomeration is inhibited, and the purity of the ammonium metatungstate is improved. The particle size is uniform and dispersed.

Description

Technical Field

[0001] The present invention relates to the technical field of tungsten oxide materials, and in particular to a method for preparing high-purity nano tungsten oxide. Background Art

[0002] Nano-tungsten oxide, a functional material, has important applications in various industrial fields. Currently, the thermal decomposition process of ammonium metatungstate is widely used in industrial production. However, two prominent issues have emerged during actual production: first, it is difficult to ensure product purity, and second, nanoparticles are prone to agglomeration. These issues directly affect the material's performance and effectiveness.

[0003] Researchers have attempted various improvements to existing technologies, such as using aqueous solutions to dissolve the raw materials and removing impurities with impurity removers. However, this method is not ideal for removing certain impurities, particularly alkaline earth metal ions like calcium and magnesium. Furthermore, it cannot completely solve the problem of particle agglomeration, and the dispersibility of the final product remains poor.

[0004] Therefore, it is necessary to provide a new technical solution to improve the purity of nano-tungsten oxide while also improving its dispersibility. Summary of the Invention

[0005] In view of this, the present application provides a method for preparing high-purity nano-tungsten oxide, which is used to solve the problem of how to improve the purity and dispersibility of nano-tungsten oxide.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions: The present application provides a method for preparing high-purity nano-tungsten oxide, comprising the following steps: S1. The crude ammonium metatungstate is dispersed in ethanol to obtain a mixture, and the mixture is centrifuged to obtain a solid ammonium metatungstate and an impurity solution; S2. dissolving solid ammonium metatungstate in water to obtain an aqueous solution of ammonium metatungstate, and then sequentially adding a complexing agent and a chelating agent to obtain a mixed solution; S3. Stir the mixed solution and evaporate and crystallize to obtain crystals, and then calcine the crystals to obtain high-purity nano-tungsten oxide.

[0007] Preferably, the complexing agent includes one or more of ethylenediaminetetraacetic acid and citric acid.

[0008] Preferably, the molar ratio of the complexing agent to the crude ammonium metatungstate is 1-3:1.

[0009] Preferably, the chelating agent is aminotrimethylenephosphonic acid.

[0010] Preferably, the molar ratio of the chelating agent to the crude ammonium metatungstate is 1:0.5-1.5.

[0011] Preferably, the mass ratio of the crude ammonium metatungstate to ethanol is 1:5-15.

[0012] Preferably, the centrifugal separation speed is 3000-6000 r / min, and the centrifugal time is 5-20 min.

[0013] Preferably, the temperature of the evaporation crystallization is 40-80℃.

[0014] Preferably, the stirring speed is 100-300 r / min.

[0015] Preferably, the final temperature of the calcination is 400-800℃, the calcination time is 2-6 h, and the temperature rising rate is 2-10℃ / min.

[0016] The application has the following beneficial effects: the application utilizes the solubility difference of ammonium metatungstate and water-soluble inorganic salt in ethanol, preliminarily purifies the ammonium metatungstate, then uses a complexing agent and a chelating agent in combination, sequentially complexes transition metal impurities and alkaline earth metal ion impurities, performs step-by-step purification, reduces the surface charge adsorption of particles, inhibits the agglomeration of ammonium metatungstate, and makes the particle size uniform and dispersed. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the application clearer, the application is further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0018] The application provides a preparation method of high-purity nano tungsten oxide, which comprises the following steps: S1. dispersing crude ammonium metatungstate in ethanol to obtain a mixture, and centrifugally separating the mixture to obtain solid ammonium metatungstate and an impurity solution; S2. dissolving the solid ammonium metatungstate in water to obtain an ammonium metatungstate aqueous solution, then sequentially adding a complexing agent and a chelating agent to obtain a mixed solution; S3. stirring the mixed solution and evaporating and crystallizing to obtain crystals, and then calcining the crystals to obtain high-purity nano tungsten oxide.

[0019] Step S1 of the application utilizes the solubility difference of ammonium metatungstate and water-soluble inorganic salt (such as Mg 2+ , Fe 2+ ) in ethanol, the ammonium metatungstate is not soluble in ethanol, and the ammonium metatungstate is preliminarily purified; step S2 uses a complexing agent (EDTA) and a chelating agent (ATMP) to synergistically complex transition metal impurities (logK>20) and alkaline earth metal ion impurities (logK=8-12) in sequence, performs step-by-step purification, reduces the surface charge adsorption of particles, inhibits the agglomeration of ammonium metatungstate, and makes the particle size uniform and dispersed.

[0020] In the present application, the complexing agent, such as EDTA, preferentially complexes high-stability metal ions (such as Fe 3+ ), and the chelating agent ATMP complements the complexing of alkaline earth metals (such as Ca 2+ , Mg 2+ ), avoiding the blind area of a single complexing agent, while the complexing agent can effectively inhibit the agglomeration of nanoparticles.

[0021] In some embodiments, the complexing agent includes one or more of ethylenediaminetetraacetic acid and citric acid.

[0022] In some embodiments, the molar ratio of the complexing agent to the ammonium metatungstate crude product is 1-3:1.

[0023] In the present application, the impurity content in the ammonium metatungstate crude product is about 0.5%, and the molar amount of impurities has a small effect on the ammonium metatungstate crude product.

[0024] In the present application, the complexing agent complexes transition metal impurity ions in the solution, inhibiting the agglomeration of nanoparticles.

[0025] In some embodiments, the chelating agent is aminotri(methylene) phosphonic acid.

[0026] In some embodiments, the molar ratio of the chelating agent to the ammonium metatungstate crude product is 1:0.5-1.5.

[0027] In some embodiments, the mass ratio of the ammonium metatungstate crude product to ethanol is 1:5-15.

[0028] In the present application, the chelating agent removes impurities of alkaline earth metal ions, making up for the impurity removal blind area of a single complexing agent; without adding the chelating agent, the following adverse effects may occur: incomplete impurity removal, inability to improve purity, limited complexing ability of EDTA and citric acid for Ca 2+ , Mg 2+ , intensified nanoparticle agglomeration and performance degradation, such as Ca 2+ and the like easily adsorbed on the surface of nanoparticle tungsten oxide particles, resulting in increased interparticle attraction.

[0029] The complexing agent and the chelating agent have a synergistic effect, the complexing agent first removes high-stability constant transition metal ions (logK>20), and the chelating agent (ATMP) then removes low-stability constant alkaline earth metal ions (logK=8-12), forming a "step-by-step purification" mechanism.

[0030] In some embodiments, the speed of centrifugal separation is 3000-6000r / min, and the centrifugal time is 5-20min.

[0031] In some embodiments, the temperature of evaporation crystallization is 40-80℃.

[0032] In the present application, the evaporation crystallization in a limited range can prevent the crystal size difference caused by local supersaturation.

[0033] In some embodiments, the stirring speed is 100-300 r / min.

[0034] In the present application, the solution is continuously stirred during the evaporation process to make the solution evaporate uniformly and promote the uniform growth of the crystals.

[0035] In some embodiments, the final temperature of the calcination is 400-800°C, the calcination time is 2-6 h, and the heating rate is 2-10°C / min.

[0036] In the present application, during the high-temperature calcination process, the crystals undergo decomposition and oxidation reactions, and finally high-purity nano tungsten oxide is obtained. The calcination final temperature ensures that the tungsten oxide is completely converted into a monoclinic phase, and the heating rate in a limited range can completely convert the tungsten oxide into a monoclinic phase.

[0037] The present scheme is further described below through specific embodiments.

[0038] Example 1 A method for preparing high-purity nano tungsten oxide includes the following steps: S1. 10 g of crude ammonium metatungstate is added to 50 g of ethanol, stirred at a stirring speed of 200 r / min for 0.5 h to form a mixture (ammonium metatungstate crude product-ethanol dispersion), and then centrifuged at a speed of 3000 r / min for 10 min to obtain solid ammonium metatungstate and an impurity solution; S2. The solid ammonium metatungstate is dissolved in water at a solid-liquid ratio of 1:5 to obtain an ammonium metatungstate aqueous solution. 1.9 g of ethylenediaminetetraacetic acid (EDTA) is first added to the ammonium metatungstate aqueous solution, and then 0.78 g of amino-tris-methyl phosphonic acid is added. Stirring is carried out at room temperature of 25°C for 1 h to obtain a mixed solution; S3. The mixed solution is placed in an evaporating dish and subjected to evaporation crystallization at a water bath temperature of 80°C and a stirring speed of 200 r / min until the solution is concentrated to a large number of crystals. The crystals are transferred to a crucible and placed in a muffle furnace. The temperature is raised to 600°C at a heating rate of 5°C / min, and calcination is carried out for 2 h to obtain high-purity nano tungsten oxide.

[0039] Detection shows that the purity of the nano tungsten oxide is 99.99%, the average particle size is 35-40 nm, and the particle dispersion is good.

[0040] Example 2 A method for preparing high-purity nano tungsten oxide includes the following steps: S1. Add 10g of crude ammonium metatungstate to 50g of ethanol and stir at 200r / min for 0.5h to form a mixture (crude ammonium metatungstate-ethanol dispersion). Then centrifuge at 3000r / min for 10min to obtain a solution of solid ammonium metatungstate and impurities. S2. Dissolve solid ammonium metatungstate in water at a solid-liquid ratio of 1:5 to obtain an aqueous solution of ammonium metatungstate. 2.85 g of citric acid and 1.46 g of aminotri(methylenephosphonic) acid were added to the aqueous solution of ammonium metatungstate, and the mixture was stirred at room temperature of 25 ° C for 1 h to obtain a mixed solution. S3. Place the mixed solution in an evaporating dish and evaporate and crystallize it at a stirring speed of 200 r / min in a water bath at a temperature of 80°C until the solution is concentrated to form a large number of crystals. Transfer the crystals to a crucible and place it in a muffle furnace. Heat it to 800°C at a heating rate of 10°C / min and calcine it for 2 hours to obtain high-purity nano-tungsten oxide.

[0041] After testing, the purity of the nano tungsten oxide is 99.95%, the average particle size is 30-35nm, and the particles are slightly agglomerated.

[0042] Example 3 A method for preparing high-purity nano-tungsten oxide comprises the following steps: S1. Add 10g of crude ammonium metatungstate to 150g of ethanol and stir at a stirring speed of 200r / min for 0.5h to form a mixture (crude ammonium metatungstate-ethanol dispersion). Then centrifuge at a speed of 3000r / min for 10min to obtain a solution of solid ammonium metatungstate and impurities. S2. Dissolve solid ammonium metatungstate in water at a solid-liquid ratio of 1:5 to obtain an ammonium metatungstate aqueous solution. First, add 0.95 g of ethylenediaminetetraacetic acid (EDTA) to the ammonium metatungstate aqueous solution, then add 0.68 g of aminotri(methylenephosphonic acid), and stir at room temperature of 25°C for 1 hour to obtain a mixed solution. S3. Place the mixed solution in an evaporating dish and evaporate and crystallize it at a stirring speed of 200 r / min in a water bath at a temperature of 80°C until the solution is concentrated to the point where a large amount of crystals appear. Transfer the crystals to a crucible and place it in a muffle furnace. Raise the temperature to 400°C at a heating rate of 2°C / min and calcine for 6 hours to obtain high-purity nano-tungsten oxide.

[0043] After testing, the purity of the nano tungsten oxide is 99.85%, the average particle size is 45-50nm, and the particles are obviously agglomerated.

[0044] Comparative Example 1 A method for preparing nano-tungsten oxide is the same as Example 1 in other aspects, except that the complexing agent is not replaced by an equal amount of a chelating agent.

[0045] After testing, the purity of the nano tungsten oxide is 99.85%, the average particle size is 60-65nm, and the particles are mostly agglomerated.

[0046] Comparative Example 2 A method for preparing nano-tungsten oxide is the same as Example 1 in other aspects, except that the chelating agent is not replaced by an equal amount of complexing agent.

[0047] After testing, the purity of the nano tungsten oxide is 99.88%, the average particle size is 40-45nm, and the particle dispersion is good.

[0048] The present application utilizes the difference in solubility of ethanol for ammonium metatungstate and water-soluble inorganic salts to preliminarily purify the ammonium metatungstate, and then uses a complexing agent and a chelating agent in combination to sequentially complex transition metal impurities and alkaline earth metal ion impurities for step-by-step purification, while reducing the surface charge adsorption of the particles, inhibiting the agglomeration of the ammonium metatungstate, and making the particle size uniform and dispersed.

[0049] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing high-purity nano-tungsten oxide, characterized in that: The following steps are involved: S1. The crude ammonium metatungstate is dispersed in ethanol to obtain a mixture, and the mixture is centrifuged to obtain a solid ammonium metatungstate and an impurity solution; S2. The solid ammonium metatungstate is dissolved in water to obtain an aqueous solution of ammonium metatungstate, and then a complexing agent and a chelating agent are sequentially added to obtain a mixed solution; S3. Stirring the mixed solution and evaporating and crystallizing to obtain crystals, and then calcining the crystals to obtain the high-purity nano-tungsten oxide.

2. The method for preparing high-purity nano-tungsten oxide according to claim 1, wherein: The complexing agent includes one or more of ethylenediaminetetraacetic acid and citric acid.

3. The method for preparing high-purity nano-tungsten oxide according to claim 1, wherein: The molar ratio of the complexing agent to the crude ammonium metatungstate is 1-3:

1.

4. The method for preparing high-purity nano-tungsten oxide according to claim 1, wherein: The chelating agent is aminotrimethylenephosphonic acid.

5. The method for preparing high-purity nano-tungsten oxide according to claim 1, wherein: The molar ratio of the chelating agent to the crude ammonium metatungstate is 1:0.5-1.

5.

6. The method for preparing high-purity nano-tungsten oxide according to claim 1, characterized in that: The mass ratio of the crude ammonium metatungstate to ethanol is 1:5-15.

7. The method for preparing high-purity nano-tungsten oxide according to claim 1, wherein: The centrifugal separation speed is 3000-6000 r / min, and the centrifugal time is 5-20 min.

8. The method for preparing high-purity nano-tungsten oxide according to claim 1, characterized in that: The temperature of the evaporation crystallization is 40-80°C.

9. The method for preparing high-purity nano-tungsten oxide according to claim 1, characterized in that: The stirring speed is 100-300 r / min.

10. The method for preparing high-purity nano-tungsten oxide according to claim 1, characterized in that: The final calcination temperature is 400-800° C., the calcination time is 2-6 hours, and the heating rate is 2-10° C. / min.