Nanometer tungstic acid with multilevel structure and preparation method thereof

Abstract

The invention belongs to the technical field of tungsten metallurgy, and particularly relates to nano tungstic acid with a multilevel structure and a preparation method thereof.The preparation method comprises the steps that S1, hydrochloric acid is added into a container, continuous stirring is conducted in the adding process, and the temperature in the container is made to be stable; s2, dropwise adding 2-5mL of a sodium tungstate-ammonium tungstate mixed solution B into the container, continuously stirring in the adding process, and enabling the temperature in the container to be stable; s3, 50-200 mL of a sodium tungstate-ammonium tungstate mixed solution A is added into the container, stirring is continuously conducted in the adding process, and the temperature in the container is made to be stable; the amount of the hydrochloric acid added in the step S1 is 2.2-2.6 times of the theoretical amount of the hydrochloric acid required for preparing the tungstic acid according to the concentration of tungstate radicals in the sodium tungstate-ammonium tungstate mixed solution A; s4, repeating the steps S1 and S3; and S5, the prepared tungstic acid is filtered, washed with hydrochloric acid and then dried, the nano tungstic acid with the multilevel structure is obtained, the nano tungstic acid with the multilevel structure comprises blocky tungstic acid and pompon-shaped tungstic acid, and the specific surface area is 50-75 m < 2 > / g.

Description

Technical Field

[0001] The present invention belongs to the technical field of tungsten metallurgy, and particularly relates to a nano tungsten acid with a multi-level structure and a preparation method thereof. Background Art

[0002] Multi-level structure materials refer to materials with multiple hierarchical or scale structure characteristics. Structures at different scales coexist and work together. Through the mutual cooperation of different functions of materials at different levels, materials that take into account performance, cost, and processability are finally obtained, thereby achieving breakthroughs in optical, mechanical, electrical, and thermal properties. Multi-level materials represent the forefront of materials science. By regulating the structure to control the performance and obtain functional materials, it is expected to trigger technological innovations in high-end manufacturing, energy and other fields.

[0003] Nano tungsten acid (H 2 WO 4 ) is a transition metal compound with special physical and chemical properties. Its particle size is usually at the nanometer level, with a large specific surface area and significant surface effects. For industries such as catalysis, batteries, and photovoltaics, an ideal material must necessarily take into account the efficiency of both reaction and mass transfer. At present, many studies have proved that nano-level tungsten acid has excellent performance in many fields. Researchers around the world have prepared multi-level nano tungsten acid materials with different structures and functions through methods such as sol-gel method, hydrothermal method, and template method, and solved many problems in catalysis, environment, energy storage, etc. However, these methods have problems such as high requirements for production equipment, high cost, and low production efficiency, resulting in difficulty in industrialization. Summary of the Invention

[0004] To solve the problems existing in the prior art, the main purpose of the present invention is to propose a nano tungsten acid with a multi-level structure and a preparation method thereof.

[0005] According to one aspect of the present invention, the following technical solution is provided: A preparation method of a nano tungsten acid with a multi-level structure, comprising the following steps: S1. Add hydrochloric acid to a container, continuously stir during the addition process and keep the temperature in the container stable; S2. Drop 2-5 mL of a sodium tungstate-ammonium tungstate mixed solution B into the container, continuously stir during the addition process and keep the temperature in the container stable; S3. Add 50-200 mL of a sodium tungstate-ammonium tungstate mixed solution A to the container, continuously stir during the addition process and keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 2.2-2.6 times the theoretical amount of hydrochloric acid required to prepare tungstic acid according to the tungstate ion concentration in the sodium tungstate-ammonium tungstate mixed solution A; S4. Repeat steps S1 and S3; S5. Filter the obtained tungstic acid, wash it with hydrochloric acid, and then dry it to obtain nano-tungstic acid with a hierarchical structure.

[0006] According to another aspect of the present invention, the present invention provides the following technical solutions: A nano-tungstic acid with a hierarchical structure is prepared by using the above-mentioned preparation method of nano-tungstic acid with a hierarchical structure. The nano-tungstic acid with a hierarchical structure includes massive tungstic acid and flocculent tungstic acid, and the specific surface area is 50-75 m 2 / g.

[0007] The beneficial effects of the present invention are as follows: The present invention proposes a nano-tungstic acid with a hierarchical structure and its preparation method. By using the precipitation method, a multi-level structure nano-tungstic acid assembled by nano-tungstic acid units with different sizes and morphologies is constructed. By preparing seeds, the morphology of tungstic acid can be guided. Alternately adding hydrochloric acid and the sodium tungstate-ammonium tungstate mixed solution A can keep the concentration of hydrochloric acid in the reaction system within a relatively stable range all the time, can control the reaction rate and the concentration of solutes in the solution, and make the particle size of the formed tungstic acid more uniform. The nano-tungstic acid with a hierarchical structure includes massive tungstic acid and flocculent tungstic acid, and the specific surface area is 50-75 m 2 / g. Description of the Drawings

[0008] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0009] Figure 1 It is the electron microscope image of the nano-tungstic acid prepared in Example 1 of the present invention; Figure 2 It is the electron microscope image of the nano-tungstic acid prepared in Example 2 of the present invention; Figure 3 It is the electron microscope image of the nano-tungstic acid prepared in Example 3 of the present invention; Figure 4 It is the electron microscope image of the tungstic acid prepared in Comparative Example 1 of the present invention; Figure 5 It is the electron microscope image of the tungstic acid prepared in Comparative Example 2 of the present invention; Figure 6 It is the electron microscope image of the tungstic acid prepared in Comparative Example 3 of the present invention; Figure 7 It is the electron microscope image of the tungstic acid prepared in Comparative Example 4 of the present invention.

[0010] The realization, functional features, and advantages of the present invention will be further described in conjunction with embodiments and with reference to the accompanying drawings. Detailed Embodiments

[0011] The technical solutions in the embodiments will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0012] In the method for preparing materials, the precipitation method is simple in operation and convenient in reaction control, and is the most easily industrialized preparation method. Therefore, the present invention adopts the precipitation method to construct a multi-level structure nano-tungstic acid assembled from nano-tungstic acid units of different sizes and morphologies, so that while having a large specific surface area and high activity, the overall material obtains a complex morphology and pores, enhancing its mechanical properties and mass transfer efficiency.

[0013] According to one aspect of the present invention, the present invention provides the following technical solution: A preparation method of nano-tungstic acid with a multi-level structure, comprising the following steps: S1. Add hydrochloric acid to a container, continuously stir during the addition process and keep the temperature in the container stable; S2. Drop 2 - 5 mL of a mixed solution B of sodium tungstate and ammonium tungstate into the container, continuously stir during the addition process and keep the temperature in the container stable; S3. Add 50 - 200 mL of a mixed solution A of sodium tungstate and ammonium tungstate to the container, continuously stir during the addition process and keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 2.2 - 2.6 times the theoretical amount of hydrochloric acid required to prepare tungstic acid according to the tungstate ion concentration in the mixed solution A of sodium tungstate and ammonium tungstate; S4. Repeat steps S1 and S3; S5. Filter the prepared tungstic acid, wash it with hydrochloric acid, and then dry it to obtain nano-tungstic acid with a multi-level structure.

[0014] Preferably, in the steps S1 - S3, the temperature in the container is 80 - 100 °C, and the stirring speed is 150 - 250 r / min. Temperature affects the morphology of tungstic acid prepared from ammonium tungstate and sodium tungstate. At low temperatures, tungstic acid prepared from ammonium tungstate forms large flakes, while tungstic acid prepared from sodium tungstate is not fully developed. Specifically, the temperature in the container can be any one of, for example, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C or the range between any two of them. If the stirring speed is too low, tungstic acid is prone to deposit and grow, with a low specific surface area; if the stirring speed is too high, tungstic acid is easily broken, with poor crystal form and poor uniformity. Specifically, the stirring speed can be any one of, for example, 150 r / min, 175 r / min, 200 r / min, 225 r / min, 250 r / min or the range between any two of them.

[0015] Preferably, in the step S1, the concentration of hydrochloric acid is 16 - 22 wt%; there is no special requirement for the addition speed of hydrochloric acid, and it can be added as soon as possible; for example, each time hydrochloric acid is added, it can be added within 5 - 10 s. Specifically, the concentration of hydrochloric acid can be any one of, for example, 16 wt%, 16.5 wt%, 17 wt%, 17.5 wt%, 18 wt%, 18.5 wt%, 19 wt%, 19.5 wt%, 20 wt%, 20.5 wt%, 21 wt%, 21.5 wt%, 22 wt% or the range between any two of them.

[0016] Preferably, in the steps S2 - S3, both the sodium tungstate - ammonium tungstate mixed solution A and the sodium tungstate - ammonium tungstate mixed solution B are prepared by mixing ammonium tungstate solution and sodium tungstate solution with the same concentration in terms of WO 3 calculation, and the volume ratio of the ammonium tungstate solution to the sodium tungstate solution is 1:(0.25 - 4); among them, in the step S2, in terms of WO 3 calculation, the concentration of the sodium tungstate - ammonium tungstate mixed solution B is 240 - 260 g / L; in the step S3, in terms of WO 3 calculation, the concentration of the sodium tungstate - ammonium tungstate mixed solution A is 240 - 260 g / L. Sodium ions and ammonium ions will generate tungstic acid with different morphologies during preparation. Among them, sodium tungstate generates massive tungstic acid to improve mass transfer ability, and ammonium tungstate generates flocculent tungstic acid to provide high - activity sites, and as the ratio of sodium tungstate to ammonium tungstate changes, the ratio of massive tungstic acid to flocculent tungstic acid also changes. Specifically, in terms of WO 3The volume ratio of the ammonium tungstate solution and the sodium tungstate solution with the same concentration can be any one of, for example, 1:0.25, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4 or the range between any two of them. The concentration of the sodium tungstate-ammonium tungstate mixed solution B can be the same as or different from that of the sodium tungstate-ammonium tungstate mixed solution A. The concentration of the sodium tungstate-ammonium tungstate mixed solution B can be any one of, for example, 240 g / L, 245 g / L, 250 g / L, 255 g / L, 260 g / L or the range between any two of them. The concentration of the sodium tungstate-ammonium tungstate mixed solution A can be any one of, for example, 240 g / L, 245 g / L, 250 g / L, 255 g / L, 260 g / L or the range between any two of them.

[0017] Preferably, in the step S2, after dropping 2-5 mL of the sodium tungstate-ammonium tungstate mixed solution B into the container, stir for 8-12 min; the addition rate of the sodium tungstate-ammonium tungstate mixed solution B is 3-5 mL / min. The function of dropping the sodium tungstate-ammonium tungstate mixed solution B is to first form a small amount of tungstic acid as the seed crystal for the subsequent growth of tungstic acid crystals. The seed crystal can guide the morphology of tungstic acid and affect the growth rate of each crystal plane of the tungstic acid prepared from sodium tungstate, causing the crystal planes with fast growth to disappear and forming massive tungstic acid. The dropping amount of the sodium tungstate-ammonium tungstate mixed solution B enables the amount of seed crystals to be controlled within a certain range. Too much or too little will lose the meaning of adding seed crystals, resulting in the inability to stably obtain nano-tungstic acid with a hierarchical structure. Specifically, the amount of the sodium tungstate-ammonium tungstate mixed solution B can be any one of, for example, 2 mL, 3 mL, 4 mL, 5 mL or the range between any two of them. The stirring time after the sodium tungstate-ammonium tungstate mixed solution B can be any one of, for example, 8 min, 9 min, 10 min, 11 min, 12 min or the range between any two of them. The addition rate of the sodium tungstate-ammonium tungstate mixed solution B can be any one of, for example, 3 mL / min, 3.5 mL / min, 4 mL / min, 4.5 mL / min, 5 mL / min or the range between any two of them.

[0018] Preferably, in the step S3, the sodium tungstate-ammonium tungstate mixed solution A is added by a peristaltic pump; the addition rate of the sodium tungstate-ammonium tungstate mixed solution A is 5-17 mL / min; after the addition of the sodium tungstate-ammonium tungstate mixed solution A is completed, stir for 2-5 min and then proceed to step S4. Alternately adding hydrochloric acid and the sodium tungstate-ammonium tungstate mixed solution A can keep the concentration of hydrochloric acid in the reaction system within a relatively stable range all the time, can control the reaction rate and the solute concentration of the solution, and make the particle size of the formed tungstic acid more uniform. Specifically, the addition rate of the sodium tungstate-ammonium tungstate mixed solution A can be any one or the range between any two of, for example, 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, 11 mL / min, 12 mL / min, 13 mL / min, 14 mL / min, 15 mL / min, 16 mL / min, 17 mL / min; the stirring time after the addition of the sodium tungstate-ammonium tungstate mixed solution A is completed can be any one or the range between any two of 2 min, 3 min, 4 min, 5 min. The volume of the sodium tungstate-ammonium tungstate mixed solution A can be any one or the range between any two of, for example, 50 mL, 60 mL, 70 mL, 80 mL, 90 mL, 100 mL, 110 mL, 120 mL, 130 mL, 140 mL, 150 mL, 160 mL, 170 mL, 180 mL, 190 mL, 200 mL. The dosage of hydrochloric acid can be any one or the range between any two of 2.2 times, 2.3 times, 2.4 times, 2.5 times, 2.6 times of the theoretical amount of dilute hydrochloric acid required to prepare tungstic acid according to the tungstate ion concentration in the ammonium tungstate solution A.

[0019] Preferably, in the step S4, repeat 3-9 times and then proceed to step S5. Specifically, the number of repetitions can be 3, 4, 5, 6, 7, 8, 9.

[0020] Preferably, in the step S5, the concentration of hydrochloric acid is 2 wt%, wash 2-4 times, and the drying temperature is 100-120 °C. Adopting a relatively high drying temperature, at this drying temperature, it is beneficial to the volatilization of the residual hydrochloric acid in the tungstic acid, but if the temperature is too high, the water evaporates too fast and it is not easy to obtain loose tungstic acid. Specifically, the drying temperature can be any one or the range between any two of, for example, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C.

[0021] According to another aspect of the present invention, the present invention provides the following technical solution: A nano-tungstic acid with a multi-stage structure is prepared by using the preparation method of the nano-tungstic acid with a multi-stage structure as described above. The nano-tungstic acid with a multi-stage structure includes massive tungstic acid and fluffy spherical tungstic acid, and the specific surface area is 50-75 m 2 / g.

[0022] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0023] Example 1 A preparation method of nano tungstic acid with a multi-level structure includes the following steps: S1. Add hydrochloric acid to a container, continuously stir during the addition process, and keep the temperature in the container stable. S2. Drop 2 mL of sodium tungstate-ammonium tungstate mixed solution B into the container, continuously stir during the addition process, and keep the temperature in the container stable. S3. Add 100 mL of sodium tungstate-ammonium tungstate mixed solution A to the container, continuously stir during the addition process, and keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 2.5 times the theoretical amount of hydrochloric acid required to prepare tungstic acid according to the tungstate ion concentration in the sodium tungstate-ammonium tungstate mixed solution A. S4. Repeat steps S1 and S3. S5. Filter the obtained tungstic acid, wash it with hydrochloric acid, and then dry it to obtain nano tungstic acid with a multi-level structure.

[0024] In steps S1-S3, the temperature in the container is 95 °C, and the stirring speed is 200 r / min. In step S1, the concentration of hydrochloric acid is 18 wt%; in steps S2-S3, both the sodium tungstate-ammonium tungstate mixed solution A and the sodium tungstate-ammonium tungstate mixed solution B are prepared by mixing ammonium tungstate solution and sodium tungstate solution with the same concentration calculated by WO 3 and the volume ratio of ammonium tungstate solution to sodium tungstate solution is 1:1; among them, in step S2, calculated by WO 3 the concentration of the sodium tungstate-ammonium tungstate mixed solution B is 250 g / L; in step S3, calculated by WO 3 the concentration of the sodium tungstate-ammonium tungstate mixed solution A is 250 g / L. In step S2, after dropping 2 mL of the sodium tungstate-ammonium tungstate mixed solution B into the container, stir for 10 min; the addition rate of the sodium tungstate-ammonium tungstate mixed solution B is 3 mL / min. The sodium tungstate-ammonium tungstate mixed solution A is added using a peristaltic pump; the addition rate of the sodium tungstate-ammonium tungstate mixed solution A is 10 mL / min; after the addition of the sodium tungstate-ammonium tungstate mixed solution A is completed, stir for 3 min and then proceed to step S4. In step S4, repeat 5 times and then proceed to step S5. In step S5, the concentration of hydrochloric acid is 2 wt%, wash 3 times, and the drying temperature is 120 °C.

[0025] The nano tungstic acid obtained in this example is as Figure 1 shown, in which there are two morphologies of tungstic acid, blocky and fluffy spherical, and its BET is 62.97 m 2 / g.

[0026] Example 2 A preparation method of nano tungstic acid with a multi - level structure, comprising the following steps: S1. Add hydrochloric acid to a container, continuously stir during the addition process and keep the temperature in the container stable; S2. Drop 5 mL of sodium tungstate - ammonium tungstate mixed solution B into the container, continuously stir during the addition process and keep the temperature in the container stable; S3. Add 125 mL of sodium tungstate - ammonium tungstate mixed solution A to the container, continuously stir during the addition process and keep the temperature in the container stable; The amount of hydrochloric acid added in step S1 is 2.2 times the theoretical amount of hydrochloric acid required to prepare tungstic acid according to the tungstate ion concentration in sodium tungstate - ammonium tungstate mixed solution A; S4. Repeat steps S1 and S3; S5. Filter the obtained tungstic acid, wash it with hydrochloric acid and then dry it to obtain nano tungstic acid with a multi - level structure.

[0027] In the above steps S1 - S3, the temperature in the container is 95 °C and the stirring speed is 200 r / min. In step S1, the concentration of hydrochloric acid is 22 wt%; In steps S2 - S3, both sodium tungstate - ammonium tungstate mixed solution A and sodium tungstate - ammonium tungstate mixed solution B are prepared by mixing ammonium tungstate solution and sodium tungstate solution with the same concentration calculated based on WO 3 and the volume ratio of ammonium tungstate solution to sodium tungstate solution is 1:0.33; Among them, in step S2, calculated based on WO 3 the concentration of sodium tungstate - ammonium tungstate mixed solution B is 250 g / L; In step S3, calculated based on WO 3 the concentration of sodium tungstate - ammonium tungstate mixed solution A is 250 g / L. In step S2, after dropping 5 mL of sodium tungstate - ammonium tungstate mixed solution B into the container, stir for 10 min; The addition speed of sodium tungstate - ammonium tungstate mixed solution B is 5 mL / min. Sodium tungstate - ammonium tungstate mixed solution A is added using a peristaltic pump; The addition speed of sodium tungstate - ammonium tungstate mixed solution A is 12.5 mL / min; After the addition of sodium tungstate - ammonium tungstate mixed solution A is completed, stir for 3 min and then proceed to step S4. In step S4, repeat 4 times and then proceed to step S5. In step S5, the concentration of hydrochloric acid is 2 wt%, wash 3 times, and the drying temperature is 120 °C.

[0028] The nano tungstic acid obtained in this example is as Figure 2 shown, in which there are two morphologies of tungstic acid, block - shaped and fluffy - ball - shaped, and its BET is 74.24 m 2 / g.

[0029] Example 3 A preparation method of nano tungstic acid with a multi - level structure, comprising the following steps: S1. Add hydrochloric acid to the container, continuously stir during the addition process and keep the temperature inside the container stable. S2. Drop 4 mL of mixed solution B of sodium tungstate - ammonium tungstate into the container, continuously stir during the addition process and keep the temperature inside the container stable. S3. Add 167 mL of mixed solution A of sodium tungstate - ammonium tungstate to the container, continuously stir during the addition process and keep the temperature inside the container stable; the amount of hydrochloric acid added in step S1 is 2.6 times the theoretical amount of hydrochloric acid required to prepare tungstic acid according to the concentration of tungstate in the mixed solution A of sodium tungstate - ammonium tungstate. S4. Repeat steps S1 and S3. S5. Filter the obtained tungstic acid, wash it with hydrochloric acid and then dry it to obtain nano - sized tungstic acid with a hierarchical structure.

[0030] In steps S1 - S3, the temperature inside the container is 90 °C and the stirring speed is 200 r / min. In step S1, the concentration of hydrochloric acid is 16 wt%; in steps S2 - S3, both the mixed solution A of sodium tungstate - ammonium tungstate and the mixed solution B of sodium tungstate - ammonium tungstate are prepared by mixing ammonium tungstate solution and sodium tungstate solution with the same concentration calculated based on WO 3 and the volume ratio of ammonium tungstate solution to sodium tungstate solution is 1:1.5; among them, in step S2, calculated based on WO 3 the concentration of the mixed solution B of sodium tungstate - ammonium tungstate is 250 g / L; in step S3, calculated based on WO 3 the concentration of the mixed solution A of sodium tungstate - ammonium tungstate is 250 g / L. In step S2, after dropping 4 mL of the mixed solution B of sodium tungstate - ammonium tungstate into the container, stir for 10 min; the addition rate of the mixed solution B of sodium tungstate - ammonium tungstate is 4 mL / min. The mixed solution A of sodium tungstate - ammonium tungstate is added using a peristaltic pump; the addition rate of the mixed solution A of sodium tungstate - ammonium tungstate is 16.67 mL / min; after the addition of the mixed solution A of sodium tungstate - ammonium tungstate is completed, stir for 3 min and then proceed to step S4. In step S4, repeat 3 times and then proceed to step S5. In step S5, the concentration of hydrochloric acid is 2 wt%, wash 3 times, and the drying temperature is 100 °C.

[0031] The nano - sized tungstic acid obtained in this example is as Figure 3 shown, in which there are two morphologies of tungstic acid, block - shaped and flocculent - spherical, and its BET is 55.86 m 2 / g.

[0032] Comparative Example 1 The difference from Example 1 is that in steps S1 - S3, the temperature inside the container is 70 °C.

[0033] The tungstic acid obtained in this comparative example is as Figure 4As shown, all tungstic acids are incompletely developed flakes, without completely developed massive tungstic acid and fluffy spherical ultrafine tungstic acid, and its BET is 47.6m 2 / g.

[0034] Comparative Example 2 The difference from Example 1 is that step S2 is not carried out.

[0035] The tungstic acid obtained in this comparative example is as Figure 5 shown. All tungstic acids are flakes, and some of the flaky tungstic acids are completely developed, without fluffy spherical ultrafine tungstic acid, and its BET is 36.49m 2 / g.

[0036] Comparative Example 3 The difference from Example 1 is that hydrochloric acid and the sodium tungstate-ammonium tungstate mixed solution A are not added in a segmented and alternating manner: that is, all hydrochloric acid is added first, and then the sodium tungstate-ammonium tungstate mixed solution B is dropped and then all the sodium tungstate-ammonium tungstate mixed solution A is added.

[0037] The tungstic acid obtained in this comparative example is as Figure 6 shown. The tungstic acid is uneven flakes, and its BET is 60.12m 2 / g.

[0038] Comparative Example 4 The difference from Example 1 is that in steps S2 - S3, both the sodium tungstate-ammonium tungstate mixed solution A and the sodium tungstate-ammonium tungstate mixed solution B are made by mixing an ammonium tungstate solution and a sodium tungstate solution with the same concentration calculated based on WO 3 and the volume ratio of the ammonium tungstate solution to the sodium tungstate solution is 9:1.

[0039] The tungstic acid obtained in this comparative example is as Figure 7 shown, in which there is tungstic acid formed into fluffy spheres and a small amount of tungstic acid with extremely incomplete development covering the surface of some of the fluffy spherical tungstic acid, and its BET is 83.72m 2 / g.

[0040] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made using the content of the specification of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for preparing nano-tungstic acid with a multi-level structure, characterized in that: The steps include: S1. Add hydrochloric acid to the container, stirring continuously during the addition process and keeping the temperature in the container stable; S2. Add 2-5 mL of sodium tungstate-ammonium tungstate mixed solution B to the container, stirring continuously and keeping the temperature in the container stable during the addition process; S3, add 50-200 mL of sodium tungstate-ammonium tungstate mixed solution A to the container, stir continuously during the addition process and keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 2.2-2.6 times the theoretical amount of hydrochloric acid required for preparing tungstic acid according to the tungstate concentration in the sodium tungstate-ammonium tungstate mixed solution A; S4, repeat steps S1 and S3; S5. Filter the prepared tungstic acid, wash it with hydrochloric acid, and then dry it to obtain nano tungstic acid with a multi-level structure.

2. The method for preparing nano-tungstic acid with a multi-level structure according to claim 1, characterized in that: In the steps S1-S3, the temperature in the container is 80-100° C., and the stirring speed is 150-250 r / min.

3. The method for preparing nano-tungstic acid with a multi-level structure according to claim 1, characterized in that: In step S1, the concentration of hydrochloric acid is 16-22 wt %.

4. The method for preparing nano-tungstic acid with a multi-level structure according to claim 1, characterized in that: In the steps S2-S3, the sodium tungstate-ammonium tungstate mixed solution A and the sodium tungstate-ammonium tungstate mixed solution B are both prepared by mixing an ammonium tungstate solution and a sodium tungstate solution having the same concentration in terms of WO3, and the volume ratio of the ammonium tungstate solution to the sodium tungstate solution is 1:(0.25-4); wherein, in the step S2, the concentration of the sodium tungstate-ammonium tungstate mixed solution B is 240-260 g / L in terms of WO3; and in the step S3, the concentration of the sodium tungstate-ammonium tungstate mixed solution A is 240-260 g / L in terms of WO3.

5. The method for preparing nano-tungstic acid with a multi-level structure according to claim 1, characterized in that: In the step S2, 2-5 mL of the sodium tungstate-ammonium tungstate mixed solution B is dripped into the container and stirred for 8-12 minutes; the addition rate of the sodium tungstate-ammonium tungstate mixed solution B is 3-5 mL / min.

6. The method for preparing nano-tungstic acid with a multi-level structure according to claim 1, characterized in that: In the step S3, the sodium tungstate-ammonium tungstate mixed solution A is added by a peristaltic pump; the addition rate of the sodium tungstate-ammonium tungstate mixed solution A is 5-17 mL / min; after the sodium tungstate-ammonium tungstate mixed solution A is added, it is stirred for 2-5 minutes before performing step S4.

7. The method for preparing nano-tungstic acid with a multi-level structure according to claim 1, characterized in that: In the step S4, step S5 is performed after repeating 3 to 9 times.

8. The method for preparing nano-tungstic acid with a multi-level structure according to claim 1, characterized in that: In step S5, the concentration of hydrochloric acid is 2 wt %, washing is performed 2 to 4 times, and the drying temperature is 100 to 120° C.

9. A nano-tungstic acid with a multi-level structure, characterized in that: The nano-tungstic acid with a multi-level structure is prepared by the preparation method of any one of claims 1 to 8.

10. The nano-tungstic acid with a multi-level structure according to claim 9, characterized in that: The nano-tungstic acid with a multi-level structure includes block-shaped tungstic acid and floc-shaped tungstic acid, and the specific surface area is 50-75m 2 / g.

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