A nano-tungstic acid with a multi-level structure and a preparation method thereof

Abstract

The present invention belongs to the technical field of tungsten metallurgy, and particularly relates to a nano tungsten acid with a multi-stage structure and a preparation method thereof. The preparation method includes: S1. Add hydrochloric acid to a container, and continuously stir during the addition process to keep the temperature in the container stable; S2. Drop 2-5 mL of a sodium tungstate-ammonium tungstate mixed solution B into the container, and continuously stir during the addition process to keep the temperature in the container stable; S3. Add 50-200 mL of a sodium tungstate-ammonium tungstate mixed solution A to the container, and continuously stir during the addition process to 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 prepared tungstic acid, wash it with hydrochloric acid, and then dry it to obtain a nano tungsten acid with a multi-stage structure. The nano tungsten acid with a multi-stage structure includes massive tungstic acid and flocculent tungstic acid, and the specific surface area is 50-75 m<supgt;2< / supgt> / g.

Description

Technical Field

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

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

[0003] Nano-tungstic acid (H2WO4) 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, ideal materials must necessarily take into account the efficiency of both reaction and mass transfer. At present, a lot of research has proved that nano-level tungstic acid has excellent performance in many fields. Scientific researchers around the world have prepared multi-stage nano-tungstic 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 and other aspects. However, these methods have problems such as high requirements for production equipment, high cost, and low production efficiency, which make it difficult to industrialize them. Summary of the Invention

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

[0005] According to one aspect of the present invention, the following technical solution is provided:

[0006] A preparation method of a nano-tungstic acid with a multi-stage structure, comprising the following steps:

[0007] S1. Add hydrochloric acid to a container, continuously stir during the addition process and keep the temperature in the container stable;

[0008] 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;

[0009] 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.

[0010] S4. Repeat steps S1 and S3;

[0011] S5. Filter the obtained tungstic acid, wash it with hydrochloric acid, and then dry it to obtain nano-tungstic acid with a hierarchical structure.

[0012] According to another aspect of the present invention, the present invention provides the following technical solution:

[0013] 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 fluffy spherical tungstic acid, and the specific surface area is 50-75 m 2 / g.

[0014] The beneficial effects of the present invention are as follows:

[0015] The present invention provides a nano-tungstic acid with a hierarchical structure and a preparation method thereof. By using the precipitation method, a multi-level structure nano-tungstic acid assembled from 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 a mixed solution A of sodium tungstate-ammonium tungstate 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 fluffy spherical tungstic acid, and the specific surface area is 50-75 m 2 / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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 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, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0017] Figure 1 It is the electron microscope image of the nano-tungstic acid prepared in Example 1 of the present invention;

[0018] Figure 2 It is the electron microscope image of the nano-tungstic acid prepared in Example 2 of the present invention;

[0019] Figure 3 It is the electron microscope image of the nano-tungstic acid prepared in Example 3 of the present invention;

[0020] Figure 4 It is the electron microscope image of the tungstic acid prepared in Comparative Example 1 of the present invention;

[0021] Figure 5 It is the electron microscope image of the tungstic acid prepared in Comparative Example 2 of the present invention;

[0022] Figure 6 Electron micrograph of tungstic acid prepared in Comparative Example 3 of the present invention;

[0023] Figure 7 Electron micrograph of tungstic acid prepared in Comparative Example 4 of the present invention.

[0024] The realization, functional features and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed implementation manners

[0025] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. 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.

[0026] In the method for preparing materials, the precipitation method has simple operation and convenient reaction control, and is the most easily industrialized preparation method. Therefore, the present invention adopts the precipitation method to construct a multi-level structured 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.

[0027] According to one aspect of the present invention, the present invention provides the following technical solution:

[0028] A method for preparing nano-tungstic acid with a multi-level structure, comprising the following steps:

[0029] S1. Add hydrochloric acid to a container, continuously stir during the addition process and keep the temperature in the container stable;

[0030] S2. Drop 2-5 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;

[0031] S3. Add 50-200 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 2.2-2.6 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;

[0032] S4. Repeat steps S1 and S3;

[0033] 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.

[0034] Preferably, in the steps S1-S3, the temperature in the container is 80-100 °C, and the stirring speed is 150-250 r / min. The temperature will affect the morphology of tungstic acid prepared from ammonium tungstate and sodium tungstate. At low temperatures, tungstic acid prepared from ammonium tungstate will form large flakes, while tungstic acid prepared from sodium tungstate is incompletely developed. Specifically, the temperature in the container can be, for example, any one of 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 prone to be broken, with poor crystal form and poor uniformity. Specifically, the stirring speed can be, for example, any one of 150 r / min, 175 r / min, 200 r / min, 225 r / min, 250 r / min or the range between any two of them.

[0035] 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, for example, any one of 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.

[0036] 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 an ammonium tungstate solution and a sodium tungstate solution with 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, in terms of WO3, the concentration of the sodium tungstate - ammonium tungstate mixed solution B is 240 - 260 g / L; in the step S3, in terms of WO3, the concentration of the sodium tungstate - ammonium tungstate mixed solution A is 240 - 260 g / L. Sodium ions and ammonium ions will generate tungstic acids with different morphologies during preparation. Among them, sodium tungstate generates blocky 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 blocky tungstic acid to flocculent tungstic acid also changes. Specifically, the volume ratio of the ammonium tungstate solution to the sodium tungstate solution with the same concentration in terms of WO3 can be, for example, any one of 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 and the concentration of the sodium tungstate - ammonium tungstate mixed solution A can be the same or different. The concentration of the sodium tungstate - ammonium tungstate mixed solution B can be, for example, any one of 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, for example, any one of 240 g / L, 245 g / L, 250 g / L, 255 g / L, 260 g / L or the range between any two of them.

[0037] 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 role 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 crystal to be controlled within a certain range. Too much or too little will lose the meaning of adding the seed crystal, 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.

[0038] Preferably, in step S3, 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 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.

[0039] Preferably, in 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.

[0040] Preferably, in 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 is beneficial to the volatilization of the residual hydrochloric acid in tungstic acid at this drying temperature, 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.

[0041] According to another aspect of the present invention, the present invention provides the following technical solution:

[0042] A nano-tungstic acid with a multi-level structure is prepared by using the preparation method of the nano-tungstic acid with a multi-level structure as described above. The nano-tungstic acid with a multi-level structure includes massive tungstic acid and flocculent tungstic acid, and the specific surface area is 50-75 m2 / g.

[0043] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0044] Example 1

[0045] A preparation method of nano tungstic acid with a multi-stage structure includes the following steps:

[0046] S1. Add hydrochloric acid to a container, and continuously stir during the addition process to keep the temperature in the container stable.

[0047] S2. Drop 2 mL of sodium tungstate-ammonium tungstate mixed solution B into the container, and continuously stir during the addition process to keep the temperature in the container stable.

[0048] S3. Add 100 mL of sodium tungstate-ammonium tungstate mixed solution A to the container, and continuously stir during the addition process to 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.

[0049] S4. Repeat steps S1 and S3.

[0050] S5. Filter the prepared tungstic acid, wash it with hydrochloric acid, and then dry it to obtain nano tungstic acid with a multi-stage structure.

[0051] 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 an ammonium tungstate solution and a sodium tungstate solution with the same concentration in terms of WO3, and the volume ratio of the ammonium tungstate solution to the sodium tungstate solution is 1:1; among them, in step S2, the concentration of the sodium tungstate-ammonium tungstate mixed solution B in terms of WO3 is 250 g / L; in step S3, the concentration of the sodium tungstate-ammonium tungstate mixed solution A in terms of WO3 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.

[0052] The nano tungstic acid obtained in this example is as Figure 1As shown, there are two morphologies of tungstic acid, blocky and fluffy spherical, with a BET of 62.97 m 2 / g.

[0053] Example 2

[0054] A preparation method of nano-tungstic acid with a multi-level structure, comprising the following steps:

[0055] S1. Add hydrochloric acid to a container, continuously stir during the addition process and keep the temperature in the container stable;

[0056] 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;

[0057] 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 the sodium tungstate-ammonium tungstate mixed solution A;

[0058] S4. Repeat steps S1 and S3;

[0059] 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.

[0060] 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 the sodium tungstate-ammonium tungstate mixed solution A and the sodium tungstate-ammonium tungstate mixed solution B are prepared by mixing an ammonium tungstate solution and a sodium tungstate solution with the same concentration in terms of WO3, and the volume ratio of the ammonium tungstate solution to the sodium tungstate solution is 1:0.33; among them, in step S2, the concentration of the sodium tungstate-ammonium tungstate mixed solution B in terms of WO3 is 250 g / L; in step S3, the concentration of the sodium tungstate-ammonium tungstate mixed solution A in terms of WO3 is 250 g / L. In step S2, after dropping 5 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 5 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 12.5 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 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.

[0061] The nano-tungstic acid obtained in this example is as Figure 2As shown, there are two morphologies of tungstic acid, namely blocky and fluffy spherical, and its BET is 74.24m 2 / g.

[0062] Example 3

[0063] A preparation method of nano-tungstic acid with a multi-level structure, comprising the following steps:

[0064] S1. Add hydrochloric acid to a container, and continuously stir during the addition process to keep the temperature in the container stable;

[0065] S2. Drop 4 mL of sodium tungstate-ammonium tungstate mixed solution B into the container, and continuously stir during the addition process to keep the temperature in the container stable;

[0066] S3. Add 167 mL of sodium tungstate-ammonium tungstate mixed solution A to the container, and continuously stir during the addition process to keep the temperature in 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 tungstate ion concentration in the sodium tungstate-ammonium tungstate mixed solution A;

[0067] S4. Repeat steps S1 and S3;

[0068] 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.

[0069] In the above steps S1-S3, the temperature in 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 sodium tungstate-ammonium tungstate mixed solution A and the sodium tungstate-ammonium tungstate mixed solution B are prepared by mixing an ammonium tungstate solution and a sodium tungstate solution with the same concentration in terms of WO3, and the volume ratio of the ammonium tungstate solution to the sodium tungstate solution is 1:1.5; among them, in step S2, the concentration of the sodium tungstate-ammonium tungstate mixed solution B is 250 g / L in terms of WO3; in step S3, the concentration of the sodium tungstate-ammonium tungstate mixed solution A is 250 g / L in terms of WO3. In step S2, after dropping 4 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 4 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 16.67 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 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.

[0070] The nano-tungstic acid obtained in this example is as Figure 3As shown, there are two morphologies of tungstic acid, namely massive and fluffy spherical, with a BET of 55.86 m 2 / g.

[0071] Comparative Example 1

[0072] The difference from Example 1 is that in steps S1 - S3, the temperature inside the container is 70 °C.

[0073] The tungstic acid obtained in this comparative example is as Figure 4 shown. The tungstic acid is all incompletely developed flaky, without completely developed massive tungstic acid and fluffy spherical ultrafine tungstic acid, and its BET is 47.6 m 2 / g.

[0074] Comparative Example 2

[0075] The difference from Example 1 is that step S2 is not carried out.

[0076] The tungstic acid obtained in this comparative example is as Figure 5 shown. The tungstic acid is all flaky, and some of the flaky tungstic acid is completely developed, without fluffy spherical ultrafine tungstic acid, and its BET is 36.49 m 2 / g.

[0077] Comparative Example 3

[0078] 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 the hydrochloric acid is added first, and then the sodium tungstate - ammonium tungstate mixed solution B is dropped in and then all the sodium tungstate - ammonium tungstate mixed solution A is added.

[0079] The tungstic acid obtained in this comparative example is as Figure 6 shown. The tungstic acid is unevenly flaky, and its BET is 60.12 m 2 / g.

[0080] Comparative Example 4

[0081] 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 prepared by mixing ammonium tungstate solution and sodium tungstate solution with the same concentration in terms of WO3, and the volume ratio of the ammonium tungstate solution to the sodium tungstate solution is 9:1.

[0082] The tungstic acid obtained in this comparative example is as Figure 7 shown. Among them, there is tungstic acid in the form of fluffy spheres and a small amount of extremely incompletely developed tungstic acid covering the surface of some fluffy - sphere tungstic acid, and its BET is 83.72 m 2 / g.

[0083] 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 preparation method of nano-tungstic acid with a multi-level structure, characterized in that, It includes the following steps: S1. Add hydrochloric acid into the container, continuously stir during the adding process and keep the temperature in the container stable; S2. Drop 2 - 5 mL of sodium tungstate - ammonium tungstate mixed solution B into the container, continuously stir during the adding process and keep the temperature in the container stable; after dropping 2 - 5 mL of sodium tungstate - ammonium tungstate mixed solution B into the container, stir for 8 - 12 min; the adding speed of sodium tungstate - ammonium tungstate mixed solution B is 3 - 5 mL / min; S3. Add 50 - 200 mL of sodium tungstate - ammonium tungstate mixed solution A into the container, continuously stir during the adding process and keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 2.2 - 2.6 times of 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 prepared tungstic acid, wash it with hydrochloric acid and then dry it to obtain nano - tungstic acid with a hierarchical structure, and the nano - tungstic acid with a hierarchical structure includes massive tungstic acid and flocculent tungstic acid; In steps S1 - S3, the temperature in the container is 80 - 100 °C; 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 as WO3, and the volume ratio of ammonium tungstate solution to sodium tungstate solution is 1:(0.25 - 4).

2. The preparation method of the nano tungstic acid with a multi-level structure according to claim 1, characterized in that, In steps S1 - S3, the stirring speed is 150 - 250 r / min.

3. The preparation method of nano tungsten acid with a multi-stage structure according to claim 1, characterized in that, In step S1, the concentration of hydrochloric acid is 16 - 22 wt%.

4. The preparation method of the nano tungsten acid with a multi-level structure according to claim 1, characterized in that, In step S2, calculated as WO3, the concentration of sodium tungstate - ammonium tungstate mixed solution B is 240 - 260 g / L; in step S3, calculated as WO3, the concentration of sodium tungstate - ammonium tungstate mixed solution A is 240 - 260 g / L.

5. The preparation method of the nano-tungstic acid with a multi-level structure according to claim 1, characterized in that, In step S3, sodium tungstate - ammonium tungstate mixed solution A is added by a peristaltic pump; the adding speed of sodium tungstate - ammonium tungstate mixed solution A is 5 - 17 mL / min; after adding sodium tungstate - ammonium tungstate mixed solution A is completed, stir for 2 - 5 min and then proceed to step S4.

6. The preparation method of the nano-tungstic acid with a multi-level structure according to claim 1, characterized in that, In step S4, repeat 3 - 9 times and then proceed to step S5.

7. The preparation method of the nano tungstic acid with a multi-stage structure according to claim 1, characterized in that, In step S5, the concentration of hydrochloric acid is 2 wt%, wash 2 - 4 times, and the drying temperature is 100 - 120 °C.

8. A nano tungsten acid with a multi - level structure, characterized in that, Prepared by using the preparation method of nano - tungstic acid with a hierarchical structure according to any one of claims 1 - 7.

9. The nano-tungstic acid with a multi-level structure according to claim 8, wherein, The specific surface area of the nano-tungstic acid with a multi-level structure is 50-75 m 2 / g.

Images