Method for reducing water content of tungstic acid

Abstract

The invention belongs to the technical field of tungsten metallurgy, and particularly relates to a method for reducing the water content of tungstic acid, which comprises the following steps: S1, heating a container filled with a sodium tungstate solution in a water bath kettle, stirring the sodium tungstate solution, and adding ethanol; s2, adding hydrochloric acid into the sodium tungstate solution added with the ethanol, adjusting the pH value of the solution, monitoring in real time in the reaction process to ensure that the pH value of the solution is stable, stopping heating to naturally cool the solution to an aging temperature for constant-temperature aging, and then filtering and washing; and S3, drying to obtain tungstic acid. The water content of the tungstic acid obtained after filtering and washing is less than or equal to 30wt%.

Description

Technical Field

[0001] The invention belongs to the technical field of tungsten metallurgy, and in particular relates to a method for reducing the water content of tungstic acid. Background Art

[0002] Tungstic acid (H 2 WO 4 ) is an important inorganic compound with high chemical stability, strong acidity, excellent photocatalytic performance and unique semiconductor properties. Its high density and high temperature resistance make it the core precursor for the preparation of materials such as metallic tungsten and tungsten carbide. It is widely used in catalysts, ceramic industry, electronic materials and other fields. In terms of catalysis, tungstic acid is used in environmental protection fields such as petroleum refining desulfurization and automobile exhaust purification; in the field of materials, its derivatives can be made into wear-resistant ceramics, fire-resistant coatings and dielectric materials; in recent years, its photocatalytic properties have shown potential in new energy fields such as solar water decomposition to produce hydrogen and lithium-ion battery electrode materials. In addition, tungstic acid-based composite materials have also attracted much attention in cutting-edge technologies such as photochromism and gas sensing.

[0003] The preparation methods of tungstic acid mainly include acid neutralization method, hydrothermal synthesis method, etc. The acid neutralization method generates precipitation by reacting strong acid (such as hydrochloric acid) with sodium tungstate solution. The process is simple but easy to introduce impurities; the hydrothermal synthesis method regulates the crystal morphology through high temperature and high pressure, which can improve the purity and performance of the product. In the preparation process, due to inadequate process control, it is easy to cause problems such as tungstic acid gelation and high water content, which leads to long drying time, high energy consumption and serious material compaction. Therefore, it is particularly important to develop a method to reduce the water content of tungstic acid. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a method for reducing the water content of tungstic acid.

[0005] According to one aspect of the present invention, the present invention provides the following technical solution: A method for reducing the water content of tungstic acid comprises the following steps: S1. Place the container containing the sodium tungstate solution in a water bath and heat it, stir the sodium tungstate solution and add ethanol; S2. Add hydrochloric acid to the sodium tungstate solution added with ethanol, adjust the pH value of the solution and monitor in real time during the reaction to ensure that the pH value of the solution is stable. After the reaction is completed, turn off the heating to allow the solution to cool naturally to the aging temperature for constant temperature aging, and then filter and wash; S3. After drying, tungstic acid is obtained.

[0006] As a preferred embodiment of the method for reducing the water content of tungstic acid described in the present invention, wherein: in step S1, WO 3 The concentration of sodium tungstate solution is 250~300g / L.

[0007] As a preferred embodiment of the method for reducing the water content of tungstic acid described in the present invention, in step S1, the heating temperature is 85-95°C.

[0008] As a preferred embodiment of the method for reducing the water content of tungstic acid described in the present invention, in step S1, the volume of ethanol is 3-6% of the volume of the sodium tungstate solution.

[0009] As a preferred embodiment of the method for reducing the water content of tungstic acid described in the present invention, in step S2, the concentration of hydrochloric acid is 12-16wt%.

[0010] As a preferred embodiment of the method for reducing the water content of tungstic acid described in the present invention, in step S2, the pH of the solution is adjusted to 0.4-0.8.

[0011] As a preferred embodiment of the method for reducing the water content of tungstic acid described in the present invention, in step S2, the pH of the solution is adjusted and monitored in real time, and hydrochloric acid is added in time when the pH of the solution is not satisfied to compensate for the decrease in acid concentration caused by volatilization or reaction at high temperature.

[0012] As a preferred embodiment of the method for reducing the water content of tungstic acid described in the present invention, in step S2, according to experience, the reaction ends after stirring for 10 to 30 minutes after adding hydrochloric acid, and then the heating is turned off.

[0013] As a preferred embodiment of the method for reducing the water content of tungstic acid described in the present invention, in step S2, the aging temperature is 60-75° C. and the aging time is 1-3 hours.

[0014] As a preferred embodiment of the method for reducing the water content of tungstic acid described in the present invention, wherein: in the step S2, the water content of the tungstic acid obtained after filtering and washing is ≤30wt%.

[0015] The beneficial effects of the present invention are as follows: The present invention proposes a method for reducing the water content of tungstic acid, comprising the following steps: S1, placing a container containing a sodium tungstate solution in a water bath for heating, stirring the sodium tungstate solution and adding ethanol; S2, adding hydrochloric acid to the sodium tungstate solution added with ethanol, adjusting the pH of the solution and monitoring in real time during the reaction to ensure that the pH of the solution is stable, turning off the heating after the reaction is completed to allow the solution to naturally cool to an aging temperature for constant temperature aging, and then filtering and washing; S3, drying to obtain tungstic acid. The water content of the tungstic acid obtained after filtration and washing in the present invention is ≤30wt%. DETAILED DESCRIPTION

[0016] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The invention provides a method for reducing the water content of tungstic acid, so as to solve the problems that in the current tungstic acid preparation process, due to inadequate process control, tungstic acid gelation and high water content are easily caused, thereby reducing the energy consumption of tungstic acid drying and the degree of material compaction.

[0018] According to one aspect of the present invention, the present invention provides the following technical solution: A method for reducing the water content of tungstic acid comprises the following steps: S1. Place the container containing the sodium tungstate solution in a water bath and heat it, stir the sodium tungstate solution and add ethanol; S2. Add hydrochloric acid to the sodium tungstate solution added with ethanol, adjust the pH value of the solution and monitor in real time during the reaction to ensure that the pH value of the solution is stable. After the reaction is completed, turn off the heating to allow the solution to cool naturally to the aging temperature for constant temperature aging, and then filter and wash; S3. After drying, tungstic acid is obtained.

[0019] Preferably, in step S1, WO 3 The concentration of sodium tungstate solution is 250-300g / L. Using this concentration of sodium tungstate as raw material to prepare tungstic acid can promote the deposition and growth of tungstic acid particles, promote the complete development of grains and form a denser precipitation, and reduce the water inclusion in the crystal gap. 3 The concentration of the sodium tungstate solution can be, for example, any one of 250 g / L, 260 g / L, 270 g / L, 280 g / L, 290 g / L, 300 g / L, or a range between any two of them.

[0020] Preferably, in step S1, the heating temperature is 85-95°C. At high temperature, the tungstic acid grains develop more completely, which can effectively reduce the crystal water contained in the crystals. If the temperature is too high, the volatilization amount is large, the acid loss is large, and the equipment energy consumption is high. If the temperature is low, the grains are not fully developed and the water content of tungstic acid is high. Specifically, the heating temperature can be, for example, any one of 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C or any range between two thereof.

[0021] Preferably, in step S1, the volume of ethanol is 3-6% of the volume of the sodium tungstate solution. Adding organic solvent ethanol as a dispersant can reduce the dielectric constant of the solution and reduce the adsorption of water molecules on the crystal surface. And ethanol evaporates during the later drying process and will not pollute the material. Specifically, the volume of ethanol can be any one of 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6% of the volume of the sodium tungstate solution or a range between any two thereof.

[0022] Preferably, in step S2, the concentration of hydrochloric acid is 12-16wt%. The use of hydrochloric acid of this concentration is conducive to reducing local overacidity when hydrochloric acid is added, reducing the number of instantaneous nuclei, promoting the deposition and growth of tungstic acid particles, promoting the complete development of grains and the formation of denser precipitation, and reducing the water inclusion in the crystal gap. Specifically, the concentration of hydrochloric acid can be, for example, any one of 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, or the range between any two.

[0023] Preferably, in step S2, the pH of the solution is adjusted to 0.4-0.8. When the pH is controlled at 0.4-0.8, the prepared tungstic acid is mainly monoclinic tungstic acid, and its crystal water content is low. If the pH is too low, the tungstic acid is easy to gel and has strong water absorption; if the pH is high, it is easy to produce highly hydrated amorphous tungstic acid with high water content. Specifically, the pH of the solution is adjusted to any one of 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8 or the range between any two.

[0024] Preferably, in step S2, the pH of the solution is adjusted and monitored in real time, and hydrochloric acid is added in time when the pH of the solution is not satisfied to compensate for the decrease in acid concentration caused by volatilization or reaction at high temperature.

[0025] Preferably, in step S2, according to experience, the reaction ends after stirring for 10 to 30 minutes after adding hydrochloric acid, and then the heating is turned off. Specifically, the stirring time can be any one of 10 minutes, 15 minutes, 20 minutes, 25 minutes, and 30 minutes, or a range between any two of them.

[0026] Preferably, in step S2, the aging temperature is 60-75°C, and the aging time is 1-3h. High temperature constant temperature aging can promote the rearrangement of the crystal structure, release part of the crystal water and promote further development of the grains. Specifically, the aging temperature can be, for example, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, any one or any two of the range, and the aging time can be, for example, 1h, 1.5h, 2h, 2.5h, 3h, any one or any two of the range.

[0027] Preferably, in step S2, the water content of the tungstic acid obtained after filtering and washing is ≤30wt%. In the present invention, the mass reduction ratio of tungstic acid before and after drying is used as the water content ratio of the tungstic acid obtained after filtering and washing, and the drying is completed when the mass of the tungstic acid does not change within a period of time.

[0028] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0029] Example 1 A method for reducing the water content of tungstic acid comprises the following steps: S1. Place the container containing sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol. 3 The concentration of sodium tungstate solution is 250g / L; the heating temperature is 85℃; the volume of ethanol is 3% of the volume of sodium tungstate solution; S2. Add hydrochloric acid to the sodium tungstate solution added with ethanol, adjust the pH value of the solution and monitor in real time during the reaction to ensure that the pH value of the solution is stable. Stir for 10 minutes after adding the hydrochloric acid, then turn off the heating to allow the solution to cool naturally to the aging temperature for constant temperature aging, and then filter and wash; the hydrochloric acid concentration is 12wt%; adjust the pH value of the solution to 0.4; the aging temperature is 60°C, and the aging time is 1h; S3. Tungstic acid is obtained after drying.

[0030] In this embodiment, the mass of tungstic acid before and after drying is reduced by 28.4wt%, that is, the water content of tungstic acid after filtering and washing is 28.4wt%.

[0031] Example 2 A method for reducing the water content of tungstic acid comprises the following steps: S1. Place the container containing sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol. 3 The concentration of sodium tungstate solution is 280g / L; the heating temperature is 90℃; the volume of ethanol is 5% of the volume of sodium tungstate solution; S2. Add hydrochloric acid to the sodium tungstate solution added with ethanol, adjust the pH value of the solution and monitor in real time during the reaction to ensure that the pH value of the solution is stable. Stir for 30 minutes after adding the hydrochloric acid, then turn off the heating to allow the solution to cool naturally to the aging temperature for constant temperature aging, and then filter and wash; the hydrochloric acid concentration is 14wt%; adjust the pH value of the solution to 0.6; the aging temperature is 70°C, and the aging time is 2h; S3. Tungstic acid is obtained after drying.

[0032] In this embodiment, the mass of tungstic acid before and after drying is reduced by 22.3wt%, that is, the water content of tungstic acid after filtering and washing is 22.3wt%.

[0033] Example 3 A method for reducing the water content of tungstic acid comprises the following steps: S1. Place the container containing sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol. 3 The concentration of sodium tungstate solution is 300g / L; the heating temperature is 95℃; the volume of ethanol is 6% of the volume of sodium tungstate solution; S2. Add hydrochloric acid to the sodium tungstate solution added with ethanol, adjust the pH value of the solution and monitor in real time during the reaction to ensure that the pH value of the solution is stable. Stir for 20 minutes after adding the hydrochloric acid, then turn off the heating to allow the solution to cool naturally to the aging temperature for constant temperature aging, and then filter and wash; the hydrochloric acid concentration is 16wt%; adjust the pH value of the solution to 0.8; the aging temperature is 75°C, and the aging time is 3h; S3. Tungstic acid is obtained after drying.

[0034] In this embodiment, the mass of tungstic acid before and after drying is reduced by 24.5wt%, that is, the water content of tungstic acid after filtering and washing is 24.5wt%.

[0035] Example 4 A method for reducing the water content of tungstic acid comprises the following steps: S1. Place the container containing sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol. 3 The concentration of sodium tungstate solution is 280g / L; the heating temperature is 95℃; the volume of ethanol is 6% of the volume of sodium tungstate solution; S2. Add hydrochloric acid to the sodium tungstate solution added with ethanol, adjust the pH value of the solution and monitor in real time during the reaction to ensure that the pH value of the solution is stable. Stir for 20 minutes after adding the hydrochloric acid, then turn off the heating to allow the solution to cool naturally to the aging temperature for constant temperature aging, and then filter and wash; the hydrochloric acid concentration is 14wt%; adjust the pH value of the solution to 0.6; the aging temperature is 75℃, and the aging time is 3h; S3. Tungstic acid is obtained after drying.

[0036] In this embodiment, the mass of tungstic acid is reduced by 20wt% before and after drying, that is, the water content of tungstic acid after filtering and washing is 20wt%.

[0037] Comparative Example 1 The difference from Example 4 is that in step S1, WO 3 The concentration of sodium tungstate solution is 200g / L.

[0038] In this embodiment, the mass of tungstic acid before and after drying is reduced by 34.6wt%, that is, the water content of tungstic acid after filtering and washing is 34.6wt%.

[0039] Comparative Example 2 The difference from Example 4 is that in step S1, the container containing the sodium tungstate solution is placed in a water bath, the sodium tungstate solution is stirred at room temperature and ethanol is added.

[0040] In this embodiment, the mass of tungstic acid before and after drying is reduced by 48.7wt%, that is, the water content of tungstic acid after filtering and washing is 48.7wt%.

[0041] Comparative Example 3 The difference from Example 4 is that in step S1, ethanol is not added.

[0042] In this embodiment, the mass of tungstic acid before and after drying is reduced by 40.1wt%, that is, the water content of tungstic acid after filtering and washing is 40.1wt%.

[0043] Comparative Example 4 The difference from Example 4 is that in step S2, the aging temperature is room temperature.

[0044] In this embodiment, the mass of tungstic acid before and after drying is reduced by 31.4wt%, that is, the water content of tungstic acid after filtering and washing is 31.4wt%.

[0045] Comparative Example 5 The difference from Example 4 is that in step S2, no aging is performed.

[0046] In this embodiment, the mass of tungstic acid before and after drying is reduced by 37.5wt%, that is, the water content of tungstic acid after filtering and washing is 37.5wt%.

[0047] Comparative Example 6 The difference from Example 4 is that in step S2, the pH of the solution is adjusted to 1.5.

[0048] In this embodiment, the mass of tungstic acid before and after drying is reduced by 50.4wt%, that is, the water content of tungstic acid after filtering and washing is 50.4wt%.

[0049] Comparative Example 7 The difference from Example 4 is that in step S2, the concentration of hydrochloric acid is 20wt%.

[0050] In this embodiment, the mass of tungstic acid before and after drying is reduced by 32.3wt%, that is, the water content of tungstic acid after filtering and washing is 32.3wt%.

[0051] Comparative Example 8 The difference from Example 4 is that in step S2, hydrochloric acid is measured according to the volume of hydrochloric acid required to completely generate tungstic acid, and the operation of adjusting the pH of the solution and real-time monitoring to ensure the stability of the pH of the solution is not performed.

[0052] In this embodiment, the mass of tungstic acid before and after drying is reduced by 59.5wt%, that is, the water content of tungstic acid after filtering and washing is 59.5wt%.

[0053] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for reducing the water content of tungstic acid, characterized in that: The steps include: S1. Place the container containing the sodium tungstate solution in a water bath and heat it, stir the sodium tungstate solution and add ethanol; S2. Add hydrochloric acid to the sodium tungstate solution added with ethanol, adjust the pH value of the solution and monitor in real time during the reaction to ensure that the pH value of the solution is stable. After the reaction is completed, turn off the heating to allow the solution to cool naturally to the aging temperature for constant temperature aging, and then filter and wash; S3. After drying, tungstic acid is obtained.

2. The method for reducing the water content of tungstic acid according to claim 1, characterized in that: In step S1, the concentration of the sodium tungstate solution is 250-300 g / L in terms of WO3.

3. The method for reducing the water content of tungstic acid according to claim 1, characterized in that: In the step S1, the heating temperature is 85-95°C.

4. The method for reducing the water content of tungstic acid according to claim 1, characterized in that: In step S1, the volume of ethanol is 3-6% of the volume of the sodium tungstate solution.

5. The method for reducing the water content of tungstic acid according to claim 1, characterized in that: In step S2, the concentration of hydrochloric acid is 12-16 wt %.

6. The method for reducing the water content of tungstic acid according to claim 1, characterized in that: In step S2, the pH of the solution is adjusted to 0.4-0.

8.

7. The method for reducing the water content of tungstic acid according to claim 1, characterized in that: In step S2, the pH value of the solution is adjusted and monitored in real time. When the pH value of the solution is not satisfied, hydrochloric acid is added in time to compensate for the decrease in acid concentration caused by volatilization or reaction at high temperature.

8. The method for reducing the water content of tungstic acid according to claim 1, characterized in that: In the step S2, after adding the hydrochloric acid, the reaction is completed after stirring for 10 to 30 minutes, and then the heating is turned off.

9. The method for reducing the water content of tungstic acid according to claim 1, characterized in that: In step S2, the aging temperature is 60-75° C., and the aging time is 1-3 hours.

10. The method for reducing the water content of tungstic acid according to claim 1, characterized in that: In the step S2, the water content of the tungstic acid obtained after filtering and washing is ≤30wt%.