A method for reducing the water content of tungstic acid

Abstract

The present invention belongs to the technical field of tungsten metallurgy, and specifically relates to 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, heating the sodium tungstate solution, stirring the sodium tungstate solution, and adding ethanol; S2, adding hydrochloric acid to the sodium tungstate solution with ethanol, adjusting the pH of the solution and monitoring the solution in real time during the reaction to ensure that the pH is stable; turning off the heating, allowing the solution to cool naturally to an aging temperature for constant temperature aging, followed by filtering and washing; and S3, drying to obtain tungstic acid. The tungstic acid obtained after filtration and washing in the present invention has a water content of ≤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 (H2WO4) is an important inorganic compound with high chemical stability, strong acidity, excellent photocatalytic properties, and unique semiconductor characteristics. Its high density and high-temperature resistance make it a core precursor for the preparation of materials such as metallic tungsten and tungsten carbide. It is widely used in catalysts, ceramics, and electronic materials. In catalysis, tungstic acid is used in environmental protection fields such as petroleum refining desulfurization and automobile exhaust purification. In the materials field, 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 splitting to produce hydrogen and lithium-ion battery electrode materials. Furthermore, tungstic acid-based composites have also attracted attention in cutting-edge technologies such as photochromism and gas sensing.

[0003] Tungstic acid preparation methods primarily include acid neutralization and hydrothermal synthesis. The acid neutralization method involves the reaction of a strong acid (such as hydrochloric acid) with a sodium tungstate solution to form a precipitate. While this method is simple, it can easily introduce impurities. The hydrothermal synthesis method utilizes high temperature and high pressure to manipulate crystal morphology, improving product purity and performance. During the preparation process, inadequate process control can lead to problems such as gelation and high water content in the tungstic acid. This can result in long drying times, high energy consumption, and severe material compaction. Therefore, developing a method to reduce the water content of the tungstic acid is crucial. 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 solutions:

[0006] A method for reducing the water content of tungstic acid comprises the following steps:

[0007] S1. Place the container containing the sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol.

[0008] S2. Add hydrochloric acid to the sodium tungstate solution containing ethanol, adjust the pH of the solution and monitor in real time during the reaction to ensure that the pH of the solution is stable. After the reaction is completed, turn off the heating and allow the solution to cool naturally to the aging temperature for constant temperature aging, followed by filtration and washing.

[0009] S3. Tungstic acid is obtained after drying.

[0010] As a preferred embodiment of the method for reducing the water content of tungstic acid described in the present invention, wherein: in step S1, the concentration of the sodium tungstate solution is 250-300 g / L in terms of WO3.

[0011] 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.

[0012] 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.

[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 concentration of hydrochloric acid is 12-16 wt%.

[0014] 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.

[0015] 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. When the pH 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.

[0016] 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 the addition of hydrochloric acid, and then the heating is turned off.

[0017] 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.

[0018] 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%.

[0019] The beneficial effects of the present invention are as follows:

[0020] The present invention provides 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, heating the sodium tungstate solution, stirring the sodium tungstate solution, and adding ethanol; S2. adding hydrochloric acid to the ethanol-added sodium tungstate solution, adjusting the pH of the solution and monitoring the solution in real time during the reaction to ensure that the pH is stable; after the reaction is completed, turning off the heat and allowing the solution to cool naturally to an aging temperature for constant temperature aging, followed by filtering and washing; and S3. drying to obtain tungstic acid. The tungstic acid obtained after filtration and washing in the present invention has a water content of ≤30wt%. DETAILED DESCRIPTION

[0021] The following will be a clear and complete description of the technical solutions in the embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0022] The present invention provides a method for reducing the water content of tungstic acid, which solves the problems of gelation of tungstic acid and high water content caused by inadequate process control in the current preparation process of tungstic acid, thereby reducing the energy consumption of tungstic acid drying and the degree of material compaction.

[0023] According to one aspect of the present invention, the present invention provides the following technical solutions:

[0024] A method for reducing the water content of tungstic acid comprises the following steps:

[0025] S1. Place the container containing the sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol.

[0026] S2. Add hydrochloric acid to the sodium tungstate solution containing ethanol, adjust the pH of the solution and monitor in real time during the reaction to ensure that the pH of the solution is stable. After the reaction is completed, turn off the heating and allow the solution to cool naturally to the aging temperature for constant temperature aging, followed by filtration and washing.

[0027] S3. Tungstic acid is obtained after drying.

[0028] Preferably, in step S1, the concentration of the sodium tungstate solution, calculated as WO3, is 250-300 g / L. Using this concentration of sodium tungstate as a raw material to prepare tungstic acid can promote the deposition and growth of tungstic acid particles, promote complete grain development and the formation of a denser precipitate, and reduce moisture inclusion in the intercrystalline spaces. Specifically, the concentration of the sodium tungstate solution, calculated as WO3, can be, for example, any one of 250 g / L, 260 g / L, 270 g / L, 280 g / L, 290 g / L, or 300 g / L, or a range between any two thereof.

[0029] Preferably, in step S1, the heating temperature is 85-95°C. At high temperatures, the tungstic acid grains develop more completely, which can effectively reduce the crystallization 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 grain development is incomplete and the tungstic acid water content 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, and 95°C, or a range between any two of them.

[0030] Preferably, in step S1, the volume of ethanol is 3-6% of the volume of the sodium tungstate solution. Adding the organic solvent ethanol as a dispersant can lower the dielectric constant of the solution and reduce the adsorption of water molecules on the crystal surface. Furthermore, during the subsequent drying process, the ethanol evaporates and does not contaminate the material. Specifically, the volume of ethanol can be, for example, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6% of the volume of the sodium tungstate solution, or any range between two thereof.

[0031] Preferably, in step S2, the hydrochloric acid concentration is 12-16 wt %. Using this concentration of hydrochloric acid is beneficial for reducing local over-acidity during hydrochloric acid addition, reducing the number of instantaneous nuclei, promoting the deposition and growth of tungstic acid particles, promoting complete grain development and forming a denser precipitate, and reducing moisture inclusion in crystal gaps. Specifically, the hydrochloric acid concentration can be, for example, any one of 12 wt %, 13 wt %, 14 wt %, 15 wt %, or 16 wt %, or any two thereof.

[0032] 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 produced tungstic acid is mainly monoclinic tungstic acid with a low crystalline water content. If the pH is too low, the tungstic acid easily gels and has strong water absorption; if the pH is high, highly hydrated amorphous tungstic acid is easily produced with a 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, and 0.8, or a range between any two of them.

[0033] 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 does not meet the requirements to compensate for the decrease in acid concentration caused by volatilization or reaction at high temperature.

[0034] Preferably, in step S2, according to experience, the reaction is completed after stirring for 10 to 30 minutes after the addition of 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.

[0035] 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 the range between any two, and the aging time can be, for example, 1h, 1.5h, 2h, 2.5h, 3h, any one or the range between any two.

[0036] Preferably, in step S2, the water content of the tungstic acid obtained after filtration and washing is ≤30wt%. In the present invention, the mass reduction ratio of the tungstic acid before and after drying is used as the water content ratio of the tungstic acid obtained after filtration and washing. The drying is completed when the mass of the tungstic acid does not change within a period of time.

[0037] The technical solution of the present invention is further described below with reference to specific embodiments.

[0038] Example 1

[0039] A method for reducing the water content of tungstic acid comprises the following steps:

[0040] S1. Place the container containing sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol. The concentration of sodium tungstate solution is 250g / L based on WO3. The heating temperature is 85℃. The volume of ethanol is 3% of the volume of sodium tungstate solution.

[0041] S2. Add hydrochloric acid to the sodium tungstate solution to which ethanol has been added, adjust the pH of the solution and monitor in real time during the reaction to ensure that the pH of the solution is stable. Stir for 10 minutes after adding the hydrochloric acid, then turn off the heating and allow the solution to cool naturally to the aging temperature for constant temperature aging, followed by filtration and washing. The hydrochloric acid concentration is 12wt%; the pH of the solution is adjusted to 0.4; the aging temperature is 60°C, and the aging time is 1 hour.

[0042] S3. Tungstic acid is obtained after drying.

[0043] In this embodiment, the mass of tungstic acid before and after drying is reduced by 28.4 wt %, that is, the water content of tungstic acid after filtration and washing is 28.4 wt %.

[0044] Example 2

[0045] A method for reducing the water content of tungstic acid comprises the following steps:

[0046] S1. Place the container containing sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol. The concentration of sodium tungstate solution is 280g / L based on WO3. The heating temperature is 90℃. The volume of ethanol is 5% of the volume of sodium tungstate solution.

[0047] S2. Add hydrochloric acid to the sodium tungstate solution to which ethanol has been added, adjust the pH of the solution and monitor in real time during the reaction to ensure that the pH of the solution is stable. Stir for 30 minutes after adding the hydrochloric acid, then turn off the heating and allow the solution to cool naturally to the aging temperature for constant temperature aging, followed by filtration and washing. The hydrochloric acid concentration is 14wt%; the pH of the solution is adjusted to 0.6; the aging temperature is 70°C, and the aging time is 2 hours.

[0048] S3. Tungstic acid is obtained after drying.

[0049] In this embodiment, the mass of tungstic acid before and after drying is reduced by 22.3 wt %, that is, the water content of tungstic acid after filtration and washing is 22.3 wt %.

[0050] Example 3

[0051] A method for reducing the water content of tungstic acid comprises the following steps:

[0052] S1. Place the container containing sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol. The concentration of sodium tungstate solution is 300g / L in terms of WO3. The heating temperature is 95℃. The volume of ethanol is 6% of the volume of the sodium tungstate solution.

[0053] S2. Add hydrochloric acid to the sodium tungstate solution to which ethanol has been added, adjust the pH of the solution and monitor in real time during the reaction to ensure that the pH of the solution is stable. Stir for 20 minutes after adding the hydrochloric acid, then turn off the heating and allow the solution to cool naturally to the aging temperature for constant temperature aging, followed by filtration and washing. The hydrochloric acid concentration is 16wt%; the pH of the solution is adjusted to 0.8; the aging temperature is 75°C, and the aging time is 3 hours.

[0054] S3. Tungstic acid is obtained after drying.

[0055] In this embodiment, the mass of tungstic acid before and after drying is reduced by 24.5 wt %, that is, the water content of tungstic acid after filtration and washing is 24.5 wt %.

[0056] Example 4

[0057] A method for reducing the water content of tungstic acid comprises the following steps:

[0058] S1. Place the container containing sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol. The concentration of sodium tungstate solution is 280g / L based on WO3. The heating temperature is 95℃. The volume of ethanol is 6% of the volume of sodium tungstate solution.

[0059] S2. Add hydrochloric acid to the sodium tungstate solution to which ethanol has been added, adjust the pH of the solution and monitor in real time during the reaction to ensure that the pH of the solution is stable. Stir for 20 minutes after adding the hydrochloric acid, then turn off the heating and allow the solution to cool naturally to the aging temperature for constant temperature aging, followed by filtration and washing. The hydrochloric acid concentration is 14wt%; the pH of the solution is adjusted to 0.6; the aging temperature is 75°C, and the aging time is 3 hours.

[0060] S3. Tungstic acid is obtained after drying.

[0061] In this embodiment, the mass of tungstic acid is reduced by 20 wt % before and after drying, that is, the water content of tungstic acid after filtration and washing is 20 wt %.

[0062] Comparative Example 1

[0063] The difference from Example 4 is that in step S1, the concentration of the sodium tungstate solution is 200 g / L in terms of WO3.

[0064] In this embodiment, the mass of tungstic acid before and after drying is reduced by 34.6 wt %, that is, the water content of tungstic acid after filtration and washing is 34.6 wt %.

[0065] Comparative Example 2

[0066] 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.

[0067] In this embodiment, the mass of tungstic acid before and after drying is reduced by 48.7 wt %, that is, the water content of tungstic acid after filtration and washing is 48.7 wt %.

[0068] Comparative Example 3

[0069] The difference from Example 4 is that in step S1, ethanol is not added.

[0070] In this embodiment, the mass of tungstic acid before and after drying is reduced by 40.1 wt %, that is, the water content of tungstic acid after filtration and washing is 40.1 wt %.

[0071] Comparative Example 4

[0072] The difference from Example 4 is that in step S2, the aging temperature is room temperature.

[0073] In this embodiment, the mass of tungstic acid before and after drying is reduced by 31.4 wt %, that is, the water content of tungstic acid after filtration and washing is 31.4 wt %.

[0074] Comparative Example 5

[0075] The difference from Example 4 is that in step S2, no aging is performed.

[0076] In this embodiment, the mass of tungstic acid before and after drying is reduced by 37.5 wt %, that is, the water content of tungstic acid after filtration and washing is 37.5 wt %.

[0077] Comparative Example 6

[0078] The difference from Example 4 is that in step S2, the pH of the solution is adjusted to 1.5.

[0079] In this embodiment, the mass of tungstic acid before and after drying is reduced by 50.4 wt %, that is, the water content of tungstic acid after filtration and washing is 50.4 wt %.

[0080] Comparative Example 7

[0081] The difference from Example 4 is that in step S2, the concentration of hydrochloric acid is 20 wt %.

[0082] In this embodiment, the mass of tungstic acid before and after drying is reduced by 32.3 wt %, that is, the water content of tungstic acid after filtration and washing is 32.3 wt %.

[0083] Comparative Example 8

[0084] 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.

[0085] In this embodiment, the mass of tungstic acid before and after drying is reduced by 59.5 wt %, that is, the water content of tungstic acid after filtration and washing is 59.5 wt %.

[0086] 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 transformations made by using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect application 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 sodium tungstate solution in a water bath and heat it. Stir the sodium tungstate solution and add ethanol. The concentration of sodium tungstate solution is 250-300 g / L based on WO3. The heating temperature is 85-95℃. S2. Add hydrochloric acid to the sodium tungstate solution to which ethanol has been added, and adjust the pH value of the solution to 0.4-0.

8. During the reaction, monitor the pH value of the solution in real time to ensure that the pH value is stable. If the pH value of the solution is not satisfied, add hydrochloric acid in time. After the reaction, turn off the heating and allow the solution to cool naturally to the aging temperature for constant temperature aging. The aging temperature is 60-75°C and the aging time is 1-3 hours. Then filter and wash. The water content of the tungstic acid obtained after filtration and washing is ≤30wt%; S3. Tungstic acid is obtained after drying.

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

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

4. The method for reducing the water content of tungstic acid according to claim 1, wherein: In step S2, after adding hydrochloric acid, the mixture is stirred for 10 to 30 minutes and the reaction is completed, and then the heating is turned off.