High-purity sodium sulfide preparation method based on homogeneous reaction

Abstract

The invention provides a high-purity sodium sulfide preparation method based on homogeneous reaction, and belongs to the technical field of new energy battery materials, the preparation method comprises the following steps: S1, under the protection of inert atmosphere, dissolving thiourea and sodium alkoxide in an anhydrous alcohol organic solvent, and heating to a solvent reflux temperature for reaction; s2, after the reaction is finished, carrying out solid-liquid separation on a reaction solution under the protection of an inert atmosphere to obtain a sodium sulfide solid and a mother solution; and S3, washing the sodium sulfide solid with preheated absolute ethyl alcohol, and performing vacuum drying to obtain the high-purity sodium sulfide. By constructing a homogeneous reaction system, the reaction is more thorough, the product is precipitated in a single solid phase and is easy to separate, the purity of the prepared sodium sulfide product is more than or equal to 99%, the reaction condition is mild, the solvent can be recycled and reused, the green chemistry principle is met, and industrial production is easy.

Description

Technical Field

[0001] This invention relates to the field of new energy battery materials technology, specifically to a method for preparing high-purity sodium sulfide based on homogeneous reaction. Background Technology

[0002] Sodium sulfide is an important basic inorganic chemical raw material, widely used in industries such as dyes, papermaking, pharmaceuticals, leather, rubber, and electroplating. It is also an emerging precursor for battery materials. Traditional industrial production mainly uses the coal powder reduction method for sodium sulfide, which has inherent drawbacks such as high energy consumption, heavy pollution, and low product purity. With the rapid development of the new energy industry, the market demand for high-purity, low-carbon sodium sulfide is increasingly urgent. Traditional industrial preparation technologies are insufficient to meet the upgrading requirements of high-end manufacturing and new energy materials for green and high-purity raw materials.

[0003] Currently, the industry has proposed several improved routes, such as the sodium hydroxide absorption of hydrogen sulfide method, which utilizes the by-product H2S gas from petrochemical and coal chemical tail gases to react with NaOH solution: H2S + 2NaOH → Na2S + 2H2O. Although this method can avoid high-temperature calcination and reduce energy consumption, the transportation and storage of high-purity H2S pose significant safety risks. H2S is a highly toxic and flammable gas; H2S leakage can lead to acute poisoning or even death. The equipment requires high-level explosion-proof and corrosion-resistant designs, resulting in high investment and maintenance costs. Another improved route is the solid-phase reaction method of thiourea and alkali metal hydroxide, with the reaction formula: (NH2)2CS + 2NaOH → Na2S + Na2CO3 + 2NH3↑. Although the raw materials for this route are readily available, the reactants thiourea and sodium hydroxide are both solid powders, leading to problems such as uneven solid-solid mixing and low reaction efficiency.

[0004] Therefore, it is of great significance to develop a new method that is mild, green, and can efficiently and stably obtain high-purity sodium sulfide. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a method for preparing high-purity sodium sulfide based on homogeneous reaction, which aims to solve the technical problems of high energy consumption, high safety risks, insufficient product purity and poor reaction efficiency in the existing sodium sulfide preparation process.

[0006] In a first aspect, the present invention provides a method for preparing high-purity sodium sulfide based on homogeneous reaction, comprising the following steps: S1. Under an inert atmosphere, thiourea and sodium alkoxide are dissolved in anhydrous alcoholic organic solvent and heated to the solvent reflux temperature to carry out the reaction. S2. After the reaction is completed, under the protection of an inert atmosphere, the reaction solution is separated into solid sodium sulfide and mother liquor. S3. High-purity sodium sulfide is obtained by washing with preheated anhydrous ethanol and vacuum drying of sodium sulfide solid.

[0007] Preferably, in step S1, the molar ratio of thiourea to sodium alkoxide is 1:(2.0~2.5).

[0008] Preferably, in step S1, the anhydrous alcoholic organic solvent includes at least one of anhydrous ethanol, anhydrous methanol, and anhydrous isopropanol.

[0009] Preferably, in step S1, the sodium alkoxide includes at least one of sodium ethoxide and sodium methoxide.

[0010] Preferably, in step S1, the solvent reflux temperature is 60℃~85℃, and the reaction time is 4~12 hours.

[0011] Preferably, in step S2, the solid-liquid separation method is thermal filtration, and the temperature of thermal filtration is 50~70℃.

[0012] Preferably, in step S2, the mother liquor is distilled to recover anhydrous alcohol solvent, and the recovered anhydrous alcohol solvent is used in step S1.

[0013] Preferably, in step S3, the temperature of the preheated anhydrous ethanol is 50~70℃.

[0014] Preferably, in step S3, the vacuum drying conditions are: temperature 60~100℃, vacuum degree ≤-0.09MPa.

[0015] Secondly, the present invention provides a high-purity sodium sulfide, which is prepared by the preparation method described in the first aspect.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing high-purity sodium sulfide based on homogeneous reaction. By constructing a homogeneous reaction system of "thiourea-sodium alkoxide-alcohol solvent," under heating conditions, thiourea decomposes and provides a sulfur source, which reacts with sodium ions provided by sodium alkoxide to generate the target product, sodium sulfide. In this system, all reactants are soluble, the homogeneous reaction is thorough, and the product precipitates as a single solid phase, which is easily separated, yielding white powdered sodium sulfide with a purity ≥99%. The preparation method provided by this invention features mild reaction conditions, recyclable solvents, conforms to green chemistry principles, and avoids high temperature, high pressure, and highly toxic raw materials. The process is simple, the equipment is conventional, and it is easily industrialized. The high-purity sodium sulfide obtained by this invention has high purity and high application value, and is particularly suitable for high-end fields sensitive to impurities, such as the synthesis of sulfide solid electrolytes. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of the method for preparing high-purity sodium sulfide based on homogeneous reaction according to the present invention. Figure 2 The image shows the XRD pattern of the sodium sulfide product obtained in Example 1 of this invention. Figure 3 The image shows the XRD pattern of the sodium sulfide product prepared in Comparative Example 1 of this invention. Detailed Implementation

[0018] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0019] To address the technical problems of high energy consumption, significant safety risks, insufficient product purity, and poor reaction efficiency in existing sodium sulfide preparation processes, this invention provides a method for preparing high-purity sodium sulfide based on homogeneous reaction. This method involves constructing a homogeneous reaction system of "thiourea-sodium alkoxide-alcohol solvent." Under heating conditions, thiourea decomposes and provides a sulfur source, which reacts with sodium ions provided by sodium alkoxide to generate the target product, sodium sulfide. In this system, all reactants are soluble, achieving molecular-level contact, resulting in high reaction efficiency, mild conditions, and high product purity.

[0020] Please refer to the appendix. Figure 1 In a first aspect, embodiments of the present invention provide a method for preparing high-purity sodium sulfide based on homogeneous reaction, comprising the following steps: S1. Under an inert atmosphere, thiourea and sodium alkoxide are dissolved in anhydrous alcoholic organic solvent and heated to the solvent reflux temperature to carry out the reaction. S2. After the reaction is completed, under the protection of an inert atmosphere, the reaction solution is separated into solid sodium sulfide and mother liquor. S3. High-purity sodium sulfide is obtained by washing with preheated anhydrous ethanol and vacuum drying of sodium sulfide solid.

[0021] In the technical solution of this invention embodiment, the main chemical reaction principle can be represented by the following formula: (NH2)2CS + 2RONa (R is an alkyl group) → Na2S↓ + 2ROH + organic byproducts. Thiourea, in a strongly alkaline alcoholic solution provided by sodium alkoxide, first undergoes alcoholysis or decomposition, generating in situ active sulfur species (such as S...). 2- The active sulfur species then reacts with sodium alkoxide to generate the target product, sodium sulfide, which precipitates out. This process may be accompanied by the generation of nitrogen-containing organic byproducts such as cyanamide, guanidine, and ethyl carbamate. These byproducts are soluble in alcohol solvents and can be separated from the product.

[0022] Furthermore, in some embodiments, in step S1, the molar ratio of thiourea to sodium alkoxide is 1:(2.0~2.5).

[0023] Furthermore, in some embodiments, in step S1, the anhydrous alcoholic organic solvent includes at least one of anhydrous ethanol, anhydrous methanol, and anhydrous isopropanol.

[0024] Furthermore, in some embodiments, in step S1, the sodium ethoxide includes at least one of sodium ethoxide and sodium methoxide.

[0025] Furthermore, in some embodiments, in step S1, the solvent reflux temperature is 60°C to 85°C, and the reaction time is 4 to 12 hours.

[0026] Furthermore, in some embodiments, in step S2, the solid-liquid separation method is thermal filtration, and the temperature of thermal filtration is 50~70°C.

[0027] In the technical solution of this invention embodiment, the solid-liquid separation method using hot filtration can effectively prevent impurities from crystallizing and precipitating out due to temperature reduction during the filtration process, thus ensuring the purity of sodium sulfide solid.

[0028] Furthermore, in some embodiments, in step S2, the mother liquor is distilled to recover anhydrous alcohol solvent, and the recovered anhydrous alcohol solvent is used in step S1.

[0029] In the technical solution of this invention embodiment, the mother liquor can be distilled to recover anhydrous alcohol solvents and reused in the reaction system in step S1, realizing the recycling of solvents, reducing production costs, reducing the emission of organic solvents, and conforming to the development concept of green chemical industry.

[0030] Furthermore, in some embodiments, in step S3, the temperature of the preheated anhydrous ethanol is 50~70°C.

[0031] In the technical solution of this invention embodiment, washing with preheated anhydrous ethanol helps the soluble organic byproducts remaining on the surface of sodium sulfide solid to dissolve rapidly in ethanol, effectively removing the mother liquor and soluble organic byproducts remaining on the surface of sodium sulfide solid.

[0032] Furthermore, in some embodiments, in step S3, the vacuum drying conditions are: temperature of 60~100℃ and vacuum degree ≤-0.09MPa.

[0033] Secondly, embodiments of the present invention provide a high-purity sodium sulfide, which is prepared by the preparation method described in the first aspect.

[0034] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0035] Example 1 A method for preparing high-purity sodium sulfide based on homogeneous reaction, the specific steps of which are as follows: In an argon-protected glove box, 300 mL of anhydrous ethanol was added to a dry 500 mL three-necked flask. Then, 19.0 g (0.25 mol) of thiourea and 166.7 g of a 21% sodium ethoxide ethanol solution (containing approximately 35.0 g of sodium ethoxide, 0.512 mol, with a molar ratio of sodium ethoxide to thiourea of ​​2.05:1) were added sequentially. A reflux condenser was installed, and the argon pressure was maintained. The mixture was heated to 78-80 °C and refluxed for 6 hours. The reaction solution was kept at 65 °C and hot-filtered under argon protection. The precipitate was washed three times with anhydrous ethanol preheated at 65 °C. The resulting solid was vacuum dried at 80 °C and -0.095 MPa for 6 hours to obtain 18.5 g of white sodium sulfide.

[0036] Figure 2 The XRD pattern of the sodium sulfide product in this embodiment shows that it is pure phase Na2S. The purity of sodium sulfide was determined to be 99.2% by chemical titration.

[0037] Example 2 The difference between this embodiment and Example 1 is that the amount of feed is changed, the molar ratio of sodium ethoxide to thiourea is 2.35:1, and the reaction is refluxed for 8 hours; the other conditions and parameters are the same as in Example 1.

[0038] Finally, 19.1g of white sodium sulfide was obtained, and the purity of sodium sulfide was determined to be 99.5% by chemical titration.

[0039] Example 3 The mother liquor collected by hot filtration in Example 1 was distilled at atmospheric pressure to recover the 77-79℃ fraction (about 280 mL of ethanol), which had a water content of less than 50 ppm. This fraction was then used directly in the next batch of reaction, and the process was repeated 5 times.

[0040] Testing revealed that after one application, 18.4g of white sodium sulfide was obtained, with a purity of 99.2% as determined by chemical titration; after three applications, 18.3g of white sodium sulfide was obtained with a purity of 99.11%; and after five applications, 18.2g of white sodium sulfide was obtained with a purity of 99.06%.

[0041] Data shows that after five consecutive applications, the purity of sodium sulfide obtained each time was higher than 99.0%, and compared with the sodium sulfide with a purity of 99.2% obtained in Example 1, the purity of sodium sulfide did not decrease significantly. This indicates that anhydrous ethanol can be recycled and reused without having a significant negative impact on product purity.

[0042] Example 4 The difference between this embodiment and Embodiment 1 is that sodium ethoxide is replaced with an equimolar amount of sodium methoxide, while the other conditions and parameters are the same as in Embodiment 1.

[0043] The purity of sodium sulfide was determined to be 99.1% by chemical titration.

[0044] Comparative Example 1 This comparative example uses a solid-state method to prepare sodium sulfide, and the specific steps are as follows: 19.0 g (0.25 mol) of thiourea and 20.0 g (0.5 mol) of sodium hydroxide solid were ground and mixed, and heated at 400 °C for 4 hours under argon atmosphere. The resulting product was a grayish-yellow powder.

[0045] Figure 3 The XRD pattern of the sodium sulfide product prepared in this comparative example shows the presence of impurity peaks such as Na2CO3. The purity of sodium sulfide was determined to be 85% by chemical titration.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 is that the ethanol was not preheated during washing, and the precipitate was washed three times with room temperature ethanol.

[0047] The purity of sodium sulfide was determined to be 98.8% by chemical titration, which was lower than 99.2% in Example 1. This was because the unheated ethanol had a weaker dissolving effect on impurities, thus affecting the purity of the sodium sulfide product.

[0048] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method for preparing high-purity sodium sulfide based on homogeneous reaction, characterized in that, Includes the following steps: S1. Under an inert atmosphere, thiourea and sodium alkoxide are dissolved in anhydrous alcoholic organic solvent and heated to the solvent reflux temperature to carry out the reaction. S2. After the reaction is completed, under the protection of an inert atmosphere, the reaction solution is separated into solid sodium sulfide and mother liquor. S3. The sodium sulfide solid is washed with preheated anhydrous ethanol and then vacuum dried to obtain high-purity sodium sulfide.

2. The method for preparing high-purity sodium sulfide based on homogeneous reaction according to claim 1, characterized in that, In step S1, the molar ratio of thiourea to sodium alkoxide is 1:(2.0~2.5).

3. The method for preparing high-purity sodium sulfide based on homogeneous reaction according to claim 1, characterized in that, In step S1, the anhydrous alcoholic organic solvent includes at least one of anhydrous ethanol, anhydrous methanol, and anhydrous isopropanol.

4. The method for preparing high-purity sodium sulfide based on homogeneous reaction according to claim 1, characterized in that, In step S1, the sodium alkoxide includes at least one of sodium ethoxide and sodium methoxide.

5. The method for preparing high-purity sodium sulfide based on homogeneous reaction according to claim 1, characterized in that, In step S1, the solvent reflux temperature is 60℃~85℃, and the reaction time is 4~12 hours.

6. The method for preparing high-purity sodium sulfide based on homogeneous reaction according to claim 1, characterized in that, In step S2, the solid-liquid separation method is thermal filtration, and the temperature of the thermal filtration is 50~70℃.

7. The method for preparing high-purity sodium sulfide based on homogeneous reaction according to claim 1, characterized in that, In step S2, the mother liquor is distilled to recover anhydrous alcohol solvent, and the recovered anhydrous alcohol solvent is used in step S1.

8. The method for preparing high-purity sodium sulfide based on homogeneous reaction according to claim 1, characterized in that, In step S3, the temperature of the preheated anhydrous ethanol is 50~70℃.

9. The method for preparing high-purity sodium sulfide based on homogeneous reaction according to claim 1, characterized in that, In step S3, the conditions for vacuum drying are: temperature 60~100℃, vacuum degree ≤-0.09MPa.

10. A high-purity sodium sulfide, characterized in that, It is prepared by the method for preparing high-purity sodium sulfide based on homogeneous reaction as described in any one of claims 1 to 9.

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