A purification method for circulating extraction of high-purity dimethyl sulfide and dimethyl sulfide
Through the steps of circulating extraction, distillation and liquid alkali treatment, the problems of low purity, low yield, high energy consumption and serious pollution in the prior art are solved, and the effects of high purity (greater than 99.9%) and continuous production are achieved.
Patent Information
- Application Number
- CN202411992181.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-04-08
AI Technical Summary
In the production of high-purity dimethyl sulfide, the prior art has problems such as low product purity, low yield, high energy consumption, serious pollution and inability to continuously produce.
The purification method of circulating extraction of high-purity dimethyl sulfide is adopted, including extracting and removing unreacted methanol impurities from methanol and hydrogen sulfide, distillation removes high boiling point substances, liquid alkali treatment removes acidic impurities, and finally distillation again to remove excess water.
High purity (greater than 99.9%) production of dimethyl sulfide is achieved, which improves product purity and yield, reduces energy consumption and pollution, and supports the continuous production of dimethyl sulfide.
Smart Images
Figure CN119775177A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of purification, and in particular to a purification method for cyclically extracting high-purity dimethyl sulfide and dimethyl sulfide. Background Art
[0002] Dimethyl sulfide, also known as methyl sulfide, is toxic. Low concentrations of dimethyl sulfide vapor generally cause nausea and loss of appetite, while high concentrations of vapor have a paralyzing effect on the central nervous system and have a unique fishy marine flavor. Dimethyl sulfide is an important intermediate in the production of dimethyl sulfoxide, methionine and pesticides. In the production of dimethyl sulfoxide, high-purity dimethyl sulfide is one of the key raw materials, which can be converted into dimethyl sulfoxide through oxidation and other reaction steps. In the pharmaceutical industry, high-purity dimethyl sulfide can be used for the synthesis and preparation of drugs. High-purity dimethyl sulfide is a solvent with excellent performance and can be used for organic compounds, resins, inorganic compounds, polymerization reactions and cyanidation reactions. Adding an appropriate amount of dimethyl sulfide to city gas can help people detect gas leaks in time. Therefore, the development of safe, efficient, high-purity, non-toxic and waste-free sulfides is of great significance in terms of both economic benefits and environmental impact. The synthesis methods of dimethyl sulfide are: reaction of dimethyl sulfate and sodium sulfide: This is a relatively classic synthesis method. The process of this method is relatively mature, but dimethyl sulfate has certain toxicity and danger, and has high requirements for production operation and environmental protection. Biosynthesis method: Using specific microorganisms or enzymes to catalyze the synthesis of dimethyl sulfide, it has the advantages of green environmental protection and mild reaction conditions. Electrochemical synthesis method: The relevant raw materials are converted into dimethyl sulfide by electrochemical methods. This method has the advantages of high reaction selectivity and easy control, but it is still in the laboratory research stage and needs to further optimize the reaction conditions and improve the yield. Reaction of methanol and hydrogen sulfide: Methanol and hydrogen sulfide can also react at high temperature to obtain dimethyl sulfide. This method requires higher temperature and specific catalyst conditions, and has certain challenges to reaction equipment and process control, but the raw materials are relatively easy to obtain. In the production process, the product purity is low, the yield is low, the energy consumption is high, the pollution is serious, and it cannot be produced continuously. Summary of the invention
[0003] The present invention provides a purification method for high-purity dimethyl sulfide by cyclic extraction, wherein unreacted methanol and other impurities are removed by extraction process, trace high-boiling-point substances in dimethyl sulfide are removed by rectification process, and then by-product methyl mercaptan is converted into sodium methyl mercaptan by liquid alkali process, thereby eliminating the dimethyl sulfide system, and finally, excess water is removed by rectification again. Dimethyl sulfide with a content greater than 99.9% can be obtained.
[0004] The present invention provides a purification method for cyclic extraction of high-purity dimethyl sulfide, comprising:
[0005] The crude dimethyl sulfide synthesized from methanol and hydrogen sulfide is extracted to remove unreacted methanol impurities;
[0006] The extracted dimethyl sulfide is distilled to remove alkane impurities;
[0007] The dimethyl sulfide after distillation is treated with liquid alkali to remove acidic impurities;
[0008] The dimethyl sulfide after alkali washing is distilled again to remove excess water to obtain high-purity dimethyl sulfide.
[0009] In some embodiments, the method comprises:
[0010] The crude dimethyl sulfide synthesized from methanol and hydrogen sulfide is extracted to remove unreacted methanol impurities;
[0011] The extracted dimethyl sulfide is distilled to remove alkane impurities therein;
[0012] The dimethyl sulfide after distillation is treated with liquid alkali to remove acidic impurities;
[0013] The dimethyl sulfide after alkali washing is distilled again to remove excess water to obtain high-purity dimethyl sulfide.
[0014] In some specific embodiments, the extracting of crude dimethyl sulfide synthesized from methanol and hydrogen sulfide to remove unreacted methanol impurities comprises:
[0015] The extraction process uses water as an extractant, the mass ratio of water to crude dimethyl sulfide is 1:1-1.5:1, the extraction temperature is not higher than 30°C, and the methanol impurity content is controlled to be lower than 0.1% through cyclic extraction.
[0016] In some specific embodiments, the mass ratio of water to crude dimethyl sulfide is 1:1.
[0017] In some specific embodiments, the mass ratio of water to crude dimethyl sulfide is 1.5:1.
[0018] In some specific embodiments, the extraction process uses water as an extractant, the mass ratio of water to crude dimethyl sulfide is 1:1 to 1.5:1, the extraction temperature is not higher than 30°C, and the methanol impurity content is controlled to be less than 0.1% by cyclic extraction, including
[0019] According to the stoichiometric ratio of methanol and hydrogen sulfide, they are mixed and heated to a certain temperature in a chemical reactor to obtain a crude dimethyl sulfide solution;
[0020] The crude dimethyl sulfide solution and the extractant were mixed in a mass ratio of 1:1, then heated in a water bath and stirred evenly, and when the temperature was raised to 30°C, the gas was passed into a condenser for condensation and collection;
[0021] The extraction step is cyclic, wherein the mass ratio of water to crude dimethyl sulfide is 1:1 for the first extraction, and the mass ratio of the water phase after the first extraction to crude dimethyl sulfide is 1:1 for the second extraction, and the cycle is repeated until the methanol impurity is below 0.1%.
[0022] In some specific embodiments, the distillation of the extracted dimethyl sulfide to remove alkane impurities therein comprises:
[0023] The temperature range of the distillation operation is that the bottom temperature is not higher than 50°C, and the outlet gas temperature is between 37 and 39°C. The extracted dimethyl sulfide liquid is sent to the distillation tower, the bottom temperature is controlled not to exceed 50°C, and the outlet gas temperature is maintained at 37 to 39°C.
[0024] In some specific embodiments, the dimethyl sulfide after distillation is treated with liquid alkali to remove acidic impurities, comprising:
[0025] According to the composition and properties of dimethyl sulfide after distillation, the optimal concentration range of alkali solution for liquid alkali treatment is determined to be 10-20% sodium hydroxide solution;
[0026] The dimethyl sulfide after distillation and the alkali solution are fully mixed in a volume ratio of 1:1 to form a uniform liquid phase;
[0027] The pH value of the mixed solution is monitored in real time by an online pH detector. When the pH value is lower than 10, additional alkali solution is automatically added until the pH value reaches and stabilizes at 10;
[0028] If the pH value exceeds 10, reduce the amount of alkali solution added to maintain the pH value at 10.
[0029] The present invention further provides dimethyl sulfide prepared by the above-mentioned purification method of cyclic extraction of high-purity dimethyl sulfide.
[0030] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:
[0031] The present invention relates to a method for purifying dimethyl disulfide. The crude dimethyl sulfide synthesized from methanol and hydrogen sulfide is subjected to an extraction process to remove unreacted methanol and other impurities, and then subjected to a distillation process to remove trace amounts of high-boiling substances in the dimethyl sulfide, and then subjected to a liquid alkali process to convert the generated byproduct methyl mercaptan into sodium methyl mercaptan, thereby eliminating the dimethyl sulfide system, and finally subjected to distillation again to remove excess water. Dimethyl sulfide with a content greater than 99.9% can be obtained. High-purity dimethyl sulfide is essential for synthesizing high-quality dimethyl sulfoxide. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1The present invention is a flow chart of a purification method for cyclic extraction of high-purity dimethyl sulfide. DETAILED DESCRIPTION
[0033] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.
[0034] Methanol and hydrogen sulfide react at high temperature to obtain crude dimethyl sulfide. Crude dimethyl sulfide components and content: The organic phase contains 40% dimethyl sulfide, 40% methanol, 15% water, 2% methyl mercaptan, 3% high boiling point, etc.
[0035] The present invention provides a purification method for high-purity dimethyl sulfide by cyclic extraction, wherein crude dimethyl sulfide synthesized from methanol and hydrogen sulfide is subjected to an extraction process to remove unreacted methanol and other impurities, and then subjected to a rectification process to remove trace amounts of high-boiling substances in dimethyl sulfide, and then subjected to a liquid alkali process to convert the generated byproduct methyl mercaptan into sodium methyl mercaptan, thereby eliminating the dimethyl sulfide system, and finally subjected to another rectification to remove excess water. Thus, dimethyl sulfide with a content greater than 99.9% can be obtained. High-purity dimethyl sulfide is essential for synthesizing high-quality dimethyl sulfoxide.
[0036] like Figure 1 In this embodiment, a purification method for cyclic extraction of high-purity dimethyl sulfide may specifically include:
[0037] Step S101, extracting crude dimethyl sulfide synthesized from methanol and hydrogen sulfide to remove unreacted methanol impurities.
[0038] According to the stoichiometric ratio of methanol and hydrogen sulfide, a chemical reactor is used to mix and heat them to a certain temperature to obtain a crude dimethyl sulfide solution. The content of impurities such as methanol in the crude dimethyl sulfide solution is determined by analyzing the component content of the crude dimethyl sulfide solution, and a suitable extractant is selected according to the concentration. The crude dimethyl sulfide solution and the extractant are mixed in a certain proportion and fully mixed by a stirrer.
[0039] Here, the extraction process uses water as an extractant, the mass ratio of water to crude dimethyl sulfide is 1:1 to 1.5:1, the extraction temperature is not higher than 30° C., and the methanol impurity content is controlled to be lower than 0.1% through cyclic extraction.
[0040] Specifically, the extractant is water, the water-ether ratio is about 1:1 to 1.5:1, the temperature is ≤30°C, and methanol is removed; water is added to the extracted organic phase, the water-ether ratio is about 1:1 to 1.5:1, the temperature is ≤30°C, and the second extractant is used as the first extractant in the next batch, that is, cyclic extraction. The cyclic extraction can control the methanol impurity to 1-2% for one time, and the methanol impurity can be controlled to less than 0.1% for the second time. The methanol content can be undetectable in gas phase detection. The methyl sulfide content of the experimental stock solution is only 35%. The yield is also 35%, with basically no loss.
[0041] Step S102, distilling the extracted dimethyl sulfide to remove alkane impurities therein.
[0042] By adopting the distillation method, the temperature of the tower bottom is controlled not higher than 50°C, the temperature of the tower top is between 37 and 39°C, and the distillate is collected by condensation. The extraction rate of methyl mercaptan is about 80%, and the remaining 20% is alkane impurities.
[0043] When the water bath temperature reaches 50℃, the heating stops automatically, the distillation process ends, and the fraction is sampled. Take the above fraction and water in a mass ratio of 1:1, mix them thoroughly, place them in a water bath, stir and heat them, and when the temperature rises to 30℃, bubbles begin to appear, and the gas is passed into the condenser for condensation and collection; when the temperature rises to 50℃, the distillation ends, and the fraction is sampled.
[0044] Here, the extracted dimethyl sulfide liquid is sent to the distillation tower for distillation. The temperature range of the distillation operation is very critical. The temperature of the tower bottom needs to be strictly controlled not to exceed 50°C, while the outlet gas temperature is kept in the range of 37-39°C. The purpose of controlling the temperature is to remove the alkane impurities in dimethyl sulfide to the greatest extent, while avoiding the decomposition or deterioration of dimethyl sulfide due to excessive temperature. Specifically, a temperature sensor can be installed in the tower bottom of the distillation tower to monitor the tower bottom temperature in real time. When the temperature is close to 50°C, the heating power is adjusted in time to maintain the temperature below 50°C. At the same time, a temperature sensor is installed on the top of the tower to monitor the outlet gas temperature. By adjusting the cooling water flow and temperature of the condenser, the outlet gas temperature is stabilized at 37-39°C. During the distillation process, alkane impurities will evaporate preferentially and be taken out of the top of the tower due to their low boiling point, while dimethyl sulfide with a higher boiling point will mainly remain in the tower bottom. By controlling the distillation temperature, most of the alkane impurities can be evaporated from the top of the tower and condensed and collected, while dimethyl sulfide with higher purity can be obtained from the bottom of the tower. In order to further improve the purity of dimethyl sulfide, alkane impurities can be separated more effectively. At the same time, the full reflux operation of the distillation tower can also be adopted, that is, all the condensate at the top of the tower is refluxed to the tower kettle for re-evaporation, which can significantly improve the liquid-gas contact efficiency in the tower and enhance the distillation separation effect. After the distillation is completed, the high-purity dimethyl sulfide obtained from the bottom of the tower can enter the next alkali washing process to further remove the acidic impurities that may remain therein, and finally obtain a high-purity product that meets the requirements. By strictly controlling the distillation operation parameters and effectively removing alkane impurities, the quality of dimethyl sulfide products can be significantly improved, providing high-quality raw materials for downstream deep processing applications.
[0045] Step S103, treating the dimethyl sulfide after distillation with liquid alkali to remove acidic impurities.
[0046] Here, after dimethyl sulfide is distilled, liquid alkali treatment is required to remove the acidic impurities therein. First, the optimal alkali concentration range should be determined according to the composition and properties of dimethyl sulfide after distillation. By analyzing the types and contents of acidic impurities in dimethyl sulfide, the required amount of alkali can be estimated. At the same time, the tolerance of dimethyl sulfide to alkali itself should also be considered. Too high alkali concentration may cause side reactions such as hydrolysis of dimethyl sulfide. Taking the above factors into consideration, the optimal alkali concentration range for liquid alkali treatment is determined to be 10% to 20% sodium hydroxide solution. In actual operation, the dimethyl sulfide after distillation and the alkali are fully mixed in a volume ratio of 1:1 to form a uniform liquid phase. This ratio can ensure that there is enough alkali to neutralize the acidic impurities, while also avoiding the negative effects that may be caused by excessive alkali. The mixing process can be carried out in a stirred tank, and the contact and mass transfer between the two phases can be enhanced by mechanical stirring or gas bubbling.
[0047] In order to control the alkalinity of the mixed solution in real time, a pH detector needs to be installed online. When the pH value is detected to be lower than 10, it means that the alkali solution is not enough to completely neutralize the acidic impurities. The system will automatically add additional alkali solution until the pH value rises to and stabilizes at 10. This pH value setting takes into account the need to remove acidic impurities and the factor of avoiding excessive alkali solution. On the contrary, if the pH value exceeds 10, it means that there is a risk of excessive alkali solution. At this time, the system will reduce the amount of alkali solution added to maintain the pH value at 10. Through this dynamic feedback control method, it can not only ensure the effective removal of acidic impurities, but also prevent other problems caused by excessive alkali solution.
[0048] The fraction of the previous step is washed with 10-20% sodium hydroxide solution to remove the methyl sulfide vapor and acidic impurities. This step mainly controls the pH value of the aqueous phase to be 10. If the pH value of the aqueous phase is lower than 10, alkali solution should be added dropwise until the pH value is 10. If the pH value of the aqueous phase is higher than 10, it means that too much alkali has been used and the amount should be reduced. The material ratio is controlled to be 1:1 (methyl sulfide fraction of the previous step: 10% alkali solution = 1:1, volume ratio, in ml). The yield of this step is about 90% or more. When the crude methyl sulfide is unstable, this method can efficiently remove acidic impurities.
[0049] For example: According to the composition and properties of dimethyl sulfide after distillation, the optimal alkali concentration range for liquid alkali treatment is determined to be 10-20% sodium hydroxide solution. The dimethyl sulfide after distillation is fully mixed with the alkali solution in a volume ratio of 1:1 to form a uniform liquid phase. The pH value of the mixed solution is monitored in real time by an online pH detector. When the pH value is lower than 10, additional alkali solution is automatically added until the pH value reaches and stabilizes above 10. If the pH value exceeds 10, the amount of alkali solution added is reduced, and the rate and amount of alkali solution addition are dynamically adjusted through the feedback control system to maintain the optimal pH range.
[0050] Step S104, distilling the dimethyl sulfide after alkali washing again to remove excess water to obtain high-purity dimethyl sulfide.
[0051] The product of the previous step is distilled and purified, the tower top temperature is controlled at 37-39°C, and the component steam is collected and condensed to obtain the product methyl sulfide. This step is mainly intended to control the water content and further control the purity of methyl sulfide. The yield of this step is 90%.
[0052] According to the operating parameters of the distillation tower, the top temperature setting value range is 37-39℃. The temperature sensor is used to detect the top temperature of the distillation tower in real time, and the detected temperature data is transmitted to the control system. The control system receives the real-time temperature data from the temperature sensor to determine whether the current temperature is within the set range. If the temperature is higher than the upper limit of the set range, the control system issues an instruction to lower the temperature by adjusting the heating power of the distillation tower; if the temperature is lower than the lower limit of the set range, the control system issues an instruction to increase the heating power of the distillation tower to increase the temperature. By continuously adjusting the heating power, the top temperature of the tower is stabilized in the range of 37-39℃ to ensure that the distillation process is carried out under the optimal temperature conditions. A condenser is set at the top of the tower to condense the dimethyl sulfide vapor with the temperature controlled within the optimal range into liquid and collect it. The collected dimethyl sulfide product is tested for real-time purity by an online purity analyzer to obtain product purity data. The product purity data is transmitted to the control system, and the control system determines whether the product is qualified according to the preset purity standard. If the product purity reaches above 99%, it will be transported to the finished product tank for storage; if the purity is lower than 99%, it will be re-transported to the distillation tower for further purification until it meets the standard.
[0053] Implementation Case 1:
[0054] Circulation extraction experiment water-ether ratio = 1:1 comparison: take 600g of workshop methyl sulfide residual liquid, 600g of water, mix them evenly, place them in a water bath, stir and heat them, when the temperature rises to 30°C, pass the gas into a condenser for condensation and collection; when the temperature rises to 50°C, the distillation ends, and the fraction is sampled; take 200g of the above fraction and 200g of water, mix them evenly, place them in a water bath, stir and heat them, when the temperature rises to 30°C, bubbles begin to appear, and pass the gas into a condenser for condensation Collect; when the temperature reaches 50°C, the distillation is completed, the fraction is sampled, 200g of water is added to the fraction, and the mixture is thoroughly mixed. Then, a NaOH (10%-20%) solution is added dropwise to the mixture, and the pH is detected to be above 10. The water bath is heated for distillation, and the fraction is condensed and collected. When the temperature reaches 50°C, the distillation is completed, and the fraction is sampled for testing. Methanol is not detected; methyl mercaptan is not detected; dimethyl sulfide content is 99.95%; water content: 0.05%.
[0055] Implementation Case 2:
[0056] Circulation extraction experiment water-ether ratio = 1.5:1 comparison: take 600g of workshop methyl sulfide residual liquid, 1200g of water and mix them evenly, place them in a water bath, stir and heat them, when the temperature rises to 30°C, bubbles begin to appear, and the gas is passed into a condenser for condensation and collection; when the temperature rises to 50°C, the distillation ends, the fraction is sampled, 300g of water is added to the above fraction, mixed evenly, and then NaOH (10%-20%) solution is added dropwise to the above mixed solution, and its PH is detected to reach more than 10, the water bath is heated for distillation, the fraction is condensed and collected, when the temperature reaches 50°C, the distillation ends, the fraction is sampled and tested, methanol: not detected; methyl mercaptan: not detected; dimethyl sulfide content 99.94%; water content: 0.06%.
[0057] The present invention provides a method for purifying dimethyl disulfide. The method comprises the following steps: extracting crude dimethyl sulfide synthesized from methanol and hydrogen sulfide, removing unreacted methanol and other impurities, removing trace amounts of high-boiling-point substances in dimethyl sulfide through a distillation process, converting the generated byproduct methyl mercaptan into sodium methyl mercaptan through a liquid alkali process, thereby eliminating the dimethyl sulfide system, and finally distilling again to remove excess water. Dimethyl sulfide with a content greater than 99.9% can be obtained.
[0058] The dimethyl sulfide prepared by the above-mentioned purification method of cyclic extraction of high-purity dimethyl sulfide provided by the present invention can obtain dimethyl sulfide with a content of more than 99.9%. High-purity dimethyl sulfide is crucial for synthesizing high-quality dimethyl sulfoxide, and dimethyl sulfide can achieve continuous production with high purity.
[0059] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A purification method for cyclic extraction of high-purity dimethyl sulfide, characterized in that: The method comprises: The crude dimethyl sulfide synthesized from methanol and hydrogen sulfide is extracted to remove unreacted methanol impurities; The extracted dimethyl sulfide is distilled to remove alkane impurities; The dimethyl sulfide after distillation is treated with liquid alkali to remove acidic impurities; The dimethyl sulfide after alkali washing is distilled again to remove excess water to obtain high-purity dimethyl sulfide.
2. The purification method of cyclic extraction of high-purity dimethyl sulfide according to claim 1, characterized in that: The crude dimethyl sulfide synthesized from methanol and hydrogen sulfide is extracted to remove unreacted methanol impurities, comprising: The extraction process uses water as an extractant, the mass ratio of water to crude dimethyl sulfide is 1:1-1.5:1, the extraction temperature is not higher than 30°C, and the methanol impurity content is controlled to be lower than 0.1% through cyclic extraction.
3. The purification method of cyclic extraction high-purity dimethyl sulfide according to claim 2, characterized in that: The mass ratio of water to crude dimethyl sulfide is 1:
1.
4. The method for purifying high-purity dimethyl sulfide by cyclic extraction according to claim 2, characterized in that: The mass ratio of water to crude dimethyl sulfide is 1.5:
1.
5. The purification method of cyclic extraction of high-purity dimethyl sulfide according to claim 2, characterized in that: The extraction process uses water as an extractant, the mass ratio of water to crude dimethyl sulfide is 1:1 to 1.5:1, the extraction temperature is not higher than 30° C., and the methanol impurity content is controlled to be less than 0.1% by cyclic extraction, including According to the stoichiometric ratio of methanol and hydrogen sulfide, they are mixed and heated to a certain temperature in a chemical reactor to obtain a crude dimethyl sulfide solution; The crude dimethyl sulfide solution and the extractant were mixed in a mass ratio of 1:1, then heated in a water bath and stirred evenly, and when the temperature was raised to 30°C, the gas was passed into a condenser for condensation and collection; The extraction step is cyclic, wherein the mass ratio of water to crude dimethyl sulfide is 1:1 for the first extraction, and the mass ratio of the aqueous phase after the first extraction to crude dimethyl sulfide is 1:1 for the second extraction, and the cycle is repeated until the methanol impurity is below 0.1%.
6. The method for purifying high-purity dimethyl sulfide by cyclic extraction according to claim 1, characterized in that: The method of distilling the extracted dimethyl sulfide to remove alkane impurities therein comprises: The temperature range of the distillation operation is that the bottom temperature is not higher than 50°C, and the outlet gas temperature is between 37 and 39°C. The extracted dimethyl sulfide liquid is sent to the distillation tower, the bottom temperature is controlled not to exceed 50°C, and the outlet gas temperature is maintained at 37 to 39°C.
7. The method for purifying high-purity dimethyl sulfide by cyclic extraction according to claim 1, characterized in that: The dimethyl sulfide after distillation is treated with liquid alkali to remove acidic impurities, comprising: According to the composition and properties of dimethyl sulfide after distillation, the optimal concentration range of alkali solution for liquid alkali treatment is determined to be 10-20% sodium hydroxide solution; The dimethyl sulfide after distillation and the alkali solution are fully mixed in a volume ratio of 1:1 to form a uniform liquid phase; The pH value of the mixed solution is monitored in real time by an online pH detector. When the pH value is lower than 10, additional alkali solution is automatically added until the pH value reaches and stabilizes at 10; If the pH value exceeds 10, reduce the amount of alkali solution added to maintain the pH value at 10.
8. Dimethyl sulfide prepared by the purification method of cyclic extraction of high-purity dimethyl sulfide according to any one of claims 1 to 7.