Extraction and recovery method of dimethyl sulfoxide

Abstract

The invention relates to an extraction and recovery method of dimethyl sulfoxide, which comprises the following steps: measuring the pH value of a mixed waste liquid containing dimethyl sulfoxide, and when the pH value of the mixed waste liquid is lower than 7.0, adding a regulator to increase the pH value of the solution to 7.0 or more; mixing and fully contacting the pH-adjusted mixed waste liquid with an extraction agent, so that dimethyl sulfoxide and organic matters in the mixed waste liquid are enriched in an extraction phase, and water-soluble salt and water are enriched in a raffinate phase; further separating the extract phase through rectification to obtain a front fraction, a transition fraction and a dimethyl sulfoxide fraction; and continuously contacting the dimethyl sulfoxide fraction with an activated dehydrating agent, so that water in the dimethyl sulfoxide fraction is adsorbed on the dehydrating agent, thereby obtaining a recovered dimethyl sulfoxide product. Compared with the prior art, the method provided by the invention not only improves the recovery efficiency and purity of dimethyl sulfoxide, but also reduces the production cost, is environment-friendly, and has important industrial application value and social and economic significance.

Description

Technical Field

[0001] The invention relates to a dimethyl sulfoxide recovery method, in particular to an extraction recovery method of dimethyl sulfoxide. Background Art

[0002] Deuterated reagents are needed in the electronics industry, pharmaceutical industry, OLED panel industry, deuterated material preparation, etc. As a deuterium source, it can increase the deuterium ratio in the compound in the deuteration reaction, thereby changing certain properties of the compound. For example, deuterated luminescent organic matter is used in the panel, thereby increasing the service life of the panel.

[0003] Using dimethyl sulfoxide with a high deuterium content as a deuterium source to prepare other deuterated compounds is a common method in the OLED panel industry. The above deuteration reaction process avoids water because water will affect the deuteration reaction and reduce the yield of the reaction. In addition, if it is light water, it will also reduce the deuteration rate of the product to a certain extent, affecting the product quality.

[0004] However, after the reaction is completed, water is usually added to make the product easier to separate. Usually, after adding water, layering, filtering and other treatments, a mixed waste liquid of dimethyl sulfoxide containing no product and catalyst can be obtained, in which the content of dimethyl sulfoxide is about 30%, and it also contains water and water-soluble salts. However, the mixed waste liquid cannot be directly used again in the manufacture of OLED light-emitting materials. Treating it as a waste liquid will cause huge waste, and the dimethyl sulfoxide with a high deuterium content needs to be recovered.

[0005] Chinese patent CN115607982A discloses a dimethyl sulfoxide distillation residual liquid recovery system and its recovery method, including a concentration kettle, an evaporative condenser, and a condensate collection tank. The method includes conveying the residual liquid to the concentration kettle, and after reaching a preset liquid level, making the pressure and temperature in the kettle reach a first preset value, waiting for the liquid level to drop, and then passing deionized water into the kettle to form a solid-liquid separation of residue and concentrated liquid, opening the residue discharge port to discharge the residue, and then opening the first liquid discharge port to discharge the concentrated liquid into the condensate collection tank. However, for homogeneous dimethyl sulfoxide mixed waste liquid, after concentration and passing deionized water, solid-liquid separation does not occur, so this method cannot recover dimethyl sulfoxide in the mixed waste liquid. In addition, the invention cannot reduce the water content.

[0006] Chinese patent CN102093268A discloses a method for purifying chromatographic grade organic solvent dimethyl sulfoxide, which includes stirring the raw material dimethyl sulfoxide with activated alumina, removing impurities therein by adsorption, distilling under reduced pressure in the presence of a desiccant, and storing the effluent in a tank filled with 4A molecular sieve. The raw material of this patent is dimethyl sulfoxide with a purity of 99.5%. The process cannot purify dimethyl sulfoxide and cannot process raw materials with high water content and salt content.

[0007] Chinese patent CN104592067A discloses a method for recycling dimethyl sulfoxide waste residue, wherein the first-stage extraction is to separate dimethyl sulfone and dimethyl sulfoxide with the extractant benzene, and then recover benzene, dimethyl sulfoxide and dimethyl sulfoxide products respectively by distillation and condensation; the second-stage extraction is to separate the first-stage extraction solid phase into benzene residual liquid containing dimethyl sulfone and dimethyl sulfoxide with the extractant methanol, and then recover the extractant methanol and benzene residual liquid respectively by distillation and condensation, and return the benzene residual liquid to the front-stage distillation tower; the second-stage extraction solid phase is dissolved with water, air or oxidant is introduced to oxidize sodium nitrite into sodium nitrate, and then evaporate and crystallize to extract inorganic components. This patent uses a combination of extraction and distillation to treat waste residue containing dimethyl sulfoxide, and dimethyl sulfoxide therein can be recovered, but the benzene extractant is non-polar, and the extraction efficiency of dimethyl sulfoxide in the mixed waste liquid described in the patent is very low, and it cannot be used to recover dimethyl sulfoxide in the mixed waste liquid.

[0008] Chinese patent CN102225904A discloses a recovery and refining device and separation method for dimethyl sulfoxide, including a primary dehydration tower, a scraped film evaporator, a primary distillation intermediate tank, a secondary dehydration tower and a DMSO refining tower, wherein the primary dehydration tower is connected to the primary distillation intermediate tank, the scraped film evaporator is connected to the primary distillation intermediate tank, and then the secondary dehydration tower and the DMSO refining tower are connected in sequence. This patent is used to recover dimethyl sulfoxide in a polymer solution. For the mixed waste liquid described in the present invention, it is impossible to handle the situation where salts precipitate during dehydration; in addition, the method disclosed in this patent cannot handle mixed waste liquids with complex compositions, such as mixed waste liquids containing multiple organic impurities with boiling points lower and higher than DMSO.

[0009] At present, mixed waste liquid is difficult to recycle, and due to its complex components, it is difficult to achieve the quality of fresh dimethyl sulfoxide after recycling, especially the water content is high. Summary of the invention

[0010] The purpose of the present invention is to provide a method for extracting and recovering dimethyl sulfoxide in order to solve the above problems, which not only improves the recovery efficiency and purity of dimethyl sulfoxide, but also reduces the production cost, is environmentally friendly, and has important industrial application value and social and economic significance.

[0011] The purpose of the present invention is achieved through the following technical solutions:

[0012] The present invention provides a method for extracting and recovering dimethyl sulfoxide, comprising the following steps:

[0013] S1. Acid-base adjustment: measure the pH of the mixed waste liquid containing dimethyl sulfoxide. When the pH of the mixed waste liquid is lower than 7.0, add a regulator to increase the pH of the solution to 7.0 or above;

[0014] S2, extraction: the mixed waste liquid after adjusting the pH is mixed with the extractant and fully contacted, so that the dimethyl sulfoxide and organic matter in the mixed waste liquid will be enriched in the extraction phase, and the water-soluble salt and water will be enriched in the raffinate phase;

[0015] S3, distillation: further separating the extract phase by distillation to obtain a front fraction, a transition fraction, and a dimethyl sulfoxide fraction;

[0016] S4, dehydration: continuously contacting the dimethyl sulfoxide fraction with the activated dehydrating agent, so that water in the dimethyl sulfoxide fraction is adsorbed on the dehydrating agent to obtain a recovered dimethyl sulfoxide product.

[0017] Further, in S1, the mixed waste liquid includes dimethyl sulfoxide and impurities, and the impurities include organic matter, water-soluble salts and / or alkalis, and water;

[0018] Part or all of the protium atoms in the molecular structure of the dimethyl sulfoxide are replaced by deuterium atoms, and the molecular formula of the dimethyl sulfoxide is C2H x D y OS, where H is a protium atom, D is a deuterium atom, x+y=6, 0≤x≤6, 0≤y≤6;

[0019] The dimethyl sulfoxide component in the dimethyl sulfoxide mixed waste liquid satisfies 0.8≤y / (x+y)≤0.999.

[0020] Furthermore, in S1, the mass content of dimethyl sulfoxide in the mixed waste liquid is 10% to 60%, the mass content of organic matter is 0% to 20%, the mass content of water-soluble salt is 5% to 50%, and the mass content of water is 30% to 80%.

[0021] Further, in S1, the organic matter is an organic matter other than dimethyl sulfoxide that can exist in a homogeneous form in the mixed waste liquid, and the organic matter is a single substance or a mixture;

[0022] When the organic matter is a mixture, the mass content of the components with a boiling point lower than dimethyl sulfoxide in the organic matter is not less than 50%.

[0023] Further, in S1, the regulator is one of a salt and / or a base, or an aqueous solution of a salt and / or a base, wherein the cation part of the salt and / or the base is selected from Na + , K + NH4 + , Ca + Mg 2+ One or more of the salts, the anion portion of the salt is selected from CO3 2- 、HCO3 - One or more of .

[0024] Furthermore, in S1, a regulator is added to control the pH of the solution between 7 and 9.

[0025] Further, in S2, the selection of the extractant satisfies:

[0026] 1) The boiling point at normal pressure is lower than that of dimethyl sulfoxide,

[0027] 2) It is immiscible with water at the extraction operating temperature,

[0028] 3) It can form the lowest azeotrope with water.

[0029] 4) It has polarity,

[0030] The normal pressure boiling point of the extractant is lower than 120° C., the solubility in water at room temperature is lower than that of being easily soluble, and the normal pressure azeotropic temperature of the lowest azeotrope formed with water is lower than 90° C.

[0031] Further, in S2, the extraction operation temperature is 10-30°C, the operation pressure is 100-150 kPaA, and the mass ratio of the solution to be extracted to the extractant is 0.5:1-3:1;

[0032] The extraction method can be intermittent or continuous;

[0033] When intermittent extraction is used, the number of extractions is 1 to 3, and the extraction phases obtained in each extraction are combined as the final extraction phase.

[0034] The extraction phase comprises dimethyl sulfoxide, organic matter and water, wherein the mass content of water is less than 5%.

[0035] Further, in S3, the transition fraction contains an extractant, dimethyl sulfoxide, and components in organic matter having a boiling point lower than dimethyl sulfoxide;

[0036] The mass content of dimethyl sulfoxide in the dimethyl sulfoxide fraction is more than 99%, the sum of the contents of other organic matter and extractant does not exceed 0.5%, and the water content does not exceed 1%;

[0037] The components in the organic matter with boiling points lower than dimethyl sulfoxide are removed in the front fraction or transition fraction;

[0038] The oil phase obtained in the front fraction stage includes an extractant, and the oil phase is directly reused as an extractant or is reused after being refined and purified.

[0039] Further, in S3, the pressure of the front fraction stage is normal pressure or reduced pressure;

[0040] When using reduced pressure, the bottom temperature of the tower is lower than 130℃;

[0041] The operating pressure of the front fraction stage is not less than 20 kPaA, the temperature of the tower top is not less than 0°C, and the reflux ratio is 1:1 to 5:1;

[0042] The operating pressure of the transition fraction stage is 2-20 kPaA, the temperature of the top of the tower is 0-110°C, and the reflux ratio is 3:1-10:1;

[0043] The operating pressure of the dimethyl sulfoxide fraction stage is 0.1-5 kPaA, the temperature of the tower top is 25-105°C, and the reflux ratio is 0.2:1-3:1.

[0044] Compared with the prior art, the present invention has the following technical advantages:

[0045] 1) The present invention provides an efficient and environmentally friendly dimethyl sulfoxide extraction and recovery method, which achieves the goal of high-purity recovery of dimethyl sulfoxide from complex mixed waste liquid through acid-base adjustment, extraction, distillation and dehydration steps. This method not only significantly improves the recovery rate and product purity of dimethyl sulfoxide, but also reduces energy consumption and production costs by optimizing operating conditions and process flow, and has significant industrial application value.

[0046] 2) By using a specific extractant and distillation technology, the present invention can effectively remove water and other impurities in dimethyl sulfoxide to obtain a high-quality product with a purity higher than 99.5%. In addition, by using an extractant that is azeotropic with water, the method simplifies the dehydration step in the distillation process, further improving the dehydration efficiency and product purity. The use of an extraction method reduces the energy consumption of water removal and improves the efficiency, with an extraction rate of more than 95%. The present invention is of great significance in improving resource utilization and protecting the environment.

[0047] 3) The recovery process of the present invention has good adaptability and flexibility, and can process mixed waste liquids with complex components and different concentrations. By accurately controlling acid-base adjustment, extraction conditions and distillation operations, the method ensures a high recovery rate of dimethyl sulfoxide and a high purity of the product, while reducing energy consumption and waste emissions in the production process. The recovery process can process mixed waste liquids with complex components, and the recovery rate of dimethyl sulfoxide in the mixed waste liquid is higher than 80%. The present invention is not only technologically advanced, but also has obvious advantages in economic and environmental benefits, and provides an efficient and environmentally friendly solution for the recovery and reuse of dimethyl sulfoxide. DETAILED DESCRIPTION

[0048] In general, the method for recovering dimethyl sulfoxide from mixed waste liquid in the present invention comprises:

[0049] Description of waste liquid composition

[0050] The dimethyl sulfoxide in the mixed waste liquid of the present invention has part or all of the protium atoms in its molecular structure replaced by deuterium atoms, and also contains water and a dehydrating agent.

[0051] In specific implementation, the dehydrating agent is one or a mixture of activated alumina and molecular sieve.

[0052] In a specific implementation, the molecular formula of the dimethyl sulfoxide is C2H x D y OS, where H is a protium atom, D is a deuterium atom, x+y=6, 0≤x≤6, 0≤y≤6,

[0053] In a specific implementation, the impurities include organic matter (except dimethyl sulfoxide), water-soluble salts and / or alkalis, and water, and the water is derived from the impurities in the dimethyl sulfoxide mixed waste liquid.

[0054] In a specific implementation, the dimethyl sulfoxide component in the dimethyl sulfoxide mixed waste liquid satisfies 0.8≤y / (x+y)≤0.999.

[0055] At the hydrogen atom level, the dimethyl sulfoxide component in the mixed wastewater is a mixture, that is, a mixture of C2H1D5OS, C2D6OS, etc. From a statistical point of view, 0.8≤y / (x+y)≤0.999 in the mixture. )

[0056] The mass content of dimethyl sulfoxide is above 99.5%, and the content of other organic matter does not exceed 0.5%.

[0057] When the melting point of the dimethyl sulfoxide is detected by differential scanning calorimetry (DSC) under the protection of inert gas, the absolute value of the deviation from the standard melting point (18.3° C.) is no more than 1° C.

[0058] The dimethyl sulfoxide mixed waste liquid includes dimethyl sulfoxide and impurities, wherein the impurities include organic matter, water-soluble salts and / or alkalis, and water. Part or all of the protium atoms in the molecular structure of the dimethyl sulfoxide are replaced by deuterium atoms, and the molecular formula of the dimethyl sulfoxide is C2H x D y OS, wherein H is a protium atom, D is a deuterium atom, x+y=6, 0≤x≤6, 0≤y≤6. The dimethyl sulfoxide component in the dimethyl sulfoxide mixed waste liquid satisfies 0.8≤y / (x+y)≤0.999.

[0059] In a specific implementation, the cation of the water-soluble salt / base includes Na + , Ca + , K + Mg 2+ 、Al 3+ , Fe 2+ , Fe 3+ , Cu 2+ NH4 + 、Zn 2+One or more of, anions include SO4 2- 、CO3 2- , Cl - 、NO3 - 、HCO3 - 、HSO4 - 、SO3 2- 、HSO3 2- PO4 3- 、HPO4 2- 、H2PO4 - Br - , F-, OH-. The mass content of dimethyl sulfoxide in the mixed waste liquid is 10% to 60%, the mass content of other organic matter is 0% to 20%, the mass content of water-soluble salt is 5% to 50%, and the mass content of water is 30% to 80%.

[0060] In a specific implementation, the organic matter is an organic matter other than dimethyl sulfoxide that can exist in a homogeneous form in the mixed waste liquid, and can be a single substance or a mixture.

[0061] In specific implementations, impurities may also include insoluble matter in particle form, such as carbon powder and metal powder.

[0062] The water content in the dimethyl sulfoxide containing trace or trace moisture is difficult to be determined by Karl Fischer method (generally below 1000ppm). When dimethyl sulfoxide is liquid at a higher ambient temperature, it is very easy to absorb moisture in the air in the moisture determination process under this state, thereby affecting the measurement result of moisture, and the lower the moisture content, the greater the impact. When dimethyl sulfoxide is solid in a lower ambient temperature, it needs to be heated and dissolved before detection, and this process further aggravates the deviation of measurement. The inventor found that water content directly affects the melting point of dimethyl sulfoxide solid, and further research found that there is a correlation between moisture and melting point, and the melting point of dimethyl sulfoxide solid can accurately reflect its water content.

[0063] Recycling method:

[0064] 1) Acid-base adjustment

[0065] The reason for adjusting the pH is that DMSO is more easily thermally decomposed under acidic conditions to generate products such as methyl sulfide, dimethyl disulfide and methyl mercaptan. When the pH of the mixed waste liquid is lower than 7.0, a regulator is added to increase the pH of the solution to 7.0 or above. In the specific implementation, preferably, the pH of the solution is controlled between 7 and 9. The regulator is one or more of a salt, an alkali or a metal oxide that can consume H+ in water after dissolving in water.

[0066] In the specific implementation, the regulator is preferably a salt and / or a base, and an aqueous solution of a salt and / or a base, wherein the cation part of the salt and / or the base can be selected from Na+ , K + NH4 + , Ca + Mg 2+ One or more of the salts, the anion portion of the salt may be selected from CO3 2- 、HCO3 - More preferably, the regulator is a mixed salt and / or alkali aqueous solution, and the reaction does not generate gas and / or precipitation when added to adjust the pH.

[0067] In specific implementation, if precipitation is produced during the acid-base adjustment process and / or the mixed waste liquid contains insoluble matter, it needs to be filtered.

[0068] If the primary separation can be performed without adjusting the pH under acidic conditions, the degree of thermal decomposition can be effectively controlled by controlling the heating temperature below 90°C (although some decomposition will still occur). The temperature of the secondary separation water fraction should also be controlled below 90°C.

[0069] After adjusting the pH, the subsequent separation temperature is controlled below 120°C, and dimethyl sulfoxide will basically not be thermally decomposed.

[0070] 2) Extraction

[0071] In the specific implementation, the mixed waste liquid is mixed with the extractant and fully contacted, and the dimethyl sulfoxide and organic matter in the mixed waste liquid will be enriched in the extraction phase, and the water-soluble salts and water will be enriched in the raffinate phase. There will be no salt precipitation during the extraction process, so the water and water-soluble salts in the mixed waste liquid can be removed efficiently. At the same time, since a large amount of water is directly removed during the extraction process, the energy consumption of the dehydration process is greatly reduced.

[0072] In the specific implementation, the extractant is a substance that meets the following conditions (it can be one or a mixture of multiple substances):

[0073] 1) The boiling point at normal pressure is lower than that of dimethyl sulfoxide

[0074] 2) Immiscible with water at extraction operating temperature

[0075] 3) It can form the lowest azeotrope with water

[0076] 4) It has polarity.

[0077] In a specific implementation, the normal pressure boiling point of the extractant is lower than 120°C, the solubility in water at room temperature is lower than that of being easily soluble, and the normal pressure azeotropic temperature of the lowest azeotrope formed with water is lower than 90°C.

[0078] In a specific implementation, the extractant is preferably a mixture of one or more of dichloromethane, ethyl acetate, chloroform, isopropyl acetate, methyl isobutyl ketone and isopropyl ether.

[0079] In the specific implementation, the operating temperature is 10-30° C., and the operating pressure is 100-150 kPaA. The mass ratio of the solution to be extracted (which can be a mixed waste liquid or the last raffinate phase) to the extractant is 0.5:1-3:1.

[0080] In specific implementation, the extraction method can be intermittent or continuous; in the case of intermittent extraction, the number of extractions is 1 to 3 times, and the extraction phases obtained in each time are combined as the final extraction phase.

[0081] The extraction apparatus may be any apparatus that allows contact and / or mixing of the two phases.

[0082] The extraction phase comprises dimethyl sulfoxide, organic matter and water, wherein the water content is less than 5%.

[0083] 3) Distillation separation

[0084] In the specific implementation, the extraction phase is further separated by distillation, and the fore fraction, transition fraction and dimethyl sulfoxide fraction can be obtained successively at the top of the tower. In the distillation process, at least in the fore fraction stage, the vapor at the top of the tower may be cooled to a liquid phase before phase separation.

[0085] As the extraction proceeds, the water content in the tower decreases, the extractant content at the top of the tower further increases, and the water phase gradually decreases until it disappears.

[0086] In a specific implementation, the transition fraction contains extractant, dimethyl sulfoxide, and components with a boiling point lower than dimethyl sulfoxide in organic matter. The mass content of dimethyl sulfoxide in the dimethyl sulfoxide fraction is more than 99%, the sum of the contents of other organic matter and extractant does not exceed 0.5wt%, and the water content does not exceed 1wt%. The components with a boiling point lower than dimethyl sulfoxide in organic matter are removed in the front fraction or transition fraction.

[0087] During specific implementation, in each stage, if the vapor at the top of the tower is cooled to a liquid phase and then separated into phases, the water phase does not participate in the reflux and is all produced, and a part of the oil phase is refluxed and the other part is produced.

[0088] In specific implementation, the oil phase obtained in the front fraction stage has a high content of extractant, which can be directly reused or reused after being refined.

[0089] In specific implementation, the pressure of the front fraction stage can be normal pressure or reduced pressure; preferably reduced pressure, and the temperature of the tower bottom is lower than 130°C. Specifically, the pressure is not lower than 20kPaA, the temperature of the tower top is not lower than 0°C, and preferably the tower top temperature is 30-75°C. The reflux ratio is 1:1-5:1.

[0090] In a specific implementation, the pressure of the transition fraction stage is 2-20 kPaA, the temperature of the tower top is 0-110°C, and the reflux ratio is 3:1-10:1. In a specific implementation, the tower top temperature is preferably 30-80°C.

[0091] In a specific implementation, the pressure of the dimethyl sulfoxide fraction stage is 0.1-5 kPaA, the temperature of the tower top is 25-105° C., and the reflux ratio is 0.2:1-3:1.

[0092] In specific implementation, the distillation tower is a packed tower or a plate tower, preferably a packed tower, more preferably a packed tower filled with structured packing inside, preferably a packed tower filled with metal wire mesh structured packing inside.

[0093] Note: Generally, when the mass fraction of dimethyl sulfoxide in the distillate is higher than 2%, it is the transition distillation stage; when the mass fraction of dimethyl sulfoxide in the distillate reaches more than 99% and the sum of the contents of other organic matter and extractant does not exceed 0.5% (generally the rest is water content not exceeding 1%), it is the dimethyl sulfoxide distillation stage; when the mass fraction of other organic matter + extractant in the distillate is higher than 0.5%, the extraction stops.

[0094] Due to the addition of the extractant, it will form an azeotrope with water during the distillation process, which is more conducive to the removal of water in DMSO.

[0095] Distillation separation can also be carried out by continuous distillation separation using multiple towers in series.

[0096] Regarding the description of phase separation, depending on the reflux ratio and the extractant, the top of the tower may or may not separate into phases, but if it does separate into phases, it will be in the front distillation stage.

[0097] 4) Dehydration

[0098] In a specific implementation, the dimethyl sulfoxide fraction is continuously contacted with the activated dehydrating agent so that the water therein is adsorbed on the dehydrating agent. The operating temperature of the dehydration is 20 to 50°C, preferably 25 to 35°C in a specific implementation. The contact method can be static immersion or continuous dehydration. When static immersion, the mass ratio of the dehydrating agent to the dimethyl sulfoxide fraction is 1:2 to 1:20; when continuous dehydration is performed, the residence time of dimethyl sulfoxide is 10 to 60 minutes. Fixed bed dehydration is preferred for continuous dehydration.

[0099] In specific implementation, the dehydrating agent can be a mixture of one or more of activated alumina, molecular sieve, and silica gel.

[0100] In a specific implementation, preferably, when the water content in the dimethyl sulfoxide fraction reaches 1% or less, the liquid portion is continuously contacted with another activated dehydrating agent, and the dehydrating agent is a mixture of activated alumina and molecular sieves in a mass ratio of 1:1 to 1:5; when the water content in the dimethyl sulfoxide fraction reaches 0.5% or less, the liquid portion is mixed with another activated dehydrating agent, and the dehydrating agent is 4A and / or 5A molecular sieves.

[0101] 5) Melting point evaluation and packaging

[0102] When the melting point of the dimethyl sulfoxide is detected by differential scanning calorimetry (DSC) under the protection of inert gas, the absolute value of the deviation from the standard melting point (18.3° C.) is no more than 1° C.

[0103] In the specific implementation, after the purity, other organic matter content and melting point of dimethyl sulfoxide are qualified, the liquid part is transferred to the packaging container. The packaging container also contains another activated dehydrating agent, and the mass ratio of the dehydrating agent to dimethyl sulfoxide is 1:10 to 1:20. The packaging container is the dimethyl sulfoxide solid-liquid mixture product. Preferably, the dehydrating agent is 4A molecular sieve.

[0104] Note: During the dehydration process, the dehydrating agent does not need to be replaced (if the amount of dehydrating agent added is sufficient), but the contact time will be very long.

[0105] The present invention is described in detail below in conjunction with specific embodiments, but is by no means intended to limit the present invention. Features such as preparation methods, materials, structures or composition ratios not explicitly described in this technical solution are considered to be common technical features disclosed in the prior art.

[0106] Example 1

[0107] Mixed waste liquid

[0108] The dimethyl sulfoxide mixed waste liquid includes dimethyl sulfoxide and impurities, wherein the impurities include organic matter (except dimethyl sulfoxide), water-soluble salts and water. The y / (x+y) of the dimethyl sulfoxide component in the mixed waste liquid is 0.90.

[0109] The cations of water-soluble salts include Na + , Ca + , K + , anions include SO4 2- , Cl - 、NO3 - The mixed waste liquid has a dimethyl sulfoxide content of 30% by mass, an organic matter (except dimethyl sulfoxide) content of 0.5% by mass, a water-soluble salt content of 10% by mass, a water content of 59% by mass, and also contains 0.5% by mass of millimeter to micron-sized carbon powder particles.

[0110] Among the organic substances other than dimethyl sulfoxide, the component with a boiling point lower than that of dimethyl sulfoxide is ethyl acetate, which accounts for 80% by mass, and the rest are components with a boiling point higher than that of dimethyl sulfoxide.

[0111] Acid-base regulation

[0112] The pH of the dimethyl sulfoxide mixed waste liquid was neutral, and therefore was not adjusted.

[0113] There are insoluble substances in the mixed waste liquid, and the mixed waste liquid is filtered to remove the insoluble substances. The filter element is made of PTFE material with a filtration accuracy of 0.25 microns.

[0114] extraction

[0115] The extractant is dichloromethane, and the intermittent extraction method is adopted. The extraction equipment is a kettle with stirring, and the extraction times are 2 times. The filtered mixed waste liquid is fully mixed with the extractant at a mass ratio of 1:2, and after standing for phase separation, the raffinate phase is fully mixed with the extractant at a mass ratio of 1:1, and after standing for phase separation again, the two extraction phases are combined to obtain the final extraction phase, and the two raffinate phases are combined to obtain the final raffinate phase. The operating temperature of the extraction process is 25°C and the pressure is 150kPaA.

[0116] The extraction phase was analyzed, wherein the water content was less than 0.5%; the raffinate phase was analyzed, wherein the dimethyl sulfoxide content was less than 0.5%, and the extraction rate of dimethyl sulfoxide reached 99%.

[0117] Distillation separation

[0118] The final extract phase is further separated by intermittent distillation. The distillation tower is filled with structured packing, and the packing height is 2 meters. The fore fraction, transition fraction and dimethyl sulfoxide fraction can be obtained at the top of the tower.

[0119] The pressure of the front fraction stage is normal pressure, and the tower top temperature is 37°C. The azeotrope of dichloromethane and water is enriched at the tower top, and the collected liquid phase is separated after cooling at the tower top. The water phase is extracted as waste liquid, part of the oil phase is refluxed, and the other part is extracted, and the reflux ratio is 2:1. As the extraction proceeds, the water content in the tower decreases, the dichloromethane content at the tower top increases, and the tower top temperature rises to 39°C, at which time the reflux ratio is still 2:1.

[0120] When the mass fraction of dimethyl sulfoxide in the distillate reaches 2%, it enters the transition distillation stage; the pressure of the transition distillation stage is 20kPaA, the reflux ratio is 10:1, and the top temperature gradually increases from 3°C to 115°C as the top of the tower is continuously produced.

[0121] When the mass fraction of dimethyl sulfoxide in the distillate reaches 99% and the sum of the contents of other organic matter and the extractant is less than 0.5%, the dimethyl sulfoxide distillation stage is entered (the rest is water); the pressure of the dimethyl sulfoxide distillation stage is 1 kPaA, and the top temperature of the tower increases from 50°C to 66°C as the top of the tower is continuously produced. The reflux ratio is 3:1, and the production is stopped when the sum of the contents of other organic matter and the extractant in the distillate is higher than 0.5%.

[0122] Deep dehydration

[0123] First, the dimethyl sulfoxide fraction is continuously dehydrated through a fixed bed, in which the activated dehydrating agent D1 is loaded, the residence time of the dimethyl sulfoxide fraction is 60 minutes, and the operating temperature is 35°C. The dehydrated material is A1, and the water content of A1 is 0.19% by Karl Fischer method. D1 is activated alumina.

[0124] A1 is then mixed with the activated dehydrating agent D2 and placed in a sealed container for 24 hours at an operating temperature of 25°C. The mass ratio of the dehydrating agent D2 to A1 is 1:5. The dehydrated material is A2. D2 is a 5A molecular sieve.

[0125] Melting point evaluation and packaging

[0126] A small amount of the liquid portion of A2 was taken in a dry environment without contact with air and the temperature was gradually cooled to 0° C. When the melting point of the dimethyl sulfoxide was detected using a differential scanning calorimeter (DSC) under inert gas protection, the absolute value of the deviation from the standard melting point (18.3° C.) was 0.5° C.

[0127] In a dry environment, the liquid part of A2 is quickly transferred into a 20L fluoroplastic barrel of the product packaging container by a closed transfer method without contact with air, and the operating temperature is 25°C. The product packaging container is pre-displaced with dry nitrogen, and the activated dehydrating agent D4 is placed. The mass ratio of dehydrating agent D4 to A2 is 1:20. The dimethyl sulfoxide solid-liquid mixture product in the packaging container is P1. D4 is 4A molecular sieve.

[0128] Preparation of deuterated dimethyl sulfoxide

[0129] In a dry environment, a 200-mesh 316L stainless steel filter is used to separate the solid in the dimethyl sulfoxide solid-liquid mixture P1 to obtain a dimethyl sulfoxide clear liquid. The clear liquid is mixed with other deuterated dimethyl sulfoxide (y / (x+y) value is 99.9%) at a ratio of 1:10 to obtain deuterated dimethyl sulfoxide, whose y / (x+y) value is 99%, which can be used in the deuteration reaction of OLED light-emitting materials.

[0130] Example 2

[0131] Deep dehydration

[0132] First, the dimethyl sulfoxide fraction was mixed with the activated dehydrating agent D1 and then sealed and placed in contact for 72 hours. The operating temperature was 25°C, and the mass ratio of the dehydrating agent D1 to the dimethyl sulfoxide fraction was 1:2. The dehydrated material was A1, and the water content of A1 was 0.11% using the Karl Fischer method. D1 was a mixture of activated alumina and 3A molecular sieve in a mass ratio of 5:1.

[0133] Then the liquid part of A1 is mixed with the activated dehydrating agent D2 and then sealed and placed in contact for 96 hours. The operating temperature is 30°C and the mass ratio of the dehydrating agent D2 to A1 is 1:5. The dehydrated material is A2. D2 is a 4A molecular sieve.

[0134] Melting point evaluation and packaging

[0135] In a dry environment, take a small amount of the liquid portion of A2 without contact with air and gradually cool it to 0° C. Detect the melting point in the same manner as in Example 1.

[0136] In a dry environment, the liquid part of A2 is quickly transferred into a 20L fluoroplastic barrel of the product packaging container by a closed transfer method without contact with air, and the operating temperature is 25°C. The product packaging container is pre-displaced with dry nitrogen and the activated dehydrating agent D4 is placed. The mass ratio of dehydrating agent D4 to A2 is 1:15. D4 is a 4A molecular sieve.

[0137] The rest is the same as in Example 1.

[0138] The dimethyl sulfoxide solid-liquid mixture product in the packaging container is P2.

[0139] Example 3

[0140] Acid-base regulation

[0141] The mixed waste liquid of dimethyl sulfoxide includes dimethyl sulfoxide and impurities, wherein the impurities include organic matter (except dimethyl sulfoxide), water-soluble salts and water. The cations of the water-soluble salts include Na + , K + , anions include SO4 2- 、HCO3 - 、HSO4 - The pH of the mixed waste liquid of dimethyl sulfoxide was slightly acidic, and the pH was adjusted to 7.0 using a 1 mol / L aqueous solution of NaCO3.

[0142] The rest is the same as in Example 1.

[0143] The dimethyl sulfoxide solid-liquid mixture product in the packaging container is P3.

[0144] Example 4

[0145] Distillation separation

[0146] The final extract phase is further separated by intermittent distillation. The distillation tower is filled with structured packing, and the packing height is 2 meters. The fore fraction, transition fraction and dimethyl sulfoxide fraction can be obtained at the top of the tower.

[0147] The pressure of the front fraction stage is normal pressure, and the tower top temperature is 37°C. The azeotrope of dichloromethane and water is enriched at the tower top, and the collected liquid phase is separated after cooling at the tower top. The water phase is extracted as waste liquid, part of the oil phase is refluxed, and the other part is extracted, and the reflux ratio is 1:1. As the extraction proceeds, the water content in the tower decreases, the dichloromethane content at the tower top increases, and the tower top temperature rises to 39°C, at which time the reflux ratio is still 1:1.

[0148] When the mass fraction of dimethyl sulfoxide in the distillate reaches 2%, it enters the transition distillation stage; the pressure of the transition distillation stage is 20kPaA, and the liquid phase collected after cooling at the top of the tower is separated into phases, the water phase is produced as waste liquid, part of the oil phase is refluxed, and the other part is produced, and the reflux ratio is 3:1. As the production proceeds, the dimethyl sulfoxide content at the top of the tower increases, the water phase gradually decreases and disappears, and the top temperature gradually rises from 3°C to 115°C.

[0149] When the mass fraction of dimethyl sulfoxide in the distillate reaches 99% and the sum of the contents of other organic matter and the extractant is less than 0.5%, the dimethyl sulfoxide distillation stage is entered (the rest is water); the pressure of the dimethyl sulfoxide distillation stage is 1 kPaA, and the top temperature of the tower increases from 50°C to 66°C as the top of the tower is continuously produced. The reflux ratio is 0.2:1, and the production is stopped when the sum of the contents of other organic matter and the extractant in the distillate is higher than 0.5%.

[0150] The rest is the same as in Example 1.

[0151] The dimethyl sulfoxide solid-liquid mixture product in the packaging container is P4.

[0152] Example 5

[0153] extraction

[0154] The extractant is a mixture of dichloromethane and chloroform, with chloroform accounting for 5wt%. A continuous extraction method is used, the extraction equipment is a centrifugal extractor, and the number of extractions is 1 (i.e., single stage). The operating temperature of the extraction process is 10°C, the pressure is 100kPaA, and the mass ratio of the filtered mixed waste liquid to the extractant is 1:1.

[0155] After extraction by a centrifugal extractor, an extract phase and a raffinate phase are obtained. The extract phase is analyzed, and the water content is less than 0.2wt%; the raffinate phase is analyzed, and the dimethyl sulfoxide content is less than 0.3wt%, and the extraction rate of dimethyl sulfoxide reaches 99.6%.

[0156] The rest is the same as in Example 1.

[0157] The dimethyl sulfoxide solid-liquid mixture product in the packaging container is P5.

[0158] Example 6

[0159] extraction

[0160] The extractant is methyl isobutyl ketone, and a continuous extraction method is adopted. The extraction equipment is a centrifugal extractor, and the number of extractions is 2 times (i.e., two-stage). In the first-stage centrifugal extractor, the fresh extractant contacts the solution to be extracted to obtain the first-stage extraction phase and the raffinate phase. The first-stage raffinate phase enters the second-stage centrifugal extractor and contacts the fresh extractant to obtain the second-stage extraction phase and the raffinate phase. The first-stage and second-stage extraction phases are combined to obtain the final extraction phase. The first-stage and second-stage raffinate phases are combined to obtain the final raffinate phase. The operating temperature of the two-stage extraction process is 30°C, the pressure is normal pressure, and the mass ratio of the solution to be extracted to the extractant is 1:1.

[0161] After extraction by a centrifugal extractor, the final extraction phase was analyzed, wherein the water content was less than 3.5wt%; the final raffinate phase was analyzed, wherein the dimethyl sulfoxide content was less than 2.5wt%, and the extraction rate of dimethyl sulfoxide reached 96%.

[0162] Distillation separation

[0163] The final extract phase is further separated by intermittent distillation. The distillation tower is filled with regular packing, and the packing height is 5 meters. The fore fraction, transition fraction and dimethyl sulfoxide fraction can be obtained at the top of the tower.

[0164] The pressure of the front fraction stage is 50kPaA, and the top temperature is 70℃. The azeotrope of methyl isobutyl ketone and water is enriched at the top of the tower. After cooling the top of the tower, the collected liquid phase is separated into phases. The water phase is produced as waste liquid, part of the oil phase is refluxed, and the other part is produced. The reflux ratio is 2:1. As the production proceeds, the water content in the tower decreases, the methyl isobutyl ketone content at the top of the tower increases, and the top temperature rises to 80℃. At this time, the reflux ratio is still 2:1.

[0165] When the mass fraction of dimethyl sulfoxide in the distillate reaches 2%, it enters the transition distillation stage; the pressure of the transition distillation stage is 2kPaA, the reflux ratio is 10:1, and the top temperature gradually increases from 42°C to 80°C as the top of the tower is continuously produced.

[0166] When the mass fraction of dimethyl sulfoxide in the distillate reaches 99% and the sum of the contents of other organic matter and the extractant is less than 0.5%, the dimethyl sulfoxide distillation stage is entered (the rest is water); the pressure of the dimethyl sulfoxide distillation stage is 0.5 kPaA, and the top temperature of the tower increases from 50°C to 53°C as the top of the tower is continuously produced. The reflux ratio is 0.2:1, and the production is stopped when the sum of the contents of other organic matter and the extractant in the distillate is higher than 0.5%.

[0167] The rest is the same as in Example 1.

[0168] The dimethyl sulfoxide solid-liquid mixture product in the packaging container is P6.

[0169] Comparative Example 1

[0170] extraction

[0171] The extractant is benzene, and the remaining parts of the waste liquid mixing, acid-base adjustment and extraction process are the same as those in Example 1.

[0172] The extraction phase was analyzed, wherein the water content was less than 0.4 wt %; the raffinate phase was analyzed, wherein the dimethyl sulfoxide content was 29.7 wt %, and the extraction rate of dimethyl sulfoxide was less than 0.5%.

[0173] Good extraction results cannot be achieved using benzene.

[0174] Comparative Example 2

[0175] extraction

[0176] The extractant is cyclohexane, and the remaining parts of the waste liquid mixing, acid-base adjustment and extraction process are the same as those in Example 1.

[0177] The extraction phase was analyzed, wherein the water content was less than 0.4 wt %; the raffinate phase was analyzed, wherein the dimethyl sulfoxide content was 29.4 wt %, and the extraction rate of dimethyl sulfoxide was less than 1%.

[0178] Good extraction results could not be achieved using cyclohexane.

[0179] Comparative Example 3

[0180] Acid-base regulation

[0181] The pH of the dimethyl sulfoxide mixed waste liquid is not adjusted and is kept slightly acidic.

[0182] The rest is the same as in Example 3. The dimethyl sulfoxide solid-liquid mixture product in the packaging container is P7.

[0183] Comparative Example 4

[0184] No dehydrating agent is placed in the package, and the rest is the same as in Example 1.

[0185] The dimethyl sulfoxide solid-liquid mixture product in the packaging container is P8.

[0186] Comparative Example 5

[0187] The extract phase in Example 1 was separated by a rotary evaporator. The vapor obtained by condensation and evaporation was sequentially obtained to obtain a front fraction, a transition fraction and a dimethyl sulfoxide fraction.

[0188] The pressure of the front distillation stage is normal pressure, and the top steam temperature is 37°C. The azeotrope of dichloromethane and water is in the gas phase and is completely extracted after condensation. When the mass fraction of dimethyl sulfoxide in the distillate reaches 2%, it enters the transition distillation stage. The pressure of the transition distillation stage is 20kPaA. With the continuous extraction, the top steam temperature gradually rises from 3°C to 115°C.

[0189] When the mass fraction of dimethyl sulfoxide in the distillate reaches 99% and the sum of the contents of other organic matter and extractant is less than 0.5%, the dimethyl sulfoxide distillation stage is entered (the rest is water). The pressure of the dimethyl sulfoxide distillation stage is 1 kPaA, and the top steam temperature rises from 50°C to 66°C. When the sum of the contents of other organic matter and extractant in the distillate is higher than 0.5%, the extraction is stopped.

[0190] The rest is the same as in Example 1.

[0191] The dimethyl sulfoxide solid-liquid mixture product in the packaging container is P9.

[0192]

[0193] By comparing and analyzing the embodiments and comparative examples, the following conclusions can be drawn:

[0194] Selection of extraction agent:

[0195] In Examples 1-6, dichloromethane, a mixture of dichloromethane and chloroform, and methyl isobutyl ketone were used as extractants, all of which were able to effectively increase the extraction rate of dimethyl sulfoxide. Among them, dichloromethane had the best effect, with an extraction rate of more than 99%.

[0196] In Comparative Examples 1 and 2, benzene and cyclohexane were used as extractants, and the extraction rate of dimethyl sulfoxide was much lower than that of the example using dichloromethane, indicating that these two extractants are not suitable for the recovery of dimethyl sulfoxide.

[0197] Acid-base adjustment:

[0198] In Comparative Example 3, no acid-base adjustment was performed and the waste liquid was kept acidic, which resulted in a certain degree of thermal decomposition of DMSO during the distillation process and a significant decrease in the recovery rate.

[0199] Distillation separation:

[0200] In Examples 1-6, high-purity dimethyl sulfoxide can be effectively separated by using intermittent distillation and a packed tower.

[0201] In Comparative Example 5, a rotary evaporator was used for separation. Although high-purity dimethyl sulfoxide was obtained, the recovery rate was low, indicating that this method was not as efficient as intermittent distillation.

[0202] Deep dehydration:

[0203] In Examples 1-6, by using different dehydrating agents and operating conditions, the water content in dimethyl sulfoxide can be effectively reduced and the purity of the product can be improved.

[0204] In Comparative Example 4, no dehydrating agent was placed in the package, resulting in the product absorbing water after being stored for a long time, affecting its stability and reusability.

[0205] Product purity and recyclability:

[0206] The product purities in Examples 1-6 are generally high, and most of the products have good reusability, indicating that these methods can effectively recover and purify dimethyl sulfoxide.

[0207] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for extracting and recovering dimethyl sulfoxide, characterized in that: The following steps are involved: S1. Acid-base adjustment: measure the pH of the mixed waste liquid containing dimethyl sulfoxide. When the pH of the mixed waste liquid is lower than 7.0, add a regulator to increase the pH of the solution to 7.0 or above; S2, extraction: the mixed waste liquid after adjusting the pH is mixed with the extractant and fully contacted, so that the dimethyl sulfoxide and organic matter in the mixed waste liquid will be enriched in the extraction phase, and the water-soluble salt and water will be enriched in the raffinate phase; S3, distillation: further separating the extract phase by distillation to obtain a front fraction, a transition fraction, and a dimethyl sulfoxide fraction; S4, dehydration: continuously contacting the dimethyl sulfoxide fraction with the activated dehydrating agent, so that water in the dimethyl sulfoxide fraction is adsorbed on the dehydrating agent to obtain a recovered dimethyl sulfoxide product.

2. The method for extracting and recovering dimethyl sulfoxide according to claim 1, characterized in that: In S1, the mixed waste liquid includes dimethyl sulfoxide and impurities, and the impurities include organic matter, water-soluble salts and / or alkalis, and water; Part or all of the protium atoms in the molecular structure of the dimethyl sulfoxide are replaced by deuterium atoms, and the molecular formula of the dimethyl sulfoxide is C2H x D y OS, where H is a protium atom, D is a deuterium atom, x+y=6, 0≤x≤6, 0≤y≤6; The dimethyl sulfoxide component in the dimethyl sulfoxide mixed waste liquid satisfies 0.8≤y / (x+y)≤0.

999.

3. The method for extracting and recovering dimethyl sulfoxide according to claim 1, characterized in that: In S1, the mass content of dimethyl sulfoxide in the mixed waste liquid is 10% to 60%, the mass content of other organic matter is 0% to 20%, the mass content of water-soluble salt is 5% to 50%, and the mass content of water is 30% to 80%.

4. The method for extracting and recovering dimethyl sulfoxide according to claim 2, characterized in that: In S1, the organic matter is an organic matter other than dimethyl sulfoxide that can exist in a homogeneous form in the mixed waste liquid, and the organic matter is a single substance or a mixture.

5. The method for extracting and recovering dimethyl sulfoxide according to claim 1, characterized in that: In S1, the regulator is one of a salt and / or a base, or an aqueous solution of a salt and / or a base, wherein the cation portion of the salt and / or the base is selected from Na + , K + NH4 + , Ca + Mg 2+ One or more of the salts, the anion portion of the salt is selected from CO3 2- 、HCO3 - One or more of .

6. The method for extracting and recovering dimethyl sulfoxide according to claim 1, characterized in that: In S1, a regulator is added to control the pH of the solution between 7 and 9.

7. The method for extracting and recovering dimethyl sulfoxide according to claim 1, characterized in that: In S2, the selection of the extractant satisfies: 1) The boiling point at normal pressure is lower than that of dimethyl sulfoxide, 2) It is immiscible with water at the extraction operating temperature, 3) It can form the lowest azeotrope with water. 4) It has polarity, The normal pressure boiling point of the extractant is lower than 120° C., the solubility in water at room temperature is lower than that of being easily soluble, and the normal pressure azeotropic temperature of the lowest azeotrope formed with water is lower than 90° C.

8. The method for extracting and recovering dimethyl sulfoxide according to claim 1, characterized in that: In S2, the extraction operating temperature is 10-30°C, the operating pressure is 100-150 kPaA, and the mass ratio of the solution to be extracted to the extractant is 0.5:1-3:1; The extraction method is intermittent extraction or continuous extraction; When the intermittent extraction is adopted, the number of extractions is 1 to 3 times, and the extraction phases obtained in each time are combined as the final extraction phase; The extraction phase comprises dimethyl sulfoxide, organic matter and water, wherein the mass content of water is less than 5%.

9. The method for extracting and recovering dimethyl sulfoxide according to claim 1, characterized in that: In S3, the transition fraction contains the extractant, dimethyl sulfoxide, and components in organic matter having a boiling point lower than dimethyl sulfoxide; The mass content of dimethyl sulfoxide in the dimethyl sulfoxide fraction is more than 99%, the sum of the contents of other organic matter and extractant does not exceed 0.5%, and the mass content of water does not exceed 1%; The components in the organic matter with boiling points lower than dimethyl sulfoxide are removed in the front fraction or transition fraction; The oil phase obtained in the front fraction stage includes an extractant, and the oil phase is directly reused as an extractant or is reused after being refined and purified.

10. The method for extracting and recovering dimethyl sulfoxide according to claim 1, characterized in that: In S3, the pressure of the front fraction stage is normal pressure or reduced pressure; When using reduced pressure, the bottom temperature of the tower is lower than 130℃; The operating pressure of the front fraction stage is not less than 20 kPaA, the temperature of the tower top is not less than 0°C, and the reflux ratio is 1:1 to 5:1; The operating pressure of the transition fraction stage is 2-20 kPaA, the temperature of the tower top is 0-110°C, and the reflux ratio is 3:1-10:1; The operating pressure of the dimethyl sulfoxide fraction stage is 0.1-5 kPaA, the temperature of the tower top is 25-105°C, and the reflux ratio is 0.2:1-3:1.

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