Recovery processing method of dimethyl sulfone evaporation mother liquor

Abstract

The invention belongs to the technical field of chemical engineering, and particularly discloses a dimethyl sulfone evaporation mother liquor recovery treatment method which is characterized by comprising the following steps: firstly, adding citric acid into dimethyl sulfone evaporation mother liquor to carry out acid-base neutralization reaction, adjusting the pH value of the mother liquor to weak acidity, then stirring the mother liquor at normal temperature under the action of magnetic stirring, controlling the stirring rate to be 200-400rpm, and carrying out reaction for 2-3 hours; and slowly adding an oxidizing agent in an amount which is 20 to 30 percent of the mass of the mother liquor under the action of mechanical stirring, reacting for 0.5 to 2 hours, cooling to below 5 DEG C, and separating out dimethyl sulfone crystals. By adopting the method, the conversion rate of dimethyl sulfoxide (DMSO) in the mother liquor can reach 98% or above. According to the method, valuable components in the mother liquor can be effectively recycled, waste is turned into wealth, reduction and recycling of waste salt and waste water are achieved, meanwhile, pollution to the environment is reduced, the resource utilization rate is increased, green and low-carbon development is promoted, and good social benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for recovering and treating dimethyl sulfone waste salt evaporation mother liquor, which is mainly used in the fields of chemical industry, environmental protection and biomedicine. Background Art

[0002] Dimethyl sulfone waste salt refers to the byproduct produced during the production of dimethyl sulfoxide (DMSO) by oxidation using dimethyl sulfide as a raw material and nitrogen dioxide as a catalyst (hereinafter referred to as MSM waste salt). Its main components include DMSO, DMSO, sodium nitrate, sodium nitrite, sodium methanesulfonate, and insoluble impurities. If DMSO waste salt is stored outdoors for a long time, it absorbs moisture or is washed away by rainwater, contaminating groundwater and causing serious damage to the surrounding natural ecosystem. Discharge without treatment can also have a serious impact on the environment. The typical treatment for DMSO waste salt is rigid landfill disposal. However, the dimethyl sulfone and sodium nitrate in DMSO waste salt are of high economic value. While rigid landfill disposal solves the environmental pollution problem of DMSO waste salt, it also represents a certain degree of waste of valuable resources. Therefore, considering the resource utilization of DMSO waste salt, thereby achieving the goal of recycling MSM and sodium nitrate, this approach can also save rigid landfill space and reduce economic costs.

[0003] Methods for recovering and separating valuable components from waste salts can be broadly divided into vacuum distillation, extraction, and cooling crystallization followed by evaporation and concentration. Vacuum distillation is energy-intensive and hazardous, while extraction is costly and unsafe. The most commonly used method, cooling crystallization followed by evaporation and concentration, offers a simple system, ease of operation, and high safety, providing constructive guidance for the resource recovery of DMSO waste salts. The cooling crystallization followed by evaporation and concentration of MSM waste salts produces a large amount of DMSO evaporation mother liquor. As the evaporation, crystallization, and centrifugation steps continue, the mother liquor becomes enriched with significant amounts of DMSO (the DMSO content in the DMSO evaporation mother liquor ranges from approximately 4.79% to 12.04%). DMSO has a low melting point and is liquid at room temperature. As the DMSO content increases, the viscosity of the DMSO evaporation mother liquor increases, making subsequent evaporation and concentration and filter press centrifugation difficult, significantly impacting production efficiency and generating significant amounts of industrial wastewater.

[0004] In response to the aforementioned shortcomings of the existing technologies, there is an urgent need to develop a new method or improve existing methods for converting dimethyl sulfoxide into dimethyl sulfone. The present invention develops a method for converting dimethyl sulfoxide from dimethyl sulfone evaporation mother liquor into dimethyl sulfone. This method not only improves the recovery rate of dimethyl sulfone and increases economic benefits, but also significantly reduces and recycles waste salt, promoting the development of enterprises in a green and low-carbon direction. This method ultimately achieves the effective and comprehensive utilization of dimethyl sulfone waste salt. Summary of the Invention

[0005] The present invention aims to develop a process for oxidizing dimethyl sulfoxide in dimethyl sulfone evaporation mother liquor to produce dimethyl sulfone. The process uses sodium tungstate as a catalyst, hydrogen peroxide as an oxidant, and an organic silicon defoamer as an evaporation defoamer. The process can effectively oxidize dimethyl sulfoxide to dimethyl sulfone and has the advantages of fast reaction rate, low reaction temperature, and the like.

[0006] The above object is achieved through the following technical solution: a method for recovering and treating dimethyl sulfone evaporation mother liquor, comprising the following steps:

[0007] Mother liquor pretreatment: Dimethyl sulfone evaporated mother liquor is placed in a reaction device, acidity regulator is added at room temperature, and completely dissolved under magnetic stirring, wherein the acidity regulator is citric acid; (2) oxidation reaction: oxidant, defoamer and catalyst are added to the reaction device at room temperature, the dripping speed of the oxidant is controlled, and dimethyl sulfoxide in the mother liquor is gradually oxidized to dimethyl sulfone under magnetic stirring to obtain mother liquor 1; (3) cooling crystallization: the mother liquor 1 in step (2) is placed in a low temperature environment for crystallization treatment to precipitate dimethyl sulfone crystals; (4) solid-liquid separation: the liquid in the solid-liquid mixture in step (3) is separated from the dimethyl sulfone crystals to obtain the dimethyl sulfone product. The present invention greatly accelerates the reaction speed of the oxidation reaction by using sodium tungstate as a catalyst for the oxidation of dimethyl sulfoxide to dimethyl sulfone. At room temperature, the reaction only takes 1 hour to achieve a dimethyl sulfoxide conversion rate of about 98%. The sodium tungstate used in the present invention as a catalyst can effectively reduce the production energy consumption of dimethyl sulfone, shorten the production cycle, improve the production efficiency, and enhance the economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a process flow chart of the present invention. Specific implementation methods

[0009] The present invention will be further described below with reference to specific examples to facilitate a better understanding of the present invention, but the protection scope of the present invention is not limited to these examples.

[0010] Example 1

[0011] The specific steps of the oxidation process for producing dimethyl sulfone by oxidation of dimethyl sulfone evaporated mother liquor are as follows:

[0012] (1) Weigh 100 mL of dimethyl sulfone evaporation mother liquor and place it in a 500 mL three-necked flask. Add 1.00 g of citric acid under magnetic stirring to adjust the pH value of the mother liquor. After complete dissolution, the pH value drops from 9.48 to 6.3. Measure 34 mL of 30% hydrogen peroxide and slowly add it dropwise to the mother liquor. As the amount of hydrogen peroxide added increases, the mother liquor temperature rises. When the temperature rises to 40°C, bubbles appear in the mother liquor. Add 7 mL of evaporation defoamer with a mass fraction of 5%. The bubbles disappear under magnetic stirring. Continue to add hydrogen peroxide. The mother liquor temperature continues to rise. When the hydrogen peroxide is completely added, the mother liquor temperature reaches a maximum of 97°C. Then continue to stir the mother liquor and the temperature gradually decreases. When the temperature drops to 77°C, add 0.1041 g of sodium tungstate. There is no boiling phenomenon and the temperature does not rise. Continue the reaction at 60°C-70°C for 2 h to obtain mother liquor 1 in which dimethyl sulfoxide is oxidized to dimethyl sulfone.

[0013] (2) Crystallization reaction: The mother liquor 1 in step (1) was placed in a 250 mL beaker and placed in a low temperature environment of 5°C for cooling crystallization, and dimethyl sulfone crystals were precipitated by cooling;

[0014] (3) solid-liquid separation: separating the liquid in the solid-liquid mixture in step (2) from the dimethyl sulfone crystals by suction filtration to obtain dimethyl sulfone crystals;

[0015] (4) The dimethyl sulfone crystals in step (3) were detected by gas chromatography. The GC purity of the dimethyl sulfone crystals was 98.87%, and the conversion rate of dimethyl sulfoxide was 98.2%.

[0016] Example 2

[0017] The specific steps of the oxidation process are as follows:

[0018] (1) Weigh 100 mL of dimethyl sulfone evaporation mother liquor and place it in a 500 mL three-necked flask. Add 1.00 g of citric acid under magnetic stirring to adjust the pH value of the mother liquor. After complete dissolution, the pH value drops from 9.51 to 6.19. Measure 34 mL of 30% hydrogen peroxide and slowly add it dropwise to the mother liquor. As the amount of hydrogen peroxide added increases, the mother liquor temperature rises. When the temperature rises to 40°C, bubbles appear in the mother liquor. Add 7 mL of 5% evaporation defoamer. The bubbles disappear under magnetic stirring. Continue to add hydrogen peroxide. The mother liquor temperature continues to rise. When the hydrogen peroxide is completely added, the mother liquor temperature reaches a maximum of 96°C. Then the mother liquor temperature gradually decreases. When the temperature drops to 80°C, add 0.2002 g of sodium tungstate. There is no boiling phenomenon, and the temperature gradually rises to a maximum of 94°C. Continue the reaction at 70°C-80°C for 1 hour to obtain mother liquor 2 in which dimethyl sulfoxide is oxidized to dimethyl sulfone.

[0019] (2) Crystallization reaction: The mother liquor 2 in step (1) was placed in a 250 mL beaker and placed in a low temperature environment of 5°C for cooling crystallization treatment to precipitate dimethyl sulfone crystals;

[0020] (3) solid-liquid separation: separating the liquid in the solid-liquid mixture in step (2) from the dimethyl sulfone crystals by suction filtration to obtain dimethyl sulfone crystals;

[0021] (4) The dimethyl sulfone crystals in step (3) were detected by gas chromatography. The GC purity of the dimethyl sulfone crystals was 98.95%, and the conversion rate of dimethyl sulfoxide was 97.94%.

[0022] Example 3

[0023] The specific steps of the oxidation process are as follows:

[0024] (1) Weigh 100 mL of dimethyl sulfone evaporation mother liquor and place it in a 500 mL three-necked flask. Add 1.02 g of citric acid under magnetic stirring to adjust the pH value of the mother liquor. After complete dissolution, the pH value drops from 9.48 to 6.05. Measure 34 mL of 30% hydrogen peroxide and slowly add it dropwise to the mother liquor. As the amount of hydrogen peroxide added increases, the temperature of the mother liquor rises. When the temperature rises to 48°C, bubbles appear in the mother liquor. Add 7 mL of 5% evaporation defoaming agent. The bubbles disappear under magnetic stirring. Continue to add hydrogen peroxide. The temperature of the mother liquor continues to rise. When the hydrogen peroxide is completely added, the mother liquor temperature reaches 97°C at its highest. Then the mother liquor temperature gradually decreases. When the temperature drops below 80°C, set the temperature of the magnetic stirrer to 75°C. The mother liquor is reacted at 70-80°C for 1.5 h to obtain mother liquor 3.

[0025] (2) Crystallization reaction: The mother solution 3 in step (1) was placed in a 250 mL beaker and placed in a low temperature environment of 5°C and allowed to stand overnight for cooling crystallization treatment;

[0026] (3) Observation of mother liquor 3 revealed no dimethyl sulfone crystal precipitation;

[0027] (4) A small amount of the mother liquor 3 in step (3) was diluted and fixed to a 250 mL volumetric flask. After further pretreatment, gas chromatography detection showed that the conversion rate of dimethyl sulfoxide was only 11.41%.

[0028] Example 4

[0029] The specific steps of the oxidation process are as follows:

[0030] (1) Weigh 100 mL of dimethyl sulfone evaporation mother liquor and place it in a 500 mL three-necked flask. Under magnetic stirring, add 1.1 g of citric acid to adjust the pH value of the mother liquor to acidic. Measure 34 mL of 30% hydrogen peroxide and slowly add it dropwise to the mother liquor. As the amount of hydrogen peroxide added increases, the temperature of the mother liquor rises. When the temperature rises to 40°C, bubbles are generated in the mother liquor. Add 10 mL of evaporation defoamer with a mass fraction of 5%. Under magnetic stirring, the bubbles disappear. Continue to add hydrogen peroxide, and the temperature of the mother liquor continues to rise. When the hydrogen peroxide is completely added, the mother liquor temperature reaches 96°C at its highest. Then slowly add 0.25 g of sodium tungstate. A small amount of bubbles are generated, and the temperature rises from 60°C to 70°C. Set the temperature of the magnetic stirrer to 70°C. The mother liquor is oxidized at this temperature for 1 hour. Then stop heating and continue stirring the mother liquor to room temperature to obtain mother liquor 4.

[0031] (2) Crystallization reaction: The mother liquor 4 in step (1) was placed in a 250 mL beaker and placed in a low temperature environment of 5°C for cooling crystallization treatment to precipitate dimethyl sulfone crystals;

[0032] (3) solid-liquid separation: separating the liquid in the solid-liquid mixture in step (2) from the dimethyl sulfone crystals by suction filtration to obtain dimethyl sulfone crystals;

[0033] (4) The dimethyl sulfone crystals in step (3) were detected by gas chromatography. The GC purity of the dimethyl sulfone crystals was 98.95%, and the conversion rate of dimethyl sulfoxide was 95.09%.

[0034] Example 5

[0035] The specific oxidation process steps are as follows:

[0036] (1) Weigh 100 mL of dimethyl sulfone evaporation mother liquor and place it in a 500 mL three-necked flask. Under magnetic stirring, add 1.02 g of citric acid to adjust the pH value of the mother liquor to acidic. Measure 34 mL of 30% hydrogen peroxide and slowly add it dropwise to the mother liquor. As the amount of hydrogen peroxide added increases, the temperature of the mother liquor rises. When the temperature rises to 46°C, bubbles appear in the mother liquor. Add 8 mL of evaporation defoamer with a mass fraction of 5%. Under magnetic stirring, the bubbles disappear. Continue to add hydrogen peroxide, and the temperature of the mother liquor continues to rise. When the hydrogen peroxide is completely added, the mother liquor temperature reaches a maximum of 94°C. Then slowly add 0.5 g of sodium tungstate. After the addition of sodium tungstate, the mother liquor temperature reaches a maximum of 92°C. There is no need to heat the magnetic stirrer. Continue to stir the mother liquor at room temperature until the mother liquor temperature drops to room temperature and then stop stirring to obtain mother liquor 5.

[0037] (2) Crystallization reaction: The mother liquor 5 in step (1) was placed in a 250 mL beaker and placed in a low temperature environment of 5°C for cooling crystallization to precipitate dimethyl sulfone crystals;

[0038] (3) solid-liquid separation: separating the liquid in the solid-liquid mixture in step (2) from the dimethyl sulfone crystals by suction filtration to obtain dimethyl sulfone crystals;

[0039] (4) The dimethyl sulfone crystals in step (3) were detected by gas chromatography. The GC purity of the dimethyl sulfone crystals was 99.17%, and the conversion rate of dimethyl sulfoxide was 98.37%.

Claims

1. A method for recovering and treating dimethyl sulfone evaporation mother liquor, comprising an oxidation reaction process, characterized in that: The oxidation reaction is as follows: using dimethyl sulfone evaporated mother liquor as a reactant, oxidizing dimethyl sulfoxide in the evaporated mother liquor to generate dimethyl sulfone under the action of an oxidant and a catalyst, wherein the oxidant is hydrogen peroxide, the catalyst is sodium tungstate, and the defoaming agent is an organosilicon defoaming agent.

2. The method for recycling dimethyl sulfoxide waste salt according to claim 1, wherein The oxidant is hydrogen peroxide or nitric acid.

3. The method for recycling dimethyl sulfoxide waste salt according to claim 2, wherein: The concentration of the hydrogen peroxide is 10%-50%.

4. The method for recovering dimethyl sulfone evaporation mother liquor according to claim 3, wherein: The effective component ratio of the dimethyl sulfone evaporation mother liquor to the hydrogen peroxide is 1:1-1.

6.

5. The method for recovering dimethyl sulfone waste salt evaporation mother liquor according to any one of claim 4, characterized in that: The reaction temperature of the oxidation reaction is 25° C.-100° C., and the reaction time is 30 min-120 min.

6. The method for recovering dimethyl sulfone waste salt evaporation mother liquor according to claim 5, characterized in that: The recovery process of its dimethyl sulfone product includes cooling crystallization, filtration, detection and other steps.

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