A method of reducing the acid value of dimethyl sulfoxide

Abstract

The application discloses a method for reducing the acid value of dimethyl sulfoxide, and belongs to the technical field of dimethyl sulfoxide production, and comprises the following steps: loading an activated carbon loaded double-metal catalyst into a fixed bed, continuously passing crude dimethyl sulfoxide through the fixed bed after vaporization in a tower, and reacting nitrogen dioxide, nitric acid, nitrous acid and the like in the crude dimethyl sulfoxide with the activated carbon to become nitrogen, carbon dioxide and water, so as to obtain dimethyl sulfoxide without nitrogen dioxide and with qualified acid value after condensation; the method can be continuously and stably operated, the production process of dimethyl sulfoxide is simplified, and the operation is simple; the catalyst has high activity, a large gas treatment capacity and high deacidification efficiency; the method does not need to use lye neutralization, and there are no waste salts such as nitrate, so that the safety and environmental protection risks are reduced.

Description

Technical Field

[0001] This application belongs to the field of dimethyl sulfoxide production technology, and in particular relates to a method for reducing the acid value of dimethyl sulfoxide. Background Technology

[0002] Dimethyl sulfoxide (DMSO) is an important organic chemical raw material. It is colorless, odorless, and has low toxicity. It can dissolve various polar organic gases, liquids, and polymers except for alkanes, and has strong molecular association properties. It is an extremely important aprotic polar solvent and is commonly used as an organic solvent and reaction reagent. It is widely used in many chemical fields such as medicine, pesticides, petroleum, chemicals, organic synthesis, electronics, coatings, metallurgy, dyes, and polymer materials, and some new applications are constantly being discovered.

[0003] Industrially, dimethyl sulfoxide (DMSO) is typically synthesized using the nitrogen dioxide oxidation method. Using dimethyl sulfide as a raw material, oxygen and nitrogen dioxide are introduced to react and produce DMSO. During the oxidation of dimethyl sulfide to DMSO, a large amount of nitrogen dioxide dissolves in the DMSO. The traditional method for removing nitrogen dioxide and reducing acid value involves adding a certain concentration of alkali solution for neutralization, generating sodium nitrate, which is then separated by distillation. Distillation for sodium nitrate removal poses significant safety risks and generates large amounts of waste salt, increasing environmental pressure. The generated sodium nitrate easily clogs pipes, affecting normal production. Furthermore, the separation of DMSO from water after sodium nitrate removal is cumbersome, increasing energy consumption and costs.

[0004] CN115466203 discloses a method for removing nitrogen dioxide from crude dimethyl sulfoxide. The method involves adding a certain mass of dimethyl sulfide to the crude dimethyl sulfoxide and heating to 20-60°C. o C. Reaction with nitrogen dioxide to remove nitrogen dioxide. The disadvantages of this method are: it essentially adds an extra reaction step, and excess dimethyl sulfide needs to be separated, increasing equipment and costs, making the process cumbersome; the process does not completely remove nitrogen dioxide, resulting in products with unacceptable acid values, requiring further processing; dimethyl sulfide is flammable and explosive, increasing safety hazards; the tail gas produced after the reaction needs to be absorbed using a potassium permanganate-sodium hydroxide solution, increasing wastewater treatment and being detrimental to environmental protection; and excessive oxidation to dimethyl sulfone may occur during the reaction, increasing the content of byproducts.

[0005] CN115611784A discloses a method for continuous removal of nitrogen dioxide in a degassing tower. The method involves introducing crude dimethyl sulfoxide (DMSO) from the top of the tower, heating it to remove nitrogen dioxide from the top, and then discharging the remaining DMSO from the bottom of the tower. The main drawbacks of this method are that it relies solely on heating to separate DMSO and nitrogen dioxide, resulting in a nitrogen dioxide removal rate of only 80%, a high acid value, requiring further removal using other methods, and potentially causing decomposition of the DMSO; the degassing tower also has a complex structure and is inconvenient to maintain.

[0006] CN220277001U discloses an apparatus for the neutralization reaction of dimethyl sulfoxide (DMSO). This apparatus consists of two towers: one as a stripping tower to remove some nitrogen dioxide, and the other as a neutralization tower to further remove nitrogen dioxide and lower the acid value using liquid alkali. The method used in this apparatus still involves final neutralization to remove nitrogen dioxide and lower the acid value from DMSO, generating a large amount of nitrate waste liquid. Subsequent operations still require distillation to separate the DMSO, increasing safety hazards and environmental pressure. Both towers are plate towers, resulting in complex structures, inconvenient maintenance, increased floor space, and higher costs.

[0007] Based on the existing production technology and equipment for removing nitrogen dioxide and reducing acid value from dimethyl sulfoxide (DMSO), the following problems have been found: the nitrogen dioxide removal rate is low, the acid value is high, and further removal is required; the removal process increases safety hazards; DMSO is over-oxidized to dimethyl sulfone, increasing byproducts; the tail gas needs to be absorbed by alkaline solution, increasing the waste liquid treatment process; the process is cumbersome, the equipment structure is complex, and the production cost is increased. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the technical solution adopted in this application is: to provide a method for reducing the dimethyl sulfoxide value, specifically including the following steps:

[0009] A bimetallic catalyst supported on activated carbon is packed into a fixed bed. Crude dimethyl sulfoxide is vaporized in the tower and continuously passed through the fixed bed. Nitrogen dioxide, nitric acid, nitrous acid and other substances in the crude product react with the bimetallic catalyst supported on activated carbon to become nitrogen, carbon dioxide and water. After condensation, dimethyl sulfoxide without nitrogen dioxide and with qualified acid value is obtained.

[0010] The reaction equation is as follows:

[0011] NO2+ 2C N2+ 2CO2

[0012] 4HNO3+ 5C 2N2+ 5CO2+ 2H2O

[0013] 4HNO2+ 3C 2N2+ 3CO2+ 2H2O

[0014] The preparation method of activated carbon supported dual metal catalyst is as follows: metal component A and metal component B are mixed in proportion and dissolved in water, and then the active components are uniformly loaded onto activated carbon through a spraying device. After standing, drying and calcining, the catalyst is obtained.

[0015] Metal component A is one of manganese, chromium, cobalt or copper nitrates, and metal component B is one of potassium, sodium or cesium nitrates; preferably, metal component A is manganese nitrate and metal component B is potassium nitrate.

[0016] In one embodiment,

[0017] The loading of metal component A is 0.5-3 wt%, and the loading of metal component B is 1-6 wt%; preferably, the loading of metal component A is 0.8-2.5 wt%, and the loading of metal component B is 1.5-5.5 wt%.

[0018] In one embodiment,

[0019] The drying temperature for activated carbon-supported bimetallic catalysts is 100-150°C. o C, Firing temperature is 300-700 o C, the calcination time is 4 hours; preferably, the drying temperature is 110-130°C. o C, calcination temperature is 400-600 o C.

[0020] In one embodiment,

[0021] The crude dimethyl sulfoxide contains 80-99 wt% dimethyl sulfoxide and 0.5-10 wt% nitrogen dioxide, preferably 1-3 wt% nitrogen dioxide.

[0022] In one embodiment,

[0023] The temperature of crude dimethyl sulfoxide passing through the fixed bed is 110-140℃. o C, pressure of 5-25 kPa(A), preferably, temperature of 120-130°C o C, pressure is 10-20 kPa (A).

[0024] In one embodiment,

[0025] Crude dimethyl sulfoxide passed through a dual-metallic catalyst supported on activated carbon with a volume hourly space velocity of 10–500 h⁻¹. -1 .

[0026] In one embodiment,

[0027] The fixed bed includes a catalyst tube array, with at least one catalyst tube array. Multiple catalyst tube arrays are arranged in a square, with a height of 2500 mm and a diameter of 25 mm.

[0028] In one embodiment,

[0029] The specific surface area of ​​activated carbon is 1000-2500 m². 2 / g, preferably, with a specific surface area of ​​1500-2000 m² 2 / g. Iodine adsorption value greater than 800 mg / g, preferably greater than 900 mg / g; average particle size range of 8-30 mesh, preferably 15-25 mesh; ash content less than 5%, preferably less than 2%.

[0030] In one embodiment,

[0031] The preparation method of activated carbon-supported bimetallic catalyst is as follows: Metal component A is dissolved in water and then uniformly sprayed onto activated carbon. After standing, drying, and calcination, a single-metal-supported activated carbon is obtained. Then, metal component B is dissolved in water and uniformly sprayed onto the single-metal-supported activated carbon. After standing, drying, and calcination, the catalyst is obtained. The spraying equipment used includes, but is not limited to, roller coating machines, spray fluidized beds, and ultrasonic spraying.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The catalyst prepared by this invention has good catalytic activity. Activated carbon simultaneously loaded with both manganese and potassium catalysts exhibits high activity. After manganese is loaded onto the activated carbon, it provides more adsorption sites, enabling the activated carbon to simultaneously possess chemical adsorption capabilities and significantly enhancing its adsorption capacity. Manganese ions have good electron transfer capabilities, and there are a large number of lattice oxygen atoms between manganese oxides. The presence of lattice oxygen is an important condition for the catalytic reduction of nitrogen oxides. Furthermore, the reduction of nitrogen oxides requires electrons, and the rapid electron exchange between different manganese ion pairs at the active centers can more effectively promote electron transfer, thereby benefiting the catalyst's ability to catalyze the reduction of nitrogen oxides. As an oxidant, nitrogen oxides can oxidize the carbon atoms on the surface of activated carbon to generate carbon dioxide, water, etc. After potassium is loaded onto the activated carbon, its acidity and alkalinity can be adjusted through chemical modification, enhancing the adsorption and reduction of nitrogen oxides and promoting the reaction.

[0034] 2. This method can operate continuously and stably, with high catalyst activity, large gas throughput, and high acid removal efficiency. The nitrogen dioxide removal rate can reach over 99.9%, and the acid value can be reduced to below 0.01 mg / g (calculated as KOH). This method does not require the use of alkaline solution for neutralization, does not produce waste salts such as nitrates, generates less chemical waste, and is green and environmentally friendly.

[0035] 3. This method has high operational safety; it does not generate dimethyl sulfone or other impurities when passing through a fixed bed, and it does not cause the decomposition of dimethyl sulfoxide, thus reducing the loss of dimethyl sulfoxide;

[0036] 4. This method simplifies the production process of dimethyl sulfoxide, and the activated carbon loaded with active components can efficiently deacidify. The operating conditions are mild, which improves production efficiency and reduces costs. The operation is simple, highly automated, easy to control, and can be monitored in real time. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 Electron micrograph of a bimetallic catalyst supported on activated carbon;

[0039] Figure 2 This is a process flow diagram for the deacidification of crude dimethyl sulfoxide.

[0040] Explanation of symbols in the diagram:

[0041] 1. First temperature sensor; 2. Lower flange of tower level gauge; 3. Upper flange of tower level gauge; 4. Dimethyl sulfoxide crude product inlet; 5. Gas distributor; 6. Second temperature sensor; 7. Catalyst tubes; 8. Third temperature sensor; 9. Pressure sensor; 10. Dimethyl sulfoxide crude product outlet; 11. Condenser; 12. Dimethyl sulfoxide buffer tank; 13. Upper flange of buffer tank level gauge; 14. Lower flange of buffer tank level gauge; 15. Sampling port; 16. Dimethyl sulfoxide reflux; 17. Dimethyl sulfoxide storage tank; 18. Upper flange of finished product tank level gauge; 19. Lower flange of finished product tank level gauge. Detailed Implementation

[0042] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, this application will be further described in detail. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit this application.

[0043] Example 1

[0044] Weigh 100 g and the specific surface area is 2000 m². 2 / g, iodine adsorption value 1000 mg / g, average particle size range 20 mesh, activated carbon with 1% ash content at 120 o The activated carbon was dried at C until constant weight, and weighed to 95.50 g. 6.64 g of manganese nitrate and 18.59 g of potassium nitrate were weighed and dissolved in deionized water, stirred, and the solution temperature was maintained at 80 °C. The aqueous solution containing the active components manganese nitrate and potassium nitrate was evenly sprayed onto 95.50 g of dried activated carbon through an atomizing nozzle, allowing the activated carbon to fully adsorb the aqueous solution containing manganese nitrate and potassium nitrate. After complete adsorption, the activated carbon was transferred to a tray and allowed to stand under constant temperature and humidity conditions until no free moisture remained on the surface. Then, it was placed in a drying oven at 120 °C. o Dry at C for 3 h, then transfer to a muffle furnace and heat to 500 °C. o After calcination at C for 4 h, the catalyst was cooled to room temperature to obtain a manganese- and potassium-supported bimetallic catalyst on activated carbon. The manganese content was 1.95 wt% and the potassium content was 4.32 wt%. The electron micrograph of the activated carbon-supported bimetallic catalyst is shown below. Figure 1 As shown;

[0045] A 5 L activated carbon-supported bimetallic catalyst was prepared using the method described above. 4 L of the catalyst was measured and packed into four catalyst tubes using a bag filter method, with 1 L packed into each tube. Crude dimethyl sulfoxide containing 5 wt% nitrogen dioxide was pumped into the column reboiler, maintaining the liquid level at 200-250 mm. The electric heater and vacuum pump were then turned on, and the pressure inside the column was controlled at 15 kPa(A). The temperature of the entire column was raised to 130°C. o C, the crude dimethyl sulfoxide is passed through the fixed bed in the form of steam, and the volume hourly space velocity (VHS) of the crude dimethyl sulfoxide through the activated carbon-supported dual-metal catalyst is adjusted to 296 h⁻¹. -1 After the material begins to be discharged from the top of the column, the feed pump is turned on at a flow rate of 3.2 kg / h, and the liquid level in the column bottom is controlled at 200-250 mm. The material discharged from the top of the column is condensed and enters the buffer tank as liquid. When the liquid level in the buffer tank reaches 200 mm, part of it can be refluxed back into the column bottom to adjust the liquid level in the column bottom, and the other part goes directly into the dimethyl sulfoxide storage tank. After passing through the fixed bed, the dimethyl sulfoxide content is tested to be 99.9% and the acid value is 0.020 mg / g (calculated as KOH).

[0046] Example 2

[0047] The difference between this embodiment and Example 1 is that metal component A is chromium nitrate and metal component B is sodium nitrate; the remaining operations are the same, resulting in an activated carbon-supported dual-metal catalyst. After fixing the bed, the dimethyl sulfoxide content was found to be 99.93%, and the acid value was 0.015 mg / g (based on KOH).

[0048] Example 3

[0049] The difference between this embodiment and Example 1 is that metal component A is cobalt nitrate and metal component B is cesium nitrate; the rest of the operations are the same, resulting in an activated carbon-supported dual-metal catalyst. After fixing the bed, the dimethyl sulfoxide content was found to be 99.91%, and the acid value was 0.020 mg / g (based on KOH).

[0050] Example 4

[0051] The difference between this embodiment and Example 1 is that metal component A is copper nitrate and metal component B is potassium nitrate; the remaining operations are the same, resulting in an activated carbon-supported dual-metal catalyst. After fixing the bed, the dimethyl sulfoxide content was found to be 99.92%, and the acid value was 0.023 mg / g (calculated as KOH).

[0052] Example 5

[0053] The difference between this embodiment and Example 1 is that 1.7 g of manganese nitrate and 4.3 g of potassium nitrate were weighed to prepare an activated carbon-supported bimetallic catalyst with a manganese content of 0.5 wt% and a potassium content of 1 wt%. After fixing the bed, the dimethyl sulfoxide content was found to be 99.9%, and the acid value was 0.026 mg / g (calculated as KOH).

[0054] Example 6

[0055] The difference between this embodiment and Example 1 is that 10.2 g of manganese nitrate and 25.8 g of potassium nitrate were weighed to prepare an activated carbon-supported bimetallic catalyst with a manganese content of 3 wt% and a potassium content of 6 wt%. After fixing the bed, the dimethyl sulfoxide content was found to be 99.94%, and the acid value was 0.008 mg / g (calculated as KOH).

[0056] Example 7

[0057] The difference between this embodiment and Example 1 is that the drying temperature of the activated carbon-supported dual-metal catalyst is 100°C. o C, calcination temperature is 300 o C. The remaining operations are the same, and the activated carbon-supported bimetallic catalyst is obtained.

[0058] Example 8

[0059] The difference between this embodiment and Example 1 is that the drying temperature of the activated carbon-supported bimetallic catalyst is 150°C. o C, calcination temperature is 700 o C. The remaining operations are the same, and the activated carbon-supported bimetallic catalyst is obtained.

[0060] Example 9

[0061] The difference between this embodiment and Example 1 is that the nitrogen dioxide content is 10 wt%, while the other operations are the same, to prepare an activated carbon-supported dual-metal catalyst. After fixing the bed, the dimethyl sulfoxide content was found to be 99.9%, and the acid value was 0.027 mg / g (calculated as KOH).

[0062] Example 10

[0063] The difference between this embodiment and Embodiment 1 is that the pressure inside the control tower is 5 kPa (A), and the temperature of the entire tower is raised to 110°C. o C. The remaining operations are the same, and the activated carbon-supported bimetallic catalyst is obtained.

[0064] Example 11

[0065] The difference between this embodiment and Embodiment 1 is that the pressure inside the control tower is 25 kPa(A), and the temperature of the entire tower is raised to 140°C. o C. The remaining operations are the same, and the activated carbon-supported bimetallic catalyst is obtained.

[0066] Example 12

[0067] The difference between this embodiment and Example 1 is that the preparation method of the activated carbon-supported dual-metal catalyst is as follows: weigh 100 g of a catalyst with a specific surface area of ​​2000 m². 2 / g of activated carbon at 120 o The activated carbon was dried at C until constant weight, and weighed to 95.50 g. 6.64 g of manganese nitrate was weighed and added to deionized water, stirred to dissolve, and the solution temperature was maintained at 80°C. The aqueous solution containing the active component was evenly sprayed onto the dried activated carbon through a misting nozzle, allowing the activated carbon to fully adsorb the manganese nitrate-containing aqueous solution. After complete adsorption, the activated carbon was transferred to a tray and allowed to stand under constant temperature and humidity until no free moisture remained on the surface. Then, it was placed in a drying oven at 120°C. o Dry at C for 3 h, then transfer to a muffle furnace and heat to 500 °C. o Calcination at C for 4 h yielded single-metal-supported activated carbon. Then, 18.59 g of potassium nitrate was added to deionized water and stirred until dissolved, maintaining the solution temperature at 80°C. The potassium nitrate solution was then uniformly sprayed onto the once-impregnated activated carbon through an atomizing nozzle, allowing the activated carbon to fully adsorb the potassium nitrate-containing aqueous solution. After complete adsorption, the activated carbon was transferred to a tray and allowed to stand under constant temperature and humidity until no free moisture remained on the surface. Finally, it was placed in a drying oven at 120°C.o Dry at C for 3 h, then transfer to a muffle furnace and heat to 500 °C. o After calcination at C for 4 h, the catalyst was cooled to room temperature to obtain a bimetallic catalyst supported on activated carbon containing manganese and potassium. The manganese content was 2.06 wt% and the potassium content was 5.83 wt%. The remaining operations were the same. After fixing the bed, the dimethyl sulfoxide content was found to be 99.95% and the acid value was 0.006 mg / g (calculated as KOH).

[0068] Example 13

[0069] like Figure 2 As shown, crude dimethyl sulfoxide (DMSO) enters the fixed bed through the DMSO crude product inlet 4. The fixed bed consists of four catalyst tubes 7 arranged in a square. The catalyst tubes 7 are 2500 mm high and 25 mm in diameter. After a certain volume of catalyst is measured, it is filled into the catalyst tubes 7 using a bag-filling method. After filling, the height is measured to ensure that the catalyst height in the four catalyst tubes 7 is consistent. The DMSO crude product passing through the catalyst tubes 7 is discharged from the DMSO crude product outlet 10 into the DMSO buffer tank 12, and the finished product enters the DMSO storage tank 17 for storage.

[0070] This application provides a method for reducing the acid value of dimethyl sulfoxide (DMSO), comprising the following steps: A dual-metal catalyst supported on activated carbon is loaded into a fixed bed; crude DMSO is vaporized in a tower and continuously passed through the fixed bed; nitrogen dioxide, nitric acid, nitrite, etc., in the crude product react with activated carbon to form nitrogen, carbon dioxide, and water; after condensation, DMSO without nitrogen dioxide and with a qualified acid value is obtained; the activated carbon-supported dual-metal catalyst is prepared by mixing metal component A and metal component B in a certain proportion and dissolving them in water, then uniformly spraying the mixture onto activated carbon, allowing it to stand, dry, and calcining; metal component A is a nitrate of manganese, chromium, cobalt, or copper, and metal component B is a nitrate of potassium, sodium, or cesium; this method can operate continuously and stably, simplifying the production process of DMSO and making it easy to operate; the catalyst has high activity, a large gas throughput, and high deacidification efficiency; this method does not require the use of alkali for neutralization and does not produce waste salts such as nitrates, reducing safety and environmental risks.

[0071] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0072] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for reducing the dimethyl sulfoxide value, characterized in that, Specifically, the following steps are included: The activated carbon-supported bimetallic catalyst is packed into a fixed bed. The crude dimethyl sulfoxide is vaporized in the tower and then continuously passed through the fixed bed. The nitrogen dioxide, nitric acid, and nitrous acid in the crude product react with the activated carbon-supported bimetallic catalyst to become nitrogen, carbon dioxide, and water. After condensation, dimethyl sulfoxide without nitrogen dioxide and with qualified acid value is obtained. The preparation method of the activated carbon supported dual metal catalyst is as follows: metal component A and metal component B are mixed in proportion and dissolved in water, then uniformly sprayed onto activated carbon, and then allowed to stand, dry and calcined to obtain the catalyst. The preparation method of the activated carbon-supported dual metal catalyst may be as follows: after dissolving metal component A in water, it is uniformly sprayed onto activated carbon, and after standing, drying and calcining, a single metal-supported activated carbon is obtained; then, after dissolving metal component B in water, it is uniformly sprayed onto the single metal-supported activated carbon, and after standing, drying and calcining, the catalyst is obtained. The drying temperature of the activated carbon-supported bimetallic catalyst is 100-150°C. o C, Firing temperature is 300-700 o C, the roasting time is 4 hours; Metal component A is one of manganese, chromium, cobalt, or copper nitrates, and metal component B is one of potassium, sodium, or cesium nitrates; the loading of metal component A is 0.5-3 wt%, and the loading of metal component B is 1.5-6 wt%. The crude dimethyl sulfoxide (DMSO) product contains 80-99 wt% DMSO and 1-10 wt% nitrogen dioxide. The temperature of crude dimethyl sulfoxide passing through the fixed bed is 110-140℃. o C, pressure is 5-25 kPa (A).

2. The method for reducing the dimethyl sulfoxide value according to claim 1, characterized in that, The crude dimethyl sulfoxide was passed through a dual-metallic catalyst supported on activated carbon with a volume hourly space velocity of 10-500 h⁻¹. -1 .

3. The method for reducing the dimethyl sulfoxide value according to claim 1, characterized in that, The fixed bed includes a catalyst tube array, the number of which is at least one, and multiple catalyst tube arrays are arranged in a square.

4. The method for reducing the dimethyl sulfoxide value according to claim 1, characterized in that, The specific surface area of ​​the activated carbon is 1000-2500 m². 2 / g.

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