Preparation method of tetramethylthiuram monosulfide

Abstract

The present invention relates to the technical field of rubber vulcanization accelerator preparation, and in particular to a method for preparing tetramethylthiuram monosulfide. The method for preparing tetramethylthiuram monosulfide of the present invention comprises the following steps: (A) a mixed solution containing sodium cyanide, NaOH and dimethylamine is subjected to a condensation reaction with carbon disulfide in a microchannel reactor, and then aged and cooled to obtain a condensation reaction liquid; (B) a mixed solution of hydrogen peroxide and sulfuric acid solution is added to the condensation reaction liquid until the pH of the system is 6.5 to 7, and the tetramethylthiuram monosulfide is obtained after an oxidation reaction. The preparation method of the present invention has a high reaction conversion rate, and tetramethylthiuram monosulfide can be obtained with high purity and high yield; the entire reaction process can realize continuous production, greatly improving production efficiency; and the method has a small amount of wastewater discharge.

Description

Technical Field

[0001] The invention relates to the technical field of rubber vulcanization accelerator preparation, in particular to a method for preparing tetramethylthiuram monosulfide. Background Art

[0002] Tetramethylthiuram monosulfide (TMTM) is a super-fast vulcanization accelerator. It is a light yellow powder or granule. It is soluble in benzene, toluene, acetone, ethylene dichloride, chloroform and carbon disulfide, slightly soluble in ethanol and ether, insoluble in gasoline and water, odorless, tasteless, non-toxic and stable in storage. TMTM is suitable for the vulcanization process of natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene rubber, nitrile rubber, butyl rubber and terpolymer rubber.

[0003] There are two routes for synthesizing TMTM. One is to use dimethylamine, carbon disulfide, and chlorine as raw materials, and produce the intermediate product tetramethylthiuram disulfide (TMTD) through condensation and oxidation reaction in aqueous solution, and then react with sodium cyanide to desulfurize and produce TMTM. This process introduces highly toxic chlorine, has high safety risks, high requirements for equipment, and the product has a low melting point, dark appearance, and low yield.

[0004] Another preparation process is to use dimethylamine, carbon disulfide, hydrogen peroxide, and sodium cyanide as raw materials to prepare TMTM through condensation reaction and oxidation reaction. This process is a common process for preparing TMTM, but it has the following problems: the yield of TMTM is low, about 87%; the reaction is not thorough, the COD of the wastewater is high, about 30,000 mg / L, which brings great challenges to sewage treatment; the wastewater is directly treated with sewage without application, and the water consumption is large; the condensation reaction and oxidation reaction are intermittent reactions, the reaction time is long, and there are batch differences in the products.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing tetramethylthiuram monosulfide. The method has high reaction conversion rate and can obtain tetramethylthiuram monosulfide with high purity and high yield; the entire reaction process can realize continuous production, which greatly improves production efficiency; the method requires a short time; and the wastewater discharge amount and the COD of the wastewater are reduced.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] The present invention provides a method for preparing tetramethylthiuram monosulfide, comprising the following steps:

[0009] (A) a mixed solution containing sodium cyanide, NaOH and dimethylamine is subjected to a condensation reaction with carbon disulfide in a microchannel reactor, and then aged and cooled to obtain a condensation reaction liquid;

[0010] (B) adding a mixture of hydrogen peroxide and sulfuric acid solution into the condensation reaction solution until the pH of the system is 6.5-7, and obtaining the tetramethylthiuram monosulfide after oxidation reaction.

[0011] Furthermore, in step (A), sodium cyanide solution, NaOH solution and water are mixed in the first microchannel reactor and then enter the second microchannel reactor, where they are mixed with dimethylamine solution in the second microchannel reactor. After cooling, they enter the third microchannel reactor and undergo condensation reaction with carbon disulfide in the third microchannel reactor.

[0012] Furthermore, in step (A), the molar ratio of the sodium cyanide, the NaOH and the dimethylamine is (0.5-0.6):(0.5-0.6):1.

[0013] Furthermore, in step (A), the mass ratio of the water to the dimethylamine is (1.5-2):1.

[0014] Preferably, the concentration of the sodium cyanide solution is 25wt% to 35wt%, the concentration of the NaOH solution is 30wt% to 40wt%, and the concentration of the dimethylamine solution is 30wt% to 45wt%.

[0015] Furthermore, in step (A), the molar ratio of the dimethylamine to the carbon disulfide is 1:(1.03-1.07).

[0016] Furthermore, in step (A), the temperature of the condensation reaction is 15 to 20° C., and the time of the condensation reaction is 5 to 100 seconds.

[0017] Furthermore, in step (A), the aging time is 10 to 60 minutes.

[0018] Furthermore, in step (B), the molar ratio of the dimethylamine to the H2O2 in the mixed solution is 1:0.5-0.6.

[0019] Furthermore, in step (B), the molar ratio of the dimethylamine to the H2SO4 in the mixed solution is 1:0.3-0.4.

[0020] Furthermore, in step (B), the temperature of the oxidation reaction is 15 to 25° C., and the time of the oxidation reaction is 3.5 to 4.5 hours.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The preparation method of tetramethylthiuram monosulfide of the present invention adds sodium cyanide and NaOH in the condensation reaction stage and adopts a microchannel reactor to carry out the reaction, so that the condensation reaction is more thorough; sulfuric acid is added in the oxidation reaction stage, so that the oxidation reaction is more thorough and the reaction conversion rate is higher; thereby the yield of the product is ≥97%. The tetramethylthiuram monosulfide prepared by the preparation method of the present invention has a melting point of 108° C. and a product purity of ≥99%.

[0023] In the preparation method of the present invention, water is used as a solvent, and mother liquor water is recovered when the product is centrifuged. 60% of the mother liquor water can be recycled, thereby reducing wastewater discharge; and the COD of the wastewater is reduced to about 8000 mg / L, greatly reducing the pressure on sewage treatment.

[0024] The present invention realizes continuous production through condensation reaction by using a microchannel reactor, and subsequent aging and oxidation reactions can be automatically switched through multiple reactors to realize the continuity of the entire reaction process, thereby greatly improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 The present invention is a schematic diagram of a device for implementing the method for preparing tetramethylthiuram monosulfide.

[0027] 1-first microchannel reactor; 2-second microchannel reactor; 3-first heat exchanger; 4-third microchannel reactor; 5-aging tank; 6-second heat exchanger; 7-condensation liquid storage tank; 8-oxidation tank. DETAILED DESCRIPTION

[0028] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0029] The preparation method of tetramethylthiuram monosulfide according to the embodiment of the present invention is specifically described below.

[0030] In some embodiments of the present invention, a method for preparing tetramethylthiuram monosulfide is provided, comprising the following steps:

[0031] (A) a mixed solution containing sodium cyanide, NaOH and dimethylamine is subjected to a condensation reaction with carbon disulfide in a microchannel reactor, and then aged and cooled to obtain a condensation reaction liquid;

[0032] (B) adding a mixture of hydrogen peroxide and sulfuric acid solution to the condensation reaction solution until the pH of the system is 6.5-7, and obtaining tetramethylthiuram monosulfide after oxidation reaction.

[0033] The condensation reaction of the present invention is carried out in a microchannel reactor, and the liquid-liquid dispersion effect is good, the reactants are in contact on a microscale, the reaction conversion efficiency is high, and the continuous operation of the condensation reaction can also be achieved, and the reaction time is shortened to a second-level reaction. By adding NaOH and sodium cyanide during the condensation reaction, NaOH is a strong base, and sodium cyanide is a strong base weak acid salt, dimethyl dithiocarbamic acid is converted into sodium dimethyl dithiocarbamate, the condensation reaction conversion rate is further improved, the condensation liquid is clear and transparent, and is basically in a homogeneous phase. The condensation liquid is stable and easy to store, which lays a foundation for the continuous operation of the subsequent process. Due to the improvement of the condensation reaction conversion rate, there is no need to add excess carbon disulfide, the carbon disulfide feed ratio is greatly reduced, less carbon disulfide enters the oxidation reaction, and the oxidation reaction safety risk is also greatly reduced.

[0034] In the oxidation reaction of the present invention, a mixture of a hydrogen peroxide solution and a sulfuric acid solution is added dropwise to a condensation reaction solution. The purpose of adding sulfuric acid dropwise in the early stage is to neutralize excess hydroxide ions in the reaction system, and the purpose of adding sulfuric acid dropwise in the later stage is to inhibit the hydrolysis of cyanide ions and prevent TMTM from being hydrolyzed under alkaline conditions. After adding sulfuric acid, the endpoint pH of the oxidation reaction is reduced from 8 to 9 to 6.5 to 7, the reaction system is basically neutral, the oxidation reaction is more thorough, and the final product yield and quality are significantly improved.

[0035] The condensation liquid produced by the condensation reaction of the present invention has stable properties and can be stored for a long time, and the condensation reaction and the oxidation reaction can be carried out separately. Then, through the automatic control of the production device, the continuous production of the entire reaction process can be achieved, thereby improving production efficiency and economic benefits.

[0036] The preparation method of tetramethylthiuram monosulfide of the present invention has a product yield of ≥97%, a product purity of ≥99%, and a melting point of 108°C.

[0037] In some embodiments of the present invention, in step (A), sodium cyanide solution, NaOH solution and water are mixed in the first microchannel reactor and then enter the second microchannel reactor, where they are mixed with dimethylamine solution in the second microchannel reactor. After cooling, they enter the third microchannel reactor and undergo condensation reaction with carbon disulfide in the third microchannel reactor.

[0038] The desulfurizing agent of the present invention is added in the condensation reaction stage. Sodium cyanide is a strong base and a weak acid salt. The aqueous solution is alkaline. Sodium cyanide is added in the condensation reaction to promote the condensation reaction. The cyanide ions that play a desulfurizing role do not participate in the condensation reaction and can maintain a high concentration in the reaction system, which is conducive to the subsequent oxidation reaction.

[0039] In some embodiments of the present invention, in step (A), the molar ratio of sodium cyanide, NaOH and dimethylamine is (0.5-0.6):(0.5-0.6):1; preferably, the molar ratio of sodium cyanide, NaOH and dimethylamine is 0.51:0.5:1.

[0040] In some embodiments of the present invention, in step (A), the mass ratio of water to dimethylamine is (1.5-2):1; typically but not limiting, for example, the mass ratio of water to dimethylamine is 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1, etc.; preferably, the mass ratio of water to dimethylamine is 1.7:1.

[0041] In some embodiments of the present invention, in step (A), the sodium cyanide solution is a sodium cyanide aqueous solution with a concentration of 25 wt % to 35 wt %, preferably a 30 wt % sodium cyanide aqueous solution.

[0042] In some embodiments of the present invention, in step (A), the NaOH solution is a NaOH aqueous solution with a concentration of 30 wt % to 40 wt %, preferably a 32 wt % NaOH aqueous solution.

[0043] In some embodiments of the present invention, in step (A), the dimethylamine solution is a dimethylamine aqueous solution with a concentration of 30 wt % to 45 wt %, preferably a 40 wt % dimethylamine aqueous solution.

[0044] In some embodiments of the present invention, in step (A), the molar ratio of dimethylamine to carbon disulfide is 1:(1.03-1.07); typically but not limiting, for example, the molar ratio of dimethylamine to carbon disulfide is 1:1.03, 1:1.04, 1:1.05, 1:1.06 or 1:1.07, etc.

[0045] Since the conversion rate of the condensation reaction is high, there is no need to add excessive carbon disulfide, and the molar ratio of dimethylamine to carbon disulfide is reduced to 1:1.03-1.07.

[0046] In some embodiments of the present invention, in step (A), the mixture is cooled to 10-20° C. and enters the third microchannel reactor; preferably, the mixture is cooled to 15° C. and enters the third microchannel reactor.

[0047] In some embodiments of the present invention, in step (A), the condensation reaction temperature is 15-20° C., and the condensation reaction time is 5-100 seconds. The condensation reaction time of the present invention is shortened to seconds.

[0048] In some embodiments of the present invention, in step (A), the aging time is 10 to 60 min; preferably, the aging time is 20 to 40 min.

[0049] In some embodiments of the present invention, in step (A), after aging, the mixture is cooled to 15-20° C. to obtain a condensation reaction solution.

[0050] In some embodiments of the present invention, in step (B), the molar ratio of dimethylamine to H2O2 in the mixed solution is 1:0.5-0.6; preferably, the molar ratio of dimethylamine to H2O2 in the mixed solution is 1:0.54.

[0051] In some embodiments of the present invention, in step (B), the molar ratio of dimethylamine to H2SO4 in the mixed solution is 1:0.3-0.4; preferably, the molar ratio of dimethylamine to H2SO4 in the mixed solution is 1:0.34.

[0052] In some embodiments of the present invention, in step (B), the concentration of hydrogen peroxide is 25 wt % to 30 wt %; preferably, the concentration of hydrogen peroxide is 27.5 wt %.

[0053] In some embodiments of the present invention, in step (B), the sulfuric acid solution is 98% concentrated sulfuric acid.

[0054] In some embodiments of the present invention, in step (B), a mixture of a hydrogen peroxide solution and a sulfuric acid solution is added dropwise to the condensation reaction solution until the pH of the system is 6.5 to 7, which is the end point.

[0055] In some embodiments of the present invention, in step (B), the temperature of the oxidation reaction is 15 to 25° C., and the time of the oxidation reaction is 3.5 to 4.5 hours.

[0056] The time required for the preparation method of tetramethylthiuram monosulfide of the present invention is 4 to 5 hours, and the production efficiency is greatly improved.

[0057] In some embodiments of the present invention, the method for preparing tetramethylthiuram monosulfide further comprises: centrifuging, washing, drying and crushing the reaction solution obtained after the oxidation reaction to obtain tetramethylthiuram monosulfide.

[0058] The present invention uses water as a solvent, and mother liquor water is recovered when the product is centrifuged. 60% of the mother liquor water can be recycled, thereby reducing wastewater discharge; and the COD of the wastewater is reduced to about 8000 mg / L, greatly reducing the pressure of sewage treatment.

[0059] See also Figure 1 In some embodiments of the present invention, a device for implementing the above-mentioned method for preparing tetramethylthiuram monosulfide is also provided, comprising a first microchannel reactor 1, a second microchannel reactor 2, a first heat exchanger 3, a third microchannel reactor 4, an aging tank 5, a second heat exchanger 6, a condensation liquid storage tank 7 and an oxidation tank 8 connected in sequence.

[0060] In some specific embodiments of the present invention, water, NaOH solution, and sodium cyanide solution are mixed in the first microchannel reactor 1, and then enter the second microchannel reactor 2 to mix with the dimethylamine solution in the microchannel reactor 2. The mixed solution (including water, NaOH, sodium cyanide, and dimethylamine) at the outlet of the second microchannel reactor 2 enters the heat exchanger 3 and is cooled to 15°C, and then enters the third microchannel reactor 4 to undergo a condensation reaction with carbon disulfide in the third microchannel reactor 4. After the reaction, it enters the aging tank 5 for aging for 0.5h, and then is cooled to 15-20°C through the heat exchanger 6. After cooling, it enters the condensation liquid storage tank 7 for storage.

[0061] After the condensation reaction liquid in the condensation liquid storage tank 7 enters the oxidation tank 8, a mixture of hydrogen peroxide and sulfuric acid solution is added dropwise to carry out an oxidation reaction. The dropping time is 3 to 4 hours, and the end point is reached when the pH value is 6.5 to 7. After the end point, it is stirred for 0.5 hours, and the liquid temperature in the oxidation tank is controlled at 15 to 25°C throughout the process.

[0062] The reaction liquid after the oxidation reaction is centrifuged, washed, dried, crushed and packaged to obtain TMTM. Part of the mother liquor from the centrifugation is used, and part of it is used for sewage treatment. During centrifugation, TMTM needs to be washed with clean water. In the middle and late stages of washing, the washing liquid is relatively clear and clean. This part of the washing liquid can be used for application, part of it is used to replace the clean water added during the condensation reaction, and the other part can be used to replace the clean water for washing during the next centrifugation.

[0063] The present invention realizes continuous production through condensation reaction by using a microchannel reactor, and subsequent aging and oxidation reactions can be automatically switched through multiple reactors to realize the continuity of the entire reaction process, thereby greatly improving production efficiency.

[0064] Example 1

[0065] The preparation method of tetramethylthiuram monosulfide provided in this embodiment comprises the following steps:

[0066] (A) Water, NaOH aqueous solution (32 wt%), and sodium cyanide aqueous solution (30 wt%) are mixed in the first microchannel reactor 1, and then enter the second microchannel reactor 2, and are mixed with dimethylamine solution (40 wt%) in the microchannel reactor 2. The mixed liquid at the outlet of the second microchannel reactor 2 (including water, NaOH, sodium cyanide and dimethylamine, wherein the molar ratio of NaOH, sodium cyanide and dimethylamine is 0.5:0.51:1, and the mass ratio of water and dimethylamine added in the first microchannel reactor 1 is 1.7:1) enters the heat exchanger 3 and is cooled to 15°C, and then enters the third microchannel reactor 4, and undergoes a condensation reaction with carbon disulfide in the third microchannel reactor 4, and the molar ratio of dimethylamine to carbon disulfide is 1:1.05. After the reaction, it enters the aging tank 5 for aging for 0.5 h, and then is cooled to 20°C through the heat exchanger 6. After cooling, it enters the condensation liquid storage tank 7 for storage.

[0067] (B) After the condensation reaction liquid in the condensation liquid storage tank 7 enters the oxidation tank 8, a mixture of 27.5wt% hydrogen peroxide and 98% concentrated sulfuric acid is added dropwise, and the molar ratio of dimethylamine, H2O2 in the mixture and H2SO4 in the mixture is 1:0.54:0.34, to carry out oxidation reaction. The dropping time is 3.5h, and the end point is reached when the pH value reaches 6.8. After the end point, the mixture is stirred for 0.5h, and the liquid temperature in the oxidation tank is controlled not to exceed 20°C throughout the whole process.

[0068] (C) The reaction liquid of the oxidation reaction is centrifuged, washed with water, dried, crushed, and packaged to obtain TMTM.

[0069] The yield of the product in this embodiment is 97.8%, the purity of the product is 99.4%, and the COD of the wastewater is 7800 mg / L.

[0070] Example 2

[0071] The preparation method of tetramethylthiuram monosulfide provided in this embodiment comprises the following steps:

[0072] (A) Water, NaOH aqueous solution (32 wt%), and sodium cyanide aqueous solution (30 wt%) are mixed in the first microchannel reactor 1, and then enter the second microchannel reactor 2, and are mixed with dimethylamine solution (40 wt%) in the microchannel reactor 2. The mixed liquid at the outlet of the second microchannel reactor 2 (including water, NaOH, sodium cyanide and dimethylamine, wherein the molar ratio of NaOH, sodium cyanide and dimethylamine is 0.6:0.6:1, and the mass ratio of water and dimethylamine added in the first microchannel reactor 1 is 2:1) enters the heat exchanger 3 and is cooled to 15°C, and then enters the third microchannel reactor 4, and undergoes a condensation reaction with carbon disulfide in the third microchannel reactor 4, and the molar ratio of dimethylamine to carbon disulfide is 1:1.03. After the reaction, it enters the aging tank 5 for aging for 0.5 h, and then is cooled to 15°C through the heat exchanger 6. After cooling, it enters the condensation liquid storage tank 7 for storage.

[0073] (B) After the condensation reaction liquid in the condensation liquid storage tank 7 enters the oxidation tank 8, a mixture of 27.5wt% hydrogen peroxide and 98% concentrated sulfuric acid is added dropwise, and the molar ratio of dimethylamine, H2O2 in the mixture and H2SO4 in the mixture is 1:0.6:0.4. The oxidation reaction is carried out, and the dropping time is 4h. The end point is reached when the pH value is 7. After the end point, it is stirred for 0.5h. The liquid temperature in the oxidation tank is controlled not to exceed 25°C throughout the whole process.

[0074] (C) The reaction liquid of the oxidation reaction is centrifuged, washed with water, dried, crushed, and packaged to obtain TMTM.

[0075] The yield of the product in this example is 97.3%, the purity of the product is 99.1%, and the COD of the wastewater is 8200 mg / L.

[0076] Example 3

[0077] The preparation method of tetramethylthiuram monosulfide provided in this embodiment comprises the following steps:

[0078] (A) Water, NaOH aqueous solution (32 wt%), and sodium cyanide aqueous solution (30 wt%) are mixed in the first microchannel reactor 1, and then enter the second microchannel reactor 2, and are mixed with dimethylamine solution (40 wt%) in the microchannel reactor 2. The mixed liquid at the outlet of the second microchannel reactor 2 (including water, NaOH, sodium cyanide and dimethylamine, wherein the molar ratio of NaOH, sodium cyanide and dimethylamine is 0.55:0.55:1, and the mass ratio of water and dimethylamine added in the first microchannel reactor 1 is 1.5:1) enters the heat exchanger 3 and is cooled to 15°C, and then enters the third microchannel reactor 4, and undergoes a condensation reaction with carbon disulfide in the third microchannel reactor 4, and the molar ratio of dimethylamine to carbon disulfide is 1:1.07. After the reaction, it enters the aging tank 5 for aging for 0.5 h, and then is cooled to 15°C through the heat exchanger 6. After cooling, it enters the condensation liquid storage tank 7 for storage.

[0079] (B) After the condensation reaction liquid in the condensation liquid storage tank 7 enters the oxidation tank 8, a mixture of 27.5wt% hydrogen peroxide and 98% concentrated sulfuric acid is added dropwise, and the molar ratio of dimethylamine, H2O2 in the mixture and H2SO4 in the mixture is 1:0.5:0.3. The oxidation reaction is carried out, and the dropping time is 3h. The pH is added until 6.5, which is the end point. After the end point, it is stirred for 0.5h. The liquid temperature in the oxidation tank is controlled not to exceed 20°C throughout the whole process.

[0080] (C) The reaction liquid of the oxidation reaction is centrifuged, washed with water, dried, crushed, and packaged to obtain TMTM.

[0081] The yield of the product in this example is 97.1%, the purity of the product is 99%, and the COD of the wastewater is 8300 mg / L.

[0082] Comparative Example 1

[0083] The preparation method of tetramethylthiuram monosulfide provided in this comparative example comprises the following steps:

[0084] Into a reaction kettle filled with pure water, 40wt% dimethylamine aqueous solution and emulsifier OP-10 are added in sequence under stirring, the temperature is controlled at 10-35°C, carbon disulfide (half of the total amount) is added dropwise, a condensation reaction is carried out, and the pH value is reacted to 7-8, sodium cyanide aqueous solution (30wt%) is added, and the remaining carbon disulfide and hydrogen peroxide (27.5wt%) are added dropwise, the carbon disulfide is added before the hydrogen peroxide, and after the hydrogen peroxide is added, after a period of reaction, solid-liquid separation, washing, drying, crushing and packaging are carried out to obtain TMTM.

[0085] The molar ratio of dimethylamine, carbon disulfide, hydrogen peroxide and sodium cyanide is 1:1.2:0.54:0.51; the steps of solid-liquid separation, washing, drying, crushing and packaging are the same as those in Example 1.

[0086] The yield of the product in this comparative example is 87%, the purity of the product is 98.5%, and the COD of the wastewater is 30000 mg / L.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing tetramethylthiuram monosulfide, characterized in that: The steps include: (A) a mixed solution containing sodium cyanide, NaOH and dimethylamine is subjected to a condensation reaction with carbon disulfide in a microchannel reactor, and then aged and cooled to obtain a condensation reaction liquid; (B) adding a mixture of hydrogen peroxide and sulfuric acid solution into the condensation reaction solution until the pH of the system is 6.5-7, and obtaining the tetramethylthiuram monosulfide after oxidation reaction.

2. The method for preparing tetramethylthiuram monosulfide according to claim 1, characterized in that: In step (A), sodium cyanide solution, NaOH solution and water are mixed in the first microchannel reactor and then enter the second microchannel reactor, where they are mixed with dimethylamine solution in the second microchannel reactor. After cooling, they enter the third microchannel reactor and undergo condensation reaction with carbon disulfide in the third microchannel reactor.

3. The method for preparing tetramethylthiuram monosulfide according to claim 1, characterized in that: In step (A), the molar ratio of the sodium cyanide, the NaOH and the dimethylamine is (0.5-0.6):(0.5-0.6):

1.

4. The method for preparing tetramethylthiuram monosulfide according to claim 2, characterized in that: In step (A), the mass ratio of the water to the dimethylamine is (1.5-2):

1.

5. The method for preparing tetramethylthiuram monosulfide according to claim 2, characterized in that: In step (A), the concentration of the sodium cyanide solution is 25wt%~35wt%, the concentration of the NaOH solution is 30wt%~40wt%, and the concentration of the dimethylamine solution is 30wt%~45wt%.

6. The method for preparing tetramethylthiuram monosulfide according to claim 1, characterized in that: In step (A), the molar ratio of the dimethylamine to the carbon disulfide is 1:(1.03-1.07).

7. The method for preparing tetramethylthiuram monosulfide according to claim 1, characterized in that: In step (A), the temperature of the condensation reaction is 15-20° C., and the time of the condensation reaction is 5-100 s.

8. The method for preparing tetramethylthiuram monosulfide according to claim 1, characterized in that: In step (A), the aging time is 10 to 60 minutes.

9. The method for preparing tetramethylthiuram monosulfide according to claim 1, characterized in that: The molar ratio of the dimethylamine in step (A) to the H2O2 in the mixed solution in step (B) is 1:0.5-0.

6.

10. The method for preparing tetramethylthiuram monosulfide according to claim 1, characterized in that: The molar ratio of the dimethylamine in step (A) to the H2SO4 in the mixed solution in step (B) is 1:0.3-0.

4.

11. The method for preparing tetramethylthiuram monosulfide according to claim 1, characterized in that: In step (B), the temperature of the oxidation reaction is 15-25° C., and the time of the oxidation reaction is 3.5-4.5 hours.

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