Process for the synthesis of rubber accelerator cbs by catalytic oxidation with solvents

Abstract

The application provides a method for synthesizing rubber accelerator CBS by solvent catalytic oxidation, which comprises the following steps: S1, adding an ethanol solution into a reactor, then adding MBT, and stirring to make the MBT into a uniform slurry; S2, under the stirring state, dropping a cyclohexane into the reactor to react with the MBT to obtain an MBT amine salt solution; S3, preparing a hydrogen peroxide solution, and adding potassium acetate to obtain a hydrogen peroxide solution containing a catalyst; S4, under the stirring state, dropping the hydrogen peroxide solution containing the catalyst into the MBT amine salt solution; S5, after the dropping of the hydrogen peroxide solution containing the catalyst is completed, using sodium hypochlorite to determine the end point of the oxidation reaction; and S6, after the reaction is determined to reach the end point, stirring for a period of time, filtering, washing with water and drying the reaction product to obtain the rubber accelerator CBS. Through the technical scheme, the yield and purity of the rubber accelerator CBS are improved, and less wastewater is generated in the reaction process, and basically no waste salt is generated.

Description

Technical Field

[0001] This invention relates to the field of rubber accelerator CBS production technology, and more specifically, to a method for synthesizing rubber accelerator CBS by solvent-based catalytic oxidation. Background Technology

[0002] CBS, chemical name: N-cyclohexyl-2-benzothiazole sulfenamide, is a white or off-white crystalline or powdery rubber accelerator. It is a commonly used post-curing accelerator with the advantages of excellent anti-scorching properties and short curing time. When used in combination with accelerators M, DM, and TMTD, it can improve the tensile strength and elongation of the vulcanizate. It is particularly suitable for synthetic and natural rubbers reinforced with carbon black using the oil furnace method with high alkalinity. It causes slight discoloration, does not bloom, and the vulcanizate has excellent aging resistance. It is mainly used in the manufacture of industrial products such as tires, hoses, rubber sheets, and cables.

[0003] In related technologies, the industrial synthetic rubber accelerator CBS is typically produced using two methods. One is the sodium hypochlorite oxidation method, where the accelerator MBT is mixed with cyclohexylamine to form an amine salt, which is then oxidized using sodium hypochlorite as the oxidant to generate CBS. Although this process is relatively mature and has a high yield, it produces a large volume of wastewater containing significant amounts of sodium chloride, resulting in high wastewater treatment costs and significant environmental harm. The other method is the mixed oxidation method, where MBT is mixed with cyclohexylamine to form an amine salt, which is then oxidized using both sodium hypochlorite and hydrogen peroxide as oxidants to generate CBS. In this method, sodium hypochlorite is added dropwise first, followed by hydrogen peroxide. While the yield is comparable to the sodium hypochlorite oxidation method, the amount of sodium hypochlorite used is reduced, and the amount of sodium chloride in the wastewater is also reduced. However, the wastewater volume remains large, and the sodium chloride must still be treated during wastewater treatment, meaning the wastewater and salt problems persist. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] Therefore, the present invention aims to provide a solvent-based catalytic oxidation method for synthesizing rubber accelerator CBS. This method allows the reaction system to proceed in a homogeneous solvent environment, enabling some impurities to dissolve in the solvent and reducing the presence of impurities in the target product. Furthermore, using potassium acetate as a catalyst and hydrogen peroxide as an oxidant improves the yield of CBS, while generating less wastewater and no waste salts, resulting in low wastewater treatment costs. Simultaneously, sodium hypochlorite is used to determine the endpoint of the oxidation reaction. In the presence of potassium acetate, sodium hypochlorite can further facilitate the rapid combination of unbound cyclohexylamine radicals and 2-mercaptobenzothiazole radicals in the reaction system to generate CBS, thus producing more of the target product.

[0006] To achieve the above objectives, the present invention provides a method for the solvent-based catalytic oxidation synthesis of rubber accelerator CBS, comprising the following steps:

[0007] S1, Add the ethanol solution to the reactor, then add MBT and stir to make the MBT into a uniform slurry;

[0008] S2, under stirring, cyclohexane is added dropwise to the reactor to react with MBT and prepare MBT amine salt solution;

[0009] S3, prepare a hydrogen peroxide solution by adding potassium acetate to obtain a hydrogen peroxide solution containing a catalyst;

[0010] S4, while stirring, add hydrogen peroxide solution containing catalyst dropwise to the MBT amine salt solution prepared in step S2;

[0011] S5. After the hydrogen peroxide solution containing the catalyst has been added dropwise, sodium hypochlorite is used to determine the endpoint of the oxidation reaction.

[0012] S6. After determining that the reaction has reached its endpoint, continue stirring for a period of time, then filter, wash with water, and dry the reaction product to prepare the rubber accelerator CBS.

[0013] In this technical solution, the reaction system is carried out in a homogeneous solvent environment (ethanol solution). Some impurities during the reaction process can dissolve in the solvent, reducing the presence of impurities in the target product and improving its purity. Stirring allows MBT to form a uniform slurry in the ethanol solution. After the addition of cyclohexane, the cyclohexane can react more fully with MBT, fully forming MBT amine salts, which is beneficial for the formation of more target products in subsequent oxidation processes, thus increasing the yield. Using potassium acetate as a catalyst and hydrogen peroxide as an oxidant improves the yield of rubber accelerator CBS, and the reaction generates less wastewater and no waste salts, resulting in low wastewater treatment costs. Sodium hypochlorite is used to determine the endpoint of the oxidation reaction. In the presence of potassium acetate, sodium hypochlorite can further facilitate the rapid combination of unbound cyclohexylamine radicals and 2-mercaptobenzothiazole radicals in the reaction system to generate rubber accelerator CBS, producing more of the target product. Using the solvent-based catalytic oxidation method for synthesizing rubber accelerator CBS proposed in this invention, the yield of the target product rubber accelerator CBS can reach over 97%. This invention uses an ethanol solution as the solvent in the reaction system. On the one hand, ethanol can be recovered and reused by distillation. On the other hand, the yield and purity of the target product are high, the byproducts are few, and the raw material consumption is low.

[0014] In the above technical solution, preferably, the molar ratio of MBT, hydrogen peroxide, and cyclohexylamine is 1.0:(1.01-1.35):(1.8-2.9).

[0015] In any of the above technical solutions, preferably, the molar ratio of MBT, hydrogen peroxide, and cyclohexylamine is 1.0:(1.05-1.10):(2.0-2.3).

[0016] In this technical solution, the dosage of MBT, hydrogen peroxide, and cyclohexylamine is limited, thereby consuming less raw materials and obtaining more of the target product, ensuring the yield of the target product. The yield of rubber accelerator CBS can reach over 97%.

[0017] In any of the above technical solutions, preferably, in step S1, the amount of ethanol used in each mole of MBT reaction system is 500mL-1500mL, and the amount of water used is 100mL-400mL.

[0018] In this technical solution, the ethanol solution used as a solvent is further optimized to ensure the solubility of the raw materials used in the reaction system. This allows the reaction to proceed in a homogeneous solvent environment, selectively dissolving some impurities in MBT. The MBT becomes a uniform slurry after stirring. After the addition of cyclohexylamine, the cyclohexylamine can react more fully with the MBT slurry, fully forming the MBT amine salt. Furthermore, this facilitates the formation of more of the target product during subsequent oxidation, improving yield and purity, reducing byproducts, and saving raw materials. Additionally, the ethanol can be recovered and reused through distillation, which helps reduce production costs.

[0019] In any of the above technical solutions, preferably, in step S3, the mass fraction of hydrogen peroxide in the catalyst-containing hydrogen peroxide aqueous solution is 7%-15%.

[0020] In any of the above technical solutions, preferably, the mass of potassium acetate added in step S3 is 0.045‰-0.05‰ of the mass of MBT added in step S1.

[0021] In any of the above technical solutions, preferably, step S3, preparing a hydrogen peroxide solution and simultaneously adding potassium acetate to obtain a catalyst-containing hydrogen peroxide solution, specifically includes the following steps: S31, adding water and a 30% hydrogen peroxide solution by mass to a container equipped with a stirrer, and stirring for 5 minutes; S32, adding potassium acetate to the above hydrogen peroxide solution, and continuing to stir for 5 minutes to prepare a catalyst-containing hydrogen peroxide solution.

[0022] In this technical solution, the preparation method of the catalyst-containing hydrogen peroxide solution is simple and reliable, with potassium acetate catalyst and hydrogen peroxide being thoroughly and uniformly mixed. The mass fraction of hydrogen peroxide is 7%-15%, and the amount of potassium acetate is 0.045‰-0.05‰ of the mass of MBT added. Under the action of the carboxyl groups of the catalyst, the oxidizing power of the oxidant hydrogen peroxide is improved, and its oxidizing power is stronger than that of sodium hypochlorite. This is more conducive to the formation of the target product during the oxidation process, thus improving the yield of the target product. This invention uses hydrogen peroxide as the oxidant and potassium acetate as the catalyst. Water is generated during the oxidation process, without salt formation. The wastewater contains no salt, making wastewater treatment simpler and lower in cost, which is conducive to achieving a green process route and is more beneficial to environmental protection. In addition, potassium acetate is inexpensive and readily available, which helps to reduce production costs.

[0023] In any of the above technical solutions, preferably, the reaction temperature in steps S4 and S5 is 25℃-45℃.

[0024] In this technical solution, the temperature of the reaction system is controlled between 25℃ and 45℃, which is more conducive to the production of the target product, increases the yield and conversion rate, reduces the generation of by-products, and improves the utilization rate of raw materials.

[0025] In any of the above technical solutions, preferably, step S5, after the hydrogen peroxide solution containing the catalyst has been added dropwise, uses sodium hypochlorite to determine the endpoint of the oxidation reaction, specifically includes the following steps:

[0026] S51, after the hydrogen peroxide solution containing the catalyst is added dropwise, continue stirring for 10 minutes;

[0027] S52, sodium hypochlorite is added dropwise to the reaction solution using a peristaltic pump. The concentration of sodium hypochlorite is 15.2%, the speed of the peristaltic pump is 0.8 rpm to 20.0 rpm, and the amount of sodium hypochlorite used is less than or equal to 0.9% of the total oxidant mass. The total oxidant is hydrogen peroxide and sodium hypochlorite added during the reaction.

[0028] S53, after adding sodium hypochlorite for 1 minute, every 20 seconds, take a drop of the reaction solution from the reaction system and add it to the indicator on the spot plate. The indicator is a mixed solution of starch, potassium iodide and ammonium sulfate. If the indicator turns blue, stop adding sodium hypochlorite to determine that the reaction has reached the endpoint.

[0029] In this technical solution, sodium hypochlorite is used to confirm the endpoint of the oxidation reaction, which is easier to observe and allows for timely cessation of the oxidation reaction, effectively preventing the over-oxidation of the target product. Moreover, the amount of sodium hypochlorite used is extremely small, so it basically does not cause waste salt production. Furthermore, in the presence of potassium acetate, sodium hypochlorite can further promote the rapid combination of unbound cyclohexylamine free radicals and 2-mercaptobenzothiazole free radicals in the reaction system to generate CBS, producing more of the target product and improving the yield of the target product.

[0030] In any of the above technical solutions, preferably, in step S1, the stirring time is 30 min; in step S2, the stirring time is 30 min; in step S4, a peristaltic pump is used to add hydrogen peroxide solution containing catalyst, and the rotation speed of the peristaltic pump is 1.0 rpm - 25.0 rpm; in step S6, the stirring time is 10 min.

[0031] This technical solution further optimizes the stirring time, the dropping method and rate of the catalyst-containing hydrogen peroxide solution in the preparation process, thereby further ensuring the yield and purity of the target product and reducing the generation of by-products and impurities. The rotational speed of the peristaltic pump = rotational speed per unit volume per unit time * reaction time * liquid volume.

[0032] The solvent-based catalytic oxidation method for synthesizing rubber accelerator CBS proposed in this invention has the following beneficial technical effects:

[0033] (1) The method for synthesizing rubber accelerator CBS by solvent catalytic oxidation proposed in this invention can achieve a yield of over 97%, with high yield and high purity. Moreover, the material is loose, appears as white crystals, and has high quality. The preparation method is simple and reliable, generates little wastewater, and contains virtually no sodium chloride salts, resulting in low wastewater treatment costs.

[0034] (2) The solvent-based catalytic oxidation method for synthesizing rubber accelerator CBS proposed in this invention uses ethanol solution as the solvent. All raw materials are soluble in ethanol solution, and the entire reaction system is carried out in a homogeneous solvent environment. Ethanol solution can selectively dissolve some impurities in MBT and also makes MBT a uniform slurry. After the addition of cyclohexane, cyclohexane can more fully contact and react with the MBT slurry, fully forming MBT amine salts, which is beneficial for the formation of the target product and increases the yield. Ethanol solution can also dissolve some impurities generated during subsequent oxidation, improving the purity of the target product, rubber accelerator CBS. In addition, the ethanol solution can be recovered by distillation, which helps reduce production costs.

[0035] (3) The solvent-based catalytic oxidation method for synthesizing rubber accelerator CBS proposed in this invention uses potassium acetate as a catalyst and hydrogen peroxide as an oxidant. The carboxyl groups of the catalyst enhance the oxidizing power of the oxidant hydrogen peroxide, making it stronger than sodium hypochlorite. This process is more conducive to the formation of the target product and increases its yield. Furthermore, water is generated during the oxidation process without salt formation, resulting in wastewater that is salt-free. This simplifies wastewater treatment, reduces costs, and facilitates a green process, thus protecting the environment. Additionally, potassium acetate is inexpensive and readily available, further reducing production costs.

[0036] (4) The solvent-based catalytic oxidation method for synthesizing rubber accelerator CBS proposed in this invention uses sodium hypochlorite to confirm the endpoint of the oxidation reaction, which is easier to observe and can stop the oxidation reaction in time, effectively preventing the over-oxidation of the target product. Moreover, the amount of sodium hypochlorite used is extremely small, and it will not cause waste salt to be generated. Furthermore, in the presence of potassium acetate, sodium hypochlorite can further enable unbound cyclohexylamine free radicals and 2-mercaptobenzothiazole free radicals in the reaction system to rapidly combine to generate CBS, generating more target products and improving the yield of target products.

[0037] Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description or may be learned by practice of the invention. Detailed Implementation

[0038] This invention discloses a solvent-based catalytic oxidation method for synthesizing the rubber accelerator CBS. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art will clearly be able to modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0039] The present invention will be further illustrated below with reference to the embodiments:

[0040] Example 1

[0041] A method for the solvent-based catalytic oxidation synthesis of rubber accelerator CBS includes the following steps:

[0042] Add 113.3g of water and 56.7g of 30% hydrogen peroxide solution to a 250ml three-necked flask equipped with a stirrer, stir for 5 minutes, then add 0.002g of potassium acetate and continue stirring for 5 minutes to prepare a 10% hydrogen peroxide solution containing a catalyst.

[0043] Add 120g of 78% ethanol solution and 40g of MBT to a 500ml three-necked flask equipped with a stirrer, and stir for 30 minutes to make it into a homogeneous slurry.

[0044] 45g of cyclohexylamine was added dropwise to the three-necked flask using a peristaltic pump and stirred for 30 minutes to prepare an MBT amine salt solution.

[0045] The prepared hydrogen peroxide solution containing catalyst with a mass fraction of 10% was added dropwise to the MBT amine salt solution using a peristaltic pump. The peristaltic pump rotation speed was controlled at 1.0 rpm, the reaction time was 210 min, and the reaction temperature was 25℃-40℃.

[0046] After the hydrogen peroxide solution containing the catalyst was added dropwise, stirring was continued for 10 minutes. Then, sodium hypochlorite with a mass fraction of 15.2% was added dropwise to the reaction solution using a peristaltic pump, with the peristaltic pump speed controlled at 0.8 rpm.

[0047] After adding sodium hypochlorite for 1 minute, every 20 seconds, a drop of solution from the reaction system is added to the indicator on the spot plate. The indicator is a mixed solution of starch, potassium iodide, and ammonium sulfate.

[0048] When the indicator turns blue, stop adding sodium hypochlorite. 0.89g of sodium hypochlorite with a mass fraction of 15.2% has been consumed. The oxidation reaction has reached its endpoint. Continue stirring for 10 minutes, then filter, wash with water, and dry to obtain the rubber accelerator CBS product.

[0049] The CBS rubber accelerator product was tested and found to contain 59.81g of loose material, which appeared as white crystals. The yield was 97.5%, the melting point was 98.9℃, and the purity was >98.5% as determined by high performance liquid chromatography.

[0050] Example 2

[0051] A method for the solvent-based catalytic oxidation synthesis of rubber accelerator CBS includes the following steps:

[0052] Add 2.3 kg of water and 1.23 kg of 30% hydrogen peroxide solution to a 5L stainless steel reaction vessel equipped with a stirrer, stir for 5 min, then add 0.04 g of potassium acetate and continue stirring for 5 min to prepare a 10% hydrogen peroxide solution containing the catalyst.

[0053] Add 2.5 kg of 78% ethanol and 0.82 kg of MBT to a 10 L stainless steel reaction vessel equipped with a stirrer, and stir for 30 min to make it into a uniform slurry.

[0054] 0.91 kg of cyclohexylamine was added dropwise using a peristaltic pump and stirred for 30 min to prepare an MBT amine salt solution.

[0055] A 10% (w / w) hydrogen peroxide solution containing the catalyst, prepared above, was added dropwise to MBT amine salt using a peristaltic pump. The peristaltic pump speed was controlled at 20.6 rpm, the reaction time at 230 min, and the reaction temperature at 25℃-40℃.

[0056] After the hydrogen peroxide solution containing the catalyst was added dropwise, stirring was continued for 10 minutes. Then, sodium hypochlorite with a mass fraction of 15.2% was added dropwise to the reaction solution using a peristaltic pump, with the pump speed controlled at 16.3 rpm.

[0057] After adding sodium hypochlorite for 1 minute, every 20 seconds, a drop of solution from the reaction system is added to the indicator on the spot plate. The indicator is a mixed solution of starch, potassium iodide, and ammonium sulfate.

[0058] When the indicator turns blue, stop adding sodium hypochlorite. 17.3g of sodium hypochlorite with a mass fraction of 15.2% has been consumed. The oxidation reaction has reached its endpoint. Continue stirring for 10 minutes, then filter, wash with water, and dry to obtain the rubber accelerator CBS product.

[0059] The CBS rubber accelerator product was tested and found to weigh 1.23 kg. The material was loose, and the appearance was white crystals. The yield reached 97.8%, the melting point reached 99.0℃, and the purity was >98.6% as determined by high performance liquid chromatography.

[0060] Therefore, the solvent-based catalytic oxidation method for synthesizing rubber accelerator CBS proposed in this invention can be applied to the production of large quantities of rubber accelerator CBS, and the yield, purity, and quality of the rubber accelerator CBS are high.

[0061] Comparative Example 1

[0062] Add 113.3g of water and 56.7g of 30% hydrogen peroxide solution to a 250ml three-necked flask equipped with a stirrer, stir for 5 minutes to prepare a 10% hydrogen peroxide solution.

[0063] Add 120g of 78% ethanol and 40g of MBT to a 500ml three-necked flask equipped with a stirrer, and stir for 30 minutes until it becomes a homogeneous slurry.

[0064] 45g of cyclohexylamine was added dropwise using a peristaltic pump and stirred for 30 minutes to prepare an MBT amine salt solution.

[0065] A 10% hydrogen peroxide solution prepared above was added dropwise to MBT amine salt using a peristaltic pump. The peristaltic pump rotation speed was controlled at 1.0 rpm, the reaction time was 210 min, and the temperature was 25℃-40℃.

[0066] After the hydrogen peroxide solution was added, stirring was continued for 10 minutes. Then, sodium hypochlorite with a mass fraction of 15.2% was added dropwise to the reaction solution using a peristaltic pump, with the pump speed controlled at 0.8 rpm.

[0067] After adding sodium hypochlorite for 1 minute, every 20 seconds, a drop of solution from the reaction system is added to the indicator on the spot plate. The indicator is a mixed solution of starch, potassium iodide, and ammonium sulfate.

[0068] When the indicator turns blue, stop adding sodium hypochlorite. 0.52g of 15.2% sodium hypochlorite will be consumed. The oxidation reaction will reach its endpoint. Continue stirring for 10 minutes, then filter, wash with water, and dry to obtain the rubber accelerator CBS product.

[0069] The tested product, CBS rubber accelerator, weighed 54.41g, with a yield of 88.7%, which was much lower than the yield in Example 1. The melting point reached 97.2℃, and the purity, as determined by high-performance liquid chromatography, was >97.6%. The quality of the CBS rubber accelerator product was inferior to that in Example 1.

[0070] Therefore, adding potassium acetate to hydrogen peroxide solution improves the yield and quality of the rubber accelerator CBS. Potassium acetate is a strong base-weak acid salt, which creates an alkaline environment in the reaction solution, favoring the formation of CBS. Simultaneously, potassium acetate contains carboxyl groups, which enhance the oxidation process of hydrogen peroxide, further promoting the formation of CBS.

[0071] Comparative Example 2

[0072] Add 113.3g of water and 56.7g of 30% hydrogen peroxide solution to a 250ml three-necked flask equipped with a stirrer, stir for 5 minutes, then add 0.002g of potassium acetate and continue stirring for 5 minutes to prepare a 10% hydrogen peroxide solution containing a catalyst.

[0073] Add 120g of 78% ethanol solution and 40g of MBT to a 500ml three-necked flask equipped with a stirrer, and stir for 30 minutes to make it into a homogeneous slurry.

[0074] 45g of cyclohexylamine was added dropwise using a peristaltic pump and stirred for 30 minutes to prepare an MBT amine salt solution.

[0075] A 10% hydrogen peroxide solution containing the catalyst, prepared above, was added dropwise to MBT amine salt using a peristaltic pump. The peristaltic pump rotation speed was controlled at 1.0 rpm, the reaction time was 213 min, and the temperature was 25℃-40℃.

[0076] When the reaction is nearing its endpoint, a small amount of solution is intermittently added dropwise from the reaction system to the indicator on the spot plate. The indicator is a mixed solution of starch, potassium iodide, and ammonium sulfate. When the indicator turns blue, the oxidation reaction has reached its endpoint, and the addition of hydrogen peroxide is stopped.

[0077] Continue stirring for 10 minutes, then filter, wash with water, and dry to obtain the rubber accelerator CBS product.

[0078] The tested CBS rubber accelerator product weighed 57.72g, with a yield of 89.2%, which was much lower than the yield in Example 1. The melting point was 97.4℃, and the purity, as determined by high performance liquid chromatography, was >97.7%. The quality of the CBS rubber accelerator product was inferior to that in Example 1.

[0079] Therefore, it can be seen that the present invention uses sodium hypochlorite to confirm the endpoint of the oxidation reaction, which is easier to observe and can stop the oxidation reaction in time, effectively preventing the over-oxidation of the target product. Moreover, the amount of sodium hypochlorite used is extremely small, and it will hardly cause waste salt to be generated. Furthermore, in the presence of potassium acetate, sodium hypochlorite can further promote the rapid combination of unbound cyclohexylamine free radicals and 2-mercaptobenzothiazole free radicals in the reaction system to generate CBS, generating more of the target product and improving the yield of the target product.

[0080] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the synthesis of rubber accelerator CBS by catalytic oxidation in solvent, characterized in that, The method comprises the following steps: S1, adding an ethanol solution into a reactor, then adding MBT, and stirring to make the MBT into a uniform slurry; S2, under stirring, adding cyclohexane dropwise into the reactor to react with the MBT, to prepare an MBT amine salt solution; S3, preparing a hydrogen peroxide solution, and adding potassium acetate into the solution to prepare a hydrogen peroxide solution containing a catalyst; the mass fraction of hydrogen peroxide in the hydrogen peroxide solution containing a catalyst is 7%-15%; the mass of potassium acetate added is 0.045‰-0.05‰ of the mass of MBT added in step S1; S4, under stirring, adding the hydrogen peroxide solution containing a catalyst into the MBT amine salt solution prepared in step S2; S5, after the addition of the hydrogen peroxide solution containing a catalyst is completed, using sodium hypochlorite to determine the end point of the oxidation reaction; S6, after determining that the reaction has reached the end point, continuing to stir for a period of time, and then filtering, washing with water, and drying the reaction product, to prepare rubber accelerator CBS.

2. The method according to claim 1, wherein the molar ratio of MBT, hydrogen peroxide, and cyclohexylamine is 1.0:(1.01-1.35):(1.8-2.9).

3. The method according to claim 2, wherein the molar ratio of MBT, hydrogen peroxide, and cyclohexylamine is 1.0:(1.05-1.10):(2.0-2.3).

4. The method according to any one of claims 1-3, wherein in step S1, the amount of ethanol used is 500 mL-1500 mL per mole of MBT in the reaction system, and the amount of water used is 100 mL-400 mL. Step S3, preparing a hydrogen peroxide solution, and adding potassium acetate into the solution to prepare a hydrogen peroxide solution containing a catalyst, specifically comprising the following steps: S31, adding water and a 30% hydrogen peroxide solution into a container provided with a stirrer, and stirring for 5 min; S32, adding potassium acetate into the above hydrogen peroxide solution, and continuing to stir for 5 min, to prepare a hydrogen peroxide solution containing a catalyst.

5. The process for the synthesis of rubber accelerator CBS by solvent process catalytic oxidation according to claim 1, characterized in that, 6. The method according to any one of claims 1-3, wherein in steps S4 and S5, the reaction temperature is 25°C-45°C. Step S5, after the addition of the hydrogen peroxide solution containing a catalyst is completed, using sodium hypochlorite to determine the end point of the oxidation reaction, specifically comprising the following steps: S51, after the addition of the hydrogen peroxide solution containing a catalyst is completed, continuing to stir for 10 min; S52, using a peristaltic pump to add sodium hypochlorite dropwise into the reaction solution; the mass fraction of sodium hypochlorite is 15.2%, the rotation speed of the peristaltic pump is 0.8 revolutions / min-20.0 revolutions / min, and the amount of sodium hypochlorite used is less than or equal to 0.9% of the total oxidizing agent, wherein the total oxidizing agent is the hydrogen peroxide and sodium hypochlorite added during the reaction; ​ 7. The process for the synthesis of rubber accelerator CBS by catalytic oxidation by solvents according to any one of claims 1 to 3, characterized in that, ​ ​ ​ S53, after adding sodium hypochlorite dropwise for 1 min, every 20 s, take a drop of reaction solution from the reaction system and drop it into the indicator on the drop plate, the indicator is a mixed solution of starch, potassium iodide and ammonium sulfate, if the indicator turns blue, stop adding sodium hypochlorite, and determine the reaction to the end point.

8. The method for synthesizing rubber accelerator CBS by catalytic oxidation according to any one of claims 1 to 3, characterized in that, In step S1, the stirring time is 30 min; In step S2, the stirring time is 30 min; In step S4, the solution containing the catalyst and hydrogen peroxide is added dropwise by using a peristaltic pump, and the rotation speed of the peristaltic pump is 1.0 revolutions / min-25.0 revolutions / min; In step S6, the stirring time is 10 min.