阅读说明：本技术 一种橡胶硫化促进剂二硫化二苯并噻唑的绿色合成方法 (Green synthesis method of rubber vulcanization accelerator dibenzothiazyl disulfide ) 是由 骆广生 田佳鑫 王凯 于 2019-10-14 设计创作，主要内容包括：本发明公开了属于化学化工技术领域的一种橡胶硫化促进剂二硫化二苯并噻唑的绿色合成方法。具体为将2-巯基苯并噻唑完全溶解于碳酸钠水溶液中,然后滴加双氧水,并通入二氧化碳调节体系pH,氧化生成二硫化二苯并噻唑和碳酸氢钠。所得碳酸氢钠溶液经加热形成的碳酸钠溶液,能用于溶解原料2-巯基苯并噻唑从而实现原料的循环。本发明方法制备的产品纯度可达99％以上,与传统混酸氧化法相比,减少了含盐废水的大量产生,过程更加绿色环保。(The invention discloses a green synthesis method of a rubber vulcanization accelerator dibenzothiazyl disulfide, belonging to the technical field of chemistry and chemical engineering. The method specifically comprises the steps of completely dissolving 2-mercaptobenzothiazole into a sodium carbonate aqueous solution, then dropwise adding hydrogen peroxide, introducing carbon dioxide to adjust the pH value of a system, and oxidizing to generate dibenzothiazyl disulfide and sodium bicarbonate. The sodium carbonate solution formed by heating the obtained sodium bicarbonate solution can be used for dissolving the raw material 2-mercaptobenzothiazole, thereby realizing the circulation of the raw material. The purity of the product prepared by the method can reach more than 99 percent, and compared with the traditional mixed acid oxidation method, the method reduces the generation of a large amount of salt-containing wastewater, and the process is more green and environment-friendly.)

1. A green synthesis method of a rubber vulcanization accelerator dibenzothiazyl disulfide is characterized by comprising the following steps:

(1) adding 2-mercaptobenzothiazole into a sodium carbonate aqueous solution, and heating until the 2-mercaptobenzothiazole is completely dissolved to obtain a solution A containing 2-mercaptobenzothiazole sodium;

(2) dropwise adding hydrogen peroxide into the solution A obtained in the step (1), adjusting the pH value of the solution to 5-10, carrying out oxidation reaction, and obtaining a sodium bicarbonate solution B containing dibenzothiazyl disulfide solid after reaction;

(3) filtering the solution B obtained in the step (2), and washing and drying the obtained solid to obtain dibenzothiazyl disulfide;

(4) and (4) heating the filtrate obtained in the step (3) to release carbon dioxide to obtain a sodium carbonate solution, circularly using the sodium carbonate solution as an alkali liquor in the step (1) to dissolve the 2-mercaptobenzothiazole, and repeating the steps (2) to (3) to prepare the dibenzothiazyl disulfide.

2. The method according to claim 1, wherein the molar ratio of the 2-mercaptobenzothiazole to the sodium carbonate in the step (1) is 1: 1-1: 10, and the mass fraction of the sodium carbonate in the sodium carbonate aqueous solution is 10-20%.

3. The method according to claim 1, wherein the heating temperature in the step (1) is 20 to 90 ℃.

4. The method according to claim 1, wherein the mass fraction of the sodium 2-mercaptobenzothiazole in the solution A in the step (1) is 3 to 30 percent.

5. The method according to claim 1, wherein the mass fraction of hydrogen peroxide in the step (2) is 1-30%, and the molar ratio of the hydrogen peroxide to the 2-mercaptobenzothiazole sodium in the solution A is 0.4: 1-0.6: 1.

6. The method according to claim 1, wherein the oxidation reaction temperature in the step (2) is 10 to 70 ℃.

7. The method according to claim 1, wherein the pH of the solution in the step (2) is adjusted by using carbon dioxide.

8. The method according to claim 1, wherein the sodium carbonate solution obtained by heating the filtrate in the step (3) to release carbon dioxide is recycled as an alkali solution for dissolving 2-mercaptobenzothiazole, and can be recycled for more than 5 times.

9. The method according to claim 1, wherein the solid obtained by filtering in the step (3) is washed by water and dried at 80-120 ℃ to obtain the dibenzothiazyl disulfide.

Technical Field

The invention belongs to the technical field of chemistry and chemical engineering, and particularly relates to a green synthesis method of a rubber vulcanization accelerator dibenzothiazyl disulfide.

Background

Dibenzothiazyl disulfide is a versatile type of rubber vulcanization accelerator. The vulcanization curve of the vulcanization process is flat, and the vulcanization critical temperature is higher. The benzothiazolyl contained in the structure belongs to a promoting group, the disulfide bond belongs to a scorch-proof group, and the compound has good aging resistance and is usually used together with other promoters to further improve the activity. The bitter taste is mainly used for manufacturing rubber products for non-food applications such as tires, rubber shoes and the like. Dibenzothiazyl disulfide is mainly prepared by using 2-mercaptobenzothiazole as a raw material and oxidizing the dibenzothiazyl disulfide by using different oxidants.

The most conventional method in industry is the sodium nitrite method. As shown in formula 1, sulfuric acid is dripped into slurry of 2-mercaptobenzothiazole and sodium nitrite, air is introduced in the presence of nitric oxide, and an oxidation reaction is carried out at 60 ℃. The method has the problems that a large amount of salt-containing wastewater is generated in the reaction, and the treatment is difficult; nitrogen oxide tail gas is generated, and air is seriously polluted; in addition, sodium nitrite is a strong carcinogen and is harmful to human health.

U.S. Pat. No. 3, 4482720,897,893,78 reports that 2-mercaptobenzothiazole is firstly dissolved in NaOH solution to generate 2-mercaptobenzothiazole sodium salt solution, and then chlorine diluted by a large amount of air is introduced into the solution to carry out oxidation reaction to obtain the product, as shown in formula 2. The method is easy to produce by-products, and excessive chlorine gas participates in the reaction to generate peroxides such as sulfonate, sulfoxide and the like.

Patent CS 393386(A1) discloses a method for direct oxidation by a solvent method, which comprises the steps of directly dissolving 2-mercaptobenzothiazole by using an isopropanol aqueous solution as a solvent, and then slowly dropwise adding hydrogen peroxide as an oxidizing agent for reaction to obtain a product, wherein the formula is shown in formula 3. The method has the advantages of high solvent cost and great potential safety hazard.

The prior method has the problems of toxic and harmful reaction process, low product yield and purity, high environmental protection treatment cost and the like, so that the invention provides a clean and green synthesis process with recyclable mother liquor aiming at the product dibenzothiazyl disulfide.

Disclosure of Invention

The invention aims to provide a green synthesis method of a rubber vulcanization accelerator dibenzothiazyl disulfide, which has the following specific technical scheme:

a green synthesis method of a rubber vulcanization accelerator dibenzothiazyl disulfide comprises the following steps:

(1) adding 2-mercaptobenzothiazole into a sodium carbonate aqueous solution, and heating until the 2-mercaptobenzothiazole is completely dissolved to obtain a solution A containing 2-mercaptobenzothiazole sodium;

(2) dropwise adding hydrogen peroxide into the solution A obtained in the step (1), adjusting the pH value of the solution to 5-10, carrying out oxidation reaction, and obtaining a sodium bicarbonate solution B containing dibenzothiazyl disulfide solid after reaction;

(3) filtering the solution B obtained in the step (2), and washing and drying the obtained solid to obtain dibenzothiazyl disulfide;

(4) and (4) heating the filtrate obtained in the step (3) to release carbon dioxide to obtain a sodium carbonate solution, circularly using the sodium carbonate solution as an alkali liquor in the step (1) to dissolve the 2-mercaptobenzothiazole, and repeating the steps (2) to (3) to prepare the dibenzothiazyl disulfide.

In the step (1), the molar ratio of the 2-mercaptobenzothiazole to the sodium carbonate is 1: 1-1: 10, and the mass fraction of the sodium carbonate in the sodium carbonate aqueous solution is 10-20%.

The heating temperature in the step (1) is 20-90 ℃.

The mass fraction of the 2-mercaptobenzothiazole sodium in the solution A in the step (1) is 3-30%.

In the step (2), the mass fraction of hydrogen peroxide in the hydrogen peroxide is 1-30%, and the molar ratio of the hydrogen peroxide to the 2-mercaptobenzothiazole sodium in the solution A is 0.4: 1-0.6: 1.

And (3) the oxidation reaction temperature in the step (2) is 10-70 ℃.

And (3) adjusting the pH value of the solution in the step (2) by using carbon dioxide.

And (3) heating the filtrate in the step (3) to release carbon dioxide to obtain a sodium carbonate solution which is used as an alkali liquor to be recycled for dissolving the 2-mercaptobenzothiazole, and the sodium carbonate solution can be recycled for more than 5 times.

And (4) washing the solid obtained by filtering in the step (3) with water, and drying at 80-120 ℃ to obtain the dibenzothiazyl disulfide.

The invention has the beneficial effects that:

(1) the invention uses sodium carbonate as alkali liquor to dissolve 2-mercaptobenzothiazole to form sodium salt, and uses CO₂The auxiliary hydrogen peroxide oxidation processAnd carrying out reaction. Compared with the prior oxidation technology, the sodium bicarbonate aqueous solution formed after the oxidation reaction can form the sodium carbonate aqueous solution after being heated, can be recycled, and does not generate Na₂SO₄Waste salt such as NaCl can greatly reduce the generation of salt-containing wastewater, the generation of about 0.5 ton of salt-containing wastewater in each ton of products is reduced, and the process environmental-friendly treatment cost is reduced;

(2) the invention takes carbon dioxide as an acidifying agent to adjust the pH of a reaction system, is milder compared with other acid-base regulators, can reduce the precipitation of insoluble 2-mercaptobenzothiazole in the acidification process, further protects the reaction system from easily generating peroxidation, and has the product yield of more than 98 percent and the purity of more than 99 percent.

(3) The sodium carbonate-sodium bicarbonate in the solution has a certain buffering effect on the pH value of the system in the reaction process, and avoids the generation of peroxidation byproducts in a weakly alkaline state.

Detailed Description

The invention provides a green synthesis method of rubber vulcanization accelerator dibenzothiazyl disulfide, which is further illustrated by combining the following examples.

The invention provides a green synthesis method of rubber vulcanization accelerator dibenzothiazyl disulfide, which has the following reaction formula:

as shown in formula 4, sodium carbonate is used as alkali liquor to dissolve 2-mercaptobenzothiazole, and the 2-mercaptobenzothiazole reacts with the sodium carbonate to form 2-mercaptobenzothiazole sodium and sodium bicarbonate; as shown in formula 5, slowly dropwise adding hydrogen peroxide into a water phase to perform an oxidation reaction, adjusting the pH value of the system by using carbon dioxide, and oxidizing 2-mercaptobenzothiazole sodium by using hydrogen peroxide to form dibenzothiazyl disulfide and sodium bicarbonate; wherein the generated sodium bicarbonate is heated to release carbon dioxide to obtain a sodium carbonate solution which can be recycled for use in formula 4 to dissolve 2-mercaptobenzothiazole for continuously preparing dibenzothiazyl disulfide.