A kind of synthetic method of dicyclohexyl disulfide

Abstract

The invention discloses a method for synthesizing dicyclohexyl disulfide, wherein chlorocyclohexane, sodium sulfide and sulfur are used as raw materials, and dicyclohexyl disulfide is obtained by reaction under a phase transfer catalyst and a controlled system pH. The invention shortens the reaction time, reduces the occurrence of side reactions, avoids the situation of greatly excessive materials, improves the raw material conversion rate, greatly reduces the generation of side products, is simple in post-processing, and the yield of the target product can reach more than 95%, and the purity can reach more than 99%, which meets the use requirements.

Description

Technical Field

[0001] The invention relates to a method for synthesizing dicyclohexyl disulfide (scorch inhibitor CTP intermediate), and in particular to a method for synthesizing dicyclohexyl disulfide with short reaction time, high conversion rate and small amount of raw materials, belonging to the technical field of rubber additive synthesis. Background Art

[0002] Rubber is currently widely used in our daily life, medical industry, rail transportation industry and other industries, and plays an irreplaceable role in people's lives. Rubber anti-scorch agent CTP is an indispensable additive to prevent scorch behavior in the current rubber industry. The use of anti-scorch agent CTP can achieve the sealed mixing of rubber in rubber production, prolong the scorch time, and at the same time does not hinder the normal functioning of the vulcanization accelerator; when the rubber is calendered or vulcanized, the system temperature can be increased, thereby improving the rubber processing production efficiency.

[0003] As a key intermediate of the anti-scorch agent CTP, the synthesis process of dicyclohexyl disulfide has the following shortcomings: 1. There is a problem of long reaction time in the synthesis process, which often takes 12 hours or longer, greatly reducing production efficiency and limiting production capacity. 2. In order to improve the product yield, the current process method often adopts a method of greatly excessive use of a certain raw material, which not only causes waste of raw materials and increases costs, but also leads to complicated post-processing processes. 3. Since the reaction of chlorocyclohexane and disodium disulfide is a nucleophilic substitution reaction, it is accompanied by an elimination reaction, resulting in a conversion rate of the target product dicyclohexyl disulfide of about 80%, accompanied by the production of by-product cyclohexene, and the product yield is low. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for synthesizing dicyclohexyl disulfide. The method uses sodium sulfide, sulfur and chlorocyclohexane as main raw materials, reduces the waste of raw materials, reduces the generation of side reactions, greatly shortens the reaction time, improves the product conversion rate, and has obvious economic benefits by using a phase transfer catalyst and controlling the pH value of the system and the addition method of chlorocyclohexane.

[0005] The present invention uses sodium sulfide, sulfur and chlorocyclohexane as raw materials, and the reaction equation is as follows:

[0006]

[0007] The synthetic method of dicyclohexyl disulfide of the present invention comprises the following steps:

[0008] (1) mixing sodium sulfide, sulfur and water to react and obtain a sodium disulfide solution;

[0009] (2) adding a phase transfer catalyst to the sodium disulfide solution of step (1) above, adjusting the pH of the system to 11-13, then dripping the sodium disulfide solution into chlorocyclohexane, and carrying out a heat-insulating reaction after the dripping is completed;

[0010] (3) After the reaction, post-treatment is performed to obtain dicyclohexyl disulfide.

[0011] Furthermore, the molar ratio of chlorocyclohexane, sodium sulfide and sulfur is 2: 1.0-1.1: 1.0-1.1. The amount of raw materials used is close to the theoretical molar amount, thus avoiding the waste of raw materials.

[0012] Furthermore, in step (1), the temperature is controlled to be 50-90° C., and sodium disulfide is obtained by reaction, for example, 50° C., 60° C., 70° C., 80° C., 90° C. The reaction time is generally 0.5-2 h.

[0013] Furthermore, in step (2), the phase transfer catalyst brings the sulfur anions in the sodium disulfide into the chlorocyclohexane, the sulfur anions react with the chlorocyclohexane to remove the chloride ions, and the chloride ions react with the sodium ions in the sodium disulfide to generate sodium chloride, and the introduction of the phase transfer catalyst accelerates the reaction process. The phase transfer catalyst is one of benzyltriethylammonium chloride (TEBA), tetrabutylammonium bromide (TBAB), tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, and tetradecyltrimethylammonium chloride, preferably tetrabutylammonium bromide.

[0014] Furthermore, in step (2), the amount of the phase transfer catalyst used is 1%-3% of the mass of the chlorocyclohexane.

[0015] Furthermore, in step (2), the pH of the entire system is maintained between 11 and 13. In this pH range, the occurrence of side reactions is reduced and the product conversion rate is improved. Preferably, the pH of the system is maintained at 12. The pH of the entire system can be maintained within a specified range by adding a buffer, wherein the buffer is one of sodium dihydrogen phosphate-disodium hydrogen phosphate buffer, acetic acid-sodium acetate buffer, sodium dihydrogen carbonate-disodium bicarbonate buffer, and citric acid-sodium citrate buffer, preferably sodium dihydrogen phosphate-disodium hydrogen phosphate buffer.

[0016] Furthermore, in step (2), the sodium disulfide solution is added dropwise for 0.5-1 h.

[0017] Furthermore, in step (2), the temperature of the solution containing sodium disulfide added dropwise and the insulation temperature after the addition are both 80-120°C, for example, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C.

[0018] Furthermore, in step (2), after the sodium disulfide-containing solution is added dropwise, the reaction is kept warm for 2-4 hours, for example, 2 hours, 3 hours, or 4 hours.

[0019] Furthermore, in step (3), the post-treatment process is as follows: after the reaction is completed, the layers are separated, the lower layer is a salt solution, and the upper layer is a crude product. The upper layer crude product is distilled and purified to obtain dicyclohexyl disulfide.

[0020] The present invention has the following advantages:

[0021] 1. The synthesis process of the present invention is simple, fast, and highly operable, greatly shortens the reaction time, reduces the time cost, avoids a large excess of materials, and improves the raw material conversion rate. The reverse dripping method is innovatively adopted to drip the solution containing sodium disulfide into chlorocyclohexane, so that chlorocyclohexane and sodium disulfide are more fully contacted and reacted, greatly reducing the generation of by-products, and the post-treatment process is simple, the economic benefit is high, and the product has industrial application value.

[0022] 2. The present invention uses a buffer solution to control the pH of the system during the reaction process, which greatly reduces the occurrence of side reactions and improves the yield and purity of the product.

[0023] 3. The target product of the present invention has high conversion rate, high product yield and high purity. The yield can reach up to more than 95%, and the purity can reach up to more than 99%, which meets the use requirements. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments, but the following embodiments are merely illustrative and do not limit the contents thereof.

[0025] In the following examples, the yield is calculated as follows: mass of product obtained / theoretical mass of product. Example 1

[0026] Add 260g of water, 82.9g of sodium sulfide, and 34g of sulfur to a 1L reactor, control the temperature to 80°C, start stirring to react, and after 2h of reaction, the sodium disulfide solution is completely reacted, add 2g of tetrabutylammonium bromide, and add sodium dihydrogen phosphate-disodium hydrogen phosphate buffer with a pH of 5 to adjust the system pH to 12 to obtain a mixed solution containing sodium disulfide;

[0027] Slowly add the mixed solution containing sodium disulfide to 120g of chlorocyclohexane for 1h. The dropping time is controlled at 90°C. After the dropping is completed, keep warm for 2.5h. After the reaction is completed, separate the liquids, the lower layer is the salt solution, and the upper layer is the crude product. The upper layer of the crude product is distilled to obtain 113.8g of light yellow transparent liquid, which is dicyclohexyl disulfide. The yield is 97.68% and the product purity is 99.42%. Example 2

[0028] Add 260g of water, 82.9g of sodium sulfide, and 34g of sulfur to a 1L reactor, control the temperature to 80°C, start stirring to react, and after 2h of reaction, the sodium disulfide solution is completely reacted, add 3.6g of tetrabutylammonium bromide, and add sodium dihydrogen phosphate-disodium hydrogen phosphate buffer with a pH of 5 to adjust the system pH to 12 to obtain a mixed solution containing sodium disulfide;

[0029] Slowly add the mixed solution containing sodium disulfide to 120g of chlorocyclohexane for 0.5h. The dropping temperature is controlled to 90°C. After the dropping is completed, keep warm for 3h. After the reaction is completed, separate the liquids, the lower layer is the salt solution, and the upper layer is the crude product. The upper layer of the crude product is distilled to obtain 112.6g of light yellow transparent liquid, which is dicyclohexyl disulfide. The yield is 96.65% and the product purity is 99.12%. Example 3

[0030] Add 260g of water, 82.9g of sodium sulfide, and 34g of sulfur to a 1L reactor, control the temperature to 80°C, start stirring to react, and after 1.5h of reaction, the sodium disulfide solution is completely reacted, add 2g of tetrabutylammonium bromide, and add sodium dihydrogen phosphate-disodium hydrogen phosphate buffer with a pH of 5 to adjust the system pH to 12 to obtain a mixed solution containing sodium disulfide;

[0031] Slowly add the mixed solution containing sodium disulfide to 120g of chlorocyclohexane for 0.5h. The dropping temperature is controlled to 90°C. After the dropping is completed, keep warm for 2h. After the reaction is completed, separate the liquids, the lower layer is the salt solution, and the upper layer is the crude product. The upper layer of the crude product is distilled to obtain 111.6g of light yellow transparent liquid, which is dicyclohexyl disulfide. The yield is 95.78% and the product purity is 99.04%. Example 4

[0032] Add 260g of water, 82.9g of sodium sulfide, and 34g of sulfur to a 1L reactor, control the temperature to 80°C, start stirring to react, and after 2h of reaction, the sodium disulfide solution is completely reacted, add 3.6g of tetrabutylammonium bromide, and add sodium dihydrogen phosphate-disodium hydrogen phosphate buffer with a pH of 5 to adjust the system pH to 12 to obtain a mixed solution containing sodium disulfide;

[0033] Slowly add the mixed solution containing sodium disulfide to 120g of chlorocyclohexane for 0.5h. The dropping temperature is controlled to 90°C. After the dropping is completed, keep warm for 2.5h. After the reaction is completed, separate the liquids, the lower layer is the salt solution, and the upper layer is the crude product. The upper layer of the crude product is distilled to obtain 113.2g of light yellow transparent liquid, which is dicyclohexyl disulfide. The yield is 97.15% and the product purity is 99.33%. Example 5

[0034] Add 260g of water, 82.9g of sodium sulfide, and 34g of sulfur to a 1L reactor, control the temperature to 80°C, start stirring to react, and after 2h of reaction, the sodium disulfide solution is completely reacted, add 2g of tetrabutylammonium chloride, and add sodium dihydrogen phosphate-disodium hydrogen phosphate buffer with a pH of 5 to adjust the system pH to 12 to obtain a mixed solution containing sodium disulfide;

[0035] Slowly add the mixed solution containing sodium disulfide to 120g of chlorocyclohexane for 0.5h. The dropping temperature is controlled to 90°C. After the dropping is completed, keep warm for 2.5h. After the reaction is completed, separate the liquids, the lower layer is the salt solution, and the upper layer is the crude product. The upper layer of the crude product is distilled to obtain 111.4g of light yellow transparent liquid, which is dicyclohexyl disulfide. The yield is 95.62% and the product purity is 99.17%. Example 6

[0036] Dicyclohexyl disulfide was synthesized according to the method of Example 1, except that an acetic acid-sodium acetate buffer solution with a pH of 5 was selected as the buffer solution, and the pH was controlled to be 12. The obtained product had an appearance of a light yellow transparent liquid, a yield of 91.35%, and a product purity of 92.47%. Example 7

[0037] Dicyclohexyl disulfide was synthesized according to the method of Example 1, except that a sodium dihydrogen carbonate acid-sodium bicarbonate buffer solution with a pH of 5 was selected as the buffer solution, and the pH was controlled to be 12. The obtained product had an appearance of light yellow transparent liquid, a yield of 89.52%, and a product purity of 94.58%. Example 8

[0038] Dicyclohexyl disulfide was synthesized according to the method of Example 1, except that a citric acid-sodium citrate buffer solution with a pH of 5 was selected as the buffer solution, and the pH was controlled to be 12. The obtained product had an appearance of a light yellow transparent liquid, a yield of 90.42%, and a product purity of 93.21%. Example 9

[0039] Dicyclohexyl disulfide was synthesized according to the method of Example 1, except that a sodium dihydrogen phosphate-disodium hydrogen phosphate buffer with a pH of 4.5 was selected to adjust the system pH to 11. The obtained product had a light yellow transparent liquid appearance, a yield of 96.74%, and a product purity of 99.23%. Example 10

[0040] Dicyclohexyl disulfide was synthesized according to the method of Example 1, except that a sodium dihydrogen phosphate-disodium hydrogen phosphate buffer with a pH of 6 was selected to adjust the system pH to 13. The obtained product had a light yellow transparent liquid appearance, a yield of 97.02%, and a product purity of 99.14%. Embodiment 11

[0041] Add 260g of water, 82.9g of sodium sulfide, and 34g of sulfur to a 1L reactor, control the temperature to 50°C, start stirring to react, and after 2h of reaction, the sodium disulfide solution is completely reacted, add 2g of trioctylmethylammonium chloride, and add sodium dihydrogen phosphate-disodium hydrogen phosphate buffer with a pH of 5 to adjust the system pH to 12 to obtain a mixed solution containing sodium disulfide;

[0042] Slowly add the mixed solution containing sodium disulfide to 120g of chlorocyclohexane for 1h. The dropping time is controlled at 120°C. After the dropping is completed, keep warm for 2h. After the reaction is completed, separate the liquids, the lower layer is the salt solution, and the upper layer is the crude product. The upper layer of the crude product is distilled to obtain 106.2g of light yellow transparent liquid, which is dicyclohexyl disulfide. The yield is 91.16% and the product purity is 95.23%.

[0043] Comparative Example 1

[0044] Dicyclohexyl disulfide was synthesized according to the method of Example 1, except that the pH of the system was adjusted to 14. The obtained product had a pale yellow transparent liquid appearance, a yield of 87.45%, and a product purity of 90.52%.

[0045] Comparative Example 2

[0046] Dicyclohexyl disulfide was synthesized according to the method of Example 1, except that tetrabutylammonium bromide was not added. The obtained product had an appearance of light yellow transparent liquid, a yield of 83.35%, and a product purity of 87.52%.

[0047] Comparative Example 3

[0048] Dicyclohexyl disulfide was synthesized according to the method of Example 1, except that the reaction temperature of disodium disulfide was 120° C. The obtained product had a pale yellow transparent liquid appearance, a yield of 80.23%, and a product purity of 85.46%.

[0049] Comparative Example 4

[0050] Dicyclohexyl disulfide was synthesized according to the method of Example 1, except that 120 g of chlorocyclohexane was slowly added to the mixed solution containing sodium disulfide in a forward dropping manner, the dropping time was 0.5 h, the dropping temperature was controlled to be 90° C., and the reaction was kept warm for 2.5 h after the dropping was completed. The appearance of the obtained product was a light yellow transparent liquid, the yield was 85.23%, and the product purity was 83.54%.

Claims

1. A method for synthesizing dicyclohexyl disulfide, characterized in that The following steps are involved: (1) mixing sodium sulfide, sulfur and water to obtain a sodium disulfide solution; (2) adding a phase transfer catalyst to the sodium disulfide solution of step (1), adjusting the pH of the system to 11-13 with a buffer solution, then dropping the sodium disulfide solution into chlorocyclohexane, and performing a heat-insulating reaction after the dropwise addition is completed; (3) performing post-treatment after the reaction to obtain dicyclohexyl disulfide; The molar ratio of chlorocyclohexane, sodium sulfide and sulfur is 2:1.0-1.1:1.0-1.1; The buffer is one of sodium dihydrogen phosphate-disodium hydrogen phosphate buffer, acetic acid-sodium acetate buffer, sodium dihydrogen carbonate-disodium bicarbonate buffer, and citric acid-sodium citrate buffer.

2. The synthesis method according to claim 1, characterized in that: In step (2), the pH of the system is 12.

3. The synthesis method according to claim 1 or 2, characterized in that: In step (2), the buffer is sodium dihydrogen phosphate-disodium hydrogen phosphate buffer.

4. The synthesis method according to claim 1 or 2, characterized in that: In step (2), the phase transfer catalyst is one of benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, and tetradecyltrimethylammonium chloride.

5. The synthesis method according to claim 4, characterized in that: In step (2), the phase transfer catalyst is tetrabutylammonium bromide.

6. The synthesis method according to claim 4, characterized in that: In step (2), the amount of the phase transfer catalyst used is 1%-3% of the mass of the chlorocyclohexane.

7. The synthesis method according to claim 1 or 2, characterized in that: In step (2), the dropwise addition time of the solution containing sodium disulfide is 0.5-1h.

8. The synthesis method according to claim 1, characterized in that: In step (2), the temperature of the solution containing sodium disulfide added dropwise and the insulation temperature after the addition are both 80-120°C.

9. The synthesis method according to claim 1, characterized in that: In step (2), after the sodium disulfide solution is added dropwise, the reaction is kept warm for 2-4 hours.

10. The synthesis method according to claim 1, characterized in that: In step (1), the temperature is controlled at 50-90° C. to obtain sodium disulfide.

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