A method for continuous preparation of 4,4'-dithiodimorpholine

Abstract

The application belongs to the technical field of rubber additive synthesis, and particularly relates to a method for continuously preparing 4,4'-dithiodimorpholine. The method uses sulfur monochloride, morpholine, 32wt% liquid alkali (sodium hydroxide solution) and 120# solvent oil as raw materials, and generates 4,4'-dithiodimorpholine in a dynamic tubular reactor. After the reaction is completed, the material flowing out of the dynamic tubular reactor is collected, and the product is obtained through static layering, washing, filtering and drying. The method uses the dynamic tubular reactor for reaction, and the mass transfer and heat transfer efficiency are extremely high. The material is instantaneously and uniformly mixed, so that the morpholine and the sulfur monochloride are rapidly contacted and reacted, the reaction heat can be instantaneously removed, the optimal reaction temperature can be accurately maintained, the continuous production can be realized, the production capacity is greatly improved, the reaction time of the traditional kettle reactor is shortened from 2-7h to 10min, the raw material conversion rate is as high as 99% or more, and the goals of cost reduction and efficiency improvement, green safety are finally achieved.

Description

Technical Field

[0001] This invention belongs to the field of rubber additive synthesis technology, specifically relating to a method for the continuous preparation of 4,4'-dithiodimorpholine. Background Technology

[0002] 4,4'-Dithiodimorpholine (DTDM), an indispensable and highly efficient vulcanizing agent in the rubber industry, releases active sulfur from its disulfide bonds at vulcanization temperatures, achieving effective cross-linking. Compared to traditional vulcanizing agents, DTDM offers significant advantages such as safe operation, no blooming, no discoloration, and no pollution. Its vulcanized rubber products exhibit excellent resistance to heat and oxygen aging. Furthermore, the morpholine free radicals generated during the reaction also function as amine antioxidants and effectively delay scorching. Therefore, DTDM is widely used in high-value-added rubber products such as radial tires, engineering tires, and rubber seals, and can also be used as a stabilizer for highway asphalt. With the continuous growth in demand for high-performance materials from the rubber industry and related downstream industries, the market demand for DTDM is also constantly increasing.

[0003] Currently, the industrial production of DTDM mainly revolves around the condensation reaction of morpholine and sulfur monochloride. Since hydrogen chloride is generated during the reaction, an acid-binding agent must be introduced to prevent the deactivation of morpholine. Based on the type of acid-binding agent and the reaction system, the existing mainstream preparation processes can be divided into two categories: One approach is the liquid alkali process, which uses liquid sodium hydroxide as an acid-binding agent and conducts the reaction in an aqueous medium. A typical technique, as described in US Patent 2766236A, involves dissolving morpholine in a hydrocarbon fraction and then sequentially adding sulfur monochloride and 25% liquid alkali at 25-30°C, achieving a yield of 88.2%. Chinese Patent CN101121703A improves reaction efficiency by introducing a phase transfer catalyst and cross-adding alkali and sulfur monochloride at 30-60°C. Another approach is the anhydrous process, designed to avoid side reactions of sulfur monochloride in water. For example, Chinese Patent CN101402616A uses solvent oil as a medium and adds finely powdered solid sodium hydroxide for the reaction; while CN118388433A uses a mixture of sodium acetate, zeolite molecular sieves, and quinoline as an acid-binding agent, fundamentally eliminating the presence of free water and ensuring the stability of the reaction system.

[0004] Although the aforementioned traditional batch reactor process has been industrialized, its inherent technical shortcomings are becoming increasingly apparent, making it difficult to meet the demands of modern green chemical engineering and high-quality production. Firstly, the existing process is intermittent, with large online liquid hold-up and reaction times lasting several hours, resulting in low production efficiency and equipment turnover. Secondly, sulfur monochloride is chemically reactive and easily decomposes in water. In the traditional process, both water introduced from the liquid alkali system and water generated during the reaction can easily trigger side reactions, not only reducing product yield but also potentially causing localized corrosion or material spillage, posing a high operational hazard. Furthermore, the raw materials morpholine and sulfur monochloride are expensive. The existing process, due to numerous side reactions and complex post-processing procedures (involving multiple washing, filtration, and solvent recovery), results in raw material waste and increased energy consumption, leading to high overall production costs. In addition, the long reaction time makes the product quality stability susceptible to human error, resulting in poor controllability.

[0005] Therefore, there is an urgent need to develop a novel continuous DTDM preparation method to solve the technical problems existing in the current batch process, such as large online liquid hold-up, long reaction cycle, high operational risk, serious waste of raw material costs, and poor controllability of product quality. Summary of the Invention

[0006] The problem to be solved by the present invention is to provide a method for the continuous preparation of 4,4'-dithiodimorpholine, that is, to continuously produce rubber vulcanizing agent 4,4'-dithiodimorpholine using a dynamic tubular reactor, with short reaction time and high product selectivity and quality yield.

[0007] The technical solution adopted is as follows: A method for the continuous preparation of 4,4'-dithiodimorpholine includes the following steps: (1) The solvent phase A, the acid-binding agent phase B and morpholine are pumped into a dynamic tubular reactor respectively and mixed to form a homogeneous reaction system; (2) Sulfur monochloride is continuously pumped into a dynamic tubular reactor and mixed and reacted with the homogeneous reaction system in the dynamic tubular reactor to obtain the reaction effluent; (3) Collect the reaction effluent, let it stand to separate into layers, wash, filter and dry to obtain 4,4'-dithiodimorpholine product.

[0008] Preferably, the acid-binding agent B phase is solid sodium hydroxide, anhydrous trisodium phosphate, sodium acetate, or an aqueous solution of sodium hydroxide.

[0009] Preferably, the acid-binding agent B phase is a 32wt% sodium hydroxide solution; the solvent A phase is 120# solvent oil.

[0010] Preferably, the dynamic tubular reactor has a liquid holding capacity of 1000–1500 ml, a reaction temperature of 40–60 °C, and a residence time of 10–30 min.

[0011] Preferably, the molar ratio of sulfur monochloride, morpholine, and acid-binding agent is 1:2 to 2.3:2 to 2.4.

[0012] Preferably, the flow rate of solvent phase A is 30-100 ml / min, the flow rate of acid-binding agent phase B is 10-40 ml / min, the flow rate of morpholine is 8-30 ml / min, and the flow rate of monochloride is 4-15 ml / min.

[0013] Preferably, the reaction time is 10 to 90 minutes.

[0014] Preferably, the settling and stratification involves collecting the reaction effluent and allowing it to stand until the oil and water phases are completely separated. The washing process involves washing the separated organic phase with deionized water 2 to 3 times.

[0015] Preferably, the filtration is performed by depressurizing the washed material to remove residual moisture or trace solid impurities; the filtration is carried out using a Buchner funnel.

[0016] Preferably, the drying process involves drying the filtered cake in an oven or airflow dryer until it reaches a constant weight; the drying temperature is 50–80°C.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention is a method for the continuous preparation of DTDM using a dynamic tubular reactor. Sulfur monochloride, morpholine, 32wt% liquid alkali (sodium hydroxide solution), and 120# solvent oil are used as raw materials. The reaction produces DTDM in a dynamic tubular reactor. After the reaction, the material flowing out of the reactor is collected, separated, washed, filtered, and dried to obtain the product. This invention shortens the reaction time of the traditional batch reactor from 2-7 hours to 10 minutes, achieves a raw material conversion rate of over 99%, and ensures highly consistent product quality. It greatly improves reaction efficiency and reduces production costs, while maintaining inherent safety in the reaction process.

[0018] (2) The present invention uses a dynamic tubular reactor for reaction, which has extremely high mass and heat transfer efficiency, and the materials are mixed uniformly in an instant, so that morpholine and sulfur monochloride can react quickly. The heat of reaction can be removed instantly, the optimal reaction temperature can be maintained precisely, and continuous production can be achieved, greatly increasing the production capacity. It also has high automation and safety, and suppresses side reactions.

[0019] (3) The reaction system of the present invention uses inexpensive liquid alkali, with a very short residence time. The water in the system will not cause the hydrolysis of sulfur monochloride. Furthermore, the reaction of the reactants in the dynamic tubular reactor is thorough, resulting in high product selectivity and quality yield, and greatly reducing production costs.

[0020] (4) The method of the present invention can precisely control the reaction conditions, suppress side reactions, ensure that each reactant has the same experience, and maintain high consistency in the purity, melting point and other indicators of the product. It can greatly improve efficiency and product quality through continuous production, increase yield, and ultimately achieve the goals of cost reduction, efficiency improvement and green safety. It is suitable for widespread promotion. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the reaction process of the present invention.

[0022] In the diagram, 1-plunger pump A, 2-plunger pump B, 3-plunger pump C, 4-plunger pump D, 5-dynamic tubular reactor, 6-high and low temperature integrated unit. Detailed Implementation

[0023] The accompanying drawings are for illustrative purposes only; it should be understood that these embodiments are for illustrating the invention only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless specific conditions are specified, are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight.

[0024] The catalyst of the present invention and its water and acid resistance are further illustrated below with specific embodiments. Unless otherwise specified, the raw materials and chemical reagents used in this invention are all obtainable through legitimate commercial channels, and the standards for the chemical reagents are those commonly used in laboratories.

[0025] Example 1 like Figure 1 As shown, the instruments used in the preparation process of this invention include: a plunger pump, a dynamic tubular reactor, and a high-low temperature integrated system. The core function of the high-low temperature integrated system is to provide a precise and stable temperature environment for the reactor, accurately controlling the reaction temperature through a circulating heat transfer medium. The high-low temperature integrated system rapidly removes the heat of reaction through the circulating heat transfer medium, preventing the decomposition of sulfur monochloride due to local overheating, thereby improving product yield and purity; it can quickly remove the heat generated by the reaction, preventing local overheating or "runaway" phenomena and avoiding side reactions.

[0026] A method for the continuous preparation of 4,4'-dithiodimorpholine (DTDM) includes: The dynamic tubular reactor has a liquid holding capacity of 1500 ml, a reaction temperature of 55℃, a residence time of about 30 min, and a molar ratio of sulfur monochloride, morpholine, and acid-binding agent of 1:2:2.

[0027] Raw material A: Solvent phase A: 120# solvent oil, fed by plunger pump A; Raw material B: acid-binding agent phase B, 32wt% liquid alkali fed by plunger pump B; Raw material C: Morpholine, fed by plunger pump C; Raw material D: Sulfur monochloride, fed by plunger pump D.

[0028] The solutions were introduced into dynamic tubular reactors at flow rates of 33.4 ml / min for reactor A, 13 ml / min for reactor B, 9 ml / min for reactor C, and 4.4 ml / min for reactor D. The reaction mixture was collected after 1.5 hours. After the reaction was complete, the mixture was allowed to stand and separate into layers, washed, filtered, and dried to obtain the product.

[0029] The tested product has a melting point of 125-128℃ and a purity of 99.5% as determined by high performance liquid chromatography.

[0030] Example 2 A method for the continuous preparation of 4,4'-dithiodimorpholine (DTDM) includes: The dynamic reactor has a liquid holding capacity of 1000 ml, a reaction temperature of 60 ℃, a residence time of about 20 min, and a molar ratio of sulfur monochloride, morpholine, and acid-binding agent of 1:2.1:2.2.

[0031] The flow rates were 50 ml / min for A, 19.5 ml / min for B, 13.5 ml / min for C, and 6.6 ml / min for D. The reaction mixture was collected after 1 hour of reaction. After the reaction was completed, the mixture was allowed to stand for separation, washed, filtered, and dried to obtain the product.

[0032] The melting point was measured to be 126-128℃, and the purity was determined to be 99.6% by high performance liquid chromatography.

[0033] Other areas not mentioned are the same as in Example 1.

[0034] Example 3 A method for the continuous preparation of 4,4'-dithiodimorpholine (DTDM) includes: The dynamic reactor has a liquid holding capacity of 1200 ml, a reaction temperature of 65 ℃, a residence time of about 20 min, and a molar ratio of sulfur monochloride, morpholine, and acid-binding agent of 1:2.2:2.3.

[0035] The flow rates were 50 ml / min for A, 19.5 ml / min for B, 13.5 ml / min for C, and 6.6 ml / min for D. The reaction mixture was collected after 1 hour of reaction. After the reaction was completed, the mixture was allowed to stand for separation, washed, filtered, and dried to obtain the product.

[0036] The melting point was measured to be 126-128℃, and the purity was determined to be 99.6% by high performance liquid chromatography.

[0037] Other areas not mentioned are the same as in Example 1.

[0038] Example 4 A method for the continuous preparation of 4,4'-dithiodimorpholine (DTDM) includes: The dynamic reactor has a liquid holding capacity of 1500 ml, a reaction temperature of 65 ℃, a residence time of about 15 min, and a molar ratio of sulfur monochloride, morpholine, and acid-binding agent of 1:2.3:2.4.

[0039] The flow rates were 66.8 ml / min for A, 26 ml / min for B, 18 ml / min for C, and 8.8 ml / min for D. The reaction mixture was collected after 45 minutes. After the reaction was complete, the mixture was allowed to stand for separation, washed, filtered, and dried to obtain the product.

[0040] The melting point was measured to be 125-128℃, and the purity was determined to be 99.6% by high performance liquid chromatography.

[0041] Other areas not mentioned are the same as in Example 1.

[0042] Example 5 A method for the continuous preparation of 4,4'-dithiodimorpholine (DTDM) includes: The dynamic reactor has a liquid holding capacity of 1500 ml, a reaction temperature of 65 ℃, a residence time of about 10 min, and a molar ratio of sulfur monochloride, morpholine, and acid-binding agent of 1:2.3:2.4.

[0043] The flow rates were 100 ml / min for A, 39 ml / min for B, 27 ml / min for C, and 13.2 ml / min for D. The reaction mixture was collected after 30 minutes of reaction. After the reaction was completed, the mixture was allowed to stand for separation, washed, filtered, and dried to obtain the product.

[0044] The melting point was measured to be 126-128℃, and the purity was determined to be 99.7% by high performance liquid chromatography.

[0045] Other areas not mentioned are the same as in Example 1.

[0046] As illustrated by the above embodiments, the preparation process of the present invention is simple, the reaction time is short when the material flow rate is high, and the prepared product has high purity.

[0047] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for the continuous preparation of 4,4'-dithiodimorpholine, characterized in that, Includes the following steps: (1) The solvent phase A, the acid-binding agent phase B and morpholine are pumped into a dynamic tubular reactor respectively and mixed to form a homogeneous reaction system; (2) Sulfur monochloride is continuously pumped into a dynamic tubular reactor and mixed and reacted with the homogeneous reaction system in the dynamic tubular reactor to obtain the reaction effluent; (3) Collect the reaction effluent, let it stand to separate into layers, wash, filter and dry to obtain 4,4'-dithiodimorpholine product.

2. The method for continuous preparation of 4,4'-dithiodimorpholine according to claim 1, characterized in that, The acid-binding agent B phase is solid sodium hydroxide, anhydrous trisodium phosphate, sodium acetate, or an aqueous solution of sodium hydroxide.

3. The method for continuous preparation of 4,4'-dithiodimorpholine according to claim 2, characterized in that, The acid-binding agent B phase is a 32wt% sodium hydroxide solution; the solvent A phase is 120# solvent oil.

4. The method for continuous preparation of 4,4'-dithiodimorpholine according to claim 1, characterized in that, The dynamic tubular reactor has a liquid holding capacity of 1000–1500 ml, a reaction temperature of 40–60 °C, and a residence time of 10–30 min.

5. The method for continuous preparation of 4,4'-dithiodimorpholine according to claim 1, characterized in that, The molar ratio of sulfur monochloride, morpholine, and acid-binding agent is 1:2 to 2.3:2 to 2.

4.

6. The method for continuous preparation of 4,4'-dithiodimorpholine according to claim 1, characterized in that, The flow rate of solvent phase A is 30–100 ml / min, the flow rate of acid-binding agent phase B is 10–40 ml / min, the flow rate of morpholine is 8–30 ml / min, and the flow rate of monochloride is 4–15 ml / min.

7. The method for continuous preparation of 4,4'-dithiodimorpholine according to claim 1, characterized in that, The reaction time is 10–90 min.

8. The method for continuous preparation of 4,4'-dithiodimorpholine according to claim 1, characterized in that, The step-by-step separation process involves collecting the reaction effluent and allowing it to stand until the oil and water phases are completely separated. The washing process involves washing the separated organic phase with deionized water 2 to 3 times.

9. The method for continuous preparation of 4,4'-dithiodimorpholine according to claim 1, characterized in that, The aforementioned filtration involves depressurizing the washed material to remove residual moisture or trace solid impurities; the filtration process utilizes a Buchner funnel.

10. The method for continuous preparation of 4,4'-dithiodimorpholine according to claim 1, characterized in that, The drying process involves drying the filtered cake in an oven or airflow dryer until it reaches a constant weight; the drying temperature is 50–80°C.

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