Safe and efficient synthesis process of o-p-toluenesulfonamide

Abstract

This invention relates to the field of fine chemical technology and discloses a safe and efficient synthesis process for o-p-toluenesulfonamide. The process uses p-toluenesulfonyl chloride and ammonia as raw materials, and tetrabutylammonium bromide as a phase transfer catalyst. In an acetone-water mixed solvent, an amination reaction is carried out in a continuous flow pipeline reactor to generate p-toluenesulfonamide in one step. After continuous extraction and separation in a countercurrent extraction tower, the organic phase is continuously recovered from dichloromethane and acetone via thin-film evaporation and recycled. The crude product is then purified by gradient vacuum distillation to obtain high-purity p-toluenesulfonamide. The aqueous phase is stripped to recover excess ammonia and reused. Wastewater is treated biochemically to meet discharge standards, and solid waste is incinerated for resource utilization. By employing continuous extraction and solvent recovery technologies, the consumption of organic solvents is significantly reduced and recycling is achieved. Simultaneously, gradient distillation instead of recrystallization avoids the generation of saline organic wastewater, thereby reducing wastewater discharge and achieving environmentally friendly production.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a safe and efficient synthesis process for o-toluenesulfonamide. Background Technology

[0002] o-p-Toluenesulfonamide is an important fine chemical intermediate widely used in organic synthesis, dyes, plastics, rubber, and pharmaceuticals. Currently, the industrial production of o-p-toluenesulfonamide mainly adopts the traditional batch reactor synthesis process, which uses p-toluenesulfonyl chloride and ammonia as raw materials, carries out an amination reaction in an organic solvent, and then obtains the finished product through extraction, decolorization, crystallization, centrifugation, and drying. However, the traditional process has the following technical defects: (1) long reaction time, usually 2-4 hours, resulting in low production efficiency; (2) batch operation leads to unstable product quality between batches, many side reactions, and a product yield of only 85%-90%; (3) recrystallization purification generates a large amount of saline organic wastewater, resulting in high environmental treatment costs; (4) large solvent consumption, and it is difficult to effectively recycle and reuse it; (5) concentrated exothermic reaction process, posing safety hazards such as local overheating and material spraying. In view of the above problems, developing a safe, efficient, green and environmentally friendly o-p-toluenesulfonamide synthesis process has important industrial application value. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a safe and efficient synthesis process for o-p-toluenesulfonamide, which has the advantages of short reaction time, high product yield, good purity, recyclable solvent, and low emissions of waste. It solves the problems of low reaction efficiency, unstable product quality, high environmental pressure, and poor safety of traditional batch reactor processes.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a safe and efficient synthesis process for o- and p-toluenesulfonamides, comprising the following steps: Step 1: Raw material preparation: Select p-toluenesulfonyl chloride, ammonia, acetone, tetrabutylammonium bromide and dichloromethane extractant as raw materials; Step 2, Raw material pretreatment: p-Toluenesulfonyl chloride is vacuum dried, and reaction solvent and catalyst solution are prepared; Step 3, Continuous Amination Reaction: The amination reaction is carried out in a continuous flow pipeline reactor, where p-toluenesulfonyl chloride solution and ammonia water are continuously fed into the reaction to generate p-toluenesulfonamide in one step; Step 4, Continuous Extraction and Separation: After the reaction is completed, the reaction solution is continuously pumped into a countercurrent extraction tower, and dichloromethane is used for countercurrent extraction to separate the organic phase and the aqueous phase. Step 5, Solvent Recovery and Recycling: The organic phase obtained from the extraction is subjected to continuous vacuum distillation to recover dichloromethane and acetone for recycling. Step 6: Purification: The crude p-toluenesulfonamide melt is purified by gradient vacuum distillation to obtain a high-purity product; Step 7, Waste Treatment and Resource Recycling: Ammonia is recovered by stripping the aqueous phase of the extraction process, the wastewater is treated biochemically to meet discharge standards, and the solid waste is incinerated and utilized as a resource.

[0005] Preferably, in step one, the raw material preparation includes: industrial-grade p-toluenesulfonyl chloride as the acylation raw material with a purity ≥98.5%; industrial-grade concentrated ammonia as the amination reagent with a mass concentration of 26%–27%; industrial-grade acetone as the reaction co-solvent with a purity ≥99%; tetrabutylammonium bromide as the phase transfer catalyst with a purity ≥99%; and dichloromethane extractant as the efficient extraction and separation medium.

[0006] Preferably, in step one, the raw material preparation involves controlling the raw material molar ratio to be p-toluenesulfonyl chloride: ammonia = 1:1.2 to 1:1.5, wherein ammonia is in excess of p-toluenesulfonyl chloride by 20% to 50%; and the amount of phase transfer catalyst is 0.5% to 1.0% of the mass of sulfonyl chloride.

[0007] Preferably, in step two, the raw material pretreatment involves placing p-toluenesulfonyl chloride in a vacuum drying oven and drying it for 1.5-2 hours under vacuum conditions of -0.08 to -0.09 MPa and a temperature of 45 to 50°C, controlling the moisture content to be ≤0.08%; preparing an acetone-water mixed solvent by volume ratio of acetone:water = 3:1, and then adding tetrabutylammonium bromide to make its concentration in the acetone-water mixed solvent 0.8 ± 0.2 g / L.

[0008] Preferably, the continuous amination reaction process in step three is as follows: S1.1 Dissolve the dried p-toluenesulfonyl chloride in an acetone-water mixed solvent containing tetrabutylammonium bromide to prepare a p-toluenesulfonyl chloride solution with a mass fraction of 20% to 30%. S1.2. Using a precision metering pump, p-toluenesulfonyl chloride solution and ammonia water are continuously fed into the pipeline reactor at a set flow rate, so that the linear velocity of the reaction liquid in the pipeline is 0.5 to 1.2 m / s. S1.3. Using the reverse feeding method, ammonia solution is introduced as a continuous phase from the main pipeline at a flow rate of 100-180 mL / min, and p-toluenesulfonyl chloride solution is introduced from the side branch pipe at a flow rate of 50-70 mL / min. The molar ratio of p-toluenesulfonyl chloride solution to ammonia solution is controlled by adjusting the flow rate ratio of the two materials to be p-toluenesulfonyl chloride solution: ammonia solution = 1:1.2-1:1.5. S1.4 The reaction temperature is controlled at 22±2℃, and the temperature is controlled by the jacket circulating water. The residence time is controlled at 45 to 50 minutes. A static mixing element is installed in the reactor, and an online sampling port is installed at the end of the pipeline to monitor the reaction process.

[0009] Preferably, the continuous amination reaction in step three includes: In the formula, Indicates p-toluenesulfonyl chloride, Indicates ammonia, Tetrabutylammonium bromide is used; an acetone-water mixed solvent provides a homogeneous reaction environment. p-Toluenesulfonyl chloride and ammonia undergo a nucleophilic substitution amination reaction in an acetone-water mixed solvent under the catalysis of tetrabutylammonium bromide, yielding the target product p-toluenesulfonamide at a temperature of 22±2℃ and a residence time of 45–50 minutes. and by-product ammonium chloride .

[0010] Preferably, the continuous extraction and separation process in step four: S2.1 After the continuous amination reaction in step three is completed, the reaction solution is continuously pumped into the top of the countercurrent extraction tower through a high-pressure metering pump at a flow rate of 180-250 mL / min. At the same time, dichloromethane extractant is continuously added from the bottom of the tower through another precision metering pump at a flow rate of 200-250 mL / min. The flow rates of the two pumps are controlled so that the volume ratio of reaction solution to dichloromethane is 1:1 to 1:1.2. S2.2 The extraction temperature is controlled at 27±3℃ by circulating water in the tower jacket and a high-efficiency sieve plate is installed inside the tower. S2.3. The dichloromethane organic phase containing p-toluenesulfonamide products is continuously collected from the top of the tower and sent to the next process. S2.4. The aqueous phase containing ammonia, catalyst and by-product salt is continuously discharged from the bottom of the tower and enters the wastewater treatment unit.

[0011] Preferably, in step five, solvent recovery and recycling: S3.1 The dichloromethane organic phase continuously collected from the top of the column in step four is continuously fed into a thin-film evaporator or a distillation column for the next solvent recovery process. S3.2 First, dichloromethane is distilled off under normal pressure and 40-45℃ conditions. After condensation, it is dehydrated by molecular sieve and reused in the extraction process. S3.3, then switch to absolute pressure of 15-20 kPa and temperature of 40-50℃ to distill off acetone, and condense it back for use as a reaction solvent. S3.4 After removing the solvent by evaporation, crude p-toluenesulfonamide melt is obtained.

[0012] Preferably, in step six, the purification process involves feeding the crude p-toluenesulfonamide melt obtained after removing the solvent in step five into a continuous distillation column. Gradient heating distillation is carried out under absolute pressure of 2–5 kPa, and the temperature range of the main fraction is 180–200°C to obtain purified p-toluenesulfonamide. The heavy components remaining at the bottom of the column are collected as solid waste.

[0013] Preferably, in step seven, the treatment of waste and resource recovery are as follows: the aqueous phase continuously discharged from the bottom of the tower in step four is first stripped to recover residual ammonia for reuse in production. After stripping, the wastewater enters the biochemical treatment system and is treated using the A / O process to meet discharge standards. When the wastewater contains trace amounts of cyanide, it is first oxidized with sodium hypochlorite to break down the cyanide before entering the biochemical system. The distillation residue and solid waste of the spent catalyst are sent to a high-temperature roasting furnace for incineration. The ash is used as a building material raw material, and the recovered organic solvent is purified by distillation and then recycled.

[0014] Compared with the prior art, the present invention provides a safe and efficient synthesis process for o-p-toluenesulfonamide, which has the following beneficial effects: 1. This invention employs a continuous flow pipeline reactor for amination reaction, combined with reverse feeding technology and turbulent mixing control, to shorten the reaction time, thereby improving the reaction conversion rate and production efficiency. Simultaneously, by precisely controlling temperature and material ratio, side reactions are effectively suppressed, improving product yield and quality. Furthermore, by using a countercurrent extraction tower for continuous extraction and gradient vacuum distillation purification, replacing traditional batch extraction and recrystallization processes, separation efficiency and product purity are significantly improved, achieving both high process efficiency and superior product quality.

[0015] 2. This invention achieves continuous production from raw material input to product output through a fully integrated continuous process design. The operation is stable and highly automated. By adopting continuous extraction and solvent recovery technologies, the consumption of organic solvents is significantly reduced and recycled. At the same time, gradient distillation replaces recrystallization to avoid the generation of saline organic wastewater, thereby reducing wastewater discharge. Through precise temperature control and continuous flow reaction mode, the safety hazards of local overconcentration and overheating in batch reactions are eliminated. Excess ammonia is recovered and reused, wastewater is biochemically treated and solid waste is utilized, thus fully realizing green and clean production and inherent process safety. Attached Figure Description

[0016] Figure 1 This is a flowchart of the synthesis process of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figure 1 A safe and efficient synthesis process for ortho- and p-toluenesulfonamides includes the following steps: Step 1: Raw material preparation: Select p-toluenesulfonyl chloride, ammonia, acetone, tetrabutylammonium bromide and dichloromethane extractant as raw materials; Step 2, Raw material pretreatment: p-Toluenesulfonyl chloride is vacuum dried, and reaction solvent and catalyst solution are prepared; Step 3, Continuous Amination Reaction: The amination reaction is carried out in a continuous flow pipeline reactor, where p-toluenesulfonyl chloride solution and ammonia water are continuously fed into the reaction to generate p-toluenesulfonamide in one step; Step 4, Continuous Extraction and Separation: After the reaction is completed, the reaction solution is continuously pumped into a countercurrent extraction tower, and dichloromethane is used for countercurrent extraction to separate the organic phase and the aqueous phase. Step 5, Solvent Recovery and Recycling: The organic phase obtained from the extraction is subjected to continuous vacuum distillation to recover dichloromethane and acetone for recycling. Step 6: Purification: The crude p-toluenesulfonamide melt is purified by gradient vacuum distillation to obtain a high-purity product; Step 7, Waste Treatment and Resource Recycling: Ammonia is recovered by stripping the aqueous phase of the extraction process, the wastewater is treated biochemically to meet discharge standards, and the solid waste is incinerated and utilized as a resource.

[0019] Specifically, in step one, the raw material preparation is as follows: industrial-grade p-toluenesulfonyl chloride is selected as the core acylation raw material, with a purity ≥98.5% and a density of 1.4±0.05 g / cm³; industrial-grade concentrated ammonia is used as the amination reagent, with a mass concentration of 26%~27% and a density of 0.9±0.005 g / cm³; industrial-grade acetone is used as the reaction co-solvent, with a purity ≥99% and a density of 0.79±0.002 g / cm³; tetrabutylammonium bromide is used as the phase transfer catalyst, with a purity ≥99%; and dichloromethane extractant is used as a highly efficient extraction and separation medium, with a boiling point of 39.6℃, which facilitates subsequent recycling. All raw materials must be inspected and qualified before use.

[0020] Specifically, in step one, the raw material preparation involves controlling the raw material molar ratio to be p-toluenesulfonyl chloride: ammonia = 1:1.2 to 1:1.5, the amount of phase transfer catalyst to be 0.5% to 1.0% of the mass of sulfonyl chloride, and the amount of ammonia in appropriate excess to ensure complete reaction of sulfonyl chloride, while avoiding excessive excess that would increase the load on subsequent wastewater treatment and prevent waste of raw materials.

[0021] Specifically, in step two, the raw material pretreatment is as follows: p-Toluenesulfonyl chloride is placed in a vacuum drying oven and dried for 1.5-2 hours under vacuum conditions of -0.08 to -0.09 MPa and temperature of 45 to 50°C, controlling the moisture content to ≤0.08% to avoid hydrolysis side reactions of p-toluenesulfonyl chloride in water. An acetone-water mixed solvent is prepared at a volume ratio of acetone:water = 3:1, and then tetrabutylammonium bromide is added to make its concentration in the acetone-water mixed solvent 0.8±0.2 g / L. The mixture is stirred and dissolved for later use. Ammonia water can be used directly without pretreatment.

[0022] Specifically, the continuous amination reaction process in step three: S1.1 Dissolve the dried p-toluenesulfonyl chloride in an acetone-water mixed solvent containing tetrabutylammonium bromide to prepare a p-toluenesulfonyl chloride solution with a mass fraction of 20% to 30%. S1.2. Using a precision metering pump, p-toluenesulfonyl chloride solution and ammonia water are continuously fed into the pipeline reactor at a set flow rate (total feed flow rate controlled at 150-250 mL / min (based on a DN50 pipeline reactor), so that the linear velocity of the reaction liquid in the pipeline is 0.5-1.2 m / s, ensuring turbulent flow (Re > 4000) to enhance mixing and mass transfer). S1.3. Using a reverse feeding method, ammonia solution is introduced as a continuous phase from the main pipeline at a flow rate of 100-180 mL / min, and p-toluenesulfonyl chloride solution is introduced from the side branch pipe at a flow rate of 50-70 mL / min. The molar ratio of p-toluenesulfonyl chloride solution to ammonia solution is controlled by adjusting the flow rate ratio of the two materials to 1:1.2-1:1.5. Turbulent mixing is used to ensure instantaneous uniform contact. S1.4 The reaction temperature is controlled at 22±2℃, and the temperature is controlled by the jacketed circulating water. The residence time is controlled at 45 to 50 minutes (corresponding to a total pipeline length of 40 to 50 meters) to ensure a conversion rate of ≥98.5%. Static mixing elements (such as spiral or grid types) are set in the reactor to further enhance the two-phase mixing. An online sampling port is set at the end of the pipeline to monitor the reaction process. This continuous reaction mode eliminates the side reactions caused by local over-concentration in the batch reaction and greatly improves the safety of the process.

[0023] Specifically, the continuous amination reaction formula in step three includes: In the formula, p-Toluenesulfonyl chloride is the acylation reagent in the reaction, providing a sulfonyl group. Ammonia, derived from industrial-grade concentrated ammonia solution (26%–27% by mass), participates in the reaction as a nucleophile. Tetrabutylammonium bromide acts as a phase transfer catalyst, accelerating the two-phase reaction. An acetone-water mixed solvent (volume ratio 3:1) provides a homogeneous reaction environment, promoting sufficient contact between reactants. Under the catalysis of tetrabutylammonium bromide, p-toluenesulfonyl chloride and ammonia undergo a nucleophilic substitution amination reaction in the acetone-water mixed solvent to generate the target product, p-toluenesulfonamide. and by-product ammonium chloride The reaction uses a continuous pipeline reactor, which achieves instantaneous uniform contact through reverse feeding and turbulent mixing. The temperature is precisely controlled at 22±2℃, and the residence time is 45 to 50 minutes to ensure a conversion rate of ≥98.5%, with few side reactions. The process is safe and efficient, and the reaction solution is directly fed into a continuous extraction process for separation and purification.

[0024] Specifically, the continuous extraction and separation process in step four: S2.1 After the continuous amination reaction in step three is completed, the reaction solution is continuously pumped into the top of the countercurrent extraction column through a high-pressure metering pump at a flow rate of 180-250 mL / min. At the same time, dichloromethane extractant is continuously added from the bottom of the column through another precision metering pump at a flow rate of 200-250 mL / min. The flow rates of the two pumps are controlled to make the volume ratio of reaction solution: dichloromethane = 1:1 to 1:1.2 (adjusted in real time according to the product concentration in the reaction solution to ensure complete extraction). S2.2. The extraction temperature is controlled at 27±3℃. The temperature is precisely controlled by circulating water in the tower jacket or by an external heat exchanger. The tower is equipped with high-efficiency sieve plates or structured packing layers (3 to 5 trays) to achieve countercurrent contact between the two phases and full mass transfer. S2.3. The dichloromethane organic phase rich in p-toluenesulfonamide products is continuously collected from the top of the tower and sent to the next process. S2.4 The aqueous phase containing ammonia, catalyst and by-product salt is continuously discharged from the bottom of the tower and enters the wastewater treatment unit. Compared with batch extraction, this continuous extraction method improves efficiency by more than 30%, reduces solvent consumption by 15% to 20%, and has stable operation and high degree of automation.

[0025] Specifically, in step five, solvent recovery and recycling: S3.1 The dichloromethane organic phase rich in p-toluenesulfonamide products continuously collected from the top of the column in step four is continuously fed into a thin-film evaporator or a distillation column. S3.2 First, dichloromethane is distilled off under normal pressure and 40-45℃ conditions. After condensation, it is dehydrated by molecular sieve and reused in the extraction process. S3.3, then switch to absolute pressure of 15-20 kPa and temperature of 40-50℃ to distill off acetone, and condense it back for use as a reaction solvent. S3.4 After removing the solvent, crude p-toluenesulfonamide melt is obtained, with a solvent recovery rate of over 95%, which significantly reduces the cost of fresh solvent consumption.

[0026] Specifically, in step six, the refining and purification process involves feeding the crude p-toluenesulfonamide melt obtained after solvent removal in step five into a continuous distillation column. Gradient temperature distillation is performed under absolute pressure of 2–5 kPa, collecting the main fraction at temperatures ranging from 180 to 200°C to obtain refined p-toluenesulfonamide with a purity ≥99.5%, meeting the premium grade standard. The remaining heavy components at the bottom of the column are collected as solid waste. This distillation process eliminates the need for a recrystallization step, avoiding wastewater generation, and the product yield is 5%–8% higher than that of the traditional recrystallization method.

[0027] Specifically, in step seven, waste treatment and resource recovery are as follows: the aqueous phase continuously discharged from the bottom of the tower in step four (mainly containing excess ammonia, tetrabutylammonium bromide, and a small amount of by-product salt) is first stripped in a stripping tower to recover residual ammonia for reuse in production. After stripping, the wastewater enters the biological treatment system and is treated using the A / O process to meet discharge standards. When the wastewater contains trace amounts of cyanide (originating from switching to other products), it is first oxidized with sodium hypochlorite to break down the cyanide before entering the biological system. Solid wastes such as distillation residue and spent catalyst are sent to a high-temperature roasting furnace for incineration. The ash is used as a building material raw material. The recovered organic solvent is purified by distillation and then recycled. The entire process maximizes resource utilization.

[0028] The synthesis process of the present invention was applied to the following embodiments, and a traditional batch reactor process was used as a control, as follows: Example 1: Synthesis was carried out according to the process parameters described in steps one through seven.

[0029] Specifically: the raw material molar ratio of p-toluenesulfonyl chloride to ammonia is 1:1.3, and the amount of tetrabutylammonium bromide catalyst is 0.8% of the mass of sulfonyl chloride; in step three, the continuous amination reaction is carried out: a 25% p-toluenesulfonyl chloride solution is prepared, the total feed flow rate is 200 mL / min (130 mL / min for ammonia and 70 mL / min for sulfonyl chloride solution), the reaction temperature is 22℃, and the residence time is 48 minutes; in step four, the continuous extraction is carried out: the reaction liquid flow rate is 200 mL / min, the dichloromethane flow rate is 220 mL / min (volume ratio 1:1.1), and the extraction temperature is 27℃; in step five, the solvent is recovered; in step six, distillation is carried out under absolute pressure of 3 kPa, and the fraction at 185-195℃ is collected to finally obtain purified p-toluenesulfonamide, and the yield and purity are calculated.

[0030] Example 2: Basically the same as Example 1, except that the amount of tetrabutylammonium bromide catalyst is 1.0% of the mass of sulfonyl chloride, the reaction temperature in step 3 is controlled at 24±2℃, the residence time is 45 minutes, and the other conditions are the same as in Example 1.

[0031] Example 3: Basically the same as Example 1, except that: the raw material molar ratio of p-toluenesulfonyl chloride:ammonia water = 1:1.5, the extraction volume ratio in step four is controlled as reaction solution:dichloromethane = 1:1.2, the extraction temperature is 30℃, and the other conditions are the same as in Example 1.

[0032] Comparative Example 1 employed a conventional batch reactor synthesis process. In a 2L reactor, p-toluenesulfonyl chloride and an acetone-water mixture were added and stirred until dissolved. Ammonia was then slowly added dropwise while maintaining the temperature at 20-25°C for 2 hours. After the reaction, acetone was first removed by atmospheric distillation. The remaining liquid was extracted three times with dichloromethane (200 mL each time). The combined organic phases were washed with saturated brine and dried over anhydrous sodium sulfate. After filtration, dichloromethane was removed by atmospheric distillation. The crude product was purified by recrystallization from ethanol-water to obtain the p-toluenesulfonamide product.

[0033] Comparative Example 2: Basically the same as Comparative Example 1, except that: no tetrabutylammonium bromide catalyst was added, and the reaction time was extended to 4 hours. The rest of the operation was the same as Comparative Example 1.

[0034] Comparative Example 3: Basically the same as Comparative Example 1, except that the reaction temperature is increased to 35-40℃ and the side reactions are observed. The rest of the operation is the same as Comparative Example 1.

[0035] Examples 1-3, using the continuous synthesis process of this invention, achieved product yields of over 96.5%, significantly higher than the 76.5%-89.3% of Comparative Examples 1-3. Product purity was ≥99.5%, meeting the premium grade standard, while the comparative examples had lower purity, especially Comparative Example 2 (without catalyst) and Comparative Example 3 (at a higher temperature), which showed increased impurity content. In terms of reaction efficiency, the continuous process had a reaction time of only 45-50 minutes, far lower than the 2-4 hours of the batch process, resulting in a significant increase in production efficiency. Regarding environmental protection and cost, the continuous process consumed only about 50% of the solvent (1.7-1.8 kg / kg product) and generated only about 2.4-2.5 L / kg product, demonstrating the advantages of green synthesis. The appearance and melting point range of the obtained products also indicated that the continuous process produced products with more stable quality and higher purity.

[0036] In summary, the present invention provides a safe and efficient synthesis process for o-toluenesulfonamide. By adopting a continuous pipeline reactor for amination reaction, continuous extraction and separation in a countercurrent extraction tower, continuous solvent recovery through thin-film evaporation, and continuous purification by gradient vacuum distillation, the entire process from raw materials to products can be continuously produced. Compared with the traditional batch reactor process, the present invention has the following advantages: (1) the reaction time is shortened by more than 60%, and the production efficiency is greatly improved; (2) the product yield is increased by 8%-10%, and the purity reaches more than 99.5%; (3) the solvent consumption is reduced by about 50%, and the wastewater generation is reduced by more than 60%, which significantly reduces the environmental pressure; (4) through optimization measures such as reverse feeding, phase transfer catalysis, and precise temperature control, there are fewer side reactions and the process is safe and controllable; (5) organic solvents and excess ammonia are recovered and recycled, which meets the requirements of green chemical industry and sustainable development. Therefore, the process of the present invention has the advantages of safety, efficiency, cleanliness and economy.

[0037] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A safe and efficient synthesis process for o- and p-toluenesulfonamides, characterized in that, Includes the following steps: Step 1: Raw material preparation: Select p-toluenesulfonyl chloride, ammonia, acetone, tetrabutylammonium bromide and dichloromethane extractant as raw materials; Step 2, Raw material pretreatment: p-Toluenesulfonyl chloride is vacuum dried, and reaction solvent and catalyst solution are prepared; Step 3, Continuous Amination Reaction: The amination reaction is carried out in a continuous flow pipeline reactor, where p-toluenesulfonyl chloride solution and ammonia water are continuously fed into the reaction to generate p-toluenesulfonamide in one step; Step 4, Continuous Extraction and Separation: After the reaction is completed, the reaction solution is continuously pumped into a countercurrent extraction tower, and dichloromethane is used for countercurrent extraction to separate the organic phase and the aqueous phase. Step 5, Solvent Recovery and Recycling: The organic phase obtained from the extraction is subjected to continuous vacuum distillation to recover dichloromethane and acetone for recycling. Step 6: Purification: The crude p-toluenesulfonamide melt is purified by gradient vacuum distillation to obtain a high-purity product; Step 7, Waste Treatment and Resource Recycling: Ammonia is recovered by stripping the aqueous phase of the extraction process, the wastewater is treated biochemically to meet discharge standards, and the solid waste is incinerated and utilized as a resource.

2. The safe and efficient synthesis process of o-toluenesulfonamide according to claim 1, characterized in that, In step one, the raw material preparation is as follows: industrial-grade p-toluenesulfonyl chloride is selected as the acylation raw material with a purity ≥98.5%; industrial-grade concentrated ammonia is selected as the amination reagent with a mass concentration of 26% to 27%; industrial-grade acetone is selected as the reaction co-solvent with a purity ≥99%; tetrabutylammonium bromide is selected as the phase transfer catalyst with a purity ≥99%; and dichloromethane is selected as the efficient extraction and separation medium.

3. The safe and efficient synthesis process of o-toluenesulfonamide according to claim 1, characterized in that, In step one, the raw material preparation is as follows: the raw material molar ratio is controlled to be p-toluenesulfonyl chloride: ammonia = 1:1.2 to 1:1.5, wherein ammonia is in excess of p-toluenesulfonyl chloride by 20% to 50%; the amount of phase transfer catalyst is 0.5% to 1.0% of the mass of sulfonyl chloride.

4. The safe and efficient synthesis process of o-toluenesulfonamide according to claim 1, characterized in that, In step two, the raw material pretreatment involves placing p-toluenesulfonyl chloride in a vacuum drying oven and drying it for 1.5-2 hours at a vacuum of -0.08 to -0.09 MPa and a temperature of 45 to 50°C, controlling the moisture content to be ≤0.08%. An acetone-water mixed solvent is prepared by volume ratio of acetone:water = 3:1, and then tetrabutylammonium bromide is added to make its concentration in the acetone-water mixed solvent 0.8 ± 0.2 g / L.

5. The safe and efficient synthesis process of o-toluenesulfonamide according to claim 1, characterized in that, The continuous amination reaction process in step three: S1.1 Dissolve the dried p-toluenesulfonyl chloride in an acetone-water mixed solvent containing tetrabutylammonium bromide to prepare a p-toluenesulfonyl chloride solution with a mass fraction of 20% to 30%. S1.

2. Using a precision metering pump, p-toluenesulfonyl chloride solution and ammonia water are continuously fed into the pipeline reactor at a set flow rate, so that the linear velocity of the reaction liquid in the pipeline is 0.5 to 1.2 m / s. S1.

3. Using the reverse feeding method, ammonia solution is introduced as a continuous phase from the main pipeline at a flow rate of 100-180 mL / min, and p-toluenesulfonyl chloride solution is introduced from the side branch pipe at a flow rate of 50-70 mL / min. The molar ratio of p-toluenesulfonyl chloride solution to ammonia solution is controlled by adjusting the flow rate ratio of the two materials to be p-toluenesulfonyl chloride solution: ammonia solution = 1:1.2-1:1.

5. S1.4 The reaction temperature is controlled at 22±2℃, and the temperature is controlled by the jacket circulating water. The residence time is controlled at 45 to 50 minutes. A static mixing element is installed in the reactor, and an online sampling port is installed at the end of the pipeline to monitor the reaction process.

6. The safe and efficient synthesis process of o-toluenesulfonamide according to claim 5, characterized in that, The continuous amination reaction in step three includes: In the formula, Indicates p-toluenesulfonyl chloride, Indicates ammonia, Tetrabutylammonium bromide is used; an acetone-water mixed solvent provides a homogeneous reaction environment. p-Toluenesulfonyl chloride and ammonia undergo a nucleophilic substitution amination reaction in an acetone-water mixed solvent under the catalysis of tetrabutylammonium bromide, yielding the target product p-toluenesulfonamide at a temperature of 22±2℃ and a residence time of 45–50 minutes. and by-product ammonium chloride .

7. The safe and efficient synthesis process of o-toluenesulfonamide according to claim 1, characterized in that, The continuous extraction and separation process in step four: S2.1 After the continuous amination reaction in step three is completed, the reaction solution is continuously pumped into the top of the countercurrent extraction tower through a high-pressure metering pump at a flow rate of 180-250 mL / min. At the same time, dichloromethane extractant is continuously added from the bottom of the tower through another precision metering pump at a flow rate of 200-250 mL / min. The flow rates of the two pumps are controlled so that the volume ratio of reaction solution to dichloromethane is 1:1 to 1:1.

2. S2.2 The extraction temperature is controlled at 27±3℃ by circulating water in the tower jacket and a high-efficiency sieve plate is installed inside the tower. S2.

3. The dichloromethane organic phase containing p-toluenesulfonamide products is continuously collected from the top of the tower and sent to the next process. S2.

4. The aqueous phase containing ammonia, catalyst and by-product salt is continuously discharged from the bottom of the tower and enters the wastewater treatment unit.

8. The safe and efficient synthesis process of o-toluenesulfonamide according to claim 1, characterized in that, Solvent recovery and recycling in step five: S3.1 The dichloromethane organic phase continuously collected from the top of the column in step four is continuously fed into a thin-film evaporator or a distillation column for the next solvent recovery process. S3.2 First, dichloromethane is distilled off under normal pressure and 40-45℃ conditions. After condensation, it is dehydrated by molecular sieve and reused in the extraction process. S3.3, then switch to absolute pressure of 15-20 kPa and temperature of 40-50℃ to distill off acetone, and condense it back for use as a reaction solvent. S3.4 After removing the solvent by evaporation, crude p-toluenesulfonamide melt is obtained.

9. The safe and efficient synthesis process of o-toluenesulfonamide according to claim 1, characterized in that, In step six, the purification process involves feeding the crude p-toluenesulfonamide melt obtained after removing the solvent in step five into a continuous distillation column. Gradient heating distillation is carried out under absolute pressure of 2–5 kPa, and the temperature range of the main fraction is 180–200 °C to obtain purified p-toluenesulfonamide. The heavy components remaining at the bottom of the column are collected as solid waste.

10. The safe and efficient synthesis process of o-toluenesulfonamide according to claim 1, characterized in that, In step seven, the treatment of waste and resource recovery are as follows: the aqueous phase continuously discharged from the bottom of the tower in step four is first stripped to recover residual ammonia for reuse in production. After stripping, the wastewater enters the biochemical treatment system and is treated using the A / O process to meet discharge standards. When the wastewater contains trace amounts of cyanide, it is first oxidized with sodium hypochlorite to break down the cyanide before entering the biochemical system. The distillation residue and solid waste of the spent catalyst are sent to a high-temperature roasting furnace for incineration. The ash is used as a building material raw material, and the recovered organic solvent is purified by distillation and then recycled.

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