A continuous synthesis apparatus and method for p-toluenesulfonyl chloride.

Abstract

The present application relates to a kind of continuous synthesis device of p-toluenesulfonyl chloride and synthesis method thereof.The synthesis method described in the present application is as follows:(1) the chlorosulfonic acid of first addition, catalyst, organic solvent are mixed in the first static mixer to obtain mixed liquid A, the mixed liquid A, toluene are pumped into first microreactor respectively to carry out reaction to obtain reaction liquid;(2) the reaction liquid is discharged from the outlet of first microreactor and separates out liquid phase, the liquid phase, the chlorosulfonic acid of second addition are pumped into second microreactor with mixed liquid B in the second static mixer respectively and mixed, carry out reaction in second microreactor to obtain secondary reaction mixture;(3) secondary reaction mixture is discharged from second microreactor and separates out intermediate layer frozen crystallization, filtration, washing, obtains p-toluenesulfonyl chloride.The synthesis method of the present application accurately controls reaction temperature, time, material ratio, greatly improves the production efficiency of p-toluenesulfonyl chloride, green, safe and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of fine chemical intermediate preparation technology, specifically to a continuous synthesis apparatus and method for p-toluenesulfonyl chloride. Background Technology

[0002] p-Toluenesulfonyl chloride (C7H7ClO2S) is an important fine chemical product. It is a white, flaky crystal widely used in the dye, pharmaceutical, and pesticide industries. The synthesis of p-toluenesulfonyl chloride can be achieved through several routes depending on the raw materials: ① using p-toluenesulfonic acid, chlorine, and S2Cl2 as raw materials; ② using thiols, KNO3, and S2Cl2 as raw materials; ③ using p-toluenesulfonamide as a raw material; ④ using toluene, chlorosulfonic acid, and ammonium chloride as raw materials; ⑤ using toluene and chlorosulfonic acid as raw materials, with N,N-dimethylacetamide or triethylamine as a catalyst; ⑥ using toluene, chlorosulfonic acid, and thionyl chloride as raw materials, with aminosulfonic acid as a catalyst, etc.

[0003] Of the synthetic routes listed above, routes ④, ⑤, and ⑥ all involve toluene sulfonation, with the toluene sulfonation method using toluene and chlorosulfonic acid as the main raw materials being the most widely used. However, this route suffers from high reaction temperatures, low production efficiency, and generates large amounts of dilute sulfuric acid waste liquid and hydrogen chloride gas, causing severe equipment corrosion and environmental pollution. Furthermore, it lacks precise control over the reaction process, and the yield needs improvement. Currently, route ④ is widely used in China, but the existing process has a low yield and generates large amounts of acidic wastewater, causing environmental pollution. Therefore, improving the yield of toluene chlorosulfonation, reducing environmental pollution, and lowering production costs are of significant social and economic importance.

[0004] To address this, domestic and international efforts have been made to improve production processes, aiming to reduce environmental pollution and increase yield. Xu Yun, Wang Hongliang, et al. (Zhejiang Chemical Industry [J], 2003(10): 10-11) used toluene as the starting material, carbon tetrachloride as the diluent, and selected a composite catalyst to synthesize p-toluenesulfonyl chloride through acyl chlorination with chlorosulfonic acid. They then used a new process of direct solvent crystallization purification and separation to obtain p-toluenesulfonyl chloride with a purity of 98% and a product yield of over 88%. Chen Zhongxiu, Jiang Linwei, et al. used toluene, oxysulfonic acid, and phosphorus oxychloride as raw materials, achieving a p-toluenesulfonyl chloride yield of 85.41%, while reducing acidic wastewater by more than 70% compared to the original process (Journal of Chemical Engineering of Chinese Universities, 2004, 18(2): 254-257). The processes or production systems disclosed in the above literature can only be improved based on traditional processes, without any substantial technological advancement.

[0005] CN103588683A discloses a synthesis process for p-toluenesulfonyl chloride with a yield as high as 99.87%, but it still suffers from complex raw materials, high raw material costs, and the problem of large waste acid production. CN201520995039 reports a production system for p-toluenesulfonyl chloride, including a sulfonation reactor, a decomposition reactor, and a product post-processing system connected in sequence. This series connection of reactors does not solve the problems of control, continuity, yield, and waste acid in the production process, and it is impossible to achieve automation.

[0006] CN113277965A discloses a method for the continuous synthesis of p-toluenesulfonyl chloride using a microchannel reactor. The materials are directly fed into the microchannel reactor for reaction, achieving a maximum crude product yield of 95.12%. This method also enables continuous production and significantly reduces waste acid output. CN113582883A discloses a continuous synthesis method for p-toluenesulfonyl chloride, using toluene, sulfur trioxide, chlorosulfonic acid, organic bases, solvents, and inhibitors as raw materials in a two-microchannel reactor series reaction. None of these patents separate the sulfonation and acyl chloride reactions. CN113277965A has specific requirements for the microreactor used, and CN113582883A requires the reaction to be carried out at low temperatures. This method uses complex materials and readily crystallizable SO3, increasing the operational difficulty and making it difficult to promote in actual industrial production. CN101195593 discloses a method for sulfonation using sulfur trioxide and diluent alkylbenzene, but its promotion in actual industrial production of SO3 is still quite difficult. Furthermore, the tubular reactor used is difficult to control precisely due to its structural characteristics, and the pollution problem has not been effectively solved.

[0007] Despite the numerous problems with the toluene-chlorosulfonic acid-based toluenesulfonyl process, it remains the preferred method for producing p-toluenesulfonyl chloride due to its advantages such as fewer operating steps and shorter reaction cycle. However, the excessive use of chlorosulfonic acid, the large amounts of hydrogen chloride gas and dilute sulfuric acid generated during the reaction, which severely corrode equipment, are difficult and costly to handle, pollute the environment, and result in low product yields are all urgent issues that need to be addressed. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a continuous synthesis apparatus and method for p-toluenesulfonyl chloride. This invention enables precise control of reaction temperature, reaction time, and reactant ratio, significantly improving the production efficiency of p-toluenesulfonyl chloride while being green, safe, and environmentally friendly.

[0009] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0010] The first objective of this invention is to provide a continuous synthesis apparatus for p-toluenesulfonyl chloride, the apparatus comprising a first static mixer, a toluene storage tank, a first microreactor, a first gas-liquid two-phase separator, a first falling film absorber, a second microreactor, a chlorosulfonic acid storage tank, a second microreactor, a second gas-liquid two-phase separator, a sulfuric acid storage tank, a cryogenic crystallizer, a centrifuge, a first metering pump, a second metering pump, a third metering pump, a fourth metering pump, a fifth metering pump, a sixth metering pump, a first inlet pipe, a second inlet pipe, a third inlet pipe, a fourth inlet pipe, a fifth inlet pipe, a first connecting pipe, a second connecting pipe, a third connecting pipe, a fourth connecting pipe, a fifth connecting pipe, and an absorption pipe;

[0011] The first static mixer is connected to the inlet of the first microreactor via the first inlet pipe, and the first metering pump is installed on the first inlet pipe; the toluene storage tank is connected to the inlet of the first microreactor via the second inlet pipe, and the second metering pump is installed on the second inlet pipe; the first microreactor is connected to the first gas-liquid two-phase separator via the first connecting pipe.

[0012] The first gas-liquid two-phase separator has two outlets. The first outlet of the first gas-liquid two-phase separator is connected to the first falling film absorber through the absorption pipe. The second outlet of the first gas-liquid two-phase separator is connected to the inlet of the second microreactor through the third inlet pipe. The third inlet pipe is equipped with the third metering pump.

[0013] The chlorosulfonic acid storage tank is connected to the inlet of the second microreactor via the fourth inlet pipe, and the fourth metering pump is installed on the fourth inlet pipe; the second static mixer is connected to the second microreactor via the fifth inlet pipe, and the fifth metering pump is installed on the fifth inlet pipe.

[0014] The outlet of the second microreactor is connected to the second gas-liquid two-phase separator via a second connecting pipe; the second gas-liquid two-phase separator has three outlets, the first outlet of the second gas-liquid two-phase separator is connected to the second falling film absorber; the second outlet of the second gas-liquid two-phase separator is connected to the inlet of the sulfuric acid storage tank via the fourth connecting pipe, and the sixth metering pump is installed on the fourth connecting pipe; the third outlet of the second gas-liquid two-phase separator is connected to the freeze crystallizer via the third connecting pipe, the freeze crystallizer is then connected to the centrifuge via the third connecting pipe, and the centrifuge is connected to the second static mixer via the fifth connecting pipe.

[0015] The second objective of this invention is to provide a continuous method for the synthesis of p-toluenesulfonyl chloride, as detailed below:

[0016] (1) The chlorosulfonic acid, catalyst and organic solvent added at one time are mixed in the first static mixer to obtain mixture A. Mixture A and toluene are pumped into the first microreactor to react and obtain reaction solution.

[0017] (2) The reaction solution is discharged from the outlet of the first microreactor and the liquid phase is separated. The liquid phase and the second-added chlorosulfonic acid are pumped into the second microreactor with the mixture B in the second static mixer for mixing. The reaction is carried out in the second microreactor to obtain a secondary reaction mixture.

[0018] (3) The secondary reaction mixture is discharged from the second microreactor and the intermediate layer is separated by freezing crystallization, filtration, and washing to obtain p-toluenesulfonyl chloride.

[0019] The beneficial effects of this invention are as follows: Firstly, in a microchannel reactor, chlorosulfonic acid is used as a sulfonating agent to react with toluene and a catalyst to prepare a p-toluenesulfonic acid mixture. This p-toluenesulfonic acid mixture is then reacted with chlorosulfonic acid and an organic solvent in a second microreactor to synthesize p-toluenesulfonyl chloride—a green process. This invention features continuous production, allowing for precise control of reaction temperature, reaction time, and reactant ratios, significantly improving the production efficiency of p-toluenesulfonyl chloride. The addition of inhibitors effectively solves the problem of generating large amounts of sulfones and polysulfides as byproducts during the reaction, and avoids equipment corrosion from hydrogen chloride gas.

[0020] Preferably, the molar ratio of the chlorosulfonic acid, the catalyst, and the organic solvent added in step (1) is 1:0.01~0.02:1.0~3.0.

[0021] Based on the above technical solution, the present invention can be further improved as follows.

[0022] Furthermore, the temperature in the first static mixer is 25℃-45℃; the temperature in the second static mixer is 35℃-65℃.

[0023] Furthermore, the mixture B mentioned in step (2) includes the following materials: catalyst, organic solvent, and inhibitor.

[0024] Furthermore, in step (2), the molar ratio of the liquid phase to the organic solvent, chlorosulfonic acid, catalyst, and inhibitor in the mixture B is 1:1.0~3.0:0.01~0.02:0.01~0.22:0.01~0.3.

[0025] The beneficial effects of adopting the above-mentioned further scheme are: the sulfonation reaction and acyl chloride reaction of this application are carried out in steps, the proportion of chlorosulfonic acid in the steps is strictly controlled, and the side reaction that occurs after excessive addition is avoided, resulting in byproducts such as ortho- and p-toluenesulfonyl chloride, which greatly improves the yield of p-toluenesulfonyl chloride.

[0026] Furthermore, the catalyst is ammonium chloride; the inhibitor includes at least one of acetic acid, propionic acid, isopropionic acid, chloroacetic acid, and trifluoroacetic acid.

[0027] The beneficial effects of adopting the above-mentioned further scheme are: the addition of inhibitors in this invention can effectively prevent the sulfonation of multiple sites of toluene during the reaction process, the generation of disulfonic acid or trisulfonic acid derivatives, and by-products such as sulfones.

[0028] Furthermore, the reaction liquid enters the second gas-liquid two-phase separator to separate into gas, sulfonated oil, intermediate layer and lower layer. The separated gas is absorbed by the second falling film absorber, the sulfonated oil is used for purification to obtain o-benzenesulfonyl chloride, iso-benzene, and sulfonyl chloride, and the lower layer is recovered and sent to the sulfuric acid storage tank.

[0029] Furthermore, the organic solvent includes at least one of dichloromethane, trichloromethane, 1,2-dichloroethane, and dichloroethane.

[0030] Furthermore, the reaction temperature in the first microreactor is 25~45℃, and the reaction time is 0~60min; the reaction temperature in the second microreactor is 45~85℃, and the reaction time is 60~300min.

[0031] The beneficial effects of adopting the above-mentioned further scheme are as follows: the sulfonation reaction in the first microreactor is an electrophilic substitution reaction, which is exothermic and has a relatively fast reaction rate. Theoretically, increasing the reaction temperature can increase the yield of the para-product, but experiments have shown that when the temperature is too high, the color of the reaction system darkens, and large amounts of o-toluenesulfonyl chloride, m-toluenesulfonyl chloride, and high-boiling products (sulfones) are generated, while the yield of the main product is not improved. This invention can achieve precise control of reaction temperature, reaction time, and reactant ratio, significantly improving the production efficiency of p-toluenesulfonyl chloride. Due to the addition of inhibitors, the generation of large amounts of sulfones and polysulfonates as byproducts during the reaction process is effectively solved.

[0032] In the second microreactor, the acyl chlorination reaction using chlorosulfonic acid as the acyl chlorinating agent showed that the yield of the target product increased with increasing temperature.

[0033] Furthermore, the intermediate layer freezing crystallization, filtration, and washing in step (3) are as follows: the intermediate layer that has passed through the separator is separated, frozen and crystallized in a freeze crystallizer, then centrifuged and filtered in a centrifuge. The crude product obtained by filtration is washed and then frozen and crystallized again in a freeze crystallizer to obtain the product.

[0034] The beneficial effects of adopting the above-mentioned further scheme are as follows: This invention enables continuous production, allowing for precise control of reaction temperature, reaction time, and reactant ratio, significantly improving the production efficiency of p-toluenesulfonyl chloride. Because the hydrolysis process is eliminated in the separation of the target product solution, the consumption of chlorosulfonic acid is greatly reduced after reuse, and the amount of waste sulfuric acid is also significantly reduced. Concentrated sulfuric acid is directly separated and can be used for sulfonation production of p-toluenesulfonic acid, achieving the goal of clean and safe production. Attached Figure Description

[0035] Figure 1 This is a flowchart of the production process of the present invention.

[0036] The attached diagram lists the components represented by each number as follows:

[0037] 1-First static mixer, 2-Toluene storage tank, 3-First microreactor, 4-First gas-liquid two-phase separator, 5-First falling film absorber, 7-Chlorosulfonic acid storage tank, 8-Second microreactor, 9-Second gas-liquid two-phase separator, 10-Sulfuric acid storage tank, 11-Freezing crystallizer, 12-Centrifuge, 13-First metering pump, 14-Second metering pump, 15-Third metering pump, 16-Fourth metering pump, 17-Fifth metering pump, 18-Sixth metering pump, 19-First inlet pipe, 20-Second inlet pipe, 21-Third inlet pipe, 22-Fourth inlet pipe, 23-Fifth inlet pipe, 24-First connecting pipe, 25-Second connecting pipe, 26-Third connecting pipe, 27-Fourth connecting pipe, 28-Fifth connecting pipe, 29-Absorption pipe. Detailed Implementation

[0038] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they should be performed according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0039] Example 1:

[0040] The process diagram of the continuous synthesis of p-toluenesulfonyl chloride in this invention is shown below. Figure 1 As shown, the details are as follows:

[0041] The reaction apparatus used in this invention includes a synthesis apparatus comprising a first static mixer 1, a toluene storage tank 2, a first microreactor 3, a first gas-liquid two-phase separator 4, a first falling film absorber 5, a second static mixer 6, a chlorosulfonic acid storage tank 7, a second microreactor 8, a second gas-liquid two-phase separator 9, a sulfuric acid storage tank 10, a cryogenic crystallizer 11, a centrifuge 12, a first metering pump 13, a second metering pump 14, a third metering pump 15, a fourth metering pump 16, a fifth metering pump 17, a sixth metering pump 18, a first inlet pipe 19, a second inlet pipe 20, a third inlet pipe 21, a fourth inlet pipe 22, a fifth inlet pipe 23, a first connecting pipe 24, a second connecting pipe 25, a third connecting pipe 26, a fourth connecting pipe 27, a fifth connecting pipe 28, and an absorption pipe 29.

[0042] The first static mixer 1 is connected to the inlet of the first microreactor 3 via the first inlet pipe 19, and the first metering pump 13 is installed on the first inlet pipe 19; the toluene storage tank 2 is connected to the inlet of the first microreactor 3 via the second inlet pipe 20, and the second metering pump 14 is installed on the second inlet pipe 20; the first microreactor 3 is connected to the first gas-liquid two-phase separator 4 via the first connecting pipe 24.

[0043] The first gas-liquid two-phase separator 4 has two outlets. The first outlet of the first gas-liquid two-phase separator 4 is connected to the first falling film absorber 5 through the absorption pipe 29. The second outlet of the first gas-liquid two-phase separator 4 is connected to the inlet of the second microreactor 8 through the third inlet pipe 21. The third inlet pipe 21 is equipped with a third metering pump 15.

[0044] The chlorosulfonic acid storage tank 7 is connected to the inlet of the second microreactor 8 via the fourth inlet pipe 22, and the fourth metering pump 16 is installed on the fourth inlet pipe 22; the second static mixer 6 is connected to the second microreactor 8 via the fifth inlet pipe 23, and the fifth metering pump 17 is installed on the fifth inlet pipe 23.

[0045] The outlet of the second microreactor 8 is connected to the second gas-liquid two-phase separator 9 through the second connecting pipe 25. The second gas-liquid two-phase separator 9 has three outlets. The first outlet of the second gas-liquid two-phase separator is connected to the second falling film absorber. The second outlet of the second gas-liquid two-phase separator 9 is connected to the inlet of the sulfuric acid storage tank 10 through the fourth connecting pipe 27. The sixth metering pump 18 is installed on the fourth connecting pipe 27. The third outlet of the second gas-liquid two-phase separator 9 is connected to the freeze crystallizer 11 through the third connecting pipe 26. The freeze crystallizer 11 is then connected to the centrifuge 12 through the third connecting pipe 26. The centrifuge 12 is connected to the second static mixer 6 through the fifth connecting pipe 28.

[0046] The following Examples 2-5 all use the above-described device examples.

[0047] Example 2: A continuous synthesis method for p-toluenesulfonyl chloride

[0048] (1) Add 1 mol chlorosulfonic acid, 0.02 mol ammonium chloride and 1 mol dichloroethane to the first static mixer 1 and mix them thoroughly at room temperature to obtain mixture A; pump mixture A and 1 mol toluene into the first microreactor 3 under the action of the first metering pump 13 for sulfonation reaction, the reaction time is 20 min and the temperature is controlled at 30℃ to obtain reaction solution;

[0049] (2) The reaction liquid discharged from the outlet of the first microreactor 3 enters the first gas-liquid two-phase separator 4 to obtain HCl gas and liquid containing p-toluenesulfonic acid. The separated HCl gas enters the first falling film absorber 5 to produce hydrochloric acid. The 1 mol of liquid phase containing p-toluenesulfonic acid separated by the first gas-liquid two-phase separator 4 is pumped into the second microreactor 8 by the third metering pump 15. 2 mol of dichloroethane, 0.02 mol of inhibitor (a mixture of acetic acid and isopropionic acid in a molar ratio of 1:1.5) and 0.02 mol of ammonium chloride are mixed in the second static mixer 6 at 30°C to obtain mixture B. Mixture B is pumped into the second microreactor 8 together with 1 mol of chlorosulfonic acid and mixed with the liquid containing p-toluenesulfonic acid to obtain a mixture for acyl chloride reaction. The reaction time is 300 min and the temperature is controlled at 45°C.

[0050] (3) The secondary reaction mixture discharged from the second microreactor 8 is separated by the second gas-liquid two-phase separator 9 to obtain HCl gas, sulfonated oil, intermediate layer, and lower layer. The HCl gas enters the second falling film absorber to produce hydrochloric acid, and the sulfonated oil is purified to obtain o-benzenesulfonyl chloride, m-benzene, and sulfonyl chloride. The lower layer is recovered and sent to the sulfuric acid storage tank 10. The intermediate layer is crystallized by the freeze crystallizer 11 and then centrifuged and filtered by the centrifuge 12. The crude product obtained by filtration is washed and then frozen and crystallized again by the freeze crystallizer 11 to obtain crude p-toluenesulfonyl chloride as the product. The filtrate obtained by filtration is sent to the chlorosulfonic acid storage tank 7 for recovery and secondary production. The total conversion rate of ortho, meta, and para is 60.44%, and the TsCl yield is 44.23%.

[0051] Example 3: A continuous synthesis method for p-toluenesulfonyl chloride (II)

[0052] (1) Add 1 mol chlorosulfonic acid, 0.02 mol ammonium chloride and 1 mol dichloroethane to the first static mixer 1 and mix thoroughly at room temperature to obtain mixture A; pump mixture A and 1 mol toluene into the first microreactor 3 under the action of the first metering pump 13 for sulfonation reaction, the reaction time is 20 min and the temperature is controlled at 30℃ to obtain reaction solution;

[0053] (2) The reaction liquid discharged from the outlet of the first microreactor 3 enters the first gas-liquid two-phase separator 4 to obtain HCl gas and liquid containing p-toluenesulfonic acid. The separated HCl gas enters the first falling film absorber 5 to produce hydrochloric acid. The 1 mol of liquid phase containing p-toluenesulfonic acid separated by the first gas-liquid two-phase separator 4 is pumped into the second microreactor 8 by the third metering pump 15. 2 mol of dichloroethane, 0.05 mol of inhibitor (a mixture of acetic acid and isopropionic acid in a molar ratio of 1:1.5) and 0.05 mol of ammonium chloride are added to the second static mixer 6 and mixed at 35°C to obtain mixture B. Mixture B is pumped into the second microreactor 8 together with 2 mol of chlorosulfonic acid and mixed with the liquid containing p-toluenesulfonic acid to obtain a mixture for acyl chloride reaction. The reaction time is 300 min and the temperature is controlled at 60°C.

[0054] (3) The secondary reaction mixture discharged from the second microreactor 8 is separated by the second gas-liquid two-phase separator 9 to obtain HCl gas, sulfonated oil, intermediate layer, and lower layer. The HCl gas enters the second falling film absorber to produce hydrochloric acid, and the sulfonated oil is purified to obtain o-benzenesulfonyl chloride and m-toluenesulfonyl chloride. The lower layer is recovered and sent to the sulfuric acid storage tank 10. The intermediate layer is crystallized by the freeze crystallizer 11 and then centrifuged and filtered by the centrifuge 12. The crude product obtained by filtration is washed and then frozen and crystallized again by the freeze crystallizer 11 to obtain crude p-toluenesulfonyl chloride as the product. The filtrate obtained by filtration is sent to the chlorosulfonic acid storage tank 7 for recovery and secondary production. The total conversion rate of ortho, meta, and para-isocyanates is 83.44%, and the TsCl yield is 71.23%.

[0055] Example 4: A continuous synthesis method for p-toluenesulfonyl chloride (Part 3)

[0056] (1) Add 1 mol chlorosulfonic acid, 0.02 mol ammonium chloride and 2 mol dichloroethane to the first static mixer 1 and mix thoroughly at room temperature to obtain mixture A; pump mixture A and 1 mol toluene into the first microreactor 3 under the action of the first metering pump 13 for sulfonation reaction, the reaction time is 300 min and the temperature is controlled at 30℃ to obtain reaction solution;

[0057] (2) The reaction liquid discharged from the outlet of the first microreactor 3 enters the first gas-liquid two-phase separator 4 to obtain HCl gas and liquid containing p-toluenesulfonic acid. The separated HCl gas enters the first falling film absorber 5 to produce hydrochloric acid. The 1 mol of liquid phase containing p-toluenesulfonic acid separated by the first gas-liquid two-phase separator 4 is pumped into the second microreactor 8 by the third metering pump 15. 3 mol of dichloroethane, 0.05 mol of inhibitor (a mixture of acetic acid and isopropionic acid in a molar ratio of 1:1.5) and 0.05 mol of ammonium chloride are added to the second static mixer 6 and mixed at 45°C to obtain mixture B. Mixture B is pumped into the second microreactor 8 together with 2 mol of chlorosulfonic acid and mixed with the liquid containing p-toluenesulfonic acid to obtain a mixture for acyl chloride reaction. The reaction time is 240 min and the temperature is controlled at 60°C.

[0058] (3) The secondary reaction mixture discharged from the second microreactor 8 is separated by the second gas-liquid two-phase separator 9 to obtain HCl gas, sulfonated oil, intermediate layer, and lower layer. The HCl gas enters the second falling film absorber to produce hydrochloric acid, and the sulfonated oil is purified to obtain o-benzenesulfonyl chloride and m-toluenesulfonyl chloride. The lower layer is recovered and sent to the sulfuric acid storage tank 10. The intermediate layer is crystallized by the freeze crystallizer 11 and then centrifuged and filtered by the centrifuge 12. The crude product obtained by filtration is washed and then frozen and crystallized again by the freeze crystallizer 11 to obtain crude p-toluenesulfonyl chloride as the product. The filtrate obtained by filtration is sent to the chlorosulfonic acid storage tank 7 for recovery and secondary production. The total conversion rate of ortho, meta, and para-positions is 90.44%, and the TsCl yield is 80.34%.

[0059] Example 5: A continuous synthesis method for p-toluenesulfonyl chloride (Part 4)

[0060] (1) Add 1 mol chlorosulfonic acid, 0.02 mol ammonium chloride and 2 mol dichloroethane to the first static mixer 1 and mix thoroughly at room temperature to obtain mixture A; pump mixture A and 1 mol toluene into the first microreactor 3 under the action of the first metering pump 13 for sulfonation reaction, the reaction time is 30 min and the temperature is controlled at 60℃ to obtain reaction solution;

[0061] (2) The reaction liquid discharged from the outlet of the first microreactor 3 enters the first gas-liquid two-phase separator 4 to obtain HCl gas and liquid containing p-toluenesulfonic acid. The separated HCl gas enters the first falling film absorber 5 to produce hydrochloric acid. The 1 mol of liquid phase containing p-toluenesulfonic acid separated by the first gas-liquid two-phase separator 4 is pumped into the second microreactor 8 by the third metering pump 15. 3 mol of dichloroethane, 0.1 mol of inhibitor (a mixture of acetic acid and isopropionic acid in a molar ratio of 1:1.5) and 0.1 mol of ammonium chloride are added to the second static mixer 6 and mixed at 30°C to obtain mixture B. Mixture B is pumped into the second microreactor 8 together with 2 mol of chlorosulfonic acid and mixed with the liquid containing p-toluenesulfonic acid to obtain a mixture for acyl chloride reaction. The reaction time is 240 min and the temperature is controlled at 60°C.

[0062] (3) The secondary reaction mixture discharged from the second microreactor 8 is separated by the second gas-liquid two-phase separator 9 to obtain HCl gas, sulfonated oil, intermediate layer, and lower layer. The HCl gas enters the second falling film absorber to produce hydrochloric acid, and the sulfonated oil is purified to obtain o-benzenesulfonyl chloride and m-toluenesulfonyl chloride. The lower layer is recovered and sent to the sulfuric acid storage tank 10. The intermediate layer is crystallized by the freeze crystallizer 11 and then centrifuged and filtered by the centrifuge 12. The crude product obtained by filtration is washed and then frozen and crystallized again by the freeze crystallizer 11 to obtain crude p-toluenesulfonyl chloride as the product. The filtrate obtained by filtration is sent to the chlorosulfonic acid storage tank 7 for recovery and secondary production. The total conversion rate of ortho, meta, and para-isocyanates is 92.24%, and the TsCl yield is 81.68%.

[0063] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for the continuous synthesis of p-toluenesulfonyl chloride, characterized in that, The continuous synthesis device is used for continuous synthesis of p-toluenesulfonyl chloride, The synthesis device comprises a first static mixer (1), a toluene storage tank (2), a first micro-reactor (3), a first gas-liquid two-phase separator (4), a first falling film absorber (5), a second static mixer (6), a chlorosulfonic acid storage tank (7), a second micro-reactor (8), a second gas-liquid two-phase separator (9), a sulfuric acid storage tank (10), a refrigeration crystallizer (11), a centrifuge (12), a first metering pump (13), a second metering pump (14), a third metering pump (15), a fourth metering pump (16), a fifth metering pump (17), a sixth metering pump (18), a first liquid inlet pipe (19), a second liquid inlet pipe (20), a third liquid inlet pipe (21), a fourth liquid inlet pipe (22), a fifth liquid inlet pipe (23), a first connecting pipe (24), a second connecting pipe (25), a third connecting pipe (26), a fourth connecting pipe (27), a fifth connecting pipe (28), an absorption pipe (29), and a second falling film absorber. The first static mixer (1) is connected with the inlet of the first micro-reactor (3) through the first liquid inlet pipe (19), and the first metering pump (13) is arranged on the first liquid inlet pipe (19); the toluene storage tank (2) is connected with the inlet of the first micro-reactor (3) through the second liquid inlet pipe (20), and the second metering pump (14) is arranged on the second liquid inlet pipe (20); and the first micro-reactor (3) is connected with the first gas-liquid two-phase separator (4) through the first connecting pipe (24). The first gas-liquid two-phase separator (4) is provided with two outlets, the first outlet of the first gas-liquid two-phase separator (4) is connected with the first falling film absorber (5) through the absorption pipe (29), and the second outlet of the first gas-liquid two-phase separator (4) is connected with the inlet of the second micro-reactor (8) through the third liquid inlet pipe (21); and the third liquid inlet pipe (21) is provided with the third metering pump (15). The chlorosulfonic acid storage tank (7) is connected with the inlet of the second micro-reactor (8) through the fourth liquid inlet pipe (22), and the fourth metering pump (16) is arranged on the fourth liquid inlet pipe (22); the second static mixer (6) is connected with the second micro-reactor (8) through the fifth liquid inlet pipe (23), and the fifth metering pump (17) is arranged on the fifth liquid inlet pipe (23). The outlet of the second micro-reactor (8) is connected with the second gas-liquid two-phase separator (9) through a second connecting pipe (25); the second gas-liquid two-phase separator (9) is provided with three outlets, the first outlet of the second gas-liquid two-phase separator (9) is connected with a second falling film absorber; the second outlet of the second gas-liquid two-phase separator (9) is connected with the inlet of the sulfuric acid storage tank (10) through the fourth connecting pipe (27), and the fourth connecting pipe (27) is provided with the sixth metering pump (18); the third outlet of the second gas-liquid two-phase separator (9) is connected with the refrigeration crystallizer (11) through the third connecting pipe (26), the refrigeration crystallizer (11) is connected with the centrifugal separator (12) through the third connecting pipe (26), and the centrifugal separator (12) is connected with the second static mixer (6) through the fifth connecting pipe (28); The method specifically comprises the following steps: (1) mixing the one-time added chlorosulfonic acid, catalyst and organic solvent in the first static mixer (1) to obtain a mixed solution A, and pumping the mixed solution A and toluene into the first micro-reactor (3) to react to obtain a reaction solution; (2) discharging the reaction solution from the outlet of the first micro-reactor (3) and separating a liquid phase, pumping the liquid phase, the second-time added chlorosulfonic acid and a mixed solution B in the second static mixer (6) into the second micro-reactor (8) to mix and react to obtain a second-time reaction mixture; (3) discharging the second-time reaction mixture from the second micro-reactor (8) and separating an intermediate layer refrigeration crystallization, filtering and washing to obtain p-toluenesulfonyl chloride; The mixed solution B in step (2) comprises the following materials: catalyst, organic solvent and inhibitor; The catalyst is ammonium chloride; The inhibitor comprises at least one of acetic acid, propionic acid, isopropyl acid, chloroacetic acid and trifluoroacetic acid; the reaction temperature in the first micro-reactor is 25-45 DEG C, and the reaction time is 0-60 min; the reaction temperature of the second micro-reactor is 45-85 DEG C, and the reaction time is 60-300 min.

2. A continuous synthesis of p-toluenesulfonyl chloride according to claim 1, characterized in that, The temperature in the first static mixer (1) is 25-45 DEG C, and the temperature in the second static mixer (6) is 35-65 DEG C.

3. A continuous synthesis of p-toluenesulfonyl chloride according to claim 1, characterized in that, The molar ratio of the liquid phase, the chlorosulfonic acid, the organic solvent, the catalyst and the inhibitor in the mixed solution B in step (2) is 1:1-3.0:1-3.0:0.01-0.22:0.01-0.

3.

4. A continuous synthesis of p-toluenesulfonyl chloride according to claim 1, characterized by, The organic solvent comprises at least one of dichloromethane, trichloromethane and dichloroethane.

5. The process for continuous synthesis of p-toluenesulfonyl chloride as claimed in claim 1, wherein, The steps of the intermediate layer refrigeration crystallization, filtering and washing in step (3) are specifically as follows: separating the intermediate layer through the second gas-liquid two-phase separator (9), refrigeration crystallization through the refrigeration crystallizer (11), centrifugation and filtration through the centrifugal separator (12), and washing the obtained crude product again through the refrigeration crystallizer (11) to obtain the product.

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