A system and process for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid

Abstract

The invention discloses a system and a process for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid, the system includes a jet loop reactor, a circulation pump, a feed pump, a heat exchanger, a gas-liquid separator, a spray absorber, a liquid delivery pump and a crude product tank, the lower end discharge port of the jet loop reactor is connected to the circulation pump and the heat exchanger in sequence, the outlet of the heat exchanger is connected to the feed port of the jet loop reactor, and a circulation loop is formed, the upper end discharge port of the jet loop reactor is connected to the gas-liquid separator by a pipeline, the lower end discharge port of the gas-liquid separator is connected to the crude product tank by a pipeline, the side discharge port of the gas-liquid separator is connected to the spray absorber, and the liquid delivery pump is connected to the spray absorber to form a circulating spray loop, and the cylinder of the jet loop reactor is divided into an upper circulation reaction section and a lower fully mixed reaction section by a partition. The present invention realizes the effect of fully mixing gas and liquid and controlling the depth of chlorination by optimizing the structural design of the jet loop reactor, and the product yield is high and the selectivity is good.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of 4-methyl-5-chlorobenzenesulfonic acid, and particularly relates to a system and a process for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid. Background Art

[0002] 4-Methyl-5-chlorobenzenesulfonic acid is an intermediate product of acid synthesis. It is usually prepared in industry using p-toluenesulfonic acid and chlorine as raw materials and concentrated sulfuric acid as a medium. In this chlorination reaction, the methyl group and the sulfonic acid group have the same positioning effect, so chlorination can only occur at the ortho position of the methyl group, and the formation of isomers is not considered. The chlorination of p-toluenesulfonic acid belongs to the substitution halogenation on the aromatic ring. The most important factor affecting the formation of m-chloro-p-toluenesulfonic acid is the control of the chlorination depth and reaction temperature.

[0003] The existing 4-methyl-5-chlorobenzenesulfonic acid production processes at home and abroad generally use kettle or tower reactors, which have many obvious defects, such as poor gas-liquid mixing effect, low uniformity, low chlorine utilization, low product yield, etc. Chinese patent CN109369469A provides a method for preparing CLT acid chloride by continuous reaction using an injection loop. Although the method uses an injector to mix chlorine with materials, the chlorine residence time is short, the chlorine reaction is incomplete, and the chlorine is wasted.

[0004] The jet loop reactor (JLR) uses the fluid jet principle to form a strong circulation inside the reactor, which can suspend and evenly disperse the materials inside the reactor, achieve full contact between the phases, and achieve efficient multiphase transfer performance. It is particularly beneficial to liquid-liquid, gas-liquid, and gas-liquid-solid multiphase reactions. It is a slurry bed reactor with excellent performance and is widely used in the field of biochemical engineering.

[0005] For traditional jet loop reactors, during industrial scale-up, the height-to-diameter ratio of the loop reactor usually needs to reach more than seven times. For large-scale loop reactors, too high a height-to-diameter ratio will make the liquid level too high, the flow resistance too large, and the required mass transfer kinetic energy large, thereby increasing energy consumption accordingly. In addition, the mass transfer effect will also be reduced, which can easily cause uneven gas phase distribution. Summary of the invention

[0006] The invention aims to overcome the shortcomings in the prior art and propose a system and a process for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid. A jet loop reactor in the system is divided into two regions, namely a lower full mixing reaction section and an upper loop reaction section. The effects of fully mixing gas and liquid and controlling the chlorination depth are achieved by optimizing the structural design of the jet loop reactor. The system is used as a reaction device for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid, and a circulation loop system and a segmented temperature control system are utilized. The chlorine gas is basically reacted completely, the product yield is high, and the selectivity is good.

[0007] The technical solution of the present invention is summarized as follows:

[0008] A system for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid comprises a jet loop reactor, a circulation pump, a feed pump, a heat exchanger, a gas-liquid separator, a spray absorption tower, a liquid delivery pump and a crude product tank. The lower end discharge port of the jet loop reactor is connected to the circulation pump and the heat exchanger in sequence, the outlet of the heat exchanger is connected to the upper end feed port of the jet loop reactor to form a circulation loop, the feed pump is arranged between the pipelines of the circulation pump and the heat exchanger through a pipeline, the upper end discharge port of the jet loop reactor is connected to the gas-liquid separator through a pipeline, the lower end discharge port of the gas-liquid separator is connected to the crude product tank through a pipeline, the side discharge port of the gas-liquid separator is connected to the spray absorption tower through a pipeline, the liquid delivery pump is connected to the spray absorption tower to form a circulation spray loop, and the barrel of the jet loop reactor is divided into an upper circulation reaction section and a lower full mixing reaction section through a partition.

[0009] Furthermore, a plurality of guide tubes are respectively provided in the upper circulation reaction section and the lower full mixing reaction section of the jet circulation reactor, and are distributed in an array inside the jet circulation reactor. A first through hole and a second through hole are provided on the partition, the first through hole is provided at the center of the partition, and the second through holes are evenly distributed on the partition. A guide tube is provided in the second through hole, and a nozzle at the upper end of the guide tube extends upward to the lower end of the guide tube in the upper circulation reaction section. The ejector is a venturi ejector, and the ejector extends from the upper end of the cylinder body and passes through the first through hole to extend into the lower full mixing reaction section. The lower end of the ejector is divided into multiple branches, and nozzles are provided on the branch pipes. The nozzles extend downward to the upper end of the guide tube in the lower full mixing reaction section, and a baffle is provided below the guide tube in the lower full mixing reaction section.

[0010] Furthermore, the ejector includes a central tube and an outer tube, the nozzle end of the central tube is inserted into the outer tube and extends to the diameter change point of the outer tube to form an annular tube structure, the lower end of the outer tube is divided into multiple branches, nozzles are provided on the branches, an air inlet is provided on the outer tube, and the upper end of the central tube is a liquid inlet.

[0011] Furthermore, heat exchange jackets are provided on both inner and outer walls of the draft tube in the upper circulation reaction section, and the heat exchange jackets are provided with inlets and outlets for heat exchange medium.

[0012] Furthermore, the upper port of the nozzle on the guide tube is flush with the lower end surface of the guide tube in the upper circulating reaction section, the lower end of the nozzle at the lower end of the ejector is flush with the upper end surface of the guide tube in the lower fully mixed reaction section, and the caliber of the nozzle on the guide tube is the same as the caliber of the nozzle at the lower end of the ejector.

[0013] Furthermore, the volume of the lower fully mixed reaction section is determined by the fully mixed flow reactor design equation: OK, where F A0 is the molar flow rate of the raw liquid, X is the conversion rate of the lower fully mixed reaction section, -r A is the reaction rate, and the conversion rate X achieved in the lower fully mixed reaction section is 50-90%.

[0014] Furthermore, the jet loop reactor meets the following structural dimension limitations:

[0015] (a) the number n of draft tubes in the upper circulating reaction section and the lower fully mixed reaction section is greater than or equal to 3;

[0016] (b) the height of the upper circulating reaction section is 1-3 times the height of the lower fully mixed reaction section;

[0017] (c) The height of the draft tube is 0.6-0.8 times the height of the reaction section;

[0018] (d) The height of the guide tube is 8-15 times its inner diameter;

[0019] (e) The diameter of the baffle is 0.7-0.9 times the inner diameter of the cylinder

[0020] (f) The vertical distance between the baffle and the lower end of the guide tube is 0.1-0.3 times the inner diameter of the tube.

[0021] Furthermore, the center of the partition is a circular plate, the edge is a 90° arc structure, and it is smoothly connected to the cylinder. According to the computational fluid dynamics simulation of the simulation software COMSOL, the dead zone volume fraction in the reactor satisfies the equation The constant k is related to the reactor structure. Within the specified reactor structure size, the value range of the constant k is 3×10 -5 -9×10 -5 , Re1 is the Reynolds number at the nozzle outlet at the lower end of the ejector (15), and its applicable range is 2×10 4 -6×10 5 , r / R is the ratio of the radius of the arc structure to the radius of the cylinder (11), and the applicable range is 0.3-0.4. When the volume fraction of the dead zone is below 10%, the conversion rate is better, preferably below 3%.

[0022] A process for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid using the above system comprises the following steps:

[0023] 1) The raw material liquid p-toluenesulfonic acid and concentrated sulfuric acid are transported to the heat exchanger through the feed pump, and after being preheated, they enter the ejector through the central tube, and chlorine is introduced through the air inlet of the outer tube, and the gas and liquid phases are mixed in the ejector;

[0024] 2) The mixed materials are ejected from the nozzle at the lower end of the ejector and enter the lower fully mixed reaction section. The gas-liquid two-phase materials descend in the guide tube and turn back at the baffle. Part of the materials rise to the upper opening of the guide tube in the annular gap outside the guide tube, thereby forming a flow circulation in the lower fully mixed reaction section. Part of the materials are discharged from the discharge port at the lower end of the jet loop reactor and then enter the heat exchanger and ejector for circulation;

[0025] 3) The material at the upper end of the lower fully mixed reaction section enters the upper circulation reaction section through the guide pipe. The material forms a multi-stage circulation under the turbulent effect of multiple guide tubes distributed in an array. The fully mixed and reacted material flows out through the discharge port at the top of the jet circulation reactor and enters the gas-liquid separator. The gas phase at the gas phase outlet of the gas-liquid separator enters the spray absorption tower. The liquid delivery pump pumps the clean water at the bottom of the tower into the nozzle at the top of the spray absorption tower for spraying. After absorbing the gas phase, a hydrochloric acid solution is obtained. The liquid phase flowing out from the liquid phase outlet of the gas-liquid separator enters the crude product tank and finally enters the distillation tower for further refining and fractionation to obtain the desired product.

[0026] Furthermore, the temperature of the lower fully mixed reaction section of the jet loop reactor is controlled at 78-82°C, and the temperature of the upper loop reaction section is controlled at 75-78°C.

[0027] The beneficial effects of the present invention are:

[0028] 1) The jet loop reactor provided by the present invention is divided into an upper loop reaction section and a lower full mixing reaction section by a perforated partition. In the lower full mixing reaction section, the gas-liquid two-phase materials form violent turbulence under the driving force of high-speed jetting, so that the gas-liquid two-phase materials are fully mixed. However, since the gas-liquid phase contact time is short, a loop reaction section is designed above the full mixing reaction section to effectively control the gas-liquid phase contact time.

[0029] 2) The partition between the two reaction areas of the jet circulation reactor provided by the present invention adopts an arc structure with a curvature and is smoothly connected to the cylinder, which can improve the circulation and reduce vortices and dead zones. A plurality of guide tubes and a plurality of array nozzles are adopted to make the gas-liquid distribution more uniform, so that a multi-stage circulation is formed in the system, thereby enhancing the local and overall circulation, so that more bubbles are entrained into the reactor annulus and the bottom of the reactor.

[0030] 3) The reaction of p-toluenesulfonic acid and chlorine is a series of reactions that generate polychlorinated substituents. From a kinetic point of view, if the chlorination continues, polychlorinated substituents will also be produced, so the chlorination depth and reaction temperature must be controlled. The use of a segmented reactor can control the chlorination depth of the reaction. External circulation heat exchange is used for the lower fully mixed reaction section, and a heat exchange jacketed draft tube is used for the upper circulating reaction section. Combining the two heat exchange methods, the reaction can be temperature controlled in segments. The above method can reduce the generation of polychlorinated substituents and improve product quality.

[0031] 4) The method utilizes a continuous feeding and discharging method to continuously react and prepare 4-methyl-5-chlorobenzenesulfonic acid. Compared with the existing batch reaction, the production capacity is greatly improved, and the hydrogen chloride gas in the tail gas is absorbed and utilized to produce industrial hydrochloric acid with a higher concentration, thereby achieving zero tail gas emission. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The structure and process diagram of the jet loop reactor of the present invention;

[0033] Figure 2 is a schematic cross-sectional view of a partition of the present invention;

[0034] Figure 3 It is a top view of the upper circulation reaction section;

[0035] Figure 4 It is a schematic diagram of the ejector structure;

[0036] Figure 5 This is the simulated streamline diagram of the jet loop reactor.

[0037] In the figure: 1. jet circulation reactor; 11. cylinder; 12. partition; 121. first through hole; 122. second through hole; 123. flow guide tube; 13. flow guide tube; 14. heat exchange jacket; 15. ejector; 151. center tube; 152. outer tube; 16. baffle; 2. circulation pump; 3. feed pump; 4. heat exchanger; 5. gas-liquid separator; 6. spray absorption tower; 7. liquid delivery pump; 8. crude product tank. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the embodiments and the accompanying drawings, but the protection scope of the present invention is not limited thereto.

[0039] like Figures 1 to 4As shown, a system for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid comprises a jet loop reactor 1, a circulation pump 2, a feed pump 3, a heat exchanger 4, a gas-liquid separator 5, a spray absorption tower 6, a liquid delivery pump 7 and a crude product tank 8. The barrel 11 of the jet loop reactor 1 is divided into an upper loop reaction section and a lower full mixing reaction section by a partition 12. The edge of the partition 12 is an arc structure and is smoothly connected to the barrel 11. The edge arc θ is 90°. A guide tube 13 is respectively arranged in the upper loop reaction section and the lower full mixing reaction section. The partition 12 is provided with a first through hole 121 and a second through hole 122. The first through hole 121 and the second through hole 122 are provided in the partition 12. The through hole 121 is provided at the center of the partition 12, and the second through holes 122 are evenly distributed on the partition 12. The lower end of the flow guide tube 123 is connected to the second through hole 122, and the upper end nozzle extends upward to the lower end of the flow guide tube 13 in the upper circulation reaction section, and the nozzle end thereof is flush with the lower end surface of the flow guide tube 13. The ejector 15 is a Venturi ejector, and the ejector 15 extends from the upper end of the cylinder 11 into and through the first through hole 121, and extends into the lower fully mixed reaction section. The ejector 15 includes a central tube 151 and an outer tube 152, and the nozzle end of the central tube 151 is inserted into the outer tube 152 and extends to the outer tube 1 The diameter change point of the outer tube 152 forms an annular gap tube structure. The lower end of the outer tube 152 is divided into multiple branches, and nozzles are provided on the branch pipes. The outer tube 152 is provided with an air inlet. The upper end of the central tube 151 is a liquid inlet. The nozzles on the branch pipes extend downward to the upper end of the guide tube 13 in the lower fully mixed reaction section, and the lower end of the nozzle is flush with the upper end surface of the guide tube 13. The caliber of the nozzle on the guide tube 123 is the same as the caliber of the nozzle at the lower end of the ejector 15. A baffle 16 is provided below the guide tube 13 in the lower fully mixed reaction section. Heat exchange jackets 14 are provided on the inner and outer walls of the guide tube 13 in the upper annular reaction section. The heat exchange jacket 14 An inlet and outlet for heat exchange medium are arranged on the top, the lower end discharge port of the jet loop reactor 1 is connected to the circulation pump 2 and the heat exchanger 4 in sequence, the outlet of the heat exchanger 4 is connected to the upper end feed port of the central pipe 151 to form a circulation loop, the feed pump 3 is arranged between the circulation pump 2 and the pipeline of the heat exchanger 4 through a pipeline, the upper end discharge port of the cylinder 11 of the jet loop reactor 1 is connected to the gas-liquid separator 5 through a pipeline, the lower end discharge port of the gas-liquid separator 5 is connected to the crude product tank 8 through a pipeline, the side discharge port of the gas-liquid separator 5 is connected to the spray absorption tower 6 through a pipeline, and the liquid delivery pump 7 is connected to the spray absorption tower 6 to form a circulation loop.

[0040] Example 1

[0041] The volume flow rate of the raw liquid (p-toluenesulfonic acid and concentrated sulfuric acid are 1:1) entering the liquid phase inlet of the ejector 15 is v0 = 7.68m 3 / h, where the molar flow rate of p-toluenesulfonic acid is F A0is 1.39 mol / s, the molar flow rate of chlorine entering the gas phase inlet of the ejector 15 is 1.45 mol / s, the average temperature of the lower fully mixed reaction section is 78°C, the average temperature of the upper loop reaction section is 75°C, and the reaction rate of p-toluenesulfonic acid and chlorine is -r A =3.65mol / m 3 ·s (reaction rate at a reaction temperature of 78°C), the conversion rate X of the lower fully mixed reaction section is 0.7, the inner diameter R of the cylinder 11 is 0.5m, the number of guide tubes n in the upper and lower regions is 4, and the volume of the lower fully mixed reaction section is given by the formula, Calculated V = 0.267m 3 , the height of the lower fully mixed reaction section is calculated to be 1.36m, the height of the upper circulating reaction section is 1.8m, the height of the guide tube 13 in the upper circulating reaction section is 1.3m, the height of the guide tube 13 in the lower fully mixed reaction section is 0.86m, the inner diameter of the guide tube 13 is 0.1m, the diameter of the baffle 16 is 0.4m, the vertical distance between the baffle 16 and the lower end of the guide tube 13 is 0.06m, the nozzle diameter at the lower end of the ejector 15 and the nozzle diameter on the guide tube 123 are both 0.01m, and the outlet flow rate of each nozzle at the lower end of the ejector 15 is u1=6.8m / s. From the density of the raw material liquid (the volume ratio of p-toluenesulfonic acid to concentrated sulfuric acid is 1:1) ρ=1.54g / cm 3 , viscosity μ = 1.46 × 10 -3 Pa·s, the Reynolds number Re1 of the nozzle outlet at the lower end of the ejector is calculated to be 71726. The fluid behavior of the reactor with the above structural dimensions is analyzed by the simulation software COMSOL. The dead zone volume fraction in the reactor satisfies the equation like Figure 5 As shown in a, the ratio r / R of the arc structure radius to the radius of the cylinder (11) is 0.2. From the simulated streamline diagram, it can be seen that a vortex appears at the edge of the arc. According to the above equation, the dead zone volume fraction α is 3.3%.

[0042] The specific steps are as follows:

[0043] 1) The raw material liquid p-toluenesulfonic acid and concentrated sulfuric acid are transported to the heat exchanger 4 through the feed pump 3, and after being preheated, they enter the ejector 15 through the central tube 151, and chlorine gas is introduced through the air inlet of the outer tube 152, and the gas and liquid phases are mixed in the ejector 15;

[0044] 2) The mixed material is ejected from the nozzle at the lower end of the ejector 15 and enters the lower fully mixed reaction section. The gas-liquid two-phase material descends in the guide tube 13 and turns back at the baffle 16. Part of the material rises in the outer annular gap of the guide tube 13 to the upper end of the guide tube 13, thereby forming a flow circulation in the lower fully mixed reaction section. Part of the material is discharged from the discharge port at the lower end of the jet loop reactor 1, and then enters the heat exchanger 4 and the ejector 15 for circulation;

[0045] 3) The material at the upper end of the lower fully mixed reaction section enters the upper circulation reaction section through the guide pipe 123. The material forms a multi-stage circulation under the turbulent effect of the multiple array-distributed guide tubes 13. The fully mixed and reacted material flows out through the discharge port at the top of the jet circulation reactor 1 and enters the gas-liquid separator 5. The gas phase at the gas phase outlet of the gas-liquid separator 5 enters the spray absorption tower 6. The liquid delivery pump 7 pumps the clean water at the bottom of the tower into the nozzle at the top of the spray absorption tower 6 for spraying. After absorbing the gas phase, a hydrochloric acid solution is obtained. The liquid phase flowing out from the liquid phase outlet of the gas-liquid separator 5 enters the crude product tank 9, and finally enters the distillation tower for further refining and fractionation to obtain the desired product.

[0046] After the whole process system was started and stabilized, sampling and analysis were carried out at the top material outlet, and high performance liquid chromatography was used for analysis and detection, and the conversion rate of p-toluenesulfonic acid was 97.5%, and the yield of product 4-methyl-5-chlorobenzenesulfonic acid was 95.8%.

[0047] Example 2

[0048] The process parameters, operation method and structural dimensions of the jet loop reactor 1 of this embodiment are the same as those of the embodiment 1, except that the ratio r / R of the radius of the arc structure to the radius of the cylinder 11 is 0.3. Figure 5 As shown in b, the simulated streamline diagram shows that there is almost no vortex at the edge of the arc, and a small vortex appears at the bottom of the guide tube. According to the equation The dead zone volume fraction α was obtained to be 1.46%. After the whole process system was started and stabilized, sampling and analysis were carried out at the top material outlet. The high performance liquid chromatography was used for analysis and detection, and the conversion rate of p-toluenesulfonic acid was 98.1%, and the yield of the product 4-methyl-5-chlorobenzenesulfonic acid was 96.1%.

[0049] Example 3

[0050] The process parameters, operation method and structural dimensions of the jet loop reactor 1 of this embodiment are the same as those of the embodiment 1, except that the ratio r / R of the arc structure radius to the radius of the cylinder 11 is 0.4. Figure 5 As shown in c, the simulated streamline diagram shows that there is almost no vortex near the partition. According to the equation

[0051] The dead zone volume fraction α is obtained as 0.82%.

[0052] After the whole process system was started and stabilized, sampling and analysis were carried out at the top material outlet, and high performance liquid chromatography was used for analysis and detection, and the conversion rate of p-toluenesulfonic acid was 98.8%, and the yield of product 4-methyl-5-chlorobenzenesulfonic acid was 96.5%.

[0053] Comparative Example:

[0054] The structural dimensions and process parameters of the jet loop reactor 1 of this embodiment are the same as those of the above-mentioned embodiment 3, except that the average temperatures of the lower fully mixed reaction section and the upper loop reaction section are controlled to be 78°C. After the system temperature stabilizes, sampling and analysis are carried out at the top material outlet. Analysis and detection by high performance liquid chromatography show that the conversion rate of p-toluenesulfonic acid is 98.9%, and the yield of the product 4-methyl-5-chlorobenzenesulfonic acid is 93.0%.

[0055] Conclusion: Through the results of the embodiments and comparative examples, it can be seen that the segmented temperature control of the upper circulating reaction section and the lower fully mixed reaction section with the partition 12 as the boundary can reduce the formation of polychlorinated substitutions while ensuring that the conversion rate of p-toluenesulfonic acid remains almost unchanged, thereby increasing the yield of the product 4-methyl-5-chlorobenzenesulfonic acid.

Claims

1. A system for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid, characterized in that The invention comprises a jet loop reactor (1), a circulation pump (2), a feed pump (3), a heat exchanger (4), a gas-liquid separator (5), a spray absorption tower (6), a liquid delivery pump (7) and a crude product tank (8). The lower end discharge port of the jet loop reactor (1) is connected to the circulation pump (2) and the heat exchanger (4) in sequence, and the outlet of the heat exchanger (4) is connected to the upper end feed port of the jet loop reactor (1) to form a circulation loop. The feed pump (3) is arranged between the circulation pump (2) and the heat exchanger (4) through a pipeline. The upper discharge port of the jet loop reactor (1) is connected to the gas-liquid separator (5) through a pipeline, the lower discharge port of the gas-liquid separator (5) is connected to the crude product tank (8) through a pipeline, the side discharge port of the gas-liquid separator (5) is connected to the spray absorption tower (6) through a pipeline, and the liquid delivery pump (7) is connected to the spray absorption tower (6) to form a circulating spray loop, and the barrel (11) of the jet loop reactor (1) is divided into an upper circulating reaction section and a lower fully mixed reaction section by a partition (12); A plurality of flow guide tubes (13) are respectively arranged in an upper loop reaction section and a lower fully mixed reaction section of the jet loop reactor (1), and are arranged in an array inside the jet loop reactor (1); a first through hole (121) and a second through hole (122) are arranged on the partition plate (12); the first through hole (121) is arranged at the center of the partition plate (12); the second through holes (122) are evenly distributed on the partition plate (12); a flow guide tube (123) is arranged in the second through hole (122); and the upper end of the flow guide tube (123) is provided with a The nozzle extends upward to the lower end of the guide tube (13) in the upper circulation reaction section. The ejector (15) is a Venturi ejector. The ejector (15) extends from the upper end of the cylinder (11) into and through the first through hole (121) to extend into the lower fully mixed reaction section. The lower end of the ejector (15) is divided into multiple branch pipes. The branch pipes are provided with nozzles. The nozzles extend downward to the upper end of the guide tube (13) in the lower fully mixed reaction section. A baffle (16) is provided below the guide tube (13) in the lower fully mixed reaction section. The ejector (15) comprises a central tube (151) and an outer tube (152); the nozzle end of the central tube (151) is inserted into the outer tube (152) and extends to the diameter change position of the outer tube (152) to form an annular tube structure; the lower end of the outer tube (152) is divided into multiple branch tubes, each branch tube is provided with a nozzle; the outer tube (152) is provided with an air inlet, and the upper end of the central tube (151) is a liquid inlet; A heat exchange jacket (14) is provided on both the inner and outer walls of the flow guide tube (13) in the upper circulation reaction section, and an inlet and outlet of a heat exchange medium are provided on the heat exchange jacket (14).

2. A system for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid as claimed in claim 1, characterized in that The upper port of the nozzle on the flow guide tube (123) is flush with the lower end surface of the flow guide tube (13) in the upper circulating reaction section, the lower end of the nozzle at the lower end of the ejector (15) is flush with the upper end surface of the flow guide tube (13) in the lower fully mixed reaction section, and the caliber of the nozzle on the flow guide tube (123) is the same as the caliber of the nozzle at the lower end of the ejector (15).

3. A system for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid as claimed in claim 2, characterized in that The volume of the lower fully mixed reaction section is determined by the fully mixed flow reactor design equation OK, where F A0 is the molar flow rate of the raw liquid, X is the conversion rate of the lower fully mixed reaction section, -r A is the reaction rate, and the conversion rate X achieved in the lower fully mixed reaction section is 50-90%.

4. A system for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid as claimed in claim 3, characterized in that The jet loop reactor (1) meets the following structural dimension restrictions: (a) the number n of draft tubes (13) in the upper circulating reaction section and the lower fully mixed reaction section is greater than or equal to 3; (b) the height of the upper circulating reaction section is 1-3 times the height of the lower fully mixed reaction section; (c) the height of the draft tube (13) is 0.6-0.8 times the height of the reaction section; (d) The height of the guide tube (13) is 8-15 times its inner diameter; (e) The diameter of the baffle (16) is 0.7-0.9 times the inner diameter of the cylinder (11) (f) The vertical distance between the baffle (16) and the lower end of the guide tube (13) is 0.1-0.3 times the inner diameter of the tube body (11).

5. A system for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid as claimed in claim 4, characterized in that The center of the partition (12) is a circular plate, and the edge is a 90° arc structure, which is smoothly connected to the cylinder (11). The volume fraction of the dead zone in the reactor is estimated by: Wherein k is a constant related to the reactor structure, Re1 is the Reynolds number at the nozzle outlet at the lower end of the ejector (15), r / R is the ratio of the radius of the arc structure to the radius of the cylinder (11), and the value range of the constant k is 3×10 -5 -9×10 -5 , the value range of Re1 is 2×10 4 -6×10 5 , the value range of r / R is 0.2-0.5, and the volume fraction of the dead zone should be less than 10%.

6. A process for continuously preparing 4-methyl-5-chlorobenzenesulfonic acid using the system as claimed in claim 5, characterized in that The steps include: 1) The raw material liquid p-toluenesulfonic acid and concentrated sulfuric acid are transported to the heat exchanger (4) through the feed pump (3), and after being preheated, they enter the ejector (15) through the central tube (151), and chlorine gas is introduced through the air inlet of the outer tube (152), and the gas and liquid phases are mixed in the ejector (15); 2) The mixed materials are ejected from the nozzle at the lower end of the ejector (15) and enter the lower fully mixed reaction section. The gas-liquid two-phase materials descend in the guide tube (13) and are turned back at the baffle (16). Part of the materials rise in the annular gap outside the guide tube (13) to the upper end of the guide tube (13), thereby forming a flow circulation in the lower fully mixed reaction section. Part of the materials are discharged from the discharge port at the lower end of the jet loop reactor (1), and then enter the heat exchanger (4) and the ejector (15) for circulation; 3) The material at the upper end of the lower fully mixed reaction section enters the upper circulation reaction section through the draft tube (123). The material forms a multi-stage circulation under the turbulent effect of the draft tubes (13) distributed in a plurality of arrays. The fully mixed and reacted material flows out through the discharge port at the top of the jet circulation reactor (1) and enters the gas-liquid separator (5). The gas phase at the gas phase outlet of the gas-liquid separator (5) enters the spray absorption tower (6). The liquid delivery pump (7) pumps the clean water at the bottom of the tower into the top nozzle of the spray absorption tower (6) for spraying. After the gas phase is absorbed, a hydrochloric acid solution is obtained. The liquid phase flowing out from the liquid phase outlet of the gas-liquid separator (5) enters the crude product tank (8) and finally enters the distillation tower for further refining and fractionation to obtain the desired product.

7. The process according to claim 6, characterized in that The temperature of the lower fully mixed reaction section of the jet loop reactor (1) is controlled at 78-82°C, and the temperature of the upper loop reaction section is controlled at 75-78°C.

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