A method and apparatus for the continuous chlorination of a pesticide intermediate

Abstract

The present application relates to the technical field of pesticide intermediate production, and discloses a continuous chlorination reaction method and equipment for pesticide intermediates, which comprises the following steps: dehydrating and preheating ortho-nitrotoluene raw materials to 60-70 DEG C; continuously injecting a 10-15wt% ferric chloride / dilute hydrochloric acid solution filtered into a reaction system; and feeding the ortho-nitrotoluene pretreated in step a, the ferric chloride solution in step b and dry chlorine into the reaction equipment at flow rates of 8-10 L / h, 1.0-1.5 L / h and 0.8-1.0 m 3 / h respectively, controlling the reaction temperature to be 60-70 DEG C, the system pressure to be 0.4-0.6 MPa and the residence time to be 30-40 min. The present application has the following advantages and effects: full-automatic regulation and control from raw material dehydration to tail gas discharge are realized, the needs of automatic chlorination production are met, efficient mass transfer and heat transfer are realized, a multi-interface mode is adopted, gas-liquid two-phase segmented mixing is realized, the reaction efficiency is improved, the dichloro-substitution side reaction is inhibited through multi-stage temperature control, and the selectivity of monochloro-substitution products is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pesticide intermediate production, in particular to a pesticide intermediate continuous chlorination reaction method and equipment. BACKGROUND

[0002] With the challenges of global population growth and climate change, food security has become a global focus. Pesticide intermediates, as key elements in pesticide production, help to ensure the stability and sustainability of food production by improving the efficiency and safety of pesticides. High-efficiency pesticides can reduce the damage of pests and diseases to crops, thereby increasing food production and ensuring adequate and stable food supply.

[0003] In the synthesis process of pesticide intermediate methyl aniline, chlorination reaction is a key step. Currently, pesticide intermediates in the industry are mainly implemented by batch chlorination process or micro-channel continuous chlorination process. However, in the long-term production operation, it is gradually found that the batch chlorination process has poor efficiency and generates many by-products, while the micro-channel continuous process has fast catalyst deactivation, poor equipment reliability, lack of real-time quality monitoring means, and is difficult to achieve closed-loop control.

[0004] Based on the above situation, the present inventors propose a pesticide intermediate continuous chlorination reaction method and equipment to improve the current problems. SUMMARY

[0005] The purpose of the present application is to provide a pesticide intermediate continuous chlorination reaction method and equipment with high reaction efficiency and automatic precision.

[0006] The above technical purpose of the present application is achieved by the following technical scheme: a pesticide intermediate continuous chlorination reaction method, which comprises the following steps:

[0007] Step a: dehydrate the o-nitrotoluene raw material and preheat it to 60-70℃;

[0008] Step b: continuously inject the filtered 10-15 wt% ferric chloride / dilute hydrochloric acid solution into the reaction system;

[0009] Step c: pass the o-nitrotoluene pretreated in step a, the ferric chloride solution in step b and dry chlorine gas into the reaction equipment at flow rates of 8-10 L / h, 1.0-1.5 L / h and 0.8-1.0 m³ / h, respectively, control the reaction temperature at 60-70℃, the system pressure at 0.4-0.6 MPa, and the residence time at 30-40 minutes;

[0010] Step d: gas-liquid separation of the reaction mixture, online analysis of the liquid phase product, and two-stage alkali washing of unreacted chlorine and hydrogen chloride gas.

[0011] Step e: continuously remove ferrous ion impurities in the ferric chloride solution by an electrodialysis module, maintain the Fe2+ concentration ≤ 50 ppm, and perform product analysis.

[0012] The further setting of the application is that the molar ratio of the chlorine gas to the o-nitrotoluene is 1.05:1 to 1.1:1.

[0013] The further setting of the application is that the moisture content of the o-nitrotoluene after dehydration is ≤0.1%.

[0014] The further setting of the application is that the operating current density of the electrodialysis module is 15-25 mA / cm2, the regeneration cycle is operated once every 48-72 hours, and the molar ratio of Fe3+ / Fe2+ in the ferric chloride solution after regeneration is ≥200:1.

[0015] A continuous chlorination reaction equipment for pesticide intermediates comprises a raw material pretreatment system, a reaction system, a catalyst injection system, a chlorine gas distribution system, a gas-liquid separation tank and a tail gas treatment system, the raw material pretreatment system is sequentially connected with the reaction system, the gas-liquid separation tank and the tail gas treatment system through pipelines in sequence, the output ends of the catalyst injection system and the chlorine gas distribution system are connected with the reaction system, the raw material pretreatment system comprises a dehydration tank, a dehydration treatment module connected with the dehydration tank and a preheater, and the reaction system comprises a tubular reactor and a cooling system and a reaction module arranged on the tubular reactor.

[0016] The further setting of the application is that the dehydration treatment module comprises a feed pipe with a fixed outer wall and the dehydration tank, a positioning sleeve arranged below the feed pipe and dehydration balls in sliding contact with the outer wall of the positioning sleeve, hot nitrogen inlet pipes and rotating mechanisms arranged on the dehydration balls, and the dehydration balls are used for placing A molecular sieves, the dehydration balls are rotated by the rotating mechanisms after the hot nitrogen inlet pipes are introduced into the dehydration balls.

[0017] The reaction module comprises sequentially connected reaction tubes and isothermal tubes, and heat insulation sheets are arranged between the reaction tubes and the isothermal tubes.

[0018] By adopting the above technical scheme, the step-by-step heating is formed, and the axial temperature coupling interference is reduced.

[0019] The further setting of the application is that leakage holes are arranged on the surface of the dehydration balls, protruding blocking strips are fixedly arranged on the inner wall bottom surface of the dehydration balls, exchange holes are arranged on the surface of the blocking strips, and sealing structures are arranged between the adjacent surfaces of the positioning sleeve and the dehydration balls.

[0020] By adopting the above technical scheme, when the dehydration balls rotate, the water flowing out from the inside of the dehydration balls can be blocked, and the hot nitrogen gas adsorption drying is assisted.

[0021] The further arrangement of the present application is that the input end of the cooling system corresponds to the position of the heterothermic tube, and the cooling system comprises a circulating tube connected with the inside of the reaction system, a three-way valve connected with the input end of the circulating tube, and an external pipe connected with the input end of the three-way valve.

[0022] By adopting the above technical scheme, the cooling liquid can be sent into the heterothermic tube area.

[0023] The further arrangement of the present application is that the preheater is connected with a water content sensor and a positioning sleeve in sequence above, the catalyst injection system comprises a storage tank, an acid-resistant diaphragm pump and an electric conductivity detector connected in sequence through pipes, and the output end of the electric conductivity detector is connected with the pipe reactor through a pipe.

[0024] By adopting the above technical scheme, the FeCl3 / HCl solution can flow into the first-stage reaction tube to react with o-nitrotoluene at low temperature.

[0025] The further arrangement of the present application is that the chlorine distribution system comprises a titanium sintering head and a control monitoring module connected in sequence through pipes, the control monitoring module is connected with the pipe reactor through a pipe below, and the gas-liquid separation tank comprises a gas-liquid separation tank pipe connected with the output end of the pipe reactor, an automatic sampler is arranged at the discharge end of the gas-liquid separation tank pipe, and the gas-liquid separation tank pipe is connected with the tail gas treatment system through a tail gas exhaust pipe.

[0026] By adopting the above technical scheme, the automatic sampler collects samples every minute, and the tail gas is sent into the tail gas treatment system through the tail gas exhaust pipe.

[0027] The present application has the following beneficial effects:

[0028] 1. Full-automatic control from dehydration of raw materials to tail gas discharge is realized, and the needs of automatic chlorination production are met.

[0029] 2. Efficient mass transfer and heat transfer are realized, a multi-interface mode is adopted, gas-liquid two-phase segmented mixing is realized, reaction efficiency is improved, a multi-stage temperature control mode is adopted to inhibit the dichloro-substituted side reaction, and the selectivity of monochloro-substituted products is improved.

[0030] 3. It is beneficial to environmental protection, reduces the generation of reaction byproducts, optimizes reaction safety, and realizes harmless treatment of tail gas, and is suitable for large-scale green production. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0032] Figure 1 A structural schematic diagram of a pesticide intermediate continuous chlorination reaction equipment provided in an embodiment of the present application is shown in the figure;

[0033] Figure 2 A structural schematic diagram of each system in the embodiment of the present application is shown in the figure;

[0034] Figure 3 A structural schematic diagram of a dehydration tank in the embodiment of the present application is shown in the figure;

[0035] Figure 4 A structural schematic diagram of a rotating mechanism in the embodiment of the present application is shown in the figure;

[0036] Figure 5 A structural schematic diagram of a sealing structure in the embodiment of the present application is shown in the figure;

[0037] Figure 6 A structural schematic diagram of a tubular reactor in the embodiment of the present application is shown in the figure.

[0038] In the figure, 1, raw material pretreatment system; 2, reaction system; 3, catalyst injection system; 4, chlorine distribution system; 5, gas-liquid separation tank; 11, dehydration tank; 12, preheater; 13, feed pipe; 14, positioning sleeve; 15, dehydration ball; 16, hot nitrogen inlet pipe; 17, rotating mechanism; 18, moisture sensor; 111, partition; 141, through hole; 142, embedded ring; 151, leakage hole; 152, blocking bar; 153, exchange hole; 154, embedded hole; 171, rotating rod; 172, gear; 173, rack; 174, support rod; 175, push cylinder; 21, tubular reactor; 22, cooling system; 211, heater; 221, circulation pipe; 222, three-way valve; 223, external pipe; 231, heat insulation sheet; 231, reaction tube; 232, different temperature pipe; 233, heat insulation sheet; 31, storage tank; 32, acid-resistant diaphragm pump; 33, conductivity detector; 41, titanium sintering head; 42, control monitoring module; 51, gas-liquid separation tank pipe; 52, automatic sampler; 53, tail gas discharge pipe. DETAILED DESCRIPTION

[0039] The technical solutions of the present application will be described clearly and completely in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0040] The embodiment of the present application specifically provides a pesticide intermediate continuous chlorination reaction method, which comprises the following steps:

[0041] Step a: dehydrating the o-nitrotoluene raw material and preheating to 60-70℃;

[0042] Step b: continuously inject the filtered ferric chloride / dilute hydrochloric acid solution with a concentration of 10-15 wt% into the reaction system;

[0043] Step c: pass the pretreated o-nitrotoluene of step a, the ferric chloride solution of step b, and dry chlorine gas into the reaction equipment at flow rates of 8-10 L / h, 1.0-1.5 L / h, and 0.8-1.0 m³ / h, respectively, control the reaction temperature at 60-70°C, the system pressure at 0.4-0.6 MPa, and the residence time at 30-40 minutes;

[0044] Step d: perform gas-liquid separation on the reacted mixture, collect the liquid phase product after online analysis, and treat the unreacted chlorine and hydrogen chloride gas with two-stage alkali washing;

[0045] Step e: continuously remove the ferrous ion impurities in the ferric chloride solution through an electrodialysis module, maintain the Fe²⁺ concentration at ≤50 ppm, and perform product analysis to extend the service life of FeCl3.

[0046] wherein the molar ratio of chlorine gas to o-nitrotoluene is 1.05:1 to 1.1:1.

[0047] wherein the water content of the dehydrated o-nitrotoluene is ≤0.1%.

[0048] wherein the operating current density of the electrodialysis module is 15-25 mA / cm², the regeneration cycle is operated once every 48-72 hours, and the Fe³⁺ / Fe²⁺ molar ratio in the ferric chloride solution after regeneration is ≥200:1.

[0049] Further, the continuous chlorination reaction method for pesticide intermediates also includes a reaction equipment, please refer to Figures 1-6 The structure includes a raw material pretreatment system 1, a reaction system 2, a catalyst injection system 3, a chlorine gas distribution system 4, a gas-liquid separation tank 5, and a tail gas treatment system.

[0050] Specifically, the raw material pretreatment system 1 is sequentially connected to the reaction system 2, the gas-liquid separation tank 5, and the tail gas treatment system through pipelines, the liquid phase o-nitrotoluene is delivered into the raw material pretreatment system 1 by a corrosion-resistant centrifugal pump, and the flow rate is set at 8-10 L / h, and the heating temperature of the delivery pipeline can be set at 62-68°C.

[0051] The output ends of the catalyst injection system 3 and the chlorine gas distribution system 4 are connected to the reaction system 2, the catalyst injection system 3 is mainly used for injecting the FeCl3 / HCl solution, the raw material pretreatment system 1 includes a dehydration tank 11, a dehydration treatment module connected to the dehydration tank 11, and a preheater 12, and the reaction system 2 includes a tubular reactor 21 and a cooling system 22 and a reaction module arranged on the tubular reactor 21.

[0052] The dehydration treatment module comprises an inlet pipe 13 fixed to the outer wall of the dehydration tank 11, a positioning sleeve 14 arranged below the inlet pipe 13, and a dehydration ball 15 in sliding contact with the outer wall of the positioning sleeve 14. The inner wall of the positioning sleeve 14 is in a spherical structure, so that the outer wall of the dehydration ball 15 can be in sliding contact with the positioning sleeve 14.

[0053] The inlet pipe 13 is used to be connected with a liquid-phase o-nitro-toluene conveying pipeline. The positioning sleeve 14 is arranged in two parts, and is symmetrically distributed above and below the center of the dehydration ball 15. An upper positioning sleeve 14 is provided with a through hole 141. The bottom end of the inlet pipe 13 is coaxially fixed to the positioning sleeve 14. The through hole 141 is coaxially arranged with the inlet pipe 13, so that the liquid-phase o-nitro-toluene can smoothly flow into the dehydration ball 15 after passing through the inlet pipe 13.

[0054] In the implementation, the dehydration ball 15 is provided with a hot nitrogen inlet pipe 16 and a rotating mechanism 17. The outer wall of the hot nitrogen inlet pipe 16 is in rotating contact with the dehydration ball 15, and the outer wall of the hot nitrogen inlet pipe 16 is fixed to the dehydration tank 11. The hot nitrogen inlet pipe 16 is provided with a rotating sealing element 161 adjacent to the dehydration ball 15. The rotating sealing element 161 is a prior art and can be obtained by customization. The rotating sealing element 161 is used to improve the air tightness of the connection between the hot nitrogen inlet pipe 16 and the dehydration ball 15. The outer end of the hot nitrogen inlet pipe 16 is connected with a hot nitrogen gas conveying pipeline to input nitrogen into the dehydration tank 11.

[0055] The dehydration ball 15 is used to place 3A molecular sieve. The 3A molecular sieve selectively adsorbs water molecules and does not adsorb o-nitro-toluene, so as to dehydrate the o-nitro-toluene.

[0056] After the hot nitrogen inlet pipe 16 is introduced into the dehydration ball 15, the dehydration ball 15 is rotated by the rotating mechanism 17. The hot nitrogen gas is used to blow off the water molecules. The temperature of the hot nitrogen gas is controlled at 200℃, so as to regenerate the 3A molecular sieve after absorbing water, thereby improving the service life. The regeneration cycle is once every 48 hours. The inner wall of the dehydration tank 11 should be connected with a hot nitrogen gas output pipeline, so that the hot nitrogen gas can be sent out through the output pipeline after being blown out of the dehydration ball 15.

[0057] Specifically, the dehydration ball 15 is provided with a leakage hole 151 on the surface, and a protruding blocking strip 152 is fixed to the inner wall of the dehydration ball 15. The leakage hole 151 is respectively corresponding to the through hole 141 of the positioning sleeve 14. The lower positioning sleeve 14 is connected with the conveying pipeline. When the o-nitro-toluene is sent into the through hole 141 of the upper positioning sleeve 14 through the inlet pipe 13, and falls into the dehydration ball 15 through the leakage hole 151 to be dehydrated, the dehydrated o-nitro-toluene flows into the conveying pipeline from the through hole 141 of the lower positioning sleeve 14.

[0058] The surface of the blocking strip 152 is provided with an exchange hole 153. When the dewatering ball 15 rotates, the 3A molecular sieve is driven by the blocking strip 152 to vibrate and fall in the dewatering ball 15, thereby improving the contact effect with the hot nitrogen gas. When the o-nitrotoluene contacts the 3A molecular sieve, the o-nitrotoluene can gradually flow to the leakage hole 151 below through the exchange hole 153.

[0059] Further, to help the dewatering ball 15 rotate, the inside bottom surface of the dewatering tank 11 is fixedly provided with a baffle 111 extending upward. The rotating mechanism 17 comprises a rotating rod 171 rotationally connected to the baffle 111, a gear 172 coaxially fixed to one end of the rotating rod 171 away from the dewatering ball 15, a rack 173 meshing with the outer side of the gear 172, a support rod 174 fixedly connected to the top end of the rack 173, and a push cylinder 175 fixedly connected to the support rod 174. The bottom end of the push cylinder 175 is fixed to the dewatering tank 11. The rotating rod 171 is fixedly connected to the outer wall of the dewatering ball 15. The rotating rod 171 is coaxial with the hot nitrogen inlet pipe 16. When the rotating rod 171 drives the dewatering ball 15 to rotate, the hot nitrogen inlet pipe 16 is coaxial with the rotating fulcrum of the dewatering ball 15.

[0060] In implementation, the push cylinder 175 drives the piston rod to move up and down, so that the rack 173 repeatedly pushes the gear 172 upward or downward to reverse, thereby making the dewatering ball 15 reverse and oscillating the 3A molecular sieve in it, and then the push cylinder 175 makes the dewatering ball 15 reset.

[0061] Specifically, to improve the internal sealing of the dewatering ball 15 when rotating, a sealing structure is arranged between the adjacent surfaces of the positioning sleeve 14 and the dewatering ball 15. The sealing structure comprises an embedded ring 142 fixedly arranged on the inner wall of the positioning sleeve 14. The embedded ring 142 is provided with two parts and is spaced apart on the left and right parts of the dewatering ball 15. The surface of the dewatering ball 15 is provided with an embedded hole 154 corresponding to the position of the embedded ring 142. The embedded ring 142 is rotationally arranged in the embedded hole 154 and is attached to the inner wall of the embedded hole 154. The embedded ring 142 is coaxial with the rotating rod 171. Thus, when the dewatering ball 15 rotates, the water flowing out from the inside of the dewatering ball 15 can be blocked, and the hot nitrogen gas can be adsorbed and dried.

[0062] Further, the reaction module comprises a reaction tube 231 and an isothermal tube 232 connected in sequence. The outer wall of the reaction tube 231 is provided with an electric heating module for heating the reaction tube 231. A heat insulation sheet 233 is arranged between the reaction tube 231 and the isothermal tube 232. The number of the reaction tube 231 is three sections, and the isothermal tube 232 has two ends. The input end of the first section and the output end of the third section are respectively connected to the raw material pretreatment system 1 and the gas-liquid separation tank 5. The reaction tube 231 and the isothermal tube 232 are coaxial.

[0063] The material of the heat insulation sheet 233 is ceramic fiber material, the thermal resistance is > 1 m2·K / W, which has strong heat resistance and can reduce the heat conduction performance between the reaction tube 231 and the heterogeneous temperature tube 232. The outer side of the heat insulation sheet 233 is fixedly connected with the inner wall of the tubular reactor 21, so that the areas where the reaction tube 231 and the heterogeneous temperature tube 232 are located can be separated from each other, forming a stepped heating, reducing the axial temperature coupling interference.

[0064] The input end of the cooling system 22 corresponds to the position of the heterogeneous temperature tube 232, and the cooling system 22 comprises a circulating pipe 221 connected with the inside of the reaction system 2, a three-way valve 222 connected with the input end of the circulating pipe 221, and an external pipe 223 connected with the input end of the three-way valve 222. The tubular reactor 21 is provided with a cooling system 22 on each side, and the circulating pipes 221 on both sides are communicated with the areas of the heterogeneous temperature tube 232 inside the tubular reactor 21, so that the cooling liquid can be sent into and out of the heterogeneous temperature tube 232 area for circulation.

[0065] In implementation, from left to right, the temperature gradient control range of the reaction tube 231 and the heterogeneous temperature tube 232 is: 70℃→68℃→65℃→63℃→60℃, so that the reaction liquid can be gradually cooled when flowing from the reaction tube 231 into the heterogeneous temperature tube 232, so as to reduce the situation that FeCl3 solution may crystallize when the temperature difference between the reaction tube 231 and the heterogeneous temperature tube 232 is > 5℃ when the reaction liquid flows out of the reaction tube 231.

[0066] The preheater 12 is connected with the water content sensor 18 and the positioning sleeve 14 in sequence, and a three-way electronic valve is arranged between the water content sensor 18 and the preheater 12. The water content sensor 18 is used to monitor the water content of the material at the outlet of the positioning sleeve 14 in real time. If the water content is > 0.1%, the electronic valve is triggered to close the lower pipeline, so that the raw material cannot flow to the preheater 12. The three-way valve is used to open and close the pipeline, so that the external dehydration tower can extract and process the unreasonable material, thereby improving the reaction accuracy and reducing the risk of failure.

[0067] If the water content is qualified, the raw material is heated by the preheater 12 and then sent to the inside of the tubular reactor 21.

[0068] In implementation, the catalyst injection system 3 comprises a storage tank 31, an acid-resistant diaphragm pump 32 and an electric conductivity detector 33 connected in sequence by pipelines, the number of the storage tank 31 is two, which respectively stores FeCl3 and HCl solution, the output end of the electric conductivity detector 33 is connected with the tubular reactor 21 through a pipeline, FeCl3 is dissolved in 10% dilute hydrochloric acid, the concentration is monitored by an online electric conductivity detector, the target value of the concentration is 12±0.5 wt%, the whole conveying pipeline is heated, and the temperature is controlled at 70 DEG C, so that FeCl3 is prevented from being precipitated at low temperature, so that the FeCl3 / HCl solution can flow into the first-stage reaction tube 231 to react with o-nitrotoluene, and the FeCl3 / HCl solution is injected to form a 30° jet mixing angle with o-nitrotoluene, and the flow rate is 1.0-1.5 L / h.

[0069] The chlorine distribution system 4 comprises a titanium sintering head 41 and a control monitoring module 42 connected in sequence by pipelines, the control monitoring module 42 comprises a dew point monitor connected therewith and a mass flow controller connected with the tubular reactor 21, the control monitoring module 42 is connected with the tubular reactor 21 through a pipeline below, that is, connected with the second-stage reaction tube 231, in operation, the dew point monitor is used for real-time detection to ensure that the dew point of chlorine is ≤-40 DEG C, and the mass flow controller is used for adjusting the flow according to the molar ratio of Cl2:o-nitrotoluene=1.05:1, if the temperature of the reactor 231 is >70 DEG C, the flow of Cl2 is automatically reduced by 5%.

[0070] Specifically, the gas-liquid separation tank 5 comprises a gas-liquid separation tank pipe 51 connected with the output end of the tubular reactor 21, the gas-liquid separation tank pipe 51 is provided with an automatic sampler 52 at the discharge end, and the gas-liquid separation tank pipe 51 is connected with a tail gas treatment system through a tail gas discharge pipe 53, samples are collected by the automatic sampler every 15 minutes, and the tail gas is sent into the tail gas treatment system through the tail gas discharge pipe 53, the tail gas treatment system comprises a primary falling film absorption tower and a secondary alkali washing tower, HCl is recovered by dilute hydrochloric acid, and residual Cl2 is neutralized by the secondary alkali washing tower, so that the discharge standard is reached.

[0071] The control mode of the present application is automatically controlled by a controller, the control circuit of the controller can be realized by simple programming of those skilled in the art, the power supply also belongs to the common knowledge in the art, and the present application is mainly used for protecting mechanical devices, therefore, the control mode and circuit connection of the present application will not be explained in detail.

[0072] The above description is only the preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for the continuous chlorination of a pesticide intermediate, characterized by: The continuous chlorination reaction equipment for pesticide intermediates is realized, the equipment includes raw material pretreatment system (1), reaction system (2), catalyst injection system (3), chlorine distribution system (4), gas-liquid separation tank (5) and tail gas treatment system, the raw material pretreatment system (1) is sequentially connected with the reaction system (2), the gas-liquid separation tank (5) and the tail gas treatment system through the pipeline, the output end of the catalyst injection system (3) and the chlorine distribution system (4) is connected with the reaction system (2), the raw material pretreatment system (1) includes a dehydration tank (11), a dehydration treatment module connected with the dehydration tank (11) and a preheater (12), the reaction system (2) includes a tubular reactor (21) and a cooling system (22) and a reaction module arranged on the tubular reactor (21); The chlorine distribution system (4) includes a titanium sintering head (41) and a control monitoring module (42) connected in sequence through the pipeline, the gas-liquid separation tank (5) includes a gas-liquid separation tank pipe (51) connected with the output end of the tubular reactor (21), an automatic sampler (52) is arranged at the discharge end of the gas-liquid separation tank pipe (51), and the gas-liquid separation tank pipe (51) is connected with the tail gas treatment system through a tail gas discharge pipe (53); The reaction module includes reaction tubes (231) and isothermal tubes (232) connected in sequence, heat insulation sheets (233) are arranged between the reaction tubes (231) and the isothermal tubes (232), forming stepped heating and reducing axial temperature coupling interference; The number of the reaction tubes (231) is three sections, the number of the isothermal tubes (232) is two sections, the input end of the first section and the output end of the third section of the reaction tubes (231) are connected with the raw material pretreatment system (1) and the gas-liquid separation tank (5) respectively, the reaction tubes (231) and the isothermal tubes (232) are coaxial, the catalyst injection system (3) is connected with the first section of the reaction tubes (231), and the control monitoring module (42) is connected with the second section of the reaction tubes (231) through the pipeline below; The method comprises the following steps: Step a: the raw material o-nitrotoluene is dehydrated in the raw material pretreatment system (1) and preheated to 60-70 DEG C; Step b: the 10-15 wt% iron trichloride / dilute hydrochloric acid solution is filtered and continuously injected into the reaction system (2) through the catalyst injection system (3); Step c: the o-nitrotoluene pretreated in step a, the iron trichloride solution in step b and dry chlorine are respectively introduced into the input end of the first section of the reaction tubes (231), the first section of the reaction tubes (231) and the third section of the reaction tubes (231) at the flow rates of 8-10 L / h, 1.0-1.5 L / h and 0.8-1.0 m³ / h respectively, the temperature of the reaction module from left to right controls the temperature of the reaction tubes (231) and the isothermal tubes (232) to decrease in the range of 70-60 DEG C, so that the reaction liquid can be gradually cooled when flowing from the reaction tubes (231) into the isothermal tubes (232), the system pressure is 0.4-0.6 MPa, and the residence time is 30-40 minutes. Step d: gas-liquid separation of the reacted mixture through a gas-liquid separator (5), liquid phase product is collected after online analysis, and unreacted chlorine and hydrogen chloride gas is treated by two-stage alkali washing; Step e: continuously removing ferrous ion impurities in the ferric chloride solution through an electrodialysis module, maintaining the Fe²⁺ concentration ≤50 ppm, and performing product analysis.

2. The method according to claim 1, wherein the method is characterized by: The molar ratio of the chlorine to the o-nitrotoluene is 1.05:1 to 1.1:

1.

3. The method according to claim 2, wherein the method is characterized by: The o-nitrotoluene has a water content ≤0.1% after dehydration.

4. The method according to claim 3, wherein the method is characterized by: The operating current density of the electrodialysis module is 15-25 mA / cm², and the regeneration cycle is operated once every 48-72 hours, and the molar ratio of Fe³⁺ / Fe²⁺ in the ferric chloride solution after regeneration is ≥200:

1.

5. The method according to claim 4, wherein the method is characterized by: The dehydration treatment module comprises a feed pipe (13) fixed to the outer wall of the dehydration tank (11), a positioning sleeve (14) arranged below the feed pipe (13), and a dehydration ball (15) in sliding contact with the positioning sleeve (14), wherein the dehydration ball (15) is provided with a hot nitrogen inlet pipe (16) and a rotating mechanism (17), and the dehydration ball (15) is used to place 3A molecular sieves.

6. The method according to claim 5, wherein the method is characterized by: The dehydration ball (15) is provided with a leakage hole (151) on the surface, and a protruding baffle (152) is fixed to the inner wall bottom surface of the dehydration ball (15), and the surface of the baffle (152) is provided with an exchange hole (153), and a sealing structure is arranged between the adjacent surfaces of the positioning sleeve (14) and the dehydration ball (15).

7. The method according to claim 6, wherein the method is characterized by: The input end of the cooling system (22) corresponds to the position of the heterothermal pipe (232), and the cooling system (22) comprises a circulating pipe (221) connected to the inside of the reaction system (2), a three-way valve (222) connected to the input end of the circulating pipe (221), and an external pipe (223) connected to the input end of the three-way valve (222).

8. The method according to claim 7, wherein the method is characterized by: The preheater (12) is sequentially connected with a water content sensor (18) and a positioning sleeve (14) above, the catalyst injection system (3) comprises a storage tank (31), an acid-resistant diaphragm pump (32) and an electric conductivity detector (33) connected in sequence through pipelines, and the output end of the electric conductivity detector (33) is connected to the tubular reactor (21) through a pipeline.

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