A device and method for continuously preparing an aniline diazonium salt

Abstract

The application relates to a device and a method for continuously preparing aniline diazonium salt, wherein a first inlet, a second inlet and a material outlet are arranged on a reactor, an aniline compound batching kettle is connected with the first inlet through a first pipeline, a first input pump and a first flowmeter are arranged on the first pipeline, a sodium nitrite batching kettle is connected with the second inlet through a second pipeline, a second input pump and a second flowmeter are arranged on the second pipeline, the material outlet is connected with a product receiving kettle through a third pipeline, a third flowmeter, a delay pipe and a sampling pipe are arranged on the third pipeline, a reactor flow channel is arranged in the reactor, the reactor flow channel comprises a primary mixing cavity and a spiral flow channel, the first inlet and the second inlet are communicated with the primary mixing cavity, the input end of the spiral flow channel is communicated with the primary mixing cavity, and the output end of the spiral flow channel is communicated with the material outlet. The application can obtain a high diazonium salt conversion rate in a short reaction time by using a reaction temperature close to room temperature, and the reaction process is safe.

Description

Technical Field

[0001] This invention relates to the field of diazotization technology, specifically to an apparatus and method for the continuous preparation of aniline-based diazonium salts. Background Technology

[0002] Diazotization generally refers to the process of reacting aromatic primary amines with sodium nitrite to form diazonium salts. Diazonium salts are important intermediates in many chemical products, such as the arylation reaction of Meerwein. Aniline diazonium salts, under the catalysis of copper salts, can generate products that substituted aromatic compounds, which can be used in various pharmaceutical and agricultural products. Furthermore, if aniline diazonium salts continue to react with aromatic amines or phenols, they can produce dyes and pigments. However, side reactions are very common during the aniline diazonium salt reaction, and most diazonium salts are unstable. Increased temperature easily leads to self-coupling reactions, producing viscous byproducts that affect the quality of the diazonium salts. They can only be stored for short periods at low temperatures (0–5°C). In addition, improper storage of diazonium salts can easily cause explosions. Current technologies mainly use traditional batch reactions to achieve batch diazotization, but because the reaction temperature needs to be maintained at 0–5°C, excessive energy consumption is required, and the diazonium salt solution has a reddish appearance and produces many byproducts. At the same time, the reaction is exothermic and prone to runaway temperature increases, potentially causing accidents. Summary of the Invention

[0003] The purpose of this invention is to provide an apparatus and method for the continuous preparation of aniline diazonium salts, which can achieve a high diazonium salt conversion rate in a shorter reaction time at a reaction temperature close to room temperature, and the reaction process is safe.

[0004] The objective of this invention is achieved through the following technical solution: An apparatus for the continuous preparation of aniline diazonium salts includes an aniline compound mixing vessel, a sodium nitrite mixing vessel, a reactor, a delay tube, and a product receiving vessel. The reactor has a first inlet, a second inlet, and a material outlet. The aniline compound mixing vessel is connected to the first inlet via a first pipeline, which is equipped with a first input pump and a first flow meter. The sodium nitrite mixing vessel is connected to the second inlet via a second pipeline, which is equipped with a second input pump and a second flow meter. The material outlet is connected to the product receiving vessel via a third pipeline, which is equipped with a third flow meter, a delay tube, and a sampling tube. The reactor contains a reactor flow channel, which includes a primary mixing chamber and a spiral flow channel. Both the first and second inlets are connected to the primary mixing chamber. The input end of the spiral flow channel is connected to the primary mixing chamber, and its output end is connected to the material outlet.

[0005] The reactor is provided with a connecting channel, and the second inlet is connected to the primary mixing chamber through the connecting channel. The lower output end of the connecting channel is provided with a PTFE gasket with through holes.

[0006] The number of through holes on the PTFE gasket satisfies the following condition: 4q / (3πd 2 )≤n≤2q / (πd) 2 ) ; In the above formula, n is the number of through holes on the PTFE gasket, q is the material flow rate input at the second inlet, and d is the diameter of the through holes on the PTFE gasket.

[0007] The reactor is equipped with spiral blades that form the spiral flow channel.

[0008] The aniline compound mixing vessel is equipped with a first heat exchanger, the sodium nitrite mixing vessel is equipped with a second heat exchanger, and the delay tube is equipped with a third heat exchanger.

[0009] Pressure sensors and temperature sensors are provided on the first pipeline between the first flow meter and the reactor, and on the second pipeline between the second flow meter and the reactor. Pressure sensors, temperature sensors, and check valves are provided on the third pipeline between the third flow meter and the delay tube. Temperature sensors are provided on the third pipeline between the delay tube and the product receiving vessel.

[0010] The aniline compound mixing tank, sodium nitrite mixing tank, and product receiving tank are all equipped with stirring blades driven by a motor.

[0011] A method for the continuous preparation of aniline diazonium salts using the aforementioned apparatus includes the following steps: Step 1: Determine the number of through holes in the PTFE gasket and install the PTFE gasket in the reactor. Step 2: Prepare a material slurry that meets the requirements in the aniline compound mixing tank, and prepare a sodium nitrite solution that meets the requirements in the sodium nitrite mixing tank; Step 3: Run water through the pipes to check for leaks; Step 4: Adjust the appropriate pump flow rates of the first and second input pumps to control the material's time in the reactor and delay tube to meet the requirements; Step 5: Control the reaction temperature in the reactor and delay tube to 15-20℃, and open the sampling tube to observe the state of the generated product. After the product state meets the requirements, open the product receiving vessel to receive the product. Step 6: After the reaction is complete, replace the reactants in the aniline compound mixing tank and the sodium nitrite mixing tank with clean water and rinse until the liquid flowing out of the sampling tube outlet is colorless; Step 7: Perform a conversion rate test on the generated diazonium salt.

[0012] In step two, if the room temperature is higher than the set reaction temperature, the pipeline is circulated with ice water; if the room temperature is lower than the set reaction temperature, the pipeline is circulated with clean water.

[0013] In step four, the initial product containing byproducts is discharged through a sampling tube. After the product clarifies, starch-potassium iodide test paper is used to verify whether the product contains excessive sodium nitrite. Only after it meets the requirements is the product receiving vessel opened.

[0014] The advantages and positive effects of this invention are as follows: 1. The present invention can achieve a high conversion rate of diazonium salts at a reaction temperature close to room temperature and in a shorter reaction time. Compared with the existing batch preparation of diazonium salts with a conversion rate of 95% to 96%, the conversion rate of the present invention can reach 98.5%. Moreover, compared with the existing batch preparation of diazonium salts with a reaction time of about 30 minutes, the reaction time of the present invention can be shortened to 1 to 2 minutes, and the reaction process is safe.

[0015] 2. This invention employs a method where two materials are first dispersed and mixed through a PTFE gasket, and then the premix is ​​further mixed through a spiral flow channel. This effectively improves the problem of uneven mixing of high-viscosity materials in the reactants. The mixture after pore dispersion enters the spiral flow channel and is simultaneously subjected to radial and axial shear forces, which ensures thorough mixing of high-viscosity reactants, reduces the generation of local hot spots, and improves the quality of the product. Furthermore, the spiral angle can be adjusted according to the reactant viscosity to achieve optimal mixing of reactants of different viscosities, ultimately increasing the diazonium salt yield. This directly improves the overall yield of subsequent reactions involving diazonium salts, reduces waste emissions, increases economic value, and facilitates reactor scale-up. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention. Figure 2 for Figure 1 A schematic diagram of the reactor structure in the diagram. Figure 3 for Figure 2 A cross-sectional view of the reactor in the image. Figure 4 for Figure 3 A schematic diagram of the spiral plate structure in the diagram. Figure 5 for Figure 3 A schematic diagram of the PTFE gasket structure.

[0017] Wherein, 1 is the aniline compound mixing vessel, 2 is the first input pump, 3 is the first flow meter, 4 is the reactor, 5 is the sodium nitrite mixing vessel, 6 is the second input pump, 7 is the second flow meter, 8 is the third flow meter, 9 is the delay tube, 10 is the product receiving vessel, 11 is the PTFE gasket; 101 is the first inlet, 401 is the reactor flow channel, 4011 is the spiral vane, 4012 is the initial mixing chamber, 402 is the material outlet, 403 is the connecting flow channel, and 501 is the second inlet. Detailed Implementation

[0018] The invention will now be described in further detail with reference to the accompanying drawings.

[0019] like Figures 1-5 As shown, the present invention includes an aniline compound mixing tank 1, a sodium nitrite mixing tank 5, a reactor 4, a delay tube 9, and a product receiving tank 10, wherein... Figure 2 As shown, the reactor 4 is provided with a first inlet 101, a second inlet 501, and a material outlet 402. The aniline compound mixing vessel 1 is connected to the first inlet 101 via a first pipeline, and a first input pump 2 and a first flow meter 3 are sequentially arranged along the material transport direction on the first pipeline. The sodium nitrite mixing vessel 5 is connected to the second inlet 501 via a second pipeline, and a second input pump 6 and a second flow meter 7 are sequentially arranged along the material transport direction on the second pipeline. In this embodiment, the first input pump 2 is a peristaltic pump, and the second input pump 6 is a horizontal flow pump. The material outlet 402 is connected to the product receiving vessel 10 via a third pipeline, and a third flow meter 8, a delay tube 9, and a sampling tube are sequentially arranged along the material transport direction on the third pipeline. Figures 3-4 As shown, the reactor 4 is provided with a reactor flow channel 401, and the reactor flow channel 401 includes a primary mixing chamber 4012 and a spiral flow channel. The first inlet 101 and the second inlet 501 are both connected to the primary mixing chamber 4012. The input end of the spiral flow channel is connected to the primary mixing chamber 4012, and the output end is connected to the material outlet 402.

[0020] like Figure 3As shown, the reactor 4 is provided with a connecting channel 403, and the second inlet 501 is connected to the primary mixing chamber 4012 through the connecting channel 403. The lower output end of the connecting channel 403 is provided with a PTFE gasket 11 with through holes. The incoming sodium nitrite solution is dispersed through the through holes on the PTFE gasket 11 and enters the primary mixing chamber 4012 to achieve initial mixing with the continuous phase aniline compound slurry that flows in continuously through the first inlet 101. Then it enters the spiral channel for forced and thorough mixing. In this embodiment, the number of through holes on the PTFE gasket 11 is determined according to the fluid flux inside the reactor 4. In order to ensure that the fluid linear velocity inside the reactor 4 is maintained at 2-3 m / s to achieve the best mass transfer effect, the number of through holes on the PTFE gasket 11 needs to be designed and selected.

[0021] The selection of the number of through holes on the PTFE gasket 11 must first meet the following conditions: n≤2q / (πd 2 (1); In the above formula (1), n ​​is the number of through holes on the PTFE gasket 11, q is the material flow rate input to the second inlet 501, and d is the diameter of the through holes on the PTFE gasket 11.

[0022] Secondly, to prevent excessive system load within reactor 4, the number of through holes on the PTFE gasket 11 must also meet the following conditions: n≥4q / (3πd 2 (2); For example, if q = 35 ml / min and d = 0.4 mm: First, n ≤ 2 × 35 / (π × 0.04) 2 ) / (100×60)=2.32, Secondly, n≥4×35 / (3×π×0.04) 2 ) / (100×60)=1.54, like Figure 5 As shown, based on the above calculations, the number of through holes on the PTFE gasket 11 is two. Preferably, the PTFE gasket 11 of the present invention has two or four through holes.

[0023] like Figures 3-4As shown in this embodiment, the reactor 4 is equipped with a spiral blade 4011 to form the spiral flow channel. This invention employs a method where two materials are first dispersed and mixed through pores, and then the premix is ​​further mixed through the spiral flow channel. This method effectively improves the problem of uneven mixing of high-viscosity materials in the reactants. After pore dispersion, the mixture enters the spiral flow channel and is simultaneously subjected to radial and axial shear forces. This ensures thorough mixing of high-viscosity reactants, reduces the generation of local hot spots, and improves the quality of the product. Furthermore, the spiral blade 4011 with an appropriate spiral angle can be selected according to the reactant viscosity to achieve optimal mixing of reactants of different viscosities, ultimately increasing the diazonium salt yield. This directly improves the overall yield of subsequent reactions involving diazonium salts, reduces waste emissions, increases economic value, and facilitates reactor scale-up.

[0024] In this embodiment, the aniline compound mixing vessel 1 is equipped with a first heat exchanger, the sodium nitrite mixing vessel 5 is equipped with a second heat exchanger, and the delay tube 9 is equipped with a third heat exchanger. In this embodiment, the heat exchangers can adopt a structure in which heat exchange tubes are arranged on the inner wall of the vessel or the inner wall of the tube. Water or other heat exchange liquids are placed inside the heat exchange tubes to achieve heat exchange and maintain the temperature inside the vessel or the tube. This is a well-known technology in the art.

[0025] A pressure sensor and a temperature sensor are provided on the first pipeline between the first flow meter 3 and the reactor 4. A pressure sensor and a temperature sensor are also provided on the second pipeline between the second flow meter 7 and the reactor 4. A pressure sensor, a temperature sensor and a check valve are provided on the third pipeline between the third flow meter 8 and the delay pipe 9. A temperature sensor is provided on the third pipeline between the delay pipe 9 and the product receiving vessel 10.

[0026] like Figure 1 As shown, the aniline compound mixing tank 1, the sodium nitrite mixing tank 5, and the product receiving tank 10 are all equipped with stirring blades that are driven to rotate by a motor.

[0027] The working principle of this invention is as follows: The process of this invention includes the following steps: Step 1: Determine the number of through holes in the PTFE gasket 11 according to the design, and install the PTFE gasket 11 in the reactor 4.

[0028] Step 2: Prepare a material slurry with the required mass concentration in aniline compound mixing tank 1, and prepare a sodium nitrite solution in sodium nitrite mixing tank 5 according to the ratio.

[0029] Step 3: Run water through the pipeline first to check for leaks. If the room temperature is higher than the reaction temperature (20°C), run ice water through the pipeline first. If the room temperature is lower than the reaction temperature (20°C), run clean water through the pipeline first.

[0030] Step 4: Adjust the appropriate flow rates of the first input pump 2 and the second input pump 6. Specifically, first turn on the first input pump 2, then turn on the second input pump 6. After the material is mixed by collision in the reactor 4, the mixture passes through a delay tube 9 of a certain length and reaches the product receiving vessel 10. It is necessary to control the time the material spends in the reactor 4 and the delay tube 9 to meet the requirements. In addition, if the generated diazonium salt needs to continuously participate in the next reaction, this invention requires adding an aminosulfonic acid solution input pipeline to react with the diazonium salt that has passed through a delay tube in an auxiliary reactor to destroy excess sodium nitrite in the diazonium salt.

[0031] Step 5: Control the reaction temperature at 15-20℃ using each heat exchanger, and open the sampling tube to observe the state of the generated product.

[0032] The reaction temperature of the reactants is controlled at 15-20℃ to obtain a high diazonium salt conversion rate in a short time. In addition, due to the mismatch in concentration of the initial product, there are many by-products, which need to be discharged as waste liquid through the sampling tube. After the product becomes clear, it is immediately verified with starch-potassium iodide test paper whether there is an excess of sodium nitrite. After meeting the requirements, the product receiving vessel 10 is opened to allow the product to be loaded into the product receiving vessel 10.

[0033] Step 6: After the reaction is complete, replace the reactants in aniline compound mixing tank 1 and sodium nitrite mixing tank 5 with clean water for rinsing until the liquid flowing out of the sampling tube outlet is colorless.

[0034] Step 7: Diazonium salt conversion rate test. Specifically, select a coupling component and prepare a standard solution of a certain concentration. For each test, take an appropriate volume of the coupling component and prepare a coupling component with a buffer solution of acetic acid and sodium acetate. Then, take a certain amount of the diazonium salt to be tested, and prepare a standard solution after destroying excess sodium nitrite with aminosulfonic acid. Use an acid burette to add the diazonium salt to be tested to the coupling component until the H acid on the filter paper changes from colorless to slightly blue using the permeation method. Record the volume of diazonium salt consumed. Then, calculate the actual concentration of diazonium salt in the product using the formula and compare it with the theoretical concentration to calculate the diazonium salt conversion rate.

[0035] The following application examples further illustrate the invention.

[0036] Application Example 1 In this application example, the material flow rate input to the second inlet 501 is 31.5 ml / min, and a PTFE gasket with a pore diameter of 0.4 mm and two pores is selected. First, prepare a 2% (w / w) concentration of 4-chloro-2-nitroaniline slurry. Weigh 13.35g of 4-chloro-2-nitroaniline (99.5% concentration, 0.077mol) and pour it into aniline compound mixing tank 1. Then weigh 300g of tap water and dissolve 27.82g of hydrochloric acid (32.8% concentration, 0.25mol) in the water to prepare a hydrochloric acid solution. Pour the well-stirred hydrochloric acid solution into aniline compound mixing tank 1. Control the slurry temperature at 0-5℃ using the first heat exchanger and slurry for at least 0.5 hours, then set aside. Weigh 15.23g of sodium nitrite (99% concentration, 0.115mol) and pour it into... 400g of tap water was stirred evenly at 10-15℃ using the second heat exchanger to control the temperature of the sodium nitrite solution, and then set aside. At the start of the reaction, the flow rate of the peristaltic pump (first input pump 2) was set to 35ml / min, and the flow rate of the horizontal flow pump (second input pump 6) was set to 31.5ml / min. The molar ratio of 4-chloro-2-nitroaniline to sodium nitrite was manually controlled at 1.12:1 using a flow meter. The diazotization temperature in the delay tube 9 was controlled at 20℃ using the third heat exchanger, and the reaction residence time was controlled at 1.008min using the delay tube 9. After the system stabilized, samples were taken, and the diazonium salt conversion rate was calculated to be 98.5% under these process conditions.

Claims

1. A method for continuous preparation of aniline diazonium salts, characterized in that: The apparatus for continuous preparation of aniline diazonium salts includes an aniline compound mixing vessel (1), a sodium nitrite mixing vessel (5), a reactor (4), a delay tube (9), and a product receiving vessel (10). The reactor (4) is equipped with a first inlet (101), a second inlet (501), and a material outlet (402). The aniline compound mixing vessel (1) is connected to the first inlet (101) via a first pipeline, and the first pipeline is equipped with a first input pump (2) and a first flow meter (3). The sodium nitrite mixing vessel (5) is connected to the second inlet (501) via a second pipeline, and the second pipeline is equipped with... The reactor (4) has a second input pump (6) and a second flow meter (7). The material outlet (402) is connected to the product receiving vessel (10) through a third pipeline. The third pipeline is equipped with a third flow meter (8), a delay tube (9) and a sampling tube. The reactor (4) is equipped with a reactor flow channel (401). The reactor flow channel (401) includes a primary mixing chamber (4012) and a spiral flow channel. The first inlet (101) and the second inlet (501) are both connected to the primary mixing chamber (4012). The input end of the spiral flow channel is connected to the primary mixing chamber (4012) and the output end is connected to the material outlet (402). The reactor (4) is provided with a connecting channel (403), and the second inlet (501) is vertically connected to the primary mixing chamber (4012) through the connecting channel (403). The lower output end of the connecting channel (403) is provided with a PTFE gasket (11) with through holes. The reactor (4) is provided with spiral blades (4011) forming the spiral flow channel; the fluid linear velocity inside the reactor (4) is maintained at 2 to 3 m / s; The aniline compound mixing vessel (1) is equipped with a first heat exchanger, the sodium nitrite mixing vessel (5) is equipped with a second heat exchanger, and the delay tube (9) is equipped with a third heat exchanger. The continuous preparation method of aniline diazonium salts includes the following steps: Step 1: Determine the number of through holes in the PTFE gasket (11) and install the PTFE gasket (11) in the reactor (4); The number of through holes on the PTFE gasket (11) satisfies the following condition: 4q / (v1πd 2 )≤n≤4q / (v2πd 2 ); In the above formula, n is the number of through holes on the PTFE gasket (11), q is the material flow rate input to the second inlet (501), d is the diameter of the through holes on the PTFE gasket (11), v1 is 3m / s, and v2 is 2m / s; Step 2: Prepare a material slurry that meets the requirements in the aniline compound mixing tank (1), and prepare a sodium nitrite solution that meets the requirements in the sodium nitrite mixing tank (5); Step 3: Run water through the pipes to check for leaks; Step 4: Adjust the appropriate pump flow rates of the first input pump (2) and the second input pump (6) to control the time the material spends in the reactor (4) and the delay tube (9) to meet the requirements; Step 5: Control the reaction temperature in the reactor (4) and the delay tube (9) to 15-20℃, and open the sampling tube to observe the state of the generated product. After the product state meets the requirements, open the product receiving vessel (10) to receive the product. The initial product, which contains byproducts, is discharged through a sampling tube. After the product is clarified, the product is verified to be free of sodium nitrite using starch-potassium iodide test paper. Once the product meets the requirements, the product receiving vessel (10) is opened. Step 6: After the reaction is complete, replace the reactants in the aniline compound mixing tank (1) and the sodium nitrite mixing tank (5) with clean water for cleaning until the liquid flowing out of the sampling tube outlet is colorless; Step 7: Perform a conversion rate test on the generated diazonium salt.

2. The method for continuous preparation of aniline diazonium salts according to claim 1, characterized in that: Pressure sensors and temperature sensors are provided on the first pipeline between the first flow meter (3) and the reactor (4) and on the second pipeline between the second flow meter (7) and the reactor (4). Pressure sensors, temperature sensors and one-way valves are provided on the third pipeline between the third flow meter (8) and the delay pipe (9). Temperature sensors are provided on the third pipeline between the delay pipe (9) and the product receiving vessel (10).

3. The method for continuous preparation of aniline diazonium salts according to claim 1, characterized in that: The aniline compound mixing tank (1), the sodium nitrite mixing tank (5), and the product receiving tank (10) are all equipped with stirring blades driven by a motor.

4. The method for continuous preparation of aniline diazonium salts according to claim 1, characterized in that: In step two, if the room temperature is higher than the set reaction temperature, the pipeline is circulated with ice water; if the room temperature is lower than the set reaction temperature, the pipeline is circulated with clean water.

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