Preparation system and preparation method of polychloromethylpyridine

Abstract

The invention provides a preparation system and a preparation method of polychloromethylpyridine. The preparation system comprises a reactor, a gas-liquid separator, a circulating pump and an extraction pump, the reactor comprises: an inner nozzle, which is used for introducing 2-chloro-5-methylpyridine; the outer spraying nozzle is used for introducing chlorine, and a spraying opening of the inner spraying nozzle is formed in the outer spraying nozzle; the outlet end of the outer spray nozzle is located in the flow dividing pipe; the shunt pipe is used for enabling reaction materials of 2-chloro-5-methylpyridine and chlorine to form internal circulation flow; the vertical shell is provided with a reaction cavity, and the flow dividing pipe is arranged in the reaction cavity in the axial direction of the vertical shell. The polychloromethylpyridine prepared by adopting the preparation system disclosed by the invention is relatively high in yield and relatively low in cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic synthesis, in particular to a preparation system and method of polychloromethyl pyridine. BACKGROUND

[0002] The main process for synthesizing 2-chloro-5-chloromethyl pyridine is 2-chloro-5-methyl pyridine process and cyclopentadiene method. Relatively speaking, the cyclopentadiene method has cost advantage. The cost of 2-chloro-5-methyl pyridine to synthesize 2-chloro-5-chloromethyl pyridine is 46832 yuan (at the price in 2024), and the cost of cyclopentadiene method to synthesize 2-chloro-5-chloromethyl pyridine is 42356 yuan (at the price in 2024). And 2-chloro-5-trichloromethyl pyridine is usually obtained by chlorination of 2-chloro-5-chloromethyl pyridine with chlorine in a reaction kettle.

[0003] 2-chloro-5-chloromethyl pyridine is an important pesticide fungicide intermediate, and its downstream products include imidacloprid, acetamiprid, etc.; the main use of 2-chloro-5-trichloromethyl pyridine includes as an organic synthesis intermediate, widely used in pesticides, medicines and fine chemicals, etc. Specifically, 2-chloro-5-trichloromethyl pyridine is a key intermediate for producing high-efficiency herbicide spirodiclofen, and can further prepare 2-chloro-5-trifluoromethyl pyridine, which is a key intermediate for producing high-efficiency insecticide chlorfluazuron, high-efficiency herbicide spiro-oxam and high-efficiency fungicide fluazinam, etc.

[0004] The cyclopentadiene method for producing 2-chloro-5-chloromethyl pyridine requires a large amount of N,N dimethylformamide solvent (1-1.2 tons per ton of product), and produces high-concentration phosphorus-containing wastewater, which is difficult to treat and has a greater impact on the environment. And the existing 2-chloro-5-methyl pyridine production 2-chloro-5-chloromethyl pyridine process cost is not dominant.

[0005] The Chinese patent application with patent application publication number CN119143664A discloses a preparation method of 2-chloro-5-trichloromethyl pyridine, which comprises the following steps: introducing 2-chloro-5-methyl pyridine and chlorine into a first kettle simultaneously to perform a first chlorination reaction to obtain a first chlorination product; introducing the first chlorination product and chlorine into a second kettle to perform a second chlorination reaction to obtain a 2-chloro-5-trichloromethyl pyridine crude product; and sequentially performing light removal and rectification on the 2-chloro-5-trichloromethyl pyridine crude product to obtain 2-chloro-5-trichloromethyl pyridine. This method uses multi-kettle reactors for chlorination, which may result in: 1) low utilization rate of chlorine, and 2) low selectivity of raw materials.

[0006] A Chinese patent application with the patent application publication number CN118851990A discloses a synthesis method of 2-chloro-5-chloromethylpyridine. 2-chloro-5-methylpyridine is vaporized, and the preheated chlorine gas is introduced into the reactor to carry out the gas phase reaction to obtain the synthesis gas; the synthesis gas is sequentially subjected to the first stage condensation and the second stage condensation to obtain the cooling liquid; wherein the temperature of the condensate after the first stage condensation is 170-180 DEG C; the cooling liquid is subjected to the rectification to obtain the 2-chloro-5-chloromethylpyridine. The process needs to vaporize the 2-chloro-5-methylpyridine, the boiling point of the 2-chloro-5-methylpyridine is above 196 DEG C, a high heat is needed to completely vaporize it, the process energy consumption is very high, and the relatively pure 2-chloro-5-methylpyridine is easy to coke at the high temperature of 190 DEG C to produce the tar, resulting in the material loss. SUMMARY

[0007] The main purpose of the present application is to provide a preparation system and method of polychloromethylpyridine to solve the problems of low yield and high cost in the prior art.

[0008] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a preparation system of polychloromethylpyridine is provided, the polychloromethylpyridine is 2-chloro-5-chloromethylpyridine or 2-chloro-5-trichloromethylpyridine, comprising: a reactor for reacting 2-chloro-5-methylpyridine with chlorine to obtain a gas-liquid mixture; the reactor comprises: an inner nozzle for introducing 2-chloro-5-methylpyridine; an outer nozzle for introducing chlorine, the nozzle of the inner nozzle is arranged inside the outer nozzle; a shunt pipe, the outlet end of the outer nozzle is located in the shunt pipe; the shunt pipe is used to form an internal circulation flow of the reactants of 2-chloro-5-methylpyridine and chlorine; a vertical shell having a reaction cavity, the shunt pipe is arranged in the reaction cavity along the axial direction of the vertical shell; a gas-liquid separator for gas-liquid separation of the gas-liquid mixture to obtain separated gas and separated liquid containing polychloromethylpyridine; a circulating pump for backflowing part of the separated liquid to the reactor; a production pump for producing the remaining separated liquid.

[0009] Further, the above-mentioned inner nozzle is provided with a first separated liquid inlet, the outer nozzle is provided with a separated gas inlet, and the vertical shell is provided with a gas-liquid mixture outlet; the gas-liquid separator has a gas-liquid mixture inlet, a separated gas outlet, a first separated liquid outlet and a second separated liquid outlet, the gas-liquid mixture outlet is connected with the gas-liquid mixture inlet, the first separated liquid outlet is connected with the first separated liquid inlet, and the separated gas outlet is connected with the separated gas inlet; the circulating pump is arranged on the pipeline connected with the first separated liquid inlet and the first separated liquid outlet; the production pump has a second separated liquid inlet, and the second separated liquid outlet is connected with the second separated liquid inlet.

[0010] Further, the outer nozzle extends axially into the interior of the flow divider through the top of the vertical shell; the outer nozzle comprises a first tube section, a second tube section and a third tube section in sequence from top to bottom, the inner diameters of the first tube section, the second tube section and the third tube section decrease in sequence, the inner nozzle extends axially into the interior of the outer nozzle through the top of the outer nozzle, and the nozzle outlet of the inner nozzle is located above the third tube section.

[0011] Further, the inner nozzle comprises a fourth tube section and a fifth tube section in sequence from top to bottom, the inner diameter of the fourth tube section is greater than that of the fifth tube section, the first separated liquid inlet is arranged on the side wall of the fourth tube section, and the top of the inner nozzle is provided with a 2-chloro-5-methylpyridine inlet; the first tube section of the outer nozzle is provided with a separated gas inlet, and a chlorine gas inlet is arranged on the pipeline of the separated gas inlet; the nozzle outlet of the inner nozzle is located below the separated gas inlet.

[0012] Further, the ratio of the inner diameter of the fourth tube section to the inner diameter of the first tube section is 1:(1.5-4); the ratio of the inner diameter of the first tube section to the inner diameter of the third tube section is 1:(0.35-0.85); the ratio of the inner diameter of the third tube section, the inner diameter of the flow divider and the inner diameter of the vertical shell is 1:(1.5-5.0):(5.5-30), and the ratio of the height of the flow divider to the height of the vertical shell is 1:(1.2-1.8).

[0013] Further, the top of the flow divider is lower than the gas-liquid mixture outlet.

[0014] Further, the reactor further comprises a tray arranged between the outer side wall of the flow divider and the inner side wall of the vertical shell.

[0015] Further, a branch pipe is arranged on the pipeline connecting the separated gas outlet and the separated gas inlet, and the preparation system further comprises a demister, the branch pipe is connected to the inlet of the demister, the demister has a converted liquid outlet and a tail gas outlet, the converted liquid outlet is connected to the inlet of the circulating pump, and a pressure valve is arranged on the pipeline connecting the separated gas outlet and the demister.

[0016] Further, the preparation system further comprises a temperature adjusting device arranged on the pipeline connecting the circulating pump and the reactor.

[0017] Further, the preparation system further comprises a gas displacement kettle for gas displacement treatment of the remaining separated liquid to remove the gas in the separated liquid after the separated liquid is produced, and the gas displacement kettle is connected to the outlet of the production pump.

[0018] According to another aspect of the present application, there is provided a method for producing a polychloromethylpyridine, which is 2-chloro-5-chloromethylpyridine or 2-chloro-5-trichloromethylpyridine, using the aforementioned production system, the method comprising: Step S1, mixing 2-chloro-5-methylpyridine and chlorine to form an internal circulation flow and reacting the same to obtain a gas-liquid mixture; Step S2, gas-liquid separating the gas-liquid mixture to obtain a separated gas and a separated liquid containing the polychloromethylpyridine; and Step S3, refluxing part of the separated liquid into the reaction and producing the remaining separated liquid.

[0019] Further, the production conditions of the 2-chloro-5-chloromethylpyridine are as follows: the molar ratio of 2-chloro-5-methylpyridine to chlorine is 1 : (1.05 to 1.8), the reaction temperature is 80 to 140°C, and when the reaction is a continuous reaction, the residence time of the continuous reaction is 1.5 to 4.5 hours.

[0020] Further, the production conditions of the 2-chloro-5-trichloromethylpyridine are as follows: the molar ratio of 2-chloro-5-methylpyridine to chlorine is 1 : (3.1 to 4.5), the reaction temperature is 130 to 170°C, and when the reaction is a continuous reaction, the residence time of the continuous reaction is 3 to 8 hours.

[0021] Further, the absolute pressure of the reaction is 0.8 bar to 5 bar.

[0022] Further, the pressure of the gas-liquid separation is 0.6 bar to 4 bar.

[0023] Further, the separated gas is refluxed into the reaction.

[0024] Further, when the actual pressure of the separated gas exceeds a set value, the foam generated in the gas-liquid separation is converted into tail gas and a converted liquid, and the converted liquid is refluxed into the reaction.

[0025] Further, in Step S3, part of the separated liquid is temperature-adjusted and then refluxed into the reaction.

[0026] Further, in Step S3, the remaining separated liquid is subjected to a gas-removing treatment after being produced.

[0027] The inner nozzle and the outer nozzle in the technical scheme of the present application help to increase the contact area of chlorine and 2-chloro-5-methylpyridine, thereby helping to improve the mixing effect of chlorine and 2-chloro-5-methylpyridine. The outlet end of the outer nozzle is located in the flow divider, which helps the mixture of chlorine and 2-chloro-5-methylpyridine to enter the bottom of the vertical shell at a certain flow rate, then bounce up between the flow divider and the inner wall of the vertical shell, and then descend along the inside of the flow divider to form an internal circulation flow, thereby helping to improve the reaction efficiency of chlorine and 2-chloro-5-methylpyridine, and further helping to improve the yield of polychloromethylpyridine. The gas-liquid separator helps to separate the gas-liquid mixture generated by the reactor into separated gas and separated liquid containing polychloromethylpyridine. The circulation pump helps to return part of the separated liquid to the reactor, which helps to further improve the yield of polychloromethylpyridine and helps to maintain the continuous operation of the preparation system. Therefore, the polychloromethylpyridine prepared by the preparation system of the present application has a high yield and a low cost. BRIEF DESCRIPTION OF DRAWINGS

[0028] The drawings accompanying the specification of the present application serve to provide a further understanding of the present application, and the illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0029] Figure 1 A preparation system structure schematic diagram of Example 1 of the present application is shown;

[0030] Figure 2 A gas chromatogram of 2-chloro-5-chloromethylpyridine in Example 1 of the present application is shown;

[0031] Figure 3 A gas chromatogram of 2-chloro-5-trichloromethylpyridine in Example 11 of the present application is shown.

[0032] Among them, the above drawings include the following reference signs:

[0033] 1, reactor; 2, gas-liquid separator; 3, defoamer; 4, temperature adjusting device; 5, circulation pump; 6, production pump; 7, gas displacement kettle; 8, pressure valve; 11, inner nozzle; 12, outer nozzle; 13, flow divider; 14, vertical shell; 15, tray. DETAILED DESCRIPTION

[0034] It should be noted that the examples in the present application and the features in the examples can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the examples.

[0035] As analyzed in the background section of this application, the prior art suffers from low yield and high cost in preparing polychlorinated methylpyridine. To address these issues, this application provides a polychlorinated methylpyridine preparation system and method thereof.

[0036] In one typical embodiment of this application, a system for preparing polychlorinated methylpyridine is provided, such as... Figure 1 As shown, the polychlorinated methylpyridine is 2-chloro-5-chloromethylpyridine or 2-chloro-5-trichloromethylpyridine, comprising: a reactor 1 for reacting 2-chloro-5-methylpyridine with chlorine gas to obtain a gas-liquid mixture; the reactor 1 includes: an inner nozzle 11 for introducing 2-chloro-5-methylpyridine; an outer nozzle 12 for introducing chlorine gas, the nozzle of the inner nozzle 11 being disposed inside the outer nozzle 12; a diverter 13, the outlet end of the outer nozzle 12 being located within the diverter 13; the diverter 13 is used to form an internal circulation flow of the reaction materials of 2-chloro-5-methylpyridine and chlorine gas; a vertical shell 14 having a reaction chamber, the diverter 13 being disposed in the reaction chamber along the axial direction of the vertical shell 14; a gas-liquid separator 2 for separating the gas-liquid mixture to obtain a separated gas and a separated liquid containing polychlorinated methylpyridine; a circulation pump 5 for returning a portion of the separated liquid to the reactor 1; and a collection pump 6 for collecting the remaining separated liquid.

[0037] The internal and external nozzle configuration in this application helps increase the contact area between chlorine and 2-chloro-5-methylpyridine, thereby improving their mixing effect. The outlet end of the external nozzle is located inside the diversion pipe, allowing the mixture of chlorine and 2-chloro-5-methylpyridine to enter the bottom of the vertical shell at a certain flow rate. It then rebounds and rises along the inner wall between the diversion pipe and the vertical shell, before descending further down the diversion pipe, forming an internal circulation flow. This helps improve the reaction efficiency of chlorine and 2-chloro-5-methylpyridine, and consequently, the yield of polychlorinated methylpyridine. The gas-liquid separator facilitates the separation of the gas-liquid mixture generated in the reactor to obtain a separated gas and a separated liquid containing polychlorinated methylpyridine. The circulating pump helps to return a portion of the separated liquid to the reactor, further improving the yield of polychlorinated methylpyridine and maintaining the continuous operation of the preparation system. Therefore, the preparation system of this application yields polychlorinated methylpyridine with a high yield and low cost.

[0038] In an embodiment of the present application, the inner nozzle 11 is provided with a first separated liquid inlet, the first separated liquid inlet is higher than the top of the outer nozzle 12, the outer nozzle 12 is provided with a separated gas inlet, and the vertical shell 14 is provided with a gas-liquid mixture outlet; the gas-liquid separator 2 has a gas-liquid mixture inlet, a separated gas outlet, a first separated liquid outlet and a second separated liquid outlet, the gas-liquid mixture outlet is connected to the gas-liquid mixture inlet, the first separated liquid outlet is connected to the first separated liquid inlet, and the separated gas outlet is connected to the separated gas inlet; the circulating pump 5 is arranged on a pipeline connecting the first separated liquid outlet and the first separated liquid inlet; the production pump 6 has a second separated liquid inlet, and the second separated liquid outlet is connected to the second separated liquid inlet.

[0039] The gas-liquid mixture outlet is connected to the gas-liquid mixture inlet, which helps to transport the gas-liquid mixture generated in the reactor to the gas-liquid separator. The first separated liquid outlet is connected to the first separated liquid inlet, which helps to return part of the separated liquid to the reactor for continuous reaction.

[0040] In an embodiment of the present application, the outer nozzle 12 extends axially through the top of the vertical shell 14 to the inside of the flow dividing pipe 13; the outer nozzle 12 comprises a first pipe section, a second pipe section and a third pipe section from top to bottom in sequence, the inner diameters of the first pipe section, the second pipe section and the third pipe section decrease in sequence, the inner nozzle 11 extends axially through the top of the outer nozzle 12 to the inside of the outer nozzle 12, and the nozzle of the inner nozzle 11 is located above the third pipe section, preferably at the junction of the first and second pipe sections.

[0041] The inner diameters of the first pipe section, the second pipe section and the third pipe section decrease in sequence, which on the one hand helps to improve the mixing effect of chlorine and 2-chloro-5-methylpyridine, and on the other hand helps to reduce the specific surface area of the bubbles in the mixture of chlorine and 2-chloro-5-methylpyridine. The nozzle of the inner nozzle 11 is located above the third pipe section, which helps to increase the contact area of chlorine and 2-chloro-5-methylpyridine.

[0042] In an embodiment of the present application, the inner nozzle 11 comprises a fourth pipe section and a fifth pipe section from top to bottom in sequence, the inner diameter of the fourth pipe section is greater than that of the fifth pipe section, the fourth pipe section is provided with a first separated liquid inlet on the side wall, and the top of the inner nozzle 11 is provided with a 2-chloro-5-methylpyridine inlet; the first pipe section of the outer nozzle 12 is provided with a separated gas inlet, and the pipeline of the separated gas inlet is provided with a chlorine inlet; the nozzle of the inner nozzle 11 is located below the separated gas inlet.

[0043] The inner diameter of the fourth pipe section is greater than that of the fifth pipe section, which helps to make 2-chloro-5-methylpyridine form a turbulent flow, so that 2-chloro-5-methylpyridine is mixed with chlorine violently, the bubbles are dispersed, and the specific surface area of the bubbles is reduced.

[0044] In an embodiment of the present application, the first pipe section is cylindrical, the second pipe section is an inverted circular truncated cone, the third pipe section is cylindrical, the fourth pipe section is cylindrical, and the fifth pipe section is an inverted circular truncated cone. The above-mentioned shapes can stabilize the feeding of the inner and outer nozzles.

[0045] Preferably, the central axes of the inner nozzle 11, the outer nozzle 12, the flow divider 13, and the vertical shell 14 are coaxial, which is more conducive to the stability of feeding and reaction.

[0046] In an embodiment of the present application, the ratio of the inner diameter of the fourth pipe section to the inner diameter of the first pipe section is 1:(1.5-4), the ratio of the inner diameter of the first pipe section to the inner diameter of the third pipe section is 1:(0.35-0.85), and the ratio of the inner diameter of the third pipe section, the inner diameter of the flow divider 13, and the inner diameter of the vertical shell 14 is 1:(1.5-5.0):(5.5-30), and the ratio of the height of the flow divider 13 to the height of the vertical shell 14 is 1:(1.2-1.8).

[0047] Controlling the ratio of the inner diameter of the fourth pipe section to the inner diameter of the first pipe section within the above-mentioned range helps to increase the intensity of mixing of 2-chloro-5-methylpyridine with chlorine, thereby further reducing the specific surface area of the bubbles. Controlling the ratio of the inner diameter of the first pipe section to the inner diameter of the third pipe section within the above-mentioned range helps to further improve the mixing effect of 2-chloro-5-methylpyridine with chlorine and reduce the specific surface area of the bubbles. Controlling the ratio of the inner diameter of the third pipe section, the inner diameter of the flow divider, and the inner diameter of the vertical shell, and the ratio of the height of the flow divider to the height of the vertical shell within the above-mentioned range helps to optimize the internal circulation flow, thereby further improving the yield of polychloromethylpyridine.

[0048] In order to further improve the circulation effect of the internal circulation flow and thereby improve the yield of polychloromethylpyridine, in an embodiment of the present application, the top of the flow divider 13 is lower than the gas-liquid mixture outlet, and preferably the ratio of the vertical distance from the top of the flow divider 13 to the gas-liquid mixture outlet to the length of the flow divider 13 is (0.1-0.25):1.

[0049] In order to reduce the gas holdup per unit volume, increase the gas-liquid surface contact area, and improve the mass transfer effect, in an embodiment of the present application, the reactor 1 further comprises a tray 15 disposed between the outer sidewall of the flow divider 13 and the inner sidewall of the vertical shell 14.

[0050] The above-mentioned tray can be one or more, and preferably the tray is a circular bubble cap tray or a sieve tray, and the hole diameter of the tray is 3.2-24 mm. More preferably, the tray is disposed near the lower end of the flow divider, which facilitates the timely formation of a more stable internal circulation flow from the reaction material sprayed from the outer nozzle 12, and has a better promoting effect on improving the mass transfer effect and enhancing the reaction efficiency.

[0051] In one embodiment of the present application, a branch pipe is arranged on the pipe connecting the separation gas outlet and the separation gas inlet, and the preparation system further comprises a demister 3, the branch pipe being connected to the inlet of the demister 3, the demister 3 having a conversion liquid outlet and a tail gas outlet, the conversion liquid outlet being connected to the inlet of the circulating pump 5; and a pressure valve 8 arranged on the pipe connecting the separation gas outlet and the demister 3.

[0052] The demister and the pressure valve help maintain the balance of pressure in the gas-liquid separator. The tail gas comprises hydrogen chloride and chlorine.

[0053] In one embodiment of the present application, the preparation system further comprises a temperature adjusting device 4 arranged on the pipe connecting the circulating pump 5 and the reactor 1.

[0054] The reaction of the present application is an exothermic reaction, and the temperature of the separation liquid refluxed to the reactor is higher than the temperature required for the reaction, and the temperature adjusting device helps cool the separation liquid refluxed to the reactor to maintain the reaction temperature in the reactor.

[0055] The temperature adjusting device 4 is a heat exchanger, and o-dichlorobenzene is used as the cooling medium.

[0056] In one embodiment of the present application, the preparation system further comprises a gas displacement still 7 for performing gas displacement treatment on the remaining separation liquid to remove the gas (in the form of tail gas) in the separation liquid after the separation liquid is produced, the gas displacement still 7 being connected to the outlet of the production pump 6.

[0057] The gas displacement still helps further remove the gas in the separation liquid, which mainly comprises hydrogen chloride and chlorine.

[0058] In another typical embodiment of the present application, a preparation method of polychloromethylpyridine, which is 2-chloro-5-chloromethylpyridine or 2-chloro-5-trichloromethylpyridine, is provided, and the polychloromethylpyridine is prepared by using the aforementioned preparation system, and the preparation method comprises the following steps: S1, mixing 2-chloro-5-methylpyridine and chlorine to form an internal circulation flow for reaction to obtain a gas-liquid mixture; S2, performing gas-liquid separation on the gas-liquid mixture to obtain separation gas and separation liquid containing polychloromethylpyridine; and S3, refluxing part of the separation liquid to the reaction, and producing the remaining separation liquid.

[0059] The formation of the internal circulation flow in the present application helps to improve the mixing effect of chlorine and 2-chloro-5-methylpyridine, thereby helping to improve the reaction efficiency of chlorine and 2-chloro-5-methylpyridine, and further helping to improve the yield of polychloromethylpyridine. The reflux of part of the separated liquid into the reactor helps to further improve the yield of polychloromethylpyridine, and also helps to maintain the continuous operation of the preparation system. Therefore, the polychloromethylpyridine prepared by the preparation method of the present application has a high yield and a low cost.

[0060] In an embodiment of the present application, the preparation conditions of 2-chloro-5-chloromethylpyridine are as follows: the molar ratio of 2-chloro-5-methylpyridine to chlorine is 1: (1.05-1.8), the reaction temperature is 80-140°C, and when the reaction is a continuous reaction, the residence time of the continuous reaction is 1.5-4.5 h.

[0061] Controlling the molar ratio of 2-chloro-5-methylpyridine to chlorine, the reaction temperature, and the residence time within the above ranges helps to improve the yield of 2-chloro-5-chloromethylpyridine.

[0062] In an embodiment of the present application, the preparation conditions of 2-chloro-5-trichloromethylpyridine are as follows: the molar ratio of 2-chloro-5-methylpyridine to chlorine is 1: (3.1-4.5), the reaction temperature is 130-170°C, and when the reaction is a continuous reaction, the residence time of the continuous reaction is 3-8 h.

[0063] Controlling the molar ratio of 2-chloro-5-methylpyridine to chlorine, the reaction temperature, and the residence time within the above ranges helps to improve the yield of 2-chloro-5-trichloromethylpyridine.

[0064] In order to further improve the yield of polychloromethylpyridine, in an embodiment of the present application, the absolute pressure of the above reaction is 0.8 bar-5 bar.

[0065] In order to further improve the effect of gas-liquid separation, in an embodiment of the present application, the pressure of the above gas-liquid separation is 0.6 bar-4 bar.

[0066] In order to reduce the reaction cost, in an embodiment of the present application, the separated gas is refluxed into the reaction.

[0067] In order to further improve the gas-liquid separation efficiency, in an embodiment of the present application, when it is detected that the actual pressure of the separated gas exceeds the set value, the foam generated in the gas-liquid separation process is converted into tail gas and conversion liquid, and the conversion liquid is refluxed into the reaction.

[0068] In order to maintain the reaction temperature and thereby improve the reaction efficiency, in an embodiment of the present application, part of the separated liquid is temperature-adjusted before being refluxed into the reaction in the above step S3.

[0069] In order to further improve the purity of the polychloromethylpyridine, in an embodiment of the present application, after the remaining separation liquid is extracted, the gas in the separation liquid is removed by gas chasing treatment.

[0070] The beneficial effects of the present application will be further illustrated below in combination with examples.

[0071] Example 1

[0072] A polychloromethylpyridine preparation system, as shown in Figure 1As shown, the preparation system comprises a reactor 1 for reacting 2-chloro-5-methylpyridine with chlorine to obtain a gas-liquid mixture, the reactor 1 comprising an inner nozzle 11 for feeding 2-chloro-5-methylpyridine, an outer nozzle 12 for feeding chlorine, a flow divider 13 for forming an inner circulating flow of the reactants of 2-chloro-5-methylpyridine and chlorine, a vertical shell 14 having a reaction cavity, the flow divider 13 being arranged in the reaction cavity along the axial direction of the vertical shell 14, the center axes of the inner nozzle 11, the outer nozzle 12, the flow divider 13 and the vertical shell 14 being coaxially arranged, a gas-liquid separator 2, a circulating pump 5, a production pump 6, a demister 3, a pressure valve 8, a temperature adjusting device 4 and a gas displacement kettle 7. The inner nozzle 11 is provided with a first separated liquid inlet which is higher than the top of the outer nozzle 12, and the outer nozzle 12 is provided with a separated gas inlet, and the vertical shell 14 is further provided with a gas-liquid mixture outlet. The gas-liquid separator 2 has a gas-liquid mixture inlet, a separated gas outlet, a first separated liquid outlet and a second separated liquid outlet, the gas-liquid mixture outlet is connected with the gas-liquid mixture inlet, the first separated liquid outlet is connected with the first separated liquid inlet, and the separated gas outlet is connected with the separated gas inlet. The circulating pump 5 is arranged on the pipeline connecting the first separated liquid outlet with the first separated liquid inlet. The production pump 6 has a second separated liquid inlet, and the second separated liquid outlet is connected with the second separated liquid inlet. The outer nozzle 12 extends axially through the top of the vertical shell 14 to the inside of the flow divider 13. The outer nozzle 12 comprises a first tube section, a second tube section and a third tube section which are sequentially communicated from top to bottom, and the inner nozzle 11 extends axially through the top of the outer nozzle 12 to the inside of the outer nozzle 12, and the nozzle of the inner nozzle 11 is located at the junction of the first and second tube sections. The inner nozzle 11 comprises a fourth tube section and a fifth tube section which are sequentially communicated from top to bottom, the first separated liquid inlet is arranged on the side wall of the fourth tube section, and the top of the inner nozzle 11 is provided with a 2-chloro-5-methylpyridine inlet. The first tube section of the outer nozzle 12 is provided with a separated gas inlet, and the pipeline of the separated gas inlet is provided with a chlorine inlet. The nozzle of the inner nozzle 11 is located below the separated gas inlet. The first tube section is in the shape of a cylinder, the second tube section is in the shape of an inverted circular table, the third tube section is in the shape of a cylinder, the fourth tube section is in the shape of a cylinder, and the fifth tube section is in the shape of an inverted circular table. The ratio of the inner diameter of the fourth tube section to the inner diameter of the first tube section is 1:3. The ratio of the inner diameter of the first tube section to the inner diameter of the third tube section is 1:0.55. The ratio of the inner diameter of the third tube section, the inner diameter of the flow divider 13 and the inner diameter of the vertical shell 14 is 1:2.5:25. The ratio of the height of the flow divider 13 to the height of the vertical shell 14 is 1:1.45. The ratio of the vertical distance from the top of the flow divider 13 to the gas-liquid mixture outlet to the length of the flow divider 13 is 0.1:1. The reactor 1 further comprises two trays 15 (circular bubble cap trays with a hole diameter of 16 mm) which are arranged between the outer side wall of the flow divider 13 and the inner side wall of the vertical shell 14 at a position close to the lower end of the flow divider.A branch pipe is arranged on the pipe connecting the separation gas outlet and the separation gas inlet, the branch pipe is connected with the inlet of the demister 3, the demister 3 has a conversion liquid outlet and a tail gas outlet, the conversion liquid outlet is connected with the inlet of the circulating pump 5; the pressure valve 8 is arranged on the pipe connecting the separation gas outlet and the demister 3; the temperature adjusting device 4 (heat exchanger, using o-dichlorobenzene as the cooling medium) is arranged on the pipe connecting the circulating pump 5 and the reactor 1; the gas displacement kettle 7 is connected with the outlet of the extraction pump 6.

[0073] The above system is used to prepare 2-chloro-5-chloromethylpyridine, 2-chloro-5-methylpyridine and chlorine gas with a molar ratio of 1:1.5 are introduced into the reactor 1 to form an internal circulation flow for reaction, the reaction pressure is 3 bar, the reaction temperature is 110°C, and the residence time is 3 h, to obtain a gas-liquid mixture, the gas-liquid mixture is introduced into the gas-liquid separator 2 for gas-liquid separation, the pressure is 2 bar, to obtain separation gas and separation liquid containing 2-chloro-5-chloromethylpyridine, the separation gas is returned to the reactor 1, when the pressure valve 8 detects that the pressure of the separation gas exceeds 2.0 bar, the demister 3 is opened to convert the foam generated in the gas-liquid separator 2 into tail gas and conversion liquid, part of the separation liquid and the conversion liquid are returned to the reactor 1 by the circulating pump 5, part of the separation liquid and the conversion liquid pass through the temperature adjusting device 4 to adjust the temperature to the same temperature as the reaction temperature during the returning process, the remaining separation liquid is extracted by the extraction pump 6, the separation liquid after extraction is removed of chlorine and hydrogen chloride by the gas displacement kettle 7, to obtain 2-chloro-5-chloromethylpyridine, and the gas chromatogram of 2-chloro-5-chloromethylpyridine is shown in Figure 2 .

[0074] Example 2

[0075] The difference from example 1 is that the ratio of the inner diameter of the fourth pipe segment to the inner diameter of the first pipe segment is 1:1.5; the ratio of the inner diameter of the first pipe segment to the inner diameter of the third pipe segment is 1:0.35; the ratio of the inner diameter of the third pipe segment, the inner diameter of the shunt pipe 13 and the inner diameter of the vertical shell 14 is 1:1.5:5.5, and the ratio of the height of the shunt pipe 13 to the height of the vertical shell 14 is 1:1.2, to finally obtain 2-chloro-5-chloromethylpyridine.

[0076] Example 3

[0077] The difference from example 1 is that the ratio of the inner diameter of the fourth pipe segment to the inner diameter of the first pipe segment is 1:4; the ratio of the inner diameter of the first pipe segment to the inner diameter of the third pipe segment is 1:0.85; the ratio of the inner diameter of the third pipe segment, the inner diameter of the shunt pipe 13 and the inner diameter of the vertical shell 14 is 1:5.0:30, and the ratio of the height of the shunt pipe 13 to the height of the vertical shell 14 is 1:1.8, to finally obtain 2-chloro-5-chloromethylpyridine.

[0078] Example 4

[0079] The difference from Example 1 is that the ratio of the inner diameter of the fourth tube segment to the inner diameter of the first tube segment is 1:5; the ratio of the inner diameter of the first tube segment to the inner diameter of the third tube segment is 1:1; the ratio of the inner diameter of the third tube segment, the inner diameter of the flow divider 13, and the inner diameter of the vertical housing 14 is 1:8:32, and the ratio of the height of the flow divider 13 to the height of the vertical housing 14 is 1:2, and 2-chloro-5-chloromethylpyridine is finally obtained.

[0080] Example 5

[0081] The difference from Example 1 is that the reaction pressure is 0.8 bar, and the pressure for gas-liquid separation is 0.6 bar, and 2-chloro-5-chloromethylpyridine is finally obtained.

[0082] Example 6

[0083] The difference from Example 1 is that the reaction pressure is 5 bar, and the pressure for gas-liquid separation is 4 bar, and 2-chloro-5-chloromethylpyridine is finally obtained.

[0084] Example 7

[0085] The difference from Example 1 is that the reaction pressure is 6 bar, and the pressure for gas-liquid separation is 6 bar, and 2-chloro-5-chloromethylpyridine is finally obtained.

[0086] Example 8

[0087] The difference from Example 1 is that the molar ratio of 2-chloro-5-methylpyridine to chlorine is 1:1.05, the reaction temperature is 80°C, and the residence time is 4.5 h, and 2-chloro-5-chloromethylpyridine is finally obtained.

[0088] Example 9

[0089] The difference from Example 1 is that the molar ratio of 2-chloro-5-methylpyridine to chlorine is 1:1.8, the reaction temperature is 140°C, and the residence time is 1.5 h, and 2-chloro-5-chloromethylpyridine is finally obtained.

[0090] Example 10

[0091] The difference from Example 1 is that the molar ratio of 2-chloro-5-methylpyridine to chlorine is 1:2, the reaction temperature is 150°C, and the residence time is 1 h, and 2-chloro-5-chloromethylpyridine is finally obtained.

[0092] Example 11

[0093] The difference from Example 1 is that the above system is used to prepare 2-chloro-5-trichloromethylpyridine, 2-chloro-5-methylpyridine and chlorine gas with a molar ratio of 1:4 are fed into the reactor 1 to form an internal circulation flow to react, the reaction pressure is 3 bar, the reaction temperature is 150°C, and the residence time is 5 h, to obtain a gas-liquid mixture, the gas-liquid mixture is fed into the gas-liquid separator 2 to perform gas-liquid separation, the pressure is 2.5 bar, to obtain separated gas and separated liquid containing 2-chloro-5-trichloromethylpyridine, the separated gas is returned to the reactor 1, when the pressure valve 8 detects that the pressure of the separated gas exceeds 2.5 bar, the defoamer 3 is opened to convert the foam generated in the gas-liquid separator 2 into tail gas and conversion liquid, part of the separated liquid and the conversion liquid are returned to the reactor 1 by using the circulating pump 5, the temperature of the part of the separated liquid and the conversion liquid is adjusted to the same temperature as the reaction temperature by using the temperature adjusting device 4, and the remaining separated liquid is extracted by using the extraction pump 6, the separated liquid after extraction is removed of chlorine and hydrogen chloride by using the gas displacement kettle 7, to obtain 2-chloro-5-trichloromethylpyridine, and the gas chromatogram of 2-chloro-5-trichloromethylpyridine is shown in Figure 1. Figure 3

[0094] Example 12

[0095] The difference from Example 11 is that the molar ratio of 2-chloro-5-methylpyridine and chlorine gas is 1:3.1, the reaction temperature is 130°C, and the residence time is 8 h, to finally obtain 2-chloro-5-trichloromethylpyridine.

[0096] Example 13

[0097] The difference from Example 11 is that the molar ratio of 2-chloro-5-methylpyridine and chlorine gas is 1:4.5, the reaction temperature is 170°C, and the residence time is 3 h, to finally obtain 2-chloro-5-trichloromethylpyridine.

[0098] Example 14

[0099] The difference from Example 11 is that the molar ratio of 2-chloro-5-methylpyridine and chlorine gas is 1:5, the reaction temperature is 180°C, and the residence time is 2 h, to finally obtain 2-chloro-5-trichloromethylpyridine.

[0100] Comparative Example 1

[0101] The difference from Example 1 is that the internal nozzle 11 is cancelled, and 2-chloro-5-methylpyridine is added through the top of the external nozzle 12, to finally obtain 2-chloro-5-chloromethylpyridine.

[0102] Comparative Example 2

[0103] The difference from Example 1 is that the shunt pipe 13 is cancelled, to finally obtain 2-chloro-5-chloromethylpyridine.

[0104] ​Comparative Example 3

[0105] 2-chloro-5-trichloromethylpyridine was prepared by the method of Example 1 of the Chinese patent application with the application publication number CN119143664A.

[0106] Performance test

[0107] The 2-chloro-5-chloromethylpyridine or 2-chloro-5-trichloromethylpyridine prepared by the examples and comparative examples was analyzed by gas chromatography and the purity and yield of the 2-chloro-5-chloromethylpyridine or 2-chloro-5-trichloromethylpyridine were calculated, and the results are shown in Table 1. It should be noted that the purity in this application is the purity after purification treatment.

[0108] Table 1

[0109]

[0110]

[0111] From the above description, it can be seen that the above-mentioned examples of the present application achieve the following technical effects:

[0112] The inner nozzle and the outer nozzle in this application help to improve the contact area of chlorine and 2-chloro-5-methylpyridine, thereby helping to improve the mixing effect of chlorine and 2-chloro-5-methylpyridine. The outlet end of the outer nozzle is located inside the flow divider, which helps the mixture of chlorine and 2-chloro-5-methylpyridine to enter the bottom of the vertical shell at a certain flow rate, then bounce up between the flow divider and the inner wall of the vertical shell, and then descend along the inside of the flow divider, forming an internal circulation flow, thereby helping to improve the reaction efficiency of chlorine and 2-chloro-5-methylpyridine, and further helping to improve the yield of polychloromethylpyridine. The gas-liquid separator helps to separate the gas-liquid mixture produced by the reactor to obtain separated gas and separated liquid containing polychloromethylpyridine. The circulation pump helps to return part of the separated liquid to the reactor, which on the one hand helps to further improve the yield of polychloromethylpyridine, and on the other hand helps to maintain the continuous operation of the preparation system. Therefore, the polychloromethylpyridine prepared by the preparation system of the present application has a high yield and a low cost.

[0113] The above is only an example of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A system for the preparation of polychloromethylpyridines, which are 2-chloro-5- chloromethylpyridine or 2-chloro-5-trichloromethylpyridine, characterized in that, The application relates to a reactor (1) for reacting 2-chloro-5-methylpyridine with chlorine to obtain a gas-liquid mixture; the reactor (1) comprises: an inner nozzle (11) for feeding 2-chloro-5-methylpyridine; an outer nozzle (12) for feeding chlorine, the nozzle of the inner nozzle (11) being arranged inside the outer nozzle (12); a shunt pipe (13), the outlet end of the outer nozzle (12) being arranged inside the shunt pipe (13); the shunt pipe (13) is used for forming an inner circulating flow of the reactants of the 2-chloro-5-methylpyridine and the chlorine; a vertical shell (14) having a reaction cavity, the shunt pipe (13) being arranged in the reaction cavity along the axial direction of the vertical shell (14); a gas-liquid separator (2) for gas-liquid separation of the gas-liquid mixture to obtain separated gas and separated liquid containing polychloromethylpyridine; a circulating pump (5) for returning part of the separated liquid to the reactor (1); and a production pump (6) for producing the remaining separated liquid. The inner nozzle (11) is provided with a first separated liquid inlet, the outer nozzle (12) is provided with a separated gas inlet, and the vertical shell (14) is provided with a gas-liquid mixture outlet. The gas-liquid separator (2) has a gas-liquid mixture inlet, a separated gas outlet, a first separated liquid outlet and a second separated liquid outlet, the gas-liquid mixture outlet is connected with the gas-liquid mixture inlet, the first separated liquid outlet is connected with the first separated liquid inlet, and the separated gas outlet is connected with the separated gas inlet. The circulating pump (5) is arranged on a pipeline connected between the first separated liquid outlet and the first separated liquid inlet. The production pump (6) has a second separated liquid inlet, and the second separated liquid outlet is connected with the second separated liquid inlet. The outer nozzle (12) extends axially to the inside of the shunt pipe (13) through the top of the vertical shell (14); the outer nozzle (12) comprises a first pipe section, a second pipe section and a third pipe section which are sequentially connected from top to bottom, the inner diameters of the first pipe section, the second pipe section and the third pipe section are sequentially reduced, the inner nozzle (11) extends axially to the inside of the outer nozzle (12) through the top of the outer nozzle (12), and the nozzle of the inner nozzle (11) is located above the third pipe section. The inner nozzle (11) comprises a fourth pipe section and a fifth pipe section which are sequentially connected from top to bottom, the inner diameter of the fourth pipe section is larger than that of the fifth pipe section, the first separated liquid inlet is arranged on the side wall of the fourth pipe section, and the top of the inner nozzle (11) is provided with a 2-chloro-5-methylpyridine inlet; the first pipe section of the outer nozzle (12) is provided with the separated gas inlet, and a chlorine inlet is arranged on the pipeline of the separated gas inlet; and the nozzle of the inner nozzle (11) is located below the separated gas inlet. The ratio of the inner diameter of the fourth pipe section to the inner diameter of the first pipe section is 1:(1.5-4), and the ratio of the inner diameter of the first pipe section to the inner diameter of the third pipe section is 1: ​ 2. The preparation system according to claim 1, characterized in that, ​ ​ ​ ​ 3. The preparation system according to claim 2, characterized in that ​ 4. The preparation system according to claim 3, characterized in that ​ 5. The preparation system according to claim 4, characterized in that ​ The ratio of the inner diameter of the third pipe section, the inner diameter of the flow divider (13) and the inner diameter of the vertical housing (14) is 1: (1.5-5.0): (5.5-30), and the ratio of the height of the flow divider (13) and the height of the vertical housing (14) is 1: (1.2-1.8).

6. The production system according to claim 5, characterized in that The top of the flow divider (13) is lower than the gas-liquid mixture outlet.

7. The production system according to claim 6, characterized in that The reactor (1) further comprises a tray (15) arranged between the outer sidewall of the flow divider (13) and the inner sidewall of the vertical housing (14).

8. The production system according to claim 7, characterized in that The preparation system further comprises: a defoamer (3) connected to the inlet of the defoamer (3), the defoamer (3) having a conversion liquid outlet and a tail gas outlet, the conversion liquid outlet being connected to the inlet of the circulating pump (5); a pressure valve (8) arranged in the pipeline connecting the separation gas outlet and the defoamer (3).

9. The production system according to claim 8, characterized in that The preparation system further comprises a temperature adjusting device (4) arranged in the pipeline connecting the circulating pump (5) and the reactor (1).

10. The production system according to any one of claims 1 to 9, characterized in that, The preparation system further comprises a gas displacement kettle (7) for displacing the remaining separation liquid to remove the gas in the separation liquid, the gas displacement kettle (7) being connected to the outlet of the production pump (6).

11. A process for the preparation of a polychloromethylpyridine, which is 2-chloro-5- chloromethylpyridine or 2-chloro-5-trichloromethylpyridine, characterized in that, The polychloromethylpyridine is prepared by the preparation system of any one of claims 1-10, and the preparation method comprises: Step S1, mixing 2-chloro-5-methylpyridine and chlorine to form an internal circulation flow for reaction to obtain a gas-liquid mixture; Step S2, gas-liquid separation of the gas-liquid mixture to obtain separation gas and separation liquid containing the polychloromethylpyridine; Step S3, part of the separation liquid is returned to the reaction, and the remaining separation liquid is produced.

12. The method of claim 11, wherein, The preparation conditions of the 2-chloro-5-chloromethylpyridine are that the molar ratio of the 2-chloro-5-methylpyridine to the chlorine is 1: (1.05-1.8), the reaction temperature is 80-140℃, and when the reaction is a continuous reaction, the residence time of the continuous reaction is 1.5-4.5h.

13. The preparation method according to claim 11, characterized in that, The preparation conditions of the 2-chloro-5-trichloromethylpyridine are that the molar ratio of the 2-chloro-5-methylpyridine to the chlorine is 1: (3.1-4.5), the reaction temperature is 130-170℃, and when the reaction is a continuous reaction, the residence time of the continuous reaction is 3-8h.

14. The production method according to any one of claims 11 to 13, characterized by, The absolute pressure of the reaction is 0.8bar-5bar.

15. The production method according to any one of claims 11 to 14, characterized by, The pressure of the gas-liquid separation is 0.6bar-4bar.

16. The production method according to any one of claims 11 to 15, characterized by, The separation gas is returned to the reaction.

17. The production method according to any one of claims 11 to 16, characterized by, When the actual pressure of the separation gas is detected to exceed the set value, the foam generated in the gas-liquid separation process is converted into tail gas and conversion liquid, and the conversion liquid is returned to the reaction.

18. The production method according to any one of claims 11 to 17, characterized by, In step S3, part of the separation liquid is temperature-adjusted before being returned to the reaction. In step S3, part of the separation liquid is temperature-adjusted before being returned to the reaction.

19. The production method according to any one of claims 11 to 18, characterized by, In the step S3, the remaining separation liquid is discharged and gas chasing treatment is performed to remove the gas in the separation liquid.

Images