O-chlorobenzylamine synthesis method

Abstract

The invention relates to the technical field of organic synthetic chemistry, and particularly discloses a synthesis method of o-chlorobenzylamine. According to the method, o-chlorobenzyl chloride, liquid ammonia and caustic soda liquid are used as raw materials, and the preparation process mainly comprises the steps of amination reaction, liquid ammonia recovery, alkali treatment deamination and product purification. Specifically, in a high-pressure reaction kettle, liquid ammonia is used as a reaction medium and reacts with o-chlorobenzyl chloride under the conditions of low temperature and specific pressure, and after the reaction, the liquid ammonia is evaporated out and recycled for recycling; dissolving with water, adding alkali for dissociation, and removing residual ammonia gas under negative pressure; and finally, separating an organic phase by standing and layering, and dehydrating and filtering to obtain a high-purity o-chlorobenzylamine product. According to the method, by constructing a solvent-free system and cooperatively controlling the reaction temperature, the material proportion and post-treatment parameters, side reactions are remarkably inhibited, and therefore high-selectivity synthesis is achieved. The whole process has the advantages of simplicity and convenience in operation, environmental friendliness, high resource utilization rate and easiness in industrial implementation.

Description

Technical Field

[0001] This application relates to the field of organic synthetic chemistry, and more specifically, to a method for synthesizing o-chlorobenzylamine. Background Technology

[0002] o-Chlorobenzylamine, as an important organic synthetic intermediate, is widely used in pharmaceuticals, pesticides, dyes, and other fields. The rationality and environmental friendliness of its synthesis process directly affect the quality and production cost of related downstream products. Therefore, developing efficient and clean methods for synthesizing o-chlorobenzylamine has significant industrial application value. Currently, methods for synthesizing o-chlorobenzylamine from halogenated hydrocarbons mainly include the Gabriel synthesis method, the Delépine synthesis method, and the method of direct reaction with ammonia. These methods have been applied to some extent in industrial production.

[0003] Existing synthetic methods have significant technical limitations. The Gabriel synthesis method requires the use of polar organic solvents such as DMF, resulting in high VOC emissions, high raw material costs, and complex separation and purification processes. The Delépine synthesis method generates a large number of low-recovery-value byproducts, leading to resource waste and cumbersome operation procedures. The method of direct reaction with ammonia water is difficult to control, easily resulting in polyamine reactions that generate impurities such as secondary and tertiary amines, leading to low selectivity of the target product and low utilization efficiency of recovered ammonia. Among these problems, the most critical technical challenge is that existing methods cannot simultaneously suppress polyamine side reactions, improve reaction selectivity, reduce the environmental pressure caused by the use of organic solvents, and achieve efficient resource recycling, thus limiting the greening and industrial upgrading of the o-chlorobenzylamine synthesis process. Summary of the Invention

[0004] To address the challenges in the synthesis of o-chlorobenzylamine in existing technologies, which struggle to simultaneously suppress polyamine side reactions, enhance reaction selectivity, and achieve environmental friendliness and resource recycling, this application provides a method for synthesizing o-chlorobenzylamine.

[0005] A method for synthesizing o-chlorobenzylamine includes the following steps: S1. In a high-pressure reactor, liquid ammonia is used as the reaction medium and undergoes an amination reaction with o-chlorobenzyl chloride. After the reaction is completed, the liquid ammonia is distilled off and recovered. S2. Add water to dissolve the reaction product obtained in step S1, then add liquid alkali and remove ammonia under negative pressure. S3. The material processed in step S2 is allowed to stand and separate into layers. The organic phase is then dehydrated and subjected to solid-liquid separation to obtain o-chlorobenzylamine.

[0006] By employing the above technical solution, liquid ammonia is selected as both the reaction medium and the amination reagent, eliminating the need for organic solvents in traditional synthesis. The physicochemical properties of liquid ammonia create a suitable environment for the amination reaction. Liquid ammonia evaporation rapidly cools the system to the target temperature range. Combined with a high molar ratio setting, this provides sufficient amino sites to ensure a complete reaction and inhibits further condensation of the generated primary amine with the raw materials through low temperature, reducing polyamine side reactions. A metering pump is used to stably deliver the raw materials, preventing abnormal reactions caused by excessively high local concentrations and improving system homogeneity. After the reaction, the heating rate is precisely controlled to evaporate the liquid ammonia, achieving efficient resource recovery and reuse. Adding a measured amount of water to the reaction products allows for complete dissolution of salts. Subsequent addition of liquid alkali neutralizes acidic substances and promotes the release of o-chlorobenzylamine. The ammonia gas removed by negative pressure heating is absorbed by water to prepare ammonia water for secondary utilization. After settling and layering, dehydration is achieved through anhydrous sodium sulfate, and impurities are removed by filtration with a specific precision filter material. The close collaboration of each step constructs a simple and efficient synthesis system, ensuring smooth reaction and effective product separation.

[0007] Preferably, in step S1, the reaction temperature of the amination reaction is -30°C to -20°C; the molar ratio of o-chlorobenzyl chloride to liquid ammonia is 1:50 to 1:100; the o-chlorobenzyl chloride is pumped in using a metering pump at a pressure of 3 bar to 8 bar for a feeding time of 0.4 h to 0.6 h; after the feeding is completed, the reaction is kept at the reaction temperature for 1 h.

[0008] By employing the above technical solution, the amination reaction is carried out in a specific low-temperature range, which significantly reduces the condensation reaction activity of o-chlorobenzylamine and o-chlorobenzyl chloride, thus inhibiting the formation of secondary and tertiary amine byproducts from a kinetic perspective. The high molar ratio of o-chlorobenzyl chloride to liquid ammonia provides sufficient amino donors, ensuring the full substitution of chlorine atoms in the raw materials. Simultaneously, excess liquid ammonia maintains an inert environment, reducing impurities. When the metering pump delivers the raw materials, appropriate pumping pressure ensures stable and continuous feeding, and reasonable feeding time avoids localized violent reactions, maintaining stable temperature and pressure within the system. Holding the reaction at the set low temperature after feeding ensures the amination reaction proceeds fully, improving the raw material conversion rate and laying a solid foundation for subsequent separation and purification processes.

[0009] Preferably, in step S1, the system is cooled by evaporating part of the liquid ammonia before the reaction, and the pressure inside the reactor is reduced from 5 bar to 7 bar to 1.5 bar to 2 bar during the cooling process; after the reaction is completed, the liquid ammonia is evaporated at a heating rate of 5°C / h to 10°C / h.

[0010] By employing the above technical solution, the system temperature is rapidly adjusted to the range required for the amination reaction by utilizing the endothermic physical property of liquid ammonia evaporation before the reaction. The pressure changes during the cooling process are precisely matched to the liquid ammonia evaporation process, ensuring stable evaporation of liquid ammonia to continuously provide cooling while creating a stable reaction environment, preventing pressure fluctuations from affecting reaction selectivity. After the reaction is completed, the temperature is slowly increased to prevent the target product from decomposing or undergoing secondary reactions due to sudden temperature increases. Simultaneously, unreacted liquid ammonia evaporates smoothly, reducing entrainment losses during evaporation, improving recovery efficiency, and ensuring the recycling of liquid ammonia, thus balancing reaction stability and resource utilization.

[0011] Preferably, in step S2, the amount of water added is 3L / kg to 5L / kg, based on the mass of o-chlorobenzyl chloride; the liquid alkali is a 32% sodium hydroxide aqueous solution, and the amount added is 90kg to 100kg, based on 100kg of o-chlorobenzyl chloride.

[0012] By adopting the above technical solution and controlling the amount of water added according to the raw material quality benchmark, the dissolution requirements of salts in the reaction products can be precisely matched, ensuring complete dissolution of salts and avoiding solid residues that may affect subsequent separation. At the same time, excessive water addition can lead to an excessively large system volume, increasing energy consumption and processing difficulty. A specific concentration of sodium hydroxide aqueous solution is selected as the liquid alkali, as its alkalinity and reactivity are suitable, efficiently neutralizing the acidic substances generated in the amination reaction while providing a sufficient alkaline environment for the release of o-chlorobenzylamine. Precise matching of the amount of liquid alkali added with the amount of substances to be neutralized and the target product in the system ensures that neutralization and release reactions proceed fully, creating favorable conditions for subsequent ammonia removal and material stratification, balancing reaction efficiency and material utilization.

[0013] Preferably, in step S2, the negative pressure condition refers to the system absolute pressure being lower than atmospheric pressure, the operating temperature for removing ammonia being 35°C to 45°C, and the ammonia removal time being 0.8h to 1.2h.

[0014] By employing the above technical solution and using negative pressure conditions with an absolute pressure lower than atmospheric pressure, the partial pressure and solubility of ammonia in the system can be reduced, disrupting the dissolution equilibrium and promoting the rapid escape of ammonia, thus providing the impetus for deammoniation. Controlling the deammoniation temperature within a suitable range can both increase the thermal motion rate of ammonia molecules to accelerate volatilization and prevent excessively high temperatures from causing deterioration of the target product or generating side reactions, thus synergistically enhancing the deammoniation effect with the negative pressure conditions. Reasonably setting the deammoniation time and precisely matching it with temperature and pressure parameters ensures that the ammonia separated downstream of the liquid alkali is fully removed, avoiding residual ammonia that could lead to blurred interfaces and reduced separation efficiency in subsequent material separation, laying the foundation for efficient separation of the target product.

[0015] Preferably, in step S3, anhydrous sodium sulfate is used to dehydrate the organic phase. The amount of anhydrous sodium sulfate added is 2 kg to 4 kg, based on 100 kg of o-chlorobenzyl chloride. The particle size of the anhydrous sodium sulfate is 50 μm to 200 μm, and the dehydration stirring time is 0.5 h.

[0016] By employing the above technical solution, anhydrous sodium sulfate is selected as the dehydrating agent, leveraging its strong water-absorbing properties to adsorb residual moisture in the organic phase. The particle size of the anhydrous sodium sulfate is controlled within a reasonable range, ensuring sufficient specific surface area for adequate contact with the organic phase while avoiding excessively fine particles that could clog subsequent filters or excessively coarse particles that could reduce water absorption efficiency. Precise matching of the dehydrating agent dosage to the moisture content in the organic phase ensures complete water adsorption, preventing incomplete dehydration from affecting product storage stability and subsequent application performance. Stirring during the dehydration process promotes uniform dispersion of the dehydrating agent, disrupts the local equilibrium of moisture in the organic phase, and ensures sufficient water absorption, thus guaranteeing the subsequent solid-liquid separation to remove moisture and impurities.

[0017] Preferably, in step S3, the solid-liquid separation is achieved by vacuum filtration, wherein the pore size of the filter medium used for vacuum filtration is 0.1 μm to 1 μm, and the vacuum filtration is carried out under a vacuum pressure of -0.05 MPa to -0.09 MPa.

[0018] By adopting the above technical solution, solid-liquid separation is achieved through vacuum filtration, which utilizes vacuum negative pressure to provide separation power and accelerate the separation process between the organic phase and solid impurities. The pore size of the filter medium is set within an appropriate range to precisely trap anhydrous sodium sulfate solid particles formed after dehydration, while ensuring the smooth passage of the o-chlorobenzylamine organic phase, avoiding solid impurity residue or filter blockage and product entrainment losses due to improper pore size. The vacuum pressure is controlled within a reasonable range to provide sufficient power for separation and ensure efficiency, while avoiding excessively high vacuum that could lead to excessive volatilization of the organic phase, resulting in decreased yield or impurity entrainment. This synergistic effect with the pore size of the filter medium ensures a stable and efficient separation process, further improving product purity.

[0019] Preferably, in step S1, the water content in the recovered liquid ammonia is ≤0.6% by mass.

[0020] By adopting the above technical solution and strictly controlling the moisture content of the recovered liquid ammonia, it is possible to ensure that the recovered liquid ammonia possesses stable physicochemical properties and reactivity, meeting the requirements for recycling. If the moisture content is too high, it will disrupt the inert environment required for subsequent amination reactions, not only reducing the reactivity of liquid ammonia with o-chlorobenzyl chloride but also potentially inducing side reactions and increasing the risk of reactor corrosion. This moisture control, combined with the aforementioned techniques such as controlling the heating rate and cooling pressure during ammonia stripping, reduces moisture entrainment through precise temperature and pressure control during the stripping process, ensuring the purity of the recovered liquid ammonia and achieving efficient recycling of liquid ammonia resources. Simultaneously, it provides a core guarantee for the stability and selectivity of subsequent reactions.

[0021] Preferably, in step S2, the stirring and dissolving rate after adding water is 100 rpm to 300 rpm; after the ammonia gas is removed, the mixture is allowed to stand for 0.8 h to 1.2 h to allow for stratification.

[0022] By adopting the above technical solution, the stirring rate after adding water is controlled within a suitable range. This provides sufficient impetus for the dissolution of salts in the reaction product, promoting rapid and uniform dispersion and dissolution, avoiding incomplete local dissolution and the formation of solid residues. It also avoids excessive foaming or high energy consumption due to excessive stirring, maintaining stable temperature and pressure in the system. A reasonable setting of the settling time after deammoniation, adapted to the density difference between the organic and aqueous phases, promotes thorough separation of the two phases, breaking any potential emulsification. Emulsification can lead to entrainment between the two phases, reducing the purity of the organic phase. A clear phase interface prevents the aqueous phase from affecting subsequent dehydration and solid-liquid separation, laying the foundation for efficient purification of the target product.

[0023] Preferably, in step S2, the removed ammonia is treated by water absorption, and the temperature of the absorption water is 10°C to 25°C; in step S3, the static stratification is carried out at an ambient temperature of 20°C to 30°C.

[0024] By adopting the above technical solution, the removed ammonia gas is treated by water absorption, leveraging the water-soluble nature of ammonia to achieve resource recovery and reuse. Controlling the absorption water temperature within a suitable range improves ammonia solubility and reduces loss through dispersion, while avoiding excessively low temperatures that reduce the absorption rate or excessively high temperatures that weaken dissolution efficiency, ensuring sufficient ammonia absorption to prepare ammonia water for secondary utilization. The set temperature for static separation in step S3 is reasonable, maintaining stable physical properties of the organic and aqueous phases, avoiding problems such as increased viscosity and slower separation rate due to excessively low temperatures, or volatilization and emulsification of the organic phase due to excessively high temperatures. This temperature parameter is precisely matched to the separation system in step S2, ensuring a clear interface between the two phases, improving the purity and efficiency of organic phase separation, and providing good preconditions for subsequent dehydration and solid-liquid separation processes.

[0025] In summary, this application has the following beneficial effects: 1. This application uses liquid ammonia as the sole reaction medium and does not introduce other organic solvents. Combined with low-temperature reaction conditions and a high molar ratio of 1:50 to 1:100, as well as precise control of the cooling pressure range and heating rate, and stable pumping of o-chlorobenzyl chloride through a metering pump, side reactions such as polyamine formation are effectively suppressed, VOC emissions are reduced, and the effects of improved reaction selectivity and resource recycling are achieved.

[0026] 2. In this application, anhydrous sodium sulfate is preferably used to dehydrate the organic phase. Its particle size and amount are reasonably set, and the filtration operation with controllable filter medium pore size and vacuum pressure is combined with the control of the ambient temperature for static stratification, so that the moisture and solid impurities in the product are efficiently removed, and the purity of the product is improved.

[0027] 3. The method of this application simplifies the synthesis process into three core steps: amination reaction and liquid ammonia recovery, water dissolution and deammoniation, and layered dehydration and solid-liquid separation. The operating parameters of each step, such as the amount of water added, the amount of liquid alkali, the stirring rate, the deammoniation temperature and time, are clearly defined, eliminating the need for additional complex purification steps. Therefore, the method achieves the effects of convenient operation, compact process and easy industrial implementation.

[0028] 4. This application achieves efficient evaporation and recovery of liquid ammonia by controlling the heating rate, and the moisture content of the recovered liquid ammonia is strictly controlled. At the same time, the removed ammonia gas is treated by water absorption and the temperature of the absorption water is controlled, realizing the recycling of ammonia resources and the compliant treatment of tail gas, and achieving the effects of low-carbon and environmentally friendly process and improved resource utilization.

[0029] 5. In this application, a metering pump is preferably used to control the pumping pressure and feeding time of o-chlorobenzyl chloride. Combined with clearly defined deammoniation temperature, vacuum conditions and deammoniation time, the key operating parameters work together to ensure that the reaction process is stable and controllable, avoid product performance differences caused by operational fluctuations, and achieve the effect of good process repeatability and stable product quality. Attached Figure Description

[0030] Figure 1 This is a flowchart of a method for synthesizing o-chlorobenzylamine provided in this application; Figure 2 The gas chromatogram of the o-chlorobenzylamine product prepared by the method described in Example 1 of this application is used for the purity determination of the product; Figure 3 The gas chromatogram of the o-chlorobenzylamine product prepared by the method described in Comparative Example 1 of this application is used for the purity determination of the product. Detailed Implementation

[0031] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0032] Technical concept: Existing technologies for the synthesis of o-chlorobenzylamine generally suffer from core problems such as poor reaction selectivity, insufficient environmental friendliness, and low resource utilization. The root cause lies in the failure to construct reaction systems and separation processes adapted to the characteristics of the amination reaction. Traditional methods either rely on organic solvents as reaction media, leading to excessive VOC emissions and increased difficulty in subsequent separation; or use ammonia as the amination reagent, which, due to insufficient amino donors and difficulty in controlling the reaction environment, easily triggers polyamine side reactions, generating impurities such as secondary and tertiary amines. Simultaneously, existing technologies lack precise control over the recovery of ammonia resources, resulting in the easy escape of unreacted ammonia or insufficient purity in recovery, causing resource waste and increasing environmental treatment pressure. These problems are interconnected, making it difficult for the synthesis process to simultaneously achieve product quality, environmental requirements, and industrialization benefits.

[0033] This technical solution addresses the aforementioned core issues, focusing on optimizing the reaction system, precisely controlling the process, and efficiently recovering resources. It constructs a closed-loop synthesis system through a series of synergistic technologies. Liquid ammonia is used as both the reaction medium and the amination reagent, eliminating organic solvents at the source. The endothermic properties of liquid ammonia evaporation are utilized to achieve low-temperature control of the system, while precise raw material ratios suppress polyamine side reactions. A stable feed process using metering pumps and precise temperature and pressure control of the ammonia stripping process enhances reaction stability and the purity of the recovered liquid ammonia. Subsequently, quantitative water dissolution of salts and liquid alkali are used to promote the release of the target product. Combined with negative pressure deammoniation and water absorption to recover ammonia resources, product purification is achieved through layering, dehydration, and precise filtration. Each technical approach specifically addresses the pain points of reaction selectivity, environmental friendliness, and resource utilization in existing technologies, forming a complete and synergistically optimized technical logic for reaction, separation, and recovery.

[0034] Example 1: This example provides a method for synthesizing o-chlorobenzylamine, including the following steps: S1. In a 1000L high-pressure reactor, liquid ammonia is used as the reaction medium and undergoes an amination reaction with o-chlorobenzyl chloride. After the reaction is completed, the liquid ammonia is distilled off and recovered. The amination reaction was carried out at a temperature of -25°C; the molar ratio of o-chlorobenzyl chloride to liquid ammonia was 1:75; o-chlorobenzyl chloride was pumped in using a metering pump over a period of 0.5 hours; after the addition was completed, the reaction was maintained at the above-mentioned temperature for 1 hour. Before the reaction, the system was cooled by evaporating some liquid ammonia. During the cooling process, the pressure inside the reactor dropped from 6 bar to 1.75 bar. The metering pump was pumped in at a pressure of 5.5 bar. After the reaction was completed, the liquid ammonia was evaporated at a heating rate of 7.5 °C / h. The recovered liquid ammonia contained 0.45% water by mass. S2. Add water to dissolve the reaction product obtained in step S1, then add liquid alkali and remove ammonia under negative pressure. The amount of water added is 4L / kg, based on the mass of o-chlorobenzyl chloride. In this embodiment, the amount of o-chlorobenzyl chloride used is 100kg, corresponding to the addition of 400L of water. The liquid alkali is a 32% sodium hydroxide aqueous solution, and the amount added is 95kg, based on 100kg of o-chlorobenzyl chloride. Negative pressure conditions refer to a system with an absolute pressure lower than atmospheric pressure, an operating temperature of 40℃ for ammonia removal, and a removal time of 1 hour. The stirring and dissolution rate after adding water is 200 rpm; after ammonia removal is completed, let stand for 1 hour to allow for layering. The removed ammonia gas is treated by water absorption, and the temperature of the absorption water is 17.5℃; S3. The material processed in step S2 is allowed to stand and separate into layers. The organic phase is then dehydrated and subjected to solid-liquid separation to obtain o-chlorobenzylamine. In this process, anhydrous sodium sulfate was used to dehydrate the organic phase. The amount of anhydrous sodium sulfate added was 3 kg, and the particle size of the anhydrous sodium sulfate was 125 μm per 100 kg of o-chlorobenzyl chloride. The dehydration stirring time was 0.5 h. Solid-liquid separation is achieved by vacuum filtration. The filtration medium used has a pore size of 0.55 μm, and the filtration is carried out under a vacuum pressure of -0.07 MPa. The static stratification was conducted at an ambient temperature of 25°C; relevant product testing data can be found here. Figure 2 .

[0035] Example 2: This example provides a method for synthesizing o-chlorobenzylamine, including the following steps: S1. In a 1000L high-pressure reactor, liquid ammonia is used as the reaction medium and undergoes an amination reaction with o-chlorobenzyl chloride. After the reaction is completed, the liquid ammonia is distilled off and recovered. The amination reaction was carried out at a temperature of -30°C; the molar ratio of o-chlorobenzyl chloride to liquid ammonia was 1:50; o-chlorobenzyl chloride was pumped in using a metering pump over a period of 0.4 hours; after the addition was completed, the reaction was maintained at the above-mentioned temperature for 1 hour. Before the reaction, the system was cooled by evaporating some liquid ammonia. During the cooling process, the pressure inside the reactor was reduced from 5 bar to 1.5 bar. The metering pump was pumped in at a pressure of 3 bar. After the reaction was completed, the liquid ammonia was evaporated at a heating rate of 5 °C / h. The recovered liquid ammonia contained 0.4% water by mass. S2. Add water to dissolve the reaction product obtained in step S1, then add liquid alkali and remove ammonia under negative pressure. The amount of water added is 3L / kg, based on the mass of o-chlorobenzyl chloride. In this embodiment, the amount of o-chlorobenzyl chloride used is 100kg, corresponding to the addition of 300L of water. The liquid alkali is a 32% sodium hydroxide aqueous solution, and the amount added is 90kg, based on 100kg of o-chlorobenzyl chloride. Negative pressure conditions refer to a system absolute pressure lower than atmospheric pressure, an operating temperature of 35℃ for ammonia removal, and an ammonia removal time of 0.8h. The stirring and dissolution rate after adding water is 100 rpm; after ammonia removal is completed, the mixture is allowed to stand for 0.8 h to allow for stratification. The removed ammonia gas is treated by water absorption, and the temperature of the absorption water is 10℃. S3. The material processed in step S2 is allowed to stand and separate into layers. The organic phase is then dehydrated and subjected to solid-liquid separation to obtain o-chlorobenzylamine. In this process, anhydrous sodium sulfate was used to dehydrate the organic phase. The amount of anhydrous sodium sulfate added was 2 kg, and the particle size of the anhydrous sodium sulfate was 50 μm per 100 kg of o-chlorobenzyl chloride. The dehydration stirring time was 0.5 h. Solid-liquid separation is achieved by vacuum filtration. The filtration medium used has a pore size of 0.1 μm and is carried out under a vacuum pressure of -0.05 MPa. The static stratification was carried out at an ambient temperature of 20°C.

[0036] Example 3: This example provides a method for synthesizing o-chlorobenzylamine, including the following steps: S1. In a 1000L high-pressure reactor, liquid ammonia is used as the reaction medium and undergoes an amination reaction with o-chlorobenzyl chloride. After the reaction is completed, the liquid ammonia is distilled off and recovered. The amination reaction was carried out at a temperature of -20°C; the molar ratio of o-chlorobenzyl chloride to liquid ammonia was 1:100; o-chlorobenzyl chloride was pumped in using a metering pump over a period of 0.6 hours; after the addition was completed, the reaction was maintained at the above-mentioned temperature for 1 hour. Before the reaction, the system was cooled by evaporating some liquid ammonia. During the cooling process, the pressure inside the reactor dropped from 7 bar to 2 bar. The metering pump was pumped in at a pressure of 8 bar. After the reaction was completed, the liquid ammonia was evaporated at a heating rate of 10 °C / h. The recovered liquid ammonia contained 0.5% water by mass. S2. Add water to dissolve the reaction product obtained in step S1, then add liquid alkali and remove ammonia under negative pressure. The amount of water added is 5L / kg, based on the mass of o-chlorobenzyl chloride. In this embodiment, the amount of o-chlorobenzyl chloride used is 100kg, corresponding to the addition of 500L of water. The liquid alkali is a 32% sodium hydroxide aqueous solution, and its addition amount is 100kg, based on 100kg of o-chlorobenzyl chloride. Negative pressure conditions refer to a system absolute pressure lower than atmospheric pressure, an operating temperature of 45℃ for ammonia removal, and an ammonia removal time of 1.2h. The stirring and dissolution rate after adding water is 300 rpm; after ammonia removal is completed, the mixture is allowed to stand for 1.2 hours to separate into layers. The removed ammonia gas is treated by water absorption, and the temperature of the absorption water is 25℃. S3. The material processed in step S2 is allowed to stand and separate into layers. The organic phase is then dehydrated and subjected to solid-liquid separation to obtain o-chlorobenzylamine. In this process, anhydrous sodium sulfate was used to dehydrate the organic phase. The amount of anhydrous sodium sulfate added was 4 kg, and the particle size of the anhydrous sodium sulfate was 200 μm per 100 kg of o-chlorobenzyl chloride. The dehydration stirring time was 0.5 h. Solid-liquid separation is achieved by vacuum filtration. The pore size of the filter medium used for vacuum filtration is 1 μm, and the vacuum filtration is carried out under a vacuum pressure of -0.09 MPa. The static stratification was carried out at an ambient temperature of 30°C.

[0037] Comparative Example 1: This comparative example provides a method for synthesizing o-chlorobenzylamine, including the following steps: S1. Add 100 kg of water and 300 kg of liquid ammonia to a 1000 L high-pressure reactor, start stirring, and cool down to below -20 °C by evaporating the liquid ammonia. The pressure inside the reactor drops from 3 bar to 0.1 bar. Use a metering pump to pump 100 kg of o-chlorobenzyl chloride into the reactor. The pumping process lasts for 0.5 h. After the pumping is completed, keep the reactor at -20 °C for 1 h. Then slowly raise the temperature. When the temperature reaches 20 °C and the vacuum degree inside the reactor reaches -0.09 MPa, the ammonia evaporation is finished. Observe the electronic scale of the liquid ammonia tank. The weight of the liquid ammonia has decreased by 35 kg. Take a sample from the ammonia compressor for testing. The moisture content of the recovered ammonia is 2.5%. S2. Add 400L of water to the high-pressure reactor after the liquid ammonia has been distilled off, and stir until the material is completely dissolved. Transfer the dissolved material to the free reactor. Add 95kg of 32% liquid alkali to the free reactor, turn on the negative pressure condition, raise the temperature to 40℃ and maintain it for 1h to remove the ammonia gas produced in the reaction. The ammonia gas is absorbed by the tail gas to prepare ammonia water. After the ammonia is distilled off, let it stand for 1h to separate the layers, and collect the upper organic phase. Add 3kg of anhydrous sodium sulfate to the collected organic phase, stir for 0.5h to dehydrate the organic phase, and filter after dehydration to obtain 88kg of crude organic product. S3. Transfer the above-mentioned crude organic product to a distillation vessel and distill under high vacuum conditions, wherein the vacuum degree reaches 500 Pa. Collect the fraction below 90°C to obtain 65 kg of o-chlorobenzylamine product. The relevant test results are attached. Figure 3 .

[0038] Test Item 1: Purity Determination of o-Chlorbenzylamine The standard used is GB / T30391-2013 "Determination of Purity of Organic Chemical Products by Gas Chromatography"; The purity of the o-chlorobenzylamine products from Examples 1-3 and Comparative Example 1 was determined using gas chromatography. The specific procedures were as follows: 0.1 g of each of the following samples were accurately weighed: 82 kg of product from Example 1, 80 kg of product from Example 2, 81 kg of product from Example 3, and 65 kg of product from Comparative Example 1. Each sample was placed in a 10 mL volumetric flask and diluted to the mark with anhydrous ethanol. The solutions were then shaken well to obtain the test sample solution. An HP-5 capillary column (30 m × 0.32 mm × 0.25 μm) was selected, and the column temperature program was set to the initial temperature. The sample was heated to 80℃ for 2 min, then increased to 200℃ at a rate of 10℃ / min and held for 5 min. The injection port temperature was 220℃, the flame ionization detector temperature was 250℃, the carrier gas was nitrogen, the flow rate was 1.0 mL / min, the split ratio was 20:1, and the injection volume was 1 μL. After the instrument stabilized, the above-mentioned sample solution was injected into the chromatograph. Each sample was measured in triplicate. The mass fraction of o-chlorobenzylamine in each sample was calculated using the area normalization method, which is the purity of the product. The purity results of Examples 1-3 and Comparative Example 1 were recorded.

[0039] Test Item 2: Calculation of o-chlorobenzylamine yield The standard used is HG / T2023-2019 "Calculation Method for Yield of Chemical Products"; The yield of o-chlorobenzylamine synthesis in Examples 1-3 and Comparative Example 1 was calculated as follows: First, the amount of o-chlorobenzylamine fed in each experiment was recorded as 100 kg. Based on the molar mass of o-chlorobenzylamine (161.01 g / mol) and the molar mass of o-chlorobenzylamine (141.59 g / mol), combined with the 1:1 molar conversion relationship in the reaction equation, the theoretical yield of o-chlorobenzylamine was calculated to be (100 × 1000 g / 161.01 g / mol) × 141.59 g / mol ≈ 87939 g, or 87.94 kg. Then, the actual mass of the o-chlorobenzylamine product obtained in each experiment was accurately weighed, with 82 kg in Example 1, 80 kg in Example 2, 81 kg in Example 3, and 65 kg in Comparative Example 1. The yield of each experiment was calculated, where yield = (actual yield / theoretical yield) × 100%. Each experiment was calculated in parallel three times and the average value was taken. The yield results of Examples 1-3 and Comparative Example 1 were recorded.

[0040] Test Item 3: Determination of Polyamine Impurity Content The reference standard is GB / T23961-2009 "Determination of Organic Amine Impurities by Gas Chromatography"; The content of polyamine impurities in the o-chlorobenzylamine products of Examples 1-3 and Comparative Example 1 was determined by gas chromatography. The specific operation was as follows: the sample preparation method and chromatographic conditions of Test Item 1 were used. The test sample solutions of each experiment were injected into the gas chromatograph. By comparing the retention times of o-chlorodibenzylamine standard and o-chlorotribenzylamine standard, the corresponding impurity peaks in the sample chromatograms were identified. The mass fraction of each impurity and the total impurity mass fraction were calculated by the area normalization method. Each sample was measured in parallel 3 times and the average value was taken. The total content of polyamine impurities in Examples 1, 2, 3 and Comparative Example 1 was recorded. This index is directly related to the purity determination results and can corroborate the high purity advantage of the product of the examples.

[0041] Table 1: Summary Table of Experimental Data for the Synthesis Process of o-Chlorobenzylamine

[0042] Combining Examples 1-3 and Comparative Example 1 with Table 1, it can be seen that Comparative Example 1 added water to the high-pressure reactor at the initial stage of the reaction, changing the reaction medium environment. Simultaneously, its liquid ammonia usage was significantly lower than that of the embodiments of this invention. These conditions collectively affected the selective pathway of the amination reaction. The presence of water and the relatively insufficient amount of ammonia increased the probability that the reaction intermediate would contact the raw materials and continue to react, generating polyamine byproducts. This not only consumed more raw materials, leading to a lower theoretical conversion rate, but also introduced more impurities into the final product that were difficult to remove through simple post-treatment. Furthermore, the high water content in the ammonia recovered in Comparative Example 1 indicated a difference in reaction system conditions compared to the examples, which may further affect the cleanliness and atom economy of the reaction process. Due to the different initial reaction conditions, the entire process required additional distillation purification steps to separate and purify the products, increasing the complexity and energy consumption of the operation.

[0043] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for synthesizing o-chlorobenzylamine, characterized in that: Includes the following steps: S1. In a high-pressure reactor, liquid ammonia is used as the reaction medium and undergoes an amination reaction with o-chlorobenzyl chloride. After the reaction is completed, the liquid ammonia is distilled off and recovered. S2. Add water to dissolve the reaction product obtained in step S1, then add liquid alkali and remove ammonia under negative pressure. S3. The material processed in step S2 is allowed to stand and separate into layers. The organic phase is then dehydrated and subjected to solid-liquid separation to obtain o-chlorobenzylamine.

2. The method for synthesizing o-chlorobenzylamine according to claim 1, characterized in that: In step S1, the reaction temperature of the amination reaction is -30℃ to -20℃; the molar ratio of o-chlorobenzyl chloride to liquid ammonia is 1:50 to 1:100; o-chlorobenzyl chloride is pumped in using a metering pump at a pressure of 3 bar to 8 bar and a feeding time of 0.4 h to 0.6 h; after the feeding is completed, the reaction is kept at the reaction temperature for 1 h.

3. The method for synthesizing o-chlorobenzylamine according to claim 1, characterized in that: In step S1, the system is cooled by evaporating some liquid ammonia before the reaction. During the cooling process, the pressure inside the reactor is reduced from 5 bar to 7 bar to 1.5 bar to 2 bar. After the reaction is completed, the liquid ammonia is evaporated at a heating rate of 5°C / h to 10°C / h.

4. The method for synthesizing o-chlorobenzylamine according to claim 1, characterized in that: In step S2, the amount of water added is 3L / kg to 5L / kg, based on the mass of o-chlorobenzyl chloride; the liquid alkali is a 32% sodium hydroxide aqueous solution, and the amount added is 90kg to 100kg, based on 100kg of o-chlorobenzyl chloride.

5. The method for synthesizing o-chlorobenzylamine according to claim 1, characterized in that: In step S2, the negative pressure condition refers to the system absolute pressure being lower than atmospheric pressure, the operating temperature for removing ammonia being 35°C to 45°C, and the ammonia removal time being 0.8h to 1.2h.

6. The method for synthesizing o-chlorobenzylamine according to claim 5, characterized in that: In step S3, anhydrous sodium sulfate is used to dehydrate the organic phase. The amount of anhydrous sodium sulfate added is 2 kg to 4 kg, based on 100 kg of o-chlorobenzyl chloride. The particle size of the anhydrous sodium sulfate is 50 μm to 200 μm, and the dehydration stirring time is 0.5 h.

7. The method for synthesizing o-chlorobenzylamine according to claim 1, characterized in that: In step S3, the solid-liquid separation is achieved by vacuum filtration. The pore size of the filter medium used for vacuum filtration is 0.1 μm to 1 μm, and the vacuum filtration is carried out under a vacuum pressure of -0.05 MPa to -0.09 MPa.

8. The method for synthesizing o-chlorobenzylamine according to claim 7, characterized in that: In step S1, the water content in the recovered liquid ammonia is ≤0.6% by mass.

9. The method for synthesizing o-chlorobenzylamine according to claim 1, characterized in that: In step S2, the stirring and dissolving rate after adding water is 100 rpm to 300 rpm; after the ammonia gas is removed, the mixture is allowed to stand for 0.8 h to 1.2 h to separate into layers.

10. The method for synthesizing o-chlorobenzylamine according to claim 1, characterized in that: In step S2, the removed ammonia is treated by water absorption, and the temperature of the absorption water is 10°C to 25°C; in step S3, the static stratification is carried out at an ambient temperature of 20°C to 30°C.

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