Process for recovering high purity tritylamine from rectification bottoms of production of benzylamine or dibenzylamine

Abstract

This invention provides a method for recovering high-purity tribenzylamine from the distillation by-products of benzylamine or dibenzylamine production. First, the distillation by-products containing tribenzylamine are subjected to molecular distillation to obtain crude tribenzylamine. Then, the crude tribenzylamine is purified by melt crystallization, followed by solid-liquid separation to obtain high-purity tribenzylamine with a purity of over 99.5%. This method operates at low temperatures, consumes little energy, and has a short residence time, which is beneficial for the purification of heat-sensitive tribenzylamine and reduces the generation of high boiling points. This method recovers high-purity tribenzylamine from the distillation by-products generated from the main benzylamine or dibenzylamine production line, reducing the amount of distillation by-products and minimizing resource waste, while recovering the valuable tribenzylamine. It achieves fully automated continuous production, high separation efficiency, and high product purity, without requiring the introduction of other solvents or generating any other waste. It has the advantages of energy saving and environmental friendliness, and is of great significance both economically and environmentally.

Description

Technical Field

[0001] This invention relates to the field of chemical product purification technology, and in particular to a method for recovering high-purity tribenzylamine from the distillation by-products of benzylamine or dibenzylamine production. Background Technology

[0002] Tribenzylamine, also known as tribenzylamine or triphenylmethylamine, is a colorless or yellow crystal. It is soluble in hot ethanol, ether, chloroform, and benzene, and very slightly soluble in water. It has a boiling point of 380–390℃, a melting point of 91–94℃, and a density of 0.991 g / cm3. It can be used in organic synthesis and for the separation and enrichment of elements that can form anions of complexes.

[0003] Tribenzylamine is typically produced by reacting benzylamine with benzyl alcohol. For example, Japanese Patent (Publication No. JPS63185942A) reports a method for producing tribenzylamine by reacting benzylamine with benzyl alcohol. This reaction is carried out in an inert organic solvent at a temperature of 140–200°C for 2–5 hours. Subsequently, the catalyst used in the reaction and the water generated in the reaction are removed, and tribenzylamine is obtained by distillation. Indian Patent (Publication No. IN 2008DE00669A) also discloses a similar synthetic route, in which benzylamine is first reacted with benzyl alcohol to obtain dibenzylamine, and then dibenzylamine is further reacted with benzyl alcohol to obtain tribenzylamine. It is not difficult to see that the above patents require the use of expensive raw materials benzyl alcohol and benzylamine, which makes the production and synthesis of tribenzylamine costly and economically inefficient.

[0004] Benzylamine and dibenzylamine are important chemical intermediates, especially dibenzylamine, which is a highly efficient and non-toxic sulfidation accelerator. Benzylamine and dibenzylamine are typically produced through benzonitrile hydrogenation or other amination processes. However, these processes often produce tribenzylamine as a byproduct. For example, a certain proportion of tribenzylamine is produced as a byproduct in the production of benzylamine and dibenzylamine via benzonitrile hydrogenation or the production of dibenzylamine from benzyl chloride and ammonia. The proportions of tribenzylamine byproducts in these processes are 5%–10% and 10%–15%, respectively. Typically, this tribenzylamine is concentrated in the final distillation byproduct. The distillation byproduct appears as a black, asphalt-like liquid with poor fluidity. Furthermore, due to its high boiling point, easy decomposition under overheating, and mixing with the high viscosity of the distillation byproduct, its recovery is extremely difficult. Therefore, no effective method for recovering tribenzylamine from benzylamine or dibenzylamine distillation byproducts has been reported. These byproducts are usually treated as hazardous waste, resulting in significant resource waste and environmental pollution.

[0005] In view of this, it is necessary to design an improved method for recovering high-purity tribenzylamine from the distillation residue of benzylamine or dibenzylamine production in order to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for recovering high-purity tribenzylamine from the distillation by-products of benzylamine or dibenzylamine production. The method involves two steps: molecular distillation and melt crystallization. This process recovers high-purity tribenzylamine from the distillation by-products generated during the main benzylamine or dibenzylamine production line, thereby reducing the amount of distillation by-products, minimizing resource waste and environmental pollution, and recovering valuable tribenzylamine, thus improving economic efficiency.

[0007] To achieve the above-mentioned objective, this invention provides a method for recovering high-purity tribenzylamine from the distillation residue of benzylamine or dibenzylamine production, comprising the following steps:

[0008] S1. The distillation residue containing tribenzylamine is subjected to molecular distillation to obtain a high-boiling product and crude tribenzylamine.

[0009] S2. The crude tribenzylamine obtained in step S1 is purified by melt crystallization, and high-purity tribenzylamine is obtained after solid-liquid separation; the purity of the high-purity tribenzylamine is above 99.5%.

[0010] As a further improvement of the present invention, in step S2, the melt crystallization process includes one or more of suspension crystallization, falling film crystallization, or static crystallization, preferably suspension crystallization.

[0011] As a further improvement of the present invention, in step S1, the molecular distillation method is to use a molecular distillation apparatus to separate the distillation residue containing tribenzylamine. The temperature of the heating medium of the molecular distillation apparatus is 10-20°C higher than the temperature of the material inside it, and the temperature of the material inside it is 100-180°C. The operating pressure of the molecular distillation apparatus is 1-50 Pa.

[0012] As a further improvement of the present invention, the suspension crystallization process is carried out using a suspension crystallizer, the temperature of the crude tribenzylamine entering the suspension crystallizer is 80-110°C, and the crystallization temperature in the suspension crystallizer is 60-90°C.

[0013] As a further improvement of the present invention, the equipment used for suspension crystallization also includes a gas circulation fan for providing circulating inert gas to the suspension crystallizer and a gas cooler for cooling the circulating inert gas, so as to ensure that a temperature difference is generated in the suspension crystallizer and the crystallization temperature is reached; the operating pressure of the suspension crystallizer and the circulation route of the circulating inert gas is 0.1 to 1 MPaG.

[0014] As a further improvement of the present invention, the suspension crystallizer includes a barrel body, a flow guide tube disposed inside the barrel body, a gas inlet and a liquid inlet disposed on the side of the barrel body, a gas distributor and a liquid distributor respectively communicating with the gas inlet and the liquid inlet, a gas outlet disposed on the upper part of the barrel body, and a solid-liquid mixture outlet disposed on the lower part of the barrel body; the gas distributor and the liquid distributor are horizontally disposed inside the barrel body and penetrate the flow guide tube, and the flow guide tube is a cylindrical structure without bottom at both ends.

[0015] As a further improvement of the present invention, the guide tube and the inner wall of the barrel are provided with a beam connecting the two, so that the upper and lower parts of the guide tube are not in contact with the barrel; the gas inlet and the liquid inlet are both located on the side of the barrel near the bottom; the gas distributor and the liquid distributor are both porous ring tube structures, so that the inert gas can fully contact and crystallize with the crude tribenzylamine material.

[0016] As a further improvement of the present invention, the diameter ratio of the guide tube to the suspension crystallizer barrel is (0.4-0.8):1, and the height ratio is (0.5-0.8):1; the hourly flow rate of the gas circulation fan is 1000-3000 times the volume of the suspension crystallizer, and the total air pressure of the gas circulation fan is 5-50 kPa; the gas cooler is a low-pressure-drop tubular cooler that cools the circulating inert gas to 25-40°C.

[0017] As a further improvement of the present invention, in step S2, the solid-liquid separation process is carried out using a solid-liquid separation device, which includes one of a washing tower, a centrifuge, and a filter, preferably a washing tower.

[0018] As a further improvement of the present invention, the heating medium of the molecular still is heat transfer oil or steam, and the cooling medium is circulating water.

[0019] As a further improvement of the present invention, a method for recovering high-purity tribenzylamine from the distillation residue of benzylamine or dibenzylamine production specifically includes the following steps:

[0020] SS1. The distillation residue containing tribenzylamine in the raw material tank is pumped to a molecular distillation apparatus. The material is separated by molecular distillation in the molecular distillation apparatus to obtain a high-boiling-point substance and crude tribenzylamine. The high-boiling-point substance is stored in a high-boiling-point tank, and the crude tribenzylamine is stored in a crude product tank.

[0021] SS2. The crude tribenzylamine obtained in step S1 is fed into a suspension crystallizer via a feed pump. It is purified by crystallization in the suspension crystallizer. Finally, it is separated into solid and liquid by a solid-liquid separation device to obtain a mother liquor enriched with impurities, which is stored in a mother liquor tank. The obtained tribenzylamine solid is remelted into liquid high-purity tribenzylamine and then stored in a finished product tank.

[0022] The beneficial effects of this invention are:

[0023] 1. This invention provides a method for recovering high-purity tribenzylamine from the distillation by-products of benzylamine or dibenzylamine production. The method comprises two steps: first, the distillation by-products containing tribenzylamine are subjected to molecular distillation to obtain crude tribenzylamine; then, the crude tribenzylamine is purified by melt crystallization, followed by solid-liquid separation to obtain high-purity tribenzylamine with a purity of 99.5% or higher. Compared to current tribenzylamine synthesis methods, this invention provides a method for recovering and obtaining high-purity tribenzylamine from the distillation by-products generated during the main benzylamine or dibenzylamine production line. This reduces the amount of distillation by-products, minimizing resource waste and environmental pollution, while simultaneously recovering the valuable tribenzylamine, which is of significant economic and environmental importance.

[0024] 2. The suspension crystallizer used in this invention, through its structural design, allows for sufficient contact between the low-temperature circulating inert gas and the material, creating a temperature difference that lowers the material's temperature and promotes crystallization. Furthermore, the circulating inert gas also thoroughly stirs the crude tribenzylamine, controlling its uniform subcooling and increasing the degree of crystallization, thereby improving the recovery rate and purity of tribenzylamine, and facilitating subsequent solid-liquid separation. The process route provided by this invention has advantages such as low operating temperature, low energy consumption, and short residence time, which is of great significance for the purification of heat-sensitive tribenzylamine, significantly reducing the occurrence of high boiling points.

[0025] 3. The suspension crystallizer of this invention has a simple structure. Compared with traditional scraper crystallizers, it eliminates the need for complex scraper (wearing parts), limiting plates, and moving parts design, as well as precision barrel machining. Therefore, the equipment operates more reliably, and the overall investment is lower. This method achieves fully automated continuous production. The equipment used is mature and reliable, with no special moving parts except for the pump. It boasts high separation efficiency, high product purity, and requires no other solvents or generates any other waste, offering advantages such as energy saving and environmental friendliness. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of the method for recovering high-purity tribenzylamine from the distillation residue of benzylamine or dibenzylamine production according to the present invention.

[0027] Figure 2This is a schematic cross-sectional view of the suspension crystallizer used in the method of recovering high-purity tribenzylamine from the distillation residue of benzylamine or dibenzylamine production according to the present invention.

[0028] Figure 3 for Figure 2 A schematic diagram of the specific structure of the gas distributor and liquid distributor in the intermediate suspension crystallizer.

[0029] Figure Labels

[0030] 110-Molecular distillation apparatus; 120-Raw material tank; 130-Raw material pump; 140-High boiling tank; 150-Crude product tank; 210-Suspension crystallizer; 211-Barrel body; 212-Gas inlet; 213-Liquid inlet; 214-Gas distributor; 215-Liquid distributor; 216-Gas outlet; 217-Solid-liquid mixture outlet; 218-Guide cylinder; 219-Beam frame; 220-Gas circulation fan; 230-Gas cooler; 240-Solid-liquid separation equipment; 250-Feed pump; 260-Mother liquor tank; 270-Finished product tank. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0033] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0034] A method for recovering high-purity tribenzylamine from distillation by-products in the production of benzylamine or dibenzylamine includes the following steps:

[0035] S1. The distillation byproducts containing tribenzylamine are subjected to molecular distillation to obtain high-boiling-point substances and crude tribenzylamine. The molecular distillation is carried out by using a molecular distillation apparatus 110 to separate the tribenzylamine-containing distillation byproducts. The temperature of the heating medium in the molecular distillation apparatus 110 is 10-20°C higher than the temperature of the material inside, and the temperature of the material inside is 100-180°C. The operating pressure of the molecular distillation apparatus 110 is 1-50 Pa.

[0036] S2. The crude tribenzylamine obtained in step S1 is purified by melt crystallization. After solid-liquid separation, high-purity tribenzylamine with a purity of over 99.5% is obtained. The suspension crystallization process is carried out in a suspension crystallizer 210. The temperature of the crude tribenzylamine entering the suspension crystallizer 210 is 80-110°C, and the crystallization temperature in the suspension crystallizer 210 is 60-90°C.

[0037] In particular, compared to the current route for the synthesis of tribenzylamine, this method recovers and obtains high-purity tribenzylamine from the distillation by-products generated from the main production line of benzylamine or dibenzylamine. This reduces the amount of distillation by-products, avoids resource waste and environmental pollution, and recovers valuable tribenzylamine, which is of great significance both economically and environmentally.

[0038] In step S2, the melt crystallization process includes one or more of suspension crystallization, falling film crystallization, or static crystallization, with suspension crystallization being preferred. Suspension crystallization is more conducive to the formation of crystals with small lattice defects and large particle size during tribenzylamine crystallization. Small lattice defects mean higher crystal purity, and large crystal particles are beneficial to the speed of subsequent solid-liquid separation, thereby increasing the yield of tribenzylamine.

[0039] Specifically, the equipment used in suspension crystallization also includes a gas circulation fan 220 that provides circulating inert gas to the suspension crystallizer 210, and a gas cooler 230 that cools the circulating inert gas to ensure that a temperature difference is generated within the suspension crystallizer 210 to reach the crystallization temperature. The temperature of the circulating inert gas exiting the suspension crystallizer 210 is 55–90°C, and after passing through the gas cooler 230, it is cooled to 25–40°C by circulating water. The operating pressure of the suspension crystallizer 210 and the circulation route of the circulating inert gas is 0.1–1 MPaG. The temperature of the circulating inert gas is related to the degree of crystallization of crude tribenzylamine in the suspension crystallizer 210, and therefore needs to be strictly controlled.

[0040] Please see Figure 2As shown, the suspension crystallizer 210 includes a barrel 211, a guide tube 218 disposed inside the barrel 211, a gas inlet 212 and a liquid inlet 213 disposed on the side of the barrel 211, a gas distributor 214 and a liquid distributor 215 respectively connected to the gas inlet 212 and the liquid inlet 213, a gas outlet 216 disposed at the upper part of the barrel 211, and a solid-liquid mixture outlet 217 disposed at the lower part of the barrel 211; the gas distributor 214 and the liquid distributor 215 are disposed inside the barrel 211 and penetrate the guide tube 218, which is a cylindrical structure without a bottom at the top and bottom. Thus, through the design of the suspension crystallizer 100, the low-temperature circulating inert gas is brought into full contact with the material, creating a temperature difference that lowers the material's temperature and induces crystallization. Furthermore, the circulating inert gas can thoroughly stir the crude tribenzylamine, controlling its uniform subcooling and improving the degree of crystallization, thereby increasing the recovery rate and purity of tribenzylamine and facilitating subsequent solid-liquid separation. The process route provided by this invention has advantages such as low operating temperature, low energy consumption, and short residence time, which is of great significance for the purification of heat-sensitive tribenzylamine and can greatly reduce the occurrence of high boiling points.

[0041] Specifically, the inner walls of the guide tube 218 and the barrel 211 are provided with beams 219 connecting the two, so that the upper and lower parts of the guide tube 218 are not in contact with the barrel 211; the gas inlet 212 and liquid inlet 213 of the suspension crystallizer 210 are both located on the side of the barrel 211 near the bottom; the gas distributor 214 and liquid distributor 215 are both porous annular tube structures, such as... Figure 3 As shown, this configuration ensures that the circulating inert gas comes into full contact with the crude tribenzylamine material and crystallizes. A gas distributor 214 is installed inside the suspension crystallizer 202, allowing the circulating inert gas to be dispersed through bubbling within the suspension crystallizer 210. The dispersed inert gas then comes into full contact with the material within the suspension crystallizer 210, ensuring the smooth operation of the crystallization process.

[0042] More specifically, the diameter ratio of the guide tube 218 to the barrel 211 of the suspension crystallizer 210 is (0.4~0.8):1, and the height ratio is (0.5~0.8):1; the hourly flow rate of the gas circulation fan 220 is 1000~3000 times the volume of the suspension crystallizer, the amount of circulating inert gas per ton of final product is 5~10t / h, and the total air pressure of the gas circulation fan 220 is 5~50kPa; the gas cooler 230 is a low-pressure drop tubular cooler that cools the circulating inert gas to 25~40℃.

[0043] The material in the suspension crystallizer 210 forms crystals under the cooling of inert gas, and the concentration of the crystals is 20% to 40%. The crystal slurry in the suspension crystallizer 210 is then separated into solid and liquid by a solid separation process. Depending on the requirements of different product contents, the solid-liquid separation process is carried out by a solid-liquid separation device 240, which includes one of a washing tower, a centrifuge, and a filter. When high-purity tribenzylamine is used as the target product, a washing tower is preferred.

[0044] The suspended crystallizer 210 used in this invention has a simple structure. Compared with the traditional scraper crystallizer, it does not require complex scraper (vulnerable parts), limit plate and moving equipment design, nor does it require precision barrel machining; therefore, the operation of the equipment is more reliable and the overall investment of the project is low.

[0045] In some specific embodiments, the heating medium of the molecular still 110 is heat transfer oil or steam, and the cooling medium is circulating water.

[0046] In some specific embodiments, the solid-liquid separation equipment 240 needs to backwash the finished product to improve the quality of the final product, and the proportion of finished product backwashing accounts for 5% to 10% of the final product.

[0047] Please see Figure 1 As shown, the method for recovering high-purity tribenzylamine from the distillation residue of benzylamine or dibenzylamine production specifically includes the following steps:

[0048] SS1. The distillation residue containing tribenzylamine in the raw material tank 120 is transported to the molecular distillation apparatus 110 via the raw material pump 130. The material is separated in the molecular distillation apparatus 110 by molecular distillation. The molecular distillation apparatus 110 is based on the principle of different molecular free paths to achieve material separation. It uses heat transfer oil or steam as the heating medium and circulating water as the cooling medium to cut the distillation residue containing tribenzylamine into different components to obtain high-boiling-point substances and crude tribenzylamine. The high-boiling-point substances are stored in the high-boiling-point tank 140, and the crude tribenzylamine is stored in the crude product tank 150.

[0049] SS2. The crude tribenzylamine obtained in step S1 is fed to the suspension crystallizer 210 via the feed pump 250. It is purified by crystallization in the suspension crystallizer 210. During the crystallization process, the gas circulation gas 220 and the gas cooler 230 are used in conjunction. Finally, the solid and liquid are separated by the solid-liquid separation device 240. The mother liquor enriched with impurities is stored in the mother liquor tank 260. The obtained solid is remelted into liquid high-purity tribenzylamine and stored in the finished product tank 270.

[0050] It should be noted that, depending on the process requirements, the high-boiling-point macromolecular substances obtained in step S1 can be transported back to the molecular distillation apparatus 110 via the raw material pump 130 for distillation; the mother liquor in the mother liquor tank 260 can be returned to the rectification process to recover valuable products, such as dibenzylamine.

[0051] The method for recovering high-purity tribenzylamine from the distillation byproducts of benzylamine or dibenzylamine production achieves fully automated continuous production. The equipment used is mature and reliable, with no special moving parts other than pumps. It has high separation efficiency, high product purity, and does not require the introduction of other solvents or generate any other waste. It has the advantages of saving energy and being environmentally friendly.

[0052] Example 1

[0053] This embodiment provides a method for recovering high-purity tribenzylamine from the distillation residue of benzylamine or dibenzylamine production, including the following steps:

[0054] SS1. The distillation by-products from the dibenzylamine production process (2.6 wt% dibenzylamine, 56.8 wt% tribenzylamine, and the remainder being other high-boiling components) are stored in feed tank 120. Subsequently, they are pumped to molecular distillation unit 110 via feed pump 130 at a flow rate of 3037.5 kg / h. The operating pressure of molecular distillation unit 110 is 5 Pa, the heating medium is heat transfer oil at 160°C, and the internal material temperature is 151°C. The low-boiling crude tribenzylamine enriched by molecular distillation is stored in crude product tank 150, accounting for 72 wt% of the feed, of which the tribenzylamine content is 80.9 wt%. The remaining 28% of the material is stored in high-boiling form in high-boiling tank 140.

[0055] SS2. The crude tribenzylamine in the crude product tank 150 is transported to the suspension crystallizer 210 through the feed pump 250. The gas circulation fan 220 and the gas cooler 230 are started to continuously supply cooled nitrogen gas into the suspension crystallizer 210 at a pressure of 0.5 MPaG. The temperature of the liquid is controlled by adjusting the air volume of the circulation fan. When production is stable, the solid content in the suspension crystallizer 210 is 28%, and the material temperature in the suspension crystallizer is 71℃; the nitrogen circulation air volume is 7.5 t / h.

[0056] SS3, the crystal slurry in the suspension crystallizer 210 is processed by the solid-liquid separation device 240 (washing tower) to achieve solid-liquid separation. The separated solid is melted into liquid and then transported to the finished product tank 270. 5% of the total material in 270 is used as the washing liquid for the filter cake layer of the washing tower, and the remaining 95% is discharged as product. The purity of the product is 99.91%; the product flow rate is 1250 kg / h. The mother liquor from the solid-liquid separation is stored in the mother liquor tank 260.

[0057] The production cost of the method for recovering high-purity tribenzylamine from the distillation by-products of benzylamine or dibenzylamine production in Example 1 was calculated, as shown in the table below.

[0058] Table 1. Cost calculation for the recovery of high-purity tribenzylamine in Example 1

[0059]

[0060]

[0061] Comparative Example 1

[0062] Comparative Example 1 provides a method for reacting benzylamine with benzyl alcohol to generate tribenzylamine, followed by purification and separation. The specific process is similar to that of the patent with publication number JP S63185942A in the background art. The material consumption cost of the process in Comparative Example 1 is calculated based on the theoretical yield and is shown in the table below.

[0063] Table 2 Cost Calculation of Tribenzylamine Synthesis Process in Comparative Example 1

[0064]

[0065] As shown in Tables 1 and 2, considering only the theoretical fixed cost, the method of recovering high-purity tribenzylamine from the distillation by-products of benzylamine or dibenzylamine production in Example 1 significantly reduces the cost compared to Comparative Example 1. Furthermore, the synthesis route in Comparative Example 1 would have a higher cost in actual production than the theoretical cost. Therefore, the method of this invention recovers and obtains high-purity tribenzylamine from the distillation by-products generated from the main benzylamine or dibenzylamine production line, which reduces the amount of distillation by-products while recovering the valuable tribenzylamine, thus having significant economic and environmental implications.

[0066] Example 2

[0067] Example 2 provides a method for recovering high-purity tribenzylamine from the distillation by-products of benzylamine or dibenzylamine production. The difference from Example 1 is that Example 2 uses a falling film crystallization method and a scraped thin film crystallizer. The rest is roughly the same as Example 1 and will not be described again here.

[0068] According to statistics, the final tribenzylamine product of the process in Example 2 has a purity of 99.6% and a yield of 1068 kg / h. Its purity and yield are not as good as the recovery process in Example 1. The reason is that the crystallization equipment and technology used in Example 1 are more conducive to forming tribenzylamine crystals with small lattice defects and large particle size than the traditional scraper crystallizer used in Example 2. Small lattice defects mean higher crystal purity, while large crystal particles are conducive to the subsequent solid-liquid separation speed, thus increasing the yield of tribenzylamine.

[0069] The production cost of the method for recovering high-purity tribenzylamine from the distillation by-products of benzylamine or dibenzylamine production in Example 2 is calculated as shown in the table below.

[0070] Table 3. Cost calculation for the recovery of high-purity tribenzylamine in Example 2.

[0071]

[0072] As can be seen from Table 3, crystallization using a scraper film crystallizer requires complex scraper, limiting plate and moving equipment design. The scraper is a vulnerable part, which increases the recycling cost. It also requires precision barrel machining, which increases the difficulty of the recycling process and reduces economic benefits.

[0073] In summary, this invention provides a method for recovering high-purity tribenzylamine from the distillation by-products of benzylamine or dibenzylamine production. This method is achieved through two steps: first, the distillation by-products containing tribenzylamine are subjected to molecular distillation to obtain crude tribenzylamine; then, the crude tribenzylamine is purified by melt crystallization, followed by solid-liquid separation to obtain high-purity tribenzylamine with a purity of 99.5% or higher. Compared to current tribenzylamine synthesis methods, this invention recovers and obtains high-purity tribenzylamine from the distillation by-products generated during the main benzylamine or dibenzylamine production line. This reduces the amount of distillation by-products while recovering the valuable tribenzylamine. Furthermore, this method achieves fully automated continuous production, utilizes mature and reliable equipment, requires no special moving parts other than pumps, has high separation efficiency, produces high-purity products, and requires no additional solvents or generate any other waste. It offers advantages in energy conservation and environmental friendliness, making it significant both economically and environmentally.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for recovering high-purity tribenzylamine from the distillation residue of benzylamine or dibenzylamine production, characterized in that, Includes the following steps: S1. The distillation byproducts containing tribenzylamine are subjected to molecular distillation to obtain high-boiling-point substances and crude tribenzylamine. The molecular distillation is performed by using a molecular distillation apparatus to separate the tribenzylamine-containing distillation byproducts. The temperature of the heating medium in the molecular distillation apparatus is 10-20°C higher than the temperature of the material inside, and the temperature of the material inside is 100-180°C. The operating pressure of the molecular distillation apparatus is 1-50 Pa. S2. The crude tribenzylamine obtained in step S1 is purified by suspension crystallization, and high-purity tribenzylamine is obtained after solid-liquid separation; the purity of the high-purity tribenzylamine is above 99.5%; the suspension crystallization process is carried out in a suspension crystallizer, the temperature of the crude tribenzylamine entering the suspension crystallizer is 80~110℃, and the crystallization temperature in the suspension crystallizer is 60~90℃; The suspension crystallizer includes a barrel body, a flow guide tube disposed inside the barrel body, a gas inlet and a liquid inlet disposed on the side of the barrel body, a gas distributor and a liquid distributor respectively communicating with the gas inlet and the liquid inlet, a gas outlet disposed on the upper part of the barrel body, and a solid-liquid mixture outlet disposed on the lower part of the barrel body; the gas distributor and the liquid distributor are horizontally disposed inside the barrel body and penetrate the flow guide tube, and the flow guide tube is a cylindrical structure without bottom at both ends; The guide tube and the inner wall of the barrel are provided with a beam connecting the two, so that the upper and lower parts of the guide tube are not in contact with the barrel; the gas inlet and the liquid inlet are both located on the side of the barrel near the bottom; the gas distributor and the liquid distributor are both porous ring tube structures to allow the inert gas to fully contact and crystallize the crude tribenzylamine material. The equipment used for suspension crystallization also includes a gas circulation fan that provides circulating inert gas to the suspension crystallizer and a gas cooler that cools the circulating inert gas to ensure that a temperature difference is generated in the suspension crystallizer to reach the crystallization temperature; the operating pressure of the suspension crystallizer and the circulation route of the circulating inert gas is 0.1~1 MPaG.

2. The process for recovering high purity trisbenzylamine from a rectification bottoms of production of benzylamine or dibenzylamine according to claim 1, characterized in that, The diameter ratio of the guide tube to the suspension crystallizer barrel is (0.4~0.8):1, and the height ratio is (0.5~0.8):1; the hourly flow rate of the gas circulation fan is 1000~3000 times the volume of the suspension crystallizer, and the total air pressure of the gas circulation fan is 5~50 kPa; the gas cooler is a low-pressure-drop tubular cooler that cools the circulating inert gas to 25~40℃.

3. The process for recovering high purity tris- benzylamine from a rectification bottoms of production of benzylamine or dibenzylamine according to claim 1, characterized by, In step S2, the solid-liquid separation process is carried out using solid-liquid separation equipment, which includes one of a washing tower, a centrifuge, and a filter.

4. The process for recovering high purity tris- benzylamine from a rectification bottoms of production of benzylamine or dibenzylamine according to claim 3, characterized by, The solid-liquid separation equipment is a washing tower.

5. The process for recovering high purity tris- benzylamine from a rectification bottoms produced from benzylamine or dibenzylamine according to claim 1, characterized by, The heating medium of the molecular still is heat transfer oil or steam, and the cooling medium is circulating water.

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