Process for the highly selective preparation of triethylenetetramine

Abstract

This invention relates to the field of fine chemical technology, specifically disclosing a process for the highly selective preparation of triethylenetetramine. The process includes the following steps: S1, using ethylenediamine and 1,2-dichloroethane as reactants, the reactants are passed through a trickle-bed reactor for reaction, and the outflowing reaction product is separated under reduced pressure, collecting the separated light and heavy components; S2, the light component is recycled back to the reactants and continues to pass through the trickle-bed reactor for reaction, and the outflowing reaction product is further separated under reduced pressure, collecting the separated light and heavy components; S3, the heavy component obtained in step S2 is mixed with an alcohol solvent or mixed with the heavy component obtained in step S1 and then mixed with an alcohol solvent, keeping the alcohol under reflux, cooling, centrifuging, and collecting the solid product; S4, the solid product is mixed with an alkaline solution for reaction, then filtered, and the filtrate is collected to obtain triethylenetetramine.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a process for the highly selective preparation of triethylenetetramine. Background Technology

[0002] Triethylenetetramine (TETA) is an aliphatic polyamine with a wide range of applications. Currently, industrially produced TETA is not obtained through directed synthesis, but mainly relies on its presence as a co-product in the production process of ethylenediamine (EDA), and is then separated by distillation. However, the purity of TETA obtained in this way is often relatively low (generally between 60% and 70%).

[0003] To obtain high-purity TETA, existing research has attempted to prepare triethylenetetramine by condensing 1,2-dichloroethane with ethylenediamine in the liquid phase. However, this reaction is typically strongly exothermic and readily generates large amounts of inorganic salt (sodium chloride) as byproducts. In traditional batch reactors, this reaction faces problems such as localized overheating, uneven mass transfer, and numerous side reactions. It also leads to poor product selectivity and high salt content in the product, making subsequent separation and purification difficult and ultimately hindering the acquisition of high-purity triethylenetetramine products. Summary of the Invention

[0004] The purpose of this invention is to provide a process for the highly selective preparation of triethylenetetramine, aiming to solve the problem that existing processes are difficult to obtain high-purity triethylenetetramine.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention provides a process for the highly selective preparation of triethylenetetramine, the process comprising the following steps: S1. Using ethylenediamine and 1,2-dichloroethane as reactants, the reactants are passed through a trickle bed reactor for reaction. The outflowing reaction products are separated under reduced pressure, and the separated light and heavy components (hydrochloride and high-boiling products) are collected. S2. The light component is circulated to the reaction raw material and continues to flow through the trickle bed reactor for reaction. The outflowing reaction product is further separated under reduced pressure, and the separated light and heavy components are collected. S3. Mix the heavy components obtained in step S2 with an alcohol solvent or mix them with the heavy components obtained in step S1 and then mix them with an alcohol solvent, keeping the alcohol under reflux, cooling, centrifuging, and collecting the solid product. S4. The solid product is mixed with an alkaline solution and reacted, then filtered, and the filtrate is collected to obtain triethylenetetramine.

[0006] Specifically, the highly selective process for preparing triethylenetetramine provided by this invention achieves the following excellent effects by mixing the separated light components with fresh reactants (1,2-dichloroethane and ethylenediamine) and then recycling them back into the reactor: ① Improved atom economy and yield: 1,2-dichloroethane and ethylenediamine are expensive chemical raw materials. Directly discarding the light components (containing a large amount of unreacted raw materials) would result in serious cost waste. However, by recycling the light components, the unreacted raw materials can be reintroduced into the reactor to continue participating in the reaction, significantly improving the overall utilization rate of the raw materials, increasing the yield, and reducing costs; ② Promoted chain growth and improved target product selectivity: The light components also contain a large amount of short-chain intermediates such as ethylenediamine (AES) and diethylenetriamine (DETA). When the light components are reintroduced into the reactor along with fresh reactants, they undergo further nucleophilic substitution reactions with 1,2-dichloroethane (leading to chain elongation) and are converted into the target product triethylenetetramine (TETA), thereby improving the reaction selectivity and product purity.

[0007] Furthermore, a process for the highly selective preparation of triethylenetetramine: the molar ratio of ethylenediamine to 1,2-dichloroethane in step S1 is (25-50):1.

[0008] Furthermore, a process for the highly selective preparation of triethylenetetramine: the flow rate of the reaction raw materials in step S1 through the trickle bed reactor is 2.5–10.0 ml / min.

[0009] Furthermore, a process for the highly selective preparation of triethylenetetramine is provided: the inner diameter of the trickle bed reactor is 6.0 mm and the length is 35 cm.

[0010] Furthermore, a process for the highly selective preparation of triethylenetetramine is provided: the reaction temperature in step S1 is 100–200 °C and the reaction pressure is 0.1–5.0 MPa.

[0011] Furthermore, a process for highly selective preparation of triethylenetetramine is provided: in step S1, the reaction products are separated under reduced pressure using a distillation column, with the distillation column temperature set to 80-100℃ and the pressure set to -0.0997--0.0990MPa. The light component is collected at the top of the distillation column and the heavy component is collected at the bottom.

[0012] Furthermore, a process for the highly selective preparation of triethylenetetramine is provided, wherein the recycling ratio of the light component to the reaction raw materials in step S2 is 3 to 15.

[0013] Furthermore, a process for the highly selective preparation of triethylenetetramine: the alcohol solvent in step S3 is anhydrous methanol.

[0014] Furthermore, a process for the highly selective preparation of triethylenetetramine: the reflux time in step S3 is 2-3 hours.

[0015] Furthermore, a process for the highly selective preparation of triethylenetetramine: in step S3, the mass ratio of the heavy component to the alcohol solvent is 1:(1.1~2.5).

[0016] The beneficial effects of this invention are: The highly selective preparation process of triethylenetetramine provided by this invention is a process carried out in a trickle bed reactor and obtains highly selective triethylenetetramine products through a high circulation ratio. This process fully utilizes the excellent heat transfer performance and efficient mass transfer surface area of ​​the trickle bed, enhancing the heterogeneous contact between the reactants ethylenediamine (EDA) and 1,2-dichloroethane (EDC), achieving efficient conversion under mild reaction conditions, avoiding the problem of numerous side reactions caused by local overheating, and preventing poor product selectivity.

[0017] The highly selective process for preparing triethylenetetramine provided by this invention further enhances the relative selectivity of triethylenetetramine and improves product purity (the triethylenetetramine content in the product can reach 98.0%) by utilizing the light components in the recycled products, which both utilizes unreacted raw materials and suppresses the regeneration of byproducts. Based on the reversibility of the reaction, this invention proposes a novel triethylenetetramine preparation process with high selectivity, simple separation, and high yield, which can significantly reduce the production cost of triethylenetetramine. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Example 1

[0020] This embodiment 1 provides a process for the highly selective preparation of triethylenetetramine, which includes the following steps: S1. Using ethylenediamine (EDA) and 1,2-dichloroethane (EDC) as reactants, 4000.0 g (66.6 mol) of ethylenediamine and 200.0 g (2.02 mol) of 1,2-dichloroethane were mixed uniformly at 20 °C, and then flowed through a trickle bed reactor at a flow rate of 5.0 ml / min. The inner diameter of the trickle bed reactor was 6.0 mm and the length was 35.0 cm. The inlet temperature of the trickle bed reactor was set to 180 °C and the outlet temperature was set to 195 °C. The reaction products flowing out of the reactor were separated by vacuum distillation in a distillation column. The column bottom temperature was 90 °C and the column bottom pressure was -0.0995 MPa. The light component was collected from the top of the column, cooled, and collected (approximately 3755 g). The heavy component (hydrochloride and high-boiling product) was collected from the bottom of the column, cooled, and collected (approximately 445 g). S2. The light components described above are circulated to the reaction raw materials (the circulation ratio is controlled at 8.4, that is, the mass ratio of light components to reaction raw materials is 8.4:1) and continue to flow through the trickle bed reactor at a flow rate of 5.0 ml / min for reaction. Then, the reaction products flowing out of the reactor are further separated under reduced pressure in a distillation column, and the separated light components and heavy components are collected. S3. Mix the heavy components obtained in step S2 with the heavy components obtained in step S1, and then stir and mix with about 600.0g of anhydrous methanol. The temperature of the mixture is 65°C, and the mixture is refluxed. After the methanol is kept in reflux for 2.5 hours, it is cooled to 25°C, centrifuged, and the solid product is collected. S4. The solid product is mixed with alkaline solution and reacted, then filtered, and the filtrate is collected. After chromatographic analysis, the content of linear triethylenetetramine in the product is about 98.2%.

[0021] Example 2

[0022] This embodiment 2 provides a process for the highly selective preparation of triethylenetetramine, which includes the following steps: S1. Using ethylenediamine (EDA) and 1,2-dichloroethane (EDC) as reactants, 3500.0 g of ethylenediamine and 200.0 g of 1,2-dichloroethane were mixed uniformly at 20°C, and then flowed through a trickle bed reactor at a flow rate of 2.5 ml / min. The inner diameter of the trickle bed reactor was 6.0 mm and the length was 35.0 cm. The inlet temperature of the trickle bed reactor was set to 175°C and the outlet temperature was set to 190°C. The reaction products flowing out of the reactor were separated by vacuum distillation in a distillation column. The column bottom temperature was 80°C and the column bottom pressure was -0.0997 MPa. The light component was collected from the top of the column, cooled, and collected (approximately 3260 g). The heavy components (hydrochloride and high-boiling products) were collected from the bottom of the column, cooled, and collected (approximately 440 g). S2. The light components described above are circulated to the reaction raw materials (the circulation ratio is controlled at 7.4, that is, the mass ratio of light components to reaction raw materials is 7.4:1) and continue to flow through the trickle bed reactor at a flow rate of 2.5 ml / min for reaction. Then, the reaction products flowing out of the reactor are further separated under reduced pressure in a distillation column, and the separated light components and heavy components are collected. S3. Mix the heavy components obtained in step S2 with the heavy components obtained in step S1, and then stir and mix with about 800.0g of anhydrous methanol. The temperature of the mixture is 65°C, and the mixture is refluxed. After the methanol is kept in reflux for 2.5 hours, it is cooled to 25°C, centrifuged, and the solid product is collected. S4. The solid product is mixed with alkaline solution and reacted, then filtered, and the filtrate is collected. After chromatographic analysis, the content of linear triethylenetetramine in the product is about 97.3%.

[0023] Example 3

[0024] This embodiment 3 provides a process for the highly selective preparation of triethylenetetramine, which includes the following steps: S1. Using ethylenediamine (EDA) and 1,2-dichloroethane (EDC) as reactants, 6000.0 g of ethylenediamine and 200.0 g of 1,2-dichloroethane were mixed uniformly at 20°C, and then flowed through a trickle bed reactor at a flow rate of 6.0 ml / min. The inner diameter of the trickle bed reactor was 6.0 mm and the length was 35.0 cm. The inlet temperature of the trickle bed reactor was set to 190°C and the outlet temperature was set to 195°C. The reaction products flowing out of the reactor were separated by vacuum distillation in a distillation column. The column bottom temperature was 100°C and the column bottom pressure was -0.099 MPa. The light component was collected from the top of the column, cooled, and collected. The heavy components (hydrochloride salts and high-boiling products) were collected from the bottom of the column, cooled, and collected. S2. The light components described above are circulated to the reaction raw materials (the circulation ratio is controlled at 12.9, that is, the mass ratio of light components to reaction raw materials is 12.9:1) and continue to flow through the trickle bed reactor at a flow rate of 6.0 ml / min for reaction. Then, the reaction products flowing out of the reactor are further separated under reduced pressure in a distillation column, and the separated light components and heavy components are collected. S3. Mix the heavy components obtained in step S2 with the heavy components obtained in step S1, and then stir and mix with about 900.0g of anhydrous methanol. The temperature of the mixture is 65°C, and the mixture is refluxed. After the methanol is kept in reflux for 2.5 hours, it is cooled to 25°C, centrifuged, and the solid product is collected. S4. The solid product is mixed with alkaline solution and reacted, then filtered, and the filtrate is collected. After chromatographic analysis, the content of linear triethylenetetramine in the product is about 98.5%.

[0025] Example 4

[0026] This embodiment 4 provides a process for the highly selective preparation of triethylenetetramine, which includes the following steps: S1. Using ethylenediamine and 1,2-dichloroethane as reactants, ethylenediamine and 1,2-dichloroethane are mixed uniformly at 20°C, and then flowed through a trickle bed reactor at a flow rate of 5.0 ml / min. The inner diameter of the trickle bed reactor is 6.0 mm and the length is 35.0 cm. The inlet temperature of the trickle bed reactor is set to 180°C and the outlet temperature is set to 195°C. The reaction products flowing out of the reactor are separated by vacuum distillation in a distillation column. The column bottom temperature is 90°C and the column bottom pressure is -0.0995 MPa. The light component is collected from the top of the column, cooled, and collected. The heavy components (hydrochloride salt, high-boiling product) are collected from the bottom of the column, cooled, and collected. S2. The light components described above are circulated to the reaction raw materials (the circulation ratio is controlled at 4.3, that is, the mass ratio of light components to reaction raw materials is 4.3:1) and continue to flow through the trickle bed reactor at a flow rate of 5.0 ml / min for reaction. Then, the reaction products flowing out of the reactor are further separated under reduced pressure in a distillation column, and the separated light components and heavy components are collected. S3. The heavy components obtained in step S2 are directly mixed with anhydrous methanol. The temperature of the mixture is 65°C, and the mixture is refluxed. After the methanol is kept in reflux for 2.5 hours, it is cooled to 25°C, centrifuged, and the solid product is collected. S4. The solid product is mixed with alkaline solution and reacted, then filtered, and the filtrate is collected. After chromatographic analysis, the content of linear triethylenetetramine in the product is about 96.7%.

[0027] The main difference between Example 4 and Example 1 is that in step S3 of Example 4, the heavy component from step S2 is mixed with anhydrous methanol alone, instead of being mixed with the heavy component from step S1. The other conditions are the same as in Example 1.

[0028] The present invention provides a highly selective process for preparing triethylenetetramine, which utilizes the difference in solubility of different substances in alcohol under reflux conditions to selectively precipitate the hydrochloride salt of the target product, achieving complete solid-liquid separation and improving product purity. This process abandons the traditional method of obtaining triethylenetetramine through distillation, eliminating the energy-intensive distillation process in traditional methods, resulting in not only high product purity but also lower costs. Furthermore, the process of this invention is designed to recycle the separated light components, which not only significantly improves the utilization rate of raw materials but also enhances the selectivity of the reaction. Simultaneously, the reflux of the light components creates a favorable dilution atmosphere within the reactor, further suppressing the occurrence of side reactions and significantly improving the selectivity of the reaction system for triethylenetetramine, thereby increasing product purity.

[0029] The above-described preferred embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of the invention. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A process for the highly selective preparation of triethylenetetramine, characterized in that, The process includes the following steps: S1. Using ethylenediamine and 1,2-dichloroethane as reactants, the reactants are passed through a trickle bed reactor for reaction. The outflowing reaction products are separated under reduced pressure, and the separated light and heavy components are collected. S2. The light component is circulated to the reaction raw material and continues to flow through the trickle bed reactor for reaction. The outflowing reaction product is further separated under reduced pressure, and the separated light and heavy components are collected. S3. Mix the heavy components obtained in step S2 with an alcohol solvent or mix them with the heavy components obtained in step S1 and then mix them with an alcohol solvent, keeping the alcohol under reflux, cooling, centrifuging, and collecting the solid product. S4. The solid product is mixed with an alkaline solution and reacted, then filtered, and the filtrate is collected to obtain triethylenetetramine.

2. The process for highly selectively preparing triethylenetetramine according to claim 1, characterized in that, The molar ratio of ethylenediamine to 1,2-dichloroethane in step S1 is (25-50):

1.

3. The process for highly selectively preparing triethylenetetramine according to claim 1, characterized in that, The flow rate of the reaction raw materials in step S1 through the trickle bed reactor is 2.5 to 10.0 ml / min.

4. A process for highly selectively preparing triethylenetetramine according to claim 1 or 3, characterized in that, The trickle bed reactor has an inner diameter of 6.0 mm and a length of 35 cm.

5. A process for highly selective preparation of triethylenetetramine according to any one of claims 1 to 4, characterized in that, The reaction temperature in step S1 is 100–200℃ and the reaction pressure is 0.1–5.0 MPa.

6. The process for highly selective preparation of triethylenetetramine according to claim 1, characterized in that, In step S1, a distillation column is used to separate the reaction products under reduced pressure. The temperature of the distillation column is set to 80-100℃ and the pressure is set to -0.0997--0.0990MPa. The light components are collected at the top of the distillation column and the heavy components are collected at the bottom of the column.

7. The process for highly selective preparation of triethylenetetramine according to claim 1, characterized in that, The recycling ratio of the light component to the reaction raw materials in step S2 is 3 to 15.

8. The process for highly selectively preparing triethylenetetramine according to claim 1, characterized in that, Anhydrous methanol is selected as the alcohol solvent in step S3.

9. The process for highly selectively preparing triethylenetetramine according to claim 1, characterized in that, The reflux time in step S3 is 2 to 3 hours.

10. The process for highly selective preparation of triethylenetetramine according to claim 1, characterized in that, In step S3, the mass ratio of the heavy component to the alcohol is 1:(1.1 to 2.5).