Process for the production of diethyltoluene diamine by molecular distillation

Abstract

The application discloses a process for producing diethyltoluene diamine by a molecular rectification method and relates to the technical field of diethyltoluene diamine production. The process comprises the following steps: filtering and removing impurities from a crude product prepared by alkylation, sequentially removing light components, monoethyltoluene diamine impurities and heavy component residues through three-stage short-range molecular rectification, and finally cooling and packaging under nitrogen protection to obtain a finished product. In the process, a lanthanum oxide and ZSM-5 molecular sieve compound catalyst is used to prepare the crude product, and different structure wiped film distillation equipment is matched to accurately control parameters such as vacuum degree, temperature and rotating speed to realize directional separation. The process has high finished product purity and comprehensive yield, low energy consumption, can efficiently prepare high-purity diethyltoluene diamine, and is suitable for industrialized continuous production.

Description

Technical Field

[0001] This invention relates to the field of diethyltoluenediamine production technology, and in particular to a process for producing diethyltoluenediamine by molecular distillation. Background Technology

[0002] Diethyltoluenediamine (DETDA) is a high-performance aromatic diamine curing agent and chain extender, characterized by high reactivity, fast curing speed, good heat resistance, and excellent mechanical properties. It is widely used in polyurethane elastomers, epoxy resin curing, adhesives, coatings, aerospace composite materials, and other fields, and is a core auxiliary raw material in the high-end fine chemical and new materials industries. With the rapid development of my country's high-end polyurethane industry, the market's requirements for the purity, color, stability, and batch consistency of DETDA products continue to increase. High-purity, low-color, and low-impurity DETDA products have become the mainstream demand in the industry.

[0003] Existing synthesis processes mostly employ an aromatic amine-aluminum catalytic system or a fixed-bed reactor method, conducting reactions at relatively high temperatures (200~350℃) and pressures (1.0~6.0MPa). Although some processes reduce costs through catalyst recycling, unreacted toluene diamine, over-alkylation byproducts, and trace amounts of metal catalyst residues are still inevitably mixed into the reaction products. If these impurities are not thoroughly removed, they will seriously affect the mechanical properties and storage stability of downstream polyurethane materials. Traditional purification methods mainly rely on vacuum distillation or water-washing / alkali-washing processes. However, DETDA has a high boiling point and is heat-sensitive; conventional vacuum distillation requires maintaining high temperatures for extended periods, which easily triggers side reactions such as deamination, demethylation, and N-alkylation, leading to a darker product color and a decrease in amine value. Furthermore, the alkali-washing and water-washing processes not only generate large amounts of high-salt wastewater, increasing environmental treatment costs, but also destroy the recovery value of some catalytic systems.

[0004] In recent years, some companies have attempted to improve selectivity by optimizing catalysts (such as sol-gel methods or supported catalysts), but the post-processing of crude products remains a bottleneck restricting product quality. Molecular distillation technology, with its high vacuum, short residence time, and low-temperature operation characteristics, exhibits unique advantages in the separation of heat-sensitive, high-boiling-point organic compounds. Introducing it into DETDA's purification process is expected to solve the technical shortcomings of traditional processes, such as severe thermal degradation, high energy consumption, and significant environmental impact.

[0005] In view of this, the present invention provides a process for producing diethyltoluene diamine by molecular distillation, which improves purity and reduces energy consumption in the separation process while ensuring product yield. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a process for producing diethyltoluene diamine by molecular distillation, which improves purity and reduces energy consumption in the separation process while ensuring product yield.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a process for producing diethyltoluene diamine by molecular distillation, comprising the following steps: Step S1, Crude Product Pretreatment: The crude diethyltoluenediamine obtained by the alkylation reaction of toluenediamine is filtered through a precision filter to remove solid catalyst residue and mechanical impurities, resulting in a clear crude liquid; Step S2, primary molecular distillation to remove light components: The clarified crude liquid is preheated to 80-90℃ and fed into a primary short-path molecular distillation apparatus. The distillation vacuum is controlled at 800-900Pa, the evaporation temperature at 110-120℃, the scraper rotation speed at 280-320r / min, the feed flow rate at 15-20L / h, and the nitrogen micro-positive pressure at 0.020MPa. Light component fractions and primary purified liquid are obtained. The light component fractions are unreacted toluene diamine and low molecular weight hydrocarbon impurities. Step S3, Secondary Molecular Distillation for Impurity Removal: The primary purified liquid is preheated to 100-110℃ and fed into a secondary short-path molecular distillation apparatus. The distillation vacuum is controlled at 600-700Pa, the evaporation temperature at 135-145℃, the scraper rotation speed at 320-360r / min, and the feed flow rate at 12-16L / h. The liquid film shearing effect is enhanced to amplify the difference in free path of isomer molecules, and the monoethyltoluene diamine impurity is directionally removed, resulting in the separation of the medium and light impurity fraction and the secondary purified liquid. Step S4, Three-stage molecular distillation purification: The secondary purified liquid is preheated to 120-130℃ and fed into a three-stage short-path molecular distillation device. The distillation vacuum is controlled at 300-400Pa, the evaporation temperature at 165-175℃, the scraper rotation speed at 360-400r / min, and the feed flow rate at 10-14L / h. The heavy component residue and the high-purity diethyltoluene diamine product fraction are separated. Step S5, Finished product cooling and packaging: The finished product fraction obtained from the three-stage distillation is cooled to 30-40℃ by a low-temperature cooler, and sealed and packaged under nitrogen protection in a closed-loop oxygen control process to obtain high-purity diethyltoluene diamine finished product.

[0008] Preferably, the filtration accuracy in step S1 is 0.5 μm.

[0009] Preferably, the preparation process of crude diethyltoluenediamine in step S1 is as follows: using m-toluenediamine as the main raw material and high-purity ethylene as the alkylating agent, a customized catalyst is used; the molar ratio of m-toluenediamine to ethylene is controlled at 1:(2.05~2.20), and the catalyst feed mass is 2.5%~4.0% of the m-toluenediamine feed mass; under nitrogen replacement protection and an oxygen-free environment, the reaction temperature is controlled at 120~160℃ and the reaction pressure at 1.0~6.0MPa, and a continuous catalytic alkylation reaction is carried out, with a reaction residence time of 2.5~4.0h; after the alkylation reaction is completed, the mixture is sent to a flash evaporator for flash evaporation at atmospheric pressure and constant temperature of 80℃ to quickly remove unreacted ethylene, trace amounts of low-carbon hydrocarbons and other gaseous light components, to obtain crude DETDA with an initial purity of 90%~92%.

[0010] Preferably, the customized catalyst is a mixture of lanthanum oxide and ZSM-5 molecular sieve in a mass ratio of (1-3):100.

[0011] Preferably, the first-stage short-range molecular distillation equipment in step S2 adopts a large-gap, low-shear scraping film structure, combined with an oxygen partial pressure adaptive nitrogen protection mode.

[0012] Preferably, the two-stage short-range molecular distillation equipment in step S3 adopts a small-gap, high-shear variable-gap scraping film structure, and dynamically and adaptively adjusts the nitrogen micro-positive pressure to 0.022 MPa.

[0013] Preferably, the three-stage short-range molecular distillation equipment in step S4 adopts a steady-state equal-gap homogeneous scraping film structure, and dynamically and adaptively adjusts the nitrogen micro-positive pressure to 0.025 MPa.

[0014] Preferably, the first-stage short-range molecular distillation equipment, the second-stage short-range molecular distillation equipment, and the third-stage short-range molecular distillation equipment are all scraped film type short-range molecular distillation devices, with a distance of 20-30 mm between the evaporation surface and the condensation surface, and the condensation temperature is controlled at 25-35℃.

[0015] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The process for producing diethyltoluene diamine by molecular distillation disclosed in this invention utilizes the characteristics of high vacuum, low temperature, and extremely short material residence time of molecular distillation. The distillation parameters are designed with a three-stage gradient heating, depressurization, and speed regulation. The highest evaporation temperature throughout the process is much lower than that of traditional high-temperature distillation, thus avoiding the thermal decomposition and deterioration problems of heat-sensitive DETDA materials. At the same time, impurities are removed through three-stage distillation: the first stage removes unreacted toluene diamine and light hydrocarbons, the second stage removes the isomer monoethyltoluene diamine in a directional manner, and the third stage separates heavy component catalyst residues and heavy by-products. The precise removal of impurities at each stage can purify the crude product with an initial purity of 90%~92% to a high-purity finished product. The product is clear and bright in color, without yellowing or blackening, and has a stable amine value and extremely low impurity content.

[0016] (2) The process for producing diethyltoluene diamine using molecular distillation disclosed in this invention employs physical molecular separation and purification technology throughout the entire process. It eliminates the need for wet processes such as water washing, alkali washing, and solvent extraction, and generates no wastewater or solid waste pollutants during production. This eliminates the environmental pressure of treating high-salt wastewater and significantly reduces environmental protection operation and maintenance costs. At the same time, the process can completely preserve the material characteristics of the reaction system, and the catalyst residue is centrally separated without component damage. It can achieve efficient recovery and recycling of the catalyst, and significantly improve the utilization rate of alkylation raw materials. Under the premise of ensuring high product yield, it effectively reduces raw material loss and overall production energy consumption, thus achieving both economic and environmental benefits.

[0017] (3) The process for producing diethyltoluenediamine by molecular distillation disclosed in this invention adopts a three-stage differentiated scraped-film molecular distillation equipment structure. The first stage has a large gap and low shear structure to protect the material from secondary reactions. The second stage has a small gap and high shear structure to enhance liquid film disturbance and amplify the difference in the free path of isomer molecules, thereby achieving the directional removal of trace amounts of difficult-to-separate impurities. The third stage has a steady-state homogeneous scraped-film structure to ensure the uniformity and stability of the finished product composition. At the same time, it is equipped with an adaptive control system for gradient vacuum, feed flow rate, and nitrogen micro-positive pressure to construct a precise molecular separation environment, which solves the technical problem that traditional processes cannot efficiently remove isomer impurities, and greatly improves the purity of product components and batch consistency.

[0018] (4) The process for producing diethyltoluene diamine by molecular distillation disclosed in this invention adopts a sealed packaging process with low temperature cooling, closed-loop oxygen control throughout the process and nitrogen micro-positive pressure protection after the finished product is purified. This effectively isolates oxygen, water vapor and impurity pollution, inhibits subsequent oxidation and deterioration of the finished product, solves the problem of poor storage stability of high-purity DETDA finished products, greatly extends the product shelf life, and ensures that the quality of different batches of products is highly consistent, which is suitable for the needs of continuous and stable mass production in industrialization. Detailed Implementation

[0019] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. Example

[0020] A process for producing diethyltoluenediamine using molecular distillation includes the following steps: Step S1, Crude Product Pretreatment: The crude diethyltoluenediamine obtained by the alkylation reaction of toluenediamine is filtered through a precision filter to remove solid catalyst residue and mechanical impurities, resulting in a clear crude liquid; Step S2, primary molecular distillation to remove light components: The clarified crude liquid is preheated to 80°C and fed into a primary short-path molecular distillation apparatus. The distillation vacuum is controlled at 800Pa, the evaporation temperature at 110°C, the scraper rotation speed at 280r / min, the feed flow rate at 15L / h, and the nitrogen micro-positive pressure at 0.020MPa. Light component fraction and primary purified liquid are obtained. The light component fraction is unreacted toluene diamine and low molecular weight hydrocarbon impurities. Step S3, Secondary Molecular Distillation for Impurity Removal: The primary purified liquid is preheated to 100°C and fed into a secondary short-path molecular distillation apparatus. The distillation vacuum is controlled at 600Pa, the evaporation temperature at 135°C, the scraper rotation speed at 320r / min, and the feed flow rate at 12L / h. The liquid film shearing effect is enhanced to amplify the difference in free path of isomer molecules, thereby directionally removing monoethyltoluene diamine impurities and separating the medium and light impurity fraction and the secondary purified liquid. Step S4, Three-stage molecular distillation purification: The secondary purified liquid is preheated to 120°C and fed into a three-stage short-path molecular distillation device. The distillation vacuum is controlled at 300Pa, the evaporation temperature at 165°C, the scraper rotation speed at 360r / min, and the feed flow rate at 10L / h. The heavy component residue and the high-purity diethyltoluene diamine product fraction are separated. Step S5, Finished product cooling and packaging: The finished product fraction obtained from the three-stage distillation is cooled to 30°C by a low-temperature cooler, and sealed and packaged under nitrogen protection in a closed-loop oxygen control process to obtain high-purity diethyltoluene diamine finished product.

[0021] The filtration precision in step S1 is 0.5 μm; the preparation process of crude diethyltoluenediamine in step S1 is as follows: using m-toluenediamine as the main raw material and high-purity ethylene as the alkylating agent, a customized catalyst is used; the molar ratio of m-toluenediamine to ethylene is controlled at 1:2.05, and the catalyst feed mass is 2.5% of the m-toluenediamine feed mass; under nitrogen replacement protection and an oxygen-free environment, the reaction temperature is controlled at 120℃ and the reaction pressure at 1.0 MPa, and a continuous catalytic alkylation reaction is carried out, with a reaction residence time of 2.5 h; after the alkylation reaction is completed, the mixture is sent to a flash tank for flash evaporation at atmospheric pressure and constant temperature of 80℃ to quickly remove unreacted ethylene, trace amounts of low-carbon hydrocarbons and other light gaseous components, to obtain crude DETDA with an initial purity of 90%.

[0022] The customized catalyst is a mixture of lanthanum oxide and ZSM-5 molecular sieve at a mass ratio of 1:100. The first-stage short-range molecular distillation equipment in step S2 employs a large-gap, low-shear scraped film structure, coupled with an oxygen partial pressure adaptive nitrogen protection mode. The second-stage short-range molecular distillation equipment in step S3 employs a small-gap, high-shear variable-gap scraped film structure, dynamically and adaptively adjusting the nitrogen micro-positive pressure to 0.022 MPa. The third-stage short-range molecular distillation equipment in step S4 employs a steady-state equal-gap homogeneous scraped film structure, dynamically and adaptively increasing the nitrogen micro-positive pressure to 0.025 MPa. All three stages of the short-range molecular distillation equipment are scraped film type short-range molecular distillation devices, with a 20 mm distance between the evaporation surface and the condensation surface, and the condensation temperature is controlled at 25°C. Example

[0023] A process for producing diethyltoluenediamine using molecular distillation includes the following steps: Step S1, Crude Product Pretreatment: The crude diethyltoluenediamine obtained by the alkylation reaction of toluenediamine is filtered through a precision filter to remove solid catalyst residue and mechanical impurities, resulting in a clear crude liquid; Step S2, primary molecular distillation to remove light components: The clarified crude liquid is preheated to 83°C and fed into a primary short-path molecular distillation apparatus. The distillation vacuum is controlled at 820 Pa, the evaporation temperature at 113°C, the scraper rotation speed at 290 r / min, the feed flow rate at 16 L / h, and the nitrogen micro-positive pressure at 0.020 MPa. Light component fraction and primary purified liquid are obtained. The light component fraction is unreacted toluene diamine and low molecular weight hydrocarbon impurities. Step S3, Secondary Molecular Distillation for Impurity Removal: The primary purified liquid is preheated to 103°C and fed into a secondary short-path molecular distillation apparatus. The distillation vacuum is controlled at 620Pa, the evaporation temperature at 137°C, the scraper rotation speed at 330r / min, and the feed flow rate at 13L / h. The liquid film shearing effect is enhanced to amplify the difference in free path of isomer molecules, and the monoethyltoluene diamine impurity is directionally removed, resulting in the separation of the medium and light impurity fraction and the secondary purified liquid. Step S4, Three-stage molecular distillation purification: The secondary purified liquid is preheated to 123°C and fed into a three-stage short-path molecular distillation device. The distillation vacuum is controlled at 320Pa, the evaporation temperature at 167°C, the scraper rotation speed at 370r / min, and the feed flow rate at 12L / h. The heavy component residue and the high-purity diethyltoluene diamine product fraction are separated. Step S5, Finished product cooling and packaging: The finished product fraction obtained from the three-stage distillation is cooled to 33°C by a low-temperature cooler. The entire process is carried out under closed-loop oxygen control and sealed under nitrogen protection to obtain high-purity diethyltoluene diamine finished product.

[0024] The filtration precision in step S1 is 0.5 μm; the preparation process of crude diethyltoluenediamine in step S1 is as follows: using m-toluenediamine as the main raw material and high-purity ethylene as the alkylating agent, a custom catalyst is used; the molar ratio of m-toluenediamine to ethylene is controlled at 1:2.08, and the catalyst feed mass is 3% of the m-toluenediamine feed mass; under nitrogen replacement protection and an oxygen-free environment, the reaction temperature is controlled at 130℃ and the reaction pressure at 2.5 MPa, and a continuous catalytic alkylation reaction is carried out, with a reaction residence time of 3.0 h; after the alkylation reaction, the mixture is sent to a flash evaporator for flash evaporation at atmospheric pressure and constant temperature of 80℃ to quickly remove unreacted ethylene, trace amounts of low-carbon hydrocarbons and other gaseous light components, to obtain crude DETDA with an initial purity of 90.5%; the custom catalyst is a mixture of lanthanum oxide and ZSM-5 molecular sieve in a mass ratio of 1.5:100.

[0025] The first-stage short-range molecular distillation device described in step S2 adopts a large-gap, low-shear scraped film structure, coupled with an oxygen partial pressure adaptive nitrogen protection mode; the second-stage short-range molecular distillation device described in step S3 adopts a small-gap, high-shear variable-gap scraped film structure, dynamically and adaptively adjusting the nitrogen micro-positive pressure to 0.022 MPa; the third-stage short-range molecular distillation device described in step S4 adopts a steady-state equal-gap homogeneous scraped film structure, dynamically and adaptively increasing the nitrogen micro-positive pressure to 0.025 MPa; the first-stage, second-stage, and third-stage short-range molecular distillation devices are all scraped film type short-range molecular distillation devices, with a distance of 23 mm between the evaporation surface and the condensation surface, and the condensation temperature controlled at 27℃. Example

[0026] A process for producing diethyltoluenediamine using molecular distillation includes the following steps: Step S1, Crude Product Pretreatment: The crude diethyltoluenediamine obtained by the alkylation reaction of toluenediamine is filtered through a precision filter to remove solid catalyst residue and mechanical impurities, resulting in a clear crude liquid; Step S2, primary molecular distillation to remove light components: The clarified crude liquid is preheated to 85°C and fed into a primary short-path molecular distillation apparatus. The distillation vacuum is controlled at 850 Pa, the evaporation temperature at 115°C, the scraper rotation speed at 300 r / min, the feed flow rate at 17 L / h, and the nitrogen micro-positive pressure at 0.020 MPa. Light component fraction and primary purified liquid are obtained. The light component fraction is unreacted toluene diamine and low molecular weight hydrocarbon impurities. Step S3, Secondary Molecular Distillation for Impurity Removal: The primary purified liquid is preheated to 105°C and fed into a secondary short-path molecular distillation apparatus. The distillation vacuum is controlled at 650Pa, the evaporation temperature at 140°C, the scraper rotation speed at 340r / min, and the feed flow rate at 14L / h. The liquid film shearing effect is enhanced to amplify the difference in free path of isomer molecules, thereby directionally removing monoethyltoluene diamine impurities and separating the medium and light impurity fraction and the secondary purified liquid. Step S4, Three-stage molecular distillation purification: The secondary purified liquid is preheated to 125°C and fed into a three-stage short-path molecular distillation device. The distillation vacuum is controlled at 350Pa, the evaporation temperature at 170°C, the scraper rotation speed at 380r / min, and the feed flow rate at 12L / h. The heavy component residue and the high-purity diethyltoluene diamine product fraction are separated. Step S5, Finished product cooling and packaging: The finished product fraction obtained from the three-stage distillation is cooled to 35°C by a low-temperature cooler, and sealed and packaged under nitrogen protection in a closed-loop oxygen control process to obtain high-purity diethyltoluene diamine finished product.

[0027] The filtration precision in step S1 is 0.5 μm; the preparation process of crude diethyltoluenediamine in step S1 is as follows: using m-toluenediamine as the main raw material and high-purity ethylene as the alkylating agent, a customized catalyst is used; the molar ratio of m-toluenediamine to ethylene is controlled at 1:2.12, and the catalyst feed mass is 3.3% of the m-toluenediamine feed mass; under nitrogen replacement protection and an oxygen-free environment, the reaction temperature is controlled at 140℃ and the reaction pressure at 3.0 MPa, and a continuous catalytic alkylation reaction is carried out, with a reaction residence time of 3.3 h; after the alkylation reaction is completed, the mixture is sent to a flash tank for flash evaporation at atmospheric pressure and constant temperature of 80℃ to quickly remove unreacted ethylene, trace amounts of low-carbon hydrocarbons and other gaseous light components, to obtain crude DETDA with an initial purity of 91%.

[0028] The customized catalyst is a mixture of lanthanum oxide and ZSM-5 molecular sieve at a mass ratio of 2:100. The first-stage short-range molecular distillation equipment in step S2 employs a large-gap, low-shear scraped film structure, coupled with an oxygen partial pressure adaptive nitrogen protection mode. The second-stage short-range molecular distillation equipment in step S3 employs a small-gap, high-shear variable-gap scraped film structure, dynamically and adaptively adjusting the nitrogen micro-positive pressure to 0.022 MPa. The third-stage short-range molecular distillation equipment in step S4 employs a steady-state equal-gap homogeneous scraped film structure, dynamically and adaptively increasing the nitrogen micro-positive pressure to 0.025 MPa. All three stages of the short-range molecular distillation equipment are scraped film type short-range molecular distillation devices, with a 25 mm distance between the evaporation surface and the condensation surface, and the condensation temperature controlled at 30°C. Example

[0029] A process for producing diethyltoluenediamine using molecular distillation includes the following steps: Step S1, Crude Product Pretreatment: The crude diethyltoluenediamine obtained by the alkylation reaction of toluenediamine is filtered through a precision filter to remove solid catalyst residue and mechanical impurities, resulting in a clear crude liquid; Step S2, primary molecular distillation to remove light components: The clarified crude liquid is preheated to 88°C and fed into a primary short-path molecular distillation apparatus. The distillation vacuum is controlled at 890Pa, the evaporation temperature at 118°C, the scraper rotation speed at 310r / min, the feed flow rate at 19L / h, and the nitrogen micro-positive pressure at 0.020MPa. Light component fraction and primary purified liquid are obtained. The light component fraction is unreacted toluene diamine and low molecular weight hydrocarbon impurities. Step S3, Secondary Molecular Distillation for Impurity Removal: The primary purified liquid is preheated to 108°C and fed into a secondary short-path molecular distillation apparatus. The distillation vacuum is controlled at 690Pa, the evaporation temperature at 143°C, the scraper rotation speed at 355r / min, and the feed flow rate at 15L / h. The liquid film shearing effect is enhanced to amplify the difference in free path of isomer molecules, thereby directionally removing monoethyltoluene diamine impurities and separating the medium and light impurity fraction and the secondary purified liquid. Step S4, Three-stage molecular distillation purification: The secondary purified liquid is preheated to 128°C and fed into a three-stage short-path molecular distillation apparatus. The distillation vacuum is controlled at 380Pa, the evaporation temperature at 173°C, the scraper rotation speed at 390r / min, and the feed flow rate at 13L / h. The heavy component residue and the high-purity diethyltoluene diamine product fraction are separated. Step S5, Finished product cooling and packaging: The finished product fraction obtained from the three-stage distillation is cooled to 38°C by a low-temperature cooler, and sealed and packaged under nitrogen protection in a closed-loop oxygen control process to obtain high-purity diethyltoluene diamine finished product.

[0030] The filtration precision in step S1 is 0.5 μm; the preparation process of crude diethyltoluenediamine in step S1 is as follows: using m-toluenediamine as the main raw material and high-purity ethylene as the alkylating agent, a customized catalyst is used; the molar ratio of m-toluenediamine to ethylene is controlled at 1:2.18, and the catalyst feed mass is 3.8% of the m-toluenediamine feed mass; under nitrogen replacement protection and an oxygen-free environment, the reaction temperature is controlled at 155℃ and the reaction pressure at 5.0 MPa, and a continuous catalytic alkylation reaction is carried out with a reaction residence time of 3.8 h; after the alkylation reaction is completed, the mixture is sent to a flash tank for flash evaporation at atmospheric pressure and constant temperature of 80℃ to quickly remove unreacted ethylene, trace amounts of low-carbon hydrocarbons and other gaseous light components, to obtain crude DETDA with an initial purity of 91.5%.

[0031] The customized catalyst is a mixture of lanthanum oxide and ZSM-5 molecular sieve at a mass ratio of 2.5:100. The first-stage short-range molecular distillation equipment in step S2 employs a large-gap, low-shear scraped film structure, coupled with an oxygen partial pressure adaptive nitrogen protection mode. The second-stage short-range molecular distillation equipment in step S3 employs a small-gap, high-shear variable-gap scraped film structure, dynamically and adaptively adjusting the nitrogen micro-positive pressure to 0.022 MPa. The third-stage short-range molecular distillation equipment in step S4 employs a steady-state equal-gap homogeneous scraped film structure, dynamically and adaptively increasing the nitrogen micro-positive pressure to 0.025 MPa. All three stages of the short-range molecular distillation equipment are scraped film type short-range molecular distillation devices, with a 28 mm distance between the evaporation surface and the condensation surface, and the condensation temperature controlled at 33°C. Example

[0032] A process for producing diethyltoluenediamine using molecular distillation includes the following steps: Step S1, Crude Product Pretreatment: The crude diethyltoluenediamine obtained by the alkylation reaction of toluenediamine is filtered through a precision filter to remove solid catalyst residue and mechanical impurities, resulting in a clear crude liquid; Step S2, primary molecular distillation to remove light components: The clarified crude liquid is preheated to 90°C and fed into a primary short-path molecular distillation apparatus. The distillation vacuum is controlled at 900Pa, the evaporation temperature at 120°C, the scraper rotation speed at 320r / min, the feed flow rate at 20L / h, and the nitrogen micro-positive pressure at 0.020MPa. Light component fraction and primary purified liquid are obtained. The light component fraction is unreacted toluene diamine and low molecular weight hydrocarbon impurities. Step S3, Secondary Molecular Distillation for Impurity Removal: The primary purified liquid is preheated to 110°C and fed into a secondary short-path molecular distillation apparatus. The distillation vacuum is controlled at 700Pa, the evaporation temperature at 145°C, the scraper rotation speed at 360r / min, and the feed flow rate at 16L / h. The liquid film shearing effect is enhanced to amplify the difference in free path of isomer molecules, thereby directionally removing monoethyltoluene diamine impurities and separating the medium and light impurity fraction and the secondary purified liquid. Step S4, Three-stage molecular distillation purification: The secondary purified liquid is preheated to 130°C and fed into a three-stage short-path molecular distillation device. The distillation vacuum is controlled at 400Pa, the evaporation temperature at 175°C, the scraper rotation speed at 400r / min, and the feed flow rate at 14L / h. The heavy component residue and the high-purity diethyltoluene diamine product fraction are separated. Step S5, Finished product cooling and packaging: The finished product fraction obtained from the three-stage distillation is cooled to 40°C using a cryogenic cooler. The entire process is carried out under closed-loop oxygen control and sealed under nitrogen protection to obtain high-purity diethyltoluene diamine.

[0033] The filtration precision in step S1 is 0.5 μm; the preparation process of crude diethyltoluenediamine in step S1 is as follows: using m-toluenediamine as the main raw material and high-purity ethylene as the alkylating agent, a custom catalyst is used; the molar ratio of m-toluenediamine to ethylene is controlled at 1:2.20, and the catalyst feed mass is 4.0% of the m-toluenediamine feed mass; under nitrogen replacement protection and an oxygen-free environment, the reaction temperature is controlled at 160℃ and the reaction pressure at 6.0 MPa, and a continuous catalytic alkylation reaction is carried out, with a reaction residence time of 4.0 h; after the alkylation reaction, the mixture is sent to a flash evaporator for flash evaporation at atmospheric pressure and constant temperature of 80℃ to quickly remove unreacted ethylene, trace amounts of low-carbon hydrocarbons and other gaseous light components, to obtain crude DETDA with an initial purity of 92%; the custom catalyst is a mixture of lanthanum oxide and ZSM-5 molecular sieve in a mass ratio of 3:100.

[0034] The first-stage short-range molecular distillation device described in step S2 adopts a large-gap, low-shear scraped film structure, coupled with an oxygen partial pressure adaptive nitrogen protection mode; the second-stage short-range molecular distillation device described in step S3 adopts a small-gap, high-shear variable-gap scraped film structure, dynamically and adaptively adjusting the nitrogen micro-positive pressure to 0.022 MPa; the third-stage short-range molecular distillation device described in step S4 adopts a steady-state equal-gap homogeneous scraped film structure, dynamically and adaptively increasing the nitrogen micro-positive pressure to 0.025 MPa; the first-stage, second-stage, and third-stage short-range molecular distillation devices are all scraped film type short-range molecular distillation devices, with a distance of 30 mm between the evaporation surface and the condensation surface, and the condensation temperature controlled at 35℃.

[0035] Comparative Example 1 Using the existing mainstream industrial process, crude DETDA from the same batch was pretreated and then fed into a vacuum distillation column. The vacuum degree was controlled at 500 Pa, the distillation temperature at 220℃, and the distillation was carried out at a constant temperature for 4 hours. After separation and purification, the product was cooled and packaged to obtain the finished product of the traditional process.

[0036] To further illustrate the beneficial technical effects of the molecular distillation process for producing diethyltoluene diamine involved in the various embodiments of the present invention, relevant performance tests were conducted on the diethyltoluene diamine produced in each example. The test methods are as follows: (1) Product purity test: An Agilent 7890A gas chromatograph with an FID detector and a DB-5 capillary column was used. The column temperature was programmed as follows: initial temperature 100℃, hold for 2 min, increase to 280℃ at 10℃ / min, hold for 10 min, injection volume 0.2 μL, and purity was calculated by external standard method.

[0037] (2) Product yield calculation: Yield = (pure product mass after refining × pure product purity) / (crude product mass × crude product initial purity) × 100%.

[0038] (3) Energy consumption detection: According to GB / T 2589-2020 "General Rules for Calculation of Comprehensive Energy Consumption", the total electrical and thermal energy consumption of a unit mass of finished product is statistically analyzed and the comprehensive energy consumption is calculated.

[0039] Table 1 Performance test data of diethyltoluenediamine

[0040] As shown in Table 1, compared with Comparative Example 1, which uses traditional vacuum distillation, the diethyltoluene diamine prepared by the molecular distillation process of this invention has significantly higher purity and overall yield, and significantly lower overall energy consumption. Furthermore, with the gradual optimization of process parameters in Examples 1 to 5, the product purity increased from 99.21% to 99.62%, the overall yield increased from 95.36% to 96.65%, and the overall energy consumption per unit product gradually decreased from 1862 kJ / kg to 1741 kJ / kg. All performance characteristics show a continuous optimization trend, highlighting the advantages of the process.

[0041] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A process for producing diethyltoluenediamine using molecular distillation, characterized in that, Includes the following steps: Step S1, Crude Product Pretreatment: The crude diethyltoluenediamine obtained by the alkylation reaction of toluenediamine is filtered through a precision filter to remove solid catalyst residue and mechanical impurities, resulting in a clear crude liquid; Step S2, primary molecular distillation to remove light components: The clarified crude liquid is preheated to 80-90℃ and fed into a primary short-path molecular distillation apparatus. The distillation vacuum is controlled at 800-900Pa, the evaporation temperature at 110-120℃, the scraper rotation speed at 280-320r / min, the feed flow rate at 15-20L / h, and the nitrogen micro-positive pressure at 0.020MPa. Light component fractions and primary purified liquid are obtained. The light component fractions are unreacted toluene diamine and low molecular weight hydrocarbon impurities. Step S3, Secondary Molecular Distillation for Impurity Removal: The primary purified liquid is preheated to 100-110℃ and fed into a secondary short-path molecular distillation apparatus. The distillation vacuum is controlled at 600-700Pa, the evaporation temperature at 135-145℃, the scraper rotation speed at 320-360r / min, and the feed flow rate at 12-16L / h. The liquid film shearing effect is enhanced to amplify the difference in free path of isomer molecules, and the monoethyltoluene diamine impurity is directionally removed, resulting in the separation of the medium and light impurity fraction and the secondary purified liquid. Step S4, Three-stage molecular distillation purification: The secondary purified liquid is preheated to 120-130℃ and fed into a three-stage short-path molecular distillation device. The distillation vacuum is controlled at 300-400Pa, the evaporation temperature at 165-175℃, the scraper rotation speed at 360-400r / min, and the feed flow rate at 10-14L / h. The heavy component residue and the high-purity diethyltoluene diamine product fraction are separated. Step S5, Finished product cooling and packaging: The finished product fraction obtained from the three-stage distillation is cooled to 30-40℃ by a low-temperature cooler, and sealed and packaged under nitrogen protection in a closed-loop oxygen control process to obtain high-purity diethyltoluene diamine finished product.

2. The process for producing diethyltoluenediamine by molecular distillation according to claim 1, characterized in that, The filtration accuracy in step S1 is 0.5 μm.

3. The process for producing diethyltoluenediamine by molecular distillation according to claim 1, characterized in that, The preparation process of crude diethyltoluenediamine in step S1 is as follows: using m-toluenediamine as the main raw material and high-purity ethylene as the alkylating agent, a customized catalyst is used; the molar ratio of m-toluenediamine to ethylene is controlled at 1:(2.05~2.20), and the catalyst feed mass is 2.5%~4.0% of the m-toluenediamine feed mass; under nitrogen replacement protection and an oxygen-free environment, the reaction temperature is controlled at 120~160℃ and the reaction pressure at 1.0~6.0MPa, and a continuous catalytic alkylation reaction is carried out, with a reaction residence time of 2.5~4.0h; after the alkylation reaction is completed, the mixture is sent to a flash tank for flash evaporation at atmospheric pressure and constant temperature of 80℃ to quickly remove unreacted ethylene, trace amounts of low-carbon hydrocarbons and other gaseous light components, to obtain crude DETDA with an initial purity of 90%~92%.

4. The process for producing diethyltoluenediamine by molecular distillation according to claim 3, characterized in that, The customized catalyst is a mixture of lanthanum oxide and ZSM-5 molecular sieve in a mass ratio of (1-3):

100.

5. The process for producing diethyltoluenediamine by molecular distillation according to claim 1, characterized in that, The first-stage short-range molecular distillation equipment described in step S2 adopts a large-gap, low-shear scraping film structure, combined with an oxygen partial pressure adaptive nitrogen protection mode.

6. The process for producing diethyltoluenediamine by molecular distillation according to claim 1, characterized in that, The two-stage short-range molecular distillation equipment described in step S3 adopts a small-gap, high-shear variable-gap scraping film structure, and dynamically and adaptively adjusts the nitrogen micro-positive pressure to 0.022 MPa.

7. The process for producing diethyltoluenediamine by molecular distillation according to claim 1, characterized in that, The three-stage short-range molecular distillation equipment described in step S4 adopts a steady-state equal-gap homogeneous scraping film structure and dynamically and adaptively adjusts the nitrogen micro-positive pressure to 0.025MPa.

8. The process for producing diethyltoluenediamine by molecular distillation according to claim 1, characterized in that, The first-stage, second-stage, and third-stage short-range molecular distillation equipment are all scraped-film type short-range molecular distillation devices, with a distance of 20-30 mm between the evaporation surface and the condensation surface, and the condensation temperature is controlled at 25-35℃.

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