A continuous process and system for the production of a lactam monomer

Abstract

A continuous production method and system of lactam monomer, raw materials containing amino acid and auxiliary agent are introduced into a reaction rectifying tower from the middle part, intramolecular dehydration and cyclization reaction of amino acid occurs to generate lactam monomer, the top discharge of the reaction rectifying tower is introduced into a liquid-liquid two-phase separator through a condenser, the separated auxiliary agent returns to the reaction rectifying tower in reflux, and the separated water is discharged; a reboiler is arranged at the bottom of the reaction rectifying tower, the tower cauldron discharge is introduced into an auxiliary agent recovery tower for separation, the obtained auxiliary agent returns to the reaction rectifying tower, and the lactam monomer product is obtained; wherein the auxiliary agent is C5-C8 alcohol. The method and system provided by the application improve the reaction conversion rate and selectivity of amino acid in preparation of lactam monomer, and reduce the energy consumption of the device.

Description

TECHNICAL FIELD

[0001] The present application relates to a reaction method and system in the field of organic synthesis, in particular, to a method and system for preparing lactam monomers by intramolecular dehydration and cyclization of amino acid. BACKGROUND

[0002] Amino acid is an organic compound containing basic amino and acidic carboxyl, which is formed by replacing the hydrogen atom on the carbon atom of carboxylic acid with amino. The amino acid obtained from the hydrolysis of biological proteins is α-amino acid, and since the acidic group and basic group coexist in the amino acid molecule and can interact to form internal salt, the amino acid usually exists in the form of dipole ion. The amino acid molecule can be dehydrated intermolecularly to generate polypeptides, and for some amino acids containing multiple amino groups or carboxyl groups in the molecule, such as lysine, glutamic acid, glutamine, arginine, ornithine, etc., intramolecular dehydration and cyclization can also be carried out under specific conditions to generate some specific cyclic compounds, and have incomparable reaction advantages over conventional organic synthesis.

[0003] Aminocaproamide is an organic monomer with very wide application, which can be used as food additive, prepared caprolactam (raw material for nylon-6 and nylon-12) and an important pharmaceutical intermediate. The current aminocaproamide monomer on the market is mainly prepared from cyclohexene as raw material through addition, amination and Beckmann rearrangement, which has long reaction route, complex process and uses many toxic and harmful substances, seriously limiting its large-scale production and application. The latest aminocaproamide route is to prepare from lysine fermented by biomass. CN111116472A discloses a method for preparing aminocaproamide from lysine as raw material by esterification first and then dehydration and cyclization, which needs a large amount of strong acid and strong base, and produces a large amount of inorganic salt, and the yield of aminocaproamide is low, only about 40%. CN102093292A discloses a method for synthesizing aminocaproamide, which first undergoes nucleophilic substitution reaction of α-halo caprolactam with benzylamine under certain conditions, and then generates target aminocaproamide by hydrogenolysis of benzyl. The above synthesis process needs two different reactions, and the process selectivity is low, which affects the product yield. One-step method refers to a method for directly synthesizing aminocaproamide from lysine, which is first reported in the literature [Tetrahedron Letters, 1980, 21, 2443-2446], lysine is dehydrated and cyclized in the presence of silica gel or alumina in toluene to generate aminocaproamide, and the product yield is 37%-71%. JP2012162463A reports a method for directly and efficiently producing aminocaproamide from lysine, the raw material lysine can be obtained from enzyme reaction of biomass such as molasses, the reaction temperature is preferably 200-350℃; the reaction is carried out in an inert gas atmosphere, and the reaction pressure is preferably 3-10 MPa. CN102718711A discloses a preparation method of aminocaproamide hydrochloride, which uses D-lysine monohydrochloride or D-lysine as raw material, sodium hydroxide as base and n-hexanol as solvent, and reacts under reflux condition at 155-157℃ to obtain aminocaproamide product.

[0004] The above patents realize the possibility of synthesizing aminocaproamide from biomass lysine. However, due to the characteristics of the reaction itself, that is, the competitive relationship between intramolecular dehydration and intermolecular dehydration, the yield of target product aminocaproamide is usually not high, and there are many and miscellaneous by-products, which reduces the effective utilization rate of raw materials and has great influence on the subsequent product separation. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a method and system for continuous production of aminocaproamide monomer from amino acid, which can reduce the energy consumption of the device and improve the reaction selectivity.

[0006] In a first aspect, the present application provides a continuous production method of lactam monomer, in which a raw material containing amino acid and an auxiliary agent are fed into a middle part of a reactive rectification tower, intramolecular dehydration and cyclization of the amino acid occur to generate lactam monomer, the top discharge of the reactive rectification tower is fed into a liquid-liquid two-phase separator through a condenser, the separated auxiliary agent is returned to the reactive rectification tower as reflux, and the separated water is discharged; a reboiler is arranged at the bottom of the reactive rectification tower, the tower kettle discharge is fed into an auxiliary agent recovery tower for fractionation, the obtained auxiliary agent is returned to the reactive rectification tower, and the lactam monomer product is collected; wherein the auxiliary agent is a C5-C8 alcohol.

[0007] In a second aspect, the present application provides a continuous production system of lactam monomer, which comprises a reactive rectification tower and an auxiliary agent recovery tower, the middle part of the reactive rectification tower is provided with a raw material and auxiliary agent inlet; a vapor phase outlet at the top of the reactive rectification tower is connected to a liquid-liquid two-phase separator through a tower top condenser, an alcohol-water phase outlet of the liquid-liquid two-phase separator is connected to a tower top reflux inlet, a reboiler and a tower kettle material outlet are arranged at the bottom of the reactive rectification tower; the tower kettle material outlet is connected to an inlet of the auxiliary agent recovery tower, a recovered auxiliary agent outlet of the auxiliary agent recovery tower is connected to the tower top reflux inlet of the reactive rectification tower, and the auxiliary agent recovery tower is further provided with a product outlet.

[0008] The continuous production method and system of lactam monomer provided by the present application have the following beneficial effects:

[0009] Compared with the prior art, the dehydration and cyclization reaction of the amino acid in the continuous production method of lactam monomer of the present application separates water and the auxiliary agent simultaneously, removes the raw material and the reaction generated water from the reaction system in time, and can improve the conversion rate and selectivity of the amino acid reaction; and simultaneously reduces energy consumption.

[0010] The method and system provided by the present application complete the reaction and dehydration process in the same equipment, the equipment structure is compact, the space utilization rate is high, and the equipment investment is significantly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 The present application provides a flow diagram of the continuous production method of lactam monomer.

[0012] Figure 2 The present application provides a structure diagram of an embodiment of the liquid-liquid two-phase separator.

[0013] Among them:

[0014] I-rectification section II-reaction section

[0015] 1-amino acid aqueous solution feed 2-reactive rectification tower 3-vapor phase at the top of the tower

[0016] 4-condenser 5-liquid-liquid two-phase separator 6-auxiliary agent reflux

[0017] 7 - aqueous phase 8 - reboiler 9 - column bottom discharge

[0018] 10 - auxiliary agent recovery column 11 - recovered auxiliary agent 12 - lactam monomer product

[0019] 13 - two-phase separator inlet 14 - auxiliary agent outlet 15 - aqueous phase outlet

[0020] 501 - fiber filament contactor 502 - flow dividing baffle 503 - water package DETAILED DESCRIPTION

[0021] The following detailed description of the application is provided.

[0022] In the present application, the so-called "top", "middle", "bottom" are based on the relative position of the container. Among them, the "bottom" refers to the position of 0-10% from the bottom to the top of the container, the "middle" refers to the position of 40-60% from the bottom to the top of the container, and the "top" refers to the position of 90-100% from the bottom to the top of the container.

[0023] The present application provides a continuous production method of lactam monomer, the raw material containing amino acid and auxiliary agent are fed into the reaction rectifying column from the middle, intramolecular dehydration and cyclization reaction of amino acid to generate lactam monomer, the top discharge of the reaction rectifying column enters the liquid-liquid two-phase separator through the condenser, the separated auxiliary agent returns to the reaction rectifying column, and the separated water is discharged; The bottom of the reaction rectifying column is provided with a reboiler, the column bottom discharge enters the auxiliary agent recovery column for fractionation, the obtained auxiliary agent returns to the reaction rectifying column, and the lactam monomer product is recovered; wherein the auxiliary agent is C5-C8 alcohol.

[0024] In the present application, the raw material containing amino acid is selected from one or more of lysine, lysine salt, and lysine aqueous solution obtained by biological fermentation;

[0025] Preferably, the raw material containing amino acid is 1wt%-60wt% lysine aqueous solution.

[0026] In the present application, the molar ratio of auxiliary agent to amino acid in the reaction feed is 1-30:1, preferably 2-20:1.

[0027] In the present application, the reaction rectifying column feed position below is the reaction section, and the feed position above is the rectification section; wherein the reaction rectifying column reaction section temperature is 140-300℃, preferably 150-250℃; The top temperature is 80-200℃, preferably 100-180℃; The pressure of the reaction rectifying column is the bubble point pressure of the auxiliary agent or the azeotrope formed by the auxiliary agent and water at the reaction temperature.

[0028] In the present application, the residence time of the raw material containing amino acid in the reaction section is 0.5-10h, preferably 1.0-6.0h.

[0029] In the present application, the reaction rectification column is filled with trays or packing, and the number of theoretical trays is 5-30.

[0030] Preferably, the liquid-liquid two-phase separator comprises a tank body and a flow separation baffle, the flow separation baffle separates the internal space of the tank body into two parts which are in communication with each other in the upper part and separated in the middle part, one end of the tank body is provided with a two-phase separator section inlet, the other end is provided with an auxiliary agent outlet, and the bottom of the tank body is provided with a water package and an aqueous phase outlet.

[0031] Preferably, the liquid-liquid two-phase separator inlet is provided with a liquid droplet coalescence strengthening structure filled with fiber filaments or surface coalescence packing. The liquid droplet coalescence strengthening structure can coalesce liquid droplets to promote liquid-liquid two-phase separation.

[0032] In the present application, the auxiliary agent is C5-C8 alcohol, and the auxiliary agent is recovered in an auxiliary agent recovery tower, and the operating conditions of the auxiliary agent recovery tower are as follows: the operating pressure is 1-50kPa (absolute pressure), the column bottom temperature is 60-150℃, and the reflux ratio is 1.0-15.0.

[0033] When the auxiliary agent is C5-C6 alcohol, the boiling point of C5-C6 alcohol is lower than that of the lactam monomer, the overhead product of the auxiliary agent recovery tower is C5-C6 alcohol, and the bottom product is the lactam monomer product; when the auxiliary agent is C7-C8 alcohol, the boiling point of C7-C8 alcohol is higher than that of the lactam monomer, the overhead product of the auxiliary agent recovery tower is the lactam monomer product, and the bottom product is C7-C8 alcohol. The obtained auxiliary agents are all returned to the reaction rectification tower.

[0034] In the second aspect, the present application provides a continuous production system of lactam monomer, which comprises a reaction rectification tower and an auxiliary agent recovery tower, the middle part of the reaction rectification tower is provided with a raw material and auxiliary agent inlet; the vapor phase outlet at the top of the reaction rectification tower is connected with a liquid-liquid two-phase separator through a column top condenser, the alcohol and water phase outlet of the liquid-liquid two-phase separator is connected with the column top reflux inlet, and the bottom part of the reaction rectification tower is provided with a reboiler and a column bottom material outlet; the column bottom material outlet of the reaction rectification tower is connected with the inlet of the auxiliary agent recovery tower, the recovery auxiliary agent outlet of the auxiliary agent recovery tower is connected with the auxiliary agent inlet of the reaction rectification tower, and the auxiliary agent recovery tower is also provided with a product outlet.

[0035] Preferably, the liquid-liquid two-phase separator comprises a tank body and a flow separation baffle, the flow separation baffle separates the internal space of the tank body into two parts which are in communication with each other in the upper part and separated in the middle part, the inlet is connected with the upper part of the tank body through a cylinder which is internally filled with packing, the other end of the upper part of the tank body is provided with an auxiliary agent outlet, and the bottom of the tank body is provided with a water package and an aqueous phase outlet; the inlet of the liquid-liquid two-phase separator is provided with a liquid droplet coalescence strengthening structure filled with fiber filaments or surface coalescence packing.

[0036] In the method provided by this invention, the amino acid molecule contains multiple amino or carboxyl groups, and the intramolecular dehydration cyclization refers to the reaction involving the amino and carboxyl groups within the amino acid molecule; the amino acid molecule is preferably lysine, selected from one or more of lysine, lysine salt, and lysine aqueous solution obtained by bio-fermentation. Other amino acids containing multiple amino or carboxyl groups are also applicable to this method, such as glutamic acid, arginine, and other amino acid molecules with similar structures.

[0037] The reactive distillation column includes an upper rectification section and a lower reaction section. Preferably, the rectification section is filled with packing material, and the reaction section is equipped with a tray structure.

[0038] The bottom of the reactive distillation column yields a solution rich in lactam monomers, while the top phase undergoes liquid-liquid phase separation and is collected as the aqueous phase. The additives are then completely refluxed. The bottom solution rich in lactam monomers enters a subsequent separation unit for product separation and purification, as well as for the reuse of the additives.

[0039] The following detailed description, with reference to the accompanying drawings, uses lysine aqueous solution as a raw material and n-hexanol as an auxiliary agent to illustrate specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0040] Appendix Figure 1 This is a schematic diagram of a continuous production process for lactam monomers. (See attached diagram.) Figure 1 As shown, the reactive distillation column 2 consists of an upper rectification section I and a lower reaction section II. Lysine aqueous solution feed 1 is added from the top of reaction section II and flows downwards through reaction section II along with the reflux liquid from rectification section I. The temperature of the reaction section is 140-300℃. In the presence of hexanol, lysine undergoes a dehydration reaction to produce aminocaprolactam. A reboiler 8 is installed at the bottom of the reactive distillation column to provide rising vapor. Because hexanol and water form a low-boiling-point azeotrope, and the reaction pressure is the bubble point pressure of this azeotrope at the reaction section temperature, the rising vapor is the azeotrope formed by hexanol and water. The vapor-phase azeotrope from the top of the column 3 is condensed into a completely liquid phase by the condenser 4 and then enters the liquid-liquid two-phase separator 5 for phase separation. After the liquid-liquid phase separation is enhanced by droplet aggregation and strengthening structures, such as fiber contactors 501, the hexanol phase saturated with dissolved water is collected from the top of the liquid-liquid two-phase separator as the top reflux 6, and the aqueous phase 7 containing a certain amount of hexanol is collected from the water tank 503 at the bottom of the liquid-liquid two-phase separator and discharged. The bottom product 9 from the bottom of the reactive distillation column is a hexanol solution of aminocaprolactam, which goes to the additive recovery column 10. The recovered additive 11 and the target product of aminocaprolactam 12 are separated in the additive recovery column. The recovered additive, recycled hexanol 11, is returned to the reactive distillation column 2 from the top.

[0041] Figure 2A schematic diagram of the structure of one embodiment of the liquid-liquid two-phase separator. As shown in the accompanying Figure 2 The liquid-liquid two-phase separator includes a tank body and a flow distribution baffle 502, which separates the internal space of the tank body into two parts that are in communication with each other and are separated in the middle. The two-phase separator inlet 13 is provided with a liquid droplet coalescence strengthening structure, and is filled with a fiber filament contactor 501. The other end of the upper part of the tank body is provided with an auxiliary agent outlet 14, and the bottom of the tank body is provided with a water bag 503 and a water phase outlet 15.

[0042] The application will be further described below through examples. The application is not limited in any way by the examples.

[0043] The lysine aqueous solution is a raw product from a biological fermentation process (purchased from Meihua Bio-technology Group Co., Ltd.), and the amyl alcohol, hexanol and octanol are commercially available products.

[0044] The content of lysine and the content of aminocaproamide in the material are analyzed by liquid chromatography external standard method.

[0045] The reaction conversion rate X and the selectivity S are calculated by the following formula:

[0046]

[0047]

[0048] In the formula, w represents the mass fraction, LYS and N-CPL represent lysine and aminocaproamide, respectively, and in and out represent the inlet and outlet of the reactor, respectively.

[0049] Comparative Example 1

[0050] Comparative Example 1 uses a mixture of lysine and n-hexanol to synthesize aminocaproamide in a batch kettle. The lysine raw material is selected from a raw product from a biological fermentation process (a lysine aqueous solution with a concentration of 60 wt%). The molar ratio of n-hexanol to lysine in the reaction material is 6.0, the reaction temperature is 180°C, the reactor pressure is 1.0 MPa (Table), and the reaction time is 5 h. The reaction results are shown in Table 1. Other by-products are polypeptide substances generated by intermolecular dehydration of lysine molecules. After the reaction, the material is subjected to dehydration by fractional distillation and removal of the auxiliary agent to obtain the aminocaproamide product.

[0051] Example 1

[0052] The process flow of Example 1 is shown in the accompanying Figure 1As shown, the reaction rectification column 2 is composed of an upper rectification section I and a lower reaction section II, the reaction feed 1 is introduced into the reaction rectification column 2 from the middle part and flows downward together with the reflux liquid from the rectification section I through the reaction section II, and in the presence of n-hexanol, lysine is dehydrated to form aminocaproamide. A reboiler 8 is arranged at the bottom of the reaction rectification column, and the ascending vapor is the azeotrope of n-hexanol and water. The reaction pressure is the bubble point pressure of the azeotrope of n-hexanol and water at the reaction temperature, and the vapor phase azeotrope of the overhead product 3 is condensed by a condenser 4 and then enters a liquid-liquid two-phase separator 5 for phase separation. A structure as shown in the drawing is arranged at the inlet of the liquid-liquid two-phase separator, and the liquid-liquid two-phase separator is composed of a liquid-liquid two-phase separation section and a liquid-liquid two-phase separation section. Figure 2 As shown in the fiber filament contactor, the n-hexanol containing water is taken from the top of the liquid-liquid two-phase separator as the column top reflux 6, and the water content is 8wt%; the water phase 7 containing a small amount of n-hexanol is taken from the bottom of the liquid-liquid two-phase separator and discharged. The bottom product 9 of the reaction rectification column is the n-hexanol solution of aminocaproamide, which is sent to the auxiliary agent recovery column 10, and the recovered auxiliary agent 11 and the aminocaproamide target product 12 are separated and obtained, and the recovered auxiliary agent is returned to the reaction rectification column 2. The rectification section of the reaction rectification column is packed with packing, and the reaction section is provided with trays, and the total theoretical plate number is 16-18.

[0053] The reaction feed is the same as that of the comparative example 1, and the molar ratio of n-hexanol to lysine is 5.0. The apparent residence time of the reaction feed in the reaction section of the reaction rectification column is 4h, and the other operating conditions are shown in Table 1, and the reaction results are shown in Table 2.

[0054] Compared with the comparative example 1, the auxiliary agent ratio of the example 1 is lower, and the distillation energy consumption of the auxiliary agent recovery column is lower, and the energy consumption data are shown in Table 3.

[0055] Example 2

[0056] The process flow and reaction equipment of the example 2 are the same as those of the example 1, except that the concentration of the lysine aqueous solution is 10wt%, n-octanol is used as the auxiliary agent, and the molar ratio of n-octanol to lysine is 3.7. The liquid droplet coalescence strengthening structure at the inlet of the liquid-liquid two-phase separator is a stainless steel hydrophilic packing.

[0057] The n-octanol containing water is taken from the top of the liquid-liquid two-phase separator and refluxed, the water is taken from the bottom of the liquid-liquid two-phase separator and discharged, and the n-octanol solution of aminocaproamide containing no water is taken from the bottom of the reaction rectification column and sent to the auxiliary agent recovery column for separation. The apparent residence time of the reaction feed in the reaction section is 4h. Different from the example 1, in the auxiliary agent recovery column, the aminocaproamide product is taken from the top, and the n-octanol is taken from the bottom and returned to the reaction rectification column. The other operating conditions are shown in Table 1, and the reaction results are shown in Table 2.

[0058] Example 3

[0059] The process flow and reaction equipment of Example 3 are the same as those of Example 1, except that the concentration of the aqueous lysine solution is 35 wt%, a lower boiling point pentanol is used as the assistant in Example 3, the molar ratio of the pentanol to lysine is 8.0, the raw material composition of the lysine is the same as that of Comparative Example 1, the apparent residence time of the reaction feed in the reaction section is 2 h, and other reaction conditions are shown in Table 1, and the reaction results are shown in Table 2.

[0060] Table 1

[0061]

[0062] Table 2

[0063] Comparative Example Comparative Example 1 Example 1 Example 2 Example 3 Lysine conversion, % 84.5 96.8 94.7 97.6 Aminocaproamide selectivity, % 60.1 95.3 94.8 93.4

[0064] Table 3

[0065] Comparative Example Comparative Example 1 Example 1 Alcohol recovery column heat consumption, MJ / kg product 30.24 24.24

[0066] As shown in Tables 2 and 3, compared with Comparative Example 1, the conversion rate of the amino acid reaction in the method provided by the present application is increased by 10-13 percentage points, the selectivity is increased by 33-35 percentage points, and the energy consumption is reduced by about 20%.

Claims

1. A continuous process for the production of a lactam monomer, characterized in that, The raw material containing amino acid and the assistant are fed into the middle part of the reaction rectifying tower, and the amino acid is subjected to intramolecular dehydration and cyclization to generate lactam monomer. The top discharge of the reaction rectifying tower is fed into the liquid-liquid two-phase separator through a condenser. The separated assistant is returned to the reaction rectifying tower, and the separated water is discharged. A reboiler is arranged at the bottom of the reaction rectifying tower, and the tower kettle discharge is fed into the assistant recovery tower for fractionation. The obtained assistant is returned to the reaction rectifying tower, and the lactam monomer product is recovered. The assistant is C5-C8 alcohol. The raw material containing amino acid is selected from one or more of lysine, lysine salt and lysine aqueous solution obtained by biological fermentation. The reaction rectifying tower is provided with a reaction section below the feed position and a rectifying section above the feed position. The temperature of the reaction section of the reaction rectifying tower is 140-300 DEG C, the top temperature is 80-200 DEG C, and the pressure is the bubble point pressure of the assistant or the azeotrope formed by the assistant and water at the reaction temperature.

2. The continuous production process of a lactam monomer according to claim 1, characterized in that, The raw material containing amino acid is 1wt%-60wt% lysine aqueous solution.

3. The continuous production process of a lactam monomer according to claim 1 or 2, characterized in that, The molar ratio of the assistant to the amino acid in the reaction feed is 1-30:

1.

4. The continuous production process of a lactam monomer according to claim 3, characterized in that, The molar ratio of the assistant to the amino acid in the reaction feed is 2-20:

1.

5. The continuous production method of a lactam monomer according to claim 1 or 2, characterized by, In the reaction rectifying tower, the temperature of the reaction section is 150-250 DEG C, and the top temperature is 100-180 DEG C.

6. The continuous production method of a lactam monomer according to claim 1 or 2, characterized by, The residence time of the raw material containing amino acid in the reaction section is 0.5-10 h.

7. The continuous production process of a lactam monomer according to claim 6, characterized in that, The residence time of the raw material containing amino acid in the reaction section is 1.0-6.0 h.

8. The continuous production method of a lactam monomer according to claim 1 or 2, characterized by, The reaction rectifying tower is filled with trays or packing, and the theoretical tray number is 5-30.

9. The continuous production process of a lactam monomer according to claim 1 or 2, characterized in that, The liquid-liquid two-phase separator includes a tank body and a flow separation baffle. The flow separation baffle separates the internal space of the tank body into two parts that are in communication with each other and are separated in the middle. One end of the tank body is provided with a two-phase separator section inlet, the other end is provided with an assistant outlet, and the bottom of the tank body is provided with a water bag and a water phase outlet.

10. The continuous production process of a lactam monomer according to claim 9, characterized in that, The liquid-liquid two-phase separator inlet is provided with a liquid droplet coalescence strengthening structure and is filled with fiber filaments or surface coalescence packing.

11. The continuous production process of a lactam monomer according to claim 1 or 2, characterized in that, The operation conditions of the assistant recovery tower are as follows: the operating pressure is 1-50 kPa (absolute pressure), the tower kettle temperature is 60-150 DEG C, and the reflux ratio is 1.0-15.

0.

12. A continuous production system of a lactam monomer for the continuous production method of a lactam monomer according to any one of claims 1 to 11, characterized by, The reaction rectifying tower and the assistant recovery tower are connected. The middle part of the reaction rectifying tower is provided with a raw material and assistant inlet. The vapor phase outlet at the top of the reaction rectifying tower is connected to the liquid-liquid two-phase separator through a top condenser. The alcohol and water phase outlet of the liquid-liquid two-phase separator is connected to the top reflux inlet. A reboiler and a tower kettle material outlet are arranged at the bottom of the reaction rectifying tower. The tower kettle material outlet is connected to the inlet of the assistant recovery tower. The recovered assistant outlet of the assistant recovery tower is connected to the assistant inlet of the reaction rectifying tower. The assistant recovery tower is also provided with a product outlet.

13. The lactam monomer continuous production system of claim 12, wherein, The liquid-liquid two-phase separator includes a tank body and a flow separation baffle. The flow separation baffle separates the internal space of the tank body into two parts that are in communication with each other and are separated in the middle. One end of the tank body is provided with a two-phase separator section inlet, the other end is provided with an assistant outlet, and the bottom of the tank body is provided with a water bag and a water phase outlet. The liquid-liquid two-phase separator inlet is provided with a liquid droplet coalescence strengthening structure and is filled with fiber filaments or surface coalescence packing.

Images