A method for separating and recovering piperazine-ethyl acetate-ethanol-water solution

Abstract

The invention relates to the technical field of organic matter purification, and discloses a separation and recovery method of piperazine-ethyl acetate-ethanol-water solution, comprising: distilling the piperazine-ethyl acetate-ethanol-water solution to separate piperazine and ethyl acetate-ethanol-water solution, dehydrating the ethyl acetate-ethanol-water solution to obtain an ethyl acetate-ethanol mixed solution; destroying the ethyl acetate-ethanol azeotrope by ionic liquid to separate ethyl acetate and ethanol; recovering ethanol and ionic liquid by flash evaporation; in industrial production, a large amount of ethyl acetate-ethanol mixed solution will be produced, and ethyl acetate and ethanol are easy to form azeotropes, which cannot be effectively separated by ordinary distillation methods. The invention utilizes simple distillation, ionic liquid replacement, and azeotropic distillation to achieve high-purity separation and recovery of piperazine, ethyl acetate and ethanol. The separation and recovery method disclosed by the invention has high yield, low energy consumption, good quality, can be reused, simple process, stable operation, and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of organic matter purification, in particular to a method for separating and recovering piperazine-ethyl acetate-ethanol-water solution. Background Art

[0002] With the continuous development of the modern chemical industry, the application of various pharmaceutical raw materials and intermediates such as ethyl acetate, ethanol, and piperazine has become more and more common. Ethyl acetate, also known as ethyl acetate, is a widely used ester that is miscible with ethanol. Because of its excellent solubility and quick drying properties, it is often used as an important organic chemical raw material and industrial solvent. Ethanol, commonly known as alcohol, is a flammable, volatile, low-toxic, colorless, transparent liquid at room temperature and pressure. Ethanol can dissolve a variety of organic and inorganic substances and is a widely used solvent. Piperazine, also known as p-diazepine, is soluble in water, ethanol and other solvents. Piperazine is not only an important pharmaceutical intermediate, but also widely used in pesticides, dyes, preservatives, antioxidants, surfactants and other fields.

[0003] In chemical and pharmaceutical production, it is often necessary to use a variety of pharmaceutical raw materials and intermediates at the same time. Therefore, in production, a large amount of waste solvents containing ethyl acetate, ethanol and piperazine are often produced. After incineration or discharge, it will cause great pollution to the environment. Therefore, the organic compounds in the waste solvents should be separated and recovered. However, the current methods for separating and purifying waste solvents are complicated, which is not only difficult to purify but also costly.

[0004] Therefore, there is an urgent need for a method for separating and recovering ethyl acetate, ethanol and piperazine in waste solvents with high purity. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for separating and recovering a piperazine-ethyl acetate-ethanol-water solution, comprising:

[0006] Step 1, distilling piperazine-ethyl acetate-ethanol-water solution to obtain piperazine crude product and ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam;

[0007] Step 2, condensing the ethyl acetate-ethanol azeotropic steam, the ethanol-water azeotropic steam, the ethyl acetate-water azeotropic steam and the ethyl acetate-ethanol-water ternary azeotropic steam obtained in step 1 to obtain an ethyl acetate-ethanol-water solution;

[0008] Step 3, dehydrating the ethyl acetate-ethanol-water solution obtained in step 2 to obtain an ethyl acetate-ethanol mixed solution;

[0009] Step 4, placing the ethyl acetate-ethanol mixed solution and the ionic liquid obtained in step 3 into a distillation tower for distillation to obtain ethyl acetate vapor and an ethanol-ionic liquid mixed solution;

[0010] Step 5, placing the ethanol-ionic liquid mixed solution obtained in step 4 into a distillation device for flash evaporation to obtain ethanol vapor and ionic liquid;

[0011] Step 6, condensing the ethyl acetate vapor obtained in step 4 and the ethanol vapor obtained in step 5 to obtain ethyl acetate and ethanol respectively;

[0012] Step 7: dehydrating the crude piperazine obtained in step 1 to obtain anhydrous piperazine.

[0013] Furthermore, in step 1, the distillation temperature is 65-95°C.

[0014] Furthermore, in step 3, the dehydration is osmotic membrane dehydration.

[0015] Furthermore, the steam flow rate of the permeable membrane dehydration is 1-3m 3 / Hour.

[0016] Furthermore, in step 4, the ionic liquid is 1-ethyl-3-methylimidazolium acetate or 1,3-disulfonate imidazole aluminum tetrachloride.

[0017] Furthermore, the addition amount of the 1-ethyl-3-methylimidazolium acetate or the 1,3-disulfonate imidazole aluminum tetrachloride is 0.5-1 times the volume of the ethyl acetate-ethanol mixture.

[0018] Furthermore, in step 5, the absolute pressure of the flash evaporation is 20 atm, and the temperature of the flash evaporation is 5°C.

[0019] Furthermore, in step 7, the dehydration is azeotropic distillation dehydration.

[0020] Furthermore, the conditions for the azeotropic distillation dehydration are: distillation bottom temperature 105-145°C, liquid temperature in the kettle 80-140°C, kettle top temperature 80-105°C, and controlled reflux ratio 20:1-1:1

[0021] Compared with the prior art, the beneficial effects are:

[0022] The embodiment of the present invention discloses a separation and recovery method of piperazine-ethyl acetate-ethanol-water solution, comprising: distilling the piperazine-ethyl acetate-ethanol-water solution to separate piperazine and ethyl acetate-ethanol-water solution, dehydrating the ethyl acetate-ethanol-water solution to obtain an ethyl acetate-ethanol mixed solution, destroying the azeotropy of ethyl acetate-ethanol by an ionic liquid, thereby separating ethyl acetate and ethanol, and finally recovering ethanol and the ionic liquid by flash distillation. In industrial production, a large amount of ethyl acetate and ethanol mixed solution is produced, and ethyl acetate and ethanol are easy to form azeotropes, which cannot be effectively separated by ordinary distillation methods. The present invention utilizes simple distillation, ionic liquid replacement, and azeotropic distillation to achieve high-purity separation and recovery of piperazine, ethyl acetate, and ethanol. The separation and recovery method disclosed in the present invention has high yield, low energy consumption, good quality, can be reused, simple production process, stable operation, and is suitable for industrial production. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] This embodiment provides a method for separating and recovering a piperazine-ethyl acetate-ethanol-water solution, comprising:

[0026] Step 1, distilling piperazine-ethyl acetate-ethanol-water solution at a specific distillation temperature of 95° C. to obtain piperazine crude product and ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam;

[0027] Step 2, condensing the ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam obtained in step 1 to obtain an ethyl acetate-ethanol-water solution;

[0028] Step 3: Dehydrate the ethyl acetate-ethanol-water solution obtained in step 2 by membrane dehydration. The steam flow rate of the membrane dehydration is 3m 3 / hour, to obtain an ethyl acetate-ethanol mixed solution;

[0029] Step 4, placing the ethyl acetate-ethanol mixed solution and the ionic liquid obtained in step 3 into a distillation tower for distillation, wherein the ionic liquid is specifically 1-ethyl-3-methylimidazolium acetate, the amount of the ionic liquid added is 1 times the volume of the ethyl acetate-ethanol mixed solution, and the distillation conditions are: the distillation bottom temperature is 112° C., the liquid temperature in the kettle is 110° C., the kettle top temperature is 85° C., and the reflux ratio is controlled to be 20:1, to obtain ethyl acetate vapor and ethanol-ionic liquid mixed solution; specifically, the ethanol-ionic liquid is a mixed solution of ethanol and 1-ethyl-3-methylimidazolium acetate;

[0030] Step 5, placing the ethanol-ionic liquid mixed solution obtained in step 4 into a flash tank for flash evaporation, the absolute pressure of the flash evaporation is 20 atm, the temperature of the flash evaporation is 5° C., and ethanol vapor and ionic liquid are obtained;

[0031] Step 6, condensing the ethyl acetate vapor obtained in step 4 and the ethanol vapor obtained in step 5 to obtain ethyl acetate and ethanol respectively;

[0032] Step 7, dehydrating the crude piperazine obtained in step 1, wherein the dehydration method is as follows: adding azeotropic agent cyclohexane to the crude piperazine for azeotropic distillation, and the conditions for azeotropic distillation are: distillation kettle bottom temperature 145°C, kettle liquid temperature 140°C, kettle top temperature 105°C, and controlling the reflux ratio to 1:1 to obtain anhydrous piperazine.

[0033] Example 2

[0034] This embodiment provides a method for separating and recovering a piperazine-ethyl acetate-ethanol-water solution, comprising:

[0035] Step 1, distilling piperazine-ethyl acetate-ethanol-water solution at a specific distillation temperature of 65° C. to obtain piperazine crude product and ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam;

[0036] Step 2, condensing the ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam obtained in step 1 to obtain an ethyl acetate-ethanol-water solution;

[0037] Step 3: Dehydrate the ethyl acetate-ethanol-water solution obtained in step 2 by membrane dehydration. The steam flow rate of the membrane dehydration is 1m 3 / hour, to obtain an ethyl acetate-ethanol mixed solution;

[0038] Step 4, placing the ethyl acetate-ethanol mixed solution and the ionic liquid obtained in step 3 into a distillation tower for distillation, wherein the ionic liquid is specifically 1-ethyl-3-methylimidazolium acetate, and the amount of the ionic liquid added is 0.5 times the volume of the ethyl acetate-ethanol mixed solution, and the distillation conditions are: the distillation bottom temperature is 72° C., the liquid temperature in the kettle is 70° C., the kettle top temperature is 68° C., and the reflux ratio is controlled to be 20:1, to obtain ethyl acetate vapor and ethanol-ionic liquid mixed solution; specifically, the ethanol-ionic liquid is a mixed solution of ethanol and 1-ethyl-3-methylimidazolium acetate;

[0039] Step 5, placing the ethanol-ionic liquid mixed solution obtained in step 4 into a flash tank for flash evaporation, the absolute pressure of the flash evaporation is 5 atm, the temperature of the flash evaporation is 72° C., and ethanol vapor and ionic liquid are obtained;

[0040] Step 6, condensing the ethyl acetate vapor obtained in step 4 and the ethanol vapor obtained in step 5 to obtain ethyl acetate and ethanol respectively;

[0041] Step 7, dehydrating the crude piperazine obtained in step 1, the dehydration method is as follows: adding azeotropic agent cyclohexane to the crude piperazine for azeotropic distillation, the conditions of azeotropic distillation are: distillation kettle bottom temperature 85°C, kettle liquid temperature 80°C, kettle top temperature 80°C, controlling the reflux ratio to 20:1, to obtain anhydrous piperazine.

[0042] Example 3

[0043] Step 1, distilling piperazine-ethyl acetate-ethanol-water solution at a specific distillation temperature of 70° C. to obtain piperazine crude product and ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam;

[0044] Step 2, condensing the ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam obtained in step 1 to obtain an ethyl acetate-ethanol-water solution;

[0045] Step 3: Dehydrate the ethyl acetate-ethanol-water solution obtained in step 2 by membrane dehydration. The steam flow rate of the membrane dehydration is 2m 3 / hour, to obtain an ethyl acetate-ethanol mixed solution;

[0046] Step 4, placing the ethyl acetate-ethanol mixed solution and the ionic liquid obtained in step 3 into a distillation tower for distillation, wherein the ionic liquid is specifically 1-ethyl-3-methylimidazolium acetate, and the amount of the ionic liquid added is 0.75 times the volume of the ethyl acetate-ethanol mixed solution. The distillation conditions are: the bottom temperature of the distillation kettle is 95° C., the liquid temperature in the kettle is 80° C., the top temperature of the kettle is 73° C., and the reflux ratio is controlled to be 5:1, to obtain ethyl acetate vapor and ethanol-ionic liquid mixed solution; specifically, the ethanol-ionic liquid is a mixed solution of ethanol and 1-ethyl-3-methylimidazolium acetate;

[0047] Step 5, placing the ethanol-ionic liquid mixed solution obtained in step 4 into a flash tank for flash evaporation, the absolute pressure of the flash evaporation is 13 atm, the temperature of the flash evaporation is 80° C., and ethanol vapor and ionic liquid are obtained;

[0048] Step 6, condensing the ethyl acetate vapor obtained in step 4 and the ethanol vapor obtained in step 5 to obtain ethyl acetate and ethanol respectively;

[0049] Step 7, dehydrating the crude piperazine obtained in step 1, the dehydration method is as follows: adding azeotropic agent cyclohexane to the crude piperazine for azeotropic distillation, the conditions of azeotropic distillation are: distillation kettle bottom temperature 100°C, kettle liquid temperature 95°C, kettle top temperature 90°C, controlling the reflux ratio to 15:1, to obtain anhydrous piperazine.

[0050] Example 4

[0051] This embodiment provides a method for separating and recovering a piperazine-ethyl acetate-ethanol-water solution, comprising:

[0052] Step 1, distilling piperazine-ethyl acetate-ethanol-water solution at a specific distillation temperature of 92° C. to obtain piperazine crude product and ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam;

[0053] Step 2, condensing the ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam obtained in step 1 to obtain an ethyl acetate-ethanol-water solution;

[0054] Step 3: Dehydrate the ethyl acetate-ethanol-water solution obtained in step 2 by membrane dehydration. The steam flow rate of the membrane dehydration is 3m 3 / hour, to obtain an ethyl acetate-ethanol mixed solution;

[0055] Step 4, placing the ethyl acetate-ethanol mixed solution and the ionic liquid obtained in step 3 into a distillation tower for distillation, wherein the ionic liquid is specifically 1,3-disulfonate imidazole aluminum tetrachloride, and the amount of the ionic liquid added is 1 times the volume of the ethyl acetate-ethanol mixed solution. The distillation conditions are: the bottom temperature of the distillation kettle is 112° C., the liquid temperature in the kettle is 110° C., the top temperature of the kettle is 85° C., and the reflux ratio is controlled to be 20:1, to obtain ethyl acetate vapor and ethanol-ionic liquid mixed solution; specifically, the ethanol-ionic liquid is a mixed solution of ethanol and 1,3-disulfonate imidazole aluminum tetrachloride;

[0056] Step 5, placing the ethanol-ionic liquid mixed solution obtained in step 4 into a flash tank for flash evaporation, the absolute pressure of the flash evaporation is 20 atm, the temperature of the flash evaporation is 5° C., and ethanol vapor and ionic liquid are obtained;

[0057] Step 6, condensing the ethyl acetate vapor obtained in step 4 and the ethanol vapor obtained in step 5 to obtain ethyl acetate and ethanol respectively;

[0058] Step 7, dehydrating the crude piperazine obtained in step 1, wherein the dehydration method is as follows: adding azeotropic agent cyclohexane to the crude piperazine for azeotropic distillation, and the conditions for azeotropic distillation are: distillation kettle bottom temperature 145°C, kettle liquid temperature 140°C, kettle top temperature 105°C, and controlling the reflux ratio to 1:1 to obtain anhydrous piperazine.

[0059] Example 5

[0060] This embodiment provides a method for separating and recovering a piperazine-ethyl acetate-ethanol-water solution, comprising:

[0061] Step 1, distilling piperazine-ethyl acetate-ethanol-water solution at a specific distillation temperature of 68° C. to obtain piperazine crude product and ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam;

[0062] Step 2, condensing the ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam obtained in step 1 to obtain an ethyl acetate-ethanol-water solution;

[0063] Step 3: Dehydrate the ethyl acetate-ethanol-water solution obtained in step 2 by membrane dehydration. The steam flow rate of the membrane dehydration is 1m 3 / hour, to obtain an ethyl acetate-ethanol mixed solution;

[0064] Step 4, placing the ethyl acetate-ethanol mixed solution and the ionic liquid obtained in step 3 into a distillation tower for distillation, wherein the ionic liquid is specifically 1,3-disulfonate imidazole aluminum tetrachloride, and the amount of the ionic liquid added is 0.5 times the volume of the ethyl acetate-ethanol mixed solution. The distillation conditions are: the bottom temperature of the distillation kettle is 72° C., the liquid temperature in the kettle is 70° C., the top temperature of the kettle is 68° C., and the reflux ratio is controlled to be 20:1, to obtain ethyl acetate vapor and ethanol-ionic liquid mixed solution; specifically, the ethanol-ionic liquid is a mixed solution of ethanol and 1,3-disulfonate imidazole aluminum tetrachloride;

[0065] Step 5, placing the ethanol-ionic liquid mixed solution obtained in step 4 into a flash tank for flash evaporation, the absolute pressure of the flash evaporation is 5 atm, the temperature of the flash evaporation is 72° C., and ethanol vapor and ionic liquid are obtained;

[0066] Step 6, condensing the ethyl acetate vapor obtained in step 4 and the ethanol vapor obtained in step 5 to obtain ethyl acetate and ethanol respectively;

[0067] Step 7, dehydrating the crude piperazine obtained in step 1, the dehydration method is as follows: adding azeotropic agent cyclohexane to the crude piperazine for azeotropic distillation, the conditions of azeotropic distillation are: distillation kettle bottom temperature 85°C, kettle liquid temperature 80°C, kettle top temperature 80°C, controlling the reflux ratio to 20:1, to obtain anhydrous piperazine.

[0068] Example 6

[0069] Step 1, distilling piperazine-ethyl acetate-ethanol-water solution at a specific distillation temperature of 78° C. to obtain piperazine crude product and ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam;

[0070] Step 2, condensing the ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam obtained in step 1 to obtain an ethyl acetate-ethanol-water solution;

[0071] Step 3: Dehydrate the ethyl acetate-ethanol-water solution obtained in step 2 by membrane dehydration. The steam flow rate of the membrane dehydration is 1m 3 / hour, to obtain an ethyl acetate-ethanol mixed solution;

[0072] Step 4, placing the ethyl acetate-ethanol mixed solution and the ionic liquid obtained in step 3 into a distillation tower for distillation, wherein the ionic liquid is specifically 1,3-disulfonate imidazolium tetrachloride aluminum salt, and the amount of the ionic liquid added is 0.85 times the volume of the ethyl acetate-ethanol mixed solution. The distillation conditions are: the bottom temperature of the distillation kettle is 84° C., the liquid temperature in the kettle is 70° C., the top temperature of the kettle is 70° C., and the reflux ratio is controlled to be 13:1, to obtain ethyl acetate vapor and ethanol-ionic liquid mixed solution; specifically, the ethanol-ionic liquid is a mixed solution of ethanol and 1,3-disulfonate imidazolium tetrachloride aluminum salt;

[0073] Step 5, placing the ethanol-ionic liquid mixed solution obtained in step 4 into a flash tank for flash evaporation, the absolute pressure of the flash evaporation is 9 atm, the temperature of the flash evaporation is 78° C., and ethanol vapor and ionic liquid are obtained;

[0074] Step 6, condensing the ethyl acetate vapor obtained in step 4 and the ethanol vapor obtained in step 5 to obtain ethyl acetate and ethanol respectively;

[0075] Step 7, dehydrating the crude piperazine obtained in step 1, the dehydration method is as follows: adding azeotropic agent cyclohexane to the crude piperazine for azeotropic distillation, the conditions of azeotropic distillation are: distillation kettle bottom temperature 120°C, kettle liquid temperature 115°C, kettle top temperature 95°C, controlling the reflux ratio to 10:1, to obtain anhydrous piperazine.

[0076] The technical indicators of the purified anhydrous piperazine of Examples 1 to 6 are shown in Table 1:

[0077] Table 1

[0078] name Purity (wt%) Water content (wt%) Anhydrous Grade Standard ≥99.5％ ≤0.5％ Example 1 99.6 0.4 Example 2 99.8 0.2 Example 3 99.8 0.2 Example 4 99.6 0.4 Example 5 99.7 0.3 Example 6 99.6 0.4

[0079] The technical indicators of the purified industrial-grade ethyl acetate of Examples 1 to 6 are shown in Table 2:

[0080] Table 2

[0081]

[0082] The technical indicators of the industrial-grade anhydrous ethanol after purification in Examples 1 to 6 are shown in Table 3:

[0083] Table 3

[0084]

[0085] In summary, the present invention provides a separation and recovery method of piperazine-ethyl acetate-ethanol-water solution, comprising: distilling piperazine-ethyl acetate-ethanol-water solution to separate piperazine and ethyl acetate-ethanol-water solution, dehydrating the ethyl acetate-ethanol-water solution to obtain an ethyl acetate-ethanol mixed solution; destroying the ethyl acetate-ethanol azeotrope by ionic liquid to separate ethyl acetate and ethanol; recovering ethanol and ionic liquid by flash evaporation; in industrial production, a large amount of ethyl acetate-ethanol mixed solution will be produced, and ethyl acetate and ethanol are easy to form azeotropes, which cannot be effectively separated by ordinary distillation methods. The present invention utilizes simple distillation, ionic liquid replacement, and azeotropic distillation to achieve high-purity separation and recovery of piperazine, ethyl acetate, and ethanol. The separation and recovery method disclosed in the present invention has high yield, low energy consumption, good quality, can be reused, simple process, stable operation, and is suitable for industrial production.

[0086] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the scheme disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0087] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for separating and recovering a piperazine-ethyl acetate-ethanol-water solution, characterized in that: include: Step 1, distilling piperazine-ethyl acetate-ethanol-water solution to obtain piperazine crude product and ethyl acetate-ethanol azeotropic steam, ethanol-water azeotropic steam, ethyl acetate-water azeotropic steam and ethyl acetate-ethanol-water ternary azeotropic steam; Step 2, condensing the ethyl acetate-ethanol azeotropic steam, the ethanol-water azeotropic steam, the ethyl acetate-water azeotropic steam and the ethyl acetate-ethanol-water ternary azeotropic steam obtained in step 1 to obtain an ethyl acetate-ethanol-water solution; Step 3, dehydrating the ethyl acetate-ethanol-water solution obtained in step 2 to obtain an ethyl acetate-ethanol mixed solution; Step 4, placing the ethyl acetate-ethanol mixed solution and the ionic liquid obtained in step 3 into a distillation tower for distillation to obtain ethyl acetate vapor and ethanol-ionic liquid mixed solution; Step 5, placing the ethanol-ionic liquid mixed solution obtained in step 4 into a distillation device for flash evaporation to obtain ethanol vapor and ionic liquid; Step 6, condensing the ethyl acetate vapor obtained in step 4 and the ethanol vapor obtained in step 5 to obtain ethyl acetate and ethanol respectively; Step 7, dehydrating the crude piperazine obtained in step 1 to obtain anhydrous piperazine; the distillation temperature is 65-95°C; the dehydration is permeable membrane dehydration; the steam flow rate of the permeable membrane dehydration is 1-3m 3 / hour; the ionic liquid is 1-ethyl-3-methylimidazolium acetate or 1,3-disulfonate imidazolium tetrachloride; the addition amount of the 1-ethyl-3-methylimidazolium acetate or the 1,3-disulfonate imidazolium tetrachloride is 0.5-1 times the volume of the ethyl acetate-ethanol mixture; the absolute pressure of the flash evaporation is 20atm, and the temperature of the flash evaporation is 5°C; the dehydration is azeotropic distillation dehydration; the conditions of the azeotropic distillation dehydration are: the distillation bottom temperature is 105-145°C, the liquid temperature in the kettle is 80-140°C, the kettle top temperature is 80-105°C, and the reflux ratio is controlled at 20:1-1:1.

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