Method for extracting, rectifying and separating ethanole-2-pentanone azeotropic system by using tetramethylammonium chloride eutectic solvent

Abstract

The invention provides a method for extracting, rectifying and separating an ethano-2-pentanone azeotropic system by using a tetramethylammonium chloride eutectic solvent, and relates to the technical field of extracting, rectifying and separating the ethano-2-pentanone azeotropic system, which comprises the following steps: taking an ethano-2-pentanone mixture as a raw material to be separated; the method comprises the following steps: mixing and stirring a hydrogen bond acceptor and a hydrogen bond donor according to a certain proportion and temperature to obtain the eutectic solvent, firstly heating a material S01 to be separated by a heat exchanger E101 and then entering the middle part of a T101 tower, adjusting a eutectic solvent material flow S02 to a proper temperature and then entering the upper part of the T101 tower, carrying out heat exchange on a tower top ethanol material flow S03, enabling a part of material flow S05 to flow back to the tower top, and carrying out heat exchange on a tower top ethanol material flow S03; according to the method, a specific eutectic solvent is adopted as an extracting agent, an extractive distillation process is matched, an ethano-2-pentanone azeotropic system can be effectively broken, the yields of ethanol and 2-pentanone can reach 99% or above finally, the purities of ethanol and 2-pentanone can reach 99.5% (mass percent) or above finally, and efficient separation is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of extractive distillation for separating ethanol-2-pentanone azeotropic system, and more specifically, particularly relates to a method for separating ethanol-2-pentanone azeotropic system by extractive distillation with a quaternary ammonium chloride-based deep eutectic solvent. Background Art

[0002] 2-Pentanone is an important chemical in ketone compounds and is widely used in fields such as solvents, pharmaceutical intermediates, and essence production. Currently, in industry, 2-pentanone is mainly produced by processes such as heating an aqueous solution of ethyl butyroacetate, dehydrating valeraldehyde, and dehydrogenating 2-pentanol. There are problems that raw materials are not easily available and the cost is high, and a large amount of pollutants are generated during the synthesis reaction, which has a great impact on the environment. With the industrialization of coal-to-ethanol technology, the condensation of ethanol to prepare high-value-added 2-pentanone has become a research hotspot.

[0003] However, ethanol and 2-pentanone form a minimum azeotrope (azeotropic temperature 78°C, ethanol content 93.3 wt%) under normal pressure, and it is difficult to achieve efficient separation by ordinary distillation, which greatly limits the separation of 2-pentanone products and the production of high-purity 2-pentanone.

[0004] Special distillation mainly includes pressure swing distillation, azeotropic distillation, and extractive distillation. Compared with pressure swing distillation, extractive distillation has lower energy consumption, is flexible in operation, and is easy to control. Using a deep eutectic solvent (the receptor can be tetramethylammonium chloride, the donor can be ethylene glycol or urea or acetamide, and the mass ratio of the receptor to the donor is 1:2-8) as the extractant for extractive distillation can greatly reduce the energy consumption and fixed investment of the device compared with pressure swing distillation; compared with conventional solvent extractive distillation, the deep eutectic solvent has stable properties, strong selectivity, high solubility, low solvent-to-feed ratio, and low volatility, can reduce the loss of the extractant, avoid secondary pollution to the product, and can also be recycled by flash evaporation. Extractive distillation has a high separation efficiency when separating azeotropic systems, so this patent uses this method to separate the ethanol-2-pentanone azeotropic system. Summary of the Invention

[0005] In order to solve the above technical problems, the invention provides a method for separating ethanol-2-pentanone azeotropic system by extractive distillation with a quaternary ammonium chloride-based deep eutectic solvent to solve the above problems.

[0006] A method for separating the ethanol-2-pentanone azeotropic system by extractive distillation, using a deep eutectic solvent as the solvent, comprising the following steps: The raw material to be separated is an ethanol-2-pentanone mixture. The hydrogen bond acceptor and the hydrogen bond donor are mixed and stirred at a certain ratio and temperature to obtain a deep eutectic solvent. First, the material to be separated S01 is heated by a heat exchanger E101 and then enters the middle of column T101. The deep eutectic solvent stream S02 is adjusted to an appropriate temperature and then enters the upper part of column T101. The ethanol stream S03 at the top of the column is partially refluxed to the top of the column after heat exchange, and the ethanol stream S04 with a purity ≥ 99.5% is collected as the product; The stream S06 rich in deep eutectic solvent and 2-pentanone at the bottom of the column enters the middle of the solvent recovery column T102 after recovering heat through the heat exchanger E104. The stream S06 enters the solvent recovery column T102 from the middle. The light component 2-pentanone stream S07 with a purity ≥ 99.5% is obtained at the top of the column, and the deep eutectic solvent stream S08 that has been completely desorbed is obtained at the bottom of the column, and after entering E101 to recover heat, it is recycled for use.

[0007] Preferably, the acceptor of the deep eutectic solvent is tetramethylammonium chloride, the donor is ethylene glycol or urea or acetamide, and the mass ratio of the acceptor to the donor is 1:2 to 8. The operating conditions of the extractive distillation column T101 are as follows: the number of theoretical plates is 20 to 60, the feeding temperature of the material to be separated S01 is 30 to 60 °C, the bottom temperature of the column is 70 to 120 °C, the top temperature of the column is 55 to 80 °C, the reflux ratio is 0.1 to 0.9, the solvent-to-feed ratio is 0.4 to 0.8:1, and the operating pressure is 105 to 210 kPa. The operating conditions of the solvent recovery column T102 are as follows: the number of theoretical plates is 10 to 20, the bottom temperature of the column is 100 to 130 °C, the top temperature of the column is 60 to 95 °C, the reflux ratio is 0.1 to 1.2, and the operating pressure is 105 to 200 kPa.

[0008] Preferably, the content ranges of ethanol and 2-pentanone in the mixed material are not limited, and this method is applicable to ethanol-2-pentanone azeotropic mixtures with different contents. During the use of the deep eutectic solvent, it is recycled through flash regeneration. During the extractive distillation process, the deep eutectic solvent increases the relative volatility of the internal components in the ethanol-2-pentanone azeotropic system.

[0009] Preferably, the yields of ethanol and 2-pentanone finally obtained by this method both reach more than 99%, and the purities both reach more than 99.5% (mass percentage). The heat exchangers E101, E102, E103, and E104 are used to realize heat recovery and utilization to reduce the energy consumption of the entire process. Compared with conventional solvents, the deep eutectic solvent has the characteristics of strong selectivity, high solubility, low volatility, and low solvent-to-feed ratio.

[0010] Compared with the prior art, the present invention has the following beneficial effects: High separation efficiency: By using a specific deep eutectic solvent as the extractant and combining with extractive distillation process, it can effectively break the ethanol-2-pentanone azeotropic system. Eventually, the yields of ethanol and 2-pentanone can both reach over 99%, and the purities can both reach over 99.5% (mass percentage), achieving high-efficiency separation.

[0011] Cost reduction: The deep eutectic solvent has simple composition and is easy to obtain, with a low solvent-to-feed ratio and a low reflux ratio. Compared with conventional solvents, it can significantly reduce the solvent cost; meanwhile, the optimized process flow effectively reduces the operating energy consumption by recovering heat; compared with pressure swing distillation, the device energy consumption and fixed investment are greatly reduced, and the overall operating cost is significantly reduced.

[0012] Strong adaptability: The requirements for the component contents of ethanol and 2-pentanone in this deep eutectic solvent are not strict, and it can be applied to azeotropic mixtures of the above substances with different contents, having a wide application range.

[0013] Environmental protection advantages: The deep eutectic solvent has low volatility, reducing the loss of the extractant and avoiding secondary pollution to the product; and the solvent can be recycled through flash evaporation regeneration, which conforms to the concept of green chemistry and reduces resource waste and environmental pollution.

[0014] Process advantages: The extractive distillation process is relatively flexible and easy to control. The deep eutectic solvent has stable properties, strong selectivity and high solubility, and is more operable and reliable in actual production. Description of the drawings

[0015] Figure 1 is the topological diagram of the overall process steps for extractive distillation separation of the present invention; Figure 2 is the topological diagram of the heating system of the present invention; Figure 3 is the topological diagram of the T101 extractive distillation column system of the present invention; Figure 4 is the topological diagram of the solvent recovery system of the present invention. Detailed implementation manners

[0016] The following further describes in detail the implementation manners of the present invention in conjunction with the drawings and embodiments. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0017] Please refer to Figures 1-4, the present invention provides a method for separating the ethanol-2-pentanone azeotropic system by extractive distillation. The solvent used is a deep eutectic solvent, and the method includes the following steps: The raw material to be separated is an ethanol-2-pentanone mixture. The hydrogen bond acceptor and the hydrogen bond donor are mixed and stirred at a certain ratio and temperature to obtain a deep eutectic solvent. First, the material to be separated S01 is heated by a heat exchanger E101 and then enters the middle of tower T101. The deep eutectic solvent stream S02 is adjusted to an appropriate temperature and then enters the upper part of tower T101. The ethanol stream S03 at the top of the tower is partially refluxed to the top of the tower after heat exchange, and the ethanol stream S04 with a purity ≥ 99.5% is collected as a product; The stream S06 rich in deep eutectic solvent and 2-pentanone at the bottom of the tower enters the middle of the solvent recovery tower T102 after recovering heat through the heat exchanger E104. The stream S06 enters the solvent recovery tower T102 from the middle. The light component 2-pentanone stream S07 with a purity ≥ 99.5% is obtained at the top of the tower, and the deep eutectic solvent stream S08 that has been completely desorbed is obtained at the bottom of the tower, and after entering E101 to recover heat, it is recycled for use.

[0018] The acceptor of the deep eutectic solvent is tetramethylammonium chloride, and the donors are ethylene glycol or urea or acetamide. The mass ratio of the acceptor to the donor is 1:2 to 8. The operating conditions of the extractive distillation tower T101 are as follows: the number of theoretical plates is 20 to 60, the feeding temperature of the material to be separated S01 is 30 to 60 °C, the bottom temperature of the tower is 70 to 120 °C, the top temperature of the tower is 55 to 80 °C, the reflux ratio is 0.1 to 0.9, the solvent-to-feed ratio is 0.4 to 0.8:1, and the operating pressure is 105 to 210 kPa. The operating conditions of the solvent recovery tower T102 are as follows: the number of theoretical plates is 10 to 20, the bottom temperature of the tower is 100 to 130 °C, the top temperature of the tower is 60 to 95 °C, the reflux ratio is 0.1 to 1.2, and the operating pressure is 105 to 200 kPa.

[0019] The content ranges of ethanol and 2-pentanone in the mixed material are not limited. This method is applicable to ethanol-2-pentanone azeotropic mixtures with different contents. During the use of the deep eutectic solvent, it is recycled through flash regeneration. During the extractive distillation process, the deep eutectic solvent increases the relative volatility of the internal components in the ethanol-2-pentanone azeotropic system.

[0020] The yields of ethanol and 2-pentanone finally obtained by the method both reach over 99%, and the purities both reach over 99.5% (mass percentage). The heat exchangers E101, E102, E103, and E104 are used to realize heat recovery and utilization to reduce the energy consumption of the entire process. Compared with conventional solvents, the deep eutectic solvent has the characteristics of strong selectivity, high solubility, low volatility, and low solvent-to-feed ratio. Example

[0021] Example 1: 1. According to the process flow of Figure 1, the deep eutectic solvent used is tetramethylammonium chloride - ethylene glycol, and the mass ratio of the two is 1:2.

[0022] 2. The main components of the mixed waste liquid to be separated are ethanol and 2 - pentanone.

[0023] 3. Operating steps: First, the material stream S01 to be separated is heated by the heat exchanger E101 and then enters the 20th plate of the T101 column. The solvent enters the 5th plate of the T101 column through the E102 heat exchanger. Ethanol with a content ≥ 99.5% is obtained at the top of the column, denoted as the stream S04, and a mixture rich in 2 - pentanone and the deep eutectic solvent after removing the light components is obtained from the bottom of the column, denoted as the stream S06; the stream S06 enters the column T102 from the 6th plate. 2 - pentanone with a purity ≥ 99.5% is obtained at the top of the column, denoted as the stream S07, and the deep eutectic solvent stream S08 that has been stripped clean is obtained from the bottom of the column. After recovering heat through the E101, it enters the T101 for recycling.

[0024] 4. Operating conditions: The number of theoretical plates of the extractive distillation column T101 is 40. The feed temperature of the material stream S01 to be separated is 40 °C, the bottom temperature of the column is 90 °C, the top temperature of the column is 65 °C, the reflux ratio is 0.3, the solvent - to - feed ratio is 0.5:1, and the operating pressure is 120 kPa; the number of theoretical plates of the solvent recovery column T102 is 12, the bottom temperature of the column is 115 °C, the top temperature of the column is 75 °C, the reflux ratio is 0.3, and the operating pressure is 130 kPa.

[0025] 5. Results: The recovery rate of ethanol is 99.0% and the purity is 99.6%; the recovery rate of 2 - pentanone is 99.1% and the purity is 99.5%.

[0026] Example 2: 1. According to the process flow of Figure 1, the deep eutectic solvent used is tetramethylammonium chloride - urea, and the mass ratio of the two is 1:6.

[0027] 2. The main components of the mixed waste liquid to be separated are ethanol and 2 - pentanone.

[0028] 3. Operating steps: First, the material stream S01 to be separated is heated by the heat exchanger E101 and then enters the 28th plate of the T101 column. The solvent enters the 6th plate of the T101 column through the E102 heat exchanger. Ethanol with a content of ≥99.5% is obtained at the top of the column, denoted as the stream S04, and a mixture rich in 2-pentanone and deep eutectic solvent after removing light components is obtained from the bottom of the column, denoted as the stream S06; the stream S06 enters the column T102 from the 5th plate. 2-pentanone with a purity of ≥99.5% is obtained at the top of the column, denoted as the stream S07, and the deep eutectic solvent stream S08 that has been desorbed cleanly is obtained from the bottom of the column. After recovering heat through E101, it enters T101 for recycling.

[0029] 4. Operating conditions: The number of theoretical plates of the extractive distillation column T101 is 55. The feed temperature of the material stream S01 to be separated is 52 °C, the bottom temperature of the column is 105 °C, the top temperature of the column is 70 °C, the reflux ratio is 0.4, the solvent-to-feed ratio is 0.7:1, and the operating pressure is 130 kPa; the number of theoretical plates of the solvent recovery column T102 is 16, the bottom temperature of the column is 120 °C, the top temperature of the column is 80 °C, the reflux ratio is 0.4, and the operating pressure is 150 kPa.

[0030] 5. Results: The ethanol yield is 99.2% and the purity is 99.7%; the 2-pentanone yield is 99.2% and the purity is 99.6%.

[0031] Example 3: 1. According to the process flow of Figure 1, the deep eutectic solvent used is tetramethylammonium chloride - acetamide, and the mass ratio of the two is 1:8.

[0032] 2. The main components of the mixed waste liquid to be separated are ethanol and 2-pentanone.

[0033] 3. Operating steps: First, the material stream S01 to be separated is heated by the heat exchanger E101 and then enters the 25th plate of the T101 column. The solvent enters the 7th plate of the T101 column through the E102 heat exchanger. Ethanol with a content of ≥99.5% is obtained at the top of the column, denoted as the stream S04, and a mixture rich in 2-pentanone and deep eutectic solvent after removing light components is obtained from the bottom of the column, denoted as the stream S06; the stream S06 enters the column T102 from the 7th plate. 2-pentanone with a purity of ≥99.5% is obtained at the top of the column, denoted as the stream S07, and the deep eutectic solvent stream S08 that has been desorbed cleanly is obtained from the bottom of the column. After recovering heat through E101, it enters T101 for recycling.

[0034] 4. Operating conditions: The number of theoretical plates of the extractive distillation column T101 is 48. The feed temperature of the material stream S01 to be separated is 56 °C, the bottom temperature is 108 °C, the top temperature is 75 °C, the reflux ratio is 0.6, the solvent-to-feed ratio is 0.8:1, and the operating pressure is 125 kPa; the number of theoretical plates of the solvent recovery column T102 is 18, the bottom temperature is 125 °C, the top temperature is 85 °C, the reflux ratio is 0.5, and the operating pressure is 160 kPa.

[0035] 5. Results: The yield of ethanol is 99.1% and the purity is 99.8%; the yield of 2-pentanone is 99.4% and the purity is 99.7%.

[0036] Example 4: 1. According to the process flow in Figure 1, the deep eutectic solvent used is tetramethylammonium chloride - ethylene glycol, and the mass ratio of the two is 1:4.

[0037] 2. The main components of the mixed waste liquid to be separated are ethanol and 2-pentanone.

[0038] 3. Operating steps: First, the material stream S01 to be separated is heated by the heat exchanger E101 and then enters the 35th plate of the T101 column. The solvent enters the 8th plate of the T101 column through the heat exchanger E102. Ethanol with a content ≥ 99.5% is obtained at the top of the column, denoted as the material stream S04. A mixture rich in 2-pentanone and the deep eutectic solvent after removing light components is obtained from the bottom of the column, denoted as the material stream S06; the material stream S06 enters the column T102 from the 9th plate. 2-Pentanone with a purity ≥ 99.5% is obtained at the top of the column, denoted as the material stream S07. The deep eutectic solvent material stream S08 that has been thoroughly desorbed is obtained from the bottom of the column and enters T101 for recycling after recovering heat through E101.

[0039] 4. Operating conditions: The number of theoretical plates of the extractive distillation column T101 is 52. The feed temperature of the material stream S01 to be separated is 45 °C, the bottom temperature is 95 °C, the top temperature is 68 °C, the reflux ratio is 0.25, the solvent-to-feed ratio is 0.6:1, and the operating pressure is 115 kPa; the number of theoretical plates of the solvent recovery column T102 is 14, the bottom temperature is 118 °C, the top temperature is 78 °C, the reflux ratio is 0.35, and the operating pressure is 140 kPa.

[0040] 5. Results: The yield of ethanol is 99.1% and the purity is 99.7%; the yield of 2-pentanone is 99.3% and the purity is 99.6%.

[0041] Example 5: 1. According to the process flow of Figure 1, the deep eutectic solvent used is tetramethylammonium chloride - urea, and the mass ratio of the two is 1:7.

[0042] 2. The main components of the mixed waste liquid to be separated are ethanol and 2 - pentanone.

[0043] 3. Operating steps: First, the material stream S01 to be separated is heated by the heat exchanger E101 and then enters the 26th plate of the T101 tower. The solvent enters the 7th plate of the T101 tower through the E102 heat exchanger. Ethanol with a content of ≥99.5% is obtained at the top of the tower, denoted as the stream S04, and a mixture rich in 2 - pentanone and the deep eutectic solvent after removing light components is obtained from the bottom of the tower, denoted as the stream S06; the stream S06 enters the tower T102 from the 5th plate. 2 - pentanone with a purity of ≥99.5% is obtained at the top of the tower, denoted as the stream S07, and the deep eutectic solvent stream S08 that has been stripped clean is obtained from the bottom of the tower. After recovering heat through the E101, it enters the T101 for recycling.

[0044] 4. Operating conditions: The number of theoretical plates of the extractive distillation tower T101 is 50. The feeding temperature of the material stream S01 to be separated is 53°C, the bottom temperature of the tower is 107°C, the top temperature of the tower is 71°C, the reflux ratio is 0.35, the solvent - to - feed ratio is 0.7:1, and the operating pressure is 135 kPa; the number of theoretical plates of the solvent recovery tower T102 is 15, the bottom temperature of the tower is 122°C, the top temperature of the tower is 82°C, the reflux ratio is 0.45, and the operating pressure is 155 kPa.

[0045] 5. Results: The recovery rate of ethanol is 99.2% and the purity is 99.7%; the recovery rate of 2 - pentanone is 99.3% and the purity is 99.7%.

[0046] Comparison of examples: 1. Influence of deep eutectic solvent composition: Deep eutectic solvents with different donors have a certain influence on the separation effect. Within the same range of operating conditions, the purity of 2 - pentanone in the tetramethylammonium chloride - acetamide system is slightly higher than that of other systems in some examples, such as Example 3 and Example 6; while for the tetramethylammonium chloride - ethylene glycol and tetramethylammonium chloride - urea systems, the recovery rates and purities of ethanol and 2 - pentanone can also reach relatively high levels at different ratios, indicating that deep eutectic solvents with different donors can all achieve effective separation, but there may be differences in some properties.

[0047] 2. Influence of mass ratio: With the change of the mass ratio of the receptor to the donor, the separation effect is different. Generally speaking, within a certain range, appropriately increasing the proportion of the donor has a tendency to increase the purity of the product. For example, in the tetramethylammonium chloride - urea system, from Example 2 (mass ratio 1:5) to Example 8 (mass ratio 1:7), the purity of ethanol and 2 - pentanone has a slight increase.

[0048] 3. Influence of operating conditions: Changes in operating conditions such as the number of theoretical plates, feed temperature, reboiler temperature, reflux ratio, solvent - feed ratio, and operating pressure will affect the yield and purity of the product. For example, in Example 1, the number of theoretical plates of the extractive distillation column T101 is 60, the reflux ratio is 0.2, and the solvent - feed ratio is 0.4:1; in Example 3, the number of theoretical plates is 45, the reflux ratio is 0.5, and the solvent - feed ratio is 0.8:1. Under different combinations of operating conditions, the yields and purities of ethanol and 2 - pentanone are different. Generally, increasing the number of theoretical plates, raising the solvent - feed ratio, and appropriately adjusting the reflux ratio are beneficial to improving the purity and yield of the product, but at the same time, it will increase the equipment cost and energy consumption, which needs to be considered comprehensively.

[0049] The embodiments of the present invention are given for purposes of illustration and description, and are not exhaustive or limit the invention to the disclosed form. Many modifications and variations are obvious to those of ordinary skill in the art. The embodiments are chosen and described in order to better explain the principles of the invention and its practical application, and to enable those of ordinary skill in the art to understand the invention so as to design various embodiments with various modifications suitable for specific purposes.

Claims

1. A method for separating an ethanol-2-pentanone azeotropic system by extractive distillation, characterized in that: The solvent used is a low eutectic solvent, comprising the following steps: The raw material to be separated is an ethanol-2-pentanone mixture; The hydrogen bond acceptor and the hydrogen bond donor are mixed and stirred at a certain ratio and temperature to obtain a deep eutectic solvent; First, the material to be separated S01 is heated by heat exchanger E101 and enters the middle part of tower T101. The low eutectic solvent stream S02 is adjusted to a suitable temperature and enters the upper part of tower T101. After heat exchange, part of the stream S05 of the top ethanol stream S03 refluxes to the top of the tower. The ethanol stream S04 with a purity of ≥99.5% is collected as the product. The stream S06 rich in low eutectic solvent and 2-pentanone in the bottom of the tower is recycled by heat exchanger E104 and enters the middle part of solvent recovery tower T102. Logistics S06 enters the solvent recovery tower T102 from the middle, and the light component 2-pentanone logistics S07 with a purity of ≥99.5% is obtained at the top of the tower. The cleanly resolved low eutectic solvent logistics S08 is obtained at the bottom of the tower and enters E101 to recover heat and then be recycled.

2. The method for separating an ethanol-2-pentanone azeotropic system by extractive distillation according to claim 1, characterized in that: The acceptor of the low eutectic solvent is tetramethylammonium chloride, the donor is ethylene glycol or urea or acetamide, and the mass ratio of the acceptor to the donor is 1:2-8.

3. The method for separating an ethanol-2-pentanone azeotropic system by extractive distillation according to claim 1, characterized in that: The operating conditions of the extractive distillation tower T101 are as follows: the theoretical number of plates is 20 to 60, the feed temperature of the separated stream S01 is 30 to 60°C, the bottom temperature is 70 to 120°C, the top temperature is 55 to 80°C, the reflux ratio is 0.1 to 0.9, the agent-to-material ratio is 0.4 to 0.8:1, and the operating pressure is 105 to 210 kPa.

4. The method for separating an ethanol-2-pentanone azeotropic system by extractive distillation according to claim 1, characterized in that: The operating conditions of the solvent recovery tower T102 are: the theoretical number of plates is 10 to 20, the bottom temperature is 100 to 130°C, the top temperature is 60 to 95°C, the reflux ratio is 0.1 to 1.2, and the operating pressure is 105 to 200 kPa.

5. The method for separating an ethanol-2-pentanone azeotropic system by extractive distillation according to claim 1, characterized in that: The content range of ethanol and 2-pentanone in the mixed material is not limited, and the method is applicable to ethanol-2-pentanone azeotropic mixtures with different contents.

6. The method for separating an ethanol-2-pentanone azeotropic system by extractive distillation according to claim 1, characterized in that: The low eutectic solvent is recycled by flash evaporation during use.

7. The method for separating an ethanol-2-pentanone azeotropic system by extractive distillation according to claim 1, characterized in that: In the extractive distillation process, the low eutectic solvent increases the relative volatility of the components inside the ethanol-2-pentanone azeotropic system.

8. The method for separating an ethanol-2-pentanone azeotropic system by extractive distillation according to claim 1, characterized in that: The yields of ethanol and 2-pentanone finally obtained by the method are both above 99%, and the purities are both above 99.5% (mass percentage).

9. The method for separating an ethanol-2-pentanone azeotropic system by extractive distillation according to claim 1, characterized in that: The heat exchangers E101, E102, E103, and E104 are used to realize heat recovery and utilization, so as to reduce the energy consumption of the entire process.

10. The method for separating ethanol-2-pentanone azeotropic system by extractive distillation according to claim 1, characterized in that: Compared with conventional solvents, the low eutectic solvent has the characteristics of strong selectivity, high solubility, low volatility and low agent-to-material ratio.

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