Method for separating isopropanol-ethyl acetate-isopropyl acetate-water azeotropic system through extractive distillation

Abstract

The invention provides a method for separating an isopropyl alcohol-ethyl acetate-isopropyl acetate-water azeotropic system through extractive distillation, and relates to the technical field of chemical separation, the used composite solvent is a mixture of 75-80% by mass of 1, 3-butanediol, 10-20% by mass of cyclopentanol and 10-20% by mass of ethylene carbonate, and the cyclopentanol and the ethylene carbonate are mixed to obtain the isopropyl alcohol-ethyl acetate-isopropyl acetate-water azeotropic system. The mass percentage content of cyclopentanol is 8%-15%, the mass percentage content of ethylene carbonate is 5%-10%, the catalyst is used for performing extractive distillation separation operation on a mixture of isopropanol, ethyl acetate, isopropyl acetate and water, the yields of isopropanol, ethyl acetate and isopropyl acetate can all reach 98% or above, and the catalyst is suitable for industrial production. The purity of the four products (including water) can reach more than 99.3% (mass percent), high-quality products can be provided for industrial production, strict requirements of various fields on the purity and yield of the organic solvents are met, the utilization rate of raw materials is greatly improved, and resource waste is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical separation, and more specifically, particularly relates to a method for extractive distillation to separate an isopropanol - ethyl acetate - isopropyl acetate - water azeotropic system. Background Art

[0002] In modern industrial production, isopropanol, ethyl acetate, and isopropyl acetate, as important organic solvents, are widely used in many fields such as chip manufacturing, coatings, pharmaceuticals, and chemical synthesis. During processes such as chip etching, a large amount of waste liquid containing isopropanol, ethyl acetate, isopropyl acetate, and water is generated, and it often contains a small amount of polymers and solid impurities. These substances form multiple azeotropic pairs under normal pressure, such as isopropanol - water, ethyl acetate - water, isopropyl acetate - water, isopropanol - ethyl acetate, and isopropanol - isopropyl acetate. The azeotropic temperatures are extremely close, all in the range of 70 - 80 °C, and their specific azeotropic compositions are complex and interrelated, making it extremely challenging to achieve effective separation through conventional distillation or a single special distillation method.

[0003] Traditional azeotropic distillation can handle azeotropic mixtures, but there are problems such as limited selection of the third component, high energy consumption, and poor operation flexibility. In contrast, extractive distillation has become a research hotspot due to the relatively wide range of extractant selection, low energy consumption, and easy operation regulation. However, for this quaternary azeotropic system, due to the complex azeotropic phenomenon, the screening of extractants and the design of extraction processes have significantly increased in difficulty. Although there have been studies using dimethyl sulfoxide, polyethylene glycol, or glycerol, etc. as extractants to separate related binary or ternary mixtures in the past, when dealing with the isopropanol - ethyl acetate - isopropyl acetate - water azeotropic system, it still cannot meet the comprehensive requirements of high - efficiency separation, high product yield and purity, low solvent consumption, and low energy consumption. Summary of the Invention

[0004] In order to solve the above - mentioned technical problems, the present invention provides a method for extractive distillation to separate an isopropanol - ethyl acetate - isopropyl acetate - water azeotropic system to solve the above problems.

[0005] A method for extractive distillation to separate an isopropanol - ethyl acetate - isopropyl acetate - water azeotropic system, wherein the composite solvent used is a mixture of 1,3 - butanediol, cyclopentanol, and ethylene carbonate. The mass percentage content of 1,3 - butanediol is between 75% and 80%, the mass percentage content of cyclopentanol is between 8% and 15%, and the mass percentage content of ethylene carbonate is between 5% and 10%. It is used for the extractive distillation separation operation of a mixture of isopropanol, ethyl acetate, isopropyl acetate, and water.

[0006] Preferably, the mass percentages of each component in the raw material to be separated are 17.2% isopropanol, 28.7% ethyl acetate, 16.9% isopropyl acetate, and 37.2% water. First, the material flow S01 to be separated enters the middle and lower part of the first extractive distillation column through a raw material preheater, and the composite solvent flow S02 enters the upper part of the column after being adjusted to a suitable temperature through a heat exchanger. A mixed flow S03 of ethyl acetate and isopropyl acetate is obtained at the top of the column, and a flow S04 rich in isopropanol, water, and composite solvent from which ethyl acetate and isopropyl acetate are removed is withdrawn from the bottom of the column. The number of theoretical plates of the first extractive distillation column is 50 - 100, the feeding temperature of the material flow S01 to be separated is 20 - 50 °C, the feeding temperature of the composite solvent S02 is 40 - 55 °C, the bottom temperature of the column is 110 - 150 °C, the top temperature of the column is 70 - 87 °C, the reflux ratio is 1.5 - 3.2, the ratio of the composite solvent to the material to be separated is 2.0 - 4.0:1 (mass ratio), and the operating pressure is 90 - 140 kPa. The flow S03 enters the ester separation column from the middle. An isopropyl acetate flow S06 is obtained at the bottom of the column, and a gaseous ethyl acetate flow S05 is obtained at the top of the column. After heat exchange with the material flow S01 to be separated, it enters the top gas condensate buffer tank and is then processed by a pump. Part of it is returned as reflux S09, and part of it is taken out as the ethyl acetate product flow S10. The number of theoretical plates of the ester separation column is 25 - 50, the top temperature of the column is 70 - 90 °C, the bottom temperature of the column is 80 - 115 °C, the reflux ratio is 1.3 - 7.3, and the operating pressure is 70 - 150 kPa. The flow S04 rich in isopropanol, water, and composite solvent enters the first solvent desorption column. The composite solvent flow S12 obtained at the bottom of the column is recycled after being adjusted in temperature through a heat exchanger, and a mixture flow S11 of isopropanol and water is obtained at the top of the column. The number of theoretical plates of the first solvent desorption column is 20 - 40, the top temperature of the column is 75 - 90 °C, the bottom temperature of the column is 180 - 210 °C, the reflux ratio is 1.5 - 2.7, and the operating pressure is 70 - 120 kPa.

[0007] Preferably, the mixture stream S11 of isopropanol and water enters the second extractive distillation column from the middle and lower part, and the composite solvent stream S13 enters from the middle and upper part. The isopropanol stream S14 is obtained at the top of the column, and the stream S15 of the composite solvent and water is obtained at the bottom of the column. The number of theoretical plates of the second extractive distillation column is 55 - 80, the feeding temperature of the composite solvent S13 is 38 - 50 °C, the top temperature of the column is 70 - 90 °C, the bottom temperature of the column is 140 - 184 °C, the reflux ratio is 1.7 - 2.4, the ratio of the composite solvent to the material to be separated is 2.0 - 5.0:1 (mass ratio), the operating pressure is 80 - 120 kPa. The stream S15 of the composite solvent and water directly enters the middle of the second solvent desorption column. The water stream S16 to be removed is obtained at the top of the column (which can be directly discharged), and the composite solvent stream S17 is obtained at the bottom of the column. After the temperature is adjusted by the heat exchanger, it is recycled to the feeding of the composite solvent in the middle and upper part of the second extractive distillation column. The number of theoretical plates of the second solvent desorption column is 18 - 45, the top temperature of the column is 70 - 110 °C, the bottom temperature of the column is 160 - 210 °C, the reflux ratio is 0.8 - 1.6, the operating pressure is 60 - 120 kPa. A supplementary solvent line S18 is set. When the solvent circulation amount of the extractive distillation system is low, fresh composite solvent is supplemented to the first and second extractive distillation columns through this supplementary solvent line S18, and the supplementary operation is carried out intermittently.

[0008] Preferably, the requirements for the content of each component of isopropanol, ethyl acetate, isopropyl acetate and water in the composite solvent are not strict, and it can be applied to quaternary mixtures of the above substances with different contents. Effective separation is achieved by appropriately adjusting the feeding amount of the composite solvent according to the organic matter content. The separated water can directly meet the national discharge standards or be used as process water, ensuring that the entire separation process meets environmental protection requirements and realizes the rational utilization of resources. Finally, the yields of isopropanol, ethyl acetate and isopropyl acetate can all reach more than 98%, and the purities of the four products can all reach more than 99.3% (mass percentage), achieving an efficient separation effect and meeting the strict requirements of industrial production for product quality and yield.

[0009] Compared with the prior art, the present invention has the following beneficial effects: High product yield and purity: By using a composite solvent composed of 1,3 - butanediol, cyclopentanol and ethylene carbonate in a specific ratio and combining with a carefully designed extractive distillation process, efficient separation of the isopropanol - ethyl acetate - isopropyl acetate - water azeotropic system is achieved. Verified by experiments, the yields of isopropanol, ethyl acetate and isopropyl acetate can all reach more than 98%, and the purities of the four products (including water) can all reach more than 99.3% (mass percentage), which can provide high - quality products for industrial production, meet the strict requirements of various fields for the purity and yield of these organic solvents, greatly improve the utilization rate of raw materials, and reduce resource waste.

[0010] Cost - benefit advantages: The composite solvent has a simple composition and is easy to obtain. Its raw materials have a wide range of supply sources and relatively low prices in the chemical market, effectively reducing the procurement cost of the solvent. At the same time, the composite solvent shows good extraction effects and high selectivity for each component to be separated, enabling a significant reduction in the agent - to - feed ratio during actual operation, reducing the circulation and usage amounts of the solvent, thereby lowering the operating cost of the entire separation process and the fixed investment in equipment, bringing significant economic benefits to the enterprise and enhancing its competitiveness in the market.

[0011] Strong process adaptability: The composite solvent of the present invention has relatively loose requirements for the content of each component of isopropyl alcohol, ethyl acetate, isopropyl acetate, and water, and can adapt to quaternary mixtures with different content compositions. In actual industrial production, in the face of fluctuations in the raw material composition, only the feed amount of the composite solvent needs to be appropriately adjusted according to the content of organic substances in the mixture to ensure stable and efficient separation effects, without the need for large - scale transformation or re - design of the entire process flow, demonstrating excellent process flexibility and adaptability, effectively reducing the operation difficulty and adjustment cost during production, and improving production efficiency.

[0012] Energy - saving and environmental - protection characteristics: In the process flow, by optimizing the recovery and utilization of the steam heat in the ester separation tower, efficient energy recycling is achieved, effectively reducing the operating energy consumption of the entire system, which is in line with the current development trend of energy conservation and emission reduction in the industrial field. In addition, the separated water can directly meet the national emission standards and can be directly discharged or recycled as process water, avoiding additional water treatment processes and costs, reducing environmental pollution, and realizing a green and environmentally friendly production process, with good social and environmental benefits. Description of the Drawings

[0013] Figure 1 is a schematic process flow diagram of the method of the present invention.

[0014] In the figure, the corresponding relationship between the component names and the drawing numbers is as follows: T101, the first extractive distillation tower; T102, the ester separation tower; T103, the first solvent desorption tower; T104, the second extractive distillation tower; T105, the second solvent desorption tower; E101, the raw material pre - heater; E102, the first composite solvent heat exchanger; E103, the second composite solvent heat exchanger; V101, the top - gas condensate buffer tank. Detailed Embodiments

[0015] The following further describes the embodiments of the present invention in detail with reference to the drawings and examples. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0016] Please refer to Figure 1, the present invention provides a method for separating the isopropanol-ethyl acetate-isopropyl acetate-water azeotropic system by extractive distillation. The composite solvent used is a mixture of 1,3-butanediol, cyclopentanol and ethylene carbonate, wherein the mass percentage content of 1,3-butanediol is between 75% and 80%, the mass percentage content of cyclopentanol is between 8% and 15%, and the mass percentage content of ethylene carbonate is between 5% and 10%. It is used for the extractive distillation separation operation of the mixture of isopropanol, ethyl acetate, isopropyl acetate and water.

[0017] The mass percentages of each component in the raw material to be separated are 17.2% isopropanol, 28.7% ethyl acetate, 16.9% isopropyl acetate, and 37.2% water. First, the material flow S01 to be separated enters the middle and lower part of the first extractive distillation column T101 through the raw material preheater, and the composite solvent flow S02 enters the upper part of the T101 column after being adjusted to a suitable temperature by the heat exchanger. A mixed flow S03 of ethyl acetate and isopropyl acetate is obtained at the top of the column, and a flow S04 rich in isopropanol, water and the composite solvent from which ethyl acetate and isopropyl acetate are removed is withdrawn from the bottom of the column. The number of theoretical plates of the first extractive distillation column T101 is 50 - 100, the feeding temperature of the material flow S01 to be separated is 20 - 50 °C, the feeding temperature of the composite solvent S02 is 40 - 55 °C, the bottom temperature of the column is 110 - 150 °C, the top temperature of the column is 70 - 87 °C, the reflux ratio is 1.5 - 3.2, the ratio of the composite solvent to the material to be separated is 2.0 - 4.0:1 (mass ratio), the operating pressure is 90 - 140 kPa. The flow S03 enters the ester separation column T102 from the middle. The isopropyl acetate flow S06 is obtained at the bottom of the column, and the gaseous ethyl acetate flow S05 is obtained at the top of the column. After being heat-exchanged with the material flow S01 to be separated, it enters the top gas condensate buffer tank, and then is processed by a pump. Part of it returns to T102 as reflux S09, and part of it is taken out as the ethyl acetate product flow S10. The number of theoretical plates of the ester separation column T102 is 25 - 50, the top temperature of the column is 70 - 90 °C, the bottom temperature of the column is 80 - 115 °C, the reflux ratio is 1.3 - 7.3, the operating pressure is 70 - 150 kPa. The flow S04 rich in isopropanol, water and the composite solvent from T101 enters the first solvent desorption column T103. The composite solvent flow S12 obtained at the bottom of the T103 column is recycled after being adjusted in temperature by the heat exchanger. A mixture flow S11 of isopropanol and water is obtained at the top of the T103 column. The number of theoretical plates of the first solvent desorption column T103 is 20 - 40, the top temperature of the column is 75 - 90 °C, the bottom temperature of the column is 180 - 210 °C, the reflux ratio is 1.5 - 2.7, the operating pressure is 70 - 120 kPa.

[0018] A mixture stream S11 of isopropanol and water enters the second extractive distillation column T104 from the middle lower part, and a composite solvent stream S13 enters T104 from the middle upper part. An isopropanol stream S14 is obtained at the top of the column, and a stream S15 of the composite solvent and water is obtained at the bottom of the column. The number of theoretical plates of the second extractive distillation column T104 is 55 - 80. The feed temperature of the composite solvent S13 is 38 - 50 °C, the top temperature of the column is 70 - 90 °C, the bottom temperature of the column is 140 - 184 °C, the reflux ratio is 1.7 - 2.4, the ratio of the composite solvent to the material to be separated is 2.0 - 5.0:1 (mass ratio), the operating pressure is 80 - 120 kPa. The stream S15 of the composite solvent and water directly enters the middle part of the second solvent desorption column T105. A water stream S16 to be removed (which can be directly discharged) is obtained at the top of the column, and a composite solvent stream S17 is obtained at the bottom of the column. After the temperature is adjusted by a heat exchanger, it is recycled to the composite solvent feed at the middle upper part of the second extractive distillation column T104. The number of theoretical plates of the second solvent desorption column T105 is 18 - 45, the top temperature of the column is 70 - 110 °C, the bottom temperature of the column is 160 - 210 °C, the reflux ratio is 0.8 - 1.6, the operating pressure is 60 - 120 kPa. A supplementary solvent line S18 is set. When the solvent circulation amount of the extractive distillation system is low, fresh composite solvent is supplemented to the first and second extractive distillation columns through this supplementary solvent line S18, and the supplementary operation is carried out intermittently.

[0019] The composite solvent has no strict requirements on the content of each component of isopropanol, ethyl acetate, isopropyl acetate and water, and can be applicable to quaternary mixtures with different contents of the above substances. Effective separation is achieved by appropriately adjusting the feed amount of the composite solvent according to the organic matter content. The separated water can directly meet the national emission standards or be used as process water, ensuring that the entire separation process meets environmental protection requirements and realizes the rational utilization of resources. Finally, the yields of isopropanol, ethyl acetate and isopropyl acetate can all reach more than 98%, and the purities of the four products can all reach more than 99.3% (mass percentage), achieving an efficient separation effect and meeting the strict requirements of industrial production for product quality and yield.

[0020] Working principle: The chip industry generates a large amount of waste liquid containing isopropanol, ethyl acetate, isopropyl acetate and water. After removing solids and polymers, the main components of this mixed waste liquid are isopropanol, ethyl acetate, isopropyl acetate and water, denoted as stream S01. First, the material stream S01 to be separated enters the middle and lower part of the first extractive distillation column T101 through the E101 raw material preheater; the composite solvent stream S02 enters the upper part of the T101 tower after being adjusted to a suitable temperature by the E102. A mixed stream S03 of ethyl acetate and isopropyl acetate is obtained at the top of the tower, and a stream S04 rich in isopropanol, water and composite solvent from which ethyl acetate and isopropyl acetate are removed is withdrawn from the bottom of the tower; the stream S03 enters the ester separation column T102 from the middle. The isopropyl acetate stream S06 is obtained at the bottom of the tower, and the gaseous ethyl acetate stream S05 is obtained at the top of the tower. After exchanging heat with the stream S01 to be separated through the E101, it enters the V101 top gas condensate buffer tank, and then through the P101, a part of it returns to the T102 as the reflux S09, and a part is taken out as the ethyl acetate product stream S10; the stream S04 rich in isopropanol, water and composite solvent from the T101 enters the first solvent desorption column T103. The composite solvent stream S12 obtained at the bottom of the T103 is adjusted in temperature by the first composite solvent heat exchanger E102 and then recycled; a mixture stream S11 of isopropanol and water is obtained at the top of the T103; the mixture stream S11 of isopropanol and water enters the second extractive distillation column T104 from the middle and lower part, and the composite solvent stream S13 enters the T104 from the middle and upper part. The isopropanol stream S14 is obtained at the top of the tower, and a stream S15 of composite solvent and water is obtained at the bottom of the tower; the stream S15 of composite solvent and water directly enters the middle part of the second solvent desorption column T105. The water stream S16 to be removed (which can be directly discharged) is obtained at the top of the tower, and the composite solvent stream S17 obtained at the bottom of the tower is adjusted in temperature by the second composite solvent heat exchanger E103 and then recycled to the composite solvent feed at the middle and upper part of the second extractive distillation column T104; when the solvent circulation amount in the extractive distillation system is low, it is supplemented through the supplementary solvent line S18.

[0021] Example: Example 1: According to Figure 1 the technological process, a mixture of 1,3 - butanediol, cyclopentanol and ethylene carbonate is used as the composite solvent, in which the mass percentage content of 1,3 - butanediol is: 80%, the mass percentage content of cyclopentanol is: 15%, and the mass percentage content of ethylene carbonate is: 5%.

[0022] The chip industry generates a large amount of waste liquid containing isopropanol, ethyl acetate, isopropyl acetate and water. After removing solids and polymers, the main components of this mixed waste liquid are isopropanol, ethyl acetate, isopropyl acetate and water, with isopropanol 17.2%, ethyl acetate 28.7%, isopropyl acetate 16.9%, and water 37.2%.

[0023] (1) First, the material stream S01 to be separated enters the 60th plate of the first extractive distillation column T101 (this column has 100 theoretical plates. Calculated from top to bottom, the topmost is the 1st plate, the same below) through the E101 raw material preheater; the composite solvent stream S02 enters the 5th plate of the T101 column after being adjusted to a suitable temperature by the E102. A mixed stream S03 of ethyl acetate and isopropyl acetate is obtained at the top of the column, and a stream S04 rich in isopropanol, water, and composite solvent with ethyl acetate and isopropyl acetate removed is withdrawn from the bottom of the column; (2) The stream S03 enters the ester separation column T102 (a total of 50 plates) from the 25th plate. The isopropyl acetate stream S06 with a purity ≥ 99.4% is obtained at the bottom of the column, and the gaseous ethyl acetate stream S05 with a purity ≥ 99.3% is obtained at the top of the column. After heat exchange with the stream S01 to be separated through the E101, it enters the V101 top gas condensate buffer tank, and then through the P101, part of it returns to the T102 as the reflux S09, and part of it is taken out as the ethyl acetate product stream S10 (purity ≥ 99.3%); (3) The stream S04 rich in isopropanol, water, and composite solvent from the T101 enters the 20th plate of the first solvent desorption column T103 (a total of 40 plates). The composite solvent stream S12 obtained at the bottom of the T103 column is recycled after adjusting the temperature by the first composite solvent heat exchanger E102; a mixture stream S11 of isopropanol and water is obtained at the top of the T103 column; (4) The mixture stream S11 of isopropanol and water enters the 50th plate of the second extractive distillation column T104 (a total of 80 plates) from the middle and lower part, and the composite solvent stream S13 enters the 5th plate of the T104 column from the middle and upper part. The isopropanol stream S14 with a purity ≥ 99.3% is obtained at the top of the column, and a stream S15 of composite solvent and water is obtained at the bottom of the column; (5) The stream S15 of composite solvent and water directly enters the 25th plate of the second solvent desorption column T105 (a total of 45 plates). The water stream S16 to be removed is obtained at the top of the column (which can be directly discharged or used as process water), and the composite solvent stream S17 obtained at the bottom of the column is recycled to the composite solvent feed at the middle and upper part of the second extractive distillation column T104 after adjusting the temperature by the second composite solvent heat exchanger E103; (6) When the amount of the composite solvent in the bottom of the T101 and T104 columns (the bottom liquid level is relatively low) is small, fresh composite solvent is supplemented through the stream S18.

[0024] In the above process, the operating conditions of each operation unit are as follows: (1) Operating conditions of the first extractive distillation column T101: The number of theoretical plates is 100, the feed temperature of the material stream S01 to be separated is 30 °C, the feed temperature of the composite solvent S02 is 40 °C, the bottom temperature is 132.5 °C, the top temperature is 80.8 °C, the reflux ratio is 2.7, the ratio of the composite solvent to the material to be separated is 4.0:1 (mass ratio), and the operating pressure is 101 kPa; (2) Operating conditions of the ester separation column T102: The number of theoretical plates is 50, the top temperature is 78.3 °C, the bottom temperature is 90.7 °C, the reflux ratio is 6, and the operating pressure is 105 kPa; (3) Operating conditions of the first solvent desorption column T103: The number of theoretical plates is 40, the top temperature is 81.3 °C, the bottom temperature is 191.9 °C, the reflux ratio is 2.7, and the operating pressure is 105 kPa; (4) Operating conditions of the second extractive distillation column T104: The number of theoretical plates is 80, the feeding temperature of the composite solvent S13 is 38 °C, the top temperature is 83.2 °C, the bottom temperature is 160.4 °C, the reflux ratio is 2.4, the ratio of the composite solvent to the material to be separated is 4.0:1 (mass ratio), and the operating pressure is 105 kPa; (5) Operating conditions of the second solvent desorption column T105: The number of theoretical plates is 45, the top temperature is 90.9 °C, the bottom temperature is 191.2 °C, the reflux ratio is 1.6, and the operating pressure is 80 kPa; (6) The fresh composite solvent stream S18 is supplemented to supply solvents to the first and second extractive distillation columns, and it is an intermittent operation.

[0025] Combined with Figure 1 the process, the isopropanol yield is 98.10% and the purity is 99.32% (mass percentage, the same below); the yield of ethyl acetate is 98.22% and the purity is 99.37%; the yield of isopropyl acetate is 98.31% and the purity is 99.63%.

[0026]

[0027] Example 2: According to Figure 1 the process flow, a mixture of 1,3 - butanediol, cyclopentanol and ethylene carbonate is used as the composite solvent, in which the mass percentage content of 1,3 - butanediol is: 75%, the mass percentage content of cyclopentanol is: 15%, and the mass percentage content of ethylene carbonate is: 10%.

[0028] The chip industry generates a large amount of waste liquid containing isopropanol, ethyl acetate, isopropyl acetate and water. After removing solids and polymers. The main components of this mixed waste liquid are isopropanol, ethyl acetate, isopropyl acetate and water, with isopropanol 32.8%, ethyl acetate 19.1%, isopropyl acetate 30.4%, and water 17.7%.

[0029] (1) First, the material stream S01 to be separated enters the 55th plate of the first extractive distillation column T101 through the E101 raw material preheater (this column has 80 theoretical plates. Calculated from top to bottom, the topmost is the 1st plate, and the same applies hereinafter); the composite solvent stream S02 enters the 6th plate of the T101 column after being adjusted to an appropriate temperature by the E102. A mixed stream S03 of ethyl acetate and isopropyl acetate is obtained at the top of the column, and a stream S04 rich in isopropanol, water, and composite solvent from which ethyl acetate and isopropyl acetate have been removed is withdrawn from the bottom of the column; (2) The stream S03 enters the ester separation column T102 (with a total of 40 plates) from the 25th plate. An isopropyl acetate stream S06 with a purity ≥ 99.5% is obtained at the bottom of the column, and a gaseous ethyl acetate stream S05 with a purity ≥ 99.4% is obtained at the top of the column. After heat exchange with the stream S01 to be separated through the E101, it enters the V101 top gas condensate buffer tank, and then through the P101, a part of it returns to the T102 as the reflux S09, and a part is withdrawn as the ethyl acetate product stream S10 (purity ≥ 99.4%); (3) The stream S04 rich in isopropanol, water, and composite solvent from the T101 enters the 20th plate (with a total of 35 plates) of the first solvent desorption column T103. The composite solvent stream S12 obtained at the bottom of the T103 column is recycled after being adjusted in temperature by the first composite solvent heat exchanger E102; a mixture stream S11 of isopropanol and water is obtained at the top of the T103 column; (4) The mixture stream S11 of isopropanol and water enters the 45th plate (with a total of 70 plates) of the second extractive distillation column T104 from the middle and lower part, and the composite solvent stream S13 enters the 6th plate of the T104 from the middle and upper part. An isopropanol stream S14 with a purity ≥ 99.4% is obtained at the top of the column, and a stream S15 of composite solvent and water is obtained at the bottom of the column; (5) The stream S15 of composite solvent and water directly enters the 20th plate (with a total of 40 plates) of the second solvent desorption column T105. A water stream S16 to be removed (which can be directly discharged or used as process water) is obtained at the top of the column, and the composite solvent stream S17 obtained at the bottom of the column is recycled to the composite solvent feed at the middle and upper part of the second extractive distillation column T104 after being adjusted in temperature by the second composite solvent heat exchanger E103; (6) When the amount of the composite solvent in the bottom of the T101 and T104 columns (the bottom liquid level is relatively low) is small, fresh composite solvent is supplemented through the stream S18.

[0030] In the above process, the operating conditions of each operating unit are as follows: (1) Operating conditions of the first extractive distillation column T101: The number of theoretical plates is 80, the feed temperature of the stream S01 to be separated is 35 °C, the feed temperature of the composite solvent S02 is 55 °C, the bottom temperature is 127.3 °C, the top temperature is 73.2 °C, the reflux ratio is 2.4, the ratio of the composite solvent to the material to be separated is 3.5:1 (mass ratio), and the operating pressure is 90 kPa; (2) Operating conditions of the ester separation column T102: The number of theoretical plates is 40, the top temperature is 66.4 °C, the bottom temperature is 78.9 °C, the reflux ratio is 5.2, and the operating pressure is 70 kPa; (3) Operating conditions of the first solvent desorption column T103: The number of theoretical plates is 35, the top temperature is 69.6 °C, the bottom temperature is 183.3 °C, the reflux ratio is 1.9, and the operating pressure is 80 kPa; (4) Operating conditions of the second extractive distillation column T104: The number of theoretical plates is 70, the feeding temperature of the composite solvent S13 is 45 °C, the top temperature is 75.8 °C, the bottom temperature is 155.3 °C, the reflux ratio is 2.0, the ratio of the composite solvent to the material to be separated is 4.2:1 (mass ratio), and the operating pressure is 90 kPa; (5) Operating conditions of the second solvent desorption column T105: The number of theoretical plates is 40, the top temperature is 83.4 °C, the bottom temperature is 182.6 °C, the reflux ratio is 1.4, and the operating pressure is 60 kPa; Combined with Figure 1 the process, the isopropanol yield is 98.27% and the purity is 99.43% (mass percentage, the same below); the ethyl acetate yield is 98.35% and the purity is 99.41%; the isopropyl acetate yield is 98.49% and the purity is 99.56%.

[0031]

[0032] Example 3: According to Figure 1 the process flow, a mixture of 1,3-butanediol, cyclopentanol and ethylene carbonate is used as the composite solvent, in which the mass percentage content of 1,3-butanediol is: 78%, the mass percentage content of cyclopentanol is: 15%, and the mass percentage content of ethylene carbonate is: 7%.

[0033] The chip industry generates a large amount of waste liquid containing isopropanol, ethyl acetate, isopropyl acetate and water. After removing solids and polymers. The main components of this mixed waste liquid are isopropanol, ethyl acetate, isopropyl acetate and water, with isopropanol 10.1%, ethyl acetate 32.9%, isopropyl acetate 14.2%, and water 42.8%.

[0034] (1) First, the material stream S01 to be separated enters the 70th plate of the first extractive distillation column T101 through the E101 raw material preheater (this column has 90 theoretical plates. Calculated from top to bottom, the topmost is the 1st plate, the same below); the composite solvent stream S02 is adjusted to the appropriate temperature through E102 and then enters the 8th plate of the T101 column. The mixed stream S03 of ethyl acetate and isopropyl acetate is obtained at the top of the column, and the stream S04 rich in isopropanol, water and composite solvent after removing ethyl acetate and isopropyl acetate is withdrawn from the bottom of the column; (2) The logistics S03 enters the ester separation column T102 (with a total of 45 trays) from 25 trays. The isopropyl acetate logistics S06 with a purity ≥ 99.3% is obtained at the bottom of the column, and the ethyl acetate vapor logistics S05 with a purity ≥ 99.3% is obtained at the top of the column. After heat exchange with the logistics S01 to be separated through E101, it enters the overhead vapor condensate buffer tank V101, and then through P101, a part returns to T102 as reflux S09, and a part is taken out as the ethyl acetate product logistics S10 (purity ≥ 99.3%); (3) The logistics S04 rich in isopropanol, water and composite solvent enters the 15th tray (a total of 30 trays) of the first solvent desorption column T103. The composite solvent logistics S12 obtained at the bottom of T103 is adjusted in temperature through the first composite solvent heat exchanger E102 and then recycled; The mixture logistics S11 of isopropanol and water is obtained at the top of T103; (4) The mixture logistics S11 of isopropanol and water enters the 60th tray (a total of 75 trays) of the second extractive distillation column T104 from the middle and lower part, and the composite solvent logistics S13 enters the 8th tray of T104 from the middle and upper part. The isopropanol logistics S14 with a purity ≥ 99.3% is obtained at the top of the column, and the logistics S15 of composite solvent and water is obtained at the bottom of the column; (5) The logistics S15 of composite solvent and water directly enters the 15th tray (a total of 30 trays) of the second solvent desorption column T105. The water logistics S16 to be removed (which can be directly discharged or used as process water) is obtained at the top of the column, and the composite solvent logistics S17 obtained at the bottom of the column is adjusted in temperature through the second composite solvent heat exchanger E103 and then recycled to the middle and upper part of the second extractive distillation column T104 as the composite solvent feed; (6) When the amount of composite solvent in the bottom of T101 and T104 (the bottom liquid level is relatively low) is small, fresh composite solvent is supplemented through the logistics S18.

[0035] In the above process, the operating conditions of each operation unit are as follows: (1) Operating conditions of the first extractive distillation column T101: The number of theoretical trays is 90, the feed temperature of the logistics S01 to be separated is 40 °C, the feed temperature of the composite solvent S02 is 50 °C, the bottom temperature of the column is 141.1 °C, the top temperature of the column is 78.8 °C, the reflux ratio is 3.0, the ratio of composite solvent to the material to be separated is 3.2:1 (mass ratio), and the operating pressure is 110 kPa; (2) Operating conditions of the ester separation column T102: The number of theoretical trays is 45, the top temperature of the column is 87.4 °C, the bottom temperature of the column is 99.8 °C, the reflux ratio is 5.9, and the operating pressure is 140 kPa; (3) Operating conditions of the first solvent desorption column T103: The number of theoretical trays is 30, the top temperature of the column is 66.3 °C, the bottom temperature of the column is 179.2 °C, the reflux ratio is 2.3, and the operating pressure is 70 kPa; (4) Operating conditions of the second extractive distillation column T104: The number of theoretical plates is 75, the feeding temperature of the composite solvent S13 is 42 °C, the top temperature of the column is 72.7 °C, the bottom temperature of the column is 151.6 °C, the reflux ratio is 2.3, the ratio of the composite solvent to the material to be separated is 3.9:1 (mass ratio), and the operating pressure is 80 kPa; (5) Operating conditions of the second solvent desorption column T105: The number of theoretical plates is 30, the top temperature of the column is 93.9 °C, the bottom temperature of the column is 194.9 °C, the reflux ratio is 1.5, and the operating pressure is 90 kPa; Combined with Figure 1 process, the yield of isopropanol is 98.84% and the purity is 99.36% (mass percentage, the same below); the yield of ethyl acetate is 98.91% and the purity is 99.33%; the yield of isopropyl acetate is 99.06% and the purity is 99.31%.

[0036]

[0037] The embodiments of the present invention are given for purposes of illustration and description, and are not intended to be exhaustive or to 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 illustrate the principles of the invention and its practical application, and to enable those of ordinary skill in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for separating an isopropanol-ethyl acetate-isopropyl acetate-water azeotropic system by extractive distillation, characterized in that, The composite solvent used is a mixture of 1,3-butanediol, cyclopentanol and ethylene carbonate, wherein the mass percentage content of 1,3-butanediol is between 75% and 80%, the mass percentage content of cyclopentanol is between 8% and 15%, and the mass percentage content of ethylene carbonate is between 5% and 10%. It is used for extractive distillation separation operation of the mixture of isopropanol, ethyl acetate, isopropyl acetate and water.

2. The method according to claim 1, wherein The mass percentages of each component in the raw material to be separated are 17.2% isopropanol, 28.7% ethyl acetate, 16.9% isopropyl acetate, and 37.2% water. First, the material flow S01 to be separated enters the middle and lower part of the first extractive distillation column (T101) through the raw material preheater, and the composite solvent flow S02 enters the upper part of the column (T101) after being adjusted to a suitable temperature through the heat exchanger. The mixed flow S03 of ethyl acetate and isopropyl acetate is obtained at the top of the column, and the flow S04 rich in isopropanol, water and composite solvent after removing ethyl acetate and isopropyl acetate is withdrawn from the bottom of the column. The number of theoretical plates of the first extractive distillation column (T101) is 50 - 100, the feeding temperature of the material flow S01 to be separated is 20 - 50 °C, the feeding temperature of the composite solvent S02 is 40 - 55 °C, the bottom temperature of the column is 110 - 150 °C, the top temperature of the column is 70 - 87 °C, the reflux ratio is 1.5 - 3.2, the ratio of the composite solvent to the material to be separated is 2.0 - 4.0:1 (mass ratio), and the operating pressure is 90 - 140 kPa.

3. The method according to claim 2, wherein The flow S03 enters the ester separation column (T102) from the middle. The isopropyl acetate flow S06 is obtained at the bottom of the column, and the gaseous ethyl acetate flow S05 is obtained at the top of the column. After heat exchange with the material flow S01 to be separated, it enters the top gas condensate buffer tank, and then after being processed by the pump, part of it returns to (T102) as the reflux S09, and part of it is taken out as the ethyl acetate product flow S10. The number of theoretical plates of the ester separation column (T102) is 25 - 50, the top temperature of the column is 70 - 90 °C, the bottom temperature of the column is 80 - 115 °C, the reflux ratio is 1.3 - 7.3, and the operating pressure is 70 - 150 kPa.

4. The method according to claim 2, wherein The flow S04 rich in isopropanol, water and composite solvent from (T101) enters the first solvent desorption column (T103). The composite solvent flow S12 obtained at the bottom of the column (T103) is recycled after being adjusted in temperature through the heat exchanger. The mixture flow S11 of isopropanol and water is obtained at the top of the column (T103). The number of theoretical plates of the first solvent desorption column (T103) is 20 - 40, the top temperature of the column is 75 - 90 °C, the bottom temperature of the column is 180 - 210 °C, the reflux ratio is 1.5 - 2.7, and the operating pressure is 70 - 120 kPa.

5. The method according to claim 4, wherein The mixture stream S11 of isopropanol and water enters the second extractive distillation column (T104) from the middle and lower part, and the composite solvent stream S13 enters (T104) from the middle and upper part. The isopropanol stream S14 is obtained at the top of the column, and the stream S15 of the composite solvent and water is obtained at the bottom of the column. The number of theoretical plates of the second extractive distillation column (T104) is 55 - 80, the feeding temperature of the composite solvent S13 is 38 - 50 °C, the top temperature of the column is 70 - 90 °C, the bottom temperature of the column is 140 - 184 °C, the reflux ratio is 1.7 - 2.4, the ratio of the composite solvent to the material to be separated is 2.0 - 5.0:1 (mass ratio), and the operating pressure is 80 - 120 kPa.

6. The method according to claim 5, characterized in that, The stream S15 of the composite solvent and water directly enters the middle part of the second solvent desorption column (T105). The water stream S16 to be removed is obtained at the top of the column (which can be directly discharged), and the composite solvent stream S17 is obtained at the bottom of the column. After the temperature is adjusted by the heat exchanger, it is recycled to the feeding of the composite solvent in the middle and upper part of the second extractive distillation column (T104). The number of theoretical plates of the second solvent desorption column (T105) is 18 - 45, the top temperature of the column is 70 - 110 °C, the bottom temperature of the column is 160 - 210 °C, the reflux ratio is 0.8 - 1.6, and the operating pressure is 60 - 120 kPa.

7. The method according to claim 1, wherein A supplementary solvent line S18 is set. When the solvent circulation amount of the extractive distillation system is low, fresh composite solvent is supplemented to the first and second extractive distillation columns through this supplementary solvent line S18, and the supplementary operation is carried out intermittently.

8. The method according to claim 1, characterized in that The requirements for the content of each component of the composite solvent, such as isopropanol, ethyl acetate, isopropyl acetate, and water, are not strict, and it can be applied to quaternary mixtures with different contents of the above substances. Effective separation is achieved by appropriately adjusting the feeding amount of the composite solvent according to the content of organic substances.

9. The method according to claim 1, characterized in that, The separated water can directly meet the national emission standards or be used as process water, ensuring that the entire separation process meets the environmental protection requirements and realizes the rational utilization of resources.

10. The method according to any one of claims 1-9, characterized in that, Finally, the yields of isopropanol, ethyl acetate, and isopropyl acetate can all reach over 98%, and the purities of the four products can all reach over 99.3% (mass percentage), achieving an efficient separation effect and meeting the strict requirements of industrial production for product quality and yield.

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