Method for separating tert-butyl alcohol-ethanol-water mixture through extractive distillation by using eutectic solvent

Abstract

The invention provides a device and a method for extracting, rectifying and separating a tert-butyl alcohol-ethanol-water mixture by using a deep eutectic solvent, and belongs to the technical field of extraction and separation. The deep eutectic solvent composed of glucose, choline chloride and ethylene glycol is adopted as the extraction agent, after extractive distillation separation, the purity of ethyl alcohol, tert-butyl alcohol and the extraction agent reaches up to 99.0-99.9%, the purity of water can reach 99.5-99.9%, the purity of the extraction agent can reach 99.5% or above, and cyclic utilization of the extraction agent can be achieved. Compared with a traditional solvent, the energy consumption of the deep eutectic solvent extractive distillation process is lower.

Description

Technical Field

[0001] The invention relates to the technical field of extraction and separation, and in particular to a device and a method for separating a tert-butyl alcohol-ethanol-water mixture by extraction and distillation of a low eutectic solvent. Background Art

[0002] Tert-butyl alcohol and ethanol are very important organic chemical raw materials. In the production process of ethyl tert-butyl ether, a large amount of wastewater containing tert-butyl alcohol and ethanol will be generated due to the occurrence of side reactions. In order to reduce the discharge of wastewater and recover tert-butyl alcohol and ethanol in the wastewater, the separation and recovery of tert-butyl alcohol and ethanol in the wastewater has become an important link in the production of ethyl tert-butyl ether.

[0003] However, ethanol, tert-butanol and water form azeotropes under normal pressure. Ethanol and water azeotropes at 78.2°C, and the azeotropic composition is 89.4% (molar fraction, the same below) of ethanol and 10.6% of water; tert-butanol and water azeotropes at 80.03°C, and the azeotropic composition is 37.02% (molar fraction, the same below) of water and 62.98% of tert-butanol. It is difficult to separate the mixture using traditional distillation methods. Azeotropic distillation and extractive distillation are commonly used in industry to separate alcohol-water azeotropic systems. Azeotropic distillation often has the problems of complex process and high cost, while extractive distillation has become the research focus of alcohol-water azeotrope separation due to its simple process.

[0004] In extractive distillation, the selection of extractants is the key to the extractive distillation separation process. In the separation of alcohol-water azeotropes, commonly used extractants include traditional organic solvents (such as glycerol, ethylene glycol, etc.), salt-added extractants, ionic liquids, etc. Traditional organic solvents often have problems such as high energy consumption, high toxicity or strong corrosiveness. In recent decades, ionic liquids have attracted widespread attention as extractants due to their good thermal stability, low vapor pressure, and high selectivity for solutes. However, ionic liquids are limited in their large-scale application due to their high cost, difficulty in synthesis, and poor biodegradability. Therefore, finding a new green extractant suitable for the separation of alcohol-water azeotropes has become a research hotspot for the separation of tert-butanol-ethanol-water azeotropes by extractive distillation. Furthermore, the energy consumption of conventional extractive distillation is often high. In order to reduce energy consumption, it is urgent to design a low-energy device to separate tert-butanol, ethanol and water. Summary of the invention

[0005] The technical solution of the present invention is achieved in this way: The present invention provides a device and method for separating tert-butyl alcohol-ethanol-water mixture by extractive distillation with a low eutectic solvent, the device comprising two extractive distillation towers with side lines, a solvent recovery tower, and an extractant cooler. The device comprises the following steps: (1) The tert-butyl alcohol-ethanol-water mixture and the first extractant enter the extractive distillation tower from the middle and lower parts and the upper parts of the first side-line extractive distillation tower respectively, high-purity tert-butyl alcohol is extracted from the top of the extractive distillation tower, the first extractant is extracted from the bottom of the tower, and a mixture containing ethanol, water and the extractant is extracted from the side line; (2) the water, ethanol, the second extractant mixture and the extractant extracted from the side line in step (1) are introduced into a second extractive distillation tower, respectively, high-purity ethanol is extracted from the top of the tower, the second extractant is extracted from the bottom of the tower, and the mixture containing water and the extractant is extracted from the side line; (3) The water and extractant mixture extracted from the side line in step (2) is introduced into an extractant recovery tower to obtain high-purity water at the top of the tower and high-purity extractant in the bottom of the tower, and the extractant is cooled and introduced into an extractive distillation tower for recycling.

[0006] As a further improvement of the present invention, in step (1), the first extractant is a low eutectic solvent composed of glucose, choline chloride and ethylene glycol in a molar ratio of 1:1-3:2-3.

[0007] As a further improvement of the present invention, the first extractant is a low eutectic solvent composed of glucose, choline chloride and ethylene glycol in a molar ratio of 1:2:2.5.

[0008] As a further improvement of the present invention, in step (1), the number of plates of the first extractive distillation tower is 20-50, the molar reflux ratio is 1.0-3.0, the operating conditions are normal pressure, the tower top temperature is 81°C-83°C, the molar ratio of the solvent is 0.5-3, and the side line extraction position is 14-35 tower plates.

[0009] As a further improvement of the present invention, in step (1), the first extractant is fed to the 3rd to 13th tray, and the water-ethanol-tert-butanol is fed to the 12th to 40th tray.

[0010] As a further improvement of the present invention, in step (2), the second extractant is a low eutectic solvent composed of choline chloride and ethylene glycol in a molar ratio of 1:1-3.

[0011] As a further improvement of the present invention, the second extractant is a low eutectic solvent composed of choline chloride and ethylene glycol in a molar ratio of 1:2.

[0012] As a further improvement of the present invention, in step (2), the number of plates of the second extractive distillation tower is 30-55, the molar reflux ratio is 1.5-5.0, the operating conditions are normal pressure, the top operating temperature is 77.5-79.0°C, the molar ratio of the solvent is 1-3, and the side line extraction position is the 23rd to 42nd tower plate.

[0013] As a further improvement of the present invention, in step (2), the feeding position of the second extractant is the 3rd to 10th tower plates, and the feeding position of water-ethanol-tert-butanol is the 22nd to 45th tower plates.

[0014] As a further improvement of the present invention, the number of plates of the extractant recovery tower in step (3) is 10-35, the molar reflux ratio is 0.1-1.0, the operating pressure is atmospheric pressure; the tower top operating temperature is 99-101° C., and the raw material feeding position is the 10th to 26th tower plate.

[0015] The present invention has the following beneficial effects: the present invention uses a low eutectic solvent composed of glucose, choline chloride and ethylene glycol as an extractant to separate wastewater containing tert-butanol and ethanol to obtain high-purity ethanol, isobutanol products and high-purity water. The added glucose is a polyhydroxy structure, has a strong affinity for n-butanol and ethanol, and can quickly separate n-butanol and ethanol. The method of the present invention has a simple process flow and is easy to operate. The extractant used has the advantages of being non-toxic, pollution-free, easy to recover and recyclable, and can effectively reduce production costs. The purity and yield of ethanol and tert-butanol obtained by the technical method of the present invention are both greater than 99%, and the purity of water can reach more than 99.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0017] Figure 1 The present invention is a process flow chart of the method for separating tert-butyl alcohol-ethanol-water mixture by extractive distillation of a low eutectic solvent. DETAILED DESCRIPTION

[0018] 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.

[0019] Example 1 like Figure 1 This embodiment provides a method for separating a tert-butyl alcohol-ethanol-water mixture by extractive distillation using a deep eutectic solvent, comprising the following steps: (1) The feed flow rate of the raw material is 100 kmol / h, the temperature is 25°C, the pressure is 1 atm, the feed contains 25 mol% of tert-butanol, 25 mol% of ethanol, 50 mol% of water, and the flow rate of the first extractant is 30 kmol / h. The raw material and the first extractant enter the extractive distillation tower from the middle and lower parts and the upper part of the first side-line extractive distillation tower respectively. High-purity tert-butanol is extracted from the top of the extractive distillation tower at an extraction rate of 24.9 kmol / h, the extractant is extracted from the bottom of the tower, and a mixture of water, ethanol and extractant is extracted from the side line at an extraction rate of 93 kmol / h; The first extractant is a deep eutectic solvent composed of glucose, choline chloride and ethylene glycol in a molar ratio of 1:2:2; The first extractive distillation tower has 20 plates, a molar reflux ratio of 1.0, an operating condition of normal pressure, a tower top temperature of 81.8°C, and a solvent ratio (molar ratio) of 0.5; the feed position of the first extractant is the third plate, the feed position of water-ethanol-tert-butanol is the 12th plate, and the side line extraction position is the 15th plate.

[0020] (2) The water, ethanol and extractant mixture and the second extractant extracted from the side line in step (1) are introduced into a second side line extractive distillation tower, respectively, and high-purity ethanol is extracted from the top of the tower at a rate of 25.1 kmol / h, the second extractant is extracted from the bottom of the tower, and a mixture containing water and the extractant is extracted from the side line at a rate of 66 kmol / h.

[0021] The second extractant is a low eutectic solvent composed of glucose, choline chloride and ethylene glycol in a molar ratio of 1:2:2, and the flow rate of the extractant is 20 kmol / h; The second extractive distillation tower has 30 plates, a molar reflux ratio of 1.5, an operating condition of normal pressure, and a tower top temperature of 78.0°C; the feed position of the second extractant is the 3rd plate, the feed position of water-ethanol-tert-butanol is the 22nd plate, and the side line extraction position is the 25th plate.

[0022] (3) The mixture of water and extractant obtained in step (2) is introduced into an extractant recovery tower, and high-purity water is obtained at the top of the tower, with an output of 50 kmol / h, and high-purity extractant is obtained in the bottom of the tower. The extractant is mixed with the extractants obtained in steps (1) and (2), cooled, and then introduced into an extractive distillation tower for recycling.

[0023] The extractant recovery tower has 10 plates, a molar reflux ratio of 0.1, an operating pressure of normal pressure, and a tower top temperature of 99.9° C.; the raw material feeding position is the 10th plate.

[0024] The purity of ethanol obtained by the method is 99.4%, and the yield is 99.2%. The purity of tert-butyl alcohol is 99.1%, and the yield is 99.4%. The purity of water is 99.9%.

[0025] Example 2 like Figure 1 This embodiment provides a method for separating a tert-butyl alcohol-ethanol-water mixture by extractive distillation using a deep eutectic solvent, comprising the following steps: (1) The feed flow rate of the raw material is 100 kmol / h, the temperature is 25°C, the pressure is 1 atm, the feed contains 40 mol% of tert-butanol, 30 mol% of ethanol, and 30 mol% of water, and the flow rate of the first extractant is 26 kmol / h. The raw material and the first extractant enter the extractive distillation tower from the middle and lower parts and the upper part of the first side-line extractive distillation tower respectively, and high-purity tert-butanol is extracted from the top of the extractive distillation tower, with an extraction rate of 40.12 kmol / h, the extractant is extracted from the bottom of the tower, and a mixture of water, ethanol and extractant is extracted from the side line, with an extraction rate of 72 kmol / h; The first extractant is a deep eutectic solvent composed of glucose, choline chloride and ethylene glycol in a molar ratio of 1:2:3; The first extractive distillation tower has 50 plates, a molar reflux ratio of 3.0, an operating condition of normal pressure, a tower top temperature of 81.8°C, and a solvent ratio (molar ratio) of 3; the feed position of the first extractant is the 9th plate, the feed position of water-ethanol-tert-butanol is the 25th plate, and the side line extraction position is the 38th plate.

[0026] (2) The water, ethanol and extractant mixture and the second extractant extracted from the side line in step (1) are introduced into a second side line extractive distillation tower from the middle lower part and the upper part of the tower respectively, and high-purity ethanol is extracted from the top of the tower at a rate of 30.05 kmol / h, the second extractant is extracted from the bottom of the tower, and a mixture containing water and the extractant is extracted from the side line at a rate of 47 kmol / h.

[0027] The second extractant is a low eutectic solvent composed of glucose, choline chloride and ethylene glycol in a molar ratio of 1:2:3, and the flow rate of the extractant is 21 kmol / h; The second extractive distillation tower has 55 plates, a molar reflux ratio of 5.0, an operating condition of normal pressure, a top temperature of 78.0°C, and a solvent ratio (molar ratio) of 3; the feed position of the second extractant is the 10th plate, the feed position of water-ethanol-tert-butanol is the 29th plate, and the side line extraction position is the 42nd plate.

[0028] (3) The water and extractant mixture obtained in step (2) is introduced into an extractant recovery tower to obtain high-purity water at the top of the tower and high-purity extractant at the bottom of the tower, and the extractant is cooled and introduced into an extraction distillation tower for recycling.

[0029] The number of plates of the extractant recovery tower is 35, the molar reflux ratio is 1.0, and the operating pressure is atmospheric pressure; the tower top temperature is 99.9° C., and the raw material feeding position is the 26th tower plate.

[0030] The purity of ethanol obtained by the method is 99.4%, and the yield is 99.2%. The purity of tert-butyl alcohol is 99.5%, and the yield is 99.4%. The purity of water is 99.8%.

[0031] Example 3 like Figure 1 This embodiment provides a method for separating a tert-butyl alcohol-ethanol-water mixture by extractive distillation using a deep eutectic solvent, comprising the following steps: (1) The feed flow rate of the raw material is 100 kmol / h, the temperature is 25°C, the pressure is 1 atm, the feed contains 10 mol% of tert-butanol, 40 mol% of ethanol, 50 mol% of water, and the flow rate of the first extractant is 35 kmol / h. The raw material and the first extractant enter the extractive distillation tower from the middle and lower parts and the upper part of the first side-line extractive distillation tower respectively. High-purity tert-butanol is extracted from the top of the extractive distillation tower, with an extraction rate of 9.98 kmol / h, the extractant is extracted from the bottom of the tower, and a mixture of water, ethanol and extractant is extracted from the side line, with an extraction rate of 107 kmol / h; The first extractant is a deep eutectic solvent composed of glucose, choline chloride and ethylene glycol in a molar ratio of 1:2:2.5; The first extractive distillation tower has 35 plates, a molar reflux ratio of 2.0, an operating condition of normal pressure, a tower top temperature of 81.8°C, and a solvent ratio (molar ratio) of 2; the feed position of the first extractant is the 5th plate, the feed position of water-ethanol-tert-butanol is the 20th plate, and the side line extraction position is the 28th plate.

[0032] (2) The water, ethanol and extractant mixture and the second extractant extracted from the side line in step (1) are introduced into the second side line extractive distillation tower from the middle and lower part and the upper part of the tower respectively, and high-purity ethanol is extracted from the top of the tower at an extraction rate of 40 kmol / h, the second extractant is extracted from the bottom of the tower, and a mixture containing water and the extractant is extracted from the side line at an extraction rate of 73 kmol / h.

[0033] The second extractant is a low eutectic solvent composed of glucose, choline chloride and ethylene glycol in a molar ratio of 1:2:2.5, and the flow rate of the extractant is 26 kmol / h; The second extractive distillation tower has 37 plates, a molar reflux ratio of 3, an operating condition of normal pressure, a top temperature of 78.0°C, and a solvent ratio (molar ratio) of 2; the feed position of the second extractant is the 6th plate, the feed position of water-ethanol-tert-butanol is the 26th plate, and the side line extraction position is the 34th plate.

[0034] (3) The water and extractant mixture obtained in step (2) is introduced into an extractant recovery tower to obtain high-purity water at the top of the tower and high-purity extractant at the bottom of the tower, and the extractant is cooled and introduced into an extraction distillation tower for recycling.

[0035] The number of plates of the extractant recovery tower is 25, the molar reflux ratio is 0.5, and the operating pressure is atmospheric pressure; the tower top temperature is 99.9° C., and the raw material feeding position is the 19th tower plate.

[0036] The purity of ethanol obtained by the method is 99.7%, and the yield is 99.5%. The purity of tert-butyl alcohol is 99.2%, and the yield is 99.1%. The purity of water is 99.9%.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for separating tert-butyl alcohol-ethanol-water mixture by extractive distillation of a deep eutectic solvent, characterized in that: The following steps are involved: (1) The tert-butyl alcohol-ethanol-water mixture and the first extractant enter the extractive distillation tower from the middle and lower parts and the upper parts of the first side-line extractive distillation tower respectively, high-purity tert-butyl alcohol is extracted from the top of the extractive distillation tower, the extractant is extracted from the bottom of the tower, and a mixture containing ethanol, water and the extractant is extracted from the side line; (2) introducing the water, ethanol and extractant mixture and the extractant extracted from the side line in step (1) into a second side line extractive distillation tower from the middle lower part and the upper part of the tower, respectively, to extract high-purity ethanol from the top of the tower, extractant from the bottom of the tower, and extractant and water mixture from the side line; (3) The mixture of water and extractant obtained in step (2) is introduced into an extractant recovery tower to obtain high-purity water at the top of the tower and high-purity extractant at the bottom of the tower, respectively; the extractant is mixed with the extractant obtained at the bottom of the tower in steps (1) and (2), cooled, and then introduced into an extractive distillation tower for recycling.

2. The method according to claim 1, characterized in that: In step (1), the first extractant and the second extractant are both low eutectic solvents composed of glucose, choline chloride and ethylene glycol in a molar ratio of 1:1-3:2-3.

3. The method according to claim 2, characterized in that The first extractant and the second extractant are both low eutectic solvents composed of glucose, choline chloride and ethylene glycol in a molar ratio of 1:2:2.

5.

4. The method according to claim 1, characterized in that: In step (1), the first side-line extractive distillation tower has 20-50 plates, a molar reflux ratio of 1.0-3.0, an operating condition of normal pressure, a tower top temperature of 81-83° C., a solvent molar ratio of 0.5-3, and a side-line extraction position of 14-35 plates.

5. The method according to claim 1, characterized in that In step (1), the first extractant is fed to the 3rd to 13th tray, and the water-ethanol-tert-butanol is fed to the 12th to 40th tray.

6. The method according to claim 1, characterized in that In step (2), the second side-line extractive distillation tower has 30-55 plates, a molar reflux ratio of 1.5-5.0, an operating condition of normal pressure, a top operating temperature of 77.5-79.0° C., a molar ratio of the solvent of 1-3, and a side-line extraction position of the 23rd to 42nd plates.

7. The method according to claim 1, characterized in that In step (2), the feeding position of the second extractant is the 3rd to 10th tower plates, and the feeding position of the raw material is the 22nd to 45th tower plates.

8. The method according to claim 1, characterized in that The number of plates of the extractant recovery tower in step (3) is 10-35, the molar reflux ratio is 0.1-1.0, the operating pressure is atmospheric pressure, and the tower top operating temperature is 99-101° C.; the raw material feeding position is the 10th to 26th tower plate.

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