Method for extracting, rectifying and separating diethoxymethane, ethanol and toluene by using mixed extracting agent

Abstract

The invention relates to a method for extracting, rectifying and separating tert-amyl ethyl ether, ethanol and water by using a mixed extracting agent, which utilizes the characteristic that relative volatility among molecules is changed along with the addition of the mixed extracting agent in a tert-amyl ethyl ether-ethanol azeotropic system, a tert-amyl ethyl ether-water azeotropic system and an ethanol-water azeotropic system. Through three-tower operation of the rectifying tower (T1), the rectifying tower (T2) and the rectifying tower (T3), efficient separation of a ternary mixture is achieved, and after separation, the concentration of a tert-amyl ethyl ether product is larger than 99.90%, the concentration of an ethanol product is larger than 99.90%, and the concentration of an aquatic product is larger than 99.90%. The method solves the problem that the azeotropic system is difficult to separate by using common rectification, is flexible to operate, is economical and environment-friendly, and can realize effective separation of the ternary azeotropic mixture through three towers.

Description

Technical Field

[0001] The present invention belongs to the field of chemical separation and purification, and particularly relates to a method for separating tert-amyl ethyl ether-ethanol-water azeotrope by extractive distillation.

Background Art

[0002] As an oxygenate, tert-amyl ethyl ether can significantly increase the octane number of gasoline and effectively improve the combustion efficiency of gasoline. Generally, the etherification reaction of ethanol and isopentene can be used to prepare tert-amyl ethyl ether respectively. However, the supply of isopentene is mainly limited to catalytic cracking and steam cracking of gasoline. Therefore, currently, researchers are committed to exploring alternative routes for its synthesis and have found that tert-amyl ethyl ether can be prepared by the etherification of tert-amyl alcohol and ethanol. However, tert-amyl ethyl ether, ethanol, and water are prone to form homogeneous or heterogeneous azeotropes, and the formation of azeotropic substances makes it difficult to separate this ternary system by ordinary distillation methods.

[0003] Distillation is a very important link in petrochemical and oil refining production processes. Its purpose is to separate the components of a mixture to reach the specified purity, and it is widely used in fields such as chemical engineering and petrochemical engineering. Extractive distillation is a technique commonly used in chemical engineering for separating and purifying mixtures, especially suitable for systems that are difficult to separate by traditional distillation methods. This technique improves the separation efficiency and purity by changing the relative volatility difference and is widely used in the refining and separation processes of industrial chemicals.

[0004] The present invention utilizes the characteristic that the relative volatility of the azeotropic composition of tert-amyl ethyl ether-ethanol-water azeotrope changes in a more easily separable direction with the addition of a mixed extractant to separate the tert-amyl ethyl ether-ethanol-water ternary mixture. Specifically, the present invention uses three distillation columns for separation and purification, designs corresponding process schemes, and realizes the efficient separation of the mixture. The present invention is applicable to the mixture of tert-amyl ethyl ether-ethanol-water, with flexible operation, and can effectively separate the ternary azeotropic mixture through extractive distillation.

Summary of the Invention

[0005] [Technical Problems to be Solved]

[0006] The purpose of the present invention is to provide a method for separating tert-amyl ethyl ether-ethanol-water mixture by extractive distillation using a mixed extractant, and to realize the process design for efficient separation of ternary azeotropic mixture by extractive distillation.

[0007] [Technical Solutions]

[0008] The present invention provides a method for separating tert-amyl ethyl ether - ethanol - water by extractive distillation using a mixed extractant. By utilizing the characteristic that the relative volatility of the azeotropes of tert-amyl ethyl ether - ethanol, tert-amyl ethyl ether - water, and ethanol - water changes in a direction more conducive to separation with the addition of the mixed extractant, extractive distillation is carried out in a three-column distillation manner, and the proposed process flow can achieve efficient separation of the ternary mixture of tert-amyl ethyl ether - ethanol - water.

[0009] A method for separating tert-amyl ethyl ether - ethanol - water by extractive distillation using a mixed extractant proposed by the present invention is characterized in that the device for separating the azeotropic system of tert-amyl ethyl ether - ethanol - water mainly comprises the following parts:

[0010] Distillation column (T1), distillation column (T2), distillation column (T3), condenser (COL), mixer (MIX), pump (P1), pump (P2), top storage tank (C1), top storage tank (C2), top storage tank (C3), reboiler (H1), reboiler (H2), reboiler (H3), condenser (CL1), condenser (CL2), condenser (CL3); The supplementary fresh mixed extractant and the recycled mixed extractant are mixed in the mixer (MIX) and then connected to the distillation column (T1) through a pipeline; The distillation column (T1) is connected to the distillation column (T2) through a pipeline via the pump (P1); The distillation column (T2) is connected to the distillation column (T3) through a pipeline; The distillation column (T3) is connected to the mixer (MIX) through a pipeline first via the pump (P2) and then via the condenser (COL); The condenser (CL1) is connected to the distillation column (T1) and the top storage tank (C1), the condenser (CL2) is connected to the distillation column (T2) and the top storage tank (C2), and the condenser (CL3) is connected to the distillation column (T3) and the top storage tank (C3); The reboiler (H1), reboiler (H2), and reboiler (H3) are respectively connected to the distillation column (T1), distillation column (T2), and distillation column (T3);

[0011] The method for separating tert-amyl ethyl ether - ethanol - water by extractive distillation using a mixed extractant invented mainly comprises the following steps:

[0012] (1) The raw material mixture of tert-amyl ethyl ether, ethanol, and water and the mixed extractant are respectively added to the distillation column (T1) from the lower part and the upper part of the column. In the distillation column (T1), the separation of ethanol is achieved. A part of the bottom stream of the distillation column (T1) is returned to the distillation column (T1) after heat exchange in the reboiler (H1), and a part is fed into the distillation column (T2) as feed; Ethanol is condensed by the condenser (CL1) and then enters the top storage tank (C1), with a part refluxing and the other part being withdrawn from the top of the distillation column (T1).

[0013] (2) Inside the rectification column (T2), the separation of ethanol is achieved. A part of the bottom stream of the rectification column (T2) is returned to the rectification column (T2) after heat exchange in the reboiler (H2), and a part is fed into the rectification column (T3) as feedstock; the diethoxymethane enters the top storage tank (C2) after condensation in the condenser (CL2), with a part refluxing and the other part being withdrawn from the top of the rectification column (T2).

[0014] (3) Inside the rectification column (T3), the separation of water is achieved. A part of the bottom stream of the rectification column (T3) is returned to the rectification column (T3) after heat exchange in the reboiler (H3), and a part of the reflux first passes through the pump (P2) and then through the condenser (COL) and is fed into the mixer (MIX); the water enters the top storage tank (C3) after condensation in the condenser (CL3), with a part refluxing and the other part being withdrawn from the top of the rectification column (T3).

[0015] According to another preferred embodiment of the present invention, it is characterized in that: the operating pressure of the rectification column (T1) is 0.1 atm, and the number of theoretical plates is 55 - 79; the operating pressure of the rectification column (T2) is 0.8 atm, and the number of theoretical plates is 38 - 71; the operating pressure of the rectification column (T3) is 0.1 atm, and the number of theoretical plates is 5 - 20. The feed temperature of the mixed extractant is 40 °C.

[0016] According to another preferred embodiment of the present invention, it is characterized in that: the mass ratio of the feed flow rates of the mixed extractant to the mixture of tert-amyl ethyl ether, ethanol and water is 0.5 - 0.7.

[0017] According to another preferred embodiment of the present invention, it is characterized in that: in the mixture of tert-amyl ethyl ether, ethanol and water, the mass fraction of diethoxymethane is 70% - 75%, the mass fraction of ethanol is 10% - 15%, and the mass fraction of toluene is 10% - 15%.

[0018] According to another preferred embodiment of the present invention, it is characterized in that: by adopting this process flow, the clean and efficient separation of the mixture can be achieved. After separation, the purity of diethoxymethane is greater than 99.90% (mass fraction), the purity of ethanol is greater than 99.90% (mass fraction), the purity of toluene is greater than 99.90% (mass fraction), and the purity of the mixed extractant recovered from the bottom of the rectification column T3 is greater than 99.90% (mass fraction).

[0019] [Beneficial effects]

[0020] The present invention has the following beneficial effects:

[0021] (1) The beneficial effect of the present invention is that the high-efficient separation of the ternary azeotropic mixture of diethoxymethane, ethanol and toluene is achieved by using the extractive distillation method with a mixed extractant.

[0022] (2) The designed process flow can achieve the economical and clean separation of the mixture.

[0023] (3) The present invention is clean, efficient, economical, environmentally friendly, simple in process and flexible in operation.

Description of the Drawings

[0024] Appendix Figure 1 It is a schematic diagram of the method for separating tert-amyl ethyl ether, ethanol and water by extractive distillation using a mixed extractant.

[0025] In the figure, T1 - distillation column; T2 - distillation column; T3 - distillation column; CL1 - condenser; CL2 - condenser; CL3 - condenser; COL - condenser; H1 - reboiler; H2 - reboiler; H3 - reboiler; P1 - pump; P2 - pump; C1 - top storage tank; C2 - top storage tank; C3 - top storage tank; MIX - mixer; the numbers represent each material flow.

Specific Embodiments

[0026] The following is further described in conjunction with the drawings, which does not limit the scope involved in the present invention.

[0027] Example 1:

[0028] The feed flow rate is 100 kmol / h, the feed temperature is 40 °C, the pressure is 0.1 atm (absolute pressure). In the feed material flow, the mass fraction of tert-amyl ethyl ether is 36.44%, the mass fraction of ethanol is 19.54%, and the mass fraction of water is 44.02%. The feed flow rate of the extractant is 63.33 kmol / h, the feed temperature is 40 °C, and the pressure is 0.1 atm (absolute pressure). The operating pressure of the distillation column (T1) is 0.1 atm (absolute pressure), the number of trays is 54, the feed positions are the 19th tray and the 51st tray respectively, the top temperature is 54.73 °C, and the bottom temperature is 106.67 °C; the operating pressure of the distillation column (T2) is 0.8 atm (absolute pressure), the number of trays is 65, the feed position is the 51st tray, the top temperature is 54.73 °C, and the bottom temperature is 722.80 °C; the operating pressure of the distillation column (T3) is 0.1 atm (absolute pressure), the number of trays is 23, the feed position is the 20th tray, the top temperature is 46.60 °C, and the bottom temperature is 11.99 °C; after separation, the concentration of the tert-amyl ethyl ether product is greater than 99.90%, the concentration of the ethanol product is greater than 99.90%, and the concentration of the water product is greater than 99.90%.

[0029] Example 2:

[0030] The feed flow rate is 100 kmol / h, the feed temperature is 40 °C, the pressure is 0.1 atm (absolute pressure). In the feed stream, the mass fraction of tert-amyl ethyl ether is 36.44%, the mass fraction of ethanol is 19.54%, and the mass fraction of water is 44.02%. The extraction agent feed flow rate is 63.33 kmol / h, the feed temperature is 40 °C, and the pressure is 0.1 atm (absolute pressure). The operating pressure of the distillation column (T1) is 0.1 atm (absolute pressure), the number of trays is 54, the feed positions are the 19th tray and the 51st tray respectively, the top temperature is 54.73 °C, and the bottom temperature is 106.67 °C; the operating pressure of the distillation column (T2) is 0.8 atm (absolute pressure), the number of trays is 65, the feed position is the 51st tray, the top temperature is 54.73 °C, and the bottom temperature is 722.80 °C; the operating pressure of the distillation column (T3) is 0.1 atm (absolute pressure), the number of trays is 23, the feed position is the 20th tray, the top temperature is 46.60 °C, and the bottom temperature is 11.99 °C; after separation, the concentration of the tert-amyl ethyl ether product is greater than 99.90%, the concentration of the ethanol product is greater than 99.90%, and the concentration of the water product is greater than 99.90%.

[0031] Example 3:

[0032] The feed flow rate is 100 kmol / h, the feed temperature is 40 °C, the pressure is 0.1 atm (absolute pressure). In the feed stream, the mass fraction of tert-amyl ethyl ether is 36.44%, the mass fraction of ethanol is 19.54%, and the mass fraction of water is 44.02%. The extraction agent feed flow rate is 63.33 kmol / h, the feed temperature is 40 °C, and the pressure is 0.1 atm (absolute pressure). The operating pressure of the distillation column (T1) is 0.1 atm (absolute pressure), the number of trays is 54, the feed positions are the 19th tray and the 51st tray respectively, the top temperature is 54.73 °C, and the bottom temperature is 106.67 °C; the operating pressure of the distillation column (T2) is 0.8 atm (absolute pressure), the number of trays is 65, the feed position is the 51st tray, the top temperature is 54.73 °C, and the bottom temperature is 722.80 °C; the operating pressure of the distillation column (T3) is 0.1 atm (absolute pressure), the number of trays is 23, the feed position is the 20th tray, the top temperature is 46.60 °C, and the bottom temperature is 11.99 °C; after separation, the concentration of the tert-amyl ethyl ether product is greater than 99.90%, the concentration of the ethanol product is greater than 99.90%, and the concentration of the water product is greater than 99.90%.

Claims

1. A method for separating tert-amyl ethyl ether, ethanol and water by extractive distillation using a mixed extractant, characterized in that The device for implementing the method mainly includes the following parts: Rectifying tower T1, rectifying tower T2, rectifying tower T3, condenser COL, mixer MIX, overhead storage tank C1, overhead storage tank C2, overhead storage tank C3, reboiler H1, reboiler H2, reboiler H3, condenser CL1, condenser CL2, condenser CL3, pump P1, pump P2; wherein the bottom of rectifying tower T1 enters rectifying tower T2 via pump P1, the bottom of rectifying tower T2 enters rectifying tower T3, the bottom of rectifying tower T3 first passes through pump P2 and then enters mixer MIX via condenser COL, the recovered mixed extractant and the supplemented fresh mixed extractant enter rectifying tower T1 via the top of rectifying tower T1 via mixer MIX, and the components to be separated enter via the bottom of rectifying tower T1; A method for separating tert-amyl ethyl ether, ethanol and water by using the above device comprises the following steps: (1) tert-amyl ethyl ether, ethanol and water mixture enter from the bottom of distillation tower T1, and extractant enters from the top of distillation tower T1. After effective contact extraction and separation, tert-amyl ethyl ether flows out from the top of distillation tower T1, and ethanol, water and mixed extractant flow out from the bottom of distillation tower T1 and enter distillation tower T2 through pump P1; (2) After distillation and separation in distillation tower T2, ethanol flows out of the top stream, and water and mixed extractant flow out of the bottom of distillation tower T2 and enter distillation tower T3; (3) After distillation and separation in the distillation tower T3, water flows out of the top stream, and the stream at the bottom of the distillation tower T3 is a nearly pure mixed extractant. The mixed extractant is pressurized by the pump P2 and enters the cooler COL for cooling, and then enters the mixer MIX together with the replenished fresh mixed extractant and enters the distillation tower T1 for recycling; The mixed extractant is a mixed solution of 59% (mass fraction) of dimethyl sulfoxide and 41% (mass fraction) of glycerol.

2. The method for separating tert-amyl ethyl ether, ethanol and water by extractive distillation using a mixed extractant according to claim 1, characterized in that: The operating pressure of the distillation tower (T1) is 0.1 atm, and the number of theoretical plates is 55 to 79; the operating pressure of the distillation tower (T2) is 0.8 atm, and the number of theoretical plates is 38 to 71; the operating pressure of the distillation tower (T3) is 0.1 atm, and the number of theoretical plates is 5 to 20. The feed temperature of the mixed extractant is 40°C.

3. The method for separating tert-amyl ethyl ether, ethanol and water by extractive distillation using a mixed extractant according to claim 1, characterized in that: The feed flow mass ratio of the mixed extractant to the mixture of tert-amyl ethyl ether, ethanol and water is 0.5-0.

7.

4. The method for separating tert-amyl ethyl ether, ethanol and water by extractive distillation using a mixed extractant according to claim 1, characterized in that: In the mixed liquid of tert-amyl ethyl ether, ethanol and water, the mass fraction of diethoxymethane is 70% to 75%, the mass fraction of ethanol is 10% to 15%, and the mass fraction of toluene is 10% to 15%.

5. The method for separating tert-amyl ethyl ether, ethanol and water by extractive distillation using a mixed extractant according to claim 1, characterized in that: After separation, the purity of tert-amyl ethyl ether is greater than 99.90% (mass fraction), the purity of ethanol is greater than 99.90% (mass fraction), the purity of water is greater than 99.90% (mass fraction), and the purity of the mixed extractant recovered at the bottom of the distillation tower T3 is greater than 99.90% (mass fraction).

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