A method for separating an ethyl acetate-ethanol-cyclohexane mixture by heat integration of extractive distillation with varying pressure

Abstract

The present invention relates to a device for separating an ethyl acetate-ethanol-cyclohexane mixture by heat-integrated extraction and rectification with pressure change. The method uses dimethyl sulfoxide as an extractant, and the ethyl acetate-ethanol-cyclohexane mixture enters a distillation tower 1 (T1) for heat-integrated extraction and rectification separation with pressure change, and the purity of the separated ethyl acetate, ethanol, and cyclohexane is as high as 99.9% or more, and the large latent heat of the gas-phase azeotrope at the top of the distillation tower 3 (T3) is used to partially heat the liquid in the bottom of the distillation tower 1 (T1) to vaporize it, while the gas-phase azeotrope at the top of the distillation tower 3 (T3) is completely condensed, and heat integration is achieved. The method has the advantages of low energy consumption, simple process, high purity of ethyl acetate, ethanol, and cyclohexane after separation, and the used extractant dimethyl sulfoxide is almost non-volatile, reducing the loss of the extractant, and is easy to recover, has good chemical thermal stability, and is green and pollution-free.

Description

[Technical field]

[0001] The invention belongs to the field of chemical separation and purification, and specifically relates to a method for separating an ethyl acetate-ethanol-cyclohexane mixture by extractive distillation heat integration with pressure changes, and further relates to a method for separating an ethyl acetate-ethanol-cyclohexane mixture by extractive distillation heat integration with pressure changes using dimethyl sulfoxide as an extractant. [Background technology]

[0002] Ethyl acetate, ethanol, and cyclohexane are common chemicals in daily life. Ethyl acetate is one of the most widely used fatty acid esters. It is a fast-drying solvent with excellent solubility. It is an excellent industrial solvent. It can also be used as an eluent for column chromatography, a cleaning agent in the textile industry, and a flavor extractant for special modified alcohols in the food industry. It is also used as an extractant for pharmaceutical processes and organic acids. Ethanol is an important organic solvent and is widely used in medicine, coatings, sanitary products, cosmetics, oils and fats, accounting for about 50% of the total ethanol consumption. Ethanol is an important basic chemical raw material and has derived many intermediates for products such as medicines, dyes, coatings, spices, synthetic rubber, detergents, pesticides, etc. Cyclohexane is used as a solvent for rubber, coatings, varnishes, a diluent for adhesives, and an oil extractant. Its advantage is that it has low toxicity, so it is often used instead of benzene for degreasing, delubricating, and depainting. Among the solvents used in the production of capsaicin, waste liquid containing ethyl acetate-ethanol-cyclohexane is easily generated, and ethanol and ethyl acetate are very important organic solvents and organic synthesis aids. Under normal pressure, ethanol / ethyl acetate, ethanol / cyclohexane, ethyl acetate / cyclohexane, and ethanol / ethyl acetate / cyclohexane can form azeotropes, which increases the difficulty of separation.

[0003] The present invention adopts the heat integration of extraction distillation by changing the pressure to separate and recycle the ethyl acetate-ethanol-cyclohexane mixture with high purity, uses dimethyl sulfoxide as an extractant, and utilizes the characteristics that dimethyl sulfoxide and pressure have a great influence on the relative volatility of ethanol / ethyl acetate, ethanol / cyclohexane, and ethyl acetate / cyclohexane azeotropes to achieve separation. The large latent heat of the gas phase azeotrope at the top of the distillation tower 3 (T3) is utilized to partially heat the liquid in the bottom of the distillation tower 1 (T1) to vaporize it, while the gas phase azeotrope at the top of the distillation tower 3 (T3) is completely condensed, thereby achieving heat integration. The purity of the separated ethyl acetate, ethanol, and cyclohexane is as high as 99.9% or more, and the extractant can be recycled and reused with high purity, which greatly reduces the separation cost. The method has low energy consumption, less equipment, and simple process. [Summary of the invention]

[0004] [Technical issues to be solved]

[0005] Another object of the present invention is to provide a method for separating an ethyl acetate-ethanol-cyclohexane mixture by heat integration of extractive distillation with pressure changes using the device.

[0006] The invention aims to provide a device for separating ethyl acetate-ethanol-cyclohexane mixture of dimethyl sulfoxide by heat integration of extractive distillation with pressure change.

[0007] Another object of the present invention is to achieve a significant reduction in energy consumption using heat integration.

[0008] [Technical solution]

[0009] The present invention is achieved through the following technical solutions.

[0010] A method for separating an ethyl acetate-ethanol-cyclohexane mixture by heat-integrated extraction distillation with pressure change, characterized in that the device for implementing the method mainly comprises the following parts: a distillation tower 1 (T1), a distillation tower 2 (T2), a distillation tower 3 (T3), a condenser 1 (D1), a condenser 2 (D2), a condenser 3 (D3), a reboiler 1 (R1), a reboiler 2 (R2), a reboiler 3 (R3), a reboiler 4 (R4), a cooler (COLD), a centrifugal pump (P1), a centrifugal pump (P2); wherein the distillation tower 1 (T1) The bottom stream passes through a centrifugal pump (P1) and enters a distillation tower 2 (T2), and a high-purity product cyclohexane is extracted from the top stream of the distillation tower 1 (T1); the bottom stream of the distillation tower 2 (T2) passes through a centrifugal pump (P1) and enters a distillation tower 3 (T3), and a high-purity product ethyl acetate is extracted from the top stream of the distillation tower 2 (T2), and a high-purity product ethanol is extracted from the top stream of the distillation tower 3 (T3); the high-purity extractant flowing out of the bottom of the distillation tower 3 (T3) passes through a centrifugal pump (P3), a reboiler 2 (R2) and a cooler (COLD) and is recycled to the extraction tower;

[0011] The separation method mainly comprises the following steps:

[0012] (1) The ethyl acetate-ethanol-cyclohexane mixture enters from the bottom of the distillation tower (T1), and the extractant enters from the top of the distillation tower 1 (T1). After effective contact and separation, the high-purity product cyclohexane is extracted from the top flow of the distillation tower 1 (T1), and the ethyl acetate-ethanol-extractant mixture in the raffinate phase enters the distillation tower 2 (T2) from the bottom of the distillation tower 1 (T1) through the centrifugal pump (P1);

[0013] (2) The ethyl acetate-ethanol-extractant mixture enters from the bottom of the distillation tower 2 (T2), and the extractant enters from the top of the distillation tower 2 (T2). After effective contact and separation, high-purity product ethyl acetate is extracted from the top flow of the distillation tower 2 (T2), and the ethanol-extractant mixture in the raffinate phase enters from the bottom of the distillation tower 2 (T2) into the distillation tower 3 (T3);

[0014] (3) The ethanol-extractant mixture enters from the bottom of the distillation tower 3 (T3), and after effective contact separation, the high-purity product ethanol is extracted from the top flow of the distillation tower 3 (T3), and the high-purity extractant flows out from the bottom of the distillation tower 3 (T3), passes through the centrifugal pump (P2), the reboiler 2 (R2) and the cooler (COLD) and enters the distillation tower (T1) for recycling;

[0015] (4) The large latent heat of the gas-phase azeotrope at the top of the distillation tower 3 (T3) is used to partially heat the liquid in the bottom of the distillation tower 1 (T1) to vaporize it, while the gas-phase azeotrope at the top of the distillation tower 3 (T3) is completely condensed, and the distillate stream at the bottom of the distillation tower 3 (T3) is used to heat the liquid in the bottom of the distillation tower 2 (T2) to vaporize it, thereby achieving heat integration;

[0016] The extractant is dimethyl sulfoxide.

[0017] According to another preferred embodiment of the present invention, it is characterized in that: the number of plates of distillation tower 1 (T1) is 30-40, the pressure is 0.1-0.5atm, and the temperature is 30-60°C; the number of plates of distillation tower 2 (T2) is 40-80, the pressure is 0.1-0.5atm, and the temperature is 30-60°C; the number of plates of distillation tower 3 (T3) is 10-30, and the temperature is 70-100°C.

[0018] According to another preferred embodiment of the present invention, it is characterized in that: the extractant is dimethyl sulfoxide.

[0019] According to another preferred embodiment of the present invention, it is characterized in that the feed flow rate molar ratio of the extractant to the ethyl acetate-ethanol-cyclohexane mixture is 0.5-2.

[0020] According to another preferred embodiment of the present invention, it is characterized in that: in the ethyl acetate-ethanol-cyclohexane mixture feed, the azeotropic point is used as the feed composition, the molar fraction of ethyl acetate is 3.6%, the molar fraction of ethanol is 42.6%, and the molar fraction of cyclohexane is 53.8%.

[0021] According to another preferred embodiment of the present invention, it is characterized in that: the purity of cyclohexane recovered from the top of distillation tower 1 (T1) is higher than 99.9%, and the yield is higher than 99.9%; the purity of ethyl acetate recovered from the top of distillation tower 2 (T2) is higher than 99.9%, and the yield is higher than 99.9%; the purity of ethanol recovered from the top of distillation tower 3 (T3) is higher than 99.9%, and the yield is higher than 99.9%.

[0022] [Beneficial Effects]

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The method is used to separate the ethyl acetate-ethanol-cyclohexane mixture to obtain high-purity ethyl acetate, ethanol and cyclohexane, thereby solving the problem that the ethyl acetate-ethanol-cyclohexane mixture is difficult to separate.

[0025] (2) This method has the advantages of simple process, less investment in equipment, high purity of ethyl acetate, ethanol and cyclohexane after separation, etc. The extraction agent dimethyl sulfoxide used is easy to recover, has good chemical thermal stability, and is green and pollution-free.

[0026] (3) The extractant dimethyl sulfoxide used in this method is almost non-volatile, which reduces the loss of the extractant and avoids secondary pollution of ethyl acetate, ethanol and cyclohexane. In addition, the extractant is easy to recycle and reduce the separation cost.

[0027] (4) The process operation cost is reduced after heat integration.

Brief Description of the Drawings

[0028] Figure 1 The present invention is a process flow chart for separating an ethyl acetate-ethanol-cyclohexane mixture by heat integration of extractive distillation with pressure change.

[0029] In the figure, T1-distillation tower 1, T2-distillation tower 2, T3-distillation tower 3; W1-bottom stream 1; W2-bottom stream 2; W3-bottom stream 3; COLD-cooler; C1-condenser 1; C2-condenser 2; C3-condenser 3; D1-top stream 1; D2-top stream 2; D3-top stream 3; R1-reboiler 1; R2-reboiler 2; R3-reboiler 3; R4-reboiler 4; P1-centrifugal pump 1, P2-centrifugal pump 2; P3-centrifugal pump 3. [Specific implementation method]

[0030] Embodiment 1:

[0031] The feed flow rate is 100 kmol / h, the feed contains 3.6% ethyl acetate, 42.6% ethanol, and 53.8% cyclohexane (molar fraction), the number of theoretical plates of distillation tower 1 (T1) is 40, the pressure is 0.3 atm, the ethyl acetate-ethanol-cyclohexane mixture enters from the bottom of distillation tower 1 (T1), the extractant enters from the top of distillation tower 1 (T1), the extractant is dimethyl sulfoxide, and the flow rate is 100 kmol / h; the ethyl acetate-ethanol-extractant mixture enters from the bottom of distillation tower 2 (T2), the extractant enters from the top of distillation tower 2 (T2), the number of theoretical plates of distillation tower 2 (T2) is 60, the pressure is 0.4 atm, the extractant is dimethyl sulfoxide, and the flow rate is 20 kg / h (the molar ratio of the extractant to the feed flow rate of the ethyl acetate-ethanol-cyclohexane mixture is 1.1). The ethanol-extractant mixture enters from the bottom of distillation tower 3 (T3). The number of theoretical plates of distillation tower 3 (T3) is 15, and the operating pressure of the distillation tower is atmospheric pressure. After separation, the purity of ethyl acetate is 99.97%, and the yield is 100%, the purity of ethanol is 99.93%, and the yield is 99.92%, and the purity of cyclohexane is 99.98%, and the yield is 99.99%.

[0032] Embodiment 2:

[0033] The feed flow rate is 100 kmol / h, the feed contains 3.6% ethyl acetate, 42.6% ethanol, and 53.8% cyclohexane (molar fraction), the number of theoretical plates of distillation tower 1 (T1) is 30, the pressure is 0.5 atm, the ethyl acetate-ethanol-cyclohexane mixture enters from the bottom of distillation tower 1 (T1), the extractant enters from the top of distillation tower 1 (T1), the extractant is dimethyl sulfoxide, and the flow rate is 120 kmol / h; the ethyl acetate-ethanol-extractant mixture enters from the bottom of distillation tower 2 (T2), the extractant enters from the top of distillation tower 2 (T2), the number of theoretical plates of distillation tower 2 (T2) is 80, the pressure is 0.5 atm, the extractant is dimethyl sulfoxide, and the flow rate is 30 kmol / h. The ethanol-extractant mixture enters from the bottom of distillation tower 3 (T3). The number of theoretical plates of distillation tower 3 (T3) is 30, and the operating pressure of the distillation tower is atmospheric pressure. After separation, the purity of ethyl acetate is 99.98%, and the yield is 99.99%. The purity of ethanol is 99.92%, and the yield is 99.91%. The purity of cyclohexane is 99.97%, and the yield is 99.98%.

[0034] Embodiment 3:

[0035] The feed flow rate is 100 kmol / h, the feed contains 3.6% ethyl acetate, 42.6% ethanol, and 53.8% cyclohexane (molar fraction), the number of theoretical plates of distillation tower 1 (T1) is 35, the pressure is 0.1 atm, the ethyl acetate-ethanol-cyclohexane mixture enters from the bottom of distillation tower 1 (T1), the extractant enters from the top of distillation tower 1 (T1), the extractant is dimethyl sulfoxide, and the flow rate is 90 kmol / h; the ethyl acetate-ethanol-extractant mixture enters from the bottom of distillation tower 2 (T2), the extractant enters from the top of distillation tower 2 (T2), the number of theoretical plates of distillation tower 2 (T2) is 40, the pressure is 0.1 atm, the extractant is dimethyl sulfoxide, and the flow rate is 60 kmol / h. The ethanol-extractant mixture enters from the bottom of distillation tower 3 (T3). The number of theoretical plates of distillation tower 3 (T3) is 10, and the operating pressure of the distillation tower is normal pressure. After separation, the purity of ethyl acetate is 99.99%, and the yield is 99.98%. The purity of ethanol is 99.91%, and the yield is 99.93%. The purity of cyclohexane is 99.95%, and the yield is 99.95%.

Claims

1. A method for separating an ethyl acetate-ethanol-cyclohexane mixture by heat integration of extractive distillation with varying pressure, characterized in that The device for implementing the method mainly includes the following parts: a distillation tower 1 (T1), a distillation tower 2 (T2), a distillation tower 3 (T3), a condenser 1 (C1), a condenser 2 (C 2), condenser 3 (C3), reboiler 1 (R1), reboiler 2 (R2), reboiler 3 (R3), reboiler 4 (R4), cooler (COLD), centrifugal pump 1 (P1), centrifugal pump 2 (P2); wherein the bottom stream of the distillation tower 1 (T1) enters the distillation tower 2 (T2) through the centrifugal pump 1 (P1), and the high-purity product cyclohexane is produced from the top stream of the distillation tower 1 (T1); the bottom stream of the distillation tower 2 (T2) enters the distillation tower 3 (T3) through the centrifugal pump 1 (P1), and the high-purity product ethyl acetate is produced from the top stream of the distillation tower 2 (T2), and the high-purity product ethanol is produced from the top stream of the distillation tower 3 (T3); the high-purity extractant flowing out of the bottom of the distillation tower 3 (T3) is recycled to the extraction tower through the centrifugal pump 3 (P3), the reboiler 2 (R2) and the cooler (COLD); A method for separating an ethyl acetate-ethanol-cyclohexane mixture by heat-integrated extraction distillation with pressure changes using the above device comprises the following steps: (1) an ethyl acetate-ethanol-cyclohexane mixture enters from the bottom of a distillation tower 1 (T1), wherein the feed composition is the azeotropic point, the molar fraction of ethyl acetate is 3.6%, the molar fraction of ethanol is 42.6%, and the molar fraction of cyclohexane is 53.8%. Dimethyl sulfoxide is used as an extractant and enters from the top of the distillation tower 1 (T1). The number of plates of the distillation tower 1 (T1) is 30-40, the pressure is 0.1-0.5 atm, and the temperature is 30-60° C. After effective contact separation, a high-purity product cyclohexane is extracted from the top flow of the distillation tower 1 (T1), and the ethyl acetate-ethanol-extractant mixture in the raffinate phase enters the distillation tower 2 (T2) from the bottom of the distillation tower 1 (T1) through a centrifugal pump 1 (P1); (2) an ethyl acetate-ethanol-extractant mixture enters from the bottom of the distillation tower 2 (T2), and dimethyl sulfoxide as an extractant enters from the top of the distillation tower 2 (T2). The number of plates of the distillation tower 2 (T2) is 40-80, the pressure is 0.1-0.5 atm, and the temperature is 30-60° C. After effective contact separation, a high-purity product ethyl acetate is extracted from the top flow of the distillation tower 2 (T2), and the ethanol-extractant mixture in the raffinate phase enters the distillation tower 3 (T3) from the bottom of the distillation tower 2 (T2); (3) The ethanol-extractant mixture enters from the bottom of the distillation tower 3 (T3). The number of plates of the distillation tower 3 (T3) is 10 to 30, the temperature is 70 to 100°C, and the pressure is atmospheric pressure. After effective contact and separation, high-purity product ethanol is extracted from the top flow of the distillation tower 3 (T3), and the high-purity extractant flows out from the bottom of the distillation tower 3 (T3), passes through the centrifugal pump 2 (P2), the reboiler 2 (R2) and the cooler (COLD), and enters the distillation tower 1 (T1) for recycling; (4) The large latent heat of the gas-phase azeotrope at the top of distillation tower 3 (T3) is used to partially heat the liquid in the bottom of distillation tower 1 (T1) to vaporize it, while the gas-phase azeotrope at the top of distillation tower 3 (T3) is completely condensed, and the distillate stream at the bottom of distillation tower 3 (T3) is used to heat the liquid in the bottom of distillation tower 2 (T2) to vaporize it, thereby achieving heat integration.

2. The method according to claim 1, further characterized in that the feed flow rate molar ratio of the extractant to the ethyl acetate-ethanol-cyclohexane mixture is 0.5 to 2:

1.

3. The method according to claim 1 is further characterized in that: the purity of cyclohexane recovered from the top of the distillation tower 1 (T1) is higher than 99.9%, and the yield is higher than 99.9%; the purity of ethyl acetate recovered from the top of the distillation tower 2 (T2) is higher than 99.9%, and the yield is higher than 99.9%; the purity of ethanol recovered from the top of the distillation tower 3 (T3) is higher than 99.9%, and the yield is higher than 99.9%.

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