Liquid-liquid extraction process for separating isopropyl ether-ethanol azeotrope by using [BMIM] AC ionic liquid

Abstract

The invention relates to a liquid-liquid extraction process for separating isopropyl ether-ethanol azeotrope by using [BMIM] AC ionic liquid. The process consists of an isopropyl ether extraction tower, an ethanol rectifying tower and a flash tank. 1-butyl-3-methylimidazole acetate is used as an extraction agent and enters the extraction tower from the top of the extraction tower. A raw material isopropyl ether-ethanol binary mixture enters an extraction tower from the bottom, high-purity isopropyl ether is obtained after a product at the top of the extraction tower enters a flash tank, an extraction agent and ethanol are extracted from a tower kettle of the extraction tower and then enter a rectifying tower, high-purity ethanol is obtained from the upper portion after flash evaporation of the flash tank, and high-purity isopropyl ether is obtained from the lower portion. And the high-purity extracting agent obtained at the bottom is recycled. The method has the advantages of low equipment investment, simplicity and convenience in operation, low energy consumption and the like, and has greater economic and environmental advantages. The adopted extracting agent 1-butyl-3-methylimidazole acetic acid is known as a hot environment-friendly solvent nowadays due to the excellent properties of low toxicity, easiness in separation and recovery, recyclability, good thermal stability and the like of the extracting agent 1-butyl-3-methylimidazole acetic acid. Meanwhile, the method has great superiority in the aspects of saving energy consumption, reducing the total cost and relieving the influence on the environment.

Description

[Technical field]

[0001] The invention belongs to separation and purification technology in the field of chemical industry, and specifically relates to a process method for extracting and separating isopropyl ether-ethanol by using an extraction tower, a rectification tower and two flash tanks. [Background technology]

[0002] Methyl tert-butyl ether (MTBE) is used as a gasoline additive because it can increase the octane number. However, due to its high solubility in water, it easily pollutes groundwater and pollutes soil due to leakage from gas stations, resulting in restrictions on the use of MTBE in California, USA. At the same time, DIPE is widely used in the petroleum, tobacco, medicine, environmental protection and chemical synthesis industries due to its advantages such as high octane number, low freezing point, low toxicity, low production cost, good anti-knock performance and low solubility in water. It is a trend to use isopropyl ether as a gasoline additive. While solving the problem of gasoline quality upgrading, it also broadens the application scope of refinery resources. It has become a strong competitor of methyl tert-butyl ether and its demand is increasing day by day. However, in the process of synthesizing isopropyl ether, there is an azeotrope of isopropyl ether and ethanol, which makes it difficult to obtain high-purity isopropyl ether products by conventional separation. Separation of isopropyl ether-ethanol azeotrope is of decisive significance to product purity, economic benefits and environmental pollution control in the production process. However, their boiling points are very close, and it is challenging to separate them by ordinary distillation separation methods. Therefore, the successful, efficient and clean separation of the isopropyl ether-ethanol azeotropic system has great practical significance and industrial application value.

[0003] Chinese patent CN106518618A "A method for continuous extraction and distillation separation of isopropyl alcohol-isopropyl ether azeotropic mixture by mixed solvent" discloses a method for continuous extraction and distillation separation of isopropyl alcohol-isopropyl ether azeotropic mixture. This method uses a low eutectic solvent mixed with a traditional solvent as an extractant, and the mass ratio of the extractant to the feed is 1 to 5:1. Isopropyl ether is extracted from the top of the extractive distillation tower, and isopropyl alcohol is extracted from the top of the solvent recovery tower. The extractant at the bottom of the tower enters the extractive distillation tower for recycling, but the equipment cost of this method is high, the operation and control are more complicated, and higher energy consumption is required.

[0004] Chinese patent CN115353442A "A control method for separating isopropyl alcohol / diisopropyl ether / water azeotropes by azeotropic distillation" discloses a control method for separating isopropyl alcohol / diisopropyl ether / water azeotropes by azeotropic distillation. However, the recovery and treatment of the entrainer in this method are relatively complicated, the design and operation of the azeotropic distillation process need to be more precise and complicated, and the energy consumption is relatively large.

[0005] The invention uses 1-butyl-3-methylimidazolium acetate as an extractant and realizes efficient separation of isopropyl ether-ethanol through liquid-liquid extraction. The essential principle of the separation is to utilize the characteristic that the interaction strength of 1-butyl-3-methylimidazolium acetate to ethanol is greater than that of isopropyl ether. The molar purity of the separated isopropyl ether-ethanol is greater than 99.9%. The method can realize the recycling and reuse of the extractant, reduce the separation cost, and the method has low energy consumption, simple process and flexible operation, and realizes the green separation of azeotropes. [Summary of the invention]

[0006] [Technical issues to be solved]

[0007] The present invention aims to provide a method for separating isopropyl ether / ethanol binary azeotropic mixture by liquid-liquid extraction process. The method adopts green solvent-1-butyl-3-methylimidazole acetate as an extractant to achieve efficient separation of azeotropes. The purpose of the present invention is to provide a device for separating isopropyl ether and ethanol by liquid-liquid extraction-distillation-flash evaporation, and to provide an extractant for separating isopropyl ether-ethanol azeotropic system efficiently and greenly. The green extractant is non-toxic and harmless, and conforms to the concept of energy saving, consumption reduction and emission reduction, and green and sustainable development. This innovation not only achieves efficient separation of isopropyl ether / ethanol binary azeotropic system, but also actively responds to the call for green, low-carbon and sustainable development.

[0008] [Technical solution]

[0009] Aiming at the problem that isopropyl ether-ethanol binary azeotropic mixture is difficult to separate, the present invention proposes a liquid-liquid extraction process for separating isopropyl ether-ethanol using a green extractant, characterized in that the device for implementing the method mainly comprises the following parts: an isopropyl ether extraction tower (E1), an ethanol distillation tower (T1), a flash tank (F1), a flash tank (F2), a reboiler (R1), a heat exchanger (Q1), a condenser (C1), a centrifugal pump (P1), and a valve (V1). The specific implementation steps are as follows:

[0010] (1) The raw material isopropyl ether-ethanol binary azeotrope mixture enters the isopropyl ether extraction tower (E1), and the extractant 1-butyl-3-methylimidazole acetate enters from the upper part of the extraction tower (E1). The top product of the extraction tower passes through a flash tank (F1) to obtain high-purity isopropyl ether.

[0011] (2) The extractant and ethanol are taken out from the bottom of the isopropyl ether extraction tower (E1) and enter the ethanol distillation tower (T1). A small amount of isopropyl ether is taken out from the top of the tower and refluxes into the isopropyl ether extraction tower (E1). The extractant and ethanol are taken out from the bottom of the tower and pass through a flash tank (F2) to obtain high-purity ethanol at the top. The extractant coming out from the bottom is recycled and reused through a mixer.

[0012] The extractant is 1-butyl-3-methylimidazole acetate.

[0013] According to another preferred embodiment of the present invention, it is characterized in that: the operating pressure of the isopropyl ether extraction tower (E1) is 1 atm, the number of plates is 5-15, the feed position is the 8th to 15th plates, the feed position of the extractant is the 2nd to 6th plates, and the feed amount of the extractant is 80 to 150 kmol / h; the feed amount of the raw material is 150 to 280 kmol / h; the operating pressure of the ethanol distillation tower (T1) is 1 atm, the number of plates is 5 to 18, the feed position is the 8th to 15th plates, and the feed amount is 150 to 230 kmol / h.

[0014] According to another preferred embodiment of the present invention, it is characterized in that: the feed flow mass ratio of the extractant to the ethanol-isopropyl ether mixture is 0.3-1.2.

[0015] According to another preferred embodiment of the present invention, it is characterized in that: in the ethanol-isopropyl ether mixture, the molar ratio of ethanol to isopropyl ether is 3:7.

[0016] According to another preferred embodiment of the present invention, it is characterized in that: the top product of the isopropyl ether extraction tower (E1) is passed through a flash tank (F1), and the purity of the isopropyl ether obtained by flash evaporation is higher than 99.9%, and the yield is higher than 99.9%; the top product of the isopropyl ether extraction tower (E1) is passed through a flash tank (F1), and the purity of the ethanol obtained by flash evaporation is higher than 99.9%, and the yield is higher than 99.9%.

[0017] [Beneficial Effects]

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) For the first time, the binary azeotropic system of ethanol and isopropyl ether was effectively separated to obtain two high-purity products.

[0020] (2) This method has a simple process, requires little investment in equipment, uses 1-butyl-3-methylimidazole acetate as an extractant, is green, environmentally friendly and sustainable, and ensures that possible environmental risks are minimized.

[0021] (3) This method achieves no waste of raw materials, the extractant can be recycled, and the amount of extractant used is reduced, thereby reducing energy consumption.

Brief Description of the Drawings

[0022] Attached Figure 1 The present invention is a process flow chart of using [BMIM]AC ionic liquid to extract and separate a binary azeotropic mixture of ethanol and isopropyl ether.

[0023] In the figure, E1-isopropyl ether extraction tower, T1-ethanol distillation tower, F1-flash tank, F2-flash tank, R1-reboiler, C1-condenser, P1-pump, V1-valve. [Specific implementation method]

[0024] Embodiment 1:

[0025] The feed flow rate is 200 kmol / h, the feed temperature is 25°C, the molar fraction of isopropyl ether in the feed stream is 66.43%, and the molar fraction of ethanol is 33.57%. The number of plates of the extractant is 10, the raw material is fed from the second plate, the extractant is fed from the tenth plate, the feed amount of the extractant is 100 kmol / h, and the operating pressure is 1 atm. The purity of isopropyl ether is greater than 99.90% (molar fraction), and the purity of ethanol is greater than 99.90%.

[0026] Embodiment 2:

[0027] The feed flow rate is 200 kmol / h, the feed temperature is 25°C, the molar fraction of isopropyl ether in the feed stream is 53.46%, and the molar fraction of isobutyl alcohol is 46.54%. The number of plates of the extraction tower is 12, the raw material is fed from the 4th plate, the extractant is fed from the 12th plate, the feed amount of the extractant is 120 kmol / h, and the operating pressure is 1 atm. The purity of isopropyl ether is greater than 99.90% (molar fraction), and the purity of ethanol is greater than 99.90%.

[0028] Embodiment 3:

[0029] The feed flow rate is 200 kmol / h, the feed temperature is 25°C, the molar fraction of isopropyl ether in the feed stream is 47.35%, and the molar fraction of isobutyl alcohol is 52.65%. The number of plates of the extraction tower is 14, the raw material is fed from the 6th plate, the extractant is fed from the 14th plate, the feed amount of the extractant is 140 kmol / h, and the operating pressure is 1 atm. The purity of isopropyl ether is greater than 99.90% (molar fraction), and the purity of ethanol is greater than 99.90%.

Claims

1. A liquid-liquid extraction process for separating isopropyl ether-ethanol azeotrope using [BMIM]AC ionic liquid, characterized in that The device used in the process mainly includes the following parts: an isopropyl ether extraction tower (E1), an ethanol distillation tower (T1), a flash tank (F1), a flash tank (F2), a reboiler (R1), a heat exchanger (Q), a condenser (C1), a centrifugal pump (P1), and a valve (V1), wherein the reboiler (R1) is connected to the bottom of the ethanol distillation tower (T1), and the condenser (C1) is connected to the top of the ethanol distillation tower (T1); the liquid-liquid extraction process for separating the binary azeotropic mixture of isopropyl ether and ethanol mainly includes the following steps: (1) The binary mixture of isopropyl ether and ethanol as raw materials enters the isopropyl ether extraction column (E1), and the extractant 1-butyl-3-methylimidazolium acetate enters from the top of the extraction column (E1). Compared with isopropyl ether, this extractant has a higher affinity for ethanol, and the use of the extractant increases the distribution coefficient of the system, thereby facilitating the separation process. Then, the product at the top of the extraction column enters the flash tank (F1), thereby obtaining isopropyl ether that meets the separation standards. (2) The extractant and ethanol are taken out from the bottom of the isopropyl ether extraction tower (E1) and enter the ethanol extraction distillation tower (T1). After passing through the flash tank (F2), high-purity ethanol is obtained at the top, and the extractant coming out from the bottom is recycled through the mixer.

2. According to the method of claim 1, the operating pressure of the isopropyl ether extraction tower (E1) is 1 atm, the number of tower plates is 5 to 15, the feed position is the 7th to 15th plate, and the extractant feed position is the 2nd to 6th plate; the operating pressure of the ethanol distillation tower (T1) is 1 atm.

3. The method according to claim 1, wherein the feed stream is 200 kmol / h, the molar fraction of isopropyl ether is 66.43%, and the molar fraction of ethanol is 33.57%.

4. The method according to claim 1, wherein the extractant feed rate of the isopropyl ether extraction column (E1) is 80 to 110 kmol / h.

5. The method according to claim 1, wherein the purity of the separated isopropyl ether is greater than 99.90% (molar fraction), and the purity of the ethanol is greater than 99.90% (molar fraction).

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