Method for separating cyclohexane, isopropanol and water by coupling extractive distillation with pervaporation
Through the extraction and rectification coupled permeability gasification technology, the problem of separation of ternary azeotropic mixtures of cyclohexane, isopropanol and water is solved, and efficient and economical separation effect is achieved. The product purity and extraction agent recovery rate are both high standards.
Patent Information
- Application Number
- CN202410868708.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-01
- Publication Date
- 2024-12-13
AI Technical Summary
The prior art cannot effectively separate the ternary azeotropic mixture of cyclohexane, isopropanol and water produced in the rapeseed oil production process, resulting in high separation costs and difficult to achieve.
Using the extraction and distillation coupled permeation gasification method, a process scheme was designed to realize cyclohexane and isopropyl alcohol through two distillation towers and one permeation gasification membrane separation device, combined with extraction and permeation gasification technology. , efficient separation of water.
It has achieved efficient separation of cyclohexane, isopropanol and water. After separation, the purity of the product reaches more than 99.87%, and the recovery purity of the extractant also reaches more than 99.85%. It has simple process, flexible operation, economical and environmentally friendly.
Smart Images
Figure CN119118773A_ABST
Abstract
Description
[Technical field]
[0001] The invention belongs to the field of chemical separation and purification, and in particular relates to a method for separating azeotropes of cyclohexane, isopropanol and water by extractive distillation. [Background technology]
[0002] Cyclohexane and isopropanol are widely used in the fields of chemical industry, medicine, pesticide, paint, coating, adhesive, plastic, rubber, etc. Cyclohexane is colorless, odorless, volatile, has excellent solubility and low toxicity, and is widely used as a solvent and cleaning agent; it can be used to clean mechanical parts, utensils and chemical equipment, and can also be used as a synthetic raw material for other compounds. Isopropanol is an important organic solvent and is also used in medicine and chemical synthesis. Due to its flammability and volatility, it is also used as a fuel additive and a component of sprays.
[0003] In the production process of rapeseed oil, a large amount of mixed solution composed of cyclohexane, isopropanol and water will be produced. Among them, cyclohexane, isopropanol and water can form three binary azeotropes of isopropanol-cyclohexane, isopropanol-water and cyclohexane-water respectively, and the boiling points are 69.18℃ (31.41wt% isopropanol, 668.59wt% cyclohexane), 80.18℃ (87.27wt% isopropanol, 12.73wt% water) and 62.17℃ (90.93wt% cyclohexane, 9.07wt% water). Separation and recovery of cyclohexane, isopropanol and water can reduce production costs and further reduce emissions. Due to the presence of azeotropes in the mixture, it is impossible to achieve effective separation using a simple distillation method, so a special distillation method is required.
[0004] The present invention utilizes the characteristics of high flexibility and low energy consumption of extractive distillation, combines pervaporation with extractive distillation, and separates cyclohexane, isopropanol, and water. Specifically, the present invention uses two distillation towers combined with a pervaporation membrane separation to perform separation and purification, designs a corresponding process scheme, and realizes efficient separation of the mixture. The present invention is applicable to a mixture of cyclohexane, isopropanol, and water, has flexible operation, and can realize effective separation of a ternary azeotropic mixture through extractive distillation. [Summary of the invention]
[0005] [Technical issues to be solved]
[0006] The purpose of the present invention is to provide a method for separating a mixture of cyclohexane, isopropanol and water by using extractive distillation coupled with pervaporation, so as to realize a process design for efficiently separating a ternary azeotropic mixture by extractive distillation.
[0007] [Technical solution]
[0008] The present invention proposes a method for separating cyclohexane, isopropanol and water by using extractive distillation coupled with pervaporation. The extractive distillation has high flexibility and low energy consumption, and pervaporation can recover and reuse the entrainer. A distillation tower is coupled with pervaporation to perform extractive distillation. The proposed process can achieve efficient separation of a ternary mixture of cyclohexane, isopropanol and water.
[0009] The present invention proposes a method for separating cyclohexane, isopropanol and water by using extractive distillation coupled with pervaporation, which is characterized in that the device for separating the azeotropic system of cyclohexane, isopropanol and water mainly comprises the following parts:
[0010] Distillation tower (T1), distillation tower (T2), membrane separation device (M1), condenser (COL), tower top storage tank (C1), tower top storage tank (C2), reboiler (H1), reboiler (H2), condenser (CL1), condenser (CL2), condenser (CL3); the supplemented fresh mixed extractant and the circulating extractant are connected to the distillation tower (T1) through a pipeline; the distillation tower (T1) is connected to the distillation tower (T2) through a pipeline; the distillation tower (T2) is connected to the distillation tower (T1) through a pipeline. The membrane separation device (M1) is connected to the distillation tower (T1) through a pipeline through a condenser (COL); the condenser (CL1) is connected to the distillation tower (T1) and the tower top storage tank (C1), the condenser (CL2) is connected to the distillation tower (T2) and the tower top storage tank (C2), and the condenser (CL3) is connected to the membrane separation device (M1); the reboiler (H1) and the reboiler (H2) are connected to the distillation tower (T1) and the distillation tower (T2) respectively;
[0011] The invented method for separating cyclohexane, isopropanol and water by extractive distillation coupled with pervaporation mainly comprises the following steps:
[0012] (1) A raw material mixture of cyclohexane, isopropanol and water and a recovered extractant ethylene glycol are added to a distillation tower (T1) from a lower part and an upper part respectively. Cyclohexane is separated in the distillation tower (T1). A part of the bottom stream of the distillation tower (T1) is returned to the distillation tower (T1) after heat exchange in a reboiler (H1), and a part is passed as a feed to a distillation tower (T2); the cyclohexane is condensed in a condenser (CL1) and enters a tower top storage tank (C1), a part of which is refluxed and the other part is extracted from the top of the distillation tower (T1).
[0013] (2) In the distillation tower (T2), separation of isopropyl alcohol is achieved. A portion of the bottom stream of the distillation tower (T2) is returned to the distillation tower (T2) after heat exchange in the reboiler (H2), and a portion is passed as feed to the membrane separation device (M1); the isopropyl alcohol is condensed in the condenser (CL2) and enters the top storage tank (C2), a portion of which is refluxed and the other portion is extracted from the top of the distillation tower (T2).
[0014] (3) In the membrane separation device (M1), water separation is achieved. The bottom flow of the membrane separation device (M1) is passed through the condenser (COL) into the distillation tower (T1), and water is extracted from the top of the membrane separation device (M1).
[0015] According to another preferred embodiment of the present invention, it is characterized in that: the operating pressure of the distillation tower (T1) is 1 atm, and the number of theoretical plates is 7 to 9; the operating pressure of the distillation tower (T2) is 1 atm, and the number of theoretical plates is 76 to 78; the operating pressure of the membrane separation device (M1) is 1 atm, and the membrane area is 47.5 m 2 The feed temperature of the extractant was 40°C.
[0016] According to another preferred embodiment of the present invention, it is characterized in that in the mixture of cyclohexane, isopropanol and water, the molar fraction of cyclohexane is 70% to 75%, the molar fraction of isopropanol is 15% to 20%, and the molar fraction of water is 5% to 10%.
[0017] According to another preferred embodiment of the present invention, it is characterized in that: the process flow can achieve clean and efficient separation of mixed substances, the purity of cyclohexane after separation is greater than 99.87% (molar fraction), the purity of isopropanol is greater than 99.49% (molar fraction), the purity of water is greater than 99.91% (molar fraction), and the purity of the recycled extractant ethylene glycol is greater than 99.85% (molar fraction).
[0018] [Beneficial Effects]
[0019] The present invention has the following beneficial effects:
[0020] (1) The beneficial effect of the present invention is to efficiently separate the ternary azeotropic mixture of cyclohexane, isopropanol and water by using extractive distillation coupled with pervaporation.
[0021] (2) The designed process flow can achieve economical and clean separation of the mixture.
[0022] (3) The present invention is clean and efficient, economical and environmentally friendly, has a simple process and is flexible to operate.
Brief Description of the Drawings
[0023] Attached Figure 1 Schematic diagram of the method for separating cyclohexane, isopropanol and water using extractive distillation coupled with pervaporation.
[0024] In the figure, T1-distillation tower; T2-distillation tower; M1-membrane separation device; CL1-condenser; CL2-condenser; CL3-condenser; COL-condenser; H1-reboiler; H2-reboiler; C1-tower top storage tank; C2-tower top storage tank; numbers represent each logistics. [Specific implementation method]
[0025] The following is further described in conjunction with the accompanying drawings, which does not limit the scope of the present invention.
[0026] Embodiment 1:
[0027] The feed flow rate is 100 kmol / h, the feed temperature is 40° C., the pressure is 1 atm (absolute pressure), the molar fraction of isopropanol in the feed stream is 18.5%, the molar fraction of cyclohexane is 74%, and the molar fraction of water is 7.5%. The operating pressure of the distillation tower (T1) is 1atm (absolute pressure), the feed flow rate of the extractant is 43kmol / h, the feed temperature is 40°C, the pressure is 1atm (absolute pressure), the number of tower plates is 8, the feed positions are the 2nd and 5th plates respectively, the tower top temperature is 80.23°C, and the tower bottom temperature is 101.51°C; the operating pressure of the distillation tower (T2) is 1atm (absolute pressure), the feed flow rate of the extractant is 46kmol / h, the feed temperature is 40°C, the pressure is 1atm (absolute pressure), the number of tower plates is 77, the feed positions are the 7th and 66th plates respectively, the tower top temperature is 81.93°C, and the tower bottom temperature is 170.34°C; after separation, the isopropanol product concentration is greater than 99.96%, the cyclohexane product concentration is greater than 99.84%, and the water product concentration is greater than 99.91%.
[0028] Embodiment 2:
[0029] The feed flow rate is 100 kmol / h, the feed temperature is 40° C., the pressure is 1 atm (absolute pressure), the molar fraction of isopropanol in the feed stream is 18.5%, the molar fraction of cyclohexane is 74%, and the molar fraction of water is 7.5%. The operating pressure of the distillation tower (T1) is 1atm (absolute pressure), the feed flow rate of the extractant is 45kmol / h, the feed temperature is 40°C, the pressure is 1atm (absolute pressure), the number of tower plates is 9, the feed positions are the 3rd and 7th plates respectively, the tower top temperature is 80.46°C, and the tower bottom temperature is 100.28°C; the operating pressure of the distillation tower (T2) is 1atm (absolute pressure), the feed flow rate of the extractant is 48kmol / h, the feed temperature is 40°C, the pressure is 1atm (absolute pressure), the number of tower plates is 76, the feed positions are the 6th and 65th plates respectively, the tower top temperature is 81.66°C, and the tower bottom temperature is 170.16°C; after separation, the isopropanol product concentration is greater than 99.87%, the cyclohexane product concentration is greater than 99.5%, and the water product concentration is greater than 99.91%.
Claims
1. A method for separating cyclohexane, isopropanol and water by extractive distillation coupled with pervaporation, characterized in that The device for implementing the method mainly includes the following parts: Distillation tower T1, distillation tower T2, membrane separation device M1, condenser COL, overhead storage tank C1, overhead storage tank C2, reboiler H1, reboiler H2, condenser CL1, condenser CL2, condenser CL3; The bottom of the distillation tower T1 enters the distillation tower T2 through a pipeline; the bottom of the distillation tower T2 enters the distillation tower membrane separation device M1 through a pipeline; the bottom of the membrane separation device M1 enters the distillation tower T1 through the condenser COL; the recovered extractant enters the distillation tower T1 through the top of the distillation tower T1, and the components to be separated enter through the bottom of the distillation tower T1; The above device is used to carry out a method for separating cyclohexane, isopropanol and water by extractive distillation coupled with pervaporation: (1) A mixture of cyclohexane, isopropanol and water enters from the bottom of the distillation tower T1, and an extractant enters from the top of the distillation tower T1. After effective contact, extraction and separation, cyclohexane flows out from the top of the distillation tower T1, and isopropanol, water and the extractant flow out from the bottom of the distillation tower T1 and enter the distillation tower T2; (2) After distillation and separation in the distillation tower T2, isopropanol flows out of the top stream, and water and the extractant flow out of the bottom stream of the distillation tower T2 and enter the membrane separation device M1; (3) After membrane separation in the membrane separation device M1, water flows out of the top stream, and the stream at the bottom of the membrane separation device M1 is almost pure extractant. The extractant enters the cooler COL to cool down, and then enters the distillation tower T1 for recycling; The extractant is ethylene glycol solution.
2. The method for separating cyclohexane, isopropanol and water by extractive distillation coupled with pervaporation according to claim 1, characterized in that: The operating pressure of the distillation tower (T1) is 1 atm, and the number of theoretical plates is 7-9; the operating pressure of the distillation tower (T2) is 1 atm, and the number of theoretical plates is 76-78; the operating pressure of the membrane separation device (M1) is 1 atm, and the membrane area is 47.5m. The feed temperature of the extractant is 40°C.
3. The method for separating cyclohexane, isopropanol and water by extractive distillation coupled with pervaporation according to claim 1, characterized in that: In the cyclohexane, isopropanol and water mixed liquid, the molar fraction of cyclohexane is 70% to 75%, the molar fraction of isopropanol is 15% to 20%, and the molar fraction of water is 5% to 10%.
4. The method for separating cyclohexane, isopropanol and water by extractive distillation coupled with pervaporation according to claim 1, characterized in that: The purity of the cyclohexane after separation is greater than 99.87% (molar fraction), the purity of the isopropanol is greater than 99.49% (molar fraction), the purity of the water is greater than 99.91% (molar fraction), and the purity of the extractant ethylene glycol recovered and reused at the bottom of the membrane separation device M1 is greater than 99.85% (molar fraction).