Method and process for separating isopropanol-isooctane by using DMAC (Dimethylacetamide)

Abstract

The invention relates to a method and a process for separating isopropanol-isooctane by using an N, N-dimethylacetamide (DMAC) organic extraction agent. The process is composed of an extractive distillation tower and a solvent recovery tower. According to the method, N, N-dimethylacetamide is used as an extraction agent, isopropanol-isooctane firstly enters an extractive distillation tower for extraction separation, high-purity isopropanol is obtained at the top of the extractive distillation tower, and materials at the bottom of the tower enter a solvent recovery tower for separation. High-purity isooctane is obtained at the top of the solvent recovery tower, and an extracting agent DMAC is obtained at the bottom of the solvent recovery tower. The method has the advantages of low energy consumption, simple process, convenience in operation, greenness, energy conservation, high purity of separated products and the like, and the adopted extracting agent N, N-dimethylacetamide is good in stability, non-toxic, low in corrosivity and environment-friendly.

Description

[Technical field]

[0001] The invention is applicable to the field of separation and purification in the chemical industry, and specifically describes a method for separating isopropanol-isooctane azeotrope by utilizing a distillation tower and a solvent recovery tower. [Background technology]

[0002] Isopropyl alcohol (IPA) and isooctane (ISO) are widely used in the chemical industry. IPA, also known as 2-propanol, can be used to produce chemicals such as acetone, hydrogen peroxide, methyl isobutyl ketone, and can also be used to produce fatty acid isopropyl esters, isopropyl chloroesters, etc. In addition, it can also be used as a solvent, chemical intermediate, medicine, antifreeze and some other industrial products. Isopropyl alcohol can also be used as a solvent, chemical intermediate, medicine, antifreeze and some other industrial products. Due to its stable physical and chemical properties, ISO is often used as a solvent or reaction medium in the fields of petrochemicals, organic synthesis, etc. Therefore, achieving efficient separation of isopropyl alcohol-isooctane azeotrope from fuel oil is of great practical significance to the petrochemical and petrochemical industries to ensure product quality and safety, reduce production costs, and promote the effective use of resources.

[0003] Isopropyl alcohol and isooctane will form azeotropes under normal pressure, and the azeotropic composition is 0.6 (molar fraction) isopropyl alcohol and 0.4 (molar fraction) isooctane. Due to the presence of azeotropes in the mixture, it is impossible to effectively separate isopropyl alcohol and isooctane using a simple distillation method. There are many different azeotropic mixture separation technologies in chemical production, such as PSD, RED, HAD, etc. According to the specific separation needs, the best azeotropic mixture separation process must be determined from the aspects of yield, energy consumption, equipment investment, and operation complexity. In actual operation, the appropriate separation method should be selected according to different azeotropic mixtures, and the process should be optimized to obtain the best separation effect and economic benefits.

[0004] The patent proposes a method for extracting and separating isopropanol and isooctane from fuel oil industrial wastewater by continuous extraction and distillation. The method uses N,N-dimethylacetamide (DMAC) as an extractant for separating isopropanol and isooctane. An extraction distillation tower and a solvent recovery tower are used to separate the isopropanol-isooctane azeotrope and also efficiently recover the extractant. The molar fractions of isopropanol and isooctane separated by this method are both greater than 99.9%. [Summary of the invention]

[0005] [Technical issues to be solved]

[0006] In order to achieve robust control of double-tower efficient separation of binary azeotropic mixture isopropanol-isooctane, the present invention provides a method and process for extracting and separating isopropanol-isooctane by using DMAC.

[0007] [Technical solution]

[0008] The present invention proposes a double-tower extractive distillation method and process for changing the relative volatility characteristics of isopropanol-isooctane azeotropic components using DMAC. By adopting a double-tower system of an extractive distillation tower and a solvent recovery tower, efficient separation of isopropanol and isooctane is achieved, and the proposed control structure can achieve robust control of the process.

[0009] This method is suitable for separating waste liquid with molar fractions of isopropanol and isooctane of 0.7 and 0.3 respectively, and the device used for separating azeotropic system of tert-butyl alcohol and ethyl acetate in this process mainly comprises the following parts:

[0010] An extractive distillation tower (T1), a solvent recovery tower (T2), a condenser (C1), a condenser (C2), a reboiler (H1), a reboiler (H2), a storage tank (D1), a storage tank (D2), and a heat exchanger (T); a raw material (1) enters the extractive distillation tower (T1) from the bottom, an extractant (6) enters the extractive distillation tower (T1) from the top, and the extractive distillation tower (T1) is connected to the condenser (C1), the storage tank (D1) and the reboiler (H1) through pipelines; a material 3 enters the top of the solvent recovery tower (T2), is connected to the condenser (C2), the storage tank (D2) and the reboiler (H2) through pipelines, is connected to the heat exchanger (T) through pipeline 5, and finally the solvent is recovered and connected to the extractive distillation tower (T).

[0011] The steady-state process of the method and process for separating isopropanol-isooctane using N,N-dimethylacetamide (DMAC) is as follows:

[0012] (1) The waste liquid with molar fractions of isopropanol and isooctane of 0.7 and 0.3 enters the extractive distillation tower (T1) through feed 1, and the extractant N,N-dimethylacetamide (DMAC) enters the extractive distillation tower (T1) through feed 6. After extraction and separation, the waste liquid is divided into two streams;

[0013] (2) One stream of the output enters the storage tank (D1) through the condenser (C1) and is distilled out from pipeline 2 as isopropanol with a purity greater than 0.9999. The other stream is distilled out from pipeline 3 through the reboiler (H1) as a mixed solution of isopropanol and DMAC;

[0014] (3) The mixed solution enters the solvent recovery tower (T2) through pipeline 3, and the isopropanol and DMAC are separated through the tower. The isopropanol with a purity greater than 0.999 enters the storage tank (D2) through the condenser (C2) and flows out from the pipeline 4; the DMAC with a purity greater than 0.999 is distilled from the pipeline 5 through the reboiler (H2) and enters the heat exchanger (T). After changing the pressure and temperature, the extractant is refluxed and re-enters the extractive distillation tower (T1) for utilization.

[0015] The operating pressure of the extractive distillation tower (T1) is 1 atm, the theoretical number of plates is 46, the raw material feed position is the 40th plate, and the extraction feed position is the 5th plate; the operating pressure of the solvent recovery tower (T2) is 1 atm, the theoretical number of plates is 13, and the feed position is the 12th plate.

[0016] The top temperature of the extractive distillation tower (T1) is 82.05°C, the bottom temperature is 153.31°C, the top temperature of the solvent recovery tower (T2) is 117.60°C, the bottom temperature is 160.85°C

[0017] The control scheme can realize process control. After separation, the purity of isooctane and isopropanol products can be maintained at 0.999 (molar fraction), and the recovery concentration of the extractant DMAC is 0.999 (molar fraction).

[0018] [Beneficial Effects]

[0019] (1) The present invention uses DMAC as an extractant. DMAC has good stability, is non-toxic, has low corrosiveness and is environmentally friendly, can realize waste resource utilization and reduce environmental pollution.

[0020] (2) The present invention can achieve efficient separation of isopropanol-isooctane binary azeotropic mixture.

[0021] (3) The present invention uses only two towers, has low cost, simple process, flexible operation, and greater environmental and economic benefits.

Brief Description of the Drawings

[0022] Attached Figure 1 Figure 2 is a process diagram for separating isopropanol-isooctane using DMAC.

[0023] In the figure, T1-extraction distillation tower; T2-solvent recovery tower; C1-condenser, C2-condenser; H1-reboiler, H2-reboiler, D1-storage tank, D2-storage tank, T-heat exchanger; numbers represent various logistics. [Specific implementation method]

[0024] The following is further described in conjunction with the accompanying drawings, which does not limit the scope of the present invention.

[0025] Implementation:

[0026] The feed temperature is 40°C, the feed flow rate is 100 kmol / h, the pressure is 1 atm (absolute pressure), and the feed contains 0.3 isooctane and 0.7 isopropanol (molar fraction). The number of theoretical plates is 46, the feed position of the raw material is the 40th plate, the extractant DMAC enters the extractive distillation tower (T1) from the 5th plate, the operating pressure is 1 atm (absolute pressure), the tower top temperature is 82.05°C, and the tower bottom temperature is 153.31°C; the solvent recovery tower operating pressure is 1 atm (absolute pressure), the number of theoretical plates is 13, the extractant and isooctane enter the solvent recovery tower (T2) from the 12th plate, the tower top temperature is 117.59°C, and the tower bottom temperature is 160.86°C. After separation, the molar fraction of isopropanol is 0.9999, and the molar fraction of isooctane is 0.999.

Claims

1. A method and process for separating isopropyl alcohol and isooctane using N,N-dimethylacetamide (DMAC), wherein the device for separating the isopropyl alcohol and isooctane binary azeotropic system mainly comprises the following parts: an extractive distillation tower (T1), a solvent recovery tower (T2), a condenser (C1), a condenser (C2), a reboiler (H1), a reboiler (H2), a storage tank (D1), a storage tank (D2), and a heat exchanger (T); a raw material (1) is extracted from a distillation tower (T1), a solvent recovery tower (T2), a condenser (C1), a condenser (C2), a reboiler (H1), a reboiler (H2), a storage tank (D1), a storage tank (D2), and a heat exchanger (T); The extractant (6) enters from the bottom of the extractive distillation tower (T1), and the extractive distillation tower (T1) is connected to the condenser (C1), the storage tank (D1) and the reboiler (H1) through pipelines; the material 3 enters from the top of the solvent recovery tower (T2), and is connected to the condenser (C2), the storage tank (D2) and the reboiler (H2) through pipelines, and is connected to the heat exchanger (T) through pipeline 5, and finally the solvent is recovered and connected to the extractive distillation tower (T).

2. According to claim 1, it is characterized in that A method and process for separating isopropyl alcohol-isooctane using N,N-dimethylacetamide (DMAC) is as follows: The waste liquid with molar fractions of isopropanol and isooctane of 0.7 and 0.3 enters the extractive distillation tower (T1) through feed 1, and the extractant N, N-dimethylacetamide (DMAC) enters the extractive distillation tower (T1) through feed 6. After extraction and separation, the waste liquid is divided into two streams. One stream of the output enters the storage tank (D1) through the condenser (C1) and is distilled from the pipeline 2, which is isopropanol with a purity greater than 0.9999. Another stream is distilled from the pipeline 3 through the reboiler (H1), which is a mixed solution of isopropanol and DMAC; the mixed solution enters the solvent recovery tower (T2) through the pipeline 3, and the isopropanol and DMAC are separated through the tower. The isopropanol with a purity greater than 0.999 enters the storage tank (D2) through the condenser (C2) and flows out from the pipeline 4; the DMAC with a purity greater than 0.999 is distilled from the pipeline 5 through the reboiler (H2), enters the heat exchanger (T), and after changing the pressure and temperature, the extractant is refluxed and re-enters the extractive distillation tower (T1) for utilization. The operating pressure of the extractive distillation tower (T1) is 1 atm, the theoretical number of plates is 46, the raw material feed position is the 40th plate, and the extraction feed position is the 5th plate; the operating pressure of the solvent recovery tower (T2) is 1 atm, the theoretical number of plates is 13, and the feed position is the 12th plate. The top temperature of the extractive distillation tower (T1) was 82.05°C, and the bottom temperature was 153.31°C. The top temperature of the solvent recovery tower (T2) was 117.60°C, and the bottom temperature was 160.85°C.

3. According to claims 1-2, it is characterized in that: After separation, the purity of isooctane and isopropanol products can be maintained at 0.999 (molar fraction), and the recovery concentration of the extractant DMAC is 0.999 (molar fraction).

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