A method for separating diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant

Abstract

The present invention relates to a method for separating diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant. The method utilizes a diethoxymethane-ethanol and toluene-ethanol azeotropic system to change the relative volatility between molecules as a mixed extractant is added. The method is operated by a distillation tower (T1), a distillation tower (T2) and a distillation tower (T3) to achieve efficient separation of a ternary mixture. The mass fraction of diethoxymethane after separation is greater than 99.99%, the mass fraction of ethanol is greater than 99.99%, and the mass fraction of toluene is greater than 99.99%. The present invention solves the problem that the azeotropic system is difficult to separate using ordinary distillation. The method is flexible in operation, economical and environmentally friendly, and can achieve effective separation of a ternary azeotropic mixture by three towers.

Description

Technical field

[0001] The invention belongs to the field of chemical separation and purification, and particularly relates to a method for separating diethoxymethane-ethanol and toluene-ethanol azeotropes by extractive distillation. [Background Technology]

[0002] Diethoxymethane, ethanol, and toluene are widely used in healthcare, food processing, agriculture, the chemical industry, and other fields. Diethoxymethane, due to its excellent stability, low boiling point, high oxygen content, and immiscibility with water, is widely used in the industrial sector. It can be used as a fuel additive to increase octane rating and reduce CO emissions, and can also be used as a blended fuel or organic solvent. Ethanol has low-carbon potential and is considered one of the most promising biofuels. Although toluene has environmental impacts and is toxic to humans, its role as a coating and dye is not negligible. Toluene is a common raw material and solvent found throughout industry.

[0003] In the production of indoxacarb and other medical processes, intermediate products containing diethoxymethane, ethanol, and toluene are generated. Diethoxymethane and ethanol, and toluene and ethanol, form azeotropes, with boiling points of 75.08°C (56.34 wt% diethoxymethane, 43.66 wt% ethanol) and 76.86°C (31.92 wt% toluene, 68.08 wt% ethanol), respectively. Separating and recovering diethoxymethane, ethanol, and toluene reduces production costs and further reduces emissions. Due to the presence of azeotropes in the mixture, simple distillation methods cannot effectively separate them, necessitating specialized distillation methods.

[0004] The present invention separates a ternary mixture of diethoxymethane, ethanol, and toluene by utilizing the property that the relative volatility of the azeotropic composition of diethoxymethane-ethanol and toluene-ethanol changes toward easier separation upon addition of a mixed extractant. Specifically, the present invention employs three distillation towers for separation and purification, and a corresponding process scheme is designed to achieve efficient separation of the mixture. The present invention is applicable to mixtures of diethoxymethane, ethanol, and toluene, offers 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 present invention aims to provide a method for separating a mixture of diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant, thereby realizing 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 diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant. Utilizing the characteristic that the relative volatility of the azeotropic composition of diethoxymethane-ethanol and toluene-ethanol azeotropes changes toward a direction that makes separation easier with the addition of the mixed extractant, extractive distillation is performed using a three-tower distillation method. The proposed process flow can achieve efficient separation of a ternary mixture of diethoxymethane, ethanol and toluene.

[0009] The present invention proposes a method for separating diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant, characterized in that the device for separating the azeotropic system of diethoxymethane, ethanol and toluene mainly comprises the following parts:

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

[0011] The invented method for extractive distillation separation of diethoxymethane, ethanol and toluene using a mixed extractant mainly comprises the following steps:

[0012] (1) A raw material mixture of diethoxymethane, ethanol and toluene and a mixed extractant are added to a distillation tower (T1) from the lower part and the upper part of the tower, respectively. In the distillation tower (T1), ethanol is separated. A portion 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 portion is passed as feed to the distillation tower (T2); the ethanol is condensed in a condenser (CL1) and enters a tower top storage tank (C1), a portion of which is refluxed and the other portion is extracted from the top of the distillation tower (T1).

[0013] (2) In the distillation tower (T2), diethoxymethane is separated. 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 distillation tower (T3); the diethoxymethane is condensed in the condenser (CL2) and enters the tower 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) Toluene is separated in the distillation tower (T3). A portion of the bottom stream of the distillation tower (T3) is returned to the distillation tower (T3) after heat exchange in the reboiler (H3), and a portion of the reflux is first passed through a centrifugal pump (P2) and then through a cooler (COL) into the mixer (MIX); the toluene is condensed in the condenser (CL3) and enters the tower top storage tank (C3), a portion of which is refluxed and the other portion is extracted from the top of the distillation tower (T3).

[0015] According to another preferred embodiment of the present invention, the distillation tower (T1) operates at a pressure of 1 atm and has a theoretical number of 44 to 59 plates; the distillation tower (T2) operates at a pressure of 1 atm and has a theoretical number of 52 to 100 plates; and the distillation tower (T3) operates at a pressure of 1 atm and has a theoretical number of 22 to 40 plates. 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 feed flow mass ratio of the mixed extractant to the mixture of diethoxymethane, ethanol and toluene is 0.8 to 0.9.

[0017] According to another preferred embodiment of the present invention, it is characterized in that in the mixture of diethoxymethane, ethanol and toluene, 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%.

[0018] 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. After separation, the purity of diethoxymethane is greater than 99.98% (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 at the bottom of the distillation tower 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 mixed extractant extraction distillation method is used to achieve efficient separation of the ternary azeotropic mixture of diethoxymethane, ethanol and toluene.

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

[0023] (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

[0024] Figure 1 The figure is a process flow chart for separating a mixture of diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant.

[0025] In the figure, the mixed extractant and the raw material are respectively introduced into the distillation tower (T1); in the distillation tower (T1), ethanol gas flows upward and the organic mixed liquid flows downward; ethanol product is obtained at the top of the distillation tower (T1), and the organic mixed liquid in the bottom of the distillation tower (T1) is introduced into the distillation tower (T2) through a centrifugal pump (P1); in the distillation tower (T2), diethoxymethane gas flows upward and the organic mixed liquid flows downward; diethoxymethane product is obtained at the top of the distillation tower (T2) , the organic matter mixed liquid in the bottom of the distillation tower (T2) is introduced into the distillation tower (T3); in the distillation tower (T3), toluene gas flows upward and the mixed extractant flows downward; a toluene product is obtained at the top of the distillation tower (T3), and a mixed extractant is obtained in the bottom of the distillation tower (T3); the mixed extractant obtained in the bottom of the distillation tower (T3) first passes through a centrifugal pump (P2), then passes through a cooler (COL) to reach a suitable condition, and is mixed with a make-up extractant flow through a mixer (MIX) and then recycled.

[0026] In the figure, T1-distillation tower; T2-distillation tower; T3-distillation tower; CL1-condenser; CL2-condenser; CL3-condenser; COL-cooler; H1-reboiler; H2-reboiler; H3-reboiler; P1-centrifugal pump; P2-centrifugal pump; C1-tower top storage tank; C2-tower top storage tank; C3-tower top storage tank; MIX-mixer. [Specific implementation method]

[0027] The following is further described with reference to the accompanying drawings, which does not limit the scope of the present invention.

[0028] Example 1:

[0029] The feed flow rate is 5000 kg / h, the feed temperature is 40°C, and the pressure is 2 atm (absolute pressure). The mass fraction of diethoxymethane in the feed stream is 73.32%, the mass fraction of ethanol is 13.07%, and the mass fraction of toluene is 13.61%. The extractant feed flow rate is 4460.94 kg / h, the feed temperature is 40°C, and the pressure is 2 atm (absolute pressure). The operating pressure of the distillation tower (T1) is 1 atm (absolute pressure), the number of tower plates is 49, the feed positions are the 19th and 41st plates respectively, the tower top temperature is 78.31°C, and the tower bottom temperature is 106.76°C; the operating pressure of the distillation tower (T2) is 1 atm (absolute pressure), the number of tower plates is 99, the feed position is the 79th plate, the tower top temperature is 87.60°C, and the tower bottom temperature is 160.11°C; the operating pressure of the distillation tower (T3) is 1 atm (absolute pressure), the number of tower plates is 39, the feed position is the 12th plate, the tower top temperature is 110.67°C, and the tower bottom temperature is 184.04°C; after separation, the concentration of the diethoxymethane product is greater than 99.99%, the concentration of the ethanol product is greater than 99.99%, and the concentration of the toluene product is greater than 99.99%.

[0030] Example 2:

[0031] The feed flow rate is 5500 kg / h, the feed temperature is 40°C, and the pressure is 2 atm (absolute pressure). The mass fraction of diethoxymethane in the feed stream is 70.00%, the mass fraction of ethanol is 15.00%, and the mass fraction of toluene is 15.00%. The extractant feed flow rate is 5000 kg / h, the feed temperature is 40°C, and the pressure is 2 atm (absolute pressure). The operating pressure of the distillation tower (T1) is 1 atm (absolute pressure), the number of tower plates is 59, the feed positions are the 12th and 52nd plates respectively, the tower top temperature is 78.31°C, and the tower bottom temperature is 107.83°C; the operating pressure of the distillation tower (T2) is 1 atm (absolute pressure), the number of tower plates is 60, the feed position is the 40th plate, the tower top temperature is 87.60°C, and the tower bottom temperature is 157.78°C; the operating pressure of the distillation tower (T3) is 1 atm (absolute pressure), the number of tower plates is 40, the feed position is the 20th plate, the tower top temperature is 110.67°C, and the tower bottom temperature is 184.06°C; after separation, the concentration of the diethoxymethane product is greater than 99.99%, the concentration of the ethanol product is greater than 99.99%, and the concentration of the toluene product is greater than 99.99%.

[0032] Example 3:

[0033] The feed flow rate is 6000 kg / h, the feed temperature is 40°C, and the pressure is 2 atm (absolute pressure). The mass fraction of diethoxymethane in the feed stream is 75.00%, the mass fraction of ethanol is 14.00%, and the mass fraction of toluene is 11.00%. The extractant feed flow rate is 5000 kg / h, the feed temperature is 40°C, and the pressure is 2 atm (absolute pressure). The operating pressure of the distillation tower (T1) is 1 atm (absolute pressure), the number of tower plates is 44, the feed positions are the 9th and 38th plates respectively, the tower top temperature is 78.31°C, and the tower bottom temperature is 105.45°C; the operating pressure of the distillation tower (T2) is 1 atm (absolute pressure), the number of tower plates is 52, the feed position is the 34th plate, the tower top temperature is 87.56°C, and the tower bottom temperature is 161.16°C; the operating pressure of the distillation tower (T3) is 1 atm (absolute pressure), the number of tower plates is 22, the feed position is the 11th plate, the tower top temperature is 110.66°C, and the tower bottom temperature is 183.56°C; after separation, the concentration of the diethoxymethane product is greater than 99.98%, the concentration of the ethanol product is greater than 99.93%, and the concentration of the toluene product is greater than 99.95%.

Claims

1. A method for separating diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant, characterized in that The device for implementing the method includes the following parts: Distillation tower (T1), distillation tower (T2), distillation tower (T3), cooler (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), centrifugal pump (P1), centrifugal pump (P2); the bottom of the distillation tower (T1) enters the distillation tower (T2) through the centrifugal pump (P1), and at the top of the distillation tower (T1) High-purity product ethanol is extracted, and the bottom flow of the distillation tower (T2) enters the distillation tower (T3). High-purity product diethoxymethane is extracted from the top flow of the distillation tower (T2). The high-purity mixed extractant flowing out of the bottom of the distillation tower (T3) first passes through a centrifugal pump (P2) and then enters a mixer (MIX) through a cooler (COL). The recovered mixed extractant and the replenished fresh mixed extractant pass through the mixer (MIX) and enter the distillation tower (T1) through the top of the distillation tower (T1). The components to be separated enter through the bottom of the distillation tower (T1); (1) A diethoxymethane-ethanol-toluene mixture enters the bottom of a distillation tower (T1), and an extractant enters the top of the distillation tower (T1). After effective contact extraction and separation, a high-purity product ethanol is extracted from the top flow of the distillation tower (T1). The diethoxymethane-toluene-extractant mixture in the raffinate phase flows out from the bottom of the distillation tower (T1) and enters the distillation tower (T2) through a centrifugal pump (P1); (2) The diethoxymethane-toluene-extractant mixture enters the bottom of the distillation tower (T2). After effective contact separation, the high-purity diethoxymethane product is extracted from the top flow of the distillation tower (T2). The toluene-extractant mixture in the raffinate phase flows out from the bottom of the distillation tower (T2) and enters the distillation tower (T3); (3) The toluene-extractant mixture enters the bottom of the distillation tower (T3). After effective contact separation, high-purity product toluene is extracted from the top flow of the distillation tower (T3). The high-purity mixed extractant flows out from the bottom of the distillation tower (T3). The mixed extractant is pressurized by the centrifugal pump (P2) and enters the cooler (COL) for cooling. Then, it enters the mixer (MIX) and enters the distillation tower (T1) together with the replenished fresh mixed extractant for recycling. The mixed extractant is a mixed solution of 90% (mass fraction) of p-diethylbenzene and 10% (mass fraction) of o-dichlorobenzene.

2. The method for separating diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant according to claim 1, wherein: The operating pressure of the distillation tower (T1) is 0.8-1.2 atm, and the number of theoretical plates is 44-59; the operating pressure of the distillation tower (T2) is 0.8-1.2 atm, and the number of theoretical plates is 52-100; the operating pressure of the distillation tower (T3) is 0.8-1.2 atm, and the number of theoretical plates is 22-40, and the feed temperature of the mixed extractant is 40°C.

3. The method for separating diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant according to claim 1, wherein: The feed flow mass ratio of the mixed extractant to the mixture of diethoxymethane, ethanol and toluene is 0.8 to 0.

9.

4. The method for separating diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant according to claim 1, wherein: In the mixed liquid of diethoxymethane, ethanol and toluene, the mass fraction of diethoxymethane is 74%, the mass fraction of ethanol is 13% and the mass fraction of toluene is 13%.

5. The method for separating diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant according to claim 1, wherein: 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 distillation tower T3 is greater than 99.90% (mass fraction).

Images