Method for separating diisopropyl ether, isopropanol and water by mixed extractant extractive distillation process combined with pre-concentration function

Abstract

The invention relates to a method for separating diisopropyl ether, isopropanol and water by a mixed extractant extractive distillation process combined with a pre-concentration function, by utilizing the characteristic that the relative volatility of azeotropic composition of a diisopropyl ether-isopropanol-water mixture is changed towards the direction of easier separation along with the addition of a mixed extraction agent, a pre-concentration tower (PDC), a rectifying tower (EDC1), a rectifying tower (EDC2) and a solvent recovery tower (SRC) are operated, efficient separation of a ternary mixture is realized, the purity of separated diisopropyl ether is greater than 99.90% (mass fraction), and the purity of the separated diisopropyl ether is greater than 99.90% (mass fraction). The purity of isopropanol is greater than 99.90% (mass fraction), the purity of water is greater than 99.90% (mass fraction), and the purity of the mixed extractant recovered from the bottom of the rectifying tower SRC is greater than 99.90% (mass fraction). The method solves the problems that the diisopropyl ether-isopropanol-water mixture with high water content is high in consumption, difficult to separate and the like when being subjected to common rectification, is flexible to operate, economical and environment-friendly, and can realize effective separation of the ternary azeotropic mixture through four towers.

Description

Technical Field

[0001] The present invention belongs to the fields of clean chemical processes and separation and purification, and particularly relates to a method for separating diisopropyl ether, isopropanol, and water by an extractive distillation process using a mixed extractant combined with a preconcentration function.

Background Art

[0002] Isopropanol is an important chemical raw material and is widely used in modern chemical production. It is often used as a chemical intermediate and organic solvent in industrial production. In addition, it is also an effective solvent and raw material for the preparation of drugs. For example, isopropanol is not only a good solvent for the production of isopropylamine or isopropyl acetate but also a chemical intermediate in the production process. Isopropanol is mainly produced by the propylene hydration process and the propylene hydrogenation process. Whether it is direct hydration or indirect hydration, diisopropyl ether is produced as a by-product. Similarly, side reactions inevitably occur during the propylene hydrogenation process, and propylene condensation produces diisopropyl ether as a by-product. Diisopropyl ether as a by-product is a good solvent and can also be used as an entrainer for separating n-propanol and water. In addition, the high octane number and strong stability of diisopropyl ether make it a good gasoline additive.

[0003] During the preparation of isopropanol, industrial wastewater containing diisopropyl ether as a by-product is generated. Among them, the concentration of water accounts for the vast majority. Diisopropyl ether, isopropanol, and water will form four azeotropic substances, and the azeotropic points are 65.97 °C (85.37 wt% diisopropyl ether, 14.63 wt% isopropanol), 62.21 °C (95.34 wt% diisopropyl ether, 4.66 wt% water), 80.18 °C (87.27 wt% isopropanol, 12.73 wt% water), and 61.72 °C (89.18 wt% diisopropyl ether, 6.22 wt% isopropanol, 4.6 wt% water), respectively. If directly discharged without treatment, it will cause environmental pollution. In some separation systems, the concentration of a certain component accounts for the vast majority, and in principle, a preconcentration process needs to be added. Therefore, separating diisopropyl ether-isopropanol industrial wastewater will bring significant economic and ecological benefits. Since diisopropyl ether and isopropanol form various azeotropes in the wastewater, it is difficult to separate and purify the heterogeneous ternary azeotrope formed by diisopropyl ether / isopropanol / water using conventional distillation methods. Therefore, a special distillation method needs to be adopted, and the concentration of water in the ternary azeotrope accounts for the vast majority, and a preconcentration process needs to be added to save energy and reduce consumption.

[0004] The present invention utilizes the characteristic that the relative volatility of the azeotropic composition of the diisopropyl ether - isopropanol - water mixture changes in the direction of easier separation with the addition of a mixed extractant to separate the diisopropyl ether - isopropanol - water mixture with a high water content. Specifically, the present invention uses four distillation columns for separation and purification, designs a corresponding process scheme, and realizes the efficient separation of the mixture. The present invention is applicable to the mixture of diisopropyl ether, isopropanol, and water with a high water content, and is flexible in operation, and can effectively separate the ternary azeotropic mixture through extractive distillation.

Summary of the Invention

[0005] [Technical Problem to be Solved]

[0006] The object of the present invention is to provide a method for separating diisopropyl ether, isopropanol, and water by an extractive distillation process of a mixed extractant combined with a preconcentration function, and to realize the process design for efficient separation of a ternary azeotropic mixture by extractive distillation.

[0007] [Technical Solution]

[0008] The present invention proposes a method for separating diisopropyl ether, isopropanol, and water by an extractive distillation process of a mixed extractant combined with a preconcentration function. Utilizing the characteristic that the relative volatility of the azeotropic composition of the diisopropyl ether - isopropanol - water mixture changes in the direction of easier separation with the addition of a mixed extractant, extractive distillation is carried out by a four - column distillation method. The proposed process flow can realize the efficient separation of the ternary mixture of diisopropyl ether, isopropanol, and water with a high water content.

[0009] The method for separating diisopropyl ether, isopropanol, and water by an extractive distillation process of a mixed extractant combined with a preconcentration function proposed by the present invention is characterized in that the device for separating the diisopropyl ether - isopropanol - water azeotropic system with a high water content mainly comprises the following parts:

[0010] Pre-concentration tower (PDC), rectification tower (EDC1), rectification tower (EDC2), solvent recovery tower (SRC), condenser (B1), mixer (MIX), pump (P1), pump (P2), pump (P3), pump (P4), top storage tank (TANK1), top storage tank (TANK2), top storage tank (TANK3), reboiler (ROB1), reboiler (ROB2), reboiler (ROB3), reboiler (ROB4), condenser (COND1), condenser (COND2), condenser (COND3), condenser (COND4); The supplementary fresh mixed extractant and the recycled mixed extractant are mixed in the mixer (MIX) and then connected to the rectification tower (EDC1) through a pipeline; The pre-concentration tower (PDC) is connected to the rectification tower (EDC1) through a pipeline via pump (P1); The rectification tower (EDC1) is connected to the rectification tower (EDC2) through a pipeline via pump (P2); The rectification tower (EDC2) is connected to the solvent recovery tower (SRC) through a pipeline via pump (P3); The solvent recovery tower (SRC) is connected to the mixer (MIX) through a pipeline via pump (P4) first and then through the condenser (B1); The condenser (COND1) is connected to the pre-concentration tower (PDC), the condenser (COND2) is connected to the rectification tower (EDC1) and the top storage tank (TANK1), the condenser (COND3) is connected to the rectification tower (EDC2) and the top storage tank (TANK2), and the condenser (COND4) is connected to the solvent recovery tower (SRC) and the top storage tank (TANK3); The reboilers (ROB1), (ROB2), (ROB3) and (ROB4) are respectively connected to the pre-concentration tower (PDC), rectification tower (EDC1), rectification tower (EDC2) and solvent recovery tower (SRC);

[0011] The method for separating diisopropyl ether, isopropyl alcohol and water by an extractive distillation process of a mixed extractant with a pre-concentration function according to the invention mainly comprises the following steps:

[0012] (1) Add the raw material mixture of diisopropyl ether, isopropyl alcohol and water into the pre-concentration tower (PDC), and separate most of the water in the pre-concentration tower (PDC). A part of the bottom stream of the pre-concentration tower (PDC) is returned to the pre-concentration tower (PDC) after heat exchange through the reboiler (ROB1), and a part is passed into the top storage tank (TANK3) as a product. A part of the unpurified diisopropyl ether-isopropyl alcohol-water mixture is refluxed, and the other part is withdrawn from the pre-concentration tower (PDC) and passed into the rectification tower (EDC1) as a feedstock via pump (P1) first.

[0013] (2) The mixture drawn from the top of the pre-concentration tower (PDC) and the mixed extractant are respectively fed into the rectification tower (EDC1) from the lower part and the upper part of the tower. In the rectification tower (EDC1), the separation of diisopropyl ether is achieved. A part of the bottom stream of the rectification tower (EDC1) is returned to the rectification tower (EDC1) after heat exchange in the reboiler (ROB2), and a part is used as feed, which is first pumped by the pump (P2) and then fed into the rectification tower (EDC2); the diisopropyl ether is condensed by the condenser (COND2) and then enters the top storage tank (TANK1), part of which is refluxed and the other part is drawn from the top of the rectification tower (EDC1).

[0014] (3) The mixture drawn from the bottom of the rectification tower (EDC1) and the mixed extractant are respectively fed into the rectification tower (EDC2) from the lower part and the upper part of the tower. In the rectification tower (EDC2), the separation of isopropanol is achieved. A part of the bottom stream of the rectification tower (EDC2) is returned to the rectification tower (EDC2) after heat exchange in the reboiler (ROB3), and a part is used as feed, which is first pumped by the pump (P3) and then fed into the solvent recovery tower (SRC); the isopropanol is condensed by the condenser (COND3) and then enters the top storage tank (TANK2), part of which is refluxed and the other part is drawn from the top of the rectification tower (EDC2).

[0015] (4) The mixture drawn from the bottom of the rectification tower (EDC2) is fed into the solvent recovery tower (SRC). In the solvent recovery tower (SRC), the separation of the remaining water is achieved. A part of the bottom stream of the solvent recovery tower (SRC) is returned to the solvent recovery tower (SRC) after heat exchange in the reboiler (ROB3), and a part is first pumped by the pump (P4) and then refluxed through the condenser (B1) and fed into the mixer (MIX); the water is condensed by the condenser (COND4) and then enters the top storage tank (TANK3), part of which is refluxed and the other part is drawn from the top of the solvent recovery tower (SRC).

[0016] According to another preferred embodiment of the present invention, it is characterized in that: the operating pressure of the pre-concentration tower (PDC) is 0.2 - 1 atm, and the number of theoretical plates is 7 - 30; the operating pressure of the rectification tower (EDC1) is 0.2 - 1 atm, and the number of theoretical plates is 25 - 35; the operating pressure of the rectification tower (EDC2) is 0.2 - 1 atm, and the number of theoretical plates is 30 - 65; the operating pressure of the solvent recovery tower (SRC) is 0.2 - 1 atm, and the number of theoretical plates is 10 - 35. The feed temperature of the mixed extractant is 50 °C.

[0017] According to another preferred embodiment of the present invention, it is characterized in that: the mass ratio of the feed flow rates of the mixed extractant to the mixture of diisopropyl ether, isopropanol and water is 0.2 - 0.5.

[0018] According to another preferred embodiment of the present invention, it is characterized in that: in the mixed liquid of diisopropyl ether, isopropanol and water, the mass fraction of water is 55% - 65%, the mass fraction of diisopropyl ether is 25% - 35%, and the mass fraction of isopropanol is 5% - 15%. The mixed extractant is composed of dimethyl sulfoxide and N-formylmorpholine, the mass fraction of dimethyl sulfoxide is 60% - 70%, and the mass fraction of N-formylmorpholine is 30% - 40%.

[0019] According to another preferred embodiment of the present invention, it is characterized in that: by adopting this process flow, the clean and efficient separation of the mixture can be realized. The purity of the separated diisopropyl ether is greater than 99.90% (mass fraction), the purity of isopropanol is greater than 99.90% (mass fraction), the purity of water is greater than 99.90% (mass fraction), and the purity of the mixed extractant recovered at the bottom of the rectifying column SRC is greater than 99.90% (mass fraction).

[0020] [Beneficial effects]

[0021] The present invention has the following beneficial effects:

[0022] (1) The beneficial effect of the present invention is that the pre-concentration process is adopted to reduce the energy consumption of the extractive distillation process for separating the mixture of diisopropyl ether, isopropanol and water with a high water content.

[0023] (2) The use of the mixed extractant realizes the efficient separation of the mixture of diisopropyl ether, isopropanol and water.

[0024] (2) The designed process flow can realize the economic and clean separation of the mixture.

[0025] (3) The present invention is clean, efficient, economical, environmentally friendly, simple in process and flexible in operation.

Description of the drawings

[0026] Appendix Figure 1 It is a schematic diagram of the method for separating diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant.

[0027] In the figure, PDC - concentration column; EDC1 - rectifying column; EDC2 - rectifying column; SRC - rectifying column; COND1 - condenser; COND2 - condenser; COND3 - condenser; COND4 - condenser; B1 - condenser; ROB1 - reboiler; ROB2 - reboiler; ROB3 - reboiler; ROB4 - reboiler; P1 - pump; P2 - pump; P3 - pump; P4 - pump; TANK1 - top storage tank; TANK2 - top storage tank; TANK3 - top storage tank; MIX - mixer; the numbers represent each material flow.

Specific implementation manners

[0028] The following is further described in conjunction with the drawings, which does not limit the scope involved in the present invention.

[0029] Example 1:

[0030] The feed flow rate is 10,000 kg / h, the feed temperature is 25 °C, the pressure is 2 atm (absolute pressure), and the mass fractions of water, diisopropyl ether, and isopropanol in the feed stream are 58%, 31%, and 11% respectively. The operating pressure of the concentration tower (PDC) is 1 atm (absolute pressure), the number of trays is 11, the feed positions are the 3rd tray, the top temperature is 61.82 °C, and the bottom temperature is 99.84 °C; the operating pressure of the rectification tower (EDC1) is 1 atm (absolute pressure), the number of trays is 37, the extraction agent feed flow rate is 1,739.54 kg / h, the feed temperature is 50 °C, the pressure is 2 atm (absolute pressure), the feed positions are the 8th and 23rd trays, the top temperature is 68.46 °C, and the bottom temperature is 93.16 °C; the operating pressure of the rectification tower (EDC2) is 1 atm (absolute pressure), the number of trays is 73, the extraction agent feed flow rate is 1,528.04 kg / h, the feed temperature is 50 °C, the pressure is 2 atm (absolute pressure), the feed positions are the 7th and 66th trays, the top temperature is 82.02 °C, and the bottom temperature is 147.07 °C; the operating pressure of the solvent recovery tower (SRC) is 1 atm (absolute pressure), the number of trays is 14, the feed position is the 6th tray, the top temperature is 99.66 °C, and the bottom temperature is 197.95 °C; the mass fractions of the mixed extraction agents dimethyl sulfoxide and N-formylmorpholine are 69.16% and 30.39% respectively. After separation, the concentration of the diisopropyl ether product is greater than 99.98%, the concentration of the isopropanol product is greater than 99.93%, and the concentration of the water product is greater than 99.99%.

[0031] Example 2:

[0032] The feed flow rate is 10,000 kg / h, the feed temperature is 25 °C, the pressure is 2 atm (absolute pressure), and the mass fractions of water, diisopropyl ether, and isopropanol in the feed stream are 60%, 30%, and 10% respectively. The operating pressure of the concentration tower (PDC) is 0.8850 atm (absolute pressure), the number of trays is 9, the feed positions are the 3rd tray, the top temperature is 59.09 °C, and the bottom temperature is 96.81 °C; the operating pressure of the rectification tower (EDC1) is 0.6450 atm (absolute pressure), the number of trays is 29, the extraction agent feed flow rate is 1,853.20 kg / h, the feed temperature is 50 °C, the pressure is 2 atm (absolute pressure), the feed positions are the 9th and 29th trays, the top temperature is 55.45 °C, and the bottom temperature is 82.10 °C; the operating pressure of the rectification tower (EDC2) is 0.4328 atm (absolute pressure), the number of trays is 34, the extraction agent feed flow rate is 1,237.55 kg / h, the feed temperature is 50 °C, the pressure is 2 atm (absolute pressure), the feed positions are the 7th and 34th trays, the top temperature is 62.51 °C, and the bottom temperature is 119.96 °C; the operating pressure of the solvent recovery tower (SRC) is 0.2773 atm (absolute pressure), the number of trays is 13, the feed position is the 7th tray, the top temperature is 96.29 °C, and the bottom temperature is 195.07 °C; the mass fractions of the mixed extraction agents dimethyl sulfoxide and N-formylmorpholine are 63.04% and 36.96% respectively. After separation, the concentration of the diisopropyl ether product is greater than 99.99%, the concentration of the isopropanol product is greater than 99.93%, and the concentration of the water product is greater than 99.98%.

Claims

1. A method for separating diisopropyl ether, isopropanol and water by a mixed extractant extractive distillation process combined with a pre-concentration function, characterized in that The device for implementing the method mainly comprises the following parts: a pre-concentrator (PDC), a distillation tower (EDC1), a distillation tower (EDC2), a solvent recovery tower (SRC), a condenser (B1), a mixer (MIX), a pump (P1), a pump (P2), a pump (P3), a pump (P4), a tower top storage tank (TANK1), a tower top storage tank (TANK2), a tower top storage tank (TANK3), a reboiler (ROB1), a reboiler (ROB2), a reboiler (ROB3), a reboiler (ROB4), a condenser (COND1), a condenser (COND2), a condenser (COND3), and a condenser (COND4); the supplemented fresh mixed extractant and the circulating mixed extractant are mixed in the mixer (MIX) and then connected to the distillation tower (EDC1) through a pipeline; the pre-concentrator (PDC) is connected to the distillation tower (EDC1) through a pipeline via a pump (P1); the distillation tower (EDC1) is connected to the distillation tower (EDC1) through a pipeline. The pipeline is connected to the distillation tower (EDC2) through a pump (P2); the distillation tower (EDC2) is connected to the solvent recovery tower (SRC) through a pipeline through a pump (P3); the solvent recovery tower (SRC) is connected to the mixer (MIX) through a pipeline first through a pump (P4) and then through a condenser (B1); the condenser (COND1) is connected to the pre-concentrator (PDC), and the condenser (COND2) is connected to the distillation tower (EDC1) and the tower top storage tank (TANK1). The condenser (COND3) is connected to the distillation tower (EDC2) and the tower top storage tank (TANK2), and the condenser (COND4) is connected to the solvent recovery tower (SRC) and the tower top storage tank (TANK3); the reboiler (ROB1), the reboiler (ROB2), the reboiler (ROB3) and the reboiler (ROB4) are respectively connected to the pre-concentrator (PDC), the distillation tower (EDC1), the distillation tower (EDC2) and the solvent recovery tower (SRC); The invented method for separating diisopropyl ether, isopropanol and water by a mixed extractant extraction distillation process combined with a pre-concentration function mainly comprises the following steps: (1) A raw material mixture of diisopropyl ether, isopropyl alcohol and water is added to a pre-concentrator (PDC), and most of the water is separated in the pre-concentrator (PDC). A portion of the bottom stream of the pre-concentrator (PDC) is returned to the pre-concentrator (PDC) after heat exchange in a reboiler (ROB1), and a portion is passed to a tower top storage tank (TANK3) as a product. A portion of the unpurified diisopropyl ether-isopropyl alcohol-water mixture is refluxed, and the other portion is extracted from the pre-concentrator (PDC) and passed to a distillation tower (EDC1) as a feed through a pump (P1). (2) The mixture and mixed extractant taken out from the top of the pre-concentrator (PDC) are added to the distillation tower (EDC1) from the lower part and the upper part respectively. In the distillation tower (EDC1), the separation of diisopropyl ether is achieved. A part of the bottom stream of the distillation tower (EDC1) is returned to the distillation tower (EDC1) after heat exchange in the reboiler (ROB2), and a part is first passed through the pump (P2) and then into the distillation tower (EDC2) as a feed; the diisopropyl ether is condensed in the condenser (COND2) and then enters the tower top storage tank (TANK1), a part of which is refluxed and the other part is taken out from the top of the distillation tower (EDC1). (3) The mixture and the mixed extractant taken out from the bottom of the distillation tower (EDC1) are added to the distillation tower (EDC2) from the lower part and the upper part respectively. In the distillation tower (EDC2), the separation of isopropyl alcohol is achieved. A part of the bottom stream of the distillation tower (EDC2) is returned to the distillation tower (EDC2) after heat exchange in the reboiler (ROB3), and a part of it is used as feed and then passed through the pump (P3) to the solvent recovery tower (SRC); the isopropyl alcohol is condensed in the condenser (COND3) and then enters the tower top storage tank (TANK2), a part of which is refluxed and the other part is taken out from the top of the distillation tower (EDC2). (4) The mixture extracted from the bottom of the distillation tower (EDC2) is added to the solvent recovery tower (SRC), and the residual water is separated in the solvent recovery tower (SRC). A part of the bottom stream of the solvent recovery tower (SRC) is returned to the solvent recovery tower (SRC) after heat exchange in the reboiler (ROB4), and a part is first refluxed through the pump (P4) and passed through the condenser (B1) into the mixer (MIX); the water is condensed in the condenser (COND4) and enters the tower top storage tank (TANK3), a part of which is refluxed and the other part is extracted from the top of the solvent recovery tower (SRC).

2. The method for separating diisopropyl ether, isopropanol and water by a mixed extractant extractive distillation process combined with a pre-concentration function according to claim 1, characterized in that: The operating pressure of the pre-concentrator (PDC) is 0.2-1 atm, and the number of theoretical plates is 7-30; the operating pressure of the distillation tower (EDC1) is 0.2-1 atm, and the number of theoretical plates is 25-35; the operating pressure of the distillation tower (EDC2) is 0.2-1 atm, and the number of theoretical plates is 30-65; the operating pressure of the solvent recovery tower (SRC) is 0.2-1 atm, and the number of theoretical plates is 10-35. The feed temperature of the mixed extractant is 50°C.

3. The method for separating diisopropyl ether, isopropanol and water by a mixed extractant extractive distillation process combined with a pre-concentration function according to claim 1, characterized in that: The feed flow mass ratio of the mixed extractant to the mixture of diisopropyl ether, isopropanol and water is 0.2-0.

5.

4. The method for separating diisopropyl ether, isopropanol and water by a mixed extractant extractive distillation process combined with a pre-concentration function according to claim 1, characterized in that: In the mixed solution of diisopropyl ether, isopropyl alcohol and water, the mass fraction of water is 55% to 65%, the mass fraction of diisopropyl ether is 25% to 35%, and the mass fraction of isopropyl alcohol is 5% to 15%. The mixed extractant is composed of dimethyl sulfoxide and N-formylmorpholine, the mass fraction of dimethyl sulfoxide is 60% to 70%, and the mass fraction of N-formylmorpholine is 30% to 40%.

5. The method for separating diisopropyl ether, isopropanol and water by a mixed extractant extractive distillation process combined with a pre-concentration function according to claim 1, characterized in that: The process can realize clean and efficient separation of mixed substances. The purity of the separated diisopropyl ether is greater than 99.90% (mass fraction), the purity of isopropyl alcohol is greater than 99.90% (mass fraction), the purity of water is greater than 99.90% (mass fraction), and the purity of the mixed extractant recovered from the bottom of the distillation tower SRC is greater than 99.90% (mass fraction).

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