Method for extracting, rectifying and separating vinyl acetate, methyl acetate and water by using mixed extracting agent

Abstract

The invention relates to a method for extracting, rectifying and separating vinyl acetate, methyl acetate and water by using a mixed extracting agent, which utilizes the characteristic that a vinyl acetate-methyl acetate-water azeotropic system changes the intermolecular relative volatility along with the addition of the mixed extracting agent, and through the three-tower operation of a rectifying tower (T1), a rectifying tower (T2) and a rectifying tower (T3), the content of the methyl acetate in the water is reduced. The method realizes efficient separation of the ternary mixture, the molar fraction of the separated vinyl acetate is greater than 99.99%, the molar fraction of the separated methyl acetate is greater than 99.99%, and the molar fraction of the separated water is greater than 99.99%. The method solves the problem that the azeotropic system is difficult to separate by using common rectification, is flexible to operate, is economical and environment-friendly, and can realize effective separation of the ternary azeotropic mixture through three towers.

Description

Technical Field

[0001] This invention belongs to the field of chemical separation and purification, specifically relating to a method for separating vinyl acetate-methyl acetate-water azeotrope using extractive distillation. Background Technology

[0002] Vinyl acetate and methyl acetate are widely used in many fields, including medical and health, food industry, and chemical industry. Vinyl acetate, as a widely used organic chemical, is a major monomer for the synthesis of key polymers such as polyvinyl alcohol, polyvinyl acetate, and ethylene-vinyl acetate copolymers. These polymers are widely used in coatings, adhesives, films, laminated glass, leather, and textile fibers. Furthermore, vinyl acetate derivatives support technological advancements in chemical manufacturing, food processing, pharmaceuticals, printing, textiles, and construction industries. Vinyl acetate is a flammable liquid and readily polymerizable, primarily used in the production of polymer materials such as adhesives, coatings, vinylon fibers, and EVA resins. Methyl acetate is recognized as an environmentally friendly chemical raw material with high solubility and rapid drying properties. Therefore, it is widely used in coatings, fragrances, inks, polymer solvents, adhesives, fine chemicals, and pharmaceutical compounds.

[0003] In the production of polyvinyl alcohol, a ternary azeotropic system is formed, consisting of methyl acetate, vinyl acetate, and water. This azeotropic system contains three azeotropes at 1 atmosphere: methyl acetate-water, vinyl acetate-water, and vinyl acetate-methyl acetate-water, with boiling points of 56.98°C, 63.51°C, and 63.68°C, respectively. Separating and recovering vinyl acetate, methyl acetate, and water can reduce production costs and further decrease emissions. Because of the presence of azeotropes in the mixture, simple distillation methods cannot achieve effective separation; therefore, a special distillation method is required.

[0004] This invention utilizes the characteristic that the relative volatility of azeotropic mixtures of methyl acetate-water, vinyl acetate-water, and vinyl acetate-methyl acetate-water changes towards easier separation with the addition of a mixed extractant. Specifically, this invention employs three distillation columns for separation and purification, and designs corresponding process schemes to achieve efficient separation of the mixture. This invention is applicable to mixtures of vinyl acetate, methyl acetate, and water, offers flexible operation, and enables effective separation of ternary azeotropic mixtures through extractive distillation. Summary of the Invention

[0005] [Technical problem to be solved] The purpose of this invention is to provide a method for separating a mixture of vinyl acetate, methyl acetate and water by extractive distillation using a mixed extractant, thereby achieving a process design for the efficient separation of ternary azeotropic mixtures by extractive distillation.

[0006] [Technical Solution]

[0007] This invention proposes a method for extractive distillation to separate vinyl acetate, methyl acetate, and water using a mixed extractant. It utilizes the characteristic that the relative volatility of methyl acetate-water, vinyl acetate-water, and vinyl acetate-methyl acetate-water azeotropic mixtures changes towards easier separation with the addition of a mixed extractant. The method employs a three-tower distillation process, enabling efficient separation of the ternary mixture of vinyl acetate, methyl acetate, and water.

[0008] The present invention proposes a method for separating vinyl acetate, methyl acetate, and water using a mixed extractant through extractive distillation, characterized in that the apparatus for separating the azeotropic system of vinyl acetate, methyl acetate, and water mainly comprises the following parts: Distillation column (T1), distillation column (T2), distillation column (T3), condenser (COL), pump (P1), pump (P2), pump (P3), top storage tank (C1), top storage tank (C2), top storage tank (C3), reboiler (H1), reboiler (H2), reboiler (H3), condenser (CL1), condenser (CL2), condenser (CL3); the circulating mixed extractant is connected to distillation column (T1) via pipeline; distillation column (T1) is connected to distillation column (T2) via pipeline and pump (P1); distillation column (T1) passes through... The pipeline is connected to the distillation column (T3); the distillation column (T3) is connected to the distillation column (T1) via the pipeline, first through the pump (P3) and then through the condenser (COL); the condenser (CL1) is connected to the distillation column (T1) and the top storage tank (C1); the condenser (CL2) is connected to the distillation column (T2) and the top storage tank (C2); the condenser (CL3) is connected to the distillation column (T3) and the top storage tank (C3); the reboilers (H1), (H2), and (H3) are connected to the distillation columns (T1), (T2), and (T3) respectively. The invented method for separating vinyl acetate, methyl acetate and water by extraction distillation using a mixed extractant mainly includes the following steps: (1) A mixture of vinyl acetate, methyl acetate and water feedstock and a mixed extractant are added to the distillation column (T1) from the bottom part and the top part of the column, respectively. In the distillation column (T1), the vinyl acetate, methyl acetate and water and the mixed extractant are separated. Part of the bottom stream of the distillation column (T1) is returned to the distillation column (T1) after heat exchange in the reboiler (H1), and part of it is fed into the distillation column (T3). After the vinyl acetate and methyl acetate are condensed by the condenser (CL1), they enter the top storage tank (C1). Part of it is refluxed, and the other part is fed into the distillation column (T2) from the top of the distillation column (T1) through the pump (P1).

[0009] (2) In the distillation column (T2), vinyl acetate is separated. Part of the bottom stream of the distillation column (T2) is returned to the distillation column (T2) after heat exchange in the reboiler (H2); methyl acetate is condensed by the condenser (CL2) and enters the top storage tank (C2), part of which is refluxed and the other part is taken out from the top of the distillation column (T2).

[0010] (3) In the distillation column (T3), water separation is achieved. Part of the bottom stream of the distillation column (T3) is returned to the distillation column (T3) after heat exchange in the reboiler (H3), and part of the reflux is first pumped (P2) and then condensed (COL) into the distillation column (T1). Toluene is condensed by the condenser (CL3) and enters the top storage tank (C3). Part of it is refluxed and the other part is taken out from the top of the distillation column (T3).

[0011] According to another preferred embodiment of the present invention, the distillation column (T1) operates at a pressure of 1 atm and has 23-42 theoretical plates; the distillation column (T2) operates at a pressure of 1 atm and has 62-71 theoretical plates; the distillation column (T3) operates at a pressure of 1 atm and has 12-15 theoretical plates. The feed temperature of the mixed extractant is 40°C.

[0012] According to another preferred embodiment of the present invention, the feed flow rate of the mixed extractant to the mixture of vinyl acetate, methyl acetate and water is 0.4% to 0.5% by mass.

[0013] According to another preferred embodiment of the present invention, the mixture of vinyl acetate, methyl acetate and water has a molar fraction of 30% to 35%, a molar fraction of methyl acetate of 10% to 15%, and a molar fraction of water of 50% to 60%.

[0014] According to another preferred embodiment of the present invention, the process can achieve clean and efficient separation of the mixed substances, and the purity of methyl acetate after separation is greater than 99.90% (mole fraction), the purity of vinyl acetate is greater than 99.90% (mole fraction), the purity of water is greater than 99.90% (mole fraction), and the purity of the mixed extractant recovered from the bottom of the distillation column T3 is greater than 99.90% (mole fraction).

[0015] [Beneficial Effects]

[0016] This invention has the following advantages: (1) The beneficial effect of the present invention is that the ternary azeotropic mixture of vinyl acetate, methyl acetate and water is efficiently separated by the mixed extractant distillation method.

[0017] (2) The designed process can achieve economical and clean separation of the mixture.

[0018] (3) This invention is clean, efficient, economical and environmentally friendly, with simple process and flexible operation. Attached Figure Description

[0019] Appendix Figure 1 This is a schematic diagram of a method for separating vinyl acetate, methyl acetate and water using a mixed extractant through extraction and distillation.

[0020] In the diagram, T1 is the distillation column; T2 is the distillation column; T3 is the distillation column; CL1 is the condenser; CL2 is the condenser; CL3 is the condenser; COL is the condenser; H1 is the reboiler; H2 is the reboiler; H3 is the reboiler; P1 is the pump; P2 is the pump; P3 is the pump; C1 is the top storage tank; C2 is the top storage tank; C3 is the top storage tank; and the numbers represent the various material flows. Detailed Implementation

[0021] The following description, in conjunction with the accompanying drawings, is intended to further illustrate the scope of the invention but is not intended to limit its scope.

[0022] Example 1:

[0023] The feed flow rate is 100 kmol / h, the feed temperature is 40℃, and the pressure is 1.5 atm (absolute pressure). The molar fraction of vinyl acetate in the feed stream is 34%, the molar fraction of methyl acetate is 10%, and the molar fraction of water is 56%. The extractant feed flow rate is 50 kmol / h, the feed temperature is 40℃, and the pressure is 1 atm (absolute pressure). Distillation column (T1) operates at 1 atm (absolute pressure), has 23 trays, and feeds to the 8th and 20th trays respectively. The top temperature is 68.26℃, and the bottom temperature is 125.26℃. Distillation column (T2) operates at 1 atm (absolute pressure), has 62 trays, and feeds to the 25th tray. The top temperature is 57.06℃, and the bottom temperature is 72.70℃. Distillation column (T3) operates at 1 atm (absolute pressure), has 12 trays, and feeds to the 12th tray. The top temperature is 99.78℃, and the bottom temperature is 202.68℃. After separation, the product concentrations of vinyl acetate, methyl acetate, and water are all greater than 99.90%.

[0024] Example 2:

[0025] The feed flow rate is 150 kmol / h, the feed temperature is 40℃, and the pressure is 1.5 atm (absolute pressure). The molar fraction of vinyl acetate in the feed stream is 34%, the molar fraction of methyl acetate is 10%, and the molar fraction of water is 56%. The extractant feed flow rate is 50 kmol / h, the feed temperature is 40℃, and the pressure is 1 atm (absolute pressure). Distillation column (T1) operates at 1 atm (absolute pressure), has 42 trays, and feeds to the 6th and 20th trays respectively. The top temperature is 68.25℃, and the bottom temperature is 122.46℃. Distillation column (T2) operates at 1 atm (absolute pressure), has 70 trays, and feeds to the 39th tray. The top temperature is 57.06℃, and the bottom temperature is 72.70℃. Distillation column (T3) operates at 1 atm (absolute pressure), has 15 trays, and feeds to the 7th tray. The top temperature is 99.72℃, and the bottom temperature is 202.99℃. After separation, the product concentrations of vinyl acetate, methyl acetate, and water are all greater than 99.90%.

[0026] Example 3:

[0027] The feed flow rate is 200 kmol / h, the feed temperature is 40℃, and the pressure is 1.5 atm (absolute pressure). The molar fraction of vinyl acetate in the feed stream is 34%, the molar fraction of methyl acetate is 10%, and the molar fraction of water is 56%. The extractant feed flow rate is 50 kmol / h, the feed temperature is 40℃, and the pressure is 1 atm (absolute pressure). Distillation column (T1) operates at 1 atm (absolute pressure), has 39 trays, and feeds to the 4th and 31st trays respectively. The top temperature is 68.26℃, and the bottom temperature is 118.38℃. Distillation column (T2) operates at 1 atm (absolute pressure), has 71 trays, and feeds to the 24th tray. The top temperature is 57.06℃, and the bottom temperature is 72.70℃. Distillation column (T3) operates at 1 atm (absolute pressure), has 13 trays, and feeds to the 7th tray. The top temperature is 99.33℃, and the bottom temperature is 202.89℃. After separation, the product concentrations of vinyl acetate, methyl acetate, and water are all greater than 99.90%.

Claims

1. A method for separating vinyl acetate, methyl acetate and water by extraction distillation using a mixed extractant, characterized in that... The apparatus for implementing this method mainly includes the following parts: Distillation column (T1), distillation column (T2), distillation column (T3), condenser (COL), pump (P1), pump (P2), pump (P3), top storage tank (C1), top storage tank (C2), top storage tank (C3), reboiler (H1), reboiler (H2), reboiler (H3), condenser (CL1), condenser (CL2), condenser (CL3); the circulating mixed extractant is connected to distillation column (T1) via pipeline; distillation column (T1) is connected to distillation column (T2) via pipeline and pump (P1); distillation column (T1) passes through... The pipeline is connected to the distillation column (T3); the distillation column (T3) is connected to the distillation column (T1) via the pipeline, first through the pump (P3) and then through the condenser (COL); the condenser (CL1) is connected to the distillation column (T1) and the top storage tank (C1); the condenser (CL2) is connected to the distillation column (T2) and the top storage tank (C2); the condenser (CL3) is connected to the distillation column (T3) and the top storage tank (C3); the reboilers (H1), (H2), and (H3) are connected to the distillation columns (T1), (T2), and (T3) respectively. A method for separating vinyl acetate, methyl acetate and water using the above-described apparatus with a mixed extractant includes the following steps: (1) A mixture of vinyl acetate, methyl acetate and water and a mixed extractant are added to the distillation column (T1) from the bottom part and the top part of the column, respectively. In the distillation column (T1), vinyl acetate, methyl acetate and water and the mixed extractant are separated. Part of the bottom stream of the distillation column (T1) is returned to the distillation column (T1) after heat exchange in the reboiler H1, and part of it is fed into the distillation column (T3). After being condensed by the condenser (CL1), vinyl acetate and methyl acetate enter the top storage tank (C1). Part of it is refluxed and the other part is pumped from the top of the distillation column (T1) into the distillation column (T2) through the pump (P1). (2) Vinyl acetate is separated in the distillation column (T2). A portion of the bottom stream of the distillation column (T2) is returned to the distillation column (T2) after heat exchange in the reboiler (H2); methyl acetate is condensed in the condenser (CL2) and enters the top storage tank (C2), a portion of which is refluxed and the other portion is collected from the top of the distillation column (T2). (3) Water separation is achieved in the distillation column (T3). Part of the bottom stream of the distillation column (T3) is returned to the distillation column (T3) after heat exchange in the reboiler (H3), and part of the reflux is first pumped (P2) and then condensed (COL) into the distillation column (T1); After being condensed by the condenser (CL3), the water enters the top storage tank (C3), part of which is refluxed and the other part is taken out from the top of the distillation column (T3).

2. The method for separating vinyl acetate, methyl acetate and water by extraction distillation using a mixed extractant according to claim 1, characterized in that: The operating pressure of the distillation column (T1) is 1 atm, and the number of theoretical plates is 23-42; the operating pressure of the distillation column (T2) is 1 atm, and the number of theoretical plates is 62-71; the operating pressure of the distillation column (T3) is 1 atm, and the number of theoretical plates is 12-15; the feed temperature of the mixed extractant is 40℃.

3. The method for separating vinyl acetate, methyl acetate and water by extraction distillation using a mixed extractant according to claim 1, characterized in that: The mass ratio of the feed flow rate of the mixed extractant to the mixture of vinyl acetate, methyl acetate and water is 0.4 to 0.

5.

4. The method for separating vinyl acetate, methyl acetate and water by extraction distillation using a mixed extractant as described in claim 1, characterized in that: In the mixture of vinyl acetate, methyl acetate and water, the molar fraction of vinyl acetate is 30%–35%, the molar fraction of methyl acetate is 10%–15%, and the molar fraction of water is 50%–60%.

5. The method for separating vinyl acetate, methyl acetate and water by extraction distillation using a mixed extractant as described in claim 1, characterized in that: After separation, the purity of methyl acetate is greater than 99.90% (mole fraction), the purity of vinyl acetate is greater than 99.90% (mole fraction), the purity of water is greater than 99.90% (mole fraction), and the purity of the mixed extractant recovered from the bottom of distillation column T3 is greater than 99.90% (mole fraction).

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