Method for producing vinyl acetate

Abstract

This method for producing vinyl acetate comprises at least: a step (1) for obtaining a crude product containing vinyl acetate by reacting ethylene, acetic acid, and oxygen; a step (2) in which a gaseous composition containing ethylene and vinyl acetate is separated from the crude product; and a step (3) in which at least a portion of the gaseous composition is introduced into a gas cleaning tower having at least an outlet (A) and an outlet (B), the total content of acetic acid and water in the liquid composition (alpha) extracted from the outlet (A) being 70 mass% or more, and the total content of acetic acid and water in the liquid composition (alpha) extracted from the outlet (B) being 70 mass% or more. The total content of vinyl acetate and acetic acid in the liquid composition (beta) extracted from the extraction opening (B) is 90% by mass or more, and the content of water is 10% by mass or less. Thus, in the method for producing vinyl acetate, the energy required for separating vinyl acetate, water, and acetic acid by distillation is reduced.

Description

Technical Field

[0001] This invention relates to a method for manufacturing vinyl acetate. In particular, it relates to a method for manufacturing vinyl acetate comprising at least the following steps: step (1), in which ethylene, acetic acid, and oxygen are reacted to obtain a crude product containing vinyl acetate; step (2), in which the crude product is separated into a liquid composition containing vinyl acetate, acetic acid, and water, and a gaseous composition containing ethylene and vinyl acetate; and step (3), in which at least a portion of the gaseous composition is introduced into a gas scrubbing tower and scrubbed with acetic acid and water, thereby removing vinyl acetate from the gaseous composition. Background Technology

[0002] Vinyl acetate is a useful compound used as a raw material for polyvinyl acetate, etc. The Wacker process, which uses ethylene, acetic acid, and oxygen as raw materials, is widely used in its industrial production.

[0003] Patent Document 1 illustrates an example of a specific manufacturing method based on the Wacker process and describes a method for manufacturing vinyl acetate characterized by reacting ethylene with acetic acid and oxygen in a single reactor, and a) Separate the product gas stream, which mainly contains ethylene, vinyl acetate, acetic acid, water, carbon dioxide, and other inert gases, and b) The recirculated gas stream containing ethylene and CO2 is returned to the aforementioned reactor. c) Before returning the aforementioned recirculated gas stream to the reactor, compress it using a recirculated gas compressor; and d) A portion of the aforementioned recirculating gas flow is branched off to the suction or compression side of the aforementioned recirculating gas compressor for CO2 scrubbing, and e) Vinyl acetate is produced by a continuous gas-phase process using a multiphase catalyst and washing in a water scrubber prior to the aforementioned CO2 washing, wherein in this method of producing vinyl acetate, f) After the aforementioned partial gas flow is washed with CO2, it is supplied to the aforementioned recirculating gas along with ethylene as the injection gas via a jet compressor on the compression side of the aforementioned recirculating gas compressor and downstream of the outlet of the partial gas flow used for CO2 washing, and / or g) The product from the bottom of the tower is directly supplied from the washing unit to the front dehydration tower.

[0004] By subjecting a portion of the aforementioned circulating gas stream to CO2 scrubbing, CO2 byproducts from the vinyl acetate synthesis reaction are prevented from accumulating in the circulating gas. Furthermore, by pre-passing the gas supplied before this CO2 scrubbing into a water scrubber and washing it with water and acetic acid, vinyl acetate is removed from the gas. During this gas scrubbing, a bottom product containing water, acetic acid, and vinyl acetate is generated at the bottom of the water scrubber. This bottom product is then distilled together with the crude reaction product containing vinyl acetate to obtain vinyl acetate after the separation of water and acetic acid.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Publication No. 2012-524757. Summary of the Invention

[0006] The problem the invention aims to solve In the production of vinyl acetate using the method described in Patent Document 1, thermal energy such as steam is required to separate acetic acid, water, and vinyl acetate by distillation. In particular, a large amount of energy is required to evaporate a large amount of water, therefore, strategies to reduce this energy are sought.

[0007] The present invention was made to solve this problem, and its purpose is to reduce the energy required to separate vinyl acetate, water and acetic acid by distillation in the method for manufacturing vinyl acetate.

[0008] Methods for solving problems The above-mentioned problem is solved by the following invention.

[0009] [1] A method for manufacturing vinyl acetate, which includes at least the following steps: Step (1) involves reacting ethylene, acetic acid, and oxygen to obtain a crude product containing vinyl acetate. Step (2) separates the aforementioned crude product into a liquid composition containing vinyl acetate, acetic acid, and water, and a gaseous composition containing ethylene and vinyl acetate; and Step (3) involves introducing at least a portion of the aforementioned gaseous composition into a gas scrubbing tower, whereby the gaseous composition is scrubbed with acetic acid and water, thereby removing vinyl acetate from the gaseous composition. The aforementioned gas cleaning tower has at least an outlet (A) and an outlet (B). The liquid composition (α) taken from the aforementioned outlet (A) contains acetic acid and water, and the total content of acetic acid and water in the aforementioned liquid composition (α) is 70% by mass or more. The liquid composition (β) taken out from the aforementioned outlet (B) contains vinyl acetate and acetic acid, wherein the total content of vinyl acetate and acetic acid in the aforementioned liquid composition (β) is 90% by mass or more, and the water content is 10% by mass or less.

[0010] [2] According to the manufacturing method described in [1], the aforementioned outlet (A) is located above the aforementioned outlet (B).

[0011] [3] According to the manufacturing method described in [1] or [2], the aforementioned gas cleaning tower has an acetic acid inlet and a water inlet, and the aforementioned outlet (A) is located above the aforementioned acetic acid inlet and below the aforementioned water inlet.

[0012] [4] The manufacturing method according to any one of [1] to [3] further includes step (4): introducing the aforementioned liquid composition (α) into an extraction tower, extracting acetic acid with vinyl acetate, and separating it into a liquid composition containing vinyl acetate and acetic acid and a liquid composition containing water.

[0013] [5] According to the manufacturing method described in [4], the aforementioned liquid composition (α) is brought into convective contact with vinyl acetate in the aforementioned extraction tower, thereby separating into a liquid composition containing vinyl acetate and acetic acid and a liquid composition containing water.

[0014] [6] According to the manufacturing method described in [5], the liquid composition (α) is introduced from the upper part of the extraction tower, vinyl acetate is introduced from the lower part of the extraction tower, the liquid composition (α) and vinyl acetate are brought into convection contact, a liquid composition containing vinyl acetate and acetic acid is taken out from the upper part of the extraction tower, and a liquid composition containing water is taken out from the lower part of the extraction tower.

[0015] [7] The manufacturing method according to any one of [1] to [6] further includes step (5): introducing the liquid composition separated by the aforementioned step (2) into a distillation column for distillation.

[0016] [8] The manufacturing method according to [7] further includes the step of introducing the aforementioned liquid composition (β) into the aforementioned distillation column.

[0017] [9] The manufacturing method according to [7] or [8] further includes the step of introducing the liquid composition containing vinyl acetate and acetic acid separated by the aforementioned step (4) into the aforementioned distillation column.

[0018]

[10] The manufacturing method according to any one of [7] to [9], wherein vinyl acetate, acetic acid and water are separated in the aforementioned distillation column.

[0019]

[11] According to the manufacturing method described in

[10] , the vinyl acetate obtained by the aforementioned step (5) is optionally purified and then used in the aforementioned step (4).

[0020]

[12] The manufacturing method according to any one of [1] to

[11] , wherein in the aforementioned step (3), the aforementioned gaseous composition is washed with acetic acid and water, thereby separating a gaseous composition containing ethylene and carbon dioxide and a liquid composition containing vinyl acetate. The manufacturing method further includes step (6): introducing the aforementioned gaseous composition containing ethylene and carbon dioxide into a carbon dioxide removal system to separate it into ethylene and carbon dioxide. The ethylene separated by the aforementioned process (6) is used in the aforementioned process (1).

[0021] Invention Effects According to the manufacturing method of the present invention, the energy required to separate vinyl acetate, water and acetic acid by distillation can be reduced, and an industrial manufacturing method for vinyl acetate with low energy consumption can be provided. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the vinyl acetate manufacturing apparatus used in Example 1.

[0023] Figure 2 This is a schematic diagram of the vinyl acetate manufacturing apparatus used in Comparative Example 1. Detailed Implementation

[0024] This invention relates to a method for manufacturing vinyl acetate. The method for manufacturing vinyl acetate includes at least the following steps: Step (1) involves reacting ethylene, acetic acid, and oxygen to obtain a crude product containing vinyl acetate. Step (2) separates the aforementioned crude product into a liquid composition containing vinyl acetate, acetic acid, and water, and a gaseous composition containing ethylene and vinyl acetate; and Step (3) involves introducing at least a portion of the aforementioned gaseous composition into a gas scrubbing tower, whereby the gaseous composition is scrubbed with acetic acid and water, thereby removing vinyl acetate from the gaseous composition. The aforementioned gas cleaning tower has at least an outlet (A) and an outlet (B). The liquid composition (α) taken from the aforementioned outlet (A) contains acetic acid and water, and the total content of acetic acid and water in the aforementioned liquid composition (α) is 70% or more. The liquid composition (β) taken out from the aforementioned outlet (B) contains vinyl acetate and acetic acid, and the total content of vinyl acetate and acetic acid in the aforementioned liquid composition (β) is 90% by mass or more.

[0025] In the manufacturing method of the present invention, vinyl acetate is manufactured by the Wacker process. Thus, vinyl acetate is synthesized using ethylene, acetic acid, and oxygen as raw materials via the following formula (I).

[0026] C2H4 + CH3COOH + 1 / 2O2 → CH2CHOCOCH3 + H2O (I) Step (1) is a step in which ethylene, acetic acid, and oxygen react to obtain a crude product containing vinyl acetate. In a reactor, the vinyl acetate synthesis reaction shown in formula (I) above is carried out in a gas-phase process using a heterogeneous catalyst. Ethylene, acetic acid, and oxygen are contacted at a pressure of 0.1–3 MPa and a temperature of 130–200 °C with a fixed-bed catalyst containing palladium or palladium compounds and an alkali metal salt on a support material, while vinyl acetate and water are generated. The reaction is exothermic, and vinyl acetate is synthesized continuously. At this time, a side reaction shown in formula (II) below also occurs, where a portion of the ethylene is oxidized by oxygen to produce carbon dioxide. As a result, the crude product taken from the reactor contains vinyl acetate and water as reaction products, ethylene, acetic acid, and oxygen as unreacted substances, and carbon dioxide as a byproduct.

[0027] C2H4+3O2→ 2CO2+2H2O (II) Step (2) is a step of separating the crude product obtained by step (1) into a liquid composition containing vinyl acetate, acetic acid, and water, and a gaseous composition containing ethylene and vinyl acetate. The liquid composition may contain small amounts of other components. In addition, the gaseous composition typically contains carbon dioxide and oxygen in addition to ethylene and vinyl acetate, and may contain water and / or acetic acid in a gaseous state. The separation device used for separating the liquid composition and the gaseous composition is not particularly limited, but a vertical gas separation tower is preferred for continuous separation. In this case, it is preferable to supply acetic acid to the separation device, thereby dissolving vinyl acetate and water in acetic acid, and then exporting the liquid composition containing vinyl acetate, acetic acid, and water from the separation device. Specifically, it is preferable to supply acetic acid from the top of the vertical separation tower and export the liquid composition from the bottom. In addition, it is also preferable to include a step of introducing the liquid composition thus separated by step (2) into a distillation tower.

[0028] Step (3) involves introducing at least a portion of the aforementioned gaseous composition obtained through step (2) into a gas scrubbing tower to scrub the gaseous composition with acetic acid and water, thereby removing vinyl acetate from the gaseous composition. By removing vinyl acetate, a decrease in carbon dioxide removal capacity can be prevented in the carbon dioxide removal system of step (6) described later. The total amount of the aforementioned gaseous composition obtained through step (2) can be supplied to step (3) without causing an excessive increase in the concentration of carbon dioxide produced as a byproduct in step (1), and only a portion can be introduced into the gas scrubbing tower and supplied to the carbon dioxide removal system. Typically, 1 to 20% by mass of the aforementioned gaseous composition obtained through step (2) is introduced into the gas scrubbing tower.

[0029] The aforementioned gas cleaning tower has two outlets, outlet (A) and outlet (B), and may further have other outlets. A liquid composition after gas cleaning is taken out from both outlet (A) and outlet (B). Liquid composition (α) is taken out from outlet (A). Liquid composition (α) contains acetic acid and water, and the total content of acetic acid and water in liquid composition (α) is 70% by mass or more. The total content of acetic acid and water is preferably 80% by mass or more, more preferably 90% by mass or more. Liquid composition (α) mainly contains vinyl acetate in addition to acetic acid and water. On the other hand, liquid composition (β) is taken out from outlet (B). Liquid composition (β) contains vinyl acetate and acetic acid, and the total content of vinyl acetate and acetic acid in liquid composition (β) is 90% by mass or more, at which point the water content is 10% by mass or less. By keeping the water content at 10% by mass or less, the energy required to supply the liquid composition (β) for distillation can be reduced. The water content is preferably 5% by mass, more preferably 2% by mass or less. On the other hand, the total content of vinyl acetate and acetic acid is preferably 95% by mass or more, and more preferably 98% by mass or more.

[0030] In the gas cleaning tower used in step (3), the aforementioned outlet (A) is preferably located above the aforementioned outlet (B). This reduces the water content of the liquid composition (β) taken from the outlet (B). Furthermore, the gas cleaning tower has an acetic acid inlet and a water inlet, and the aforementioned outlet (A) is preferably located above the aforementioned acetic acid inlet and below the aforementioned water inlet. By operating in this way, vinyl acetate in the gas can be dissolved in acetic acid and removed, and acetic acid contained in the gas after the vinyl acetate is removed can be dissolved in water and removed. As a result, a liquid composition (α) with acetic acid and water as the main components is discharged from the outlet (A), which is located above the acetic acid inlet and below the aforementioned water inlet. In addition, a liquid composition (β) with vinyl acetate and acetic acid as the main components is discharged from the outlet (B), which is located below the outlet (A). Considering the dissolution efficiency of vinyl acetate, it is preferable to introduce the gaseous composition obtained in step (2) into the gas cleaning tower below the acetic acid inlet. Furthermore, the outlet (B) is preferably located below the section where the gaseous composition obtained in step (2) is introduced into the gas cleaning tower, and is particularly preferably located at the bottom of the tower. On the other hand, the location where the gas cleaned by the gas cleaning tower is taken out is preferably above the water inlet, and is particularly preferably at the top of the tower. That is, in the gas cleaning tower, the outlet for cleaned gas, the water inlet, the outlet (A), the acetic acid inlet, the gas inlet before cleaning, and the outlet (B) are preferably arranged sequentially from top to bottom. Preferably, the process of introducing the liquid composition (β) taken out from the outlet (B) in step (3) into the distillation tower is also included.

[0031] Preferably, the process further includes step (4): the aforementioned liquid composition (α) discharged from the outlet (A) of the gas cleaning tower in step (3) is introduced into an extraction tower, and acetic acid is extracted using vinyl acetate, separating the liquid composition containing vinyl acetate and acetic acid into a liquid composition containing water. The extraction tower used in step (4) is not particularly limited as long as it is capable of liquid-liquid extraction. The liquid composition (α) and liquid vinyl acetate are introduced into the extraction tower, and they come into contact in the liquid phase. Thus, acetic acid is extracted from the liquid composition (α), which is mainly composed of water and acetic acid, using vinyl acetate, separating the liquid composition containing vinyl acetate and acetic acid into a liquid composition containing water. Preferably, in the extraction tower, the aforementioned liquid composition (α) is convectively contacted with vinyl acetate to separate the liquid composition containing vinyl acetate and acetic acid into a liquid composition containing water. More preferably, the liquid composition (α) is introduced from the upper part of the extraction tower, and vinyl acetate is introduced from the lower part of the extraction tower, so that the liquid composition (α) and vinyl acetate come into convective contact. The liquid composition containing vinyl acetate and acetic acid is taken out from the upper part of the extraction tower, and the liquid composition containing water is taken out from the lower part of the extraction tower. Since the specific gravity of the aqueous phase is higher than that of the oil phase, this configuration is suitable. Preferably, the liquid composition containing vinyl acetate and acetic acid separated in this way through step (4) is introduced into a distillation tower. The total content of vinyl acetate and acetic acid in the liquid composition containing vinyl acetate and acetic acid is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The water content in the liquid composition containing water is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0032] Preferably, the process also includes a step (5) in which the liquid composition separated in step (2) is introduced into a distillation column for distillation. In this case, it is preferable to introduce the liquid composition (β) taken from the outlet (B) in step (3) into the distillation column, and it is also preferable to introduce the liquid composition containing vinyl acetate and acetic acid separated in step (4) into the distillation column. Furthermore, it is more preferable to supply the liquid composition separated in step (2), the liquid composition (β), and the liquid composition separated in step (4) together in the distillation step (5). A vinyl acetate fraction, a water fraction, and an acetic acid fraction are obtained from the mixture containing vinyl acetate, acetic acid, and water by distillation. Each fraction may contain small amounts of other components. According to the suitable manufacturing method of the present invention, most of the water used for gas cleaning in step (3) can be removed in step (4) by a liquid-liquid extraction operation. Thus, separation can be achieved through phase separation of the aqueous and oil phases with almost no energy required, and therefore, the amount of water evaporated in the distillation of step (5) is small. As a result, energy consumption can be reduced. If steam is used as a heat source, the amount of steam can be reduced. Alternatively, it is also preferable to optionally purify the vinyl acetate obtained in step (5) and then use it in step (4) to extract acetic acid.

[0033] Furthermore, the process preferably includes step (6): In step (3), after the aforementioned gaseous composition is washed with acetic acid and water to separate it into a gaseous composition containing ethylene and carbon dioxide and a liquid composition containing vinyl acetate, the aforementioned gaseous composition containing ethylene and carbon dioxide is introduced into a carbon dioxide removal system to separate ethylene and carbon dioxide. It is also preferable to introduce the ethylene separated in step (6) into the reactor of the aforementioned step (1) for use in the synthesis reaction of vinyl acetate. Preferably, when a portion of the gaseous composition from the separation device of step (2) is supplied to step (3) and subsequent step (6), the ethylene separated in step (6) and the remainder of the gaseous composition from the separation device of step (2) are combined, and after further addition of ethylene, acetic acid and oxygen, it is introduced into the reactor of the aforementioned step (1) for use in the synthesis reaction of vinyl acetate. By recycling the gaseous composition containing unreacted raw materials in this way, vinyl acetate can be produced efficiently and refined. Example

[0034] [Example 1] use Figure 1The apparatus shown is used to produce vinyl acetate. A circulating gas containing ethylene is introduced into an acetic acid evaporator 1 through conduit 11. Acetic acid, which has been vaporized in the acetic acid evaporator 1, is mixed into the circulating gas and discharged through conduit 12. After oxygen is supplied to the circulating gas in conduit 12, it is introduced into reactor 2. After the vinyl acetate synthesis reaction takes place in reactor 2, the crude product is withdrawn into conduit 13. This crude product contains vinyl acetate and water generated by the reaction in reactor 2, ethylene, acetic acid, and oxygen as unreacted substances, and carbon dioxide as a byproduct.

[0035] The aforementioned crude product is introduced through conduit 13 into gas separation tower 3. Liquid acetic acid is introduced from the top of the tower to contact the gas, thereby separating it into a liquid composition containing vinyl acetate, acetic acid, and water, and a gaseous composition containing ethylene, oxygen, carbon dioxide, vinyl acetate, acetic acid, and water. The resulting liquid composition is introduced into distillation tower 4 via conduit 14. The aforementioned gaseous composition is then introduced into compressor 5 via conduit 15, and the compressed gaseous composition is introduced into conduit 16. Approximately 95% by mass of this gaseous composition is supplied to conduit 11 via conduit 16, and the remaining approximately 5% by mass is supplied to conduit 17.

[0036] The aforementioned gaseous composition, approximately 5% by mass, is introduced into the lower part of the gas scrubbing tower 6 through conduit 17. In the gas scrubbing tower 6, water is supplied from the inlet, and acetic acid is supplied from the inlet on its lower side. A liquid composition (α) containing acetic acid and water is drawn from the outlet (A) located between the water inlet and the acetic acid inlet into conduit 20. Additionally, a liquid composition (β) containing vinyl acetate and acetic acid is drawn from the outlet (B) located at the lower part of the gas scrubbing tower 6 into conduit 21. Furthermore, a gaseous composition containing ethylene, carbon dioxide, and oxygen is drawn from the upper part of the gas scrubbing tower 6 into conduit 18. The total content of acetic acid and water in the liquid composition (α) is approximately 100% by mass, the total content of vinyl acetate and acetic acid in the liquid composition (β) is approximately 99% by mass, and the water content is approximately 1% by mass. It should be noted that the gas scrubbing tower 6, from top to bottom, has an outlet for the gaseous composition, a water inlet, an outlet (A), an acetic acid inlet, a gaseous composition inlet, and an outlet (B).

[0037] The gaseous composition taken from the gas scrubbing tower 6 is introduced into the CO2 removal system 7 via conduit 18. After carbon dioxide removal, it is introduced into conduit 11, where ethylene is further introduced before being returned to the acetic acid evaporator 1. That is, from the acetic acid evaporator 1 through conduits 12, 13, 15, 16, and 11, most of the gaseous composition is circulated. The remaining portion of the gaseous composition is decarbonized via conduits 17, 18, 19, and 11 and then returned to the acetic acid evaporator 1 for further circulation. This prevents the accumulation of carbon dioxide as a byproduct in the circulating gas, thus preventing an increase in its concentration.

[0038] The liquid composition (β) taken from the gas scrubbing tower 6 is introduced into the distillation tower 4 via conduit 21. Additionally, the liquid composition (α) taken from the gas scrubbing tower 6 is introduced into the upper part of the acetic acid extraction tower 8 via conduit 20. The acetic acid extraction tower 8 is a tower-type liquid-liquid extraction device, which, from top to bottom, has an outlet for a liquid composition containing vinyl acetate and acetic acid, an inlet for the liquid composition (α), an inlet for vinyl acetate, and an outlet for a liquid composition containing water.

[0039] A liquid composition (α) containing acetic acid and water is supplied to the upper part of the acetic acid extraction tower 8 through conduit 20, and vinyl acetate (liquid) is supplied to the lower part of the acetic acid extraction tower 8 through conduit 23. This vinyl acetate is obtained from distillation tower 4. Since the density of the liquid composition (α) is higher than that of vinyl acetate, the liquid composition (α) settles while the vinyl acetate rises, and the two undergo convective contact within the acetic acid extraction tower 8. Furthermore, acetic acid is more soluble in vinyl acetate than water, therefore, acetic acid dissolves in the rising vinyl acetate. As a result, a liquid composition containing vinyl acetate and acetic acid is taken out from the upper part of the acetic acid extraction tower 8 and supplied to distillation tower 4 via conduit 24. Additionally, a liquid composition containing water is taken out from the lower part of the acetic acid extraction tower 8. The total content of vinyl acetate and acetic acid in the aforementioned liquid composition containing vinyl acetate and acetic acid is approximately 99% by mass, and the water content in the aforementioned liquid composition containing water is approximately 97% by mass.

[0040] A liquid composition containing vinyl acetate, acetic acid, and water is introduced into distillation column 4 via conduits 14, 21, and 24, and vinyl acetate, acetic acid, and water are separated by distillation. The vinyl acetate obtained by distillation is removed from conduit 22, and a portion of it is supplied to acetic acid extraction column 8 via conduit 23. During continuous operation, the required steam flow rate in distillation column 4 is 16.2 tons / hour.

[0041] [Comparative Example 1] use Figure 2The apparatus shown is used to produce vinyl acetate. Except for the absence of the acetic acid extraction tower 8, the same apparatus as in Example 1 is used to continuously produce vinyl acetate. Because the acetic acid extraction tower 8 is absent, the conduit 20 connecting the gas purging tower 6 and the acetic acid extraction tower 8, the conduit 24 connecting the acetic acid extraction tower 8 and the distillation tower 4, and the conduit 23 connecting the conduit 22 and the acetic acid extraction tower 8 are also absent.

[0042] In the gas scrubbing tower 6, water and acetic acid are supplied from their respective inlets, similar to Example 1, and the gaseous composition is introduced into the CO2 removal system 7 via conduit 18. On the other hand, the liquid composition obtained in the gas scrubbing tower 6 is entirely withdrawn from the outlet located at the bottom of the gas scrubbing tower 6 into conduit 21. This liquid composition contains vinyl acetate, acetic acid, and water, with a total content of vinyl acetate and acetic acid of approximately 85% by mass and a water content of approximately 15% by mass. The gas scrubbing tower 6 has, from top to bottom, an outlet for the gaseous composition, a water inlet, an acetic acid inlet, another gaseous composition inlet, and an outlet for the liquid composition. The supply rates of water and acetic acid are the same as in Example 1.

[0043] The aforementioned liquid composition is introduced from the outlet of the gas scrubbing tower 6 into the distillation tower 4 via conduit 21. Additionally, the liquid composition is introduced from the gas separation tower 3 into the distillation tower 4 via conduit 14. Distillation is carried out in the distillation tower 4 to separate vinyl acetate, acetic acid, and water. During continuous operation, the required steam flow rate in the distillation tower 4 is 18.0 tonnes / hour. Since a larger amount of water needs to be separated in the distillation tower 4, more steam is required than in Example 1.

[0044] Explanation of reference numerals in the attached figures 1 Acetic acid evaporator 2 Reactor 3 Gas Separation Tower 4. Distillation Column 5 Compressors 6. Gas cleaning tower 7 CO2 Removal System 8 Acetic acid extraction tower 11~24 catheters

Claims

1. A method for manufacturing vinyl acetate, comprising at least the following steps: Step (1) involves reacting ethylene, acetic acid, and oxygen to obtain a crude product containing vinyl acetate. Step (2) separates the aforementioned crude product into a liquid composition containing vinyl acetate, acetic acid, and water, and a gaseous composition containing ethylene and vinyl acetate; and Step (3) involves introducing at least a portion of the aforementioned gaseous composition into a gas scrubbing tower, whereby the gaseous composition is scrubbed with acetic acid and water, thereby removing vinyl acetate from the gaseous composition. The aforementioned gas cleaning tower has at least an outlet (A) and an outlet (B). The liquid composition (α) taken from the aforementioned outlet (A) contains acetic acid and water, and the total content of acetic acid and water in the aforementioned liquid composition (α) is 70% by mass or more. The liquid composition (β) taken out from the aforementioned outlet (B) contains vinyl acetate and acetic acid, wherein the total content of vinyl acetate and acetic acid in the aforementioned liquid composition (β) is 90% by mass or more, and the water content is 10% by mass or less.

2. The manufacturing method according to claim 1, wherein, The aforementioned outlet (A) is located above the aforementioned outlet (B).

3. The manufacturing method according to claim 1 or 2, wherein, The aforementioned gas cleaning tower has an acetic acid inlet and a water inlet, and the aforementioned outlet (A) is located above the aforementioned acetic acid inlet and below the aforementioned water inlet.

4. The manufacturing method according to claim 1 or 2 further includes step (4): introducing the aforementioned liquid composition (α) into an extraction tower, extracting acetic acid with vinyl acetate, and separating it into a liquid composition containing vinyl acetate and acetic acid and a liquid composition containing water.

5. The manufacturing method according to claim 4, wherein, In the aforementioned extraction tower, the aforementioned liquid composition (α) is brought into convective contact with vinyl acetate, thereby separating it into a liquid composition containing vinyl acetate and acetic acid, and a liquid composition containing water.

6. The manufacturing method according to claim 5, wherein, The liquid composition (α) is introduced from the upper part of the aforementioned extraction tower, and vinyl acetate is introduced from the lower part of the aforementioned extraction tower, so that the liquid composition (α) and vinyl acetate come into convective contact. A liquid composition containing vinyl acetate and acetic acid is taken out from the upper part of the aforementioned extraction tower, and a liquid composition containing water is taken out from the lower part of the aforementioned extraction tower.

7. The manufacturing method according to claim 1 or 2, further comprising step (5): introducing the liquid composition separated by the aforementioned step (2) into a distillation column for distillation.

8. The manufacturing method according to claim 7, further comprising the step of introducing the aforementioned liquid composition (β) into the aforementioned distillation column.

9. The manufacturing method according to claim 7, further comprising the step of introducing the liquid composition containing vinyl acetate and acetic acid separated by the aforementioned step (4) into the aforementioned distillation column.

10. The manufacturing method according to claim 7, wherein, In the aforementioned distillation column, it is separated into vinyl acetate, acetic acid, and water.

11. The manufacturing method according to claim 10, wherein, The vinyl acetate obtained through the aforementioned step (5) may be purified and then used in the aforementioned step (4).

12. The manufacturing method according to claim 1 or 2, wherein, In the aforementioned step (3), the aforementioned gaseous composition is washed with acetic acid and water, thereby separating it into a gaseous composition containing ethylene and carbon dioxide and a liquid composition containing vinyl acetate. The manufacturing method further includes step (6): introducing the aforementioned gaseous composition containing ethylene and carbon dioxide into a carbon dioxide removal system to separate it into ethylene and carbon dioxide. The ethylene separated by the aforementioned process (6) is used in the aforementioned process (1).

Images