KR20240026766A - Method for purifying vinyl acetate - Google Patents

Abstract

The present invention provides a step of (S1) supplying a reaction mixture containing vinyl acetate monomer (VAM) and methanol to a pre-separation tower to obtain a top stream containing vinyl acetate monomer, (S2) supplying a reaction mixture containing vinyl acetate monomer (VAM) and methanol to a pre-separation tower. Supplying the upper stream and water to a monomer recovery tower to separate them into an upper stream rich in vinyl acetate monomer and a lower stream containing methanol, (S3) condensing the upper stream of the monomer recovery tower and then producing vinyl acetate as an organic phase in a decanter. Providing a method for purifying vinyl acetate comprising the steps of separating a monomer-rich layer and an aqueous layer of water, and (S4) supplying the organic phase separated in the decanter to a monomer purification tower to obtain purified vinyl acetate monomer at the bottom. do.

Description

Method for purifying vinyl acetate {METHOD FOR PURIFYING VINYL ACETATE}

The present invention relates to a method for purifying vinyl acetate, and more specifically, to a method for recovering unreacted vinyl acetate monomers generated in the production process of ethylene vinyl alcohol with high purity.

Ethylene vinyl alcohol (EVOH) has excellent properties such as gas barrier properties, chemical resistance, and mechanical strength, and is widely used as a coating material to protect metal, paper, wood, etc., and as a packaging material for food.

Such EVOH can be generally produced by hydrolyzing polyethylene vinyl acetate obtained by copolymerization of ethylene monomer and vinyl acetate monomer (VAM) in an alcohol-based solvent such as methanol. In this copolymerization, a significant amount of the monomers remain unreacted and must be separated in the EVOH reactor along with the solvent used.

Generally, in the EVOH production process, a distillation method using gaseous methanol is used to recover unreacted vinyl acetate monomer from the copolymerization solution. For example, in Domestic Patent No. 10-0508071, a post-copolymerization solution is introduced into the upper part of the distillation tower and gaseous methanol is introduced into the lower part, so that ethylene-vinyl acetate copolymer (b.p. about 171°C) with a high boiling point is formed at the lower part of the distillation tower. The process of recovering the solution and recovering unreacted vinyl acetate monomer and gaseous methanol together from the top is disclosed.

Since the vinyl acetate monomer recovered from the top of the distillation column contains a large amount of methanol, a process of separating it is necessary. The vinyl acetate monomer (b.p. about 73°C) and methanol (b.p. about 65°C) form an azeotropic composition, and the separation of the vinyl acetate monomer from the azeotropic composition occurs between the vinyl acetate monomer and water by adding water. It is performed using a distillation method using liquid-liquid phase equilibrium. For example, when water is introduced into a distillation tower containing an azeotropic mixture of vinyl acetate monomer and methanol, the azeotrope of vinyl acetate monomer-methanol is broken by the water, resulting in a (VAM-rich) stream containing a large number of vinyl acetate monomers at the top of the distillation tower. is discharged, and a mixed stream of methanol and water is discharged from the bottom.

Thereafter, the methanol and water discharged to the bottom of the distillation tower are separated from each other by distillation, but when the content of methanol in the feed is high, there is a problem that a lot of energy is consumed to separate the methanol.

KR 10-0508071 B

The present invention is intended to solve the problems mentioned in the technology behind the invention. When separating unreacted vinyl acetate monomer (VAM) and methanol generated in the production of ethylene vinyl alcohol, if the methanol content is high, it is removed in advance. The aim is to provide a method for purifying vinyl acetate monomer that can reduce the amount of energy consumed in the process.

According to one aspect of the present invention for solving the above problem,

(S1) supplying a reaction mixture containing vinyl acetate monomer (VAM) and methanol to a pre-separation tower to obtain a top stream containing vinyl acetate monomer,

(S2) supplying the upper stream and water of the pre-separation tower to a monomer recovery tower to separate them into an upper stream rich in vinyl acetate monomer and a lower stream containing methanol,

(S3) condensing the upper stream of the monomer recovery tower and then separating it into a vinyl acetate monomer-rich layer as an organic phase and an aqueous layer of water in a decanter, and

(S4) A method for purifying vinyl acetate is provided, including the step of supplying the organic phase separated in the decanter to a monomer purification tower to obtain purified vinyl acetate monomer at the bottom.

Additionally, the upper stream of the pre-separation tower can be heated by compression and used for heat exchange with the stream separated at the bottom of the downstream distillation tower.

According to the present invention, when separating unreacted vinyl acetate monomer and methanol generated in the production process of ethylene vinyl alcohol (EVOH), if the methanol content is high, methanol is removed in advance using a pre-separation tower and consumed throughout the process. It reduces the amount of energy and can contribute to additional energy reduction by raising the temperature of the upper stream of the pre-separation tower and using it for heat exchange with the stream separated at the bottom of the downstream distillation tower.

Figures 1 and 2 each schematically show the process of purifying vinyl acetate monomer (VAM) by applying a pre-separation tower according to an embodiment of the present invention.
Figure 3 schematically shows the vinyl acetate monomer purification process according to Comparative Example 1.

Terms or words used in the description and claims of the present invention should not be construed as limited to their usual or dictionary meanings, and the inventor should appropriately use the concepts of terms to explain his invention in the best way. Based on the principle of definability, it must be interpreted with meaning and concept consistent with the technical idea of the present invention.

As used herein, the meaning of 'comprising' or 'containing' specifies a specific characteristic, area, integer, step, operation, element, or ingredient, and the addition of another specific characteristic, area, integer, step, operation, element, or ingredient. It is not excluded.

As used herein, the term 'top' refers to a point of 0 to 5% height from the top of the device, unless otherwise specified, and may specifically mean the top (top). Additionally, the term 'bottom' refers to a point at a height of 95 to 100% from the top of the device, and may specifically mean the bottom (bottom of the tower).

The term 'stream' used herein may refer to the flow of fluid within a process, or may also refer to the fluid itself flowing within a pipe. Specifically, the stream may refer to both the fluid itself and the flow of the fluid flowing within the pipes connecting each device. Additionally, the fluid may include any one or more of gas, liquid, and solid.

One embodiment of the present invention relates to a purification method for recovering unreacted vinyl acetate monomer (VAM) generated in the production process of ethylene vinyl alcohol (EVOH) with high purity.

Hereinafter, the purification method of the present invention will be described in detail with reference to the attached drawings.

1 to 2 schematically show a method for purifying vinyl acetate monomer according to an embodiment of the present invention. The purification method of the present invention includes a pre-separation tower (10), a monomer recovery tower (100), and a decanter (20, 30). ), a monomer purification tower (200), and a methanol separation tower (300).

Referring to FIG. 1, in the method for purifying vinyl acetate monomer according to an embodiment of the present invention, a reaction mixture containing vinyl acetate monomer (VAM) and methanol is first prepared and supplied to the pre-separation tower 10 (S1) ).

The reaction mixture of vinyl acetate monomer and methanol is an azeotropic mixture recovered in the EVOH production process. The reaction mixture is a copolymerization solution of ethylene monomer and vinyl acetate monomer in EVOH production, and then the solution is introduced into the upper part of the distillation tower, and methanol is added to the lower part of the distillation tower. By introducing a solution of ethylene-vinyl acetate copolymer with a high boiling point from the bottom of the distillation tower, unreacted vinyl acetate monomer and gaseous methanol can be recovered together from the top of the distillation tower.

The reaction mixture may contain 80 to 90% by weight, specifically 85 to 90% by weight, of methanol based on the total weight.

In order to reuse the vinyl acetate monomer contained in the reaction mixture for the production of EVOH, it must be separated from methanol. If the methanol content in the reaction mixture is high, a lot of energy is consumed when methanol is removed to the top during azeotropic distillation using water. do.

Accordingly, in the present invention, in order to remove methanol in advance, the reaction mixture is supplied to the pre-separation tower (10), a part of the methanol (12) is pre-separated and discharged at the bottom, and a stream (11) containing vinyl acetate monomer is discharged at the top. ) to get

The pre-separation tower 10 corresponds to a distillation tower capable of separating the components constituting the reaction mixture by selective heating and condensation, and can be designed with materials, sizes, and operating methods commonly applied in the field. There are no special restrictions. For example, the reaction mixture supplied to the tower is heated by heat provided from a reboiler connected to the bottom of the tower, the generated vapor moves to the top of the tower and is discharged, and the discharged vapor is partially discharged from a condenser attached to the top of the tower. Or it can be completely condensed. Meanwhile, part of the condensate can be recycled back to the tower.

In one embodiment of the present invention, the line separation tower 10 is operated at a temperature of 30 to 90 ° C. (e.g., 60 to 65 ° C.) at a pressure of 0.5 to 4 bar or 0.5 to 3 bar (e.g., normal pressure of 1 bar). You can. When the above operating conditions are met, most of the methanol contained in a high content in the reaction mixture is discharged to the bottom stream, and vinyl acetate monomer and remaining methanol can be separated in an azeotropic form at the top.

The content of methanol discharged from the bottom of the pre-separation tower may be 10 to 90% by weight, specifically 50 to 90% by weight, of the methanol contained in the reaction mixture, and the above content of methanol is extracted from the reaction mixture supplied as a feed. By removing it in advance, the amount of energy consumed in the later process of purifying vinyl acetate monomer can be reduced.

Meanwhile, the upper stream 11 of the pre-separation tower may contain an azeotropic mixture of vinyl acetate monomer-methanol and trace amounts of by-products such as methyl acetate and acetaldehyde, and the vinyl acetate monomer and methanol are mixed in a ratio of 1:2 to 1:2. It may be included in a weight ratio of 9 or 1:3 to 1:9, but is not particularly limited thereto.

Referring to FIG. 2, the upper stream 11 of the pre-separation tower may be heated by compression through a condenser before being supplied to the monomer recovery tower 100, and the heated stream may be separated at the bottom of the downstream distillation tower. Heat may be exchanged by contact with one or more of the streams.

To illustrate, the stream 11 containing vinyl acetate monomer and residual methanol in azeotropic form is separated at about 60°C at the top of the pre-separation tower 10, and then attached to the top of the pre-separation tower. It may be compressed in a condenser to 3 to 7 bar, specifically 4 to 6 bar, and raised to 130 to 190°C, specifically 140 to 180°C.

The heated stream moves to a reheater connected to the bottom of each of the monomer recovery tower 100, monomer purification tower 200, or methanol separation tower 300, and heat exchanges the stream separated at the bottom of the downstream distillation tower. It can be preheated.

This heat exchange contributes to reducing the energy consumed in the recovery and purification steps of vinyl acetate monomer and the recovery of residual methanol, thereby reducing the energy usage of the entire process.

Meanwhile, the temperature increase range due to the heat exchange may vary depending on the type of distillation column, operating conditions, latent heat conversion rate, etc.

Next, the stream 11 containing the vinyl acetate monomer and residual methanol separated at the top of the pre-separation tower is supplied to the monomer recovery tower 100, and is converted into an upper stream rich in vinyl acetate monomer and a lower stream containing methanol. Separate.

The monomer recovery tower 100 corresponds to a distillation tower capable of separating vinyl acetate monomer and residual methanol by azeotropic distillation using water, and can be designed with materials, sizes, and operating methods commonly applied in the field, and can be designed with special There are no limits.

In one embodiment of the present invention, the monomer recovery tower 100 may be operated at a temperature of 40 to 90°C or 50 to 85°C at a pressure of 0.5 to 4 bar or 0.5 to 3 bar (for example, normal pressure of 1 bar). . When the above operating conditions are met, the azeotrope of the methanol-vinyl acetate monomer is broken due to water and a new azeotropic mixture of water-vinyl acetate monomer is formed, and the methanol has high solubility in water, so it is removed from the recovery tower (100) by water with a high specific gravity. It moves to the bottom, and the vinyl acetate monomer can be separated by moving to the top of the recovery tower 100 in the form of an azeotropic mixture with water.

The stream 110 separated at the top of the monomer recovery tower 100 will contain 30 to 70% by weight of vinyl acetate monomer, 5 to 50% by weight of water, and 10 to 30% by weight of methanol that was not separated, based on the total weight. You can.

In addition, the stream 120 separated from the bottom of the monomer recovery tower 100 may contain 20 to 60% by weight of methanol, 20 to 60% by weight of water, and 5 to 20% by weight of vinyl acetate monomer based on the total weight. .

Thereafter, the upper stream 110 of the monomer recovery tower 100 is partially or completely condensed in a condenser connected to the top of the recovery tower and then passes through the decanter 20 (S3).

The condensation temperature of the upper stream 110 may be in the range of 35 to 45 ℃, for example, 38 to 42 ℃, and the stream condensed in the above temperature range passes through the decanter 20 and passes through the aqueous layer 21 of water and the vinyl organic phase. Liquid-liquid separation can be achieved with an acetate monomer-rich layer (22).

The decanter 20 is a device for separating immiscible fluids using gravity or centrifugal force due to density differences. Relatively light liquids can be separated into the upper part of the decanter, and relatively heavy liquids can be separated into the lower part of the decanter. there is. The aqueous layer 21 separated in the decanter 20 is re-supplied to the monomer recovery tower 100, and the vinyl acetate monomer-rich layer 22 can be moved to the downstream purification tower.

The vinyl acetate monomer-rich layer 22 may include 70 to 99.9% by weight of vinyl acetate monomer based on the total weight, and methanol and water may additionally remain.

Meanwhile, the methanol-containing stream 120 separated from the bottom of the monomer recovery tower 100 may be supplied to the methanol separation tower 300.

The methanol separation tower 300 corresponds to a distillation tower capable of separating methanol from water by boiling and condensing the stream 120, and can be designed with materials, sizes, and operating methods commonly applied in the field, and can be designed with special materials, sizes, and operation methods. There are no limits.

In one embodiment of the present invention, the methanol separation tower 300 may be operated at a temperature of 60 to 100°C, for example, 65 to 100°C, at a pressure of 0.5 to 1.5 bar or 0.5 to 1 bar (for example, normal pressure of 1 bar). And under these conditions, low boiling point methanol can be separated into the top stream (310). When it is necessary to lower the operating temperature for heat exchange, the methanol separation tower 300 can be controlled to operate at a lower pressure than other process towers.

Thereafter, the top stream of methanol can be partially or completely condensed in a condenser and then recovered as an exhaust stream, and a portion of the condensed methanol can be fed back into the tower. Meanwhile, water with a higher boiling point than methanol can be separated into the lower stream 320 of the methanol separation tower 300, and then some of it is reheated and re-supplied into the methanol separation tower 300, and the remainder is process water 321. It can be recovered.

The water recovered from the bottom of the methanol separation tower (300) may be combined with the moving line of the water layer separated in the decanter (20) and supplied to the monomer recovery tower (100). Make-up water may also be added to the recovered water moving stream 321.

In this way, when supplementary water is introduced into the decanter 20, it is advantageous to control the amount of water used to separate the vinyl acetate monomer from methanol, and through this, the vinyl acetate monomer is separated from the reaction mixture of vinyl acetate monomer and methanol to produce high purity product. It is possible to achieve the effect of minimizing energy consumption while controlling the amount of water used to obtain it to an optimal level.

In one embodiment of the present invention, the total flow rate of the make-up water and recovered water may be in the range of 30 to 150% by weight, specifically 60 to 80% by weight, of the stream flow rate supplied to the monomer recovery tower (100). When the above flow rate range is satisfied, there is an effect of minimizing energy consumption in the purification process while increasing the efficiency of separating vinyl acetate monomer with high purity from the reaction mixture.

Specifically, if the total flow rate of the make-up water and recovered water is less than 30% by weight of the feed stream flow rate of the recovery tower 100, the water consumed for separation of the feed stream cannot be sufficiently supplied, resulting in reduced separation efficiency or separation itself. It can be difficult. On the other hand, when the total flow rate of the makeup water and recovered water exceeds 150% by weight of the feed stream flow rate, the separation efficiency of unreacted vinyl acetate monomer and methanol can be increased as the water input amount increases, but energy consumption increases. There is a problem of excessive increase in operating costs.

Thereafter, the vinyl acetate monomer-rich stream 22, which is the organic phase separated in the decanter 20, can be supplied to the monomer purification tower 200 to obtain purified vinyl acetate monomer at the bottom (S4).

The monomer purification tower 200 corresponds to a distillation tower capable of separating vinyl acetate monomer with high purity by boiling and condensing the vinyl acetate monomer-rich stream, and is commonly used in the field like the monomer recovery tower 100 described above. It can be designed with the applied material, size, and operation method, and there are no special restrictions.

In one embodiment of the present invention, the monomer purification tower 200 may be operated at a temperature of 45 to 75°C, for example, 60 to 75°C, at a pressure of 0.5 to 4 bar or 0.5 to 3 bar (e.g., normal pressure of 1 bar). there is. When the above operating conditions are met, components with a lower boiling point than vinyl acetate monomer can be obtained by being separated into an upper stream (210), and vinyl acetate monomer can be separated into a lower stream (220).

Additionally, the top stream 210 of the monomer purification tower 200 may include vinyl acetate monomer, methanol, and water, and is partially or completely condensed in a condenser connected to the top of the purification tower 200. Passing through the decanter 30, the vinyl acetate monomer can be separated into an organic layer 31 and an aqueous layer 32, where the aqueous layer 32 is transferred to the monomer recovery tower 100, and the organic layer 31 is transferred to the purification tower 200. ) can be resupplied.

As described above, in the present invention, in the process of separating unreacted vinyl acetate monomer and methanol generated in the EVOH manufacturing process, methanol is removed in advance using a line separation column to reduce the amount of energy consumed throughout the process, and the line By raising the temperature of the upper stream of the separation column and using it for heat exchange with the stream separated at the bottom of the downstream distillation column, it can contribute to additional energy reduction.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are intended to illustrate the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, and the scope of the present invention is not limited to these alone.

Example 1:

According to the process shown in Figure 1, vinyl acetate monomer (VAM) was purified from a reaction mixture containing vinyl acetate monomer (VAM) and methanol.

First, a reaction mixture containing vinyl acetate monomer (63 kg/hr) and methanol (537 g/hr) is supplied to the pre-separation tower (10), and the pre-separation tower (10) is heated to 60°C at the top and 60°C at the bottom at normal pressure (1 bar). It was operated at 65°C to obtain an upper stream (11) containing vinyl acetate monomer, and methanol was pre-separated and discharged to the bottom.

The upper stream 11 and water of the pre-separation tower 10 are supplied to the monomer recovery tower 100, and the monomer recovery tower 100 is operated at an upper temperature of 60°C and a lower temperature of 85°C at normal pressure (1 bar) to produce vinyl. It was separated into an upper stream (110) rich in acetate monomers and a lower stream (120) containing residual methanol.

The upper stream 110 rich in vinyl acetate monomer is cooled to 40° C. in a condenser connected to the top of the monomer recovery tower 100, and then passed through a decanter 20 to produce an aqueous layer of water 21 and an organic phase, vinyl acetate monomer- Liquid-liquid separation was performed using a rich layer (22).

Meanwhile, the methanol-containing stream 120 separated from the bottom of the monomer recovery tower 100 is supplied to the methanol separation tower 300, and the methanol separation tower 300 is operated at 65° C. at the top and 65° C. at the bottom at normal pressure (1 bar). It was operated at 100°C and separated into an upper stream of methanol (310) and a lower stream of water (320). At this time, the water recovered from the lower part of the methanol separation tower 300 was combined with the moving stream 321 of the water layer separated in the decanter 20 and supplied back to the monomer recovery tower 100, and the recovered water was further transferred. Make-up water was supplied to the line.

The organic phase (vinyl acetate monomer-rich stream) separated in the decanter 20 is supplied to the monomer purification tower 200 and operated at 60°C in the upper part and 72°C in the lower part at normal pressure (1 bar) to purify components with a lower boiling point than vinyl acetate monomer. Separated into an upper stream (210) and a lower stream (220) of vinyl acetate monomer. The bottoms stream was obtained as high purity (>98%) vinyl acetate monomer.

Example 2:

As shown in FIG. 2, the upper stream 11 of the pre-separation tower 10 is compressed to 6 bar in a condenser and the temperature is raised to 173°C, and then the heated stream is transferred to the monomer recovery tower 100, which is the downstream distillation tower, and the monomer Vinyl acetate monomer was obtained by performing the same process as Example 1, except for heat exchange with one or more streams of the purification tower (200) and the methanol separation tower (300).

Specifically, the heat exchange transfers the stream heated to 173°C in the condenser to a reheater connected to each lower part of the monomer recovery tower 100, monomer purification tower 200, and methanol separation tower 300 to the lower part of the downstream distillation tower. This was carried out by sequential contact with the stream. The temperature of the raised stream was 114°C after heat exchange, and the temperature was maintained at 114°C due to latent heat even when heat exchange was performed sequentially with the lower streams of the subsequent distillation columns.

Example 3:

As shown in FIG. 2, the upper stream 11 of the pre-separation tower 10 is compressed to 4 bar in a condenser and the temperature is raised to 147°C, and then the heated stream is transferred to the monomer recovery tower 100, which is the downstream distillation tower, and the monomer The same process as in Example 1 was performed, except that heat was exchanged with one or more streams of the purification tower (200) and the methanol separation tower (300), and the methanol separation tower (300) was operated under conditions of 0.5 bar and 100 ° C. Thus, vinyl acetate monomer was obtained.

Specifically, the heat exchange transfers the stream heated to 147°C in the condenser to a reheater connected to each lower part of the monomer recovery tower 100, the monomer purification tower 200, and the methanol separation tower 300 to the lower part of the downstream distillation tower. This was carried out by sequential contact with the stream. The temperature of the raised stream was 100°C after heat exchange, and the temperature was maintained at 100°C due to latent heat even when heat exchange was performed sequentially with the lower streams of the subsequent distillation columns.

Comparative Example 1: Method for purifying vinyl acetate monomer without applying a pre-separation tower

As shown in FIG. 3, vinyl acetate monomer was purified from a reaction mixture containing vinyl acetate monomer and methanol according to a process without applying the pre-separation tower 10.

First, a reaction mixture containing vinyl acetate monomer (63 kg/hr) and methanol (537 g/hr) is supplied together with water to the monomer recovery tower 100, and the monomer recovery tower 100 is operated at atmospheric pressure (1 bar) at the upper part 66. ℃ and the lower stream was operated at 75 ℃ and 75 ℃ and separated into an upper stream (110) rich in vinyl acetate monomer and a lower stream (120) containing residual methanol.

The upper stream 110 rich in vinyl acetate monomer is cooled to 40° C. in a condenser connected to the top of the monomer recovery tower 100, and then passed through a decanter 20 to produce an aqueous layer of water 21 and an organic phase, vinyl acetate monomer- Liquid-liquid separation was performed using a rich layer (22).

Meanwhile, the methanol-containing stream 120 separated from the bottom of the monomer recovery tower 100 is supplied to the methanol separation tower 300, and the methanol separation tower 300 is operated at 65° C. at the top and 65° C. at the bottom at normal pressure (1 bar). It was operated at 100°C and separated into an upper stream of methanol (310) and a lower stream of water (320). At this time, the water recovered from the lower part of the methanol separation tower 300 was combined with the moving stream 321 of the water layer separated in the decanter 20 and supplied back to the monomer recovery tower 100, and the recovered water was further transferred. Make-up water was supplied to the line.

The organic phase (vinyl acetate monomer-rich stream) separated in the decanter 20 is supplied to the monomer purification tower 200, and operated at 62°C in the upper part and 73°C in the lower part at normal pressure (1 bar) to purify components with a lower boiling point than vinyl acetate monomer. Separated into an upper stream (210) and a lower stream (220) of vinyl acetate monomer.

Table 1 below shows the operating conditions and energy consumption of each distillation column applied in Examples 1 to 3 and Comparative Example 1.

As can be seen in Table 1, in Examples 1 to 3, energy was generated due to the operation of the pre-separation tower 10, but as the energy consumption of the subsequent process was greatly reduced, the total energy of the vinyl acetate monomer purification process was reduced. It decreased compared to Comparative Example 1.

In particular, in Examples 2 and 3, the upper stream of the pre-separation tower 10 was heated and used for heat exchange at least one of the lower streams of the monomer recovery tower 100, the monomer purification tower 200, and the methanol separation tower 300. Accordingly, it can be confirmed that no energy was consumed to raise the temperature in the downstream distillation tower.

1: Feed Stream
10: Line separation tower
11: Upper stream separated in pre-separation tower
12: Bottom stream separated in pre-separation tower
20, 30: Decanter
21, 22, 31, 32: Separated layers in decanter
100: Monomer recovery tower
110: Top stream separated from monomer recovery tower
120: Bottom stream separated from monomer recovery tower
200: Monomer purification tower
210: Top stream separated from monomer purification tower
220: Bottom stream separated from monomer purification tower
300: Methanol separation tower
310: Top stream separated in methanol separation tower
320, 321: Bottom stream separated in the methanol separation tower

Claims (11)

(S1) supplying a reaction mixture containing vinyl acetate monomer (VAM) and methanol to a pre-separation tower to obtain a top stream containing vinyl acetate monomer,
(S2) supplying the upper stream and water of the pre-separation tower to a monomer recovery tower to separate them into an upper stream rich in vinyl acetate monomer and a lower stream containing methanol,
(S3) condensing the upper stream of the monomer recovery tower and then separating it into a vinyl acetate monomer-rich layer as an organic phase and an aqueous layer of water in a decanter, and
(S4) A method for purifying vinyl acetate comprising the step of supplying the organic phase separated in the decanter to a monomer purification tower to obtain purified vinyl acetate monomer at the bottom. According to paragraph 1,
In step (S1), the reaction mixture contains 80 to 90% by weight of methanol based on the total weight, and a portion of the methanol is discharged to the bottom of the pre-separation tower. According to paragraph 2,
A method for purifying vinyl acetate wherein the content of methanol discharged from the bottom of the pre-separation tower is 10 to 90% by weight of the methanol contained in the reaction mixture. According to paragraph 1,
A method for purifying vinyl acetate in which the bottom stream of the monomer recovery tower is supplied to a methanol separation tower and separated into an upper stream of methanol and a lower stream of water. According to any one of claims 1 to 4,
The upper stream of the pre-separation tower is heated by compression and then used for heat exchange of one or more of the streams separated at the bottom of the monomer recovery tower, monomer purification tower, and methanol separation tower. According to clause 5,
A method for purifying vinyl acetate in which the temperature of the upper stream of the pre-separation tower is raised to 130 to 190 ° C. According to clause 5,
A method for purifying vinyl acetate, wherein the upper stream of the heated pre-separation tower is maintained at a temperature of 90 to 120 ° C. after heat exchange. According to any one of claims 1 to 4,
A method for purifying vinyl acetate in which water recovered from the bottom of the methanol separation tower is supplied to a decanter along with makeup water. According to paragraph 1,
A method for purifying vinyl acetate, wherein the upper stream of the monomer purification tower is fed back to the monomer recovery tower. According to paragraph 1,
A method for purifying vinyl acetate in which the monomer recovery tower and the monomer purification tower are each operated at a pressure of 0.5 to 4 bar. According to paragraph 4,
A method for purifying vinyl acetate in which the methanol separation tower is operated at a pressure of 0.5 to 1.5 bar.