Method for removing acetic ether in vinyl acetate by extractive distillation

Abstract

The invention relates to a method and a device for removing ethyl acetate from vinyl acetate by extractive distillation. The device comprises an extraction tower (101), a phase separator (105), an extraction agent recovery tower (102), a separator (103) and a mixer (104). The top of the extraction tower (101) is connected with a phase separator (105), and the bottom of the extraction tower (101) is connected with an extraction agent recovery tower (102); a tower kettle of the extraction agent recovery tower (102) is connected with the separator (103); an upper outlet of the separator (103) is connected with the mixer (104); and an outlet material flow of the mixer (104) is connected with the extraction tower (101). According to the method, one or more of furfural, n-butyl acetate, carbon tetrachloride and trichloromethane are used as extraction agents, and the content of acetic ether in vinyl acetate is reduced to 70 ppm or below through extractive distillation. The device is operated under normal pressure, and is simple in structure, efficient and energy-saving.

Description

Technical Field

[0001] The invention relates to the field of vinyl acetate production, and in particular to a method for removing ethyl acetate from vinyl acetate by extractive distillation. Background Art

[0002] Vinyl acetate (VAC) is an organic compound with a wide range of uses and plays an important role in modern industry. Due to its unsaturated C═C, vinyl acetate can be self-polymerized or copolymerized with other monomers to form high molecular polymers such as polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA) and vinyl chloride-vinyl acetate copolymer (EVC). These polymers are widely used in coatings, leather, hot melt adhesives, textiles, synthetic fibers and waterproof materials.

[0003] At present, there are two main production processes for vinyl acetate: the ethylene process and the acetylene process. Among them, the ethylene process has the advantages of simple process, low energy consumption, environmental friendliness and high selectivity. However, the vinyl acetate produced by the ethylene process contains a small amount of ethyl acetate that is difficult to remove. Ethyl acetate affects the viscosity, volatility and reaction kinetics of vinyl acetate during polymerization, thereby limiting the application of vinyl acetate in adhesives, coatings and polymer materials. Since vinyl acetate and ethyl acetate have similar boiling points and good mutual solubility, traditional distillation methods require a higher reflux ratio to remove ethyl acetate, and the stream of ethyl acetate still contains a large amount of vinyl acetate. Therefore, it is crucial to develop a low-energy consumption, high vinyl acetate yield ethyl acetate removal technology.

[0004] Patent CN 1243118A discloses a method for reducing the concentration of ethyl acetate in vinyl acetate by using water and acetic acid in distillation. In this method, 0.1-5% by weight (based on the crude liquid vinyl acetate raw material) of water and 0.1-60% by weight (based on the crude liquid vinyl acetate raw material) of acetic acid are introduced into the distillation tower from above the crude liquid vinyl acetate raw material feed plate. Water can promote the full dehydration of the crude liquid vinyl acetate raw material, while acetic acid can separate ethyl acetate from vinyl acetate. Although this method does not introduce new impurities and can meet the separation requirements, the large amount of water and acetic acid used leads to high energy consumption in distillation and subsequent recovery of acetic acid. The content of ethyl acetate in the product vinyl acetate separated by this method is 200ppm, which is still relatively high for some high-end applications with high quality requirements for vinyl acetate.

[0005] Patent CN 112209830A invented a method for separating vinyl acetate and ethyl acetate using acetic acid as an extractant. The invention uses acetic acid in the feed as an extractant to increase the relative volatility between vinyl acetate and ethyl acetate. Although the invention reduces the content of vinyl acetate in the ethyl acetate stream from more than 90% to 4%, thereby increasing the yield of vinyl acetate, the content of vinyl acetate in the ethyl acetate stream is still relatively high.

[0006] Patent CN 104030921B invented a method for purifying vinyl acetate using a bulkhead distillation tower. This method extracts ethyl acetate and light components (acetaldehyde, methyl acetate, acrolein) at the bottom of the stripping section and the top of the distillation section, respectively, and obtains a vinyl acetate product on the other side of the bulkhead section. This method simplifies the separation process of vinyl acetate, ethyl acetate, acetaldehyde, methyl acetate and acrolein, but the separated ethyl acetate stream and light component stream still contain a large amount of vinyl acetate. At the same time, this method does not consider the effect of the azeotrope formed between acetic acid, vinyl acetate, water and ethyl acetate on distillation. Summary of the invention

[0007] The purpose of the present invention is to solve at least one of the problems existing in the prior art, and to provide a method for removing ethyl acetate from vinyl acetate. In the method, extractive distillation is used to reduce the content of ethyl acetate in vinyl acetate and the energy consumption. The azeotrope formed between vinyl acetate, acetic acid, water and ethyl acetate in the crude product vinyl acetate will lead to the problems of difficult separation and high energy consumption. The present invention uses one or more of furfural, n-butyl acetate, carbon tetrachloride and chloroform as an extractant, and cooperates with a method for separating ethyl acetate from vinyl acetate. The method can reduce the content of ethyl acetate in vinyl acetate to below 70ppm.

[0008] In order to achieve the above invention object, the specific technical scheme of the present invention is as follows:

[0009] In the extractive distillation process proposed by the present invention, the top of the extraction tower is connected to the phase separator, and the bottom of the tower is connected to the extractant recovery tower; the top of the extractant recovery tower is connected to the reflux tank, and the bottom of the tower is connected to the separator; the upper outlet (rich in extractant) of the separator is connected to the mixer; and the outlet logistics of the mixer is connected to the extraction tower.

[0010] A method for removing ethyl acetate from vinyl acetate by extractive distillation, using one or more of furfural, n-butyl acetate, carbon tetrachloride and chloroform as extractants, and realizing high-efficiency and low-energy separation of crude vinyl acetate from ethyl acetate, acetic acid, water and other heavy components by extractive distillation; specifically comprising the following steps:

[0011] 1) introducing a crude product of vinyl acetate containing vinyl acetate, water, acetic acid and a small amount of heavy components such as acetaldehyde, methyl acetate, ethyl acetate and ethylene glycol diacetate into an extraction tower, and using one or more of furfural, n-butyl acetate, carbon tetrachloride and chloroform as an extractant to introduce the crude product of vinyl acetate into the extraction tower from above a feed plate;

[0012] 2) After extraction and distillation separation, the vapor at the top of the extraction tower is condensed to obtain a mixture of vinyl acetate, water, acetaldehyde, a small amount of methyl acetate and a small amount of ethyl acetate, and the mixture enters a phase separator, and the lower layer of the phase separator obtains an aqueous phase containing a small amount of vinyl acetate and a small amount of acetaldehyde, and the upper layer obtains an organic phase containing vinyl acetate, water, acetaldehyde, methyl acetate and a small amount of ethyl acetate;

[0013] 3) A portion of the organic phase in step (2) is refluxed into the extraction tower, and another portion enters the vinyl acetate refining tower to be purified to obtain a high-purity vinyl acetate product, and the aqueous phase enters the wastewater tower;

[0014] 4) extracting the tower kettle to obtain an acetic acid phase containing a small amount of vinyl acetate, water, ethyl acetate, an extractant, and heavy components such as ethylene glycol diacetate;

[0015] 5) the acetic acid phase in step 4) enters an extractant recovery tower;

[0016] 6) After separation in an extractant recovery tower, the top vapor is condensed to obtain an acetic acid phase containing ethyl acetate, a small amount of vinyl acetate, a small amount of water and a small amount of ethyl acetate in a reflux tank, and a part of the acetic acid phase is refluxed to the extractant recovery tower in the reflux tank, and the other part enters the acetic acid recovery tower;

[0017] 7) The extractant recovery tower obtains heavy components such as the extractant, ethylene glycol diacetate and a small amount of acetic acid, and the bottom liquid enters the separator;

[0018] 8) The bottom liquid is separated into two streams through a separator: one stream is an extractant containing a small amount of acetic acid, and the other stream is heavy components such as ethylene glycol diacetate;

[0019] 9) The extractant containing a small amount of acetic acid in step 8) is introduced into a mixer, and heavy components such as ethylene glycol diacetate are sent out of the boundary area for impurity removal;

[0020] 10) In the mixer of step 9), a small amount of extractant is added and circulated back to the extraction tower together with the extractant in step 9).

[0021] Furthermore, the crude product vinyl acetate contains, based on 100% by mass, 20-45% by mass of vinyl acetate, 6-20% by mass of water, 0.2-2.0% by mass of acetaldehyde, 0.02-1.2% by mass of ethyl acetate, 0.02-0.5% by mass of methyl acetate, 0.02-1.2% by mass of ethylene glycol diacetate and 30-73% by mass of acetic acid.

[0022] Furthermore, the mass flow ratio of the extractant to the crude product vinyl acetate is 1:600 ​​to 1:4 (specifically 1:4, 1:50, 1:100, 1:150, 1:200, 1:250, 1:300, 1:350, 1:400, 1:450, 1:500, 1:550, 1:600, etc.).

[0023] Furthermore, the top pressure of the extraction tower is normal pressure, the top temperature is 55-70°C (specifically 55°C, 60°C, 65°C, 70°C, etc.), the bottom temperature is 105-120°C (specifically 105°C, 110°C, 115°C, 120°C, etc.), and the number of plates is 40-60 (specifically 40, 45, 50, 55, 60, etc.).

[0024] The feeding position of the crude product vinyl acetate is within the range of the 19th to 36th tower plates (specifically, the 19th, 20th, 21st, 22nd, 23rd, 24th, 25th, 26th, 27th, 28th, 29th, 30th, 31st, 32nd, 33rd, 34th, 35th, 36th, etc.).

[0025] The extractant is introduced onto the 5th to 18th layers (specifically, the 5th, 6th, 7th, 8th, 9th, 10th, 11th, 12th, 13th, 14th, 15th, 16th, 17th, 18th, etc.) tower plates above the crude product vinyl acetate feed plate.

[0026] The mass ratio of the supplemented extractant to the extractant recovered from the extractant recovery tower is 0.2-5% (specifically 0.2%, 1%, 2%, 3%, 4%, 5%, etc.).

[0027] The extractant is introduced in liquid form.

[0028] The acetic acid phase obtained from the bottom of the extraction tower enters the extractant recovery tower from the 5th to 25th (specifically, the 5th, 6th, 7th, 8th, 9th, 10th, 11th, 12th, 13th, 14th, 15th, 16th, 17th, 18th, 19th, 20th, 21st, 22nd, 23rd, 24th, 25th, etc.) tray of the extractant recovery tower.

[0029] The top pressure of the extractant recovery tower is normal pressure, the top temperature is 100-130°C (specifically 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, etc.), the bottom temperature is 140-180°C (specifically 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, etc.), and the number of plates is 40-50 (specifically 40, 42, 44, 46, 48, 50, etc.).

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) In the present method, one or more of furfural, n-butyl acetate, carbon tetrachloride and chloroform are used as extractants to change the relative volatility between vinyl acetate and ethyl acetate. The content of ethyl acetate in the discharged vinyl acetate stream is less than 70 ppm.

[0032] (2) Under the same vinyl acetate output, the present invention significantly reduces the content of ethyl acetate in the vinyl acetate stream compared with traditional distillation, improves separation efficiency and reduces energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a schematic flow diagram of a method for removing ethyl acetate from vinyl acetate by extractive distillation.

[0034] Among them: 101-extraction tower, 102-extraction agent recovery tower, 103-separator, 104-mixer, 105-phase separator, 106-extraction tower condenser, 107-extraction tower reboiler, 108-reflux tank, 109-extraction agent recovery tower condenser, 110-extraction agent recovery tower reboiler. DETAILED DESCRIPTION

[0035] A method for removing ethyl acetate from vinyl acetate by extractive distillation, comprising: Figure 1 The process shown is implemented as follows:

[0036] First, a crude product vinyl acetate stream containing water, acetic acid, acetaldehyde, methyl acetate, ethyl acetate and ethylene glycol diacetate and an extractant from a mixer 104 enter an extraction tower 101, and the feed position of the extractant is 5 to 18 trays higher than the feed position of the crude product vinyl acetate;

[0037] After extraction and distillation separation, a mixture of vinyl acetate, water, acetaldehyde, a small amount of methyl acetate and a small amount of ethyl acetate is extracted from the top of the extraction tower 101 and then enters the phase separator 105;

[0038] After phase separation, a water phase containing a small amount of vinyl acetate and a small amount of acetaldehyde is obtained in the lower layer, and a vinyl acetate phase containing a small amount of water, a small amount of acetaldehyde, a small amount of methyl acetate and a small amount of ethyl acetate is obtained in the upper layer. The water phase enters the wastewater tower, and a part of the vinyl acetate phase is refluxed to the extraction tower 101, and the other part enters the vinyl acetate refining tower for purification to obtain a high-purity vinyl acetate product;

[0039] Acetic acid, water, ethyl acetate, ethylene glycol diacetate, extractant and a small amount of vinyl acetate are withdrawn from the bottom of extraction tower 101;

[0040] The bottom liquid of the extraction tower 101 enters the extractant recovery tower 102, and the feeding position of the bottom liquid is within the range of the 5th to 25th trays;

[0041] After separation in the extractant recovery tower 102, a mixed liquid containing acetic acid, ethyl acetate, a small amount of vinyl acetate and a small amount of water is extracted from the top of the tower. Part of the mixed liquid is refluxed to the extractant recovery tower 102 in the reflux tank 108, and the other part enters the acetic acid recovery tower. The extractant, ethylene glycol diacetate and a small amount of acetic acid are extracted from the bottom of the tower.

[0042] The bottom liquid of the extractant recovery tower 102 enters the separator 103, and the extractant containing a small amount of acetic acid is extracted from the upper part of the separator 103, and ethylene glycol diacetate is extracted from the lower part;

[0043] Finally, the extractant containing a small amount of acetic acid and a small amount of additional extractant enter the mixer 104 and are mixed and then passed into the extraction tower 101 .

[0044] The extraction tower 101 is provided with an extractant feed plate and a crude product vinyl acetate feed plate;

[0045] The gas phase at the top of the extraction tower 101 is condensed by the condenser 106, and the condensate enters the phase separator 105;

[0046] The extraction tower 101 is provided with a reboiler 107 in the bottom of the tower, and the liquid outlet of the bottom of the tower is connected to the feed inlet of the extractant recovery tower 102;

[0047] The gas phase at the top of the extractant recovery tower 102 is condensed by the condenser 109, and the condensate enters the reflux tank 108;

[0048] The extractant recovery tower 102 has a bottom with a reboiler 110, and the bottom liquid outlet is connected to the feed port of the separator 103;

[0049] The upper extraction port of the separator 103 is connected to the mixer 104;

[0050] The outlet of the mixer 104 is connected to the extractant feed port of the extraction tower 101;

[0051] The ratio of the feed mass flow rate of the extractant to the feed mass flow rate of the crude product vinyl acetate is 1:600 ​​to 1:4;

[0052] The top pressure of the extraction tower 101 is normal pressure, the top temperature is 55-70° C., the bottom temperature is 105-120° C., and the number of plates is 40-60;

[0053] The feed position of the crude product vinyl acetate is within the range of the 19th to 36th trays;

[0054] The top pressure of the extractant recovery tower 102 is normal pressure, the top temperature is 100-130° C., the bottom temperature is 140-180° C., and the number of plates is 40-50;

[0055] The feeding position of the bottom liquid of the extraction tower 101 is within the range of the 5th to 25th trays;

[0056] The mass ratio of the supplemented extractant to the extractant recovered from the extractant recovery tower 102 is 0.2-5%.

[0057] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0058] Any feature disclosed in this specification (including claims and abstract), unless otherwise stated, may be replaced by other equivalent or alternative features having similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0059] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0060] Embodiment 1:

[0061] A method for removing ethyl acetate from vinyl acetate by extractive distillation, the steps of which are:

[0062] A crude product vinyl acetate stream containing water, acetic acid, acetaldehyde, methyl acetate, ethyl acetate and ethylene glycol diacetate enters the extraction tower 101 from the bottom, with a feed flow rate of 46300 kg / h, wherein the content of vinyl acetate is 30 wt%, and the content of ethyl acetate is 0.04 wt%.

[0063] The extraction agent furfural enters the extraction tower 101 from above the crude product vinyl acetate stream, the feed flow rate is 8260 kg / h, the top pressure of the extraction tower 101 is normal pressure, the bottom temperature is 64.6°C, and the bottom temperature is 113.2°C.

[0064] After extractive distillation separation, the content of ethyl acetate in the vinyl acetate stream produced by the top phase separator 105 is less than 70 ppm, and the recovery rate of vinyl acetate in the top vinyl acetate stream is 99.86 wt%.

[0065] The bottom liquid of the extraction tower 101 enters the extractant recovery tower (102) from the top, and after distillation separation, a mixture of extractant, ethylene glycol diacetate and acetic acid is produced from the bottom of the tower, with a mass flow rate of 8220 kg / h, wherein the content of the extractant is 99.70 wt%.

[0066] The top pressure of the extractant recovery tower 102 is normal pressure, the top temperature is 111.5° C., and the bottom temperature is 161.4° C.

[0067] The mixture extracted from the bottom of the extractant recovery tower 102 enters the separator (103), and 8205 kg / h of the extractant and acetic acid mixture is extracted from the upper part of the separator, wherein the content of the extractant is 99.99 wt%.

[0068] The mixture withdrawn from the upper part of the separator enters the mixer 104, and the extractant is added to the mixer 104. The mass flow ratio of the added extractant to the mixture withdrawn from the upper part of the separator is 0.8%.

[0069] If conventional distillation is used to achieve the same vinyl acetate production as that of the present invention, the ethyl acetate content in the extracted vinyl acetate stream is much higher than the ethyl acetate content of the present invention, and the total energy consumption of conventional distillation is much greater than that of the present invention.

[0070] Embodiment 2:

[0071] A crude product vinyl acetate stream containing water, acetic acid, acetaldehyde, methyl acetate, ethyl acetate and ethylene glycol diacetate enters the extraction tower 101 from the bottom, with a feed rate of 39900 kg / h, wherein the content of vinyl acetate is 34 wt%, and the content of ethyl acetate is 0.22 wt%.

[0072] The extractant n-butyl acetate enters the extraction tower 101 from above the crude product vinyl acetate stream, the feed rate is 1077 kg / h, the top pressure of the extraction tower 101 is atmospheric pressure, the bottom temperature is 64.2°C, and the bottom temperature is 111.5°C.

[0073] After extractive distillation separation, the content of ethyl acetate in the vinyl acetate stream produced by the top phase separator 105 is less than 70 ppm, and the recovery rate of vinyl acetate in the top vinyl acetate stream is 99.72 wt%.

[0074] The bottom liquid of the extraction tower 101 enters the extractant recovery tower (102) from the middle, and after distillation separation, a mixture of extractant, ethylene glycol diacetate and acetic acid is produced from the bottom of the tower, with a mass flow rate of 1110 kg / h, wherein the content of the extractant is 97.70 wt%.

[0075] The top pressure of the extractant recovery tower 102 is normal pressure, the top temperature is 111.9° C., and the bottom temperature is 129.2° C.

[0076] The mixture extracted from the bottom of the extractant recovery tower 102 enters the separator (103), and 1085 kg / h of the extractant and acetic acid mixture is extracted from the upper part of the separator, wherein the content of the extractant is 99.2 wt%.

[0077] The mixture drawn from the upper part of the separator enters the mixer 104, and the extractant is added to the mixer 104, and the mass flow ratio of the added extractant to the mixture drawn from the upper part of the separator is 0.3%.

[0078] Embodiment 3:

[0079] A crude product vinyl acetate stream containing water, acetic acid, acetaldehyde, methyl acetate, ethyl acetate and ethylene glycol diacetate enters the extraction tower 101 from the bottom, with a feed flow rate of 46300 kg / h, wherein the content of vinyl acetate is 30 wt%, and the content of ethyl acetate is 0.04 wt%.

[0080] The extractant carbon tetrachloride enters the extraction tower 101 from above the crude product vinyl acetate stream, the feed flow rate is 1230 kg / h, the top pressure of the extraction tower 101 is atmospheric pressure, the bottom temperature is 64.6°C, and the bottom temperature is 111.5°C.

[0081] After extractive distillation separation, the content of ethyl acetate in the vinyl acetate stream produced by the top phase separator 105 is less than 70 ppm, and the recovery rate of vinyl acetate in the top vinyl acetate stream is 99.78 wt%.

[0082] The bottom liquid of the extraction tower 101 enters the extractant recovery tower (102) from the top, and after distillation separation, a mixture of extractant, ethylene glycol diacetate and acetic acid is produced from the bottom of the tower, with a mass flow rate of 1410 kg / h, wherein the content of the extractant is 99.40 wt%.

[0083] The top pressure of the extractant recovery tower 102 is normal pressure, the top temperature is 110.8°C, and the bottom temperature is 155.2°C.

[0084] The mixture extracted from the bottom of the extractant recovery tower 102 enters the separator (103), and 1241 kg / h of the extractant and acetic acid mixture is extracted from the upper part of the separator, wherein the content of the extractant is 99.11 wt%.

[0085] The mixture withdrawn from the upper part of the separator enters the mixer 104, and the extractant is added to the mixer 104, and the mass flow ratio of the added extractant to the mixture withdrawn from the upper part of the separator is 0.5%.

[0086] Embodiment 4:

[0087] The method is the same as that of Example 1, but the extractant is changed to cyclohexane. After separation, the content of ethyl acetate in the vinyl acetate stream produced by the top phase separator 105 is 108 ppm, which is much higher than 70 ppm, and the recovery rate of vinyl acetate in the vinyl acetate phase is only 58 wt%.

[0088] Embodiment 5:

[0089] The method is the same as that of Example 1, but the extractant is changed to n-heptane. After separation, the content of ethyl acetate in the vinyl acetate stream produced by the top phase separator 105 is 518 ppm, which is much higher than 70 ppm, and the recovery rate of vinyl acetate in the vinyl acetate phase is only 84 wt%.

[0090] Embodiment 6:

[0091] The method is the same as that of Example 1, but the extractant is changed to butanone. After separation, the content of ethyl acetate in the vinyl acetate stream produced by the top phase separator 105 is less than 70 ppm, but the recovery rate of vinyl acetate in the vinyl acetate phase is only 89 wt%.

[0092] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

[0093] This background section is provided to generally present the context of the invention, and the work of the presently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither explicitly nor implicitly admitted to be prior art to the present invention.

Claims

1. A method for removing ethyl acetate from vinyl acetate by extractive distillation, characterized in that: The following steps are involved: 1) introducing crude vinyl acetate into an extraction tower (101), using an extractant to introduce the crude vinyl acetate into the extraction tower (101) from above a feed plate; 2) After extraction and distillation separation, the vapor at the top of the extraction tower (101) is condensed to obtain a mixture of vinyl acetate, water, acetaldehyde, a small amount of methyl acetate and a small amount of ethyl acetate, and the mixture enters a phase separator (105); a water phase containing a small amount of vinyl acetate and a small amount of acetaldehyde is obtained at the lower layer of the phase separator (105), and an organic phase containing vinyl acetate, water, acetaldehyde, methyl acetate and a small amount of ethyl acetate is obtained at the upper layer; 3) a portion of the organic phase in step (2) is refluxed into the extraction tower (101), another portion enters the vinyl acetate refining tower, and after purification, a high-purity vinyl acetate product is obtained, and the aqueous phase enters the wastewater tower; 4) obtaining an acetic acid phase containing a small amount of vinyl acetate, water, ethyl acetate, an extractant, and heavy components such as ethylene glycol diacetate in the bottom of the extraction tower (101); 5) the acetic acid phase in step 4) enters the extractant recovery tower (102); 6) After separation in the extractant recovery tower (102), the top vapor is condensed to obtain an acetic acid phase containing ethyl acetate, a small amount of vinyl acetate, a small amount of water and a small amount of ethyl acetate, and a portion of the acetic acid phase is refluxed to the extractant recovery tower (102) in the reflux tank (108), and the other portion enters the acetic acid recovery tower; 7) The extractant recovery tower (102) obtains the extractant, a small amount of acetic acid, and heavy components such as ethylene glycol diacetate in the bottom of the tower, and the bottom liquid enters the separator (103); 8) The bottom liquid is separated into two streams through a separator (103): one stream is an extractant containing a small amount of acetic acid, and the other stream is a heavy component of ethylene glycol diacetate; 9) The extractant containing a small amount of acetic acid in step 8) is introduced into a mixer (104), and the heavy components are sent out of the boundary area for impurity removal; 10) In the mixer (104) of step 9), a small amount of extractant is added and circulated back to the extraction tower (101) together with the extractant in step 9).

2. The method according to claim 1, characterized in that: The crude product vinyl acetate contains 20%-45% by mass of vinyl acetate, 6-20% by mass of water, 0.02-2.0% by mass of acetaldehyde, 0.02-1.2% by mass of ethyl acetate, 0.02-0.5% by mass of methyl acetate, 0.02-1.2% by mass of ethylene glycol diacetate and 30-73% by mass of acetic acid.

3. The method according to claim 1, characterized in that: The extractant is any one of furfural, n-butyl acetate, carbon tetrachloride and chloroform or a mixture of several of them.

4. The method according to claim 1, characterized in that: The mass flow ratio of the extractant to the crude product vinyl acetate in step 1) is 1:600 ​​to 1:

4.

5. The method according to claim 1, characterized in that: In the step 2), the top pressure of the extraction tower (101) is normal pressure, the top temperature is 55-70° C., the bottom temperature is 105-120° C., and the number of plates is 40-60.

6. The method according to claim 1, characterized in that: In the step 2), the feeding position of the crude product vinyl acetate is within the range of the 19th to 36th tower plates.

7. The method according to claim 1, characterized in that: The extractant is introduced onto the 5th to 18th tray above the crude vinyl acetate feed tray.

8. The method according to claim 1, characterized in that: The mass ratio of the extractant supplemented in step 10) to the extractant recovered from the extractant recovery tower (102) is 0.2-5%.

9. The method according to claim 1, characterized in that: In the step 5), the feeding position of the acetic acid phase of the extractant recovery tower (102) is within the range of the 5th to 25th tower plates.

10. The method according to claim 1, characterized in that: In the step 7), the top pressure of the extractant recovery tower (102) is atmospheric pressure, the top temperature is 100-130° C., the bottom temperature is 140-180° C., and the number of plates is 40-50.

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