Process and system for preparing vinyl acetate by using ethylene method

Abstract

The invention belongs to the field of chemical reaction and separation, and particularly relates to a process system for preparing vinyl acetate by an ethylene gas phase method. The system comprises a vinyl acetate synthesis system, a pre-separation system, a CO2 absorption / desorption system and a rectification system, and by optimizing a gas-liquid separation treatment mode of materials after reaction, the feeding positions of a liquid-phase product and a gas-phase product washing liquid at an outlet of a reactor in a rectification tower are improved; and a specific extraction agent is added to change the relative volatility of the product vinyl acetate and the key impurity ethyl acetate, so that the content of impurities such as ethyl acetate in the vinyl acetate product is greatly reduced, the product quality is improved, and the energy consumption of a separation system is reduced.

Description

Technical Field

[0001] The invention belongs to the field of chemical reaction and separation, and specifically relates to a process and system for preparing vinyl acetate by an ethylene gas phase process. Background Art

[0002] Vinyl acetate (VAM) is an important chemical product with a wide range of uses, mainly used in the production of polyvinyl acetate, polyvinyl alcohol, copolymer emulsions and copolymer resins. As an upstream product of ethylene-vinyl acetate (EVA), with the rapid increase in demand for EVA due to the development of the photovoltaic industry, the application areas and market demand of vinyl acetate are also expanding. At present, there are two main production process routes for vinyl acetate: the ethylene method and the acetylene method. Among them, the ethylene method is more competitive due to its large production capacity, high product quality, low energy consumption and low pollution.

[0003] At present, the standard for industrial vinyl acetate does not require the content of ethyl acetate, and vinyl acetate products contain a certain amount of ethyl acetate that is difficult to remove. High-end application fields such as EVA have high requirements for the quality of vinyl acetate products, especially the impurities in vinyl acetate (mainly methyl acetate and ethyl acetate). However, due to the limitations of catalysts and reaction kinetics, a certain amount of methyl acetate and ethyl acetate by-products will inevitably be generated in ethylene-based vinyl acetate products. Ethyl acetate and methyl acetate not only affect the quality of the product, but also reduce the activity of vinyl acetate in subsequent polymerization processes and can easily cause blockages. These by-products, especially ethyl acetate, have similar physical and chemical properties to the product vinyl acetate, making separation difficult. At present, most ethylene-based vinyl acetate plants mainly achieve the purpose of reducing the methyl acetate and ethyl acetate contents in vinyl acetate products by increasing the number of plates and reflux ratio in the distillation system. However, the ethyl acetate content in the product is still relatively high, and the stream that discharges ethyl acetate impurities contains a large amount of vinyl acetate, resulting in low product yield and high energy consumption.

[0004] Patent ZL 201210385948.4 discloses a method for producing vinyl acetate, and the invention relates to a method for producing vinyl acetate. Patent ZL 202011125426.1 discloses a process and device for producing vinyl acetate, and the invention relates to a process and device for producing vinyl acetate, and in particular, to a process and device for synthesizing vinyl acetate by ethylene gas phase method. Patent ZL202011127390.0 discloses a method for producing vinyl acetate, and the invention relates to a method for producing vinyl acetate that improves product yield, reduces waste discharge, and reduces material and energy consumption. Patent ZL202211312477.4 discloses a system and method for removing ethyl acetate in the process of producing vinyl acetate. The ethyl acetate content in the produced vinyl acetate can be made ≤250 mg / kg by extracting a stream of material from the side line of the distillation tower and feeding it into the deethyl acetate tower, and the top gas phase of the deethyl acetate tower is condensed in the deethyl acetate tower condenser and then enters the deethyl acetate tower distillation tank.

[0005] The above methods have low removal efficiency of ethyl acetate, the ethyl acetate content in the product is still relatively high, and the separation energy consumption is high. Summary of the invention

[0006] The purpose of the present invention is to solve at least one of the problems existing in the prior art and to provide a process system for producing vinyl acetate by the ethylene process, which reduces energy consumption, improves product quality and reduces product loss by optimizing the reaction and separation processes and integrating the system.

[0007] An ethylene-based vinyl acetate process system optimizes the gas-liquid separation treatment method of materials after the reaction, improves the feeding position of the liquid product at the reactor outlet and the gas product washing liquid in the distillation tower, and adds a specific extractant to change the relative volatility of the product vinyl acetate and the key impurity ethyl acetate, thereby significantly reducing the ethyl acetate content in the vinyl acetate product and reducing the energy consumption of the separation system.

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

[0009] An ethylene-based vinyl acetate process system, comprising: a vinyl acetate synthesis system, a pre-separation system, a CO2 absorption / desorption system, and a distillation system;

[0010] (1) Vinyl acetate synthesis system

[0011] After the fresh ethylene and the circulating gas are uniformly mixed in the mixer, they are gasified together with the fresh acetic acid and the circulating acetic acid in the acetic acid gasifier to obtain a gasified acetic acid / ethylene mixed raw material gas;

[0012] Fresh O2 and acetic acid / ethylene mixed raw gas are evenly mixed in a mixer to obtain a mixed reaction raw gas; the mixed reaction raw gas and the gas from the outlet of the vinyl acetate synthesis reactor are heated by a heat exchanger and further heated to the reaction temperature by a heater before entering the vinyl acetate synthesis reactor;

[0013] The vinyl acetate synthesis reactor adopts a tube-type fixed bed reactor, and the tubes are filled with Pd-Au-potassium acetate / SiO2 catalyst. The mixed reaction raw gas reacts under the action of the catalyst in the vinyl acetate synthesis reactor to obtain vinyl acetate and by-products such as CO2, H2O, acetaldehyde, methyl acetate, ethyl acetate, ethylene glycol diacetate, etc.

[0014] (2) Pre-separation system

[0015] Vinyl acetate, by-products, and unreacted C2H4, acetic acid, O2, etc. in the outlet gas of the vinyl acetate synthesis reactor are heated by a heat exchanger to mix the reaction raw gas to utilize its heat, and then the cold circulating gas is heated by a heat exchanger to further utilize its heat, and then enters the gas-liquid separator after cooling by a cooler;

[0016] The gas phase obtained at the top of the gas-liquid separator enters the bottom of the pickling / water washing tower, and the crude acetic acid solution from the bottom of the distillation tower is sprayed from the upper end of the pickling / water washing tower to wash away the acetic acid, vinyl acetate and other organic substances entrained in the gas, and deionized water is sprayed from above the acetic acid addition position of the pickling / water washing tower to wash away the acetic acid and other organic substances entrained and sprayed in the gas. The liquid is transported from the bottom of the pickling / water washing tower to the stirring tank, and the gas is transported from the top of the pickling / water washing tower to the CO2 absorption tower;

[0017] The liquid phase obtained at the bottom of the gas-liquid separator enters the stripping tower, and the gas obtained at the top of the stripping tower is separated into gas and liquid in the gas-liquid separator, wherein the gas enters the acid washing / water washing tower, and the liquid is circulated to the stripping tower;

[0018] The liquid phase at the bottom of the stripping tower enters the first distillation tower;

[0019] (3)CO2 absorption / desorption system

[0020] The gas from the acid / water washing tower enters the bottom of the CO2 absorption tower, and the absorbent is added from the top of the CO2 absorption tower for countercurrent absorption. The absorbed gas is pressurized by the compressor, preheated in the heat exchanger, and further recycled as a reaction raw material;

[0021] The absorbed rich liquid after absorbing CO2 flows out from the bottom of the tower and is preheated in the heat exchanger with the CO2 hot flow at the top of the CO2 desorption tower, and then enters the CO2 desorption tower after further heating in the heater. The desorbed CO2 gas flows out from the top of the CO2 desorption tower, heats the bottom solution of the CO2 absorption tower in the heat exchanger, and is further cooled in the cooler, dehydrated in the gas-liquid separator, and further purified and refined in the membrane separator to obtain the CO2 by-product. The absorbent solution at the bottom of the CO2 desorption tower is recycled after adding part of the absorbent in the absorbent stirring tank.

[0022] (4) Distillation system

[0023] After the reaction, the liquid phase is sent from the bottom of the stripping tower to the first distillation tower, the solution at the bottom of the pickling / water washing tower is evenly mixed with the extractant (b) in the extractant stirring tank, and sent to the first distillation tower, a small amount of non-condensable gases such as C2H4 and CO2 dissolved in the feed of the first distillation tower are sent to the pickling / water washing tower after cooling from the top of the tower, and the condensable components at the top of the tower are mainly acetaldehyde, methyl acetate, vinyl acetate, ethyl acetate and water, which are phase-separated in a phase separator, wherein the aqueous phase is sent to a wastewater tower, a part of the organic phase is refluxed to the first distillation tower, and the remaining part of the organic phase is sent to a light component removal tower, and the bottom of the tower is mainly crude acetic acid containing a small amount of water and ethyl acetate, a part of which is returned to the first distillation tower after being heated in a reboiler, a part of which enters an acetic acid refining tower, and a part of which is sent to the pickling / water washing tower as a pickling agent;

[0024] The acetic acid tower top entering the acetic acid refining tower separates light component impurities such as vinyl acetate, ethyl acetate, and H2O. After cooling and phase separation, the water phase is sent to the wastewater tower to further recover the organic matter, and the oil phase is sent to the ethyl acetate tower; the tower bottom obtains high-purity acetic acid containing trace amounts of high-boiling impurities such as ethylene glycol diacetate, which is sent to the acetic acid gasifier for recycling as a reaction raw material, and the high-boiling impurities such as ethylene glycol diacetate are regularly discharged from the bottom of the acetic acid gasifier;

[0025] The organic phase sent to the ethyl acetate tower is sent to the first distillation tower to recover the light components such as vinyl acetate at the top of the tower, and the water phase at the top of the tower is sent to the wastewater tower to further recover the organic matter therein, and the high-concentration ethyl acetate waste liquid is discharged at the bottom of the tower;

[0026] The organic matter sent to the light component removal tower obtains acetaldehyde, methyl acetate, a small amount of vinyl acetate and other light component organics and water entrained in the azeotropic composition at the top of the tower, and a high-purity acetaldehyde and methyl acetate mixture is obtained at the top of the aldehyde-removing tower. The bottom of the tower is mainly methyl acetate, vinyl acetate, etc., which are returned to the light component removal tower for further refining; the bottom of the light component removal tower obtains relatively high-purity vinyl acetate, and the bottom liquid phase is further refined in the vinyl acetate refining tower to obtain high-purity vinyl acetate at the top of the tower, and the heavy component impurity ethyl acetate and a small amount of vinyl acetate are obtained in the bottom of the tower, which are sent to the first distillation tower to further recover the vinyl acetate therein.

[0027] As a preferred embodiment, the vinyl acetate synthesis reactor is a tube-in-tube fixed bed reactor, and pressurized water is placed between the tubes of the tube-in-tube fixed bed reactor. The pressurized water is heated and vaporized in the reactor to remove the reaction heat and generate steam. The reaction temperature of the vinyl acetate synthesis reactor is 120-200°C, preferably 140-180°C, and the reaction temperature of the vinyl acetate synthesis reactor increases with the attenuation of the catalyst performance to ensure a stable vinyl acetate yield. The reaction pressure is 0.40-1.20MPa, preferably 0.70-0.80MPa, and the reaction space velocity is 1500-6000h -1 , preferably 2000-5000h -1 The composition of the reaction gas at the inlet of the vinyl acetate synthesis reactor (in terms of molar ratio) is C2H4:CH3COOH:O2:H2O:CO2=60-75:12-18:4-6:2-5:6-9;

[0028] In the above technical scheme, the material entering the reactor also contains a certain amount of CO2 and H2O, the main functions of which are: (1) the main product of the side reaction is CO2, and the addition of CO2 can effectively inhibit the occurrence of the side reaction; (2) although the increase in the partial pressure of water is not conducive to the main reaction, water vapor can inhibit the occurrence of coking reaction; (3) the reaction is a violent exothermic reaction, so the addition of water vapor increases the specific heat of the feed gas, which can effectively inhibit the occurrence of runaway temperature phenomenon; (4) the atmosphere contains a certain amount of CO2 and H2O, which can reduce the explosion range of ethylene and improve the safety of the device.

[0029] As a preferred embodiment, the first distillation tower has 55-75 plates, an operating pressure of 0.0-0.15 MPaG, an operating temperature of 50-150° C., and a reflux ratio of 3.0-6.0.

[0030] As a preferred embodiment, the liquid phase of the stripping tower kettle in the first distillation tower is fed from the 35th to 47th tower plates, and the liquid phase of the extractant stirring tank is fed from the 25th to 35th tower plates.

[0031] As a preferred embodiment, the first distillation tower adopts extractive distillation, and the extractant comprises an extractant (a) and an extractant (b), wherein the extractant (a) is a solution at the bottom of the acid washing / water washing tower, and the extractant (b) is dimethyl sulfoxide, N,N-dimethylformamide, ethylene glycol monobutyl ether, ethylene glycol, 3,5,5-trimethylhexanol, 2,6-dimethylheptanol, cyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, benzyl alcohol, β -phenylethanol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 2,3-butylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,5-pentanediol, 2-butene-1,4-diol, 1,6-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol, pentaerythritol, 2-methylbutyric acid, one or more of benzyl formate.

[0032] As a preferred embodiment, the ratio of the mass flow rate of the extractant (b) to the mass flow rate of the vinyl acetate product is 0.0001-0.05:1, and the extractant (b) is enriched at the bottom of the acetic acid gasifier and discharged regularly.

[0033] As a preferred embodiment, in the inlet material of the ethyl acetate tower, the mass content of ethyl acetate is ≥0.3%, and the mass content of vinyl acetate is ≤0.2%.

[0034] As a preferred embodiment, the mass content of ethyl acetate in the top of the first distillation tower is ≤100 ppm, the mass content of acetic acid in the top of the tower is ≤0.01%, and the mass content of vinyl acetate in the bottom of the tower is ≤0.1%.

[0035] As a preferred embodiment, the mass content of ethyl acetate in the vinyl acetate product is ≤80ppm.

[0036] As a preferred embodiment, the absorbent is an aqueous solution of one or more of potassium carbonate, sodium carbonate, monoethanolamine, diethanolamine, methyldiethanolamine, and diisopropanolamine.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The liquid product at the reactor outlet and the washing liquid after acid washing / water washing of the gas phase enter the distillation tower from different positions respectively, the washing liquid mainly contains high-boiling-point acetic acid and water, and the content of low-boiling-point acetaldehyde, vinyl acetate, ethyl acetate, and methyl acetate is low, and is added from the top as part of the extractant, which can effectively change the azeotropic effect between the components in the liquid product at the reactor outlet in the distillation tower, increase the relative volatility of vinyl acetate and ethyl acetate with similar composition, reduce the content of ethyl acetate at the top of the tower, improve the separation efficiency, and reduce the separation energy consumption;

[0039] (2) Since the reaction product has a complex composition and contains a variety of azeotropic compositions, the boiling point of ethyl acetate (~77°C) is slightly higher than the boiling point of vinyl acetate (~72.5°C), but the azeotropic point of ethyl acetate / water (~71°C) is slightly lower than the boiling point of vinyl acetate (~72.5°C), which makes it difficult to separate vinyl acetate from ethyl acetate. The present invention can effectively break the azeotropic composition of ethyl acetate and water by adding an extractant (b), reduce the azeotropic composition of ethyl acetate / water in the distillation section of the first distillation tower, increase the relative volatility of vinyl acetate and ethyl acetate, improve the separation efficiency, and reduce the energy consumption of the separation process by 15%-30%;

[0040] (3) By effectively separating vinyl acetate from ethyl acetate in a distillation tower, on the one hand, the content of ethyl acetate in the vinyl acetate product can be reduced to below 80 ppm, thereby reducing the risk of excessive ethyl acetate content clogging pipelines, equipment, and instruments and affecting the quality of the vinyl acetate product. On the other hand, the content of vinyl acetate in the ethyl acetate waste liquid can be greatly reduced, the separation energy consumption can be reduced, and the recovery rate of the vinyl acetate product can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic flow diagram of a vinyl acetate synthesis system, a pre-separation system, and a CO2 absorption / desorption system in a process system for producing vinyl acetate from ethylene according to the present invention;

[0042] Figure 2 It is a schematic flow diagram of a distillation system in a process system for producing vinyl acetate from ethylene according to the present invention;

[0043] The reference numerals are: 101-mixer, 102-acetic acid gasifier, 103-oxygen mixer, 104-primary heat exchanger, 105-heater 1, 106-vinyl acetate synthesis reactor, 107-secondary heat exchanger, 108-cooler 1, 109-gas-liquid separator 1, 110-stripping tower, 111-gas-liquid separator 2, 112-acid washing / water washing tower, 113-CO2 absorption tower, 114-circulating gas compressor, 115-heat exchanger, 116- 6-heater 2, 117-CO2 desorption tower, 118-absorbent stirring tank, 119-cooler 2, 120-gas-liquid separator 3, 121-membrane separator, 122-extractant stirring tank, 202-phase separator 1, 203-acetic acid refining tower, 204-phase separator 2, 205-light component removal tower, 206-phase separator 3, 207-aldehyde and ester removal tower, 208-vinyl acetate refining tower, 209-ethyl acetate tower, 210-phase separator 4, 211-wastewater tower. DETAILED DESCRIPTION

[0044] 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.

[0045] 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.

[0046] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0047] In the following examples, "%" refers to molar percentage unless otherwise specified.

[0048] The ethylene-based vinyl acetate process system proposed in the present invention mainly includes a vinyl acetate synthesis system, a pre-separation system, a CO2 absorption / desorption system, and a distillation system. The following is a description of the method and device of the present invention in conjunction with the accompanying drawings.

[0049] The present invention is achieved by Figure 1 , Figure 2 The method shown implements:

[0050] Embodiment 1:

[0051] A process system for producing vinyl acetate from ethylene, such as Figure 1 and Figure 2 As shown, it includes a mixer 101, an acetic acid gasifier 102, an oxygen mixer 103, a primary heat exchanger 104, a heater 105, a vinyl acetate synthesis reactor 106, a secondary heat exchanger 107, a cooler 108, a gas-liquid separator 109, a stripping tower 110, a gas-liquid separator 2 111, an acid washing / water washing tower 112, a CO2 absorption tower 113, a circulating gas compressor 114, a heat exchanger 115, a heater Two 116, CO2 desorption tower 117, absorbent stirring tank 118, cooler two 119, gas-liquid separator three 120, membrane separator 121, extractant stirring tank 122, phase separator one 202, acetic acid refining tower 203, phase separator two 204, light component removal tower 205, phase separator three 206, aldehyde removal tower 207, vinyl acetate refining tower 208, ethyl acetate tower 209, phase separator four 210, wastewater tower 211.

[0052] The specific process is:

[0053] After the fresh ethylene and the circulating gas are uniformly mixed in the mixer 101, they are gasified together with the fresh acetic acid and the circulating acetic acid in the acetic acid gasifier 102 to obtain a gasified acetic acid / ethylene mixed raw material gas;

[0054] Fresh O2 and acetic acid / ethylene mixed raw gas are mixed evenly in the mixer 103 to obtain mixed reaction raw gas;

[0055] The mixed reaction raw gas and the gas from the outlet of the vinyl acetate synthesis reactor 106 are heated by the heat exchanger 104, and further heated to the reaction temperature by the heater 105, and then enter the vinyl acetate synthesis reactor 106;

[0056] The vinyl acetate synthesis reactor 106 adopts a tube-in-tube fixed bed reactor, and the tubes are filled with Pd-Au-potassium acetate / SiO2 catalysts. The mixed reaction raw gas reacts under the action of the catalyst in the vinyl acetate synthesis reactor 106 to obtain vinyl acetate and by-products such as CO2, H2O, acetaldehyde, methyl acetate, ethyl acetate, ethylene glycol diacetate, etc.

[0057] The inner diameter of the tubes of the vinyl acetate synthesis reactor 106 is 32 mm and the length is 8.0 m. There is pressurized water between the tubes of the reactor. The pressurized water is heated and vaporized in the reactor to remove the reaction heat and generate steam. The steam can provide heat for the subsequent separation process. The reaction temperature of the vinyl acetate synthesis reactor 106 is 150°C, the reaction pressure is 0.80 MPa, and the reaction space velocity is 4500 h -1 The composition of the reaction gas at the inlet of the vinyl acetate synthesis reactor 106 (in terms of molar ratio) is C2H4:CH3COOH:O2:H2O:CO2=66:17:6:3:8;

[0058] The outlet gas of the vinyl acetate synthesis reactor 106 mainly contains 4.651% of vinyl acetate in molar fraction, 1.180% of by-product CO2, 0.028% of acetaldehyde, 0.006% of methyl acetate, 0.13% of ethyl acetate, 0.008% of ethylene glycol diacetate, and unreacted C2H4, acetic acid, and O2. After the mixed reaction raw gas is heated by the heat exchanger 104 to utilize its heat, the cold circulating gas is heated by the heat exchanger 107 to further utilize its heat, and then the gas is cooled to 30° C. by the cooler 108 and enters the gas-liquid separator 109;

[0059] The gas phase obtained from the top of the gas-liquid separator 109 enters the bottom of the pickling / water washing tower 112, and the crude acetic acid solution from the bottom of the distillation tower 201 is sprayed from the upper end of the pickling / water washing tower 112 to wash away the acetic acid, vinyl acetate and other organic substances entrained in the gas, and deionized water is sprayed from above the acetic acid addition position of the pickling / water washing tower 112 to wash away the acetic acid and other organic substances entrained and sprayed in the gas. The liquid is transported from the bottom of the pickling / water washing tower 112 to the stirring tank 122, and the gas is transported from the top of the pickling / water washing tower 112 to the CO2 absorption tower 113;

[0060] The liquid phase obtained at the bottom of the gas-liquid separator 109 enters the stripping tower 110, and the gas obtained at the top of the stripping tower 110 is separated into gas and liquid in the gas-liquid separator 2 111, wherein the gas enters the acid washing / water washing tower 112, and the liquid is circulated to the stripping tower 110;

[0061] The liquid phase at the bottom of the stripping tower 110 enters the first distillation tower 201;

[0062] The gas from the acid / water washing tower 112 enters the bottom of the CO2 absorption tower 113, and the absorbent of 15% ethanolamine aqueous solution is added from the top of the CO2 absorption tower 113 for countercurrent absorption. The gas after absorption treatment is pressurized by the compressor 114, preheated in the heat exchanger 107, and further recycled as a reaction raw material;

[0063] The absorbed rich liquid after absorbing CO2 flows out from the bottom of the tower and is preheated in the heat exchanger 115 with the CO2 hot flow at the top of the CO2 desorption tower 117, and is further heated in the heater 2 116 before entering the CO2 desorption tower 117.

[0064] The desorbed CO2 gas flows out from the top of the CO2 desorption tower 117, heats the bottom solution of the CO2 absorption tower 113 in the heat exchanger 115, is further cooled in the cooler 119, and is dehydrated in the gas-liquid separator 120, and is further purified and refined in the membrane separator 121 to obtain a high-purity CO2 by-product.

[0065] The absorbent solution at the bottom of the CO2 desorption tower 117 is recycled in the absorbent stirring tank 118 after being supplemented with part of the absorbent.

[0066] The liquid phase after the reaction is sent from the bottom of the stripping tower 110 to the first distillation tower 201, the solution at the bottom of the acid washing / water washing tower 112 and N,N-dimethylformamide with a mass ratio of 1:60 to the liquid phase stream after the reaction are evenly mixed in the extractant stirring tank 122, and sent to the first distillation tower 201, wherein the first distillation tower 201 has 68 trays, an operating pressure of 0.12 MPaG, a tower top operating temperature of 69.5°C, a tower bottom operating temperature of 123°C, a reflux ratio of 4.5, and the liquid phase of the bottom of the stripping tower 110 is fed from the 45th tray, and the liquid phase of the extractant stirring tank 122 is fed from the 27th tray;

[0067] A small amount of non-condensable gases such as C2H4 and CO2 dissolved in the feed of the first distillation tower 201 are sent to the pickling / water washing tower 112 after cooling from the top of the tower. The condensable components at the top of the tower are mainly acetaldehyde, methyl acetate, vinyl acetate, ethyl acetate and water. Phase separation is carried out in the first phase separator 202, wherein the aqueous phase is sent to the wastewater tower 211, a part of the organic phase is refluxed to the first distillation tower 201, and the remaining part of the organic phase is sent to the light component removal tower 205. The bottom of the tower is mainly crude acetic acid containing a small amount of water and ethyl acetate, a part of which is returned to the first distillation tower 201 after heating in the reboiler, a part enters the acetic acid refining tower 203, and a part is sent to the pickling / water washing tower 112 as a pickling agent. The molar ratio of the pickling agent to the gas entering the pickling / water washing tower 112 is 1:3.6;

[0068] The light component impurities such as vinyl acetate, ethyl acetate and H2O are separated from the top of the acetic acid tower entering the acetic acid refining tower 203. After cooling and phase separation, the aqueous phase is sent to the wastewater tower 211 to further recover the organic matter therein, and the oil phase is sent to the ethyl acetate tower 209; the high-purity acetic acid containing trace amounts of ethylene glycol diacetate and high-boiling point impurities such as N,N-dimethylformamide is obtained in the bottom of the tower, and is sent to the acetic acid gasifier 102 for recycling as a reaction raw material, and the high-boiling point impurities such as ethylene glycol diacetate and N,N-dimethylformamide are regularly discharged from the bottom of the acetic acid gasifier 102; the discharged high-boiling point impurities contain a certain amount of acetic acid, which is pumped to the high-boiling waste liquid tank for centralized treatment to recover the acetic acid and N,N-dimethylformamide therein.

[0069] The organic phase sent to the ethyl acetate tower 209 is sent to the top of the tower to recover the light components such as vinyl acetate and methyl acetate. The organic phase is sent to the first distillation tower 201 to recover the vinyl acetate therein, and the water phase at the top of the tower is sent to the wastewater tower 211 to further recover the organic matter therein, and the high-concentration ethyl acetate waste liquid is discharged at the bottom of the tower;

[0070] The organic matter sent to the light component removal tower 205 obtains acetaldehyde, methyl acetate, a small amount of vinyl acetate and other light component organics and water entrained in the azeotropic composition at the top of the tower. After most of the water is removed by the phase separator three 206, the remaining organic phase obtains a high-purity acetaldehyde and methyl acetate mixture at the top of the aldehyde removal tower 207. The bottom of the tower mainly contains methyl acetate, vinyl acetate, etc., which are returned to the light component removal tower 205 for further refinement; the bottom of the light component removal tower 205 obtains relatively high-purity vinyl acetate, and the bottom liquid phase is further refined by the vinyl acetate refining tower 208, and a vinyl acetate product with a mass purity of 99.97% is obtained at the top of the tower. The ethyl acetate content in the vinyl acetate is 65ppm. The heavy component impurity ethyl acetate and a small amount of vinyl acetate are obtained in the bottom of the tower, which are sent to the distillation tower 1 201 for further recovery of the vinyl acetate.

[0071] The energy consumption of the distillation process in this Example 1 is 216 kg of standard coal per ton of vinyl acetate product.

[0072] Embodiment 2:

[0073] A process system for producing vinyl acetate from ethylene, such as Figure 1 and Figure 2 As shown, it includes a mixer 101, an acetic acid gasifier 102, an oxygen mixer 103, a primary heat exchanger 104, a heater 105, a vinyl acetate synthesis reactor 106, a secondary heat exchanger 107, a cooler 108, a gas-liquid separator 109, a stripping tower 110, a gas-liquid separator 2 111, an acid washing / water washing tower 112, a CO2 absorption tower 113, a circulating gas compressor 114, a heat exchanger 115, a heater Two 116, CO2 desorption tower 117, absorbent stirring tank 118, cooler two 119, gas-liquid separator three 120, membrane separator 121, extractant stirring tank 122, phase separator one 202, acetic acid refining tower 203, phase separator two 204, light component removal tower 205, phase separator three 206, aldehyde removal tower 207, vinyl acetate refining tower 208, ethyl acetate tower 209, phase separator four 210, wastewater tower 211.

[0074] The specific process is:

[0075] After the fresh ethylene and the circulating gas are uniformly mixed in the mixer 101, they are gasified together with the fresh acetic acid and the circulating acetic acid in the acetic acid gasifier 102 to obtain a gasified acetic acid / ethylene mixed raw material gas;

[0076] Fresh O2 and acetic acid / ethylene mixed raw gas are mixed evenly in the mixer 103 to obtain mixed reaction raw gas;

[0077] The mixed reaction raw gas and the gas from the outlet of the vinyl acetate synthesis reactor 106 are heated by the heat exchanger 104, and further heated to the reaction temperature by the heater 105, and then enter the vinyl acetate synthesis reactor 106;

[0078] The vinyl acetate synthesis reactor 106 adopts a tube-in-tube fixed bed reactor, and the tubes are filled with Pd-Au-potassium acetate / SiO2 catalysts. The mixed reaction raw gas reacts under the action of the catalyst in the vinyl acetate synthesis reactor 106 to obtain vinyl acetate and by-products such as CO2, H2O, acetaldehyde, methyl acetate, ethyl acetate, ethylene glycol diacetate, etc.

[0079] The inner diameter of the tubes of the vinyl acetate synthesis reactor 106 is 32 mm and the length is 8.0 m. There is pressurized water between the tubes of the reactor. The pressurized water is heated and vaporized in the reactor to remove the reaction heat and generate steam. The steam can provide heat for the subsequent separation process. The reaction temperature of the vinyl acetate synthesis reactor 106 is 150°C, the reaction pressure is 0.80 MPa, and the reaction space velocity is 4500 h -1The composition of the reaction gas at the inlet of the vinyl acetate synthesis reactor 106 (in terms of molar ratio) is C2H4:CH3COOH:O2:H2O:CO2=66:17:6:3:8;

[0080] The outlet gas of the vinyl acetate synthesis reactor 106 mainly contains 4.651% of vinyl acetate in molar fraction, 1.180% of by-product CO2, 0.028% of acetaldehyde, 0.006% of methyl acetate, 0.005% of ethyl acetate, 0.008% of ethylene glycol diacetate, and unreacted C2H4, acetic acid, and O2. After the mixed reaction raw gas is heated by the heat exchanger 104 to utilize its heat, the cold circulating gas is heated by the heat exchanger 107 to further utilize its heat, and then the gas is cooled to 30° C. by the cooler 108 and enters the gas-liquid separator 109;

[0081] The gas phase obtained from the top of the gas-liquid separator 109 enters the bottom of the pickling / water washing tower 112, and the crude acetic acid solution from the bottom of the distillation tower 201 is sprayed from the upper end of the pickling / water washing tower 112 to wash away the acetic acid, vinyl acetate and other organic substances entrained in the gas, and deionized water is sprayed from above the acetic acid addition position of the pickling / water washing tower 112 to wash away the acetic acid and other organic substances entrained and sprayed in the gas. The liquid is transported from the bottom of the pickling / water washing tower 112 to the stirring tank 122, and the gas is transported from the top of the pickling / water washing tower 112 to the CO2 absorption tower 113;

[0082] The liquid phase obtained at the bottom of the gas-liquid separator 109 enters the stripping tower 110, and the gas obtained at the top of the stripping tower 110 is separated into gas and liquid in the gas-liquid separator 2 111, wherein the gas enters the acid washing / water washing tower 112, and the liquid is circulated to the stripping tower 110;

[0083] The liquid phase at the bottom of the stripping tower 110 enters the first distillation tower 201;

[0084] The gas from the acid / water washing tower 112 enters the bottom of the CO2 absorption tower 113, and the absorbent of 15% ethanolamine aqueous solution is added from the top of the CO2 absorption tower 113 for countercurrent absorption. The gas after absorption treatment is pressurized by the compressor 114, preheated in the heat exchanger 107, and further recycled as a reaction raw material;

[0085] The absorbed rich liquid after absorbing CO2 flows out from the bottom of the tower and is preheated in the heat exchanger 115 with the CO2 hot flow at the top of the CO2 desorption tower 117, and is further heated in the heater 2 116 before entering the CO2 desorption tower 117.

[0086] The desorbed CO2 gas flows out from the top of the CO2 desorption tower 117, heats the bottom solution of the CO2 absorption tower 113 in the heat exchanger 115, is further cooled in the cooler 119, and is dehydrated in the gas-liquid separator 120, and is further purified and refined in the membrane separator 121 to obtain a high-purity CO2 by-product.

[0087] The absorbent solution at the bottom of the CO2 desorption tower 117 is recycled in the absorbent stirring tank 118 after being supplemented with part of the absorbent.

[0088] The liquid phase after the reaction is sent from the bottom of the stripping tower 110 to the first distillation tower 201, the solution at the bottom of the acid washing / water washing tower 112 and 1,4-butanediol with a mass ratio of 1:75 to the liquid phase after the reaction are evenly mixed in the extractant stirring tank 122, and sent to the first distillation tower 201, wherein the first distillation tower 201 has 68 trays, an operating pressure of 0.12 MPaG, a tower top operating temperature of 69.5°C, a tower bottom operating temperature of 123°C, a reflux ratio of 4.5, and the liquid phase of the bottom of the stripping tower 110 is fed from the 45th tray, and the liquid phase of the extractant stirring tank 122 is fed from the 27th tray;

[0089] A small amount of non-condensable gases such as C2H4 and CO2 dissolved in the feed of the first distillation tower 201 are sent to the pickling / water washing tower 112 after cooling from the top of the tower. The condensable components at the top of the tower are mainly acetaldehyde, methyl acetate, vinyl acetate, ethyl acetate and water. Phase separation is carried out in the first phase separator 202, wherein the aqueous phase is sent to the wastewater tower 211, a part of the organic phase is refluxed to the first distillation tower 201, and the remaining part of the organic phase is sent to the light component removal tower 205. The bottom of the tower is mainly crude acetic acid containing a small amount of water and ethyl acetate, a part of which is returned to the first distillation tower 201 after heating in the reboiler, a part enters the acetic acid refining tower 203, and a part is sent to the pickling / water washing tower 112 as a pickling agent. The molar ratio of the pickling agent to the gas entering the pickling / water washing tower 112 is 1:3.6;

[0090] The acetic acid tower top entering the acetic acid refining tower 203 separates out light component impurities such as vinyl acetate, ethyl acetate, and H2O. After cooling and phase separation, the aqueous phase is sent to the wastewater tower 211 to further recover the organic matter therein, and the oil phase is sent to the ethyl acetate tower 209; the tower bottom obtains high-purity acetic acid containing trace amounts of ethylene glycol diacetate and high-boiling point impurities such as 1,4-butanediol, which is sent to the acetic acid gasifier 102 for recycling as a reaction raw material, and the high-boiling point impurities such as ethylene glycol diacetate and 1,4-butanediol are regularly discharged from the bottom of the acetic acid gasifier 102; the discharged high-boiling point impurities contain a certain amount of acetic acid, which is pumped to the high-boiling waste liquid tank for centralized treatment to recover the acetic acid and 1,4-butanediol therein.

[0091] The organic phase sent to the ethyl acetate tower 209 is sent to the top of the tower to recover the light components such as vinyl acetate and methyl acetate. The organic phase is sent to the first distillation tower 201 to recover the vinyl acetate therein, and the water phase at the top of the tower is sent to the wastewater tower 211 to further recover the organic matter therein, and the high-concentration ethyl acetate waste liquid is discharged at the bottom of the tower;

[0092] The organic matter sent to the light component removal tower 205 obtains acetaldehyde, methyl acetate, a small amount of vinyl acetate and other light component organics and water entrained in the azeotropic composition at the top of the tower. After most of the water is removed by the phase separator three 206, the remaining organic phase obtains a high-purity acetaldehyde and methyl acetate mixture at the top of the aldehyde removal tower 207. The bottom of the tower mainly contains methyl acetate, vinyl acetate, etc., which are returned to the light component removal tower 205 for further refinement; the bottom of the light component removal tower 205 obtains relatively high-purity vinyl acetate, and the bottom liquid phase is further refined by the vinyl acetate refining tower 208, and a vinyl acetate product with a mass purity of 99.96% is obtained at the top of the tower, and the ethyl acetate content in the vinyl acetate is 73ppm. The heavy component impurity ethyl acetate and a small amount of vinyl acetate are obtained in the bottom of the tower, which are sent to the distillation tower 1 201 for further recovery of the vinyl acetate.

[0093] The energy consumption of the distillation process in this Example 2 is 223 kg of standard coal per ton of vinyl acetate product.

[0094] Comparative Example 1:

[0095] After the fresh ethylene and the circulating gas are uniformly mixed in the mixer 101, they are gasified together with the fresh acetic acid and the circulating acetic acid in the acetic acid gasifier 102 to obtain a gasified acetic acid / ethylene mixed raw material gas;

[0096] Fresh O2 and acetic acid / ethylene mixed raw gas are mixed evenly in the mixer 103 to obtain mixed reaction raw gas;

[0097] The mixed reaction raw gas and the gas from the outlet of the vinyl acetate synthesis reactor 106 are heated by the heat exchanger 104, and further heated to the reaction temperature by the heater 105, and then enter the vinyl acetate synthesis reactor 106;

[0098] The vinyl acetate synthesis reactor 106 adopts a tube-in-tube fixed bed reactor, and the tubes are filled with Pd-Au-potassium acetate / SiO2 catalysts. The mixed reaction raw gas reacts under the action of the catalyst in the vinyl acetate synthesis reactor 106 to obtain vinyl acetate and by-products such as CO2, H2O, acetaldehyde, methyl acetate, ethyl acetate, ethylene glycol diacetate, etc.

[0099] The inner diameter of the tubes of the vinyl acetate synthesis reactor 106 is 32 mm and the length is 8.0 m. There is pressurized water between the tubes of the reactor. The pressurized water is heated and vaporized in the reactor to remove the reaction heat and generate steam. The steam can provide heat for the subsequent separation process. The reaction temperature of the vinyl acetate synthesis reactor 106 is 150°C, the reaction pressure is 0.80 MPa, and the reaction space velocity is 4500 h -1 The composition of the reaction gas at the inlet of the vinyl acetate synthesis reactor 106 (in terms of molar ratio) is C2H4:CH3COOH:O2:H2O:CO2=66:17:6:3:8;

[0100] The outlet gas of the vinyl acetate synthesis reactor 106 mainly contains 4.651% of vinyl acetate in molar fraction, 1.180% of by-product CO2, 0.028% of acetaldehyde, 0.006% of methyl acetate, 0.005% of ethyl acetate, 0.008% of ethylene glycol diacetate, and unreacted C2H4, acetic acid, and O2. After the mixed reaction raw gas is heated by the heat exchanger 104 to utilize its heat, the cold circulating gas is heated by the heat exchanger 107 to further utilize its heat, and then the gas is cooled to 30° C. by the cooler 108 and enters the gas-liquid separator 109;

[0101] The gas phase obtained from the top of the gas-liquid separator 109 enters the bottom of the pickling / water washing tower 112, and the crude acetic acid solution from the bottom of the distillation tower 201 is sprayed from the upper end of the pickling / water washing tower 112 to wash away the acetic acid, vinyl acetate and other organic substances entrained in the gas, and deionized water is sprayed from above the acetic acid addition position of the pickling / water washing tower 112 to wash away the acetic acid and other organic substances entrained and sprayed in the gas. The liquid is transported from the bottom of the pickling / water washing tower 112 to the stirring tank 122, and the gas is transported from the top of the pickling / water washing tower 112 to the CO2 absorption tower 113;

[0102] The liquid phase obtained at the bottom of the gas-liquid separator 109 enters the stripping tower 110, and the gas obtained at the top of the stripping tower 110 is separated into gas and liquid in the gas-liquid separator 2 111, wherein the gas enters the acid washing / water washing tower 112, and the liquid is circulated to the stripping tower 110;

[0103] The gas from the acid / water washing tower 112 enters the bottom of the CO2 absorption tower 113, and the absorbent of 15% ethanolamine aqueous solution is added from the top of the CO2 absorption tower 113 for countercurrent absorption. The gas after absorption treatment is pressurized by the compressor 114, preheated in the heat exchanger 107, and further recycled as a reaction raw material;

[0104] The absorbed rich liquid after absorbing CO2 flows out from the bottom of the tower and is preheated in the heat exchanger 115 with the CO2 hot flow at the top of the CO2 desorption tower 117, and is further heated in the heater 2 116 before entering the CO2 desorption tower 117.

[0105] The desorbed CO2 gas flows out from the top of the CO2 desorption tower 117, heats the bottom solution of the CO2 absorption tower 113 in the heat exchanger 115, is further cooled in the cooler 119, and is dehydrated in the gas-liquid separator 120, and is further purified and refined in the membrane separator 121 to obtain a high-purity CO2 by-product.

[0106] The absorbent solution at the bottom of the CO2 desorption tower 117 is recycled in the absorbent stirring tank 118 after being supplemented with part of the absorbent.

[0107] The liquid phase at the bottom of the stripping tower 110 and the solution at the bottom of the acid / water washing tower 112 are mixed and then sent to the first distillation tower 201, wherein the first distillation tower 201 has 68 trays, an operating pressure of 0.12 MPaG, a tower top operating temperature of 69.5°C, a tower bottom operating temperature of 123°C, a reflux ratio of 4.5, and the liquid phase is fed from the 45th tray;

[0108] A small amount of non-condensable gases such as C2H4 and CO2 dissolved in the feed of the first distillation tower 201 are sent to the pickling / water washing tower 112 after cooling from the top of the tower. The condensable components at the top of the tower are mainly acetaldehyde, methyl acetate, vinyl acetate, ethyl acetate and water. Phase separation is carried out in the first phase separator 202, wherein the aqueous phase is sent to the wastewater tower 211, a part of the organic phase is refluxed to the first distillation tower 201, and the remaining part of the organic phase is sent to the light component removal tower 205. The bottom of the tower is mainly crude acetic acid containing a small amount of water and ethyl acetate, a part of which is returned to the first distillation tower 201 after heating in the reboiler, a part enters the acetic acid refining tower 203, and a part is sent to the pickling / water washing tower 112 as a pickling agent. The molar ratio of the pickling agent to the gas entering the pickling / water washing tower 112 is 1:3.6;

[0109] The light component impurities such as vinyl acetate, ethyl acetate and H2O are separated from the top of the acetic acid tower entering the acetic acid refining tower 203. After cooling and phase separation, the aqueous phase is sent to the wastewater tower 211 to further recover the organic matter therein, and the oil phase is sent to the ethyl acetate tower 209; the high-purity acetic acid containing trace amounts of high-boiling point impurities such as ethylene glycol diacetate is obtained in the bottom of the tower and sent to the acetic acid gasifier 102 for recycling as a reaction raw material, and the high-boiling point impurities such as ethylene glycol diacetate are regularly discharged from the bottom of the acetic acid gasifier 102; the discharged high-boiling point impurities contain a certain amount of acetic acid, which are pumped to the high-boiling waste liquid tank for centralized treatment to recover the acetic acid therein.

[0110] The organic phase sent to the ethyl acetate tower 209 is sent to the top of the tower to recover the light components such as vinyl acetate and methyl acetate. The organic phase is sent to the first distillation tower 201 to recover the vinyl acetate therein, and the water phase at the top of the tower is sent to the wastewater tower 211 to further recover the organic matter therein, and the high-concentration ethyl acetate waste liquid is discharged at the bottom of the tower;

[0111] The organic matter sent to the light component removal tower 205 obtains acetaldehyde, methyl acetate, a small amount of vinyl acetate and other light component organics and water entrained in the azeotropic composition at the top of the tower. After most of the water is removed by the phase separator three 206, the remaining organic phase obtains a high-purity acetaldehyde and methyl acetate mixture at the top of the aldehyde removal tower 207. The bottom of the tower mainly contains methyl acetate, vinyl acetate, etc., which are returned to the light component removal tower 205 for further refinement; the bottom of the light component removal tower 205 obtains relatively high-purity vinyl acetate, and the bottom liquid phase is further refined by the vinyl acetate refining tower 208, and a vinyl acetate product with a mass purity of 99.93% is obtained at the top of the tower. The ethyl acetate content in the vinyl acetate is 328ppm. The heavy component impurity ethyl acetate and a small amount of vinyl acetate are obtained in the bottom of the tower, which are sent to the distillation tower 1 201 for further recovery of the vinyl acetate.

[0112] The energy consumption of the distillation process in this comparative example is 254 kg standard coal per ton of vinyl acetate product.

[0113] 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.

[0114] 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 process system for preparing vinyl acetate by ethylene process, comprising a vinyl acetate synthesis system, a pre-separation system, a CO2 absorption / desorption system, and a distillation system, characterized in that: (1) Vinyl acetate synthesis system After the fresh ethylene and the circulating gas are uniformly mixed in the mixer (101), they are gasified together with the fresh acetic acid and the circulating acetic acid in the acetic acid gasifier (102) to obtain a gasified acetic acid / ethylene mixed raw material gas; Fresh O2 and acetic acid / ethylene mixed raw gas are mixed evenly in a mixer (103) to obtain a mixed reaction raw gas; The mixed reaction raw gas and the gas from the outlet of the vinyl acetate synthesis reactor (106) are heated by the heat exchanger (104), and further heated to the reaction temperature by the heater 1 (105), and then enter the vinyl acetate synthesis reactor (106); The mixed reaction raw gas reacts under the action of a catalyst in a vinyl acetate synthesis reactor (106) to obtain vinyl acetate and by-products such as CO2, H2O, acetaldehyde, methyl acetate, ethyl acetate, and ethylene glycol diacetate; (2) Pre-separation system Vinyl acetate, by-products, and unreacted C2H4, acetic acid, and O2 in the outlet gas of the vinyl acetate synthesis reactor (106) are heated by the heat exchanger (104) to heat the mixed reaction raw gas to utilize its heat, and then heated by the heat exchanger (107) to further utilize its heat, and then enter the gas-liquid separator (109) after cooling by the cooler (108); The gas phase obtained from the top of the gas-liquid separator (109) enters the bottom of the pickling / water washing tower (112), and the crude acetic acid solution from the bottom of the distillation tower (201) is sprayed from the upper end of the pickling / water washing tower (112) to wash away a small amount of acetic acid, vinyl acetate and other organic matter entrained in the gas, and deionized water is sprayed from above the acetic acid addition position of the pickling / water washing tower (112) to wash away a small amount of vinyl acetate and acetic acid entrained and sprayed in the gas. The liquid is transported from the bottom of the pickling / water washing tower (112) to the stirring tank (122), and the gas is transported from the top of the pickling / water washing tower (112) to the CO2 absorption tower (113); The liquid phase obtained at the bottom of the gas-liquid separator 1 (109) enters the stripping tower (110), and the gas obtained at the top of the stripping tower (110) is separated into gas and liquid in the gas-liquid separator 2 (111), wherein the gas enters the acid washing / water washing tower (112), and the liquid is circulated to the stripping tower (110); The liquid phase at the bottom of the stripping tower (110) enters the first distillation tower (201); (3)CO2 absorption / desorption system The gas from the acid / water washing tower (112) enters the bottom of the CO2 absorption tower (113), and the absorbent is added from the top of the CO2 absorption tower (113) for countercurrent absorption. The absorbed gas is pressurized by the compressor (114), preheated in the heat exchanger (107), and further recycled as a reaction raw material; The absorbed rich liquid after absorbing CO2 flows out from the bottom of the tower and is preheated with the CO2 hot flow at the top of the CO2 desorption tower (117) in the heat exchanger (115), and is further heated in the second heater (116) before entering the CO2 desorption tower (117); the desorbed CO2 gas flows out from the top of the CO2 desorption tower (117) and heats the bottom solution of the CO2 absorption tower (113) in the heat exchanger (115), and is further cooled in the second cooler (119), and is dehydrated in the third gas-liquid separator (120), and is further purified and refined in the membrane separator (121) to obtain a CO2 by-product; the absorbent solution at the bottom of the CO2 desorption tower (117) is recycled after being supplemented with part of the absorbent in the absorbent stirring tank (118); (4) Distillation system After the reaction, the liquid phase is sent from the bottom of the stripping tower (110) to the first distillation tower (201). The solution at the bottom of the acid washing / water washing tower (112) is mixed evenly with the extractant (b) in the extractant stirring tank (122) and sent to the first distillation tower (201). A small amount of C2H4, CO2, and O2 non-condensable gases dissolved in the feed of the first distillation tower (201) are sent to the acid washing / water washing tower (112) from the top of the tower after cooling. The condensable components at the top of the tower are mainly acetaldehyde, methyl acetate, vinyl acetate, acetic acid Ethyl acetate and water are separated in a phase separator (202), wherein the aqueous phase is transported to a wastewater tower (211), a portion of the organic phase is refluxed to a distillation tower (201), and the remaining portion of the organic phase is transported to a light component removal tower (205). The bottom of the tower is mainly crude acetic acid containing a small amount of water and ethyl acetate, a portion of which is heated in a reboiler and returned to the distillation tower (201), a portion of which enters an acetic acid refining tower (203), and a portion of which is sent to an acid washing / water washing tower (112) for use as an acid washing agent; The light impurity vinyl acetate, a small amount of ethyl acetate and H2O are separated from the top of the acetic acid tower entering the acetic acid refining tower (203). After cooling and phase separation, the aqueous phase is sent to the wastewater tower (211) to further recover the organic matter therein, and the oil phase is sent to the ethyl acetate tower (209); the high-purity acetic acid containing a trace amount of high-boiling impurity ethylene glycol diacetate is obtained in the bottom of the tower and sent to the acetic acid gasifier (102) for recycling as a reaction raw material, and the ethylene glycol diacetate is regularly discharged from the bottom of the acetic acid gasifier (102); The organic phase sent to the ethyl acetate tower (209) is sent to the first distillation tower (201) to recover the light component vinyl acetate at the top of the tower, and the water phase at the top of the tower is sent to the wastewater tower (211) to further recover the organic matter therein, and the high-concentration ethyl acetate waste liquid is discharged at the bottom of the tower; The organic matter fed into the light component removal tower (205) obtains light component organic matter acetaldehyde, methyl acetate, a small amount of vinyl acetate and water entrained in the azeotropic composition at the top of the tower, and a high-purity mixture of acetaldehyde and methyl acetate is obtained at the top of the aldehyde removal tower (207). The bottom of the tower mainly contains methyl acetate and vinyl acetate, which are returned to the light component removal tower (205) for further refining; the bottom of the light component removal tower (205) obtains relatively high-purity vinyl acetate, and the bottom liquid phase is further refined by the vinyl acetate refining tower (208), and high-purity vinyl acetate is obtained at the top of the tower, and the heavy component impurity ethyl acetate and a small amount of vinyl acetate are obtained in the bottom of the tower, which are fed to the first distillation tower (201) to further recover the vinyl acetate therein.

2. The ethylene-based vinyl acetate process system according to claim 1, characterized in that: The vinyl acetate synthesis reactor (106) is a tube-in-tube fixed bed reactor, in which Pd-Au-potassium acetate / SiO2 catalyst is loaded; between the tubes of the tube-in-tube fixed bed reactor there is pressurized water, which is heated and vaporized in the reactor to remove the reaction heat and generate steam. The reaction temperature of the vinyl acetate synthesis reactor (106) is 120-200°C, the reaction pressure is 0.40-1.20MPa, and the reaction space velocity is 1500-6000h -1 The composition of the reaction gas at the inlet of the vinyl acetate synthesis reactor (106) is C2H4:CH3COOH:O2:H2O:CO2=60-75:12-18:4-6:2-5:6-9 in terms of molar ratio.

3. The ethylene-based vinyl acetate process system according to claim 1, characterized in that: The first distillation tower (201) has 55-75 plates, an operating pressure of 0.0-0.15 MPaG, an operating temperature of 50-150°C, and a reflux ratio of 3.0-6.

0.

4. A process system for producing vinyl acetate from ethylene according to any one of claims 1 to 3, characterized in that: The liquid phase of the bottom of the stripping tower (110) in the first distillation tower (201) is fed from the 35th to 47th tower plates, and the liquid phase of the extractant stirring tank (122) is fed from the 25th to 35th tower plates.

5. The ethylene-based vinyl acetate process system according to claim 4, characterized in that: The first distillation tower (201) adopts extractive distillation, and the extractant comprises an extractant (a) and an extractant (b); the extractant (a) is the solution at the bottom of the acid washing / water washing tower (112); the extractant (b) is dimethyl sulfoxide, N,N-dimethylformamide, ethylene glycol monobutyl ether, ethylene glycol, 3,5,5-trimethylhexanol, 2,6-dimethylheptanol, cyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, benzyl alcohol, β- One or more of phenylethyl alcohol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 2,3-butylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,5-pentanediol, 2-butene-1,4-diol, 1,6-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol, pentaerythritol, 2-methylbutyric acid, and benzyl formate.

6. The ethylene-based vinyl acetate process system according to claim 5, characterized in that: The ratio of the mass flow rate of the extractant (b) to the mass flow rate of the vinyl acetate product is 0.0001-0.05:1; the extractant (b) can be enriched at the bottom of the acetic acid gasifier (102) and discharged regularly.

7. The ethylene-based vinyl acetate process system according to claim 1 or 6, characterized in that: In the inlet material of the ethyl acetate tower (209), the mass content of ethyl acetate is ≥0.3%, and the mass content of vinyl acetate is ≤0.2%.

8. The ethylene-based vinyl acetate process system according to claim 7, characterized in that: The mass content of ethyl acetate at the top of the first distillation tower (201) is ≤100ppm, the mass content of acetic acid at the top is ≤0.01%, and the mass content of vinyl acetate at the bottom is ≤0.1%.

9. A process system for producing vinyl acetate from ethylene according to claim 1, 2, 3, 5, 6 or 8, characterized in that: The mass content of ethyl acetate in vinyl acetate products is ≤80ppm.

10. The ethylene-based vinyl acetate process system according to claim 9, characterized in that: The absorbent is an aqueous solution of one or more of potassium carbonate, sodium carbonate, monoethanolamine, diethanolamine, methyldiethanolamine and diisopropanolamine.

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