Acetic acid separation process based on supercritical CO2 coupling with vacuum distillation

Abstract

This invention relates to an acetic acid separation process based on supercritical CO2 coupled vacuum distillation, belonging to the technical field of acetic acid separation. The process is as follows: S1, the pH of the dilute acetic acid feed solution is adjusted to 4.0-4.5, filtered, and then the pH-adjusted feed solution is fed into a calcium chloride packed layer for complexation, followed by desorption by carbon dioxide to obtain a pre-concentrated acetic acid solution; S2, the acetic acid solution is fed into the lower part of a distillation column with a built-in supercritical extraction section, and supercritical CO2 is introduced into the extraction section to obtain a pre-enriched acetic acid-CO2 mixture; S3, the pre-enriched acetic acid-CO2 mixture continues to flow into the rectification section at the top of the distillation column, controlling the pressure in the rectification section at 5-8 kPa and the temperature at 60-75℃ to obtain purified crude acetic acid product; S4, the purified crude acetic acid product continues to flow into a flash tank, controlling the pressure in the flash tank at 2-3 MPa and the temperature at 40-50℃ to obtain a deeply purified acetic acid product.

Description

Technical Field

[0001] This invention belongs to the technical field of acetic acid separation, and more specifically, relates to an acetic acid separation process based on supercritical CO2 coupled vacuum distillation. Background Technology

[0002] Acetic acid, as an important organic chemical raw material, is widely used in food, pharmaceuticals, electronics, coatings, and other fields. In industrial production, acetic acid often exists in dilute solution form (such as in chemical wastewater and fermentation broth), and its separation and purification mainly rely on traditional distillation processes. However, acetic acid and water have a strong association reaction, and traditional distillation requires multiple towers in series or the addition of entrainers (such as benzene or ethyl acetate), which presents the following problems:

[0003] ① High energy consumption: Traditional vacuum distillation consumes 350-400 kJ / kg of acetic acid per unit, and multi-tower operation further increases energy consumption.

[0004] ②Low separation efficiency: The extraction rate of acetic acid by single-tower distillation is only 75-80%, and multiple distillations are required to achieve high purity.

[0005] ③ Environmental risks: The entrainer is volatile, which can lead to product residues and exhaust emissions, polluting the environment.

[0006] ④ Equipment corrosion: Acetic acid is highly corrosive to ordinary steel, resulting in high maintenance costs for traditional equipment.

[0007] Therefore, it is of great significance to develop an efficient, low-consumption, and environmentally friendly method for separating acetic acid. Summary of the Invention

[0008] The purpose of this invention is to provide an acetic acid separation process based on supercritical CO2 coupled vacuum distillation, which is environmentally friendly and highly efficient.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] An acetic acid separation process based on supercritical CO2 coupled vacuum distillation includes the following steps:

[0011] S1. Adjust the pH value of the dilute acetic acid raw material solution to 4.0-4.5, filter it, and send the pH-adjusted raw material solution into the calcium chloride filling layer for complexation. Then, introduce carbon dioxide at a pressure of 1.5-2MPa for desorption to obtain a preliminarily concentrated acetic acid solution. The calcium chloride filling layer is formed by filling anhydrous calcium chloride with a particle size of 3-5mm.

[0012] S2. The acetic acid solution is fed into the feed inlet at the bottom of the distillation column with a built-in supercritical extraction section. Supercritical CO2 is introduced into the extraction section, and the temperature of the extraction section is controlled at 31-40℃ and the pressure is 7.5-10MPa to obtain a pre-enriched acetic acid-CO2 mixture.

[0013] S3. The pre-enriched acetic acid-CO2 mixture continues to flow into the rectification section at the top of the distillation column. The pressure in the rectification section is controlled at 5-8 kPa and the temperature at 60-75℃, so that the supercritical CO2 is volatilized and separated at the top of the column to obtain purified crude acetic acid.

[0014] S4. The purified crude acetic acid product continues to flow into the flash tank. The pressure of the flash tank is controlled at 2-3 MPa and the temperature at 40-50℃ to remove residual supercritical CO2 and obtain a deeply purified acetic acid product.

[0015] This technical solution utilizes the carboxyl dissociation property of acetic acid to adjust the pH of the dilute acetic acid feed solution to 4.0-4.5. Within this pH range, acetic acid exists primarily in its molecular state, with a small amount in its dissociated state. Molecular acetic acid is more soluble in supercritical CO2, thus increasing its solubility. Dissociated acetic acid can form weak hydrogen bonds with water, preventing excessive dilution. After pH adjustment, the feed solution is filtered to remove any trace amounts of salt residue that may be generated, preventing blockage of the supercritical system. Furthermore, this technical solution also utilizes the complexation effect of acetic acid with anhydrous calcium chloride, i.e., the carboxyl group of acetic acid can react with Ca... 2+ A stable six-membered ring complex is formed, while water and Ca... 2+ Only an unstable four-membered ring is formed, which can complex acetic acid, while water is discharged with the effluent; the complexed acetic acid is desorbed from calcium chloride by CO2, and a preliminary concentrated acetic acid solution is obtained.

[0016] In the supercritical CO2 process, a supercritical extraction section is set in the lower part of the distillation column. Supercritical CO2 mainly acts as a non-polar extractant, physically dissolving acetic acid. Utilizing the high selectivity of supercritical CO2 for acetic acid, the concentration of acetic acid in the gas phase is increased, thus obtaining a pre-enriched acetic acid-CO2 mixture. The enriched acetic acid-CO2 mixture flows into the rectification section, where the boiling point of acetic acid is lowered (60-75℃) by reducing pressure (5-8 kPa). Taking advantage of the volatility of supercritical CO2 (critical temperature 31.1℃), rapid separation of CO2 and acetic acid is achieved at the top of the column, yielding purified crude acetic acid. The CO2 is condensed, compressed, and recycled. The small amount of incompletely separated supercritical CO2 contained in the purified crude acetic acid is further recovered through a flash evaporator, thus obtaining a deeply purified acetic acid product.

[0017] Further, in step S1, the calcium chloride filling layer is formed by filling anhydrous calcium chloride with a particle size of 3-5 mm, with a height of 1.5-2 m, and the volume of anhydrous calcium chloride in the calcium chloride filling layer is 20-30 L.

[0018] Furthermore, when the mass percentage of the dilute acetic acid raw material is ≤15%, the mass ratio of the dilute acetic acid raw material to the calcium chloride filling layer is 3-5:1; when the mass percentage of the dilute acetic acid raw material is >15%, the mass ratio of the dilute acetic acid raw material to the calcium chloride filling layer is 2-4:1.

[0019] Furthermore, in step S2, the supercritical extraction section is filled with corrugated packing material, the specific surface area of ​​which is 250-350 m². 2 / m 3 The supercritical CO2 is distributed through a distributor, with a gas-liquid contact efficiency of ≥92%.

[0020] In this technical solution, although supercritical CO2 has gas-like flow properties, its density is close to that of a liquid, with low viscosity but high mass flow rate. If it is directly introduced into the column from a single point or through a small hole, it can easily lead to uneven flow, decreased mass transfer efficiency, pressure drop fluctuations, or flooding risks. Especially in packed or tray structures, uneven flow may cause operational instability. A distributor can ensure that supercritical CO2 is uniformly dispersed into fine streams or microbubbles, maximizing the phase interface area and improving acetic acid extraction efficiency.

[0021] Furthermore, the corrugated packing is made of 316L stainless steel, with a corrugation angle of 30°, and 8-10 trays per meter of packing.

[0022] Furthermore, in step S2, the feed temperature of the acetic acid solution is 25-35℃, the feed pressure is 0.3-0.5MPa, and the feed temperature of the supercritical CO2 is 45-55℃.

[0023] In this process, acetic acid solution and supercritical CO2 exchange heat when they come into contact in the extraction section, achieving an extraction section temperature of 31-40℃, which reduces the system's energy consumption.

[0024] Furthermore, in step S3, after the supercritical CO2 is volatilized and separated at the top of the column, it is recovered through condensation and compression processes and returned to the extraction section for recycling; wherein the temperature of the condensation and compression process is 20-25℃ and the pressure is 7.5-10MPa.

[0025] Furthermore, in step S3, the rectification section is filled with metal wire mesh packing.

[0026] Furthermore, the metal wire mesh filler is of type BX, with a wire diameter of 0.12-0.15 mm and a porosity of 95%-97%.

[0027] Furthermore, after step S4, step S5 is also included: microwave-assisted molecular distillation. Specifically, the deeply purified acetic acid product is fed into a microwave-assisted molecular distillation device, and the microwave power is controlled at 300-800W, the operating vacuum degree is 0.1-1Pa, the evaporation temperature is 55-65℃, and the condensation temperature is 20-25℃, in order to remove formic acid, acetaldehyde, and heavy ester impurities to obtain a high-purity acetic acid product.

[0028] Furthermore, the microwave-assisted molecular distillation equipment is equipped with 4-6 sets of ring microwave antennas.

[0029] Preferably, the radiated power density of the loop microwave antenna is 20-30 W / cm². 2 The distance between the antenna and the evaporation wall is 5-8cm.

[0030] Furthermore, the microwave-assisted molecular distillation equipment is equipped with a rotating scraper with a rotation speed of 300-500 rpm to expand the evaporation area.

[0031] Furthermore, in step S5, the specific operation of controlling the microwave power to 300-800W is as follows: first control the microwave power to 300-400W for 10-20 minutes, then increase the microwave power to 600-800W and continue working for 15-30 minutes.

[0032] In this technical solution, the supercritical CO2 coupled vacuum distillation process utilizes the low viscosity and high diffusion coefficient characteristics of supercritical CO2 (SC-CO2) to construct a "supercritical extraction-distillation synergistic separation" mechanism in a vacuum distillation system. This addresses the pain points of strong association between acetic acid and water, making separation difficult and high energy consumption in traditional distillation. This method is particularly suitable for the concentration and purification of dilute acetic acid solutions (mass fraction 30-60 wt%), simplifying the traditional 2-3 distillation columns into a single-column coupled system, significantly improving separation efficiency.

[0033] The beneficial effects of this invention are:

[0034] This invention breaks through the technical bottleneck of traditional acetic acid separation by coupling supercritical CO2 with vacuum distillation, achieving efficient, low-consumption, and environmentally friendly acetic acid separation. The optional microwave-assisted purification scheme further expands the product's application scenarios, making it suitable for acetic acid production and recycling in chemical, pharmaceutical, and electronic fields, with significant economic and environmental benefits and broad industrialization prospects. Detailed Implementation

[0035] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0036] Example 1

[0037] An acetic acid separation process based on supercritical CO2 coupled vacuum distillation includes the following steps:

[0038] S1. Add 0.1 mol / L sodium bicarbonate solution to a 30 wt% dilute acetic acid feed solution to adjust the pH value of the dilute acetic acid feed solution to 4.2. After pH adjustment, the feed solution is filtered through a 0.22 micron filter membrane and then fed into a calcium chloride packed layer for complexation. Then, carbon dioxide at a pressure of 1.5-2 MPa is introduced for desorption to obtain a preliminarily concentrated acetic acid solution. The calcium chloride packed layer is formed by filling anhydrous calcium chloride with a particle size of 3-5 mm, with a height of 1.8 m and a volume of 20-30 L.

[0039] S2. The initially concentrated acetic acid solution is diverted at 10m... 3 A flow rate of 120 m³ / h is fed into the lower feed inlet of the distillation column with a built-in supercritical extraction section, and SC-CO2 is introduced into the extraction section. 3 / h, the temperature of the extraction section is controlled at 35℃ and the pressure at 8MPa; SC-CO2 mainly acts as a non-polar extractant, physically dissolving with acetic acid to increase the concentration of acetic acid in the gas phase, thus obtaining a pre-enriched acetic acid-CO2 mixture;

[0040] S3. The enriched acetic acid-CO2 mixture continues to flow into the rectification section at the top of the distillation column. The pressure in the rectification section is controlled at 6 kPa, the bottom temperature at 70℃, and the top temperature at 45℃. Taking advantage of the low critical temperature (31.1℃) of SC-CO2, the supercritical CO2 is volatilized and separated at the top of the column, and the purified crude acetic acid product solution is obtained in the bottom of the column.

[0041] S4. The purified crude acetic acid solution continues to flow into the flash evaporator, where the pressure is controlled at 2.5 MPa and the temperature at 45°C to remove residual supercritical CO2, yielding a deeply purified acetic acid product. Additionally, the SC-CO2 at the top of the column is condensed in a condenser (22°C), compressed to 8 MPa by a compressor, and then returned to the extraction section for recovery and reuse.

[0042] Example 2

[0043] An acetic acid separation process based on supercritical CO2 coupled vacuum distillation includes the following steps:

[0044] S1. Add 0.1 mol / L sodium bicarbonate solution to a 40 wt% dilute acetic acid feed solution to adjust the pH value of the dilute acetic acid feed solution to 4.0. After pH adjustment, the feed solution is filtered through a 0.22 micron filter membrane and then fed into a calcium chloride packed layer for complexation. Then, carbon dioxide at a pressure of 1.5-2 MPa is introduced for desorption to obtain a preliminarily concentrated acetic acid solution. The calcium chloride packed layer is formed by filling anhydrous calcium chloride with a particle size of 3-5 mm, with a height of 1.8 m and a volume of 20-30 L.

[0045] S2. The initially concentrated acetic acid solution is diverted to a flow rate of 8m... 3A flow rate of / h is fed into the lower feed inlet of the distillation column with a built-in supercritical extraction section, and SC-CO2 is introduced into the extraction section at a flow rate of 100m³ / h. 3 / h, the temperature of the extraction section is controlled at 38℃ and the pressure at 9MPa. SC-CO2 mainly acts as a non-polar extractant, physically dissolving with acetic acid to increase the concentration of acetic acid in the gas phase, thus obtaining a pre-enriched acetic acid-CO2 mixture.

[0046] S3. The enriched acetic acid-CO2 mixture continues to flow into the rectification section at the top of the distillation column. The pressure in the rectification section is controlled at 5 kPa, the bottom temperature at 65℃, and the top temperature at 42℃. Taking advantage of the low critical temperature (31.1℃) of SC-CO2, the supercritical CO2 is volatilized and separated at the top of the column, and the purified crude acetic acid product solution is obtained in the bottom of the column.

[0047] S4. The purified crude acetic acid solution continues to flow into the flash evaporator, where the pressure is controlled at 2 MPa and the temperature at 40°C to remove residual supercritical CO2, yielding a deeply purified acetic acid product. Additionally, the SC-CO2 at the top of the column is condensed in a condenser (20°C), compressed to 8 MPa by a compressor, and then returned to the extraction section for recovery and reuse.

[0048] Example 3

[0049] An acetic acid separation process based on supercritical CO2 coupled vacuum distillation includes the following steps:

[0050] S1. Add 0.1 mol / L sodium bicarbonate solution to a 20 wt% dilute acetic acid feed solution to adjust the pH value of the dilute acetic acid feed solution to 4.5. After pH adjustment, the feed solution is filtered through a 0.22 micron filter membrane and then fed into a calcium chloride packed layer for complexation. Then, carbon dioxide at a pressure of 1.5-2 MPa is introduced for desorption to obtain a preliminarily concentrated acetic acid solution. The calcium chloride packed layer is formed by filling anhydrous calcium chloride with a particle size of 3-5 mm, with a height of 1.8 m and a volume of 20-30 L.

[0051] S2. The initially concentrated acetic acid solution is diverted at 12m... 3 A flow rate of 140 m³ / h is fed into the lower feed inlet of a distillation column with a built-in supercritical extraction section. The feed temperature is 25°C, which is then increased to 30°C via a preheater. SC-CO2 is introduced into the extraction section at a flow rate of 140 m³ / h. 3 / h, the temperature of the extraction section is controlled at 32℃ and the pressure at 8.5MPa. SC-CO2 mainly acts as a non-polar extractant, physically dissolving with acetic acid to increase the concentration of acetic acid in the gas phase, thus obtaining a pre-enriched acetic acid-CO2 mixture.

[0052] S3. The enriched acetic acid-CO2 mixture is continued to flow into the rectification section at the top of the distillation column. The pressure in the rectification section is controlled at 7 kPa, the bottom temperature at 72℃, and the top temperature at 48℃. The reflux ratio is controlled at 3.5. Taking advantage of the low critical temperature (31.1℃) of SC-CO2, the supercritical CO2 is volatilized and separated at the top of the column, and the purified crude acetic acid product solution is obtained in the bottom of the column.

[0053] S4. The purified crude acetic acid solution continues to flow into the flash evaporator, where the pressure is controlled at 2.8 MPa and the temperature at 48°C to remove residual supercritical CO2, yielding a deeply purified acetic acid product. Additionally, the SC-CO2 at the top of the column is condensed in a condenser (23°C), compressed to 8 MPa by a compressor, and then returned to the extraction section for recovery and reuse.

[0054] Example 4

[0055] An acetic acid separation process based on supercritical CO2 coupled vacuum distillation includes the following steps:

[0056] S1. A 30wt% dilute acetic acid feed solution is added at a flow rate of 10m... 3 A flow rate of / h is fed into the lower feed inlet of the distillation column with a built-in supercritical extraction section, and SC-CO2 is introduced into the extraction section at a flow rate of 80m³ / h. 3 / h, the extraction section temperature is 39℃ and the pressure is 9.5MPa. SC-CO2 mainly acts as a non-polar extractant, physically dissolving with acetic acid to increase the concentration of acetic acid in the gas phase, thus obtaining a pre-enriched acetic acid-CO2 mixture;

[0057] S2. The enriched acetic acid-CO2 mixture is continued to flow into the rectification section at the top of the distillation column. The pressure in the rectification section is controlled at 5 kPa, the bottom temperature at 63℃, and the top temperature at 40℃. The reflux ratio is controlled at 2.5. Taking advantage of the low critical temperature (31.1℃) of SC-CO2, the supercritical CO2 is volatilized and separated at the top of the column, and the purified crude acetic acid product solution is obtained in the bottom of the column.

[0058] S3. The purified crude acetic acid solution continues to flow into the flash evaporator, where the pressure is controlled at 2.2 MPa and the temperature at 42°C to remove residual supercritical CO2, yielding a deeply purified acetic acid product. Additionally, the SC-CO2 at the top of the column is condensed in a condenser (21°C), compressed to 8 MPa by a compressor, and then returned to the extraction section for recovery and reuse.

[0059] Example 5

[0060] The deeply purified acetic acid product obtained in Example 1 was fed into a microwave-assisted molecular distillation apparatus. The feed flow rate was controlled at 500 L / h, the microwave power at 350 W, and the sample was held for 10 minutes to remove acetaldehyde. The microwave power was then increased to 700 W, and the sample was held for 20 minutes to separate formic acid and heavy esters. During this process, the vacuum degree was controlled at 0.5 Pa, the evaporation temperature at 60 °C, the condensation temperature at 23 °C, and the scraper speed at 400 rpm. The final acetic acid product was collected.

[0061] Example 6

[0062] The deeply purified acetic acid product obtained in Example 3 was fed into a microwave-assisted molecular distillation apparatus. The feed flow rate was controlled at 500 L / h, the microwave power was first set at 350 W for 10 minutes, then increased to 700 W for 20 minutes, and the cycle was repeated for 72 hours. The scraper speed was 400 rpm, and the scraper was cleaned every 12 hours. At the same time, the vacuum system maintained a stable vacuum of 0.3 Pa, the evaporation temperature was 60 °C, the condensation temperature was 23 °C, the molecular pump oil was replaced every 8 hours, and the final acetic acid product was collected.

[0063] Example 7

[0064] This embodiment uses a traditional vacuum distillation process to separate dilute acetic acid, and the preparation method includes the following steps:

[0065] S1. A 30 wt% dilute acetic acid feedstock is introduced into the extraction tower, while ethyl acetate is added as the extractant from the top of the tower. Inside the tower, the extractant and dilute acetic acid are thoroughly mixed through countercurrent contact. Utilizing the difference in the partition coefficient of acetic acid between the extractant and the aqueous phase, acetic acid is transferred from the aqueous phase to the extractant phase. At a temperature of 35°C and a pressure of 0.08 MPa, through multi-stage mass transfer, the concentration of acetic acid in the extractant phase is increased, and the raffinate phase (mainly water and a small amount of incompletely extracted acetic acid and extractant) is discharged from the bottom of the tower.

[0066] S2. The extract phase is fed into a distillation column and distilled at 0.02 MPa. The top temperature of the distillation column is controlled at 45°C, the bottom temperature at 90°C, and the reflux ratio at 3.5 to obtain acetic acid.

[0067] The acetic acid products obtained in Examples 1-7 were subjected to performance tests, and the test results are shown in Table 1.

[0068] Table 1

[0069]

[0070] As shown in Table 1, compared with Example 7, under the same raw material acetic acid concentration, Example 1 yields a product with higher acetic acid purity, higher acetic acid extraction rate, and lower unit energy consumption, demonstrating high efficiency and low consumption performance advantages. Similarly, in Examples 2-3, under different raw material acetic acid concentrations, the product acetic acid purity exceeded 99.5%, the acetic acid extraction rate exceeded 92%, and the energy consumption was less than 205 kJ / kg acetic acid. This indicates that the present invention, through pH-controlled supercritical extraction, the complexation of acetic acid with anhydrous calcium chloride, and the coupling of supercritical CO2 and vacuum distillation, breaks through the technical bottleneck of traditional acetic acid separation, achieving high efficiency and low consumption acetic acid separation. In Example 4, the acetic acid purity of the product obtained by coupling supercritical CO2 and vacuum distillation alone was slightly lower, indicating that the pH-controlled supercritical extraction and the complexation of acetic acid with anhydrous calcium chloride have a synergistic effect. Moreover, the SC-CO2 recycling rate in Examples 1-4 is higher than 99%, demonstrating that the present invention has environmentally friendly, safe, and cost-saving technical effects. In addition, the acetic acid products obtained by the optional microwave-assisted purification schemes in Examples 5 and 6 have higher purity, meeting the high purity requirements of electronic and pharmaceutical grades, adapting to different application scenarios, further expanding the application fields of the products, meeting the acetic acid product requirements of chemical, pharmaceutical, and electronic fields, and having significant economic and environmental benefits, with broad prospects for industrialization.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An acetic acid separation process based on supercritical CO2 coupled vacuum distillation, characterized in that, Includes the following steps: S1. Adjust the pH value of the dilute acetic acid raw material solution to 4.0-4.5, filter it, and send the pH-adjusted raw material solution into the calcium chloride packed layer for complexation. Then, introduce carbon dioxide at a pressure of 1.5-2 MPa for desorption to obtain a preliminarily concentrated acetic acid solution. S2. The acetic acid solution is fed into the feed inlet at the bottom of the distillation column with a built-in supercritical extraction section. Supercritical CO2 is introduced into the extraction section, and the temperature of the extraction section is controlled at 31-40℃ and the pressure is 7.5-10MPa to obtain a pre-enriched acetic acid-CO2 mixture. S3. The pre-enriched acetic acid-CO2 mixture continues to flow into the rectification section at the top of the distillation column. The pressure in the rectification section is controlled at 5-8 kPa and the temperature at 60-75℃, so that the supercritical CO2 is volatilized and separated at the top of the column to obtain purified crude acetic acid. S4. The purified crude acetic acid product continues to flow into the flash tank. The pressure of the flash tank is controlled at 2-3 MPa and the temperature at 40-50℃ to remove residual supercritical CO2 and obtain a deeply purified acetic acid product. In step S1, the calcium chloride filling layer is formed by filling anhydrous calcium chloride with a particle size of 3-5 mm, with a height of 1.5-2 m and a volume of anhydrous calcium chloride in the calcium chloride filling layer of 20-30 L. When the mass percentage of dilute acetic acid raw material is ≤15%, the mass ratio of the dilute acetic acid raw material to the calcium chloride filling layer is 3-5:1; when the mass percentage of dilute acetic acid raw material is >15%, the mass ratio of the dilute acetic acid raw material to the calcium chloride filling layer is 2-4:

1.

2. The acetic acid separation process based on supercritical CO2 coupled vacuum distillation according to claim 1, characterized in that, In step S2, the supercritical extraction section is filled with corrugated packing material with a specific surface area of ​​250-350 m². 2 / m 3 .

3. The acetic acid separation process based on supercritical CO2 coupled vacuum distillation according to claim 1, characterized in that, In step S2, the supercritical CO2 is distributed through a distributor, with a gas-liquid contact efficiency of ≥92%.

4. The acetic acid separation process based on supercritical CO2 coupled vacuum distillation according to claim 1, characterized in that, In step S2, the feed temperature of the acetic acid solution is 25-35℃, the feed pressure is 0.3-0.5MPa, and the feed temperature of the supercritical CO2 is 45-55℃.

5. The acetic acid separation process based on supercritical CO2 coupled vacuum distillation according to claim 1, characterized in that, In step S3, after the supercritical CO2 is volatilized and separated at the top of the column, it is recovered through condensation and compression processes and returned to the extraction section for recycling; wherein the temperature of the condensation and compression process is 20-25℃ and the pressure is 7.5-10MPa.

6. The acetic acid separation process based on supercritical CO2 coupled vacuum distillation according to claim 1, characterized in that, In step S3, the rectification section is filled with metal wire mesh packing.

7. The acetic acid separation process based on supercritical CO2 coupled vacuum distillation according to claim 1, characterized in that, After step S4, step S5 is also included: microwave-assisted molecular distillation. Specifically, the deeply purified acetic acid product is fed into a microwave-assisted molecular distillation device, and the microwave power is controlled at 300-800W, the operating vacuum degree is 0.1-1Pa, the evaporation temperature is 55-65℃, and the condensation temperature is 20-25℃ to remove formic acid, acetaldehyde, and heavy ester impurities to obtain a high-purity acetic acid product.

8. The acetic acid separation process based on supercritical CO2 coupled vacuum distillation according to claim 7, characterized in that, In step S5, the specific operation of controlling the microwave power to 300-800W is as follows: first control the microwave power to 300-400W for 10-20 minutes, then increase the microwave power to 600-800W and continue to work for 15-30 minutes.

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