Adsorption tank for acetonitrile purification and device and method for preparing chromatographic grade acetonitrile from acetonitrile wastewater, and acetonitrile

Abstract

The present invention provides an adsorption tank for acetonitrile purification, an apparatus and method for preparing chromatographic-grade acetonitrile from acetonitrile wastewater, and the resulting acetonitrile. The method comprises: adding alkali to the acetonitrile wastewater for pretreatment, then passing the wastewater through a microfiltration unit, passing the impurity-removed acetonitrile wastewater through a cryogenic freezing unit to obtain an organic layer, passing the organic layer through a first distillation tower, and obtaining an acetonitrile distillate in the bottom of the tower; passing the acetonitrile distillate and an extractant through a second extractive distillation tower to purify high-purity acetonitrile, passing the high-purity acetonitrile through an adsorption tank for adsorption and impurity removal, and passing the adsorbed high-purity acetonitrile through an ultrafiltration unit to remove particulates therein to obtain chromatographic-grade acetonitrile. The present invention can use acetonitrile wastewater generated in the biopharmaceutical industry as raw material, and through microfiltration, phase separation, extractive distillation, adsorption, and ultrafiltration, can achieve an acetonitrile recovery rate greater than 90%, an acetonitrile content in the wastewater less than 1%, and produce chromatographic-grade acetonitrile with a moisture content of less than 300 ppm and a mass percentage of ≥99.95%.

Description

Technical Field

[0001] The present invention relates to an adsorption tank for acetonitrile purification, a device for preparing chromatographic-grade acetonitrile from acetonitrile wastewater, a method for preparing chromatographic-grade acetonitrile from acetonitrile wastewater in the pharmaceutical industry, and acetonitrile obtained by the method. Background Art

[0002] Acetonitrile is a highly volatile, colorless liquid with an ethereal odor. With excellent solubility, it is widely used in various fields, including medicine, chemicals, and analysis. 70% of acetonitrile's downstream use is in the pharmaceutical industry. As an excellent reaction solvent, it can be used in various pharmaceutical synthesis reactions, such as the synthesis of cephalosporin intermediates, peptide drugs, and vitamin preparation. However, after the reaction is completed, a large amount of acetonitrile wastewater is generated. This acetonitrile wastewater is often highly complex, containing not only acetonitrile and water, but also large amounts of proteins, organic salts, and solid impurities. Direct discharge of this wastewater can pose a significant environmental risk due to high COD values.

[0003] Currently, there are two main methods for treating this type of wastewater. The first is direct incineration. However, incineration of the wastewater will produce a large amount of greenhouse gases and cause serious waste of acetonitrile resources. The second is to recycle the wastewater and concentrate and purify the acetonitrile in it for reuse. This can not only greatly reduce environmental pressure, but also enable the reuse of mismatched acetonitrile resources, with good economic benefits. Therefore, it is very necessary to develop a set of efficient, energy-saving, high-recovery, and high-concentration purified acetonitrile wastewater recovery processes and equipment.

[0004] CN104926690A discloses a method and apparatus for recovering and refining acetonitrile used in the synthesis of ceftriaxone sodium. The method primarily utilizes multiple distillation towers connected in series and a pervaporation membrane separation unit to recover and purify acetonitrile. This method has a high degree of automation, does not introduce a third component, and produces high product purity. However, the recovery process requires evaporating a large amount of water in the distillation towers, resulting in high energy consumption and poor economic efficiency.

[0005] CN109593050A discloses a method for recovering acetonitrile from an acetonitrile-water mixture. The main technical principle is to select a suitable extractant, extract and separate the acetonitrile and water, and then distill the extract to obtain purified acetonitrile. This method is simple and has high recovery efficiency. However, it does not take into account the separation of other impurities in the wastewater. The resulting purified acetonitrile is of low purity and cannot be directly used for subsequent use. It needs to be further purified by other methods.

[0006] CN108794348A discloses a method for preparing high-purity acetonitrile from biopharmaceutical waste acetonitrile. The main steps include pretreatment, azeotropic distillation, dehydration in a dehydration tower, adsorption in a composite adsorption tower, and high-efficiency distillation. This method is complex and requires a third component, an entrainer, which consumes a large amount of energy for azeotropic distillation. Summary of the Invention

[0007] In response to the above-mentioned problems in the prior art, the present invention aims to provide a process and apparatus for preparing chromatographic-grade acetonitrile from acetonitrile wastewater in the pharmaceutical industry. By employing techniques such as low-temperature stratification and ionic liquid extraction and distillation, the present invention overcomes the challenges encountered in the prior art of separating acetonitrile from water, such as high energy consumption and the introduction of new impurities by adding a third component. Furthermore, the present invention also fully considers the removal of other trace impurities in the acetonitrile, thereby producing acetonitrile of chromatographic-grade purity. Furthermore, the apparatus utilizes a self-designed adsorption tank, which offers advantages such as high adsorption efficiency, easy disassembly and cleaning, and semi-automatic operation.

[0008] According to a first aspect of the present invention, the present invention provides an adsorption tank for acetonitrile purification, which includes a tank body and a material receiving frame; the tank body has a cavity with a circular cross-section, and at least the upper and lower parts of the cavity wall are respectively provided with annular slide rails; the material receiving frame has a circular cross-section and is used to load an adsorbent, and the height and corresponding cross-sectional diameter of the material receiving frame are both smaller than the tank body. At least two baffles are vertically provided inside the material receiving frame, dividing the interior of the material receiving frame into at least three spaces for loading different adsorbents, and small holes are opened on the outer wall of the material receiving frame so that the liquid phase can pass freely but the adsorbent cannot pass through; the material receiving frame is installed on the annular slide rail by a fixed sliding device, so that the material receiving frame can rotate inside the tank body.

[0009] According to a second aspect of the present invention, the present invention provides an apparatus for preparing chromatographic-grade acetonitrile from acetonitrile wastewater, the apparatus comprising: a microfiltration unit, a cryogenic freezing unit, a first distillation tower, a second extractive distillation tower, optionally a third distillation tower, an adsorption tank and an ultrafiltration unit; wherein the outlet of the microfiltration unit is connected to the inlet of the cryogenic freezing unit; the organic layer outlet of the cryogenic freezing unit is connected to the feeding port of the first distillation tower; the top outlet of the first distillation tower is connected to the outside, and the kettle outlet of the first distillation tower is connected to the acetonitrile distillate feeding port of the second extractive distillation tower; the top outlet of the second extractive distillation tower is connected to the inlet of the adsorption tank, and the kettle outlet of the second extractive distillation tower is connected to the feeding port of the third distillation tower; the top outlet of the third distillation tower is connected to the outside, and the kettle outlet of the third distillation tower is connected to the extractant feeding port of the second extractive distillation tower; the adsorption tank outlet is connected to the inlet of the ultrafiltration unit, and the ultrafiltration unit outlet discharges chromatographic-grade acetonitrile, and preferably the adsorption tank is the adsorption tank described in the present invention.

[0010] According to a third aspect of the present invention, the present invention provides a method for preparing chromatographic grade acetonitrile using acetonitrile wastewater in the pharmaceutical industry, the method comprising:

[0011] Step 1: Add alkali to the acetonitrile wastewater for pretreatment, and then pass it into a microfiltration unit to remove impurities including proteins, organic salts and solids in the wastewater through the filter membrane;

[0012] Step 2: passing the acetonitrile wastewater after impurity removal into a low-temperature freezing unit to separate the wastewater into a water or ice layer and an organic layer;

[0013] Step 3: passing the organic layer into the first distillation tower to remove the volatile light components, and obtaining acetonitrile distillate in the bottom of the tower;

[0014] Step 4: passing the acetonitrile distillate and the extractant into a second extractive distillation tower, and refining the acetonitrile by extractive distillation in the second extractive distillation tower to obtain high-purity acetonitrile and a mixed solution of water and the extractant;

[0015] Step 5: Pass high-purity acetonitrile into the adsorption tank for adsorption and impurity removal to remove small molecular organic impurities, metal ions and trace moisture;

[0016] Step 6: The adsorbed high-purity acetonitrile is then passed through an ultrafiltration unit to remove the particles therein to obtain chromatographic grade acetonitrile;

[0017] Optionally, the mixture of water and extractant is separated by a third distillation tower, and the extractant is returned to the second extractive distillation tower as an extractant raw material for extractive distillation. Preferably, the adsorption tank is the adsorption tank described in the present invention.

[0018] According to a fourth aspect of the present invention, the present invention provides acetonitrile obtained by the method described in the present invention, wherein the acetonitrile is chromatographic grade, the mass percentage of acetonitrile is ≥99.95%, and the water content is less than 300 ppm.

[0019] The present invention utilizes a self-designed adsorption tank that can simultaneously load three different adsorbents, meeting the purification needs of simultaneously adsorbing different types of impurities. The adsorbents are loaded via a separate frame, making disassembly and cleaning easy and requiring minimal space. Furthermore, the tank's internal frame can spin under external drive, ensuring full contact between the adsorbents and the acetonitrile liquid, increasing the contact area between the loaded adsorbents and the acetonitrile and thereby improving adsorption efficiency.

[0020] The invention can use acetonitrile wastewater generated in the biopharmaceutical industry as a raw material, and through microfiltration, phase separation, extraction and rectification, adsorption, ultrafiltration and other steps, the acetonitrile recovery rate can be greater than 90%, the acetonitrile content in the wastewater is less than 1%, and chromatographic grade acetonitrile with a water content of less than 300 ppm and a mass percentage of ≥99.95% can be prepared.

[0021] The present invention preferably adopts a low-temperature cooling and stratification method, which can remove a large amount of water in acetonitrile before distillation, thereby saving energy consumption in evaporating water in a subsequent distillation tower.

[0022] The present invention preferably uses an ionic liquid as an extractant. By utilizing the different interaction forces of the ionic liquid on water and acetonitrile, the relative volatility between acetonitrile and water can be effectively increased, the azeotropic point can be eliminated, and acetonitrile with a mass fraction of greater than 99% can be produced through extractive distillation. At the same time, the ionic liquid is almost non-volatile, and the water and the ionic liquid after the extractive distillation can be completely separated by a single distillation tower. The separated ionic liquid can be recycled and reused in the extractive distillation, thereby achieving good environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention provides a flow chart for preparing chromatographic-grade acetonitrile from acetonitrile wastewater produced by biopharmaceuticals.

[0024] Figure 2 The present invention is a schematic diagram of the structure of an apparatus for preparing chromatographic-grade acetonitrile from acetonitrile wastewater produced by biopharmaceuticals.

[0025] Figure 3 This is a schematic diagram of the front structure of the adsorption tank of the present invention.

[0026] Figure 4 This is an axonometric schematic diagram of the adsorption tank of the present invention.

[0027] Description of Reference Numerals

[0028] Figure 1 In the figure, A is acetonitrile wastewater, B is organic layer logistics, C is volatile light component logistics, D is acetonitrile distillate, E is extractant, F is high-purity acetonitrile, G is the side line discharge of the third distillation tower, H is extractant logistics, and I is chromatographic grade acetonitrile.

[0029] Figure 2 In the figure, 1 is a microfiltration unit, 2 is a low-temperature freezing tank, 3 is a first distillation tower, 4 is a second extractive distillation tower, 5 is a third distillation tower, 6 is an adsorption tank, and 7 is an ultrafiltration unit. DETAILED DESCRIPTION

[0030] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0031] The present invention provides an adsorption tank for acetonitrile purification, which comprises a tank body and a material receiving frame;

[0032] The tank body has a cavity with a circular cross section, and an annular slide is provided on at least the upper and lower parts of the cavity wall; the cross section of the material receiving frame is circular and is used to load the adsorbent. The height and corresponding cross-sectional diameter of the material receiving frame are both smaller than the tank body. At least two baffles are vertically provided inside the material receiving frame, dividing the interior of the material receiving frame into at least three spaces for loading different adsorbents. The outer wall of the material receiving frame is provided with small holes so that the liquid phase can pass freely while the adsorbent cannot pass; the material receiving frame is mounted on the annular slide by a fixed sliding device so that the material receiving frame can rotate inside the tank body. The adsorption tank of the present invention can be loaded with at least three different adsorbents at the same time, which can meet the purification requirements of simultaneously adsorbing different types of impurities; at the same time, the adsorbent is loaded through a separate frame, which is convenient for disassembly and cleaning and takes up little space. At the same time, the adsorption tank is designed so that the frame inside it can perform spin motion under external drive, so that the adsorbent can fully contact the acetonitrile liquid, increase the contact area between the loaded adsorbent and acetonitrile, and thus improve the adsorption efficiency.

[0033] According to a preferred embodiment of the present invention, the tank body has a cylindrical cavity; the material receiving frame is preferably cylindrical.

[0034] According to a preferred embodiment of the present invention, a support rod is installed on the upper portion of the material receiving frame, and the support rod can drive the material receiving frame to rotate under the drive of an external motor.

[0035] According to a preferred embodiment of the present invention, the outer wall of the material receiving frame is provided with evenly distributed small holes, preferably with a diameter of 1-2 mm.

[0036] According to a preferred embodiment of the present invention, four fixing buckles are installed at the quadrant points of the upper and lower circles of the material receiving frame, and the fixing buckles are embedded in the slide rails of the tank body, so that the material receiving frame can rotate in the tank body.

[0037] According to a preferred embodiment of the present invention, the tank body is the main body of the adsorption tank, and is preferably cylindrical; preferably, the bottom diameter of the tank body is 400-700 mm, and the height is 800-1200 mm.

[0038] According to a preferred embodiment of the present invention, the material of the material receiving frame can be various materials, including but not limited to polytetrafluoroethylene.

[0039] According to a preferred embodiment of the present invention, the baffle may be made of various materials, including but not limited to polytetrafluoroethylene.

[0040] According to a preferred embodiment of the present invention, the baffles are evenly arranged in the vertical direction of the material receiving frame to divide the inner part of the frame into at least three spaces with exactly the same volume.

[0041] According to a preferred embodiment of the present invention, the adsorption tank is mainly composed of a tank body and a material receiving frame. The tank body is the main part of the adsorption tank and is cylindrical with a bottom diameter of 400-700mm and a height of 800-1200mm. The upper and lower parts of the wall each have an annular slide rail. The material frame is the part for loading the adsorbent. It is made of polytetrafluoroethylene and is also cylindrical. Its height and bottom diameter are slightly smaller than the tank body. There are three layers of polytetrafluoroethylene baffles inside it, which divide the inner part of the tank body into three spaces of exactly the same volume. The three spaces can respectively hold different types of adsorbents; the outer wall of the material frame is provided with evenly distributed small holes, so that the liquid phase can pass freely but the adsorbent cannot pass through. The diameter of the small holes is 1-2mm; the quadrant points of the upper and lower circles of the material frame are each equipped with 4 fixing buckles, which can be embedded in the slide rail of the tank body, so that the material frame can rotate in the tank body; a support rod is installed on the upper part of the material frame, which can drive the material frame to rotate under the drive of an external motor.

[0042] The invention provides a device for preparing chromatographic-grade acetonitrile from acetonitrile wastewater. The device comprises: a microfiltration unit, a cryogenic freezing unit, a first distillation tower, a second extractive distillation tower, optionally a third distillation tower, an adsorption tank and an ultrafiltration unit; wherein the outlet of the microfiltration unit is communicated with the inlet of the cryogenic freezing unit; the organic layer outlet of the cryogenic freezing unit is communicated with the feeding port of the first distillation tower; the top outlet of the first distillation tower is communicated with the outside, and the kettle discharge port of the first distillation tower is connected with the feeding port of acetonitrile distillate of the second extractive distillation tower; the top outlet of the second extractive distillation tower is connected with the inlet of the adsorption tank, and the kettle discharge port of the second extractive distillation tower is communicated with the feeding port of the third distillation tower; the top outlet of the third distillation tower is communicated with the outside, and the kettle discharge port of the third distillation tower is communicated with the extractant feeding port of the second extractive distillation tower; the discharge port of the adsorption tank is communicated with the inlet of the ultrafiltration unit, and the chromatographic-grade acetonitrile is discharged from the outlet of the ultrafiltration unit. Preferably, the adsorption tank is the adsorption tank described in the invention.

[0043] According to the present invention, the low-temperature freezing unit is used for low-temperature freezing and can be a common low-temperature freezing equipment, such as a low-temperature freezing tank.

[0044] In the present invention, the third distillation tower is mainly used to recover the solvent and the extractant, and is used or equipped according to needs.

[0045] The device of the present invention can use acetonitrile wastewater generated by the biopharmaceutical industry as raw material, and through microfiltration, freezing unit phase separation, extraction distillation, adsorption, ultrafiltration and other steps, can achieve an acetonitrile recovery rate of more than 90%, the acetonitrile content in the wastewater is less than 1%, and chromatographic grade acetonitrile with a water content of less than 300 ppm and a mass percentage of ≥99.95% is produced.

[0046] The present invention provides a method for preparing chromatographic-grade acetonitrile by utilizing acetonitrile wastewater, the method comprising:

[0047] Step 1: Add alkali to the acetonitrile wastewater for pretreatment, and then pass it into a microfiltration unit to remove impurities including proteins, organic salts and solids in the wastewater through the filter membrane;

[0048] Step 2: The acetonitrile wastewater after impurity removal is passed into a low-temperature freezing unit to separate the wastewater into a water or ice layer and an organic layer; the low-temperature freezing will separate the wastewater into a water (ice) layer and an organic layer, and the water content in the organic layer will be greatly reduced, and then the organic layer is taken for subsequent refining operations;

[0049] Step 3: passing the organic layer into the first distillation tower to remove the volatile light components, and obtaining acetonitrile distillate in the bottom of the tower;

[0050] Step 4: passing the acetonitrile distillate and the extractant into a second extractive distillation tower, and refining the acetonitrile by extractive distillation in the second extractive distillation tower to obtain high-purity acetonitrile and a mixed solution of water and the extractant;

[0051] Step 5: Pass high-purity acetonitrile into the adsorption tank for adsorption and impurity removal to remove small molecular organic impurities, metal ions and trace moisture;

[0052] Step 6: The adsorbed high-purity acetonitrile is then passed through an ultrafiltration unit to remove the particles therein to obtain chromatographic grade acetonitrile;

[0053] Optionally, the mixture of water and extractant is separated by a third distillation tower, and the extractant is returned to the second extractive distillation tower as an extractant raw material for extractive distillation. Preferably, the adsorption tank is the adsorption tank described in the present invention.

[0054] In the present invention, the acetonitrile wastewater can be various common acetonitrile-containing wastewaters, and there is no special limitation on the sub-composition. According to a preferred embodiment of the present invention, based on 100 weight percent, the acetonitrile wastewater contains: 10-40% acetonitrile, 55-85% water, 1-2% protein, 1% other organic impurities, and 1-2% other solid impurities.

[0055] According to a preferred embodiment of the present invention, the pH of the acetonitrile wastewater is 4-6.

[0056] According to a preferred embodiment of the present invention, the acetonitrile wastewater is derived from wastewater of various production processes, preferably acetonitrile wastewater produced by biopharmaceuticals.

[0057] In the present invention, the base can be any commonly used base. According to a preferred embodiment of the present invention, in step 1, the base is preferably one or more of sodium hydroxide, sodium carbonate, calcium carbonate and potassium hydroxide.

[0058] In the present invention, the amount of the base is determined as needed. According to a preferred embodiment of the present invention, in step 1, the amount of base added is 2-5% of the mass of the acetonitrile wastewater.

[0059] In the present invention, the pH range of the alkali treatment is preferably 6-8.

[0060] In the present invention, the microfiltration unit can be a commonly used setting, for example, the microfiltration unit adopts membrane microfiltration, and the filter membrane can be a commonly used type. According to a preferred embodiment of the present invention, in step one, the filter membrane material of the microfiltration unit is cellulose carbonate, polypropylene, polycarbonate or silica.

[0061] According to a preferred embodiment of the present invention, in step 1, the pore size of the filter membrane of the microfiltration unit is 0.1-1 μm.

[0062] According to a preferred embodiment of the present invention, in step 2, the low-temperature freezing unit is a low-temperature freezing tank.

[0063] In the present invention, the temperature of the low-temperature freezing unit is determined as needed. According to a preferred embodiment of the present invention, in step 2, the temperature of the low-temperature freezing tank is set to -35°C to -15°C, and the acetonitrile wastewater is allowed to stand for 8-16 hours.

[0064] In the present invention, the purpose of the first distillation is to remove light components in the acetonitrile wastewater by distillation operation. According to a preferred embodiment of the present invention, in step three, the first distillation tower is a vacuum distillation operation, the top pressure is controlled at 0.6-0.8atm, the feed position is at the 5th to 9th plate, the number of plates is 12-20 plates, the bottom temperature is 70-80°C, and the reflux ratio is 0.5-3.

[0065] In the present invention, the purpose of the second extractive distillation is to add an extractant to increase the relative volatility of acetonitrile and water in the acetonitrile wastewater, and then separate the acetonitrile and water by distillation. According to a preferred embodiment of the present invention, in step 4, the second extractive distillation tower is an atmospheric distillation tower with 25-40 plates, the temperature of the distillation tower top is 75-85°C, the tower bottom temperature is 120-140°C, and the reflux ratio is 1-4.

[0066] According to a preferred embodiment of the present invention, in step 4, the acetonitrile distillate enters the tower from the 12th to 20th plates, and the extractant is added to the tower from the 6th to 10th plates. The feed amount of the extractant is 20-40% by weight of the acetonitrile distillate, and the mass fraction of the high-purity acetonitrile extracted from the top of the tower is greater than 99%.

[0067] According to a preferred embodiment of the present invention, in step 4, the extractant ionic liquid is, for example, one or more of 1-propyl-4-methylpyridinium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-propyl-2,3-methylpyridinium tetrafluoroborate, 1-pentyl imidazolium bis(trifluoromethanesulfonyl)imide and N-butylpyridinium bromide.

[0068] In the present invention, the purpose of the third distillation is to separate water from the extractant and return the extractant to the second distillation tower for recycling. According to a preferred embodiment of the present invention, the third distillation tower is a vacuum distillation tower, the tower pressure is controlled at 0.2-0.5atm, the number of tower plates is 18-30, the temperature at the top of the distillation tower is 90-105°C, the temperature at the bottom of the tower is 140-160°C, and the reflux ratio is 0.5-2; the mixed liquid of water and extractant enters the tower from the 8th to 15th plates, the mass fraction of water extracted from the top of the tower is greater than 99% and is directly discharged to the outside, and the extractant in the bottom of the tower with a water content of 1-5% by weight is returned to the second extractive distillation tower for use as the extractant.

[0069] In the present invention, the adsorbent may be of various types, and is mainly used to adsorb moisture, trace organic impurities and metal ions in acetonitrile wastewater. According to a preferred embodiment of the present invention, in step five, the adsorbent is selected from one or more of calcium chloride, phosphorus pentoxide, 3A molecular sieve, 5A molecular sieve, activated carbon fiber, activated alumina, strong acid cationic resin and weak acid anionic resin.

[0070] According to a preferred embodiment of the present invention, in step five, the particle size of the adsorbent is 5-10 mesh.

[0071] According to a preferred embodiment of the present invention, in step 5, the average residence time of high-purity acetonitrile in the adsorption tank is 4-8 hours.

[0072] According to a preferred embodiment of the present invention, in step five, the material receiving frame of the adsorption tank is provided with three spaces, which are filled with three different adsorbents, and the adsorbents include in sequence: a first adsorbent selected from 3A molecular sieve and / or 5A molecular sieve and / or calcium chloride and / or phosphorus pentoxide; a second adsorbent selected from one or more of 3A molecular sieve, 5A molecular sieve, activated carbon fiber and activated alumina; a third adsorbent selected from strong acid cationic resin and / or weak acid cationic resin, and the usage ratio of the three is 1-2:1-2:1-2.

[0073] According to the method of the present invention, the total recovery rate of acetonitrile is greater than 90%, the acetonitrile content in the wastewater directly discharged outside the boundary after recovery is less than 1%, the mass percentage of the chromatographic grade acetonitrile prepared is greater than or equal to 99.95%, and the water content is less than 300 ppm.

[0074] According to a preferred embodiment of the present invention, the filter membrane of the ultrafiltration unit can be various ultrafiltration devices, such as membrane ultrafiltration. The preferred filter membrane material is polyvinyl chloride, polyacrylonitrile, polysulfone, polyvinylidene fluoride or cellulose carbonate.

[0075] According to a preferred embodiment of the present invention, the pore size of the filter membrane of the ultrafiltration unit is 0.02-0.05 μm.

[0076] The present invention provides acetonitrile obtained by the method described in the present invention. The acetonitrile is of chromatography grade, the mass percentage of acetonitrile is greater than or equal to 99.95%, and the water content is less than 300 ppm.

[0077] The present invention is further described below by way of examples and comparative examples, but the method of the present invention is not limited thereto.

[0078] The method of the present invention is further described below with reference to the embodiments.

[0079] Figure 1 The present invention provides a flow chart for preparing chromatographic-grade acetonitrile from acetonitrile wastewater produced by biopharmaceuticals.

[0080] Figure 2 The present invention is a schematic diagram of the structure of an apparatus for preparing chromatographic-grade acetonitrile from acetonitrile wastewater produced by biopharmaceuticals.

[0081] Figure 3 This is a schematic diagram of the front structure of the adsorption tank of the present invention.

[0082] Figure 4 This is an axonometric schematic diagram of the adsorption tank of the present invention.

[0083] Figure 1 In the figure, A is acetonitrile wastewater, B is organic layer logistics, C is volatile light component logistics, D is acetonitrile distillate, E is extractant, F is high-purity acetonitrile, G is the side line discharge of the third distillation tower, H is extractant logistics, and I is chromatographic grade acetonitrile.

[0084] Figure 2 In the figure, 1 is a microfiltration unit, 2 is a low-temperature freezing tank, 3 is a first distillation tower, 4 is a second extractive distillation tower, 5 is a third distillation tower, 6 is an adsorption tank, and 7 is an ultrafiltration unit.

[0085] The following examples adopt Figure 1 The process and Figure 2 The adsorption tank is used as follows. Figure 3 and Figure 4 Adsorption canister shown.

[0086] The adsorption tank includes: a tank body and a material receiving frame; the tank body has a cylindrical cavity, and at least the upper and lower parts of the cavity wall are respectively provided with annular slide rails; the height and bottom diameter of the material receiving frame are both smaller than the tank body; a support rod is installed on the upper part of the material receiving frame, and the support rod can drive the material receiving frame to rotate under the drive of an external motor; the outer wall of the material receiving frame is provided with evenly distributed small holes, and the diameter of the small holes is preferably 1-2mm; 4 fixing buckles are installed at the quadrant points of the upper and lower circles of the material receiving frame, and the fixing buckles are embedded in the slide rails of the tank body, so that the material receiving frame can rotate in the tank body; the tank body is cylindrical; the bottom diameter of the tank body is preferably 400-700mm (500mm is used as an example in the embodiment) and the height is 800-1200mm (1000mm is used as an example in the embodiment); the material of the material receiving frame is polytetrafluoroethylene; the baffle is made of polytetrafluoroethylene; 2 baffles are evenly arranged in the vertical direction of the material receiving frame to divide the inner part of the frame into at least 3 spaces of exactly the same volume to load different adsorbents.

[0087] In the following examples, according to the present invention, Figure 1 and Figure 2 The method of the present invention comprises:

[0088] Step 1: adding alkali to the acetonitrile wastewater A for pretreatment, and then passing it into the microfiltration unit 1 to remove impurities including proteins, organic salts and solids in the wastewater through the filter membrane;

[0089] Step 2: Pass the acetonitrile wastewater after impurity removal into a low-temperature freezing tank 2, so that the wastewater is separated into a water or ice layer and an organic layer stream B;

[0090] Step 3: passing the organic layer into the first distillation tower 3 to remove the volatile light component stream C, and obtaining the acetonitrile distillate D in the bottom of the tower;

[0091] Step 4: passing the acetonitrile distillate and the extractant E into a second extractive distillation tower 4, and refining them by extractive distillation in the second extractive distillation tower to obtain high-purity acetonitrile F and a mixed solution of water and the extractant;

[0092] Step 5: Pass high-purity acetonitrile into the adsorption tank 6 for adsorption and impurity removal, thereby removing small molecular organic impurities, metal ions and trace moisture therein;

[0093] Step 6: The adsorbed high-purity acetonitrile is then passed through an ultrafiltration unit 7 to remove the particles therein to obtain chromatographic grade acetonitrile I;

[0094] Optionally, the mixture of water and extractant is separated by the third distillation tower 5, and the separated extractant stream H is returned to the second extractive distillation tower as the extractant raw material for extractive distillation, and the side discharge G of the third distillation tower is discharged.

[0095] In the present invention, holes are provided on the outer wall of the material receiving frame and between the baffles, thereby ensuring that the acetonitrile liquid is in full contact with the three adsorbents.

[0096] In the present invention, the strong acid cationic resin is, for example, one or more of 01×7 (732) strong acid styrene cation exchange resin, Amberlite IR120, D001 macroporous strong acid styrene cation exchange resin and Amberlite XAD-4 ion exchange macroporous adsorption resin. In the embodiments, 01×7 (732) strong acid styrene cation exchange resin is used as an example.

[0097] In the present invention, the weakly acidic cationic resin is, for example, one or more of D113 macroporous weakly acidic phenyl propylene-based cation exchange resin and D-85 macroporous propionic acid-based weakly acidic cation exchange resin. In the embodiments, D113 macroporous weakly acidic phenyl propylene-based cation exchange resin is used as an example.

[0098] In the following examples, activated carbon fiber was purchased from Nantong Senyou, strong acid cationic resin was purchased from Aladdin or Myrel, activated alumina was purchased from Sinopharm Group, weak acid cationic resin was purchased from Aladdin, and 3A molecular sieve was purchased from Sinopharm Group.

[0099] Example 1

[0100] Use Figure 1The process shown in the figure is to pre-treat acetonitrile wastewater (composition: 20% acetonitrile, 77% water, 1% protein, 1% other organic impurities, and 1% other solid impurities) by adding 3% potassium hydroxide by mass to the wastewater to control the pH at 7-8. The wastewater is then passed through a microfiltration device using a polypropylene membrane with a pore size of 0.5 μm. After microfiltration, the wastewater is passed into a low-temperature cooling tank at -35°C and allowed to stand for 8 hours. The organic layer is then passed into a first distillation tower. The top pressure of the first distillation tower is controlled at 0.75-0.8 atm, the feed position is at the 8th stage (the entire tower has 15 stages), the bottom temperature is controlled at 75-78°C, and the reflux ratio is 1. The acetonitrile distillate extracted from the bottom is passed into a second extractive distillation tower. The second extractive distillation tower is fed with acetonitrile distillate on the 14th tray. The ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) is introduced into the tower from the 8th tray, with the amount added being 25% of the mass of the acetonitrile distillate. The tower has 30 trays, with the top temperature controlled at 79-81°C, the bottom temperature at 123-125°C, and a reflux ratio of 1.5. The high-purity acetonitrile produced from the top is passed into an adsorption tank, and the bottom produced liquid is passed into the third distillation tower. The top pressure of the third distillation tower is controlled at 0.45-0.5 atm, and the feed position is on the 12th tray. The tower has 19 trays, with the top temperature controlled at 93-95°C, the bottom temperature at 145-150°C, and a reflux ratio of 0.5. The wastewater produced from the top can be directly discharged to the environment, and the ionic liquid produced from the bottom of the tower is returned to the ionic liquid feed port of the second distillation tower for further extractive distillation. The adsorbent loaded in the adsorption tank is calcium chloride, activated carbon fiber, and strong acid cationic resin (the mass ratio of the three is 1:1:1), with an average particle size of 6-8 mesh. The average residence time of high-purity acetonitrile in the adsorption tank is about 5 hours. After adsorption in the adsorption tank is completed, it is passed into the ultrafiltration equipment. The filter membrane material of the ultrafiltration equipment is cellulose carbonate with a pore size of 0.03 μm. After ultrafiltration is completed, chromatographic grade acetonitrile can be collected.

[0101] Example 2

[0102] Use Figure 1The process shown in the figure is to pre-treat acetonitrile wastewater (composition: 35% acetonitrile, 60% water, 2% protein, 1% other organic impurities, and 2% other solid impurities) by adding 2% sodium hydroxide by mass to the wastewater to control the pH at 6-8. The wastewater is then passed through a microfiltration device using a polycarbonate membrane with a pore size of 0.7 μm. After microfiltration, the wastewater is passed through a low-temperature cooling tank at -20°C and allowed to stand for 12 hours. The organic layer is then passed into a first distillation column. The top pressure of the first distillation column is controlled at 0.65-0.7 atm, and the feed point is at the 9th tray of the 16 trays. The bottom temperature is controlled at 76-79°C, and the reflux ratio is 1.5. The acetonitrile distillate removed from the bottom is passed into a second extractive distillation column. The feed tray for the acetonitrile distillate of the second extractive distillation tower is the 16th tray, and the ionic liquid enters the tower from the 10th tray. The addition amount is 30% of the mass of the acetonitrile distillate. The ionic liquid used is 1-pentyl imidazole bis (trifluoromethanesulfonyl imide salt). The whole tower has 34 trays, the top temperature is controlled at 81-83°C, the bottom temperature is controlled at 126-128°C, and the reflux ratio is 1.2; the high-purity acetonitrile produced from the top of the tower is passed into the adsorption tank, and the bottom produced liquid is passed into the third distillation tower. The top pressure of the third distillation tower is controlled at 0.4-0.45 atm, and the feed position is at the 13th tray. The entire tower has 21 trays. The top temperature is controlled at 98-100°C, the bottom temperature is controlled at 147-151°C, and the reflux ratio is 0.75. The wastewater produced from the top of the tower can be directly discharged into the environment, and the ionic liquid produced from the bottom of the tower is returned to the ionic liquid feed port of the second distillation tower to participate in the extractive distillation again. The adsorbent loaded in the adsorption tank is phosphorus pentoxide, activated alumina, and weak acid cationic resin (the mass ratio of the three is 1.5:2:1), with an average particle size of 7-10 mesh. The average residence time of high-purity acetonitrile in the adsorption tank is approximately 6 hours. After adsorption in the adsorption tank, it is passed into the ultrafiltration equipment. The filter membrane of the ultrafiltration equipment is made of polysulfone with a pore size of 0.02μm. After ultrafiltration, the chromatographic grade acetonitrile can be collected.

[0103] Example 3

[0104] Use Figure 1The process shown in the figure is to pre-treat acetonitrile wastewater (composition: 40% acetonitrile, 56% water, 2% protein, 1% other organic impurities, and 1% other solid impurities) by adding 4% sodium carbonate by weight to the wastewater to control the pH at 7-8. The wastewater is then passed through a microfiltration device using a silica membrane with a pore size of 0.6 μm. After microfiltration, the wastewater is passed through a low-temperature cooling tank at -25°C and allowed to stand for 10 hours. The organic layer is then passed into a first distillation tower. The top pressure of the first distillation tower is controlled at 0.7-0.75 atm, and the feed point is at the sixth stage of the 17-stage tower. The bottom temperature is controlled at 78-80°C, and the reflux ratio is 2. The acetonitrile distillate removed from the bottom is passed into a second extractive distillation tower. The second extractive distillation tower is fed with acetonitrile distillate on the 15th tray. The ionic liquid (1-propyl-4-methylpyridinium tetrafluoroborate) is introduced into the tower from the 8th tray, with the added amount being 35% of the mass of the acetonitrile distillate. The tower has 32 trays, the top temperature is controlled at 78-80°C, the bottom temperature is controlled at 121-122°C, and the reflux ratio is 2. The high-purity acetonitrile produced from the top is passed into an adsorption tank, and the bottom produced liquid is passed into the third distillation tower. The top pressure of the third distillation tower is controlled at 0.25-0.3 atm, the feed position is on the 10th tray, and the tower has 24 trays. The top temperature is controlled at 90-91°C, the bottom temperature is controlled at 140-143°C, and the reflux ratio is 0.8. The wastewater produced from the top can be directly discharged to the environment, and the ionic liquid produced from the bottom is returned to the ionic liquid feed port of the second distillation tower for further extractive distillation. The adsorbent loaded in the adsorption tank is 5A molecular sieve, activated carbon fiber, and strong acid cationic resin (the mass ratio of the three is 2:1.5:1), with an average particle size of 8-9 mesh. The average residence time of high-purity acetonitrile in the adsorption tank is about 7 hours. After adsorption in the adsorption tank is completed, it is passed into the ultrafiltration equipment. The filter membrane material of the ultrafiltration equipment is polyvinylidene fluoride with a pore size of 0.04μm. After ultrafiltration is completed, chromatographic grade acetonitrile can be collected.

[0105] Example 4

[0106] Use Figure 1The process shown in the figure is to pre-treat acetonitrile wastewater (composition: 10% acetonitrile, 85% water, 2% protein, 1% other organic impurities, and 2% other solid impurities) by adding 5% calcium carbonate by weight to the wastewater to control the pH at 7-8. The wastewater is then passed through a microfiltration device using a cellulose carbonate membrane with a pore size of 0.8 μm. After microfiltration, the wastewater is passed into a low-temperature cooling tank at -25°C and allowed to stand for 12 hours. The organic layer is then passed into a first distillation tower. The top pressure of the first distillation tower is controlled at 0.6-0.65 atm, the feed position is at the sixth stage of the 13-stage tower, the bottom temperature is controlled at 74-76°C, and the reflux ratio is 2.5. The acetonitrile distillate extracted from the bottom is passed into a second extractive distillation tower. The second extractive distillation tower is fed with acetonitrile distillate at tray 18. The ionic liquid (N-butylpyridinium bromide) is introduced into the tower at tray 9, with the amount added being 20% ​​of the mass of the acetonitrile distillate. The tower has 28 trays, with the top temperature controlled at 82-83°C, the bottom temperature at 135-137°C, and a reflux ratio of 1.8. The high-purity acetonitrile withdrawn from the top is passed into an adsorption tank, and the bottom liquid is passed into the third distillation tower. The top pressure of the third distillation tower is controlled at 0.35-0.4 atm, and the feed position is at tray 9. The tower has 24 trays, with the top temperature controlled at 97-99°C, the bottom temperature at 151-154°C, and a reflux ratio of 1.5. Wastewater withdrawn from the top can be discharged directly into the environment, while the ionic liquid withdrawn from the bottom of the tower is returned to the ionic liquid feed port of the second distillation tower for further extractive distillation. The adsorbent loaded in the adsorption tank is 3A molecular sieve, activated alumina, and weak acid cationic resin (the mass ratio of the three is 1.5:1.5:1), with an average particle size of 8-10 mesh. The average residence time of high-purity acetonitrile in the adsorption tank is about 6 hours. After adsorption in the adsorption tank is completed, it is passed into the ultrafiltration equipment. The filter membrane material of the ultrafiltration equipment is cellulose carbonate with a pore size of 0.02 μm. After ultrafiltration is completed, chromatographic grade acetonitrile can be collected.

[0107] Example 5

[0108] Use Figure 1The process shown in the figure is to pre-treat acetonitrile wastewater (composition: 20% acetonitrile, 78% water, 0.5% protein, 1% other organic impurities, and 0.5% other solid impurities) by adding 4% sodium carbonate by weight to the wastewater to control the pH at 6-8. The wastewater is then passed through a microfiltration device using a polycarbonate membrane with a pore size of 0.3 μm. After microfiltration, the wastewater is passed through a low-temperature cooling tank at -15°C and allowed to stand for 14 hours. The organic layer is then passed into a first distillation tower. The top pressure of the first distillation tower is controlled at 0.7-0.75 atm, the feed point is at the 8th stage (of the 18 stages), the bottom temperature is controlled at 72-74°C, and the reflux ratio is 1.6. The acetonitrile distillate removed from the bottom is passed into a second distillation tower. The second distillation tower's acetonitrile distillate feed tray is located on the 17th tray. The ionic liquid (1-pentyl imidazolium bis(trifluoromethanesulfonyl)imide) is introduced into the tower from the 6th tray, at a rate of 32% of the acetonitrile distillate's mass. The tower has 30 trays, with the top temperature controlled at 76-79°C, the bottom temperature at 127-130°C, and a reflux ratio of 2.2. High-purity acetonitrile withdrawn from the top is fed into an adsorption tank, and the bottom liquid is fed into the third distillation tower. The top pressure of the third distillation tower is controlled at 0.28-0.32 atm, and the feed tray is located on the 10th tray. The tower has 26 trays, with the top temperature controlled at 90-93°C, the bottom temperature at 147-149°C, and a reflux ratio of 1.75. Wastewater withdrawn from the top of the tower can be discharged directly to the environment, while the ionic liquid withdrawn from the bottom of the tower is returned to the ionic liquid feed port of the second distillation tower for further extractive distillation. The adsorbent loaded in the adsorption tank is phosphorus pentoxide, activated carbon fiber, and weak acid cationic resin (the mass ratio of the three is 1:1:1), with an average particle size of 7-9 mesh. The average residence time of high-purity acetonitrile in the adsorption tank is about 5 hours. After adsorption in the adsorption tank is completed, it is passed into the ultrafiltration equipment. The filter membrane material of the ultrafiltration equipment is cellulose carbonate with a pore size of 0.04 μm. After ultrafiltration is completed, chromatographic grade acetonitrile can be collected.

[0109] Example 6

[0110] Use Figure 1The process shown in the figure is to pre-treat acetonitrile wastewater (composition: 20% acetonitrile, 78% water, 0.5% protein, 1% other organic impurities, and 0.5% other solid impurities) by adding 3% potassium hydroxide by mass to the wastewater to control the pH at 6-8. The wastewater is then passed through a microfiltration device using a polypropylene membrane with a pore size of 0.2μm. After microfiltration, the wastewater is passed into a low-temperature cooling tank at -15°C and allowed to stand for 15 hours. The organic layer is then passed into a first distillation tower. The top pressure of the first distillation tower is controlled at 0.75-0.8atm, the feed position is at the sixth stage of the 16-stage tower, the bottom temperature is controlled at 73-75°C, and the reflux ratio is 2.4. The acetonitrile distillate extracted from the bottom is passed into a second extractive distillation tower. The second extractive distillation tower is fed with acetonitrile distillate on the 13th tray. The ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) is introduced into the tower from the 8th tray, with the amount added being 28% of the mass of the acetonitrile distillate. The tower has 28 trays, the top temperature is controlled at 82-84°C, the bottom temperature is controlled at 135-137°C, and the reflux ratio is 3. The high-purity acetonitrile produced from the top is passed to an adsorption tank, and the bottom produced liquid is passed to the third distillation tower. The top pressure of the third distillation tower is controlled at 0.45-0.48 atm, the feed position is on the 12th tray, and the tower has 20 trays. The top temperature is controlled at 102-104°C, the bottom temperature is controlled at 153-156°C, and the reflux ratio is 1.1. The wastewater produced from the top can be directly discharged to the environment, and the ionic liquid produced from the bottom is returned to the ionic liquid feed port of the second distillation tower for further extractive distillation. The adsorbent loaded in the adsorption tank is 3A molecular sieve, activated alumina, and strong acid cationic resin (the mass ratio of the three is 1.5:1.25:1), with an average particle size of 7-9 mesh. The average residence time of high-purity acetonitrile in the adsorption tank is about 7 hours. After adsorption in the adsorption tank is completed, it is passed into the ultrafiltration equipment. The filter membrane material of the ultrafiltration equipment is polyacrylonitrile with a pore size of 0.02 μm. After ultrafiltration is completed, chromatographic grade acetonitrile can be collected.

[0111] Example 7

[0112] Use Figure 1The process shown in the figure is to pre-treat acetonitrile wastewater (composition: 30% acetonitrile, 67% water, 0.5% protein, 1% other organic impurities, and 1.5% other solid impurities) by adding 3% calcium carbonate by weight to the wastewater to control the pH at 7-8. The wastewater is then passed through a microfiltration device using a silica membrane with a pore size of 0.3 μm. After microfiltration, the wastewater is passed through a low-temperature cooling tank at -18°C and allowed to stand for 15 hours. The organic layer is then passed into a first distillation tower. The top pressure of the first distillation tower is controlled at 0.6-0.65 atm, the feed point is at the 9th stage (a total of 19 stages), the bottom temperature is controlled at 74-76°C, and the reflux ratio is 2.4. The acetonitrile distillate removed from the bottom is passed into a second distillation tower. The second distillation tower's acetonitrile distillate feed tray is located on the 20th tray. The ionic liquid (1-pentyl imidazolium bis(trifluoromethanesulfonyl)imide) is introduced from the 8th tray, at a rate of 30% of the acetonitrile distillate's mass. The tower has 35 trays, with the top temperature controlled at 80-82°C, the bottom temperature at 135-138°C, and a reflux ratio of 1.4. The high-purity acetonitrile withdrawn from the top is fed into an adsorption tank, while the bottom liquid is fed into the third distillation tower. The top pressure of the third distillation tower is controlled at 0.4-0.43 atm, and the feed tray is located on the 12th tray. The tower has 28 trays, with the top temperature controlled at 96-99°C, the bottom temperature at 148-150°C, and a reflux ratio of 1.8. Wastewater withdrawn from the top of the tower can be discharged directly to the environment, while the ionic liquid withdrawn from the bottom of the tower is returned to the ionic liquid feed port of the second distillation tower for further extractive distillation. The adsorbent loaded in the adsorption tank is 5A molecular sieve, activated alumina, and strong acid cationic resin (the mass ratio of the three is 1:1.5:1), with an average particle size of 8-10 mesh. The average residence time of high-purity acetonitrile in the adsorption tank is about 6 hours. After adsorption in the adsorption tank is completed, it is passed into the ultrafiltration equipment. The filter membrane material of the ultrafiltration equipment is polysulfone with a pore size of 0.04 μm. After ultrafiltration is completed, chromatographic grade acetonitrile can be collected.

[0113] Example 8

[0114] Use Figure 1The process shown in the figure is to pre-treat acetonitrile wastewater (composition: 22% acetonitrile, 76% water, 0.6% protein, 1% other organic impurities, and 0.4% other solid impurities) by adding 2% potassium hydroxide by mass to the wastewater to control the pH at 6-7. The wastewater is then passed through a microfiltration device using a polypropylene membrane with a pore size of 0.2μm. After microfiltration, the wastewater is passed into a low-temperature cooling tank at -28°C and allowed to stand for 10 hours. The organic layer is then directly passed into the first distillation tower. The top pressure of the first distillation tower is controlled at 0.6-0.65atm, the feed position is at the 8th stage of the 14-stage tower, the bottom temperature is controlled at 75-78°C, and the reflux ratio is 2. The acetonitrile distillate extracted from the bottom is passed into the second distillation tower. The second distillation tower's acetonitrile distillate feed tray is located at tray 35. The ionic liquid (1-propyl-4-methylpyridinium tetrafluoroborate) is introduced into the tower at tray 9, at a rate of 28% of the acetonitrile distillate's mass. The tower has 40 trays, with the top temperature controlled at 78-80°C, the bottom temperature at 133-136°C, and a reflux ratio of 2. The high-purity acetonitrile withdrawn from the top is fed into an adsorption tank, and the bottom liquid is fed into the third distillation tower. The top pressure of the third distillation tower is controlled at 0.35-0.38 atm, and the feed point is located at tray 14. The tower has 26 trays, with the top temperature controlled at 93-95°C, the bottom temperature at 142-145°C, and a reflux ratio of 1.5. Wastewater withdrawn from the top can be discharged directly into the environment, while the ionic liquid withdrawn from the bottom of the tower is returned to the ionic liquid feed port of the second distillation tower for further extractive distillation. The adsorbent loaded in the adsorption tank is 3A molecular sieve, activated alumina, and weak acid cationic resin (the mass ratio of the three is 2:1.5:1), with an average particle size of 6-8 mesh. The average residence time of high-purity acetonitrile in the adsorption tank is about 7 hours. After adsorption in the adsorption tank is completed, it is passed into the ultrafiltration equipment. The filter membrane material of the ultrafiltration equipment is polyacrylonitrile with a pore size of 0.04 μm. After ultrafiltration is completed, chromatographic grade acetonitrile can be collected.

[0115] Comparative Example 1 (without adsorption tank)

[0116] Use Figure 1The process shown in the figure is to pre-treat acetonitrile wastewater (composition: 20% acetonitrile, 77% water, 1% protein, 1% other organic impurities, and 1% other solid impurities) by adding 3% potassium hydroxide by mass to the wastewater to control the pH at 7-8. The wastewater is then passed through a microfiltration device using a polypropylene membrane with a pore size of 0.5 μm. After microfiltration, the wastewater is passed into a low-temperature cooling tank at -35°C and allowed to stand for 8 hours. The organic layer is then passed into a first distillation tower. The top pressure of the first distillation tower is controlled at 0.75-0.8 atm, the feed position is at the 8th stage (the entire tower has 15 stages), the bottom temperature is controlled at 75-78°C, and the reflux ratio is 1. The acetonitrile distillate extracted from the bottom is passed into a second extractive distillation tower. The second extractive distillation tower is fed with acetonitrile distillate on the 14th tray. The ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) is introduced into the tower from the 8th tray, with the amount added being 25% of the mass of the acetonitrile distillate. The tower has 30 trays, with the top temperature controlled at 79-81°C, the bottom temperature at 123-125°C, and a reflux ratio of 1.5. The high-purity acetonitrile produced from the top is directly fed into an ultrafiltration device, and the bottom produced liquid is fed into the third distillation tower. The top pressure of the third distillation tower is controlled at 0.45-0.5 atm, and the feed point is on the 12th tray. The tower has 19 trays, with the top temperature controlled at 93-95°C, the bottom temperature at 145-150°C, and a reflux ratio of 0.5. Wastewater produced from the top can be discharged directly to the environment, while the ionic liquid produced from the bottom of the tower is returned to the ionic liquid feed port of the second distillation tower for further extractive distillation. The filter membrane of the ultrafiltration equipment is made of cellulose carbonate with a pore size of 0.03 μm. After ultrafiltration is completed, acetonitrile can be collected.

[0117] Comparative Example 2 (using ordinary adsorption column)

[0118] Use Figure 1The process shown in the figure is to pre-treat acetonitrile wastewater (composition: 20% acetonitrile, 77% water, 1% protein, 1% other organic impurities, and 1% other solid impurities) by adding 3% potassium hydroxide by mass to the wastewater to control the pH at 7-8. The wastewater is then passed through a microfiltration device using a polypropylene membrane with a pore size of 0.5 μm. After microfiltration, the wastewater is passed into a low-temperature cooling tank at -35°C and allowed to stand for 8 hours. The organic layer is then passed into a first distillation tower. The top pressure of the first distillation tower is controlled at 0.75-0.8 atm, the feed position is at the 8th stage (the entire tower has 15 stages), the bottom temperature is controlled at 75-78°C, and the reflux ratio is 1. The acetonitrile distillate extracted from the bottom is passed into a second extractive distillation tower. The second extractive distillation tower is fed with acetonitrile distillate on the 14th tray. The ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) is introduced into the tower from the 8th tray, with the amount added being 25% of the mass of the acetonitrile distillate. The tower has 30 trays, with the top temperature controlled at 79-81°C, the bottom temperature at 123-125°C, and a reflux ratio of 1.5. The high-purity acetonitrile produced from the top is fed into a conventional adsorption column, and the bottom produced liquid is fed into the third distillation tower. The top pressure of the third distillation tower is controlled at 0.45-0.5 atm, and the feed point is on the 12th tray. The tower has 19 trays, with the top temperature controlled at 93-95°C, the bottom temperature at 145-150°C, and a reflux ratio of 0.5. Wastewater produced from the top can be discharged directly to the environment, while the ionic liquid produced from the bottom of the tower is returned to the ionic liquid feed port of the second distillation tower for further extractive distillation. The adsorbents loaded in ordinary adsorption columns are calcium chloride, activated carbon fiber and strong acid cationic resin with an average particle size of 6-8 mesh. High-purity acetonitrile flows through the adsorption column from top to bottom at a certain rate. After adsorption in the adsorption column, it is passed into the ultrafiltration equipment. The filter membrane of the ultrafiltration equipment is made of cellulose carbonate with a pore size of 0.03μm. After ultrafiltration is completed, acetonitrile can be collected.

[0119] Table 1

[0120]

[0121]

[0122] Table 2

[0123]

[0124] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing chromatographic grade acetonitrile using acetonitrile wastewater, characterized in that: The method includes: Step 1: adding alkali to the acetonitrile wastewater for pretreatment, and then passing the wastewater into a microfiltration unit to remove impurities including protein, organic salts and solids in the wastewater through the filter membrane; based on 100 weight, the acetonitrile wastewater contains: 10-40% acetonitrile, 55-85% water, 1-2% protein, 1% other organic impurities, and 1-2% other solid impurities; Step 2: passing the acetonitrile wastewater after impurity removal into a low-temperature freezing unit to separate the wastewater into a water or ice layer and an organic layer; Step 3: passing the organic layer into the first distillation tower to remove the volatile light components, and obtaining acetonitrile distillate in the bottom of the tower; Step 4: passing the acetonitrile distillate and the extractant into a second extractive distillation tower, and refining the acetonitrile by extractive distillation in the second extractive distillation tower to obtain high-purity acetonitrile and a mixed solution of water and the extractant; Step 5: Pass high-purity acetonitrile into the adsorption tank for adsorption and impurity removal to remove small molecular organic impurities, metal ions and trace moisture; Step 6: The adsorbed high-purity acetonitrile is then passed through an ultrafiltration unit to remove the particles therein to obtain chromatographic grade acetonitrile; The mixed liquid of water and extractant is separated by the third distillation tower, and the extractant is returned to the second extractive distillation tower as the extractant raw material for extractive distillation.

2. The method according to claim 1, wherein The pH of the acetonitrile wastewater is 4-6; The acetonitrile wastewater is acetonitrile wastewater generated by the biopharmaceutical industry.

3. The method according to claim 1, wherein In step one, The alkali is one or more of sodium hydroxide, sodium carbonate, calcium carbonate and potassium hydroxide; The amount of alkali added is 2-5% of the mass of acetonitrile wastewater; The pH range for alkaline treatment is 6-8; The filter membrane of the microfiltration unit is made of cellulose carbonate, polypropylene, polycarbonate or silica; The pore size of the filter membrane of the microfiltration unit is 0.1-1 μm; In step 2, The low-temperature freezing unit is a low-temperature freezing tank; The temperature of the low-temperature freezing tank is set at -35°C to -15°C, and the acetonitrile wastewater is allowed to stand for 8-16 hours; In step three, The first distillation tower is operated by vacuum distillation, the top pressure is controlled at 0.6-0.8 atm, the feed position is at the 5th to 9th tray, the number of trays is 12-20 trays, the bottom temperature is 70-80°C, and the reflux ratio is 0.5-3; In step four, The second extractive distillation tower is an atmospheric distillation tower with 25-40 plates, a top temperature of 75-85°C, a bottom temperature of 120-140°C, and a reflux ratio of 1-4; The acetonitrile distillate enters the tower from the 12th to 20th plates, and the extractant is added from the 6th to 10th plates. The feed amount of the extractant is 20-40% by weight of the acetonitrile distillate. The mass fraction of high-purity acetonitrile extracted from the top of the tower is greater than 99%; The extractant is one or more of 1-propyl-4-methylpyridinium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-propyl-2,3-methylpyridinium tetrafluoroborate, 1-pentyl imidazolium bis(trifluoromethanesulfonyl)imide and N-butylpyridinium bromide.

4. The method according to claim 1, wherein The third distillation tower is a vacuum distillation tower, the tower body pressure is controlled at 0.2-0.5 atm, the number of tower plates is 18-30, the temperature of the distillation tower top is 90-105°C, the tower bottom temperature is 140-160°C, and the reflux ratio is 0.5-2; the mixed liquid of water and extractant enters the tower from the 8th to 15th plates, the mass fraction of water extracted from the tower top is greater than 99% and is directly discharged to the outside, and the extractant with a water content of 1-5% by weight in the tower bottom is returned to the second extractive distillation tower for use as the extractant.

5. The method according to claim 1, wherein In step five, The adsorbent is selected from one or more of calcium chloride, phosphorus pentoxide, 3A molecular sieve, 5A molecular sieve, activated carbon fiber, activated alumina, strong acid cationic resin and weak acid anionic resin. The particle size of the adsorbent is 5-10 mesh; The average residence time of high-purity acetonitrile in the adsorption tank is 4-8h; The material receiving frame of the adsorption tank is provided with three spaces, which are filled with three different adsorbents, including: a first adsorbent selected from 3A molecular sieve and / or 5A molecular sieve and / or calcium chloride and / or phosphorus pentoxide; a second adsorbent selected from one or more of 3A molecular sieve, 5A molecular sieve, activated carbon fiber and activated alumina; a third adsorbent selected from strong acid cationic resin and / or weak acid cationic resin, and the usage ratio of the three is 1-2:1-2:1-2.

6. The method according to claim 1, wherein The filter membrane of the ultrafiltration unit is made of polyvinyl chloride, polyacrylonitrile, polysulfone, polyvinylidene fluoride or cellulose carbonate; The pore size of the filter membrane of the ultrafiltration unit is 0.02-0.05 μm.

7. The acetonitrile obtained by the method according to any one of claims 1 to 6, wherein the acetonitrile is chromatographic grade, the mass percentage of acetonitrile is ≥99.95%, and the moisture content is less than 300 ppm.

8. The method according to claim 1, wherein The adsorption tank includes a tank body and a material receiving frame; the tank body has a cavity with a circular cross-section, and an annular slide rail is respectively provided on at least the upper and lower parts of the cavity wall; the material receiving frame has a circular cross-section and is used to load the adsorbent, and the height and corresponding cross-sectional diameter of the material receiving frame are both smaller than the tank body, and at least two baffles are vertically provided inside the material receiving frame, dividing the interior of the material receiving frame into at least three spaces for loading different adsorbents, and small holes are opened on the outer wall of the material receiving frame so that the liquid phase can pass freely but the adsorbent cannot pass through; the material receiving frame is installed on the annular slide rail by a fixed sliding device, so that the material receiving frame can rotate inside the tank body.

9. The method according to claim 8, wherein The tank body has a cylindrical cavity; the material receiving frame is cylindrical; The upper part of the material receiving frame is provided with a support rod, which can drive the material receiving frame to rotate under the drive of an external motor; The outer wall of the material receiving frame is provided with evenly distributed small holes; There are 4 fixing buckles installed on the quadrant points of the upper and lower circles of the material receiving frame. The fixing buckles are embedded in the slide rails of the tank body, so that the material receiving frame can rotate in the tank body. The tank body is the main part of the adsorption tank; The material of the material receiving frame is polytetrafluoroethylene; The baffle is made of polytetrafluoroethylene; The baffles are evenly arranged in the vertical direction of the material receiving frame to divide the frame into at least three spaces with completely identical volumes.

10. The method according to claim 9, wherein: The diameter of the small hole is 1-2mm; The tank body is cylindrical.

11. The method according to claim 10, wherein: The bottom diameter of the tank is 400-700mm and the height is 800-1200mm.

12. A device for preparing chromatographic grade acetonitrile from acetonitrile wastewater using the method according to any one of claims 8 to 11, characterized in that: The device comprises: a microfiltration unit, a low-temperature freezing unit, a first distillation tower, a second extractive distillation tower, optionally a third distillation tower, an adsorption tank and an ultrafiltration unit; wherein, the outlet of the microfiltration unit is connected to the inlet of the low-temperature freezing unit; the organic layer outlet of the low-temperature freezing unit is connected to the feeding port of the first distillation tower; the top outlet of the first distillation tower is connected to the outside, and the kettle discharge port of the first distillation tower is connected to the acetonitrile distillate feeding port of the second extractive distillation tower; the top outlet of the second extractive distillation tower is connected to the inlet of the adsorption tank, and the kettle discharge port of the second extractive distillation tower is connected to the feeding port of the third distillation tower; the top outlet of the third distillation tower is connected to the outside, and the kettle discharge port of the third distillation tower is connected to the extractant feeding port of the second extractive distillation tower; the adsorption tank discharge port is connected to the inlet of the ultrafiltration unit, and the outlet of the ultrafiltration unit discharges chromatographic-grade acetonitrile.

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