Separation method of toluene-ethanol-water three-phase azeotrope

Abstract

The embodiment of the invention discloses a separation method of a toluene-ethanol-water three-phase azeotrope. A specific embodiment of the method comprises the following steps: carrying out separation treatment on a toluene-ethanol-water three-phase azeotrope through a preferential permeable membrane assembly to obtain a primary treatment material comprising a retentate material and vapor product water collected in a mixing tank; condensing the vapor product water to obtain product water; the retentate material is conveyed to a rectifying tower, a rectified material is obtained, and the rectified material comprises a liquid azeotrope and a toluene product; treating the liquid azeotrope through a preferential toluene permeable membrane assembly to obtain a secondary treatment material comprising an ethanol product and toluene-containing steam; condensing the toluene-containing steam to obtain a liquid toluene-containing material; conveying a liquid toluene-containing material to a mixing tank, and treating along with a retentate material; and extracting a product water, a toluene product and an ethanol product. Through the coupling of the two membrane assemblies and the rectifying tower, the separation process flow can be simplified by the implementation mode.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the field of chemical separation technology, in particular to a separation method of toluene-ethanol-water ternary azeotrope. BACKGROUND

[0002] Toluene and ethanol are widely used basic chemical raw materials and common solvents in organic chemistry, synthetic pharmaceuticals and fine chemical industry. The mixture of toluene and ethanol, especially the toluene-ethanol-water ternary azeotrope formed in the presence of water, is ubiquitous in many industrial processes. At present, the toluene-ethanol-water ternary azeotrope is separated by the method of extractive distillation.

[0003] However, when separating the toluene-ethanol-water ternary azeotrope by the above method, in addition to the separation of the ternary azeotrope, the steps of selection, use and recovery of the extractant are additionally required, and the technical problem of high complexity of the process flow often exists.

[0004] The above information disclosed in this Background section is only for the purpose of enhancing the understanding of the background of the present disclosure and, as such, it can contain information that does not form the prior art that is already known to those of ordinary skill in the art in this country. SUMMARY

[0005] The summary section of the present disclosure is provided in a brief form to introduce the concepts that will be described in detail in the specific embodiments section. The summary section of the present disclosure is not intended to identify key or essential features of the claimed technical solutions nor is it intended to be used to limit the scope of the claimed technical solutions.

[0006] Some embodiments of the present disclosure propose a separation method of toluene-ethanol-water ternary azeotrope to solve one or more of the technical problems mentioned in the background section.

[0007] Some embodiments of the present disclosure provide a method for separating a toluene-ethanol-water ternary azeotrope, the method comprising: separating the toluene-ethanol-water ternary azeotrope by a preferential water-permeable membrane assembly to obtain a first treated material, wherein the first treated material comprises a retentate and gaseous product water, and the retentate is collected in a mixing tank; condensing the gaseous product water by a condenser to obtain product water; feeding the retentate from the mixing tank to a rectification column; rectifying the retentate by the rectification column to obtain a rectified material, wherein the rectified material comprises a liquid azeotrope and a toluene product; permeation vaporizing the liquid azeotrope by a preferential toluene-permeable membrane assembly to obtain a second treated material, wherein the second treated material comprises an ethanol product and toluene-containing vapor; condensing the toluene-containing vapor to obtain a liquid toluene-containing material; feeding the liquid toluene-containing material to the mixing tank by a liquid transfer pump to be treated together with the retentate; and collecting the product water, the toluene product and the ethanol product.

[0008] Optionally, the separating the toluene-ethanol-water ternary azeotrope by the preferential water-permeable membrane assembly to obtain the first treated material comprises: heating the toluene-ethanol-water ternary azeotrope to a preset temperature to obtain a heated azeotrope, wherein the heated azeotrope is located at a retentate side of the preferential water-permeable membrane assembly; and controlling a gas pressure at a permeation side of the preferential water-permeable membrane assembly to be less than a gas pressure at the retentate side to obtain the first treated material.

[0009] Optionally, the feeding the retentate from the mixing tank to the rectification column comprises: feeding the retentate from the retentate side of the preferential water-permeable membrane assembly to the mixing tank; preheating the retentate in the mixing tank to obtain a preheated retentate; and feeding the preheated retentate to the rectification column.

[0010] Optionally, the rectifying the retentate by the rectification column to obtain the rectified material comprises: heating the retentate to obtain gaseous azeotrope and the toluene product; and condensing the gaseous azeotrope to obtain the liquid azeotrope.

[0011] Optionally, the permeation vaporizing the liquid azeotrope by the preferential toluene-permeable membrane assembly to obtain the second treated material comprises: heating the liquid azeotrope to 30-50°C to obtain a preheated azeotrope; controlling a gas pressure at a permeation side of the preferential toluene-permeable membrane assembly to be less than a saturated vapor pressure of toluene at 30-50°C; and feeding the preheated azeotrope to the preferential toluene-permeable membrane assembly to obtain the second treated material.

[0012] Optionally, before the distillate material is obtained by distilling the retentate material through the distillation column, the method further comprises: controlling the number of plates of the distillation column to be 10-30, the bottom temperature to be 110-120℃, and the reflux ratio to be 0.5-2.

[0013] Optionally, the controlling the gas pressure on the permeate side of the preferential water-permeable membrane assembly to be less than the gas pressure on the retentate side to obtain the first-stage treated material comprises: controlling the gas pressure on the retentate side of the preferential water-permeable membrane assembly to be 0.05-0.3 MPaG; and controlling the gas pressure on the permeate side of the preferential water-permeable membrane assembly to be 0.5-10 kPaA.

[0014] Optionally, the controlling the gas pressure on the permeate side of the preferential toluene-permeable membrane assembly to be less than the saturated vapor pressure of toluene at 30-50℃ comprises: controlling the gas pressure on the permeate side of the preferential toluene-permeable membrane assembly to be 0.5-10 kPaA.

[0015] Optionally, before the secondary treated material is obtained by permeation vaporization of the liquid azeotrope through the preferential toluene-permeable membrane assembly, the method further comprises: dissolving methyl triethoxysilane in n-heptane to obtain a mixed solution; dispersing SBA-15 molecular sieve into the mixed solution to obtain a mixture; heating the mixture to reflux at 100℃ under a nitrogen atmosphere for 12-24 hours to obtain a reaction product, wherein the mixture is stirred during the oil bath process; washing the reaction product with n-heptane to obtain a washed reaction product; drying the washed reaction product to obtain a modified molecular sieve; dissolving vinyl-terminated polydimethylsiloxane in n-heptane to obtain a polymer solution, wherein the mass of n-heptane is 8-10 times that of the vinyl-terminated polydimethylsiloxane; dispersing the modified molecular sieve into the polymer solution to obtain a uniform mixed solution; adding tetraethyl orthosilicate and dibutyltin dilaurate to the uniform mixed solution under stirring to obtain a primary casting solution; stirring the primary casting solution at an increased stirring speed for a preset time to obtain a secondary casting solution; degassing the secondary casting solution to obtain a finished casting solution; coating the finished casting solution on a support membrane to obtain a coated membrane; drying the coated membrane at room temperature in a vacuum environment for 12 hours to obtain a primary solidified membrane; drying the primary solidified membrane at 120℃ in a vacuum environment for 4 hours to obtain a secondary solidified membrane; washing the secondary solidified membrane with deionized water after the secondary solidified membrane cools to room temperature to obtain a washed solidified membrane; and air-drying the washed solidified membrane at room temperature to obtain the preferential toluene-permeable membrane.

[0016] Some embodiments of the present disclosure provide a separation method of toluene-ethanol-water ternary azeotrope, which can simplify the process flow of separating toluene-ethanol-water ternary azeotrope. Specifically, the reason why most separation processes of toluene-ethanol-water ternary azeotrope are complicated is that the current common way of extractive distillation is used to separate toluene-ethanol-water ternary azeotrope. When separating toluene-ethanol-water ternary azeotrope by using the above-mentioned method, in addition to the separation of ternary azeotrope, the selection, use, and recovery of the extractant are additionally required. Based on this, some embodiments of the present disclosure provide a separation method of toluene-ethanol-water ternary azeotrope, which comprises: separating toluene-ethanol-water ternary azeotrope by using a preferential water-permeable membrane assembly to obtain a first treatment material, wherein the first treatment material comprises a retentate and gaseous product water, and the retentate is collected in a mixing tank; condensing the gaseous product water by using a condenser to obtain product water; conveying the retentate from the mixing tank to a rectifying column; rectifying the retentate by using the rectifying column to obtain a rectified material, wherein the rectified material comprises liquid azeotrope and toluene product; permeation vaporizing the liquid azeotrope by using a preferential toluene-permeable membrane assembly to obtain a second treatment material, wherein the second treatment material comprises ethanol product and toluene-containing steam; condensing the toluene-containing steam to obtain liquid toluene-containing material; conveying the liquid toluene-containing material into the mixing tank by using a liquid transfer pump to be treated together with the retentate; and collecting the product water, the toluene product, and the ethanol product, respectively. By combining the membrane separation technology and the rectification technology, a double-membrane assembly separation system without extractant is formed. Thus, the process flow of separating toluene-ethanol-water ternary azeotrope can be simplified. BRIEF DESCRIPTION OF DRAWINGS

[0017] The above and other features, aspects, and advantages of the present disclosure will become more apparent with reference to the following detailed description when taken in conjunction with the accompanying drawings. Throughout the drawings, the same or like reference numerals are used to represent the same or similar elements. It is to be understood that the drawings are schematically showing the elements and elements are not necessarily drawn to scale.

[0018] Figure 1 is a flowchart of some embodiments of the separation method of toluene-ethanol-water ternary azeotrope according to the present disclosure. DETAILED DESCRIPTION

[0019] Embodiments of the present disclosure will be described below in greater detail with reference to the accompanying drawings. While certain embodiments of the present disclosure are shown in the drawings, it is understood that the present disclosure can be embodied in various forms and should not be interpreted as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be more thoroughly and completely understood. It should be understood that the drawings and embodiments of the present disclosure are only for illustrative purposes and are not intended to limit the scope of protection of the present disclosure.

[0020] It should also be noted that, for ease of description, only the parts related to the present application are shown in the drawings. The embodiments in the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0021] It should be noted that the terms "first", "second", and the like mentioned in the present disclosure are only used to distinguish different devices, modules or units, and are not intended to limit the order or interdependence of the functions performed by these devices, modules or units.

[0022] It should be noted that the terms "one", "multiple" mentioned in the present disclosure are illustrative and not restrictive, and those skilled in the art should understand that unless otherwise explicitly stated in the context, it should be understood as "one or more".

[0023] The names of the messages or information exchanged between the devices in the embodiments of the present disclosure are only for illustrative purposes, and are not intended to limit the scope of the messages or information.

[0024] The present disclosure will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0025] Figure 1 Flow 100 of some embodiments of a separation method of a toluene-ethanol-water ternary azeotrope according to the present disclosure is shown. The separation method of the toluene-ethanol-water ternary azeotrope includes the following steps:

[0026] Step 101, separating the toluene-ethanol-water ternary azeotrope by a water-preferential membrane module to obtain a first treated material.

[0027] In some embodiments, the toluene-ethanol-water ternary azeotrope can be separated by a preferential water permeable membrane assembly to obtain a first treated material. The preferential water permeable membrane assembly can include a preferential water permeable membrane. The preferential water permeable membrane can be a pervaporation membrane that allows water to permeate preferentially. The preferential water permeable membrane assembly can have a cylindrical stainless steel pressure vessel. The preferential water permeable membrane assembly can include a preferential water permeable membrane installed inside the pressure vessel. The first treated material can include a retentate and vapor product water, and the retentate can be collected in a mixing tank. The mixing tank can be a cylindrical stainless steel storage tank that can be used to store materials that do not pass through the preferential water permeable membrane assembly and to collect recycled materials that can be used in subsequent separation processes.

[0028] In some optional implementations of some embodiments, the first treated material can be obtained by the following steps:

[0029] In a first step, the toluene-ethanol-water ternary azeotrope can be heated to a predetermined temperature to obtain a heated azeotrope. The heated azeotrope can be on the retentate side of the preferential water permeable membrane assembly. The predetermined temperature can be adjusted according to the type of preferential water permeable membrane. For example, if the preferential water permeable membrane is a polyvinyl alcohol film, the predetermined temperature can be determined to be greater than or equal to 30°C. When the temperature is greater than or equal to 30°C, the polyvinyl alcohol film has good water permeability. This is because the polyvinyl alcohol molecular chain contains a large number of hydroxyl groups, and hydrogen bonds form certain crystalline and amorphous regions between molecules. When the temperature is above 30°C, as the temperature increases, the molecular thermal motion increases, the hydrogen bond interaction weakens, the proportion of amorphous regions increases, the molecular chain gap expands, and water molecules are more likely to pass through the film by diffusion. In practice, the toluene-ethanol-water ternary azeotrope can be heated to the predetermined temperature by an electric heater to obtain the heated azeotrope.

[0030] In a second step, the pressure on the permeate side of the preferential water permeable membrane assembly can be controlled to be less than the pressure on the retentate side to obtain a first treated material. The first treated material can include a retentate and vapor product water. In practice, a vacuum pump can be connected to the permeate side of the preferential water permeable membrane assembly to draw the pressure on the permeate side to be less than the pressure on the retentate side to drive the heated azeotrope to the permeate side of the membrane. Because the preferential water permeable membrane assembly has the ability to allow water to permeate preferentially, the water in the heated azeotrope can be separated. When the water permeates the preferential water permeable membrane assembly, the toluene-ethanol azeotrope remains on the retentate side, which is the retentate. The toluene-ethanol azeotrope on the retentate side can be transported to the mixing tank for the next step. When the pressure on the permeate side is less than the saturated vapor pressure of water at the predetermined temperature, even if the toluene-ethanol-water ternary azeotrope enters the preferential water permeable membrane assembly in a liquid state, the water obtained on the permeate side will be in a vapor state, which is the vapor product water.

[0031] Optionally, the preferential water permeable membrane in the preferential water permeable membrane assembly described above can be prepared by the following steps:

[0032] In the first step, polyvinyl alcohol powder is added to deionized water to obtain a solid-liquid mixture. The amount of polyvinyl alcohol powder is not specifically limited here, as long as the mass fraction of the polyvinyl alcohol solution is 5-8%.

[0033] In the second step, the solid-liquid mixture is stirred at a constant temperature of 85±5℃ in a water bath at a speed of 200-400rpm for 2-3 hours until complete dissolution, to obtain a polyvinyl alcohol solution. The mass fraction of the polyvinyl alcohol solution can be 5-8%. In practice, the solid-liquid mixture can be placed in a constant temperature water bath with an electric stirrer to stir the solid-liquid mixture, and the temperature reading of the real-time thermometer is observed to determine whether it is within the target temperature range. The target temperature range can improve the dissolution efficiency and prevent molecular chain degradation due to high temperature. The stirring time can be adjusted flexibly according to the actual situation, as long as the polyvinyl alcohol powder is completely dissolved.

[0034] In the third step, a non-ionic defoaming agent with a mass fraction of 0.1-0.5% is added to the polyvinyl alcohol solution to obtain a pre-defoaming solution. The non-ionic defoaming agent can be polyethylene glycol ester. Polyethylene glycol ester has good compatibility with polyvinyl alcohol and has both defoaming and thickening effects, which can reduce the structural defects of the membrane. In practice, a non-ionic defoaming agent with a mass fraction of 0.1-0.5% can be added to the polyvinyl alcohol solution using a pipette to obtain a pre-defoaming solution.

[0035] In the fourth step, the pre-defoaming solution is stirred for 0.5 hours to obtain a defoaming casting solution. Although the pre-defoaming solution has already added a defoaming agent, the defoaming agent has not fully dispersed. In practice, to make the defoaming agent better play a defoaming role, the pre-defoaming solution can be stirred at a speed of 100-200rpm for 0.5 hours using a stirrer to obtain a defoaming casting solution.

[0036] In the fifth step, the defoaming casting solution is left to stand for 12 hours to remove bubbles, to obtain a casting solution. Although the defoaming casting solution has removed large bubbles and foam layers through the treatment of the defoaming agent, it still contains bubbles generated during the stirring process. In practice, the defoaming casting solution can be transferred to a wide-mouth container and sealed for 12 hours to allow the bubbles to naturally float to the surface and be removed, ensuring the purity of the casting solution and reducing the possibility of pinholes in the film to some extent.

[0037] In the sixth step, the base membrane is immersed in an ethanol aqueous solution with a mass fraction of 30% and ultrasonically cleaned for 20 minutes to obtain a cleaned base membrane. The base membrane can be a polyacrylonitrile (PAN) ultrafiltration membrane or a polysulfone (PSf) ultrafiltration membrane. The base membrane can serve as a carrier for coating the casting liquid and play a supporting role. In practice, the base membrane can be immersed in an ethanol aqueous solution with a mass fraction of 30%. The ethanol aqueous solution soaked with the base membrane is then placed in an ultrasonic cleaning machine. The base membrane is ultrasonically cleaned for 20 minutes to obtain a cleaned base membrane. This operation can utilize the degreasing ability of ethanol and the cavitation effect of ultrasound to remove organic matter, dust and other impurities on the surface of the base membrane, thereby improving the adhesion between the base membrane and the casting liquid. The use of a 30% ethanol aqueous solution can give a balance between cleaning effect and economy. Too high a concentration can easily cause the base membrane to swell, while too low a concentration will result in insufficient cleaning ability.

[0038] In the seventh step, the cleaned basement membrane is rinsed with deionized water until the outlet water conductivity is less than 5μS / cm, thereby obtaining a rinsed basement membrane. Ethanol may remain on the surface of the cleaned basement membrane, and ions may be dissolved during the ultrasonic cleaning process. In practice, the cleaned basement membrane can be repeatedly rinsed with deionized water until the conductivity of the rinse water is less than 5μS / cm. This operation can improve the purity of the basement membrane surface and reduce the possibility of impurities affecting membrane performance.

[0039] In the eighth step, the rinsed basement membrane is dried for two hours to obtain an activated basement membrane. In practice, the rinsed basement membrane can be placed in a forced-air drying oven and dried at 40-60°C for two hours to obtain an activated basement membrane. This operation removes moisture from the surface of the basement membrane and simultaneously activates the hydroxyl groups on the surface of the basement membrane, enhancing compatibility and adhesion with the casting solution. The temperature range of 40-60°C allows for rapid drying while reducing the possibility of deformation or oxidation of the basement membrane caused by high temperatures.

[0040] In the ninth step, the silica nanoparticles are dispersed in a deionized water solution containing 10% polyvinyl alcohol by weight to obtain a dispersion. The silica nanoparticles may comprise hydrophilic silica nanoparticles having a particle size of 20 to 50 nm. In practice, the silica nanoparticles can be added to a deionized water solution containing 10% polyvinyl alcohol by weight and dispersed using an ultrasonic disperser for 30 minutes until uniform. The amount of silica nanoparticles used can be 1 to 3% of the mass of the polyvinyl alcohol powder added in the first step.

[0041] In the tenth step, the dispersion is added to the casting solution to obtain a composite casting solution. The silica nanoparticles in the dispersion can improve the mechanical strength, hydrophilicity, and water permeability of the membrane. In practice, the dispersion can be slowly added to the casting solution and stirred at 100-200 rpm for 1-2 hours until uniformly mixed. There is no specific requirement for stirring time; uniform stirring is sufficient.

[0042] The tenth step is to coat the composite casting solution on the surface of the activated base film using an automatic film coater to obtain a wet coated film. The automatic film coater can be a device that spreads the slurry evenly on the surface of a substrate such as a metal foil, glass, plastic film, etc. by mechanical movement of the doctor blade to form a thin film. In practice, the doctor blade gap of the automatic film coater can be set to 100 ± 10 μm, and the coating speed can be controlled at 2-5 cm / s to obtain a wet coated film.

[0043] The twelfth step is to place the wet coated film in an environment with a relative humidity of 60 ± 5% and a temperature of 25 ± 1°C for 10-15 minutes to obtain a gel primary wet film. In practice, the wet coated film can be placed in a constant temperature and humidity chamber with a relative humidity of 60 ± 5% and a temperature of 25 ± 1°C for 10-15 minutes. By aging, the solvent in the wet coated film can be slowly exchanged with the non-solvent, promoting the phase separation process of the film and forming a preliminary gel network structure to improve the density and selectivity of the film. Using a humidity of 60 ± 5% can to some extent avoid the rapid drying of the wet film leading to surface cracking, while also promoting uniform solvent evaporation rate. A temperature of 25 ± 1°C can control the rate of phase separation, and too high a temperature can easily form a loose structure, and too low a temperature can prolong the aging time.

[0044] The thirteenth step is to perform gradient cross-linking and curing treatment on the gel primary wet film to obtain a cross-linked film. In practice, the gel primary wet film can be immersed in a cross-linking solution and treated in two stages: the first stage is treated at a constant temperature of 50 ± 2°C for 20 minutes, and the second stage is treated at a constant temperature of 65 ± 2°C for 40 minutes. The cross-linking solution can be a deionized water solution containing 3-4 wt% maleic acid and 0.8-1.2 wt% concentrated sulfuric acid. The pH value of the cross-linking solution needs to be adjusted to 2.5 ± 0.2 with citric acid. Using the above cross-linking solution can improve the cross-linking efficiency and reduce the swelling rate of the finished film. The reason is that maleic acid contains two carboxyl groups, which can undergo esterification cross-linking reaction with the hydroxyl groups on the polyvinyl alcohol (PVA) molecular chain to form a three-dimensional network structure, and each maleic acid molecule can connect two PVA chains. Compared with similar single carboxyl cross-linking agent such as acetic acid, the cross-linking efficiency is improved by 1 times. Moreover, the ester bond formed by esterification reaction has high chemical stability and strong acid and alkali resistance, which can reduce the swelling rate of the finished film and is more suitable for environments containing high concentrations of toluene and ethanol. The concentrated sulfuric acid as a strong acid catalyst can further improve the cross-linking rate by providing hydrogen ions to reduce the activation energy of the esterification reaction.

[0045] The fourteenth step is to rinse the cross-linked film with deionized water until the effluent pH is greater than 6.0 to obtain a washed film. In practice, the cross-linked film can be rinsed with deionized water until the effluent pH is greater than 6.0 to remove residual cross-linking agents and other impurities on the film surface, thereby reducing the impact on the water permeability and safety of the film.

[0046] Fifteenth step, the water-washed film piece is subjected to multi-stage drying and shaping treatment to obtain a dry film piece. In practice, the water-washed film piece can be placed in a clean and dust-free room, and placed horizontally at room temperature for 4 hours under the control of an environmental wind speed of 0.5 m / s. Then the film piece is transferred to a hot air circulating drying box for treatment at 50°C for 2 hours. Finally, the film piece is subjected to heat treatment at a vacuum degree of -0.095 MPa and a temperature of 80°C for 1.5 hours to obtain a dry film piece. Multi-stage drying can reduce stress concentration in the film, remove free water at a low temperature stage, remove bound water at a high temperature stage, and optimize the pore structure and compactness of the film.

[0047] Sixteenth step, the dry film piece is subjected to heat pressing and strengthening treatment to obtain a preferential water permeable film. In practice, the dry film piece can be placed in a flat plate vulcanizing machine and subjected to heat pressing treatment at 120±5°C and a pressure of 0.5 MPa for 10 minutes to make the composite casting solution layer and the base film interface more fully fused to obtain a preferential water permeable film.

[0048] The first step to the sixteenth step above is an application point of an embodiment of the present disclosure, which solves the technical problem of poor crosslinking rate during preparation of a preferential water permeable film. Factors leading to the poor crosslinking rate during preparation of a preferential water permeable film are as follows: traditional crosslinking agents (such as glutaraldehyde) have single activity and lack efficient catalytic systems, leading to slow esterification crosslinking reaction rate between polyvinyl alcohol molecular chains. If the above factors are solved, the crosslinking rate can be improved. In order to achieve this effect, the present disclosure further provides a preparation method of a preferential water permeable film. By selecting a crosslinking agent containing maleic acid and catalyzing by concentrated sulfuric acid, the esterification reaction rate is accelerated. Thus, the crosslinking rate is improved.

[0049] Step 102, condensing the gaseous product water through a condenser to obtain product water.

[0050] In some embodiments, the gaseous product water can be condensed through a condenser to obtain product water. The condenser can be a shell-and-tube condenser, which is not limited herein.

[0051] Step 103, conveying the retentate from the mixing tank to a rectifying column.

[0052] In some embodiments, the retentate can be conveyed from the mixing tank to the rectifying column by a centrifugal pump, and the rectifying column can be an atmospheric rectifying column.

[0053] In some optional implementations of some embodiments, the retentate can be conveyed from the mixing tank to the rectifying column by the following steps:

[0054] In the first step, the retentate is led out of the retentate side of the PTFM to a mixing tank. In practice, a centrifugal pump can be used to lead the retentate out to the mixing tank.

[0055] In the second step, the retentate in the mixing tank is preheated to obtain preheated retentate. In practice, the retentate in the mixing tank can be preheated to 70-85°C by an electric heater to obtain preheated retentate.

[0056] In the third step, the preheated retentate is fed to the rectifying column. In practice, the preheated retentate at 70-85°C has a small temperature difference with the internal temperature of the rectifying column, which can avoid the sudden drop of the temperature in the column caused by cold retentate, maintain stable gas-liquid equilibrium, and to some extent, reduce the decrease of separation efficiency caused by temperature fluctuation.

[0057] Optionally, the rectifying column can be regulated by the following parameters:

[0058] The number of plates of the rectifying column is controlled to be 10-30, the bottom temperature is controlled to be 110-120°C, and the reflux ratio is controlled to be 0.5-2. When the number of plates is less than 10, the azeotropic composition cannot be broken through, which can result in low purity of the toluene product. When the number of plates is greater than 30, the purity of toluene can be further improved, but the energy consumption can also be increased. In combination with the actual application requirements, the toluene product obtained when the number of plates is 10-30 can meet the required purity requirements. The bottom temperature of 110-120°C is higher than the boiling point of ethanol in the rectifying column, which can make the ethanol fully vaporized at the bottom without increasing too much energy consumption. When the reflux ratio is greater than 2, the liquid phase load in the column is large, which can easily cause the liquid to not flow down. When the reflux ratio is less than 0.5, the gas phase speed can be insufficient, which can easily cause the liquid to leak from the plate holes. The range of 0.5-2 can match the gas-liquid load in the column.

[0059] In step 104, the retentate is subjected to rectification treatment by the rectifying column to obtain rectified material.

[0060] In some implementations, the retentate can be subjected to rectification treatment by the rectifying column to obtain rectified material. The rectified material can include liquid azeotrope and toluene product.

[0061] In some optional implementations of some embodiments, the rectified material can be obtained by the following steps:

[0062] In the first step, the retentate is heated to obtain gaseous azeotrope and toluene product. In practice, the bottom temperature of the rectifying column can be controlled to be 110-120°C to heat the retentate, obtain gaseous azeotrope (containing ethanol-toluene azeotrope) at the top, and obtain toluene product at the bottom.

[0063] In the second step, the gaseous azeotrope is condensed to obtain the liquid azeotrope. In practice, a condenser can be installed at the top of the distillation column to condense the gaseous azeotrope to obtain the liquid azeotrope.

[0064] In step 105, the liquid azeotrope is subjected to pervaporative treatment by the toluene-prior-permeable membrane assembly to obtain the secondary processed material.

[0065] In some embodiments, the liquid azeotrope can be subjected to pervaporative treatment by the toluene-prior-permeable membrane assembly to obtain the secondary processed material. The toluene-prior-permeable membrane assembly can have a similar structure as the water-prior-permeable membrane assembly, except that the toluene-prior-permeable membrane is installed inside the toluene-prior-permeable membrane assembly. The toluene-prior-permeable membrane can be a membrane that selectively permeates toluene.

[0066] Optionally, the toluene-prior-permeable membrane can be prepared by the following steps:

[0067] In the first step, methyltriethoxysilane is dissolved in n-heptane to obtain a mixed solution. In practice, 5 mmol (about 1.04 g) of methyltriethoxysilane can be dissolved in 15 g of n-heptane to obtain the mixed solution.

[0068] In the second step, SBA-15 molecular sieve is dispersed in the mixed solution to obtain a mixture. The SBA-15 molecular sieve is an ordered mesoporous molecular sieve composed of silicon dioxide and belongs to the category of mesoporous materials. In practice, 0.5-1 g of SBA-15 molecular sieve powder can be added to the mixed solution, and the SBA-15 molecular sieve powder can be uniformly dispersed in the mixed solution by an ultrasonic dispersing instrument to obtain the mixture.

[0069] In the third step, the mixture is heated to reflux at 100°C under a nitrogen atmosphere for 12-24 hours to obtain a reaction product. The mixture is stirred during the oil bath process. In practice, the oil bath, the reaction bottle, and the condenser tube can be installed according to the principle of "from bottom to top and from left to right" to ensure the sealing of the interfaces. Then, the mixture is added to the reaction bottle. Nitrogen is introduced into the reaction bottle to remove air in the reaction bottle until the end of the reaction. The reaction bottle is heated to 100°C by the oil bath, and the heating power is adjusted to maintain the droplet refluxing speed in the condenser tube at 1-2 drops per second. The mixture is stirred at 300-500 rpm to ensure uniform dispersion of the SBA-15 particles and prevent sedimentation. After the reaction is completed, the oil bath is turned off, and the reaction bottle is naturally cooled to room temperature. The oil bath is removed, the nitrogen is turned off, and the condenser tube is disassembled to avoid back suction. Then, the reaction product is taken out of the reaction bottle. The reaction bottle can be a three-necked round-bottom flask, which is not limited here.

[0070] The fourth step is to clean the reaction product with n-heptane to obtain a cleaned reaction product. The n-heptane can dissolve the residual organic matter, so that the unreacted silane, solvent and by-products remaining on the surface of the reaction product can be removed, and the purity of the modified molecular sieve can be improved.

[0071] The fifth step is to dry the cleaned reaction product to obtain a modified molecular sieve. In practice, the cleaned reaction product can be placed in a vacuum drying oven at 120°C for drying treatment to obtain the modified molecular sieve. The methyl groups on the surface of the modified molecular sieve have strong adsorption capacity for toluene, so that toluene molecules can be preferentially allowed to pass through the membrane pores.

[0072] The sixth step is to dissolve the vinyl-terminated polydimethylsiloxane in n-heptane to obtain a polymer solution. The mass of n-heptane can be 8-10 times that of the vinyl-terminated polydimethylsiloxane. In practice, the vinyl-terminated polydimethylsiloxane can be placed in a beaker, slowly poured into n-heptane, and placed in a magnetic stirrer. First, stir at a low speed of 100-200 rpm for 5 minutes, and then stir at a high speed of 300-400 rpm until the solution is transparent.

[0073] The seventh step is to disperse the modified molecular sieve in the polymer solution to obtain a uniform mixture. In practice, the modified molecular sieve can be added to the polymer solution in 2-3 portions, and each portion is stirred at a low speed of 200-300 rpm for 5 minutes after addition. After all the portions are added, the stirring speed is adjusted to 400-500 rpm for 30 minutes. The specific stirring time is not limited, and the molecular sieve is uniformly dispersed.

[0074] The eighth step is to add tetraethyl orthosilicate and dibutyltin dilaurate to the uniform mixture under stirring to obtain a primary casting solution. In practice, the tetraethyl orthosilicate and dibutyltin dilaurate can be added to the uniform mixture sequentially or simultaneously under stirring. The stirring speed is 300-400 rpm. The amount of tetraethyl orthosilicate added can be 5%-35% of the mass of the vinyl-terminated polydimethylsiloxane. Dibutyltin dilaurate is used as a catalyst, and the amount added can be 0.5%-1% of the mass of the vinyl-terminated polydimethylsiloxane.

[0075] The ninth step is to stir the primary casting solution at an increased stirring speed for a predetermined time to obtain a secondary casting solution. In practice, the stirring speed of the stirrer can be increased to 500-800 rpm, and the high-speed stirring can be maintained for 30-60 minutes to obtain the secondary casting solution.

[0076] In the tenth step, the secondary casting solution is subjected to defoaming treatment to obtain the finished casting solution. In practice, the secondary casting solution can be subjected to vacuum defoaming or static defoaming treatment to obtain the finished casting solution. Taking vacuum defoaming as an example, the secondary casting solution can be poured into a vacuum defoaming tank, sealed with a cover, connected to a vacuum pump, and slowly pumped to a vacuum degree of ≤50 Pa. The negative pressure is maintained for 15-30 minutes, and after observing that no obvious bubbles rise to the liquid surface, air is slowly introduced to break the vacuum to obtain the finished casting solution.

[0077] In the tenth step, the secondary casting solution is subjected to defoaming treatment to obtain the finished casting solution. In practice, the secondary casting solution can be subjected to vacuum defoaming or static defoaming treatment to obtain the finished casting solution. Taking vacuum defoaming as an example, the secondary casting solution can be poured into a vacuum defoaming tank, sealed with a cover, connected to a vacuum pump, and slowly pumped to a vacuum degree of ≤50 Pa. The negative pressure is maintained for 15-30 minutes, and after observing that no obvious bubbles rise to the liquid surface, air is slowly introduced to break the vacuum to obtain the finished casting solution.

[0078] In the twelfth step, the coated film is dried at room temperature in a vacuum environment for 12 hours to obtain a primary cured film. In practice, the coated film can be placed in a vacuum drying oven, the oven door is closed, and the vacuum is pumped to ≤100 Pa, and the room temperature is maintained. After drying for 12 hours, the oven door should not be frequently opened to prevent air from entering and affecting curing. After the drying is completed, the film should be transparent or translucent and not sticky.

[0079] In the thirteenth step, the primary cured film is dried at 120°C in a vacuum environment for 4 hours to obtain a secondary cured film. In practice, the primary cured film can be placed in a vacuum drying oven and heated to 120°C, and the vacuum degree is maintained at ≤100 Pa for 4 hours.

[0080] In the fourteenth step, after the secondary cured film cools to room temperature, the secondary cured film is washed with deionized water to obtain a washed cured film. In practice, after the drying is completed, the heating power is turned off, the temperature in the oven is naturally reduced to below 50°C, air is slowly introduced to break the vacuum, and the film is removed. Then, the secondary cured film is placed in a beaker containing deionized water, and then gently stirred with a glass rod for 3-5 minutes. The deionized water is replaced, and the washing is repeated 3-4 times until the conductivity of the washing liquid is ≤10 μS / cm. It should be noted that the film edges should be held with tweezers during washing to avoid contacting the film surface to prevent contamination or damage.

[0081] In the fifteenth step, the washed cured film is air-dried at room temperature to obtain a toluene preferential permeation film. In practice, the washed cured film can be laid flat on clean filter paper and placed on a drying rack in a well-ventilated room at room temperature to air-dry to obtain a toluene preferential permeation film.

[0082] In some optional implementations of some embodiments, the secondary processing material can be obtained by the following steps:

[0083] The first step is to heat the liquid azeotrope to 30-50℃ to obtain a preheated azeotrope.

[0084] The second step is to control the gas pressure on the permeation side of the toluene- preferential membrane assembly to be less than the saturated vapor pressure of toluene at 30-50℃. The saturated vapor pressure of toluene at 30-50℃ is about 4-17 kPa. In practice, the gas pressure on the permeation side can be reduced to 0.5-10 kPa A by a vacuum pump connected to the permeation side of the toluene-preferential membrane assembly.

[0085] The third step is to pass the preheated azeotrope through the toluene-preferential membrane assembly to obtain a secondary treated material. In practice, the secondary treated material can be obtained by passing the preheated azeotrope through the toluene-preferential membrane assembly after the first and second steps are completed. The secondary treated material includes the ethanol product obtained on the retentate side and the toluene vapor obtained on the permeation side.

[0086] In some optional implementations of some embodiments, the pressure on both sides of the toluene-preferential membrane assembly can be controlled by a pressure control assembly. The pressure control assembly can be a device composed of a pressure sensor, a temperature sensor, and a controller. The pressure sensor and the temperature sensor can be communicatively connected to the controller. There can be two pressure sensors installed on the retentate side and the permeation side of the toluene-preferential membrane assembly, respectively. There can also be two temperature sensors installed next to the two pressure sensors to more accurately detect the working environment temperature of the pressure sensors. The controller can be an industrial computer, which is not limited here. The pressure control assembly is configured to perform the following steps:

[0087] The first step is to control the pressure sensor to sample both sides of the toluene-preferential membrane assembly at a preset frequency to obtain primary pressure information. The primary pressure information can be an array containing two values, which represent the pressure values of the retentate side and the permeation side of the toluene-preferential membrane assembly, respectively. For example, if the primary pressure information is (0.2, 0.3), it means that the pressure of the retentate side of the toluene-preferential membrane assembly is 0.2 MPa and the pressure of the permeation side is 0.3 MPa. In practice, the controller can control the pressure sensor to sample both sides of the toluene-preferential membrane assembly at a preset frequency and encode the values obtained each time into an array to obtain the primary pressure information. For example, the controller can sample both sides of the toluene-preferential membrane assembly at a frequency of 3 times per second.

[0088] Secondly, the first pressure information obtained by sampling for a preset number of times is filtered to obtain second pressure information. The second pressure information can be an array. In practice, the controller can calculate the average of the two-side pressure values of the first pressure information collected by the pressure sensor for a preset number of times, respectively, to obtain the average of each side, and then combine the two averages into a new array as the second pressure information. For example, assuming that the preset number of times is three, three arrays (1, 2), (2, 3), and (3, 4) are obtained. The numbers representing the pressure values of the same side in the three arrays can be averaged. That is, the three first numbers in the three arrays are added and divided by 3, the three second numbers are added and divided by 3, and the two numbers obtained are used to form a new array. That is, 1+2+3=6, 6 / 3=2; 2+3+4=9, 9 / 3=3, and the new array is (2, 3).

[0089] Further, due to the piezoresistive effect, the resistivity of the semiconductor material of most pressure sensors increases when the temperature rises, causing the output signal to deviate from the true pressure value. Since the toluene preferential permeation membrane assembly separates toluene from other substances mainly by means of osmotic vaporization, the working environment temperature is usually higher than the normal temperature, so it is necessary to compensate and correct the pressure value measured by the pressure sensor to more accurately control the process parameters.

[0090] Thirdly, the temperature sensor detects the temperature of the working environment of the pressure sensor to obtain an environment temperature value. In practice, the controller can control the temperature sensor to collect the environment temperature value of the working environment of the pressure sensor. For the case where multiple temperature sensors are present, the average of the temperature values detected by the multiple temperature sensors can be determined as the environment temperature value.

[0091] Fourthly, a pressure compensation coefficient is determined according to the environment temperature value. The pressure compensation coefficient can be a numerical value used to correct the pressure value measured by the pressure sensor. In practice, the controller can match the pressure compensation coefficient corresponding to the current environment temperature value through a preset temperature value-compensation coefficient mapping table.

[0092] Fifthly, the current pressure information is determined according to the second pressure information and the pressure compensation coefficient. The current pressure information can include the retentate-side pressure value and the permeate-side pressure value, and the retentate-side pressure value and the permeate-side pressure value can be stored in the form of an array with reference to the second pressure information. In practice, the controller can determine the current pressure information by the following formula:

[0093] Retentate-side pressure value = second pressure value + (1 + compensation coefficient x (temperature value - 25℃)).

[0094] The "secondary pressure value" can be a value representing the pressure on the permeate side included in the secondary pressure information. The "compensation coefficient" can be the pressure compensation coefficient. The "temperature value" can be the ambient temperature value.

[0095] The permeate side pressure value = the secondary pressure value + (1 + the compensation coefficient x (the temperature value - 25℃)).

[0096] The "secondary pressure value" can be a value representing the pressure on the permeate side included in the secondary pressure information. The "compensation coefficient" can be the pressure compensation coefficient. The "temperature value" can be the ambient temperature value.

[0097] The permeate side pressure value and the pressure value determined by the formula are arranged into an array as the current pressure information.

[0098] In the sixth step, in response to the fact that the pressure on the permeate side does not match the first target pressure interval, first deviation information is generated based on the pressure on the permeate side and the first target pressure interval. The first target pressure interval can be a preset pressure range on the permeate side. The fact that the pressure on the permeate side does not match the first target pressure interval can mean that the pressure on the permeate side is not within the first target pressure interval, and can be greater than or less than the interval. In practice, the controller can generate the first deviation information from the following two aspects:

[0099] In the first aspect, when it is determined that the pressure on the permeate side is greater than the first target pressure interval, the first deviation information can be determined by subtracting the maximum value of the first target pressure interval from the pressure on the permeate side. For example, if the first target pressure interval is [2, 3] and the pressure on the permeate side is 4, the first deviation information can be "1".

[0100] In the second aspect, when it is determined that the pressure on the permeate side is less than the first target pressure interval, the first deviation information can be determined by subtracting the pressure on the permeate side from the minimum value of the first target pressure interval. For example, if the first target pressure interval is [2, 3] and the pressure on the permeate side is 1, 2-1 = 1. It should be noted that the difference values obtained by the first aspect and the second aspect can be equal, but the meanings represented by the two aspects are different. The first aspect needs to reduce the pressure on the permeate side, and the second aspect needs to increase the pressure on the permeate side. Therefore, in order to distinguish the different meanings represented by the two aspects, the controller can perform a preset processing on the difference value obtained by the second aspect (or the first aspect, which is not limited) to obtain the first deviation information. For example, the controller can multiply the obtained difference value by "-1", and then determine the obtained product as the first deviation information.

[0101] In the seventh step, the first control parameter is determined according to the first deviation information. The first control parameter can be a parameter for adjusting the pressure on the retentate side, such as the change in the rotational speed of the feed pump. In practice, the controller can match the first control parameter corresponding to the first deviation information from a preset deviation information-control parameter mapping table. For example, when the first deviation information is "-1", the corresponding first control parameter can be "increase the rotational speed by 80 rpm"; when the first deviation information is "1", the corresponding first control parameter can be "decrease the rotational speed by 80 rpm".

[0102] In the eighth step, the rotational speed of the feed pump is adjusted according to the first control parameter. The feed pump can be connected to the retentate side of the toluene- preferential membrane module. In practice, the controller can adjust the rotational speed of the feed pump by the following steps:

[0103] In step one, the original rotational speed of the feed pump is added to the rotational speed adjustment amount corresponding to the first control parameter to obtain the target rotational speed. When the rotational speed needs to be increased, the rotational speed adjustment amount is positive; when the rotational speed needs to be decreased, the rotational speed adjustment amount is negative. The controller can determine that the rotational speed adjustment amount is positive when the first control parameter contains the word "increase", and determine that the rotational speed adjustment amount is negative when the first control parameter contains the word "decrease". The specific value of the rotational speed adjustment amount can be directly extracted from the numerical part of the first control parameter. Then, the determined rotational speed adjustment amount is added to the original rotational speed to obtain the target rotational speed. For example, when the first control parameter is "increase the rotational speed by 80 rpm", the rotational speed adjustment amount can be determined as +80. Assuming that the original rotational speed of the feed pump is 200 rpm, the target rotational speed at this time is 200+80 = 280 rpm.

[0104] In step two, the obtained target rotational speed is compared with a preset rotational speed-power relationship table to obtain the target power value. For example, the target power value corresponding to 280 rpm can be 50 W.

[0105] In step three, the actual power value of the feed pump is adjusted to the target power value.

[0106] In the ninth step, in response to the fact that the permeation side pressure value does not match the second target pressure interval, the second deviation information is generated based on the permeation side pressure value and the second target pressure interval. The second target pressure interval can be a preset permeation side pressure range. The fact that the permeation side pressure value does not match the second target pressure interval means that the permeation side pressure value is not within the second target pressure interval, and can be greater than or less than the interval. It should be noted that since the permeation side of the toluene-selective membrane module is in a negative pressure state, the actual pressure value can be negative, which means that the greater the negative pressure, the smaller the corresponding pressure value. In order to avoid errors, the permeation side pressure value and the second target pressure interval are represented by the absolute value of the actual pressure value to represent the degree of negative pressure. For example, if the permeation side pressure value is 1, it actually represents a pressure of -1 MPa on the permeation side. In practice, the controller can generate the second deviation information from two aspects:

[0107] In the first aspect, when it is determined that the permeation side pressure value is greater than the second target pressure interval, the second deviation information is determined by subtracting the maximum value of the second target pressure interval from the permeation side pressure value. For example, if the second target pressure interval is [2, 3] and the permeation side pressure value is 4, the second deviation information at this time can be "1".

[0108] In the second aspect, when it is determined that the permeation side pressure value is less than the second target pressure interval, the difference value is obtained by subtracting the permeation side pressure value from the minimum value of the second target pressure interval. For example, if the second target pressure interval is [2, 3] and the permeation side pressure value is 1, then 2-1=1. It should be noted that the difference values obtained by the first aspect and the second aspect can be equal, but the meanings represented by the two aspects are different. The first aspect needs to reduce the degree of negative pressure on the permeation side, and the second aspect needs to increase the degree of negative pressure on the permeation side. Therefore, in order to distinguish the different meanings represented by the two aspects, the controller can perform a preset processing on the difference value obtained by the second aspect (or the first aspect, which is not limited) to obtain the second deviation information. For example, the controller can multiply the obtained difference value by "-1", and then determine the obtained product as the second deviation information.

[0109] In the tenth step, the second control parameter is determined according to the second deviation information. The second control parameter can be a parameter for adjusting the pressure on the permeation side, such as the change amount of the power of the vacuum pump. In practice, the controller can match the second control parameter corresponding to the current second deviation information from a preset deviation information-control parameter mapping table. For example, when the second deviation information is "-1", the corresponding second control parameter can be "power increase 20W"; when the second deviation information is "1", the corresponding second control parameter can be "power decrease 20W".

[0110] In the tenth step, the power of the vacuum pump is adjusted according to the second control parameter. The vacuum pump is connected to the permeate side of the toluene-prioritized membrane assembly. In practice, the controller can first obtain the target power by adding the power adjustment amount corresponding to the second control parameter to the original power of the vacuum pump. Then, the power of the vacuum pump is adjusted to the target power. When the second control parameter indicates that the power needs to be increased, the power adjustment amount is positive; when the power needs to be decreased, the power adjustment amount is negative. When the second control parameter contains the word “increase”, the controller can determine that the power adjustment amount is positive; when the second control parameter contains the word “decrease”, the controller can determine that the power adjustment amount is negative. The specific value of the power adjustment amount can be directly extracted from the numerical part of the second control parameter. For example, when the second control parameter is “power increase 20W”, the power adjustment amount can be determined as +20W. Assuming that the original power of the feed pump is 60W, the target power at this time is 60+20=80W. Then, the power of the vacuum pump is adjusted to 80W.

[0111] The first step to the tenth step above is an application point of one embodiment of the present disclosure, which solves the technical problem of low filtration efficiency of the toluene-prioritized membrane assembly. The factors that cause the low filtration efficiency of the toluene-prioritized membrane assembly are as follows: In order to use the toluene-prioritized membrane assembly, it is necessary to accurately detect the pressures on the retentate side and the permeate side in real time under an environment higher than room temperature, and to adjust the pressures to the efficient range. Currently, pressure sensors are commonly used to detect the pressures on both sides of the toluene-prioritized membrane assembly in real time. However, under an environment higher than room temperature, due to the piezoresistive effect, the pressure values measured by the pressure sensors have a large error with the actual values. If the above factors are solved, the filtration efficiency of the toluene-prioritized membrane assembly can be improved. In order to achieve this effect, the present disclosure further provides a pressure measurement method based on “sampling-filtering-compensation”. A plurality of sets of pressure data are obtained by multiple samplings, the plurality of sets of data are filtered, and then the pressure values are compensated and corrected according to the working environment temperature, thereby improving the accuracy of the pressure values measured by the pressure sensor. Thus, the filtration efficiency of the toluene-prioritized membrane assembly is improved.

[0112] In step 106, the toluene-containing vapor is subjected to condensation treatment to obtain a liquid toluene-containing material.

[0113] In some embodiments, the toluene-containing vapor can be subjected to condensation treatment by a condenser to obtain a liquid toluene-containing material. It should be noted that the content of toluene in the above-mentioned liquid toluene-containing material is 45-60wt%, which cannot be directly collected as a toluene product.

[0114] In step 107, the liquid toluene-containing material is delivered to the mixing tank by a liquid transfer pump and is subjected to treatment together with the retentate material.

[0115] In some embodiments, a liquid toluene-containing material can be transferred to a mixing tank via a liquid transfer pump and processed together with the retentate material. The liquid toluene-containing material has a toluene content of 45-60 wt% and cannot be directly collected as a toluene product. Therefore, the liquid toluene-containing material can be re-transferred to the mixing tank as a recycle material for further separation processing, thereby achieving material recycling.

[0116] In step 108, product water, toluene product and ethanol product are respectively produced.

[0117] In some embodiments, liquid transfer pumps can be used to separately withdraw product water, product toluene, and product ethanol from their respective storage devices.

[0118] Some embodiments of the present disclosure provide a method for separating a toluene-ethanol-water azeotrope, which can simplify the process flow for separating the toluene-ethanol-water azeotrope. Specifically, the reason why the separation process of most toluene-ethanol-water azeotropes is relatively complex is that the toluene-ethanol-water ternary azeotrope is currently separated by extractive distillation. When the toluene-ethanol-water ternary azeotrope is separated by the above method, in addition to separating the ternary azeotrope, additional steps such as the selection, use, and recovery of the extractant are required. Based on this, some embodiments of the present disclosure provide a method for separating a toluene-ethanol-water three-phase azeotrope, the method comprising separating the toluene-ethanol-water three-phase azeotrope through a preferentially water-permeable membrane assembly to obtain a primary treatment material, wherein the primary treatment material comprises a retentate material and vaporous product water, and the retentate material is collected in a mixing tank; condensing the vaporous product water through a condenser to obtain product water; conveying the retentate material from the mixing tank to a distillation tower; rectifying the retentate material through the distillation tower to obtain a rectified material, wherein the rectified material comprises a liquid azeotrope and a toluene product; pervaporating the liquid azeotrope through a preferentially toluene-permeable membrane assembly to obtain a secondary treatment material, wherein the secondary treatment material comprises an ethanol product and toluene-containing vapor; condensing the toluene-containing vapor to obtain a liquid toluene-containing material; conveying the liquid toluene-containing material to the mixing tank through a liquid transfer pump to be processed together with the retentate material; and extracting the product water, the toluene product, and the ethanol product respectively. By combining membrane separation technology with distillation technology, a dual-membrane module separation system without an extractant is formed, thereby simplifying the process for separating the toluene-ethanol-water three-phase azeotrope.

[0119] The above description is merely exemplary of some of the many possible embodiments of the present disclosure and of the principles thereof. It is to be understood that those skilled in the art will be able to devise various embodiments of the present disclosure without departing from the scope of the present disclosure as disclosed in the above description and attached claims, and that the scope of the present disclosure is not limited to the specific technical features described above. For example, the technical features described above can be replaced with other technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) to form other technical solutions.

Claims

1. A method for separating a toluene-ethanol-water three-phase azeotrope, comprising: Separating the toluene-ethanol-water three-phase azeotrope through a preferentially water-permeable membrane assembly to obtain a primary processed material, wherein the primary processed material includes a retentate material and vaporous product water, and the retentate material is collected in a mixing tank; condensing the vaporous product water through a condenser to obtain product water; transporting the retentate material from the mixing tank to a distillation tower; The retentate material is subjected to a rectification treatment by the rectification tower to obtain a rectification material, wherein the rectification material comprises a liquid azeotrope and a toluene product; Performing pervaporation treatment on the liquid azeotrope through a toluene-preferentially permeable membrane assembly to obtain a secondary treatment material, wherein the secondary treatment material includes an ethanol product and toluene-containing vapor; condensing the toluene-containing vapor to obtain a liquid toluene-containing material; The liquid toluene-containing material is transported to the mixing tank by a liquid transfer pump and is processed together with the retentate material; The product water, the toluene product and the ethanol product are respectively produced.

2. The method according to claim 1, wherein The method of separating and treating the toluene-ethanol-water three-phase azeotrope by using a preferentially water-permeable membrane assembly to obtain a primary treated material comprises: Heating the toluene-ethanol-water three-phase azeotrope to a preset temperature to obtain a heating azeotrope, wherein the heating azeotrope is located on the retentate side of the preferential water permeable membrane assembly; The air pressure on the permeate side of the preferentially water-permeable membrane assembly is controlled to be lower than the air pressure on the retentate side to obtain a primary treated material.

3. The method according to claim 1, wherein The step of transporting the retentate material from the mixing tank to a distillation tower comprises: Leading the retentate material from the retentate side of the preferentially water permeable membrane assembly to the mixing tank; preheating the retentate material in the mixing tank to obtain a preheated retentate material; The preheated retentate material is conveyed to the distillation column.

4. The method according to claim 1, wherein The step of performing a rectification process on the retentate material by the rectification tower to obtain the rectified material comprises: heating the retentate material to obtain a vapor azeotrope and a toluene product; The vapor azeotrope is condensed to obtain a liquid azeotrope.

5. The method according to claim 1, wherein The method of pervaporating the liquid azeotrope through a toluene-preferential membrane assembly to obtain a secondary treated material comprises: heating the liquid azeotrope to 30-50° C. to obtain a preheated azeotrope; Controlling the gas pressure on the permeate side of the toluene preferential permeation membrane assembly to be less than the saturated vapor pressure of toluene at 30-50° C.; The preheated azeotrope is passed to the toluene-preferentially permeable membrane assembly to obtain a secondary treatment material.

6. The method according to claim 1, wherein Before the retentate material is subjected to rectification treatment by the rectification tower to obtain the rectified material, the method further comprises: The number of plates of the distillation tower is controlled to be 10 to 30, the bottom temperature is controlled to be 110 to 120° C., and the reflux ratio is controlled to be 0.5 to 2.

7. The method according to claim 2, wherein: The step of controlling the air pressure on the permeate side of the preferentially water permeable membrane assembly to be lower than the air pressure on the retentate side to obtain the primary treated material comprises: Controlling the air pressure on the retentate side of the preferentially water permeable membrane assembly to be between 0.05 and 0.3 MPaG; The air pressure on the permeation side of the preferentially water-permeable membrane assembly is controlled to be between 0.5 and 10 kPaA.

8. The method according to claim 5, wherein The method of controlling the gas pressure on the permeate side of the toluene preferentially permeable membrane assembly to be lower than the saturated vapor pressure of toluene at 30-50° C. comprises: The gas pressure on the permeation side of the toluene preferentially permeating membrane assembly is controlled to be between 0.5 and 10 kPaA.

9. The method according to claim 1, wherein Before performing pervaporation treatment on the liquid azeotrope through the toluene preferentially permeable membrane assembly to obtain a secondary treated material, the method further comprises: Methyltriethoxysilane was dissolved in n-heptane to obtain a mixed solution; dispersing SBA-15 molecular sieve into the mixed solution to obtain a mixture; Under a nitrogen atmosphere, heating the mixture in an oil bath at 100° C. for reflux reaction for 12 to 24 hours to obtain a reaction product, wherein the mixture is stirred during the oil bath process; washing the reaction product with n-heptane to obtain a washed reaction product; Drying the cleaned reaction product to obtain a modified molecular sieve; Dissolving vinyl-terminated polydimethylsiloxane in n-heptane to obtain a polymer solution, wherein the mass of n-heptane is 8 to 10 times that of the vinyl-terminated polydimethylsiloxane; dispersing the modified molecular sieve in the polymer solution to obtain a uniform mixed solution; adding tetraethyl orthosilicate and dibutyltin dilaurate to the uniform mixed solution under stirring to obtain a primary casting solution; Stirring the primary casting solution for a preset time under the condition of increasing the stirring speed to obtain a secondary casting solution; Degassing the secondary casting solution to obtain a finished casting solution; applying the finished casting solution on a support film by blade coating to obtain a coating film; The coating film was dried at room temperature in a vacuum environment for 12 hours to obtain a primary cured film; drying the primary cured film at 120° C. under vacuum for 4 hours to obtain a secondary cured film; After the secondary cured film is cooled to room temperature, the secondary cured film is washed with deionized water to obtain a washed cured film; The cleaned cured film was air-dried at room temperature to obtain a toluene-permeable film.

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