Preparation device and method of high-purity propylene glycol methyl ether

Abstract

The application discloses a kind of preparation device and method of high-purity propylene glycol methyl ether, including sequentially interconnected raw material tank, raw material pump, heater, dense pervaporation water-permeable membrane group includes first inlet and first retentate side outlet, first inlet with the heater communication;Dense pervaporation methanol-permeable membrane group includes second inlet and second retentate side outlet, second inlet and the first retentate side outlet of dense pervaporation water-permeable membrane group communication;Dense pervaporation membrane group includes third inlet and third retentate side outlet, third inlet and the second retentate side outlet of dense pervaporation methanol-permeable membrane group communication, third retentate side outlet is used to communicate liquid storage tank.The application can remove the impurity of industrial grade propylene glycol methyl ether, improve product purity high, and the purity of obtained propylene glycol methyl ether is 99.999%.

Description

Technical Field

[0001] This invention relates to the field of high-purity chemical reagents, and particularly to an apparatus and method for preparing high-purity propylene glycol methyl ether. Background Technology

[0002] Propylene glycol methyl ether is a very important intermediate compound. Because it contains both a hydrophobic functional group (ether bond) that can dissolve lipophilic compounds and a hydrophilic group (hydroxyl group) that can dissolve water-soluble substances, it is widely used as a general-purpose solvent in coating materials, paints, antifreeze, printing, leather dyeing, and electronic chemicals. High-purity propylene glycol methyl ether is often used as a stripping agent, photoresist diluent, and silicon wafer cleaning agent in photoresist production processes. Its impurity content has a significant impact on the quality of semiconductor products.

[0003] In the industrial production of propylene glycol methyl ether using the propylene oxide process, two isomers are generated: propylene glycol methyl ether and 2-methoxy-1-propanol, along with water. Water and propylene glycol methyl ether exhibit an azeotropic reaction and cannot be separated by ordinary distillation. As isomers, propylene glycol methyl ether and 2-methoxy-1-propanol have boiling points that differ by 1°C, making separation via distillation difficult. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an apparatus and method for preparing high-purity propylene glycol methyl ether. This apparatus and method can remove impurities from industrial-grade propylene glycol methyl ether, thereby improving the purity of the product.

[0005] This invention is achieved through the following technical solution:

[0006] An apparatus for preparing high-purity propylene glycol methyl ether includes a raw material tank, a raw material pump, and a heater connected in sequence. The apparatus further includes:

[0007] A dense pervaporation water-permeable membrane assembly, which can remove water from a crude propylene glycol methyl ether solution and includes a first inlet and a first retentate-side outlet, wherein the first inlet is connected to the heater;

[0008] A dense pervaporation methanol permeation membrane module, wherein the dense pervaporation methanol permeation membrane module can remove methanol from crude propylene glycol methyl ether solution and includes a second inlet and a second urate side outlet, wherein the second inlet is connected to the first urate side outlet of the dense pervaporation water permeation membrane module;

[0009] A dense pervaporation membrane assembly is provided, which can remove 2-methoxy-1-propanol from a crude propylene glycol methyl ether solution to obtain high-purity propylene glycol methyl ether and includes a third inlet and a third osmosis side outlet. The third inlet is connected to the second osmosis side outlet of the dense pervaporation methanol permeation membrane assembly, and the third osmosis side outlet is used to connect to a storage tank.

[0010] Furthermore, the dense pervaporation water-permeable membrane assembly also includes a first permeation-side outlet, which is sequentially connected to a first-stage condenser and a first permeate recovery tank, the first permeate recovery tank being used to recover water from propylene glycol methyl ether.

[0011] Furthermore, the dense pervaporation methanol membrane assembly also includes a second permeate-side outlet, which is sequentially connected to a second-stage condenser and a second permeate recovery tank, which can recover methanol from propylene glycol methyl ether.

[0012] Furthermore, the dense pervaporation membrane assembly also includes a third permeate-side outlet, which is sequentially connected to a third-stage condenser and a third permeate recovery tank, which can recover 2-methoxy-1-propanol from propylene glycol methyl ether.

[0013] Furthermore, the apparatus for preparing high-purity propylene glycol methyl ether also includes a vacuum pump, and the first-stage condenser, the second-stage condenser, and the third-stage condenser are all connected to the vacuum pump.

[0014] Furthermore, the dense pervaporation methanol permeation membrane in the dense pervaporation methanol permeation membrane assembly includes a first layer, a second layer, and a third layer, wherein the first and second layers are both asymmetric tubular inorganic membranes, and the third layer is an effective separation layer;

[0015] The first layer of the dense pervaporation methanol membrane is selected from one of alumina, corundum, and mullite.

[0016] The second layer of the dense pervaporation methanol membrane is selected from one of alumina, titanium dioxide, and zirconium oxide.

[0017] The third layer of the dense pervaporation methanol membrane is a polycarbosilane composite membrane modified with polyacrylic acid.

[0018] Furthermore, the first layer of the dense pervaporation methanol membrane has an average pore size of 500–1000 nm, the second layer has an average pore size of 2–100 nm, and the third layer has a thickness of 5–20 μm.

[0019] Furthermore, the structure of the dense pervaporation membrane in the dense pervaporation membrane assembly includes a first layer, a second layer, and a third layer. The first and second layers of the dense pervaporation membrane are both asymmetric tubular inorganic membranes, and the third layer is an effective separation layer.

[0020] The first layer of the dense pervaporation membrane is selected from one of alumina, corundum, and mullite;

[0021] The second layer of the dense pervaporation membrane is selected from one of alumina, titanium dioxide, and zirconium oxide;

[0022] The third layer of the dense pervaporation membrane is a dense membrane composed of UiO-66 doped PDMS.

[0023] Furthermore, the dense pervaporation membrane has an average pore size of 500–1000 nm for the first layer, an average pore size of 2–100 nm for the second layer, and a thickness of 5–20 μm for the third layer.

[0024] Furthermore, the thickness of the dense pervaporation permeable membrane in the dense pervaporation permeable membrane assembly is 5-20 μm, and the dense pervaporation permeable membrane is selected from one or more of molecular sieve membranes, chitosan membranes, silica membranes, and PVA membranes.

[0025] Furthermore, the dense pervaporation membrane can also be selected from molecular sieve membranes, chitosan membranes, silica membranes, and PVA membranes by doping or modifying nanoparticles.

[0026] Furthermore, the heater has a heating temperature of 50–100°C, and the dense pervaporation water-permeable membrane group, the dense pervaporation methanol-permeable membrane group, and the dense pervaporation membrane group have an operating temperature of 50–100°C.

[0027] A method for preparing high-purity propylene glycol methyl ether, the method comprising the following steps:

[0028] Step S1: The crude propylene glycol methyl ether solution is fed into the raw material tank and then heated by a heater for later use;

[0029] Step S2: Primary membrane dehydration: The heated crude propylene glycol methyl ether solution obtained in step S1 is fed into a dense pervaporation water-permeable membrane assembly for pervaporation to remove water from the crude propylene glycol methyl ether solution, resulting in a first osmotic solution and a first permeate. The first permeate is 90% to 98% water, and the first osmotic solution is a propylene glycol methyl ether solution containing methanol and 2-methoxy-1-propanol.

[0030] Step S3: Secondary membrane removal of methanol: The first permeate obtained in step S2 is transported to a dense pervaporation methanol permeate membrane group for pervaporation to remove methanol from the first permeate, resulting in a second permeate and a second permeate. The second permeate is 90% to 98% methanol and is a propylene glycol methyl ether solution containing 2-methoxy-1-propanol.

[0031] Step S4: Three-stage membrane removal of 2-methoxy-1-propanol: The second permeate obtained in step S3 is transported to a dense pervaporation membrane assembly for pervaporation to remove 2-methoxy-1-propanol from the second permeate, resulting in a third permeate and a third permeate. The third permeate is 90% to 98% 2-methoxy-1-propanol, and the third permeate is a high-purity propylene glycol methyl ether solution.

[0032] Furthermore, steps S2 to S4 specifically include:

[0033] First-stage membrane dehydration: The crude propylene glycol methyl ether solution obtained after heating in step S1 is fed into a dense pervaporation water-permeable membrane assembly for pervaporation. Water selectively permeates through the dense pervaporation water-permeable membrane to become permeate vapor and is enriched on the first permeate side. The first permeate side is evacuated at 1000-8000 Pa. The permeate vapor on the first permeate side is condensed at a condensation temperature of -15 to 0°C by the first-stage condenser to form the first permeate liquid. The first permeate liquid is obtained on the first permeate side of the dense pervaporation water-permeable membrane. The first permeate liquid is a propylene glycol methyl ether solution containing methanol and 2-methoxy-1-propanol.

[0034] Methanol removal via secondary membrane: The first permeate obtained in step S2 is transported to a dense pervaporation methanol membrane assembly for pervaporation. Methanol selectively permeates through the dense pervaporation methanol membrane, becoming permeate vapor and accumulating on the second permeate side. The second permeate side is evacuated at 1000–8000 Pa. The permeate vapor on the second permeate side is condensed at a temperature of -15–0°C by the second-stage condenser to form the second permeate. The second permeate is obtained from the second permeate side of the dense pervaporation methanol membrane. The second permeate is a propylene glycol methyl ether solution containing 2-methoxy-1-propanol.

[0035] Step S4: Three-stage membrane removal of 2-methoxy-1-propanol: The second permeate obtained in step S3 is transported to a dense pervaporation membrane assembly for pervaporation. 2-methoxy-1-propanol selectively permeates through the dense pervaporation membrane, becoming permeate vapor and accumulating on the third permeate side. The third permeate side is evacuated at 1000-8000 Pa. The permeate vapor on the third permeate side is condensed at a temperature of -15 to 0°C by the third-stage condenser to form the third permeate. The third permeate is obtained on the third permeate side of the dense pervaporation membrane. The third permeate is a high-purity propylene glycol methyl ether solution.

[0036] Furthermore, the dense pervaporation methanol membrane in step S3 is prepared using the following method:

[0037] Step (1) Pre-plugging the hole: Soak the tubular inorganic membrane in water for 30-60 minutes. After soaking, blow the tubular inorganic membrane for later use.

[0038] Step (2) Preparation of transition layer: Immerse the pre-plugged tubular inorganic membrane in water glass solution, dip and coat the outer surface of the membrane for 5-60 seconds, and then dry;

[0039] Step (3) Coating: Dissolve polycarbosilane powder with a molecular weight of 4000 in p-xylene to prepare a coating solution with a concentration of 1-10%, and then dip the coating solution onto the surface of the membrane obtained in step (2) to obtain the composite membrane precursor.

[0040] Step (4) Curing: The composite film precursor from step (3) is first cured in an air stream at 150-300°C for 2-5 hours, and then heated at 750°C for 0.5 hours in a N2 atmosphere;

[0041] Step (5) Modification: Dissolve polyacrylic acid powder in hot water at 85-95°C to prepare a polyacrylic acid solution with a concentration of 1-3%. Then add 1-3% tetraethyl orthosilicate by mass of polyacrylic acid, stir, and then dip-coat the membrane obtained in step 4. Dry to obtain a dense pervaporated methanol membrane.

[0042] Furthermore, the dense pervaporation membrane in step S4 is prepared using the following method:

[0043] Step (1): Pre-plugging the hole: Soak the tubular inorganic membrane in water for 30-60 minutes. After soaking, blow the tubular inorganic membrane for later use.

[0044] Step (2) Preparation of transition layer: Immerse the pre-plugged tubular inorganic membrane in water glass solution, dip and coat the outer surface of the membrane for 5-60 seconds, and then dry;

[0045] Step (3) MOF preparation: Dissolve ZrCl4 in half of the DMF, then add acetic acid solution, sonicate for 10 min, then dissolve terephthalic acid in the remaining half of the DMF, then pour the terephthalic acid solution into the ZrCl4 solution, add water and stir at room temperature for 30 min. After stirring, transfer the resulting solution to a stainless steel autoclave lined with PTFE, and place it in a convection oven at 120℃ for 72 h for synthesis. After synthesis, centrifuge the suspension, wash with ethanol, and then vacuum dry.

[0046] Step (4) Preparation of coating solution: Take a certain mass of hydroxyl-terminated polydimethylsiloxane prepolymer and mix it with 3 to 10 times the weight of polydimethylsiloxane in n-heptane. Stir for 15 minutes to fully dissolve the polydimethylsiloxane. Then add 3 to 20% of the weight of polydimethylsiloxane in tetraethyl orthosilicate as a crosslinking agent and stir. Finally, add 0.01 to 5% of the weight of polydimethylsiloxane in dibutyltin dilaurate as a catalyst and stir to perform pre-crosslinking to obtain a polymer solution. Then add 1 to 5 wt% of MOFs to the polymer solution and sonicate continuously for 1 to 4 hours until the MOFs particles are completely dispersed to obtain the coating solution.

[0047] Step (5) Coating: The coating liquid obtained in step (4) is immersed in the base film obtained in step 2, evaporated at room temperature, and finally dried to obtain a dense pervaporation membrane.

[0048] Furthermore, the preparation of the dense pervaporation methanol membrane in step S3 includes:

[0049] Step (1) The tubular inorganic membrane is air-washed at 0.1-0.2 MPa for 5-20 minutes and then set aside.

[0050] Step (2): Dipping speed 0.05-0.2 m / s, drying temperature 30-50℃, drying time 2-4 h;

[0051] Step (3) Dipping speed: 0.05-0.2 m / s; Dipping time: 5-60 s;

[0052] Step (4) Heating rate: 20–50 °C / min;

[0053] Step (5): Stirring time 2-6h, dipping speed 0.05-0.2m / s, dipping time 5-60s, drying temperature 100-150℃, drying time 2-4h.

[0054] Furthermore, the preparation of the dense pervaporation membrane in step S4 also includes:

[0055] Step (1) The tubular inorganic membrane is air-washed at 0.1-0.2 MPa for 5-20 minutes and then set aside.

[0056] Step (2): Dipping speed 0.05-0.2 m / s, drying temperature 30-50℃, drying time 2-4 h;

[0057] Step (3): Wash with ethanol 3-5 times, vacuum degree 10-30 kPa, drying temperature 25-50℃, drying time 2-6 h.

[0058] In step (3), the molar ratio of ZrCl4: terephthalic acid: water: acetic acid: DMF is 1:1:1:150:500;

[0059] Step (4) After adding tetraethyl orthosilicate, the stirring time is 10-20 min; after adding dibutyltin dilaurate, the stirring time is 10-20 min; and the ultrasonic temperature is 80℃.

[0060] Step (5): Dipping speed 0.05–0.2 m / s, dipping time 5–60 s, drying temperature 80–100 °C, drying time 2–4 h. Further, the crude propylene glycol methyl ether solution contains 0.0001–30 wt% water and 0.01–20 wt% 2-methoxy-1-propanol.

[0061] Furthermore, the polydimethylsiloxane is PDMS.

[0062] Furthermore, the MOFs are UiO-66.

[0063] Compared with the prior art, the advantages of this invention are:

[0064] 1. The present invention uses a single pervaporation system for primary membrane dehydration, secondary membrane methanol removal, and tertiary membrane 2-methoxy-1-propanol removal. By combining different functional membranes, the two purposes of removing water and organic impurities can be achieved simultaneously. The heating system and vacuum system are shared, which can effectively reduce equipment investment and lower costs.

[0065] 2. This invention uses a composite membrane of polyacrylic acid modified with polysilane, which has preferential selectivity for methanol. By controlling the crosslinking temperature, the composite membrane of polysilane can obtain membrane structures with different pore sizes. The resulting microstructure has preferential selectivity for methanol, with a faster permeation rate and greater flux than other components, thereby achieving the purpose of removing methanol.

[0066] 3. This invention uses a separation membrane doped with UiO-66 and PDMS. UiO-66 has a regular inorganic structure with a pore size of 0.6 nm, good stability, and preferential selectivity for 2-methoxy-1-propanol. Through preferential adsorption and pore size sieving effect, 2-methoxy-1-propanol and propylene glycol methyl ether are separated.

[0067] 4. The secondary membrane for methanol removal and the tertiary membrane for 2-methoxy-1-propanol removal of the present invention use ceramic-based membranes, which have excellent solvent resistance. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the apparatus for preparing high-purity propylene glycol methyl ether according to the present invention;

[0069] 1. Feed tank; 2. Feed pump; 3. Heater; 4. Dense pervaporation water-permeable membrane assembly; 40. First inlet; 42. First-stage condenser; 43. First residual side; 430. First residual side outlet; 44. First permeate side; 440. First permeate side outlet; 5. Dense pervaporation methanol-permeable membrane assembly; 50. Second inlet; 52. Second-stage condenser; 53. Second residual side; 530. Second residual side outlet; 54. Second permeate side; 540. Second permeate side outlet; 6. Dense pervaporation membrane assembly; 60. Third inlet; 62. Third-stage condenser; 63. Third residual side; 630. Third residual side outlet; 64. Third permeate side; 640. Third permeate side outlet; 7. First permeate recovery tank; 8. Second permeate recovery tank; 9. Third permeate recovery tank; 10. Storage tank; 11. Vacuum pump. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this invention clearer, the following detailed description, in conjunction with embodiments, is provided to enable those skilled in the art to fully understand the technical content of this invention. It should be understood that the following embodiments are for further illustration of this invention and should not be construed as limiting the scope of protection of this invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description of this invention all fall within the scope of protection of this invention. The specific preparation method parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to limit themselves to the specific values ​​in the examples below.

[0071] like Figure 1 A device for preparing high-purity propylene glycol methyl ether mainly includes a raw material tank 1, a raw material pump 2, a heater 3, a dense pervaporation water-permeable membrane group 4, a dense pervaporation methanol-permeable membrane group 5, and a dense pervaporation membrane group 6, which are connected in sequence.

[0072] The dense pervaporation water-permeable membrane assembly 4 includes a first inlet 40 and a first permeate-side outlet 440. The first inlet 40 is sequentially connected to a heater 3, a feed pump 2 and a feed tank 1. The first permeate-side outlet 440 is sequentially connected to a first-stage condenser 42 and a first permeate recovery tank 7. The first permeate recovery tank 7 is used to recover water from propylene glycol methyl ether.

[0073] The dense pervaporation methanol membrane module 5 includes a second inlet 50 and a second permeate outlet 540. The second inlet 50 is connected to the first permeate outlet 430 of the dense pervaporation water membrane module 4. The second permeate outlet 540 is sequentially connected to a second-stage condenser 62 and a second permeate recovery tank 8. The second permeate recovery tank 8 can recover methanol from propylene glycol methyl ether to avoid environmental hazards.

[0074] The dense pervaporation membrane module 6 includes a third inlet 60, a third permeate-side outlet 630, and a third permeate-side outlet 640. The third inlet 60 is connected to the second permeate-side outlet 530 of the dense pervaporation methanol permeation membrane module 5. The third permeate-side outlet 640 is sequentially connected to a third-stage condenser 62 and a third permeate recovery tank 9. The third permeate recovery tank 9 facilitates the recovery of 2-methoxy-1-propanol from propylene glycol methyl ether. The third permeate-side outlet 630 is connected to a storage tank 10 for storing the obtained high-purity propylene glycol methyl ether solution.

[0075] The apparatus for preparing high-purity propylene glycol methyl ether also includes a vacuum pump 11. The first-stage condenser 42, the second-stage condenser 52, and the third-stage condenser 62 are all connected to the vacuum pump 11. In this embodiment, the first-stage condenser 42, the second-stage condenser 52, and the third-stage condenser 62 all share a vacuum system for power, which can effectively reduce equipment investment and reduce costs.

[0076] In this embodiment, only one heater is installed between the dense pervaporation water-permeable membrane group 4 and the raw material tank 1. The dense pervaporation water-permeable membrane group 4, the dense pervaporation methanol-permeable membrane group 5, and the dense pervaporation membrane group 6 share only one heating system, which effectively reduces equipment investment and costs.

[0077] In this invention, the dense pervaporation methanol permeation membrane in the dense pervaporation methanol permeation membrane assembly 5 has a three-layer structure. The first and second layers of the dense pervaporation methanol permeation membrane are both asymmetric tubular inorganic membranes, and the third layer is an effective separation layer.

[0078] Furthermore, the first layer of the dense pervaporation methanol membrane is selected from one of alumina, corundum, and mullite.

[0079] Furthermore, the second layer of the dense pervaporation methanol membrane is selected from one of alumina, titanium dioxide, and zirconium oxide.

[0080] Furthermore, the third layer of the dense pervaporation methanol membrane is a polycarbosilane composite membrane modified with polyacrylic acid.

[0081] Furthermore, the average pore size of the first layer of the dense pervaporation methanol membrane is 500–1000 nm, the average pore size of the second layer is 2–100 nm, and the thickness of the third layer is 5–20 μm.

[0082] In this invention, the dense pervaporation membrane in the dense pervaporation membrane assembly 6 has a three-layer structure. The first and second layers of the dense pervaporation membrane are both asymmetric tubular inorganic membranes, and the third layer is an effective separation layer.

[0083] Furthermore, the first layer of the dense pervaporation membrane is selected from one of alumina, corundum, and mullite.

[0084] Furthermore, the second layer of the dense pervaporation membrane is selected from one of alumina, titanium dioxide, and zirconium oxide.

[0085] Furthermore, the third layer of the dense pervaporation membrane is a dense membrane composed of UiO-66-doped PDMS.

[0086] Furthermore, the dense pervaporation membrane has an average pore size of 500–1000 nm for the first layer, an average pore size of 2–100 nm for the second layer, and a thickness of 5–20 μm for the third layer.

[0087] The thickness of the dense pervaporation permeable membrane in the dense pervaporation permeable membrane group 4 is 5-20 μm. The dense pervaporation permeable membrane is selected from one or more of molecular sieve membranes, chitosan membranes, silica membranes, PVA membranes, and modified membranes.

[0088] Furthermore, dense pervaporation permeable membranes can also be selected from molecular sieve membranes, chitosan membranes, silica membranes, and PVA membranes by doping or modifying nanoparticles.

[0089] Furthermore, the heater's heating temperature is 50–100°C.

[0090] The dense pervaporation water-permeable membrane group 4 for dehydration, the dense pervaporation methanol-permeable membrane group 5 for methanol removal, and the dense pervaporation membrane group 6 for 2-methoxy-1-propanol removal share a single pervaporation system. By combining different functional membranes, the dual objectives of water removal and organic impurity removal are achieved simultaneously. The heating system and vacuum system are shared, which can effectively reduce equipment investment and lower costs.

[0091] The present invention also provides a method for preparing the above-mentioned high-purity propylene glycol methyl ether, the method comprising the following steps:

[0092] Step S1: The crude propylene glycol methyl ether solution is fed into raw material tank 1 and then heated by heater 3 for later use;

[0093] First-stage membrane dehydration: The crude propylene glycol methyl ether solution obtained after heating in step S1 is fed into a dense pervaporation water-permeable membrane assembly for pervaporation. Water selectively permeates through the dense pervaporation water-permeable membrane to become permeate vapor and is enriched on the first permeate side. The first permeate side is evacuated at 1000-8000 Pa. The permeate vapor on the first permeate side is condensed at a temperature of -15 to 0°C by the first-stage condenser to form the first permeate liquid. The first permeate liquid is 90%-98% water. The first residual liquid is obtained on the first residual side of the dense pervaporation water-permeable membrane. The first residual liquid is a propylene glycol methyl ether solution containing methanol and 2-methoxy-1-propanol.

[0094] Methanol removal via secondary membrane: The first permeate obtained in step S2 is transported to a dense pervaporation methanol membrane assembly for pervaporation. Methanol selectively permeates through the dense pervaporation methanol membrane, becoming permeate vapor and accumulating on the second permeate side. The second permeate side is evacuated at 1000–8000 Pa. The permeate vapor on the second permeate side is condensed at a temperature of -15–0°C by the second-stage condenser to form the second permeate. The first permeate is 90%–98% methanol. The second permeate is obtained from the second permeate side of the dense pervaporation methanol membrane. The second permeate is a propylene glycol methyl ether solution containing 2-methoxy-1-propanol.

[0095] Step S4: Three-stage membrane removal of 2-methoxy-1-propanol: The second permeate obtained in step S3 is transported to a dense pervaporation membrane assembly for pervaporation. 2-methoxy-1-propanol selectively permeates through the dense pervaporation membrane, becoming permeate vapor and accumulating on the third permeate side. The third permeate side is evacuated at 1000–8000 Pa. The permeate vapor on the third permeate side is condensed at a temperature of -15–0°C by the third-stage condenser to form the third permeate. 90%–98% of the first permeate is 2-methoxy-1-propanol. The third permeate is obtained on the third permeate side of the dense pervaporation membrane. The third permeate is a high-purity propylene glycol methyl ether solution.

[0096] The dense pervaporation methanol membrane in step S3 is prepared using the following method:

[0097] Step (1) Pre-plugging the hole: Soak the tubular inorganic membrane in water for 30-60 minutes. After soaking, blow the tubular inorganic membrane with air at 0.1-0.2 MPa for 5-20 minutes for later use.

[0098] Step (2) Preparation of transition layer: Immerse the pre-plugged tubular inorganic membrane in water glass solution, and dip and coat the outer surface of the membrane at a lifting speed of 0.05-0.2 m / s for 5-60 s, and then dry it at 30-50℃ for 2-4 h;

[0099] Step (3) Coating: Dissolve polycarbosilane powder with a molecular weight of 4000 in p-xylene to prepare a coating solution with a concentration of 1-10%. Then, dip the coating solution onto the surface of the membrane obtained in step (2) at a lifting speed of 0.05-0.2 m / s for 5-60 seconds to obtain the composite membrane precursor.

[0100] Step (4) Curing: The composite film precursor from step (3) is cured under an air flow of 150-300°C for 2-5 hours, and then heated at 750°C for 0.5 hours under N2 atmosphere, with a heating rate of about 20-50°C / min.

[0101] Step (5) Modification: Dissolve polyacrylic acid powder in hot water at 85-95℃ to prepare a polyacrylic acid solution with a concentration of 1-3%. Then add 1-3% tetraethyl orthosilicate by mass of polyacrylic acid, stir for 2-6 hours, and then dip and coat the membrane from step 4 at a lifting speed of 0.05-0.2m / s for 5-60 seconds. Finally, dry at 100-150℃ for 2-4 hours to obtain a dense pervaporated methanol membrane.

[0102] The dense pervaporation membrane in step S4 is prepared using the following method:

[0103] Step (1) Pre-plugging the hole: Soak the tubular inorganic membrane in water for 30-60 minutes. After soaking, blow the tubular inorganic membrane with air at 0.1-0.2 MPa for 5-20 minutes for later use.

[0104] Step (2) Preparation of transition layer: Immerse the pre-plugged tubular inorganic membrane in water glass solution, and dip and coat the outer surface of the membrane at a lifting speed of 0.05-0.2 m / s for 5-60 s, and then dry it at 30-50℃ for 2-4 h;

[0105] Step (3) MOFs (UiO-66) preparation: Dissolve ZrCl4 in half of the DMF, then add acetic acid solution, sonicate for 10 min, then dissolve terephthalic acid in the remaining half of the DMF, then pour the terephthalic acid solution into the ZrCl4 solution, add water and stir at room temperature for 30 min. After stirring, transfer the resulting solution to a stainless steel autoclave lined with PTFE, place it in a convection oven at 120℃ for 72 h for synthesis. After synthesis, centrifuge the suspension, wash it with ethanol 3 to 5 times, and vacuum dry it at 25 to 50℃ and 10 to 30 kPa for 2 to 6 h.

[0106] In step (3), the molar ratio of ZrCl4: terephthalic acid: water: acetic acid: DMF is 1:1:1:150:500.

[0107] Step (4) Preparation of coating solution: Take a certain mass of hydroxyl-terminated polydimethylsiloxane (PDMS) prepolymer and mix it with 3 to 10 times the weight of PDMS in n-heptane. Stir for 15 min to fully dissolve PDMS. Then add 3 to 20% of the weight of PDMS in tetraethyl orthosilicate (TEOS) crosslinking agent and stir for 10 to 20 min. Finally, add 0.01 to 5% of the weight of PDMS in dibutyltin dilaurate catalyst and stir for 10 to 20 min for pre-crosslinking to obtain a polymer solution. Then add 1 to 5 wt% of MOF to the polymer solution and sonicate continuously at 80℃ for 1 to 4 h until the MOF particles are completely dispersed to obtain the coating solution.

[0108] Step (5) Coating: The coating liquid obtained in step (4) is dipped into the base film obtained in step 2 at a lifting speed of 0.05 to 0.2 m / s for 5 to 60 seconds, evaporated at room temperature for 4 hours, and finally dried at 80 to 100°C for 2 to 4 hours to obtain a dense pervaporation membrane.

[0109] This invention employs a composite membrane of polyacrylic acid modified with polysilane, which exhibits preferential selectivity for methanol. By controlling the crosslinking temperature, the polysilane composite membrane can be configured with different pore sizes. The resulting microstructure exhibits preferential selectivity for methanol, resulting in a faster permeation rate and higher flux compared to other components, thereby achieving the purpose of methanol removal.

[0110] This invention employs a separation membrane doped with UiO-66 and PDMS. UiO-66 has a regular inorganic structure with a pore size of 0.6 nm, good stability, and preferential selectivity for 2-methoxy-1-propanol. Through preferential adsorption and pore size sieving effect, 2-methoxy-1-propanol and propylene glycol methyl ether are separated.

[0111] UiO-66, also known as MOFs, is a metal-organic framework material. As a relatively new type of porous material, it has the characteristics of customizable and diverse structures, and possesses the common properties of organic polymers and inorganic compounds.

[0112] The secondary membrane for methanol removal and the tertiary membrane for 2-methoxy-1-propanol removal of the present invention use ceramic-based membranes, which have excellent solvent resistance.

[0113] The following specific embodiments are used to further illustrate and describe the concept of the present invention, but it does not mean that the present invention is limited to the specific solutions described below. Any specific value within the range described in the embodiments is feasible.

[0114] Example 1

[0115] Step S1: A crude propylene glycol methyl ether solution containing 0.01 wt% water and 0.01 wt% 2-methoxy-1-propanol is fed into raw material tank 1 at a rate of 1000 kg / h and heated to 60°C under heater 3 for later use.

[0116] Step S2: First-stage membrane dehydration: The heated crude propylene glycol methyl ether solution obtained in step S1 is fed into a dense pervaporation water-permeable membrane formed by a dopamine-modified PVA / PAN composite membrane for pervaporation. Water selectively pervaporates the dense pervaporation water-permeable membrane to become permeate vapor and is enriched on the first permeate side 44. The first permeate side 44 is evacuated at 2000 Pa. The permeate vapor on the first permeate side 44 is condensed through the first-stage condenser 42 to form the first permeate liquid. The first permeate liquid flows into the first permeate recovery tank 7 to remove water from the propylene glycol methyl ether. The first permeate liquid is obtained on the first permeate side 43 of the dense pervaporation water-permeable membrane.

[0117] Step S3:

[0118] Secondary membrane removal of methanol: The first permeate obtained in step S2 is transported to a dense pervaporation methanol permeation membrane formed by a polyacrylic acid-modified polycarbosilane membrane with a thickness of 5 μm and an average pore size of 500 nm, and a tubular inorganic membrane with a zirconium oxide upper layer and an average pore size of 2 nm for pervaporation. Methanol selectively permeates through the dense pervaporation methanol permeation membrane as permeate vapor and is enriched on the second permeation side 54. The second permeation side 54 is evacuated at 2000 Pa. The permeate vapor on the second permeation side 54 is condensed through a second-stage condenser to form a second permeate liquid. The second permeate liquid flows into the second permeate recovery tank 8. The second permeate liquid is obtained from the second permeate side 53 of the dense pervaporation methanol permeation membrane.

[0119] The preparation of a dense pervaporation methanol membrane is as follows:

[0120] Step (1) Pre-plugging the hole: Soak the tubular inorganic membrane in water for 30 minutes. After soaking, blow the tubular inorganic membrane with air at 0.1-0.2 MPa for 5 minutes for later use.

[0121] Step (2) Preparation of transition layer: The tubular inorganic membrane after pre-plugging is immersed in water glass solution, and the outer surface of the membrane is dipped and coated for 20s at a lifting speed of 0.05m / s, and then dried at 30℃ for 2h.

[0122] Step (3) Coating: Dissolve polycarbosilane powder with a molecular weight of 4000 in p-xylene to prepare a coating solution with a concentration of 1%. Then, dip the coating solution onto the surface of the membrane obtained in step (2) at a lifting speed of 0.05 m / s and dip for 20 seconds to obtain the composite membrane precursor.

[0123] Step (4) Curing: The composite film precursor from step (3) is cured under an air stream at 150°C for 2 hours, and then heated at 750°C for 0.5 hours under a N2 atmosphere at a heating rate of about 20°C / min.

[0124] Step (5) Modification: Dissolve polyacrylic acid powder in hot water at 85°C to prepare a 1% polyacrylic acid solution, then add 1% tetraethyl orthosilicate by mass of polyacrylic acid, stir for 2 hours, then dip and coat the membrane from step 4 at a lifting speed of 0.05 m / s for 20 seconds, and finally dry at 100°C for 2 hours to obtain a dense pervaporated methanol membrane.

[0125] Step S4:

[0126] Three-stage membrane removal of 2-methoxy-1-propanol: The second permeate obtained in step S3 is transported to a dense pervaporation membrane formed by a UiO-66-doped PDMS membrane with a thickness of 5 μm and an average pore size of 500 nm, and a tubular inorganic membrane with an upper layer of zirconium oxide and an average pore size of 2 nm for pervaporation. 2-methoxy-1-propanol selectively permeates through the dense pervaporation membrane as permeate vapor and is enriched on the third permeate side 64. The third permeate side 64 is evacuated at 2000 Pa. The permeate vapor on the third permeate side 64 is condensed through a third-stage condenser to form the third permeate liquid. The third permeate liquid flows into the third permeate recovery tank 9. A high-purity propylene glycol methyl ether solution is obtained from the third permeate side 63 of the dense pervaporation membrane. The propylene glycol methyl ether solution flows into the storage tank 10.

[0127] The product flow rate of the third permeate side outlet 630 of the dense pervaporation membrane module 6 is 900 kg / h, the water in the propylene glycol methyl ether of the product is removed to 20 ppm, and the purity of the propylene glycol methyl ether reaches 99.99%.

[0128] Preparation of dense pervaporation membrane:

[0129] Step (1) Pre-plugging the hole: Soak the tubular inorganic membrane in water for 30 minutes. After soaking, blow the tubular inorganic membrane with air at 0.1-0.2 MPa for 5 minutes for later use.

[0130] Step (2) Preparation of transition layer: The tubular inorganic membrane after pre-plugging is immersed in water glass solution, and the outer surface of the membrane is dipped and coated for 20s at a lifting speed of 0.05m / s, and then dried at 30℃ for 2h.

[0131] Step (3) Preparation of MOFs (UiO-66): Dissolve 1 mol of ZrCl4 in 250 mol of DMF, then add 150 mol of acetic acid solution, sonicate for 10 min, then dissolve 1 mol of terephthalic acid in the remaining 250 mol of DMF, then pour the terephthalic acid solution into the ZrCl4 solution, add 1 mol of water and stir at room temperature for 30 min. After stirring, transfer the resulting solution to a stainless steel autoclave lined with PTFE and place it in a convection oven at 120 °C for 72 h for synthesis. After synthesis, centrifuge the suspension, wash it three times with ethanol, and then vacuum dry it at 25 °C and 10-30 kPa for 2 h.

[0132] Step (4) Preparation of coating solution: Take a certain mass of hydroxyl-terminated polydimethylsiloxane (PDMS) prepolymer and mix it with 3 times the weight of PDMS in n-heptane. Stir for 15 min to fully dissolve PDMS. Then add 3% of the weight of PDMS in tetraethyl orthosilicate (TEOS) crosslinking agent and stir for 10 min. Finally, add 0.01% of the weight of PDMS in dibutyltin dilaurate catalyst and stir for 10-20 min for pre-crosslinking to obtain a polymer solution. Then add 1 wt% of MOFs to the polymer solution and sonicate continuously at 80℃ for 1 h until the MOFs particles are completely dispersed to obtain the coating solution.

[0133] Step (5) Coating: The coating liquid obtained in step (4) is immersed in the base film obtained in step 2 at a lifting speed of 0.05 m / s for 20 s, evaporated at room temperature for 4 h, and finally dried at 80 ℃ for 2 h to obtain a dense pervaporation membrane.

[0134] Example 2

[0135] Step S1: A crude propylene glycol methyl ether solution containing 30 wt% water and 20 wt% 2-methoxy-1-propanol is fed into raw material tank 1 at a rate of 1000 kg / h and heated to 100°C under heater 3 for later use.

[0136] Step S2: Primary membrane dehydration: The heated crude propylene glycol methyl ether solution obtained in step S1 is fed into a dense pervaporation water-permeable membrane formed by NaA molecular sieve / mullite inorganic composite membrane for pervaporation. Water selectively permeates through the dense pervaporation water-permeable membrane to become permeate vapor and is enriched on the first permeate side 44. The first permeate side 44 is evacuated at 8000 Pa. The permeate vapor on the first permeate side 44 is condensed through the first-stage condenser 42 to form the first permeate liquid. The first permeate liquid flows into the first permeate recovery tank 7 to remove water from the propylene glycol methyl ether. The first permeate liquid is obtained on the first permeate side 43 of the dense pervaporation water-permeable membrane.

[0137] Step S3:

[0138] Secondary membrane removal of methanol: The first permeate obtained in step S2 is transported to a dense pervaporation methanol permeation membrane formed by a support of corundum with a thickness of 20 μm and an average pore size of 1000 nm, which is a polyacrylic acid-modified polycarbosilane membrane, and a tubular inorganic membrane with an average pore size of 100 nm and an upper layer of zirconium oxide. Methanol selectively permeates through the dense pervaporation methanol permeation membrane as permeate vapor and is enriched on the second permeation side 54. The second permeation side 54 is evacuated at 8000 Pa. The permeate vapor on the second permeation side 54 is condensed through a second-stage condenser to form a second permeate liquid. The second permeate liquid flows into the second permeate recovery tank 8. The second permeate liquid is obtained from the second permeate side 53 of the dense pervaporation methanol permeation membrane.

[0139] Preparation of dense pervaporation methanol membrane:

[0140] Step (1) Pre-plugging the hole: Soak the tubular inorganic membrane in water for 45 minutes. After soaking, blow the tubular inorganic membrane with air at 0.1-0.2 MPa for 15 minutes for later use.

[0141] Step (2) Preparation of transition layer: The tubular inorganic membrane after pre-plugging is immersed in water glass solution, and the outer surface of the membrane is dipped and coated for 40s at a lifting speed of 0.1m / s, and then dried at 40℃ for 3h.

[0142] Step (3) Coating: Dissolve polycarbosilane powder with a molecular weight of 4000 in p-xylene to prepare a coating solution with a concentration of 5%. Then, dip the coating solution onto the surface of the membrane obtained in step (2) at a lifting speed of 0.1 m / s and dip for 40 s to obtain the composite membrane precursor.

[0143] Step (4) Curing: The composite film precursor from step (3) is cured under an air stream at 210°C for 4 hours, and then heated at 750°C for 0.5 hours under a N2 atmosphere at a heating rate of about 35°C / min.

[0144] Step (5) Modification: Dissolve polyacrylic acid powder in hot water at 90°C to prepare a polyacrylic acid solution with a concentration of 2%, then add 2% tetraethyl orthosilicate by mass of polyacrylic acid, stir for 4 hours, then dip and coat the membrane in step 4 at a lifting speed of 0.1 m / s for 40 seconds, and finally dry at 120°C for 3 hours to obtain a dense pervaporated methanol membrane.

[0145] Step S3: Three-stage membrane removal of 2-methoxy-1-propanol: The second permeate obtained in step S3 is transported to a dense pervaporation membrane formed by a corundum support with a UiO-66-doped PDMS membrane and a thickness of 20 μm and an average pore size of 1000 nm, and a tubular inorganic membrane with a zirconium oxide upper layer and an average pore size of 100 nm for pervaporation. 2-methoxy-1-propanol selectively permeates through the dense pervaporation membrane as permeate vapor and is enriched on the third permeate side 64. The third permeate side 64 is evacuated at 8000 Pa. The permeate vapor on the third permeate side 64 is condensed through a third-stage condenser to form the third permeate liquid. The third permeate liquid flows into the third permeate recovery tank 9. A high-purity propylene glycol methyl ether solution is obtained from the third permeate side 63 of the dense pervaporation membrane. The propylene glycol methyl ether solution flows into the storage tank 10.

[0146] Preparation of dense pervaporation membrane:

[0147] Step (1) Pre-plugging the hole: Soak the tubular inorganic membrane in water for 40 minutes. After soaking, blow the tubular inorganic membrane with air at 0.1-0.2 MPa for 15 minutes for later use.

[0148] Step (2) Preparation of transition layer: The tubular inorganic membrane after pre-plugging is immersed in water glass solution, and the outer surface of the membrane is dipped and coated for 40s at a lifting speed of 0.1m / s, and then dried at 40℃ for 3h.

[0149] Step (3) Preparation of MOFs (UiO-66): Dissolve 2 mol of ZrCl4 in 500 mol of DMF, then add 300 mol of acetic acid solution, sonicate for 10 min, then dissolve 2 mol of terephthalic acid in the remaining 500 mol of DMF, then pour the terephthalic acid solution into the ZrCl4 solution, add 2 mol of water and stir at room temperature for 30 min. After stirring, transfer the resulting solution to a stainless steel autoclave lined with PTFE and place it in a convection oven at 120℃ for 72 h for synthesis. After synthesis, centrifuge the suspension, wash it 4 times with ethanol, and then vacuum dry it at 40℃ and 10-30 kPa for 4 h.

[0150] Step (4) Preparation of coating solution: Take a certain mass of hydroxyl-terminated polydimethylsiloxane (PDMS) prepolymer and mix it with 7 times the weight of PDMS in n-heptane. Stir for 15 min to fully dissolve PDMS. Then add 10% of the weight of PDMS in tetraethyl orthosilicate (TEOS) crosslinking agent and stir for 15 min. Finally, add 3% of the weight of PDMS in dibutyltin dilaurate catalyst and stir for 15 min for pre-crosslinking to obtain polymer solution. Then add 4 wt% of MOFs to polymer solution and sonicate continuously at 80℃ for 3 h until MOFs particles are completely dispersed to obtain coating solution.

[0151] Step (5) Coating: The coating liquid obtained in step (4) is immersed in the base film obtained in step 2 at a lifting speed of 0.1 m / s for 40 s, evaporated at room temperature for 4 h, and finally dried at 90 ℃ for 3 h to obtain a dense pervaporation membrane.

[0152] The product flow rate of the third permeate side outlet 630 of the dense pervaporation membrane module 6 is 400 kg / h, the water in the propylene glycol methyl ether of the product is removed to 10 ppm, and the purity of the propylene glycol methyl ether reaches 99.999%.

[0153] Example 3

[0154] Step S1: A crude propylene glycol methyl ether solution containing 5 wt% water and 5 wt% 2-methoxy-1-propanol is fed into raw material tank 1 at a rate of 1000 kg / h and heated to 80°C under heater 3 for later use.

[0155] Step S2: Primary membrane dehydration: The heated crude propylene glycol methyl ether solution obtained in step S1 is fed into a dense pervaporation water-permeable membrane formed by NaA molecular sieve / mullite inorganic composite membrane for pervaporation. Water selectively permeates through the dense pervaporation water-permeable membrane to become permeate vapor and is enriched on the first permeate side 44. The first permeate side 44 is evacuated at 5000 Pa. The permeate vapor on the first permeate side 44 is condensed through the first-stage condenser 42 to form the first permeate liquid. The first permeate liquid flows into the first permeate recovery tank 7 to remove water from the propylene glycol methyl ether. The first permeate liquid is obtained on the first permeate side 43 of the dense pervaporation water-permeable membrane.

[0156] Step S3: Secondary membrane removal of methanol: The first permeate obtained in step S2 is transported to a dense pervaporation methanol permeation membrane formed by a polyacrylic acid-modified polycarbonylsilane membrane with a thickness of 10 μm and an average pore size of 800 nm, and a tubular inorganic membrane with a zirconium oxide upper layer and an average pore size of 50 nm for pervaporation. Methanol selectively permeates through the dense pervaporation methanol permeation membrane as permeate vapor and is enriched on the second permeation side 54. The second permeation side 54 is evacuated at 5000 Pa. The permeate vapor on the second permeation side 54 is condensed through a second-stage condenser to form a second permeate liquid. The second permeate liquid flows into the second permeate recovery tank 8. The second permeate liquid is obtained from the second permeate side 53 of the dense pervaporation methanol permeation membrane.

[0157] Preparation of dense pervaporation methanol membrane:

[0158] Step (1) Pre-plugging the hole: Soak the tubular inorganic membrane in water for 60 minutes. After soaking, blow the tubular inorganic membrane with air at 0.1-0.2 MPa for 20 minutes for later use.

[0159] Step (2) Preparation of transition layer: The tubular inorganic membrane after pre-plugging is immersed in water glass solution, and the outer surface of the membrane is dipped and coated at a lifting speed of 0.2 m / s for 60 s, and then dried at 50℃ for 4 h;

[0160] Step (3) Coating: Dissolve polycarbosilane powder with a molecular weight of 4000 in p-xylene to prepare a coating solution with a concentration of 10%. Then, dip the coating solution onto the surface of the membrane obtained in step (2) at a lifting speed of 0.2 m / s and dip for 60 s to obtain the composite membrane precursor.

[0161] Step (4) Curing: The composite film precursor from step (3) is cured under an air flow at 300°C for 5 hours, and then heated at 750°C for 0.5 hours under a N2 atmosphere at a heating rate of about 50°C / min.

[0162] Step (5) Modification: Dissolve polyacrylic acid powder in hot water at 95°C to prepare a 3% polyacrylic acid solution, then add 3% tetraethyl orthosilicate by mass of polyacrylic acid, stir for 6 hours, then dip and coat the membrane from step 4 at a lifting speed of 0.2 m / s for 60 seconds, and finally dry at 150°C for 4 hours to obtain a dense pervaporated methanol membrane.

[0163] Step S4: Three-stage membrane removal of 2-methoxy-1-propanol: The second permeate obtained in step S3 is transported to a dense pervaporation membrane formed by a UiO-66-doped PDMS membrane with a thickness of 10 μm and an average pore size of 800 nm, and a tubular inorganic membrane with an upper layer of zirconium oxide and an average pore size of 50 nm for pervaporation. 2-methoxy-1-propanol selectively permeates through the dense pervaporation membrane as permeate vapor and is enriched on the third permeate side 64. The third permeate side 64 is evacuated at 5000 Pa. The permeate vapor on the third permeate side 64 is condensed through a third-stage condenser to form the third permeate liquid. The third permeate liquid flows into the third permeate recovery tank 9. A high-purity propylene glycol methyl ether solution is obtained from the third permeate side 63 of the dense pervaporation membrane. The propylene glycol methyl ether solution flows into the storage tank 10.

[0164] Preparation of dense pervaporation membrane:

[0165] Step (1) Pre-plugging the hole: Soak the tubular inorganic membrane in water for 60 minutes. After soaking, blow the tubular inorganic membrane with air at 0.1-0.2 MPa for 20 minutes for later use.

[0166] Step (2) Preparation of transition layer: The tubular inorganic membrane after pre-plugging is immersed in water glass solution, and the outer surface of the membrane is dipped and coated at a lifting speed of 0.2 m / s for 60 s, and then dried at 50℃ for 4 h;

[0167] Step (3) Preparation of MOFs (UiO-66): Dissolve 4 mol of ZrCl4 in 1000 mol of DMF, then add 600 mol of acetic acid solution, sonicate for 10 min, then dissolve 4 mol of terephthalic acid in the remaining 1000 mol of DMF, then pour the terephthalic acid solution into the ZrCl4 solution, add 4 mol of water and stir at room temperature for 30 min. After stirring, transfer the resulting solution to a stainless steel autoclave lined with PTFE and place it in a convection oven at 120℃ for 72 h for synthesis. After synthesis, centrifuge the suspension, wash it 5 times with ethanol, and then vacuum dry it at 50℃ and 10-30 kPa for 6 h.

[0168] Step (4) Preparation of coating solution: Take a certain mass of hydroxyl-terminated polydimethylsiloxane (PDMS) prepolymer and mix it with 10 times the weight of PDMS in n-heptane. Stir for 15 min to fully dissolve PDMS. Then add 20% of the weight of PDMS in tetraethyl orthosilicate (TEOS) crosslinking agent and stir for 20 min. Finally, add 5% of the weight of PDMS in dibutyltin dilaurate catalyst and stir for 20 min for pre-crosslinking to obtain polymer solution. Then add 5 wt% of MOFs to polymer solution and sonicate continuously at 80℃ for 4 h until MOFs particles are completely dispersed to obtain coating solution.

[0169] Step (5) Coating: The coating liquid obtained in step (4) is immersed in the base film obtained in step 2 at a lifting speed of 0.2 m / s for 60 s, evaporated at room temperature for 4 h, and finally dried at 100 ℃ for 4 h to obtain a dense pervaporation membrane.

[0170] The product flow rate of the third permeate side outlet 630 of the dense pervaporation membrane module 6 is 850 kg / h, the water in the propylene glycol methyl ether of the product is removed to 5 ppm, and the purity of the propylene glycol methyl ether reaches 99.999%.

[0171] It should be noted that the above preferred embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A device for producing high-purity propylene glycol methyl ether, comprising, in series, a raw material tank (1), a raw material pump (2), and a heater (3), characterized in that The preparation apparatus further includes: A dense pervaporation water-permeable membrane assembly (4) is provided, which can remove water from a crude propylene glycol methyl ether solution and includes a first inlet (40) and a first treble-side outlet (430), wherein the first inlet (40) is connected to the heater (3); A dense pervaporation methanol membrane assembly (5) is provided, which can remove methanol from a crude propylene glycol methyl ether solution and includes a second inlet (50) and a second treasury side outlet (530). The second inlet (50) is connected to the first treasury side outlet (430) of the dense pervaporation water membrane assembly (4). A dense pervaporation membrane assembly (6) is provided, which can remove 2-methoxy-1-propanol from a crude propylene glycol methyl ether solution to obtain high-purity propylene glycol methyl ether and includes a third inlet (60) and a third osmotic side outlet (630). The third inlet (60) is connected to the second osmotic side outlet (530) of the dense pervaporation methanol permeation membrane assembly (5), and the third osmotic side outlet (630) is used to connect to a storage tank (10). The dense pervaporation methanol membrane assembly (5) includes a first layer, a second layer and a third layer, wherein the first and second layers are both asymmetric tubular inorganic membranes and the third layer is an effective separation layer. The first layer of the dense pervaporation methanol membrane is selected from one of alumina, corundum, and mullite. The second layer of the dense pervaporation methanol membrane is selected from one of alumina, titanium dioxide, and zirconium oxide. The third layer of the dense pervaporation methanol membrane is a polycarbosilane composite membrane modified with polyacrylic acid. The structure of the dense pervaporation membrane in the dense pervaporation membrane group (6) includes a first layer, a second layer and a third layer. The first and second layers of the dense pervaporation membrane are both asymmetric tubular inorganic membranes, and the third layer is an effective separation layer. The first layer of the dense pervaporation membrane is selected from one of alumina, corundum, and mullite; The second layer of the dense pervaporation membrane is selected from one of alumina, titanium dioxide, and zirconium oxide; The third layer of the dense pervaporation membrane is a dense membrane composed of UiO-66 doped PDMS.

2. The apparatus for preparing high-purity propylene glycol methyl ether according to claim 1, characterized in that: The dense pervaporation water-permeable membrane assembly (4) also includes a first permeation side outlet (440), which is connected in sequence to a first-stage condenser (42) and a first permeate recovery tank (7). The first permeate recovery tank (7) is used to recover water from propylene glycol methyl ether. The dense pervaporation methanol membrane module (5) also includes a second permeate-side outlet (540), which is connected in sequence to a second-stage condenser (52) and a second permeate recovery tank (8). The second permeate recovery tank (8) can recover methanol from propylene glycol methyl ether. The dense pervaporation membrane assembly (6) also includes a third permeate outlet (640), which is connected in sequence to a third-stage condenser (62) and a third permeate recovery tank (9). The third permeate recovery tank (9) can recover 2-methoxy-1-propanol from propylene glycol methyl ether.

3. The apparatus for preparing high-purity propylene glycol methyl ether according to claim 1, characterized in that, The apparatus for preparing high-purity propylene glycol methyl ether also includes a vacuum pump (11), and the first-stage condenser (42), the second-stage condenser (52) and the third-stage condenser (62) are all connected to the vacuum pump (11).

4. The apparatus for preparing high-purity propylene glycol methyl ether according to claim 1, characterized in that, The dense pervaporation methanol membrane has an average pore size of 500–1000 nm in the first layer, an average pore size of 2–100 nm in the second layer, and a thickness of 5–20 μm in the third layer.

5. The apparatus for preparing high-purity propylene glycol methyl ether according to claim 1, characterized in that, The dense pervaporation membrane has an average pore size of 500–1000 nm in the first layer, an average pore size of 2–100 nm in the second layer, and a thickness of 5–20 μm in the third layer.

6. The apparatus for preparing high-purity propylene glycol methyl ether according to claim 1, characterized in that, The thickness of the dense pervaporation permeable membrane in the dense pervaporation permeable membrane group (4) is 5-20 μm, and the dense pervaporation permeable membrane is selected from one or more of molecular sieve membrane, chitosan membrane, silica membrane, and PVA membrane.

7. A method for preparing the apparatus for preparing high-purity propylene glycol methyl ether as described in any one of claims 1-6, characterized in that, The preparation method includes the following steps: Step S1: The crude propylene glycol methyl ether solution is fed into the raw material tank (1) and then heated by the heater (3) at a temperature of 50-100℃ for later use; Step S2: Primary membrane dehydration: The crude propylene glycol methyl ether solution obtained after heating in step S1 is fed into a dense pervaporation permeable membrane group (4) for pervaporation to remove water from the crude propylene glycol methyl ether solution, resulting in a first osmotic solution and a first permeate. The first permeate is 90% to 98% water, and the first osmotic solution is a propylene glycol methyl ether solution containing methanol and 2-methoxy-1-propanol. Step S3: Secondary membrane removal of methanol: The first permeate obtained in step S2 is transported to a dense pervaporation methanol permeate membrane group (5) for pervaporation to remove methanol from the first permeate, resulting in a second permeate and a second permeate. The second permeate is 90% to 98% methanol and is a propylene glycol methyl ether solution containing 2-methoxy-1-propanol. Step S4: Three-stage membrane removal of 2-methoxy-1-propanol: The second permeate obtained in step S3 is transported to a dense pervaporation membrane assembly (6) for pervaporation so that 2-methoxy-1-propanol in the second permeate can be removed, resulting in a third permeate and a third permeate. The third permeate is 90% to 98% 2-methoxy-1-propanol, and the third permeate is a high-purity propylene glycol methyl ether solution.

8. The method for preparing high-purity propylene glycol methyl ether according to claim 7, characterized in that, Steps S2 to S4 specifically also include: First-stage membrane dehydration: The crude propylene glycol methyl ether solution obtained after heating in step S1 is fed into a dense pervaporation water-permeable membrane group (4) for pervaporation. Water selectively permeates through the dense pervaporation water-permeable membrane to become permeate vapor and is enriched on the first permeate side (44). The first permeate side (44) is evacuated at 1000~8000Pa. The permeate vapor on the first permeate side (44) is condensed at a temperature of -15~0℃ by the first-stage condenser (42) to form the first permeate liquid. The first permeate liquid is obtained on the first permeate side (43) of the dense pervaporation water-permeable membrane. The first permeate liquid is a propylene glycol methyl ether solution containing methanol and 2-methoxy-1-propanol. Methanol removal by secondary membrane: The first permeate obtained in step S2 is transported to the dense pervaporation methanol membrane group (5) for pervaporation. Methanol selectively permeates through the dense pervaporation methanol membrane to become permeate vapor and is enriched on the second permeate side (54). The second permeate side (54) is evacuated at 1000~8000Pa. The permeate vapor on the second permeate side (54) is condensed at a temperature of -15~0℃ by the second stage condenser (52) to form the second permeate. The second permeate is obtained on the second permeate side (53) of the dense pervaporation methanol membrane. The second permeate is a propylene glycol methyl ether solution containing 2-methoxy-1-propanol. Step S4: Three-stage membrane removal of 2-methoxy-1-propanol: The second permeate obtained in step S3 is transported to the dense pervaporation membrane group (6) for pervaporation. 2-methoxy-1-propanol selectively permeates through the dense pervaporation membrane to become permeate vapor and is enriched on the third permeate side (64). The third permeate side (64) is evacuated at 1000~8000Pa. The permeate vapor on the third permeate side (64) is condensed at a condensation temperature of -15~0℃ by the third-stage condenser (62) to form the third permeate. The third permeate is obtained on the third permeate side (63) of the dense pervaporation membrane. The third permeate is a high-purity propylene glycol methyl ether solution.

9. The method for preparing high-purity propylene glycol methyl ether according to claim 8, characterized in that: The dense pervaporation methanol membrane in step S3 is prepared using the following method: Step (1) Pre-plugging the hole: Soak the tubular inorganic membrane in water for 30-60 minutes. After soaking, blow the tubular inorganic membrane for later use. Step (2) Preparation of transition layer: Immerse the pre-plugged tubular inorganic membrane in water glass solution, dip and coat the outer surface of the membrane for 5-60 seconds, and then dry; Step (3) Coating: Dissolve polycarbosilane powder with a molecular weight of 4000 in p-xylene to prepare a coating solution with a concentration of 1-10%, and then dip the coating solution onto the surface of the membrane obtained in step (2) to obtain the composite membrane precursor. Step (4) Curing: The composite film precursor from step (3) is first cured under an air flow of 150-300°C for 2-5 hours, and then heated at 750°C for 0.5 hours under a N2 atmosphere; Step (5) Modification: Dissolve polyacrylic acid powder in hot water at 85-95℃ to prepare a polyacrylic acid solution with a concentration of 1-3%, then add 1-3% tetraethyl orthosilicate by mass of polyacrylic acid, stir, and then dip-coat the membrane obtained in step 4, and dry to obtain a dense pervaporated methanol membrane. The dense pervaporation membrane in step S4 is prepared using the following method: Step (1): Pre-plugging the hole: Soak the tubular inorganic membrane in water for 30-60 minutes. After soaking, blow the tubular inorganic membrane for later use. Step (2) Preparation of transition layer: Immerse the pre-plugged tubular inorganic membrane in water glass solution, dip and coat the outer surface of the membrane for 5-60 seconds, and then dry; Step (3) MOF preparation: Dissolve ZrCl4 in half of the DMF, then add acetic acid solution, sonicate for 10 min, then dissolve terephthalic acid in the remaining half of the DMF, then pour the terephthalic acid solution into the ZrCl4 solution, add water and stir at room temperature for 30 min. After stirring, transfer the resulting solution to a stainless steel autoclave lined with PTFE, place it in a convection oven at 120°C for 72 h for synthesis. After synthesis, centrifuge the suspension, wash with ethanol, and then vacuum dry. Step (4) Preparation of coating solution: Take a certain mass of hydroxyl-terminated polydimethylsiloxane prepolymer and mix it with 3 to 10 times the weight of polydimethylsiloxane in n-heptane. Stir for 15 minutes to fully dissolve the polydimethylsiloxane. Then add 3 to 20% of the weight of polydimethylsiloxane in tetraethyl orthosilicate as a crosslinking agent and stir. Finally, add 0.01 to 5% of the weight of polydimethylsiloxane in dibutyltin dilaurate as a catalyst and stir to perform pre-crosslinking to obtain a polymer solution. Then add 1 to 5 wt% of MOFs to the polymer solution and sonicate continuously for 1 to 4 hours until the MOFs particles are completely dispersed to obtain the coating solution. Step (5) Coating: The coating liquid obtained in step (4) is immersed in the base film obtained in step 2, evaporated at room temperature, and finally dried to obtain a dense pervaporation membrane.

10. The method for preparing high-purity propylene glycol methyl ether according to claim 9, characterized in that: The preparation of the dense pervaporation methanol membrane in step S3 includes: Step (1) The tubular inorganic membrane is air-washed at 0.1-0.2 MPa for 5-20 minutes and then set aside. Step (2): Dipping speed 0.05-0.2 m / s, drying temperature 30-50℃, drying time 2-4 h; Step (3) Dipping speed: 0.05-0.2 m / s, dipping time: 5-60 s; Step (4) Heating rate: 20–50 °C / min; Step (5): Stirring time 2-6h, dipping speed 0.05-0.2m / s, dipping time 5-60s, drying temperature 100-150℃, drying time 2-4h; The preparation of the dense pervaporation membrane in step S4 also includes: Step (1) The tubular inorganic membrane is air-washed at 0.1-0.2 MPa for 5-20 minutes and then set aside. Step (2): Dipping speed 0.05-0.2 m / s, drying temperature 30-50℃, drying time 2-4 h; Step (3): Wash with ethanol 3-5 times, vacuum degree 10-30 kPa, drying temperature 25-50℃, drying time 2-6 h. In step (3), the molar ratio of ZrCl4: terephthalic acid: water: acetic acid: DMF is 1:1:1:150:500; Step (4) After adding tetraethyl orthosilicate, the stirring time is 10-20 min; after adding dibutyltin dilaurate, the stirring time is 10-20 min; and the ultrasonic temperature is 80℃. Step (5): Dipping speed 0.05-0.2 m / s, dipping time 5-60 s, drying temperature 80-100 ℃, drying time 2-4 h.

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